Test drilling in basalts, Lalamilo area, South Kohala District, Hawaii

USGS Publications Warehouse

Teasdale, Warren E.

1980-01-01

Test drilling has determined that a downhole-percussion airhammer can be used effectively to drill basalts in Hawaii. When used in conjunction with a foam-type drilling fluid, the hammer-bit penetration rate was rapid. Continuous drill cuttings from the materials penetrated were obtained throughout the borehole except from extremely fractured or weathered basalt zones where circulation was lost or limited. Cementing of these zones as soon as encountered reduced problems of stuck tools, washouts, and loss of drill-cuttings. Supplies and logistics on the Hawaiian Islands, always a major concern, require that all anticipated drilling supplies, spare rig and tool parts, drilling muds and additives, foam, and miscellaneous hardware be on hand before starting to drill. If not, the resulting rig downtime is costly in both time and money. (USGS)

Tensile behavior of cenosphere/epoxy syntactic foams

NASA Astrophysics Data System (ADS)

Shahapurkar, Kiran; Doddamani, Mrityunjay; Kumar, G. C. Mohan

2018-04-01

Tensile behavior of syntactic foam composites are very critical to the engineering applications. The fracture modes and failure mechanisms under tension must be fully understood in order to realize the potential of such composites. In the present work, syntactic foam composites are fabricated using as received and surface modified hollow cenospheres embedded into epoxy matrix. Combinations of cenosphere volume fraction (0, 20, 40 and 60%) and surface modification are studied. Experimental results reveal that modulus of both untreated and treated syntactic foams increases with increase in cenosphere volume fraction compared to neat resin. Strength values of syntactic foams show decreasing trend compared to neat resin. However, treated syntactic foams demonstrated better results compared to untreated ones attributing to good bonding between matrix and filler. Scanning electron microscopy reveal brittle fracture for all the syntactic foams.

Foam vessel for cryogenic fluid storage

DOEpatents

Spear, Jonathan D [San Francisco, CA

2011-07-05

Cryogenic storage and separator vessels made of polyolefin foams are disclosed, as are methods of storing and separating cryogenic fluids and fluid mixtures using these vessels. In one embodiment, the polyolefin foams may be cross-linked, closed-cell polyethylene foams with a density of from about 2 pounds per cubic foot to a density of about 4 pounds per cubic foot.

Graphene Foam: Uniaxial Tension Behavior and Fracture Mode Based on a Mesoscopic Model.

PubMed

Pan, Douxing; Wang, Chao; Wang, Tzu-Chiang; Yao, Yugui

2017-09-26

Because of the combined advantages of both porous materials and two-dimensional (2D) graphene sheets, superior mechanical properties of three-dimensional (3D) graphene foams have received much attention from material scientists and energy engineers. Here, a 2D mesoscopic graphene model (Modell. Simul. Mater. Sci. Eng. 2011, 19, 054003), was expanded into a 3D bonded graphene foam system by utilizing physical cross-links and van der Waals forces acting among different mesoscopic graphene flakes by considering the debonding behavior, to evaluate the uniaxial tension behavior and fracture mode based on in situ SEM tensile testing (Carbon 2015, 85, 299). We reasonably reproduced a multipeak stress-strain relationship including its obvious yielding plateau and a ductile fracture mode near 45° plane from the tensile direction including the corresponding fracture morphology. Then, a power scaling law of tensile elastic modulus with mass density and an anisotropic strain-dependent Poisson's ratio were both deduced. The mesoscopic physical mechanism of tensile deformation was clearly revealed through the local stress state and evolution of mesostructure. The fracture feature of bonded graphene foam and its thermodynamic state were directly navigated to the tearing pattern of mesoscopic graphene flakes. This study provides an effective way to understand the mesoscopic physical nature of 3D graphene foams, and hence it may contribute to the multiscale computations of micro/meso/macromechanical performances and optimal design of advanced graphene-foam-based materials.

Cryogenic Temperature-Gradient Foam/Substrate Tensile Tester

NASA Technical Reports Server (NTRS)

Vailhe, Christophe

2003-01-01

The figure shows a fixture for measuring the tensile strength of the bond between an aluminum substrate and a thermally insulating polymeric foam. The specimen is meant to be representative of insulating foam on an aluminum tank that holds a cryogenic liquid. Prior to the development of this fixture, tensile tests of this type were performed on foam/substrate specimens immersed in cryogenic fluids. Because the specimens were cooled to cryogenic temperatures throughout their thicknesses, they tended to become brittle and to fracture at loads below true bond tensile strengths. The present fixture is equipped to provide a thermal gradient from cryogenic temperature at the foam/substrate interface to room temperature on the opposite foam surface. The fixture includes an upper aluminum block at room temperature and a lower aluminum block cooled to -423 F (approx. -253 C) by use of liquid helium. In preparation for a test, the metal outer surface (the lower surface) of a foam/substrate specimen is bonded to the lower block and the foam outer surface (the upper surface) of the specimen is bonded to the upper block. In comparison with the through-the-thickness cooling of immersion testing, the cryogenic-to-room-temperature thermal gradient that exists during testing on this fixture is a more realistic approximation of the operational thermal condition of sprayed insulating foam on a tank of cryogenic liquid. Hence, tensile tests performed on this fixture provide more accurate indications of operational bond tensile strengths. In addition, the introduction of the present fixture reduces the cost of testing by reducing the amount of cryogenic liquid consumed and the time needed to cool a specimen.

Strength and fracture energy of foamed concrete incorporating rice husk ash and polypropylene mega-mesh 55

NASA Astrophysics Data System (ADS)

Jaini, Z. M.; Rum, R. H. M.; Boon, K. H.

2017-10-01

This paper presents the utilization of rice husk ash (RHA) as sand replacement and polypropylene mega-mesh 55 (PMM) as fiber reinforcement in foamed concrete. High pozzolanic reaction and the ability to become filler make RHA as a strategic material to enhance the strength and durability of foamed concrete. Furthermore, the presence of PMM optimizes the toughness of foamed concrete in resisting shrinkage and cracking. In this experimental study, cube and cylinder specimens were prepared for the compression and splitting-tensile tests. Meanwhile, notched beam specimens were cast for the three-point bending test. It was found that 40% RHA and 9kg/m3 PMM contribute to the highest strength and fracture energy. The compressive, tensile and flexural strengths are 32MPa, 2.88MPa and 6.68MPa respectively, while the fracture energy achieves 42.19N/m. The results indicate high potential of RHA and PMM in enhancing the mechanical properties of foamed concrete.

Personal cooling air filtering device

DOEpatents

Klett, James [Knoxville, TN; Conway, Bret [Denver, NC

2002-08-13

A temperature modification system for modifying the temperature of fluids includes at least one thermally conductive carbon foam element, the carbon foam element having at least one flow channel for the passage of fluids. At least one temperature modification device is provided, the temperature modification device thermally connected to the carbon foam element and adapted to modify the temperature of the carbon foam to modify the temperature of fluids flowing through the flow channels. Thermoelectric and/or thermoionic elements can preferably be used as the temperature modification device. A method for the reversible temperature modification of fluids includes the steps of providing a temperature modification system including at least one thermally conductive carbon foam element having flow channels and at least one temperature modification device, and flowing a fluid through the flow channels.

Carbon or graphite foam as a heating element and system thereof

DOEpatents

Ott, Ronald D [Knoxville, TN; McMillan, April D [Knoxville, TN; Choudhury, Ashok [Oak Ridge, TN

2004-05-04

A temperature regulator includes at least one electrically conductive carbon foam element. The foam element includes at least two locations adapted for receiving electrical connectors thereto for heating a fluid, such as engine oil. A combustion engine includes an engine block and at least one carbon foam element, the foam element extending into the engine block or disposed in thermal contact with at least one engine fluid.

Fluid Physics of Foam Evolution and Flow

NASA Technical Reports Server (NTRS)

Aref, H.; Thoroddsen, S. T.; Sullivan, J. M.

2003-01-01

The grant supported theoretical, numerical and experimental work focused on the elucidation of the fluid physics of foam structure, evolution and flow. The experimental work concentrated on these subject areas: (a) Measurements of the speed of reconnections within a foam; (b) statistics of bubble rearrangements; and (c) three-dimensional reconstruction of the foam structure. On the numerical simulation and theory side our efforts concentrated on the subjects: (a) simulation techniques for 2D and 3D foams; (b) phase transition in a compressible foam; and (c) TCP structures.

The dynamic properties of sandwich structures based on metal-ceramic foams.

DOT National Transportation Integrated Search

2014-01-01

The present research program has studied the fracture properties of closed pore metal-ceramic foams for their potential applications as core systems in sandwich structures. The composite foams were created at Fireline, Inc. (Youngstown, OH) using the...

Characterization of 17-4 PH stainless steel foam for biomedical applications in simulated body fluid and artificial saliva environments.

PubMed

Mutlu, Ilven; Oktay, Enver

2013-04-01

Highly porous 17-4 PH stainless steel foam for biomedical applications was produced by space holder technique. Metal release and weight loss from 17-4 PH stainless steel foams was investigated in simulated body fluid and artificial saliva environments by static immersion tests. Inductively coupled plasma-mass spectrometer was employed to measure the concentrations of various metal ions released from the 17-4 PH stainless steel foams into simulated body fluids and artificial saliva. Effect of immersion time and pH value on metal release and weight loss in simulated body fluid and artificial saliva were determined. Pore morphology, pore size and mechanical properties of the 17-4 PH stainless steel foams were close to human cancellous bone. Copyright © 2012 Elsevier B.V. All rights reserved.

Heat exchanger using graphite foam

DOEpatents

Campagna, Michael Joseph; Callas, James John

2012-09-25

A heat exchanger is disclosed. The heat exchanger may have an inlet configured to receive a first fluid and an outlet configured to discharge the first fluid. The heat exchanger may further have at least one passageway configured to conduct the first fluid from the inlet to the outlet. The at least one passageway may be composed of a graphite foam and a layer of graphite material on the exterior of the graphite foam. The layer of graphite material may form at least a partial barrier between the first fluid and a second fluid external to the at least one passageway.

On the determination of a generalized Darcy equation for yield stress fluid in porous media using a LB TRT scheme

NASA Astrophysics Data System (ADS)

Talon, Laurent; Chevalier, Thibaud

2014-11-01

Non-Newtonian fluids have practical applications in very different domains. Indeed, polymer mixture, paints, slurries, colloidal suspensions, emulsions, foams or heavy oil present complex rheologies. Among the large number of different non-Newtonian fluids an important class of behavior is represented by the yield-stress fluids, viz. fluids that require a minimum of stress to flow. Yield stress fluids are usually modelled as a Bingham fluid or by the Herschel-Bulkley equation. However, simulating flow of a Bingham fluid in porous media still remains a challenging task as the yield stress may significantly alter the numerical stability and precision. In the present work, we use a Lattice-Boltzmann TRT scheme to determine this type of flow in a synthetic porous medium or fracture. Different pressure drops ΔP have been applied in order to derive a generalization of the Darcy's equation. Three different scaling regimes can be distinguished when plotting the dimensionless flow rate q as function of the distance to the critical pressure ΔP - ΔPc . In this presentation, we will investigate the importance of the heterogeneities on those flowing regimes. ANR-12-MONU-0011.

Computational Fluids Domain Reduction to a Simplified Fluid Network

DTIC Science & Technology

2012-04-19

readily available read/ write software library. Code components from the open source projects OpenFoam and Paraview were explored for their adaptability...to the project. Both Paraview and OpenFoam read polyhedral mesh. OpenFoam does not read results data. Paraview actually allows for user “filters

Processing, Microstructure, and Properties of Engineered Diboride Structures

NASA Astrophysics Data System (ADS)

Wittmaier, Connor Charles

The mechanical properties and processing parameters of boride ceramics in foam and laminate architectures were evaluated. The ceramic reticulated foam was produced through a polymer substrate replication technique and the hardness and compressive strength were tested. The laminate structure was tested to evaluate the flexure strength and work of fracture as a function of temperature. The foam architecture was produced using a TiB2 slurry coating on a polyurethane reticulated foam preform. Foams sintered to 2150°C displayed an average grain size of 8.9 +/- 7.3 microm, and a hardness of 17.3 +/- 2.4 GPa. Crush testing foams were sintered at 1975°C, and displayed a specific strength of 208 +/- 63 kPa with an overall porosity of 97%. For these specimens, it is likely that microcracking lowered the hardness, but the overall strength was controlled by the bulk density. The laminate structures were fabricated using alternating layers of ZrB 2 and C-10 vol% ZrB2. The structures were fabricated through the shaping of ceramic loaded thermoplastic polymers that underwent burnout and hot pressing cycles. These specimens had strong phase ZrB2 layers that were about 150 mum thick alternating with weak phase layers that were about 20 mum thick. Specimens exhibited a maximum flexure strength of 311 +/- 10 MPa at 1600°C, and an increased work of fracture compared to conventional ZrB2 ceramics. The maximum fraction of inelastic work of fracture occurred at room temperature, and decreased as temperature increased. This was reflected in the length of the crack path through the specimen. Deflected cracks travelled through the center of the C-ZrB2 layers in the material in Mode II fracture.

Experimental Evaluation of Equivalent-Fluid Models for Melamine Foam

NASA Technical Reports Server (NTRS)

Allen, Albert R.; Schiller, Noah H.

2016-01-01

Melamine foam is a soft porous material commonly used in noise control applications. Many models exist to represent porous materials at various levels of fidelity. This work focuses on rigid frame equivalent fluid models, which represent the foam as a fluid with a complex speed of sound and density. There are several empirical models available to determine these frequency dependent parameters based on an estimate of the material flow resistivity. Alternatively, these properties can be experimentally educed using an impedance tube setup. Since vibroacoustic models are generally sensitive to these properties, this paper assesses the accuracy of several empirical models relative to impedance tube measurements collected with melamine foam samples. Diffuse field sound absorption measurements collected using large test articles in a laboratory are also compared with absorption predictions determined using model-based and measured foam properties. Melamine foam slabs of various thicknesses are considered.

Enhanced Remedial Amendment Delivery to Subsurface Using Shear Thinning Fluid and Aqueous Foam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhong, Lirong; Szecsody, James E.; Oostrom, Martinus

2011-04-23

A major issue with in situ subsurface remediation is the ability to achieve an even spatial distribution of remedial amendments to the contamination zones in an aquifer or vadose zone. Delivery of amendment to the aquifer using shear thinning fluid and to the vadose zone using aqueous foam has the potential to enhance the amendment distribution into desired locations and improve the remediation. 2-D saturated flow cell experiments were conducted to evaluate the enhanced sweeping, contaminant removal, and amendment persistence achieved by shear thinning fluid delivery. Bio-polymer xanthan gum solution was used as the shear thinning fluid. Unsaturated 1-D columnmore » and 2-D flow cell experiments were conducted to evaluate the mitigation of contaminant mobilization, amendment uniform distribution enhancement, and lateral delivery improvement by foam delivery. Surfactant sodium lauryl ether sulfate was used as the foaming agent. It was demonstrated that the shear thinning fluid injection enhanced the fluid sweeping over a heterogeneous system and increased the delivery of remedial amendment into low-permeability zones. The persistence of the amendment distributed into the low-perm zones by the shear thinning fluid was prolonged compared to that of amendment distributed by water injection. Foam delivery of amendment was shown to mitigate the mobilization of highly mobile contaminant from sediments under vadose zone conditions. Foam delivery also achieved more uniform amendment distribution in a heterogeneous unsaturated system, and demonstrated remarkable increasing in lateral distribution of the injected liquid compared to direct liquid injection.« less

A nonsemen copulatory fluid influences the outcome of sperm competition in Japanese quail.

PubMed

Finseth, F R; Iacovelli, S R; Harrison, R G; Adkins-Regan, E K

2013-09-01

Sperm competition is a powerful and widespread evolutionary force that drives the divergence of behavioural, physiological and morphological traits. Elucidating the mechanisms governing differential fertilization success is a fundamental question of sperm competition. Both sperm and nonsperm ejaculate components can influence sperm competition outcomes. Here, we investigate the role of a nonsemen copulatory fluid in sperm competition. Male Japanese quail possess a gland that makes meringue-like foam. Males produce and store foam independent of sperm and seminal fluid, yet transfer foam to females during copulation. We tested whether foam influenced the outcome of sperm competition by varying foam state and mating order in competitive matings. We found that the presence of foam from one male decreased the relative fertilization success of a rival, and that foam from a given male increased the probability he obtained any fertilizations. Mating order also affected competitive success. Males mated first fertilized proportionally more eggs in a clutch and had more matings with any fertilizations than subsequent males. We conclude that the function of foam in sperm competition is mediated through the positive interaction of foam with a male's sperm, and we speculate whether the benefit is achieved through improving sperm storage, fertilizing efficiency or retention. Our results suggest males can evolve complex strategies to gain fertilizations at the expense of rivals as foam, a copulatory fluid not required for fertilization, nevertheless, has important effects on reproductive performance under competition. © 2013 The Authors. Journal of Evolutionary Biology © 2013 European Society For Evolutionary Biology.

Innovative energy absorbing devices based on composite tubes

NASA Astrophysics Data System (ADS)

Tiwari, Chandrashekhar

Analytical and experimental study of innovative load limiting and energy absorbing devices are presented here. The devices are based on composite tubes and can be categorized in to two groups based upon the energy absorbing mechanisms exhibited by them, namely: foam crushing and foam fracturing. The device based on foam crushing as the energy absorbing mechanism is composed of light weight elastic-plastic foam filling inside an angle ply composite tube. The tube is tailored to have a high Poisson’s ratio (>20). Upon being loaded the device experiences large transverse contraction resulting in rapid decrease in diameter. At a certain axial load the foam core begins to crush and energy is dissipated. This device is termed as crush tube device. The device based upon foam shear fracture as the energy absorbing mechanism involves an elastic-plastic core foam in annulus of two concentric extension-twist coupled composite tubes with opposite angles of fibers. The core foam is bonded to the inner and outer tube walls. Upon being loaded axially, the tubes twist in opposite directions and fracture the core foam in out of plane shear and thus dissipate the energy stored. The device is termed as sandwich core device (SCD). The devices exhibit variations in force-displacement characteristics with changes in design and material parameters, resulting in wide range of energy absorption capabilities. A flexible matrix composite system was selected, which was composed of high stiffness carbon fibers as reinforcements in relatively low stiffness polyurethane matrix, based upon large strain to failure capabilities and large beneficial elastic couplings. Linear and non-linear analytical models were developed encapsulating large deformation theory of the laminated composite shells (using non-linear strain energy formulation) to the fracture mechanics of core foam and elastic-plastic deformation theory of the foam filling. The non-linear model is capable of including material and geometric nonlinearities that arise from large deformation and fiber reorientation. Developed non-linear analysis predicts the behavior of extension-twist coupled and angle ply flexible matrix composite tubes under multi-axial loadings. The predicted results show close correlation with experimental findings. It was also found that these devices exhibit variations with respect to rate of loading. It was found that the novel energy absorbing devices are capable of providing 4-5 times higher specific energy absorption (SEA) than currently used devices for similar purposes (such as wire bender which has SEA of 3.6 J/g).

Foam Transport in Porous Media - A Review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Z. F.; Freedman, Vicky L.; Zhong, Lirong

2009-11-11

Amendment solutions with or without surfactants have been used to remove contaminants from soil. However, it has drawbacks such that the amendment solution often mobilizes the plume, and its movement is controlled by gravity and preferential flow paths. Foam is an emulsion-like, two-phase system in which gas cells are dispersed in a liquid and separated by thin liquid films called lamellae. Potential advantages of using foams in sub-surface remediation include providing better control on the volume of fluids injected, uniformity of contact, and the ability to contain the migration of contaminant laden liquids. It is expected that foam can servemore » as a carrier of amendments for vadose zone remediation, e.g., at the Hanford Site. As part of the U.S. Department of Energy’s EM-20 program, a numerical simulation capability will be added to the Subsurface Transport Over Multiple Phases (STOMP) flow simulator. The primary purpose of this document is to review the modeling approaches of foam transport in porous media. However, as an aid to understanding the simulation approaches, some experiments under unsaturated conditions and the processes of foam transport are also reviewed. Foam may be formed when the surfactant concentration is above the critical micelle concentration. There are two main types of foams – the ball foam (microfoam) and the polyhedral foam. The characteristics of bulk foam are described by the properties such as foam quality, texture, stability, density, surface tension, disjoining pressure, etc. Foam has been used to flush contaminants such as metals, organics, and nonaqueous phase liquids from unsaturated soil. Ball foam, or colloidal gas aphrons, reportedly have been used for soil flushing in contaminated site remediation and was found to be more efficient than surfactant solutions on the basis of weight of contaminant removed per gram of surfactant. Experiments also indicate that the polyhedral foam can be used to enhance soil remediation. The transport of foam in porous media is complicated in that the number of lamellae present governs flow characteristics such as viscosity, relative permeability, fluid distribution, and interactions between fluids. Hence, foam is a non-Newtonian fluid. During transport, foam destruction and formation occur. The net result of the two processes determines the foam texture (i.e., bubble density). Some of the foam may be trapped during transport. According to the impacts of the aqueous and gas flow rates, foam flow generally has two regimes – weak and strong foam. There is also a minimum pressure gradient to initiate foam flow and a critical capillary for foam to be sustained. Similar to other fluids, the transport of foam is described by Darcy’s law with the exception that the foam viscosity is variable. Three major approaches to modeling foam transport in porous media are the empirical, semi-empirical, and mechanistic methods. Mechanistic approaches can be complete in principal but may be difficult to obtain reliable parameters, whereas empirical and semi-empirical approaches can be limited by the detail used to describe foam rheology and mobility. Mechanistic approaches include the bubble population-balance model, the network/percolation theory, the catastrophe theory, and the filtration theory. Among these methods, all were developed for modeling polyhedral foam with the exception that the method based on the filtration theory was for the ball foam (microfoam).« less

Deformation and Plateau Region of Functionally Graded Aluminum Foam by Amount Combinations of Added Blowing Agent.

PubMed

Hangai, Yoshihiko; Utsunomiya, Takao; Kuwazuru, Osamu; Kitahara, Soichiro; Yoshikawa, Nobuhiro

2015-10-21

Recently, to further improve the performance of aluminum foam, functionally graded (FG) aluminum foams, whose pore structure varies with their position, have been developed. In this study, three types of FG aluminum foam of aluminum alloy die casting ADC12 with combinations of two different amounts of added blowing agent titanium(II) hydride (TiH₂) powder were fabricated by a friction stir welding (FSW) route precursor foaming method. The combinations of 1.0-0 mass %, 0.4-0 mass %, and 0.2-0 mass % TiH₂ were selected as the amounts of TiH₂ relative to the mass of the volume stirred by FSW. The static compression tests of the fabricated FG aluminum foams were carried out. The deformation and fracture of FG aluminum foams fundamentally started in the high-porosity (with TiH₂ addition) layer and shifted to the low-porosity (without TiH₂ addition) layer. The first and second plateau regions in the relationship between compressive stress and strain independently appeared with the occurrence of deformations and fractures in the high- and low-porosity layers. It was shown that FG aluminum foams, whose plateau region varies in steps by the combination of amounts of added TiH₂ ( i.e. , the combination of pore structures), can be fabricated.

An Overview of Spray-On Foam Insulation Applications on the Space Shuttle's External Tank: Foam Applications and Foam Shedding Mechanisms

NASA Technical Reports Server (NTRS)

Sullivan, Roy M.; Lerch, Bradley A.; Rogers, Patrick R.; Sparks, Scotty S.

2006-01-01

The Columbia Accident Investigation Board (CAIB) concluded that the cause of the tragic loss of the Space Shuttle Columbia and its crew was a breach in the thermal protection system on the leading edge of the left wing. The breach was initiated by a piece of insulating foam that separated from the left bipod ramp of the External Tank and struck the wing in the vicinity of the lower half of Reinforced Carbon-Carbon panel No. 8 at 81.9 seconds after launch. The CAIB conclusion has spawned numerous studies to identify the cause of and factors influencing foam shedding and foam debris liberation from the External Tank during ascent. The symposium on the Thermo-mechanics and Fracture of Space Shuttle External Tank Spray-On Foam Insulation is a collection of presentations that discuss the physics and mechanics of the ET SOFI with the objective of improving analytical and numerical methods for predicting foam thermo-mechanical and fracture behavior. This keynote presentation sets the stage for the presentations contained in this symposium by introducing the audience to the various types of SOFI applications on the Shuttle s External Tank and by discussing the various mechanisms that are believed to be the cause of foam shedding during the Shuttle s ascent to space

Multiscale Modeling of Multiphase Fluid Flow

DTIC Science & Technology

2016-08-01

the disparate time and length scales involved in modeling fluid flow and heat transfer. Molecular dynamics simulations were carried out to provide a...fluid dynamics methods were used to investigate the heat transfer process in open-cell micro-foam with phase change material; enhancement of natural...Computational fluid dynamics, Heat transfer, Phase change material in Micro-foam, Molecular Dynamics, Multiphase flow, Multiscale modeling, Natural

Sloshing of a bubbly magma reservoir as a mechanism of triggered eruptions

NASA Astrophysics Data System (ADS)

Namiki, Atsuko; Rivalta, Eleonora; Woith, Heiko; Walter, Thomas R.

2016-06-01

Large earthquakes sometimes activate volcanoes both in the near field as well as in the far field. One possible explanation is that shaking may increase the mobility of the volcanic gases stored in magma reservoirs and conduits. Here experimentally and theoretically we investigate how sloshing, the oscillatory motion of fluids contained in a shaking tank, may affect the presence and stability of bubbles and foams, with important implications for magma conduits and reservoirs. We adopt this concept from engineering: severe earthquakes are known to induce sloshing and damage petroleum tanks. Sloshing occurs in a partially filled tank or a fully filled tank with density-stratified fluids. These conditions are met at open summit conduits or at sealed magma reservoirs where a bubbly magma layer overlays a newly injected denser magma layer. We conducted sloshing experiments by shaking a rectangular tank partially filled with liquids, bubbly fluids (foams) and fully filled with density-stratified fluids; i.e., a foam layer overlying a liquid layer. In experiments with foams, we find that foam collapse occurs for oscillations near the resonance frequency of the fluid layer. Low viscosity and large bubble size favor foam collapse during sloshing. In the layered case, the collapsed foam mixes with the underlying liquid layer. Based on scaling considerations, we constrain the conditions for the occurrence of foam collapse in natural magma reservoirs. We find that seismic waves with lower frequencies < 1 Hz, usually excited by large earthquakes, can resonate with magma reservoirs whose width is > 0.5 m. Strong ground motion > 0.1 m s- 1 can excite sloshing with sufficient amplitude to collapse a magma foam in an open conduit or a foam overlying basaltic magma in a closed magma reservoir. The gas released from the collapsed foam may infiltrate the rock or diffuse through pores, enhancing heat transfer, or may generate a gas slug to cause a magmatic eruption. The overturn in the magma reservoir provides new nucleation sites which may help to prepare a following/delayed eruption. Mt. Fuji erupted 49 days after the large Hoei earthquake (1707) both dacitic and basaltic magmas. The eruption might have been triggered by magma mixing through sloshing.

Crack Initiation and Growth in Rigid Polymeric Closed-Cell Foam Cryogenic Applications

NASA Technical Reports Server (NTRS)

Sayyah, Tarek; Steeve, Brian; Wells, Doug

2006-01-01

Cryogenic vessels, such as the Space Shuttle External Tank, are often insulated with closed-cell foam because of its low thermal conductivity. The coefficient of thermal expansion mismatch between the foam and metallic substrate places the foam under a biaxial tension gradient through the foam thickness. The total foam thickness affects the slope of the stress gradient and is considered a significant contributor to the initiation of subsurface cracks. Rigid polymeric foams are brittle in nature and any subsurface cracks tend to propagate a finite distance toward the surface. This presentation investigates the relationship between foam thickness and crack initiation and subsequent crack growth, using linear elastic fracture mechanics, in a rigid polymeric closed-cell foam through analysis and comparison with experimental results.

Shallow Subsurface transport and eruption of basaltic foam

NASA Astrophysics Data System (ADS)

Parcheta, C. E.; Mitchell, K. L.

2016-12-01

Volcanic fissure vents are difficult to quantify, and details of eruptive behavior are elusive even though it is the most common eruption mechanism on Earth and across the solar system. A fissure's surface expression is typically concealed, but when a fissure remains exposed, its subsurface conduit can be mapped post-eruptively with VolcanoBot. The robot uses a NIR structured light sensor that reproduces a 3D surface model to cm-scale accuracy, documenting the shallow conduit. VolcanoBot3 has probed >1000m3 of volcanic fissure vents at the Mauna Ulu fissure system on Kilauea. Here we present the new 3D model of a flared vent on the Mauna Ulu fissure system. We see a self-similar pattern of irregularities on the fissure walls throughout the entire shallow subsurface, implying a fracture mechanical origin similar to faults. These irregularities are typically 1 m across, protrude 30 cm horizontally into the drained fissure, and have a vertical spacing of 2-3 m. However, irregularity size is variable and distinct with depth, potentially reflecting stratigraphy in the wall rock. Where piercing points are present, we infer the dike broke the wall rock in order to propagate upwards; where they are not, we infer that syn-eruptive mechanical erosion has taken place. One mechanism for mechanical erosion is supersonic shocks, which may occur in Hawaiian fountains. We are calculating the speed of sound in 64% basaltic foam, which appears to be the same velocity (or slightly slower) than inferred eruption velocities. Irregularities are larger than the maximum 10% wall roughness used in engineering fluid dynamic studies, indicating that magma fluid dynamics during fissure eruptions are probably not as passive nor as simple as previously thought. We are currently using the mapped conduit geometries and derived speed of sound for basaltic foam in fluid dynamical modeling of fissure-fed lava fountains.

Fluid-Driven Deformation of a Soft Porous Medium

NASA Astrophysics Data System (ADS)

Lutz, Tyler; Wilen, Larry; Wettlaufer, John

2017-11-01

Viscous drag forces resisting the flow of fluid through a soft porous medium are maintained by restoring forces associated with deformations in the solid matrix. We describe experimental measurements of the deformation of foam under a pressure-driven flow of water along a single axis. Image analysis techniques allow tracking of the foam displacement while pressure sensors allow measurement of the fluid pressure. Experiments are performed for a series of different pressure heads ranging from 10 to 90 psi, and the results are compared to theory. This work builds on previous measurements of the fluid-induced deformation of a bed of soft hydrogel spheres. Compared to the hydrogel system, foams have the advantage that the constituents of the porous medium do not rearrange during an experiment, but they have the disadvantage of having a high friction coefficient with any boundaries. We detail strategies to characterize and mitigate the effects of friction on the observed foam deformations.

Stochastic metallic-glass cellular structures exhibiting benchmark strength.

PubMed

Demetriou, Marios D; Veazey, Chris; Harmon, John S; Schramm, Joseph P; Johnson, William L

2008-10-03

By identifying the key characteristic "structural scales" that dictate the resistance of a porous metallic glass against buckling and fracture, stochastic highly porous metallic-glass structures are designed capable of yielding plastically and inheriting the high plastic yield strength of the amorphous metal. The strengths attainable by the present foams appear to equal or exceed those by highly engineered metal foams such as Ti-6Al-4V or ferrous-metal foams at comparable levels of porosity, placing the present metallic-glass foams among the strongest foams known to date.

Deformation and Plateau Region of Functionally Graded Aluminum Foam by Amount Combinations of Added Blowing Agent

PubMed Central

Hangai, Yoshihiko; Utsunomiya, Takao; Kuwazuru, Osamu; Kitahara, Soichiro; Yoshikawa, Nobuhiro

2015-01-01

Recently, to further improve the performance of aluminum foam, functionally graded (FG) aluminum foams, whose pore structure varies with their position, have been developed. In this study, three types of FG aluminum foam of aluminum alloy die casting ADC12 with combinations of two different amounts of added blowing agent titanium(II) hydride (TiH2) powder were fabricated by a friction stir welding (FSW) route precursor foaming method. The combinations of 1.0–0 mass %, 0.4–0 mass %, and 0.2–0 mass % TiH2 were selected as the amounts of TiH2 relative to the mass of the volume stirred by FSW. The static compression tests of the fabricated FG aluminum foams were carried out. The deformation and fracture of FG aluminum foams fundamentally started in the high-porosity (with TiH2 addition) layer and shifted to the low-porosity (without TiH2 addition) layer. The first and second plateau regions in the relationship between compressive stress and strain independently appeared with the occurrence of deformations and fractures in the high- and low-porosity layers. It was shown that FG aluminum foams, whose plateau region varies in steps by the combination of amounts of added TiH2 (i.e., the combination of pore structures), can be fabricated. PMID:28793626

Enhanced Amendment Delivery to Subsurface Using Shear Thinning Fluid and Aqueous Foam for Metal, Radionuclide, and NAPL Remediation

NASA Astrophysics Data System (ADS)

Zhong, L.; Szecsody, J.; Li, X.; Oostrom, M.; Truex, M.

2010-12-01

In many contamination sites, removal of contaminants by any active remediation efforts is not practical due to the high cost and technological limitations. Alternatively, in situ remediation is expected to be the most important remediation strategy. Delivery of reactive amendment to the contamination zone is essential for the reactions between the contaminants and remedial amendments to proceed in situ. It is a challenge to effectively deliver remedial amendment to the subsurface contamination source areas in both aquifer and vadose zone. In aquifer, heterogeneity induces fluid bypassing the low-permeability zones, resulting in certain contaminated areas inaccessible to the remedial amendment delivered by water injection, thus inhibiting the success of remedial operations. In vadose zone in situ remediation, conventional solution injection and infiltration for amendment delivery have difficulties to achieve successful lateral spreading and uniform distribution of the reactive media. These approaches also tend to displace highly mobile metal and radionuclide contaminants such as hexavalent chromium [Cr(VI)] and technetium (Tc-99), causing spreading of contaminations. Shear thinning fluid and aqueous foam can be applied to enhance the amendment delivery and improve in situ subsurface remediation efficiency under aquifer and vadose zone conditions, respectively. Column and 2-D flow cell experiments were conducted to demonstrate the enhanced delivery and improved remediation achieved by the application of shear thinning fluid and foam injection at the laboratory scale. Solutions of biopolymer xanthan gum were used as the shear thinning delivering fluids. Surfactant sodium lauryl ether sulfate (STEOL CS-330) was the foaming agent. The shear thinning fluid delivery (STFD) considerably improved the sweeping efficiency over a heterogeneous system and enhanced the non-aqueous liquid phase (NAPL) removal. The delivery of amendment into low-perm zones (LPZs) by STFD also increased the persistence of amendment solution in the LPZs after injection. Immobilization of Tc-99 was improved when a reductant was delivered by foam versus by water-based solution to contaminated vadose zone sediments. Foam delivery remarkably improved the lateral distribution of fluids compared to direct liquid injection. In heterogeneous vadose zone formation, foam injection increased the liquid flow in the high permeable zones into which very limited fluid was distributed during liquid infiltration, demonstrating improved amendment distribution uniformity in the heterogeneous system by foam delivery.

Finite Element Modeling of Tensile Deformation Behaviors of Iron Syntactic Foam with Hollow Glass Microspheres

PubMed Central

Cho, Yi Je; Lee, Wookjin; Park, Yong Ho

2017-01-01

The elastoplastic deformation behaviors of hollow glass microspheres/iron syntactic foam under tension were modeled using a representative volume element (RVE) approach. The three-dimensional microstructures of the iron syntactic foam with 5 wt % glass microspheres were reconstructed using the random sequential adsorption algorithm. The constitutive behavior of the elastoplasticity in the iron matrix and the elastic-brittle failure for the glass microsphere were simulated in the models. An appropriate RVE size was statistically determined by evaluating elastic modulus, Poisson’s ratio, and yield strength in terms of model sizes and boundary conditions. The model was validated by the agreement with experimental findings. The tensile deformation mechanism of the syntactic foam considering the fracture of the microspheres was then investigated. In addition, the feasibility of introducing the interfacial deboning behavior to the proposed model was briefly investigated to improve the accuracy in depicting fracture behaviors of the syntactic foam. It is thought that the modeling techniques and the model itself have major potential for applications not only in the study of hollow glass microspheres/iron syntactic foams, but also for the design of composites with a high modulus matrix and high strength reinforcement. PMID:29048346

Compressive Deformation Behavior of Closed-Cell Micro-Pore Magnesium Composite Foam.

PubMed

Wang, Jing; Wang, Nannan; Liu, Xin; Ding, Jian; Xia, Xingchuan; Chen, Xueguang; Zhao, Weimin

2018-05-04

The closed-cell micro-pore magnesium composite foam with hollow ceramic microspheres (CMs) was fabricated by a modified melt foaming method. The effect of CMs on the compressive deformation behavior of CM-containing magnesium composite foam was investigated. Optical microscopy and scanning electron microscopy were used for observation of the microstructure. Finite element modeling of the magnesium composite foam was established to predict localized stress, fracture of CMs, and the compressive deformation behavior of the foam. The results showed that CMs and pores directly affected the compressive deformation behavior of the magnesium composite foam by sharing a part of load applied on the foam. Meanwhile, the presence of Mg₂Si phase influenced the mechanical properties of the foam by acting as the crack source during the compression process.

Compressive Deformation Behavior of Closed-Cell Micro-Pore Magnesium Composite Foam

PubMed Central

Wang, Jing; Wang, Nannan; Liu, Xin; Ding, Jian; Xia, Xingchuan; Chen, Xueguang; Zhao, Weimin

2018-01-01

The closed-cell micro-pore magnesium composite foam with hollow ceramic microspheres (CMs) was fabricated by a modified melt foaming method. The effect of CMs on the compressive deformation behavior of CM-containing magnesium composite foam was investigated. Optical microscopy and scanning electron microscopy were used for observation of the microstructure. Finite element modeling of the magnesium composite foam was established to predict localized stress, fracture of CMs, and the compressive deformation behavior of the foam. The results showed that CMs and pores directly affected the compressive deformation behavior of the magnesium composite foam by sharing a part of load applied on the foam. Meanwhile, the presence of Mg2Si phase influenced the mechanical properties of the foam by acting as the crack source during the compression process. PMID:29734700

Use of Microcellular Foam Particles for Encapsulation of Viscous fluids

USDA-ARS?s Scientific Manuscript database

A relatively new starch product with various novel applications is a porous microcellular foam [1,2]. The foam product is made by dehydrating a starch hydrogel in a solvent such as ethanol and then removing the solvent to form a foam product [1,2]. Starch microcellular foam has very small pores and ...

Yield-stress fluids foams: flow patterns and controlled production in T-junction and flow-focusing devices.

PubMed

Laborie, Benoit; Rouyer, Florence; Angelescu, Dan E; Lorenceau, Elise

2016-11-23

We study the formation of yield-stress fluid foams in millifluidic flow-focusing and T-junction devices. First, we provide a phase diagram for the unsteady operating regimes of bubble production when the gas pressure and the yield-stress fluid flow rate are imposed. Three regimes are identified: a co-flow of gas and yield-stress fluid, a transient production of bubble and a flow of yield-stress fluid only. Taking wall slip into account, we provide a model for the pressure at the onset of bubble formation. Then, we detail and compare two simple methods to ensure steady bubble production: regulation of the gas pressure or flow-rate. These techniques, which are easy to implement, thus open pathways for controlled production of dry yield-stress fluid foams as shown at the end of this article.

Guide to NavyFOAM V1.0

DTIC Science & Technology

2011-04-01

NavyFOAM has been developed using an open-source CFD software tool-kit ( OpenFOAM ) that draws heavily upon object-oriented programming. The...numerical methods and the physical models in the original version of OpenFOAM have been upgraded in an effort to improve accuracy and robustness of...computational fluid dynamics OpenFOAM , Object Oriented Programming (OOP) (CFD), NavyFOAM, 16. SECURITY CLASSIFICATION OF: a. REPORT UNCLASSIFIED b

Podoplanin immunopositive lymphatic vessels at the implant interface in a rat model of osteoporotic fractures.

PubMed

Lips, Katrin Susanne; Kauschke, Vivien; Hartmann, Sonja; Thormann, Ulrich; Ray, Seemun; Kampschulte, Marian; Langheinrich, Alexander; Schumacher, Matthias; Gelinsky, Michael; Heinemann, Sascha; Hanke, Thomas; Kautz, Armin R; Schnabelrauch, Matthias; Schnettler, Reinhard; Heiss, Christian; Alt, Volker; Kilian, Olaf

2013-01-01

Insertion of bone substitution materials accelerates healing of osteoporotic fractures. Biodegradable materials are preferred for application in osteoporotic patients to avoid a second surgery for implant replacement. Degraded implant fragments are often absorbed by macrophages that are removed from the fracture side via passage through veins or lymphatic vessels. We investigated if lymphatic vessels occur in osteoporotic bone defects and whether they are regulated by the use of different materials. To address this issue osteoporosis was induced in rats using the classical method of bilateral ovariectomy and additional calcium and vitamin deficient diet. In addition, wedge-shaped defects of 3, 4, or 5 mm were generated in the distal metaphyseal area of femur via osteotomy. The 4 mm defects were subsequently used for implantation studies where bone substitution materials of calcium phosphate cement, composites of collagen and silica, and iron foams with interconnecting pores were inserted. Different materials were partly additionally functionalized by strontium or bisphosphonate whose positive effects in osteoporosis treatment are well known. The lymphatic vessels were identified by immunohistochemistry using an antibody against podoplanin. Podoplanin immunopositive lymphatic vessels were detected in the granulation tissue filling the fracture gap, surrounding the implant and growing into the iron foam through its interconnected pores. Significant more lymphatic capillaries were counted at the implant interface of composite, strontium and bisphosphonate functionalized iron foam. A significant increase was also observed in the number of lymphatics situated in the pores of strontium coated iron foam. In conclusion, our results indicate the occurrence of lymphatic vessels in osteoporotic bone. Our results show that lymphatic vessels are localized at the implant interface and in the fracture gap where they might be involved in the removal of lymphocytes, macrophages, debris and the implants degradation products. Therefore the lymphatic vessels are involved in implant integration and fracture healing.

Podoplanin Immunopositive Lymphatic Vessels at the Implant Interface in a Rat Model of Osteoporotic Fractures

PubMed Central

Lips, Katrin Susanne; Kauschke, Vivien; Hartmann, Sonja; Thormann, Ulrich; Ray, Seemun; Kampschulte, Marian; Langheinrich, Alexander; Schumacher, Matthias; Gelinsky, Michael; Heinemann, Sascha; Hanke, Thomas; Kautz, Armin R.; Schnabelrauch, Matthias; Schnettler, Reinhard; Heiss, Christian; Alt, Volker; Kilian, Olaf

2013-01-01

Insertion of bone substitution materials accelerates healing of osteoporotic fractures. Biodegradable materials are preferred for application in osteoporotic patients to avoid a second surgery for implant replacement. Degraded implant fragments are often absorbed by macrophages that are removed from the fracture side via passage through veins or lymphatic vessels. We investigated if lymphatic vessels occur in osteoporotic bone defects and whether they are regulated by the use of different materials. To address this issue osteoporosis was induced in rats using the classical method of bilateral ovariectomy and additional calcium and vitamin deficient diet. In addition, wedge-shaped defects of 3, 4, or 5 mm were generated in the distal metaphyseal area of femur via osteotomy. The 4 mm defects were subsequently used for implantation studies where bone substitution materials of calcium phosphate cement, composites of collagen and silica, and iron foams with interconnecting pores were inserted. Different materials were partly additionally functionalized by strontium or bisphosphonate whose positive effects in osteoporosis treatment are well known. The lymphatic vessels were identified by immunohistochemistry using an antibody against podoplanin. Podoplanin immunopositive lymphatic vessels were detected in the granulation tissue filling the fracture gap, surrounding the implant and growing into the iron foam through its interconnected pores. Significant more lymphatic capillaries were counted at the implant interface of composite, strontium and bisphosphonate functionalized iron foam. A significant increase was also observed in the number of lymphatics situated in the pores of strontium coated iron foam. In conclusion, our results indicate the occurrence of lymphatic vessels in osteoporotic bone. Our results show that lymphatic vessels are localized at the implant interface and in the fracture gap where they might be involved in the removal of lymphocytes, macrophages, debris and the implants degradation products. Therefore the lymphatic vessels are involved in implant integration and fracture healing. PMID:24130867

DOE Office of Scientific and Technical Information (OSTI.GOV)

William C. Maurer; William J. McDonald; Thomas E. Williams

Underbalanced drilling is experiencing growth at a rate that rivals that of horizontal drilling in the mid-1980s and coiled-tubing drilling in the 1990s. Problems remain, however, for applying underbalanced drilling in a wider range of geological settings and drilling environments. This report addresses developments under this DOE project to develop products aimed at overcoming these problems. During Phase I of the DOE project, market analyses showed that up to 12,000 wells per year (i.e., 30% of all wells) will be drilled underbalanced in the U.S.A. within the next ten years. A user-friendly foam fluid hydraulics model (FOAM) was developed formore » a PC Windows environment during Phase I. FOAM predicts circulating pressures and flow characteristics of foam fluids used in underbalanced drilling operations. FOAM is based on the best available mathematical models, and was validated through comparison to existing models, laboratory test data and field data. This model does not handle two-phase flow or air and mist drilling where the foam quality is above 0.97. This FOAM model was greatly expanded during Phase II including adding an improved foam rheological model and a ''matching'' feature that allows the model to be field calibrated. During Phase I, a lightweight drilling fluid was developed that uses hollow glass spheres (HGS) to reduce the density of the mud to less than that of water. HGS fluids have several advantages over aerated fluids, including they are incompressible, they reduce corrosion and vibration problems, they allow the use of mud-pulse MWD tools, and they eliminate high compressor and nitrogen costs. Phase II tests showed that HGS significantly reduce formation damage with water-based drilling and completion fluids and thereby potentially can increase oil and gas production in wells drilled with water-based fluids. Extensive rheological testing was conducted with HGS drilling and completion fluids during Phase II. These tests showed that the HGS fluids act similarly to conventional fluids and that they have potential application in many areas, including underbalanced drilling, completions, and riserless drilling. Early field tests under this project are encouraging. These led to limited tests by industry (which are also described). Further field tests and cost analyses are needed to demonstrate the viability of HGS fluids in different applications. Once their effectiveness is demonstrated, they should find widespread application and should significantly reduce drilling costs and increase oil and gas production rates. A number of important oilfield applications for HGS outside of Underbalanced Drilling were identified. One of these--Dual Gradient Drilling (DGD) for deepwater exploration and development--is very promising. Investigative work on DGD under the project is reported, along with definition of a large joint-industry project resulting from the work. Other innovative products/applications are highlighted in the report including the use of HGS as a cement additive.« less

Development of drilling foams for geothermal applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

McDonald, W.J.; Remont, L.J.; Rehm, W.A.

The use of foam drilling fluids in geothermal applications is addressed. A description of foams - what they are, how they are used, their properties, equipment required to use them, the advantages and disadvantages of foams, etc. - is presented. Geothermal applications are discussed. Results of industry interviews presented indicate significant potential for foams, but also indicate significant technical problems to be solved to achieve this potential. Testing procedures and results of tests on representative foams provide a basis for work to develop high-temperature foams.

Closed-cell crystalline foams: self-assembling, resonant metamaterials.

PubMed

Spadoni, Alessandro; Höhler, Reinhard; Cohen-Addad, Sylvie; Dorodnitsyn, Vladimir

2014-04-01

Internal degrees of freedom and periodic structure are critical requirements in the design of acoustic/elastic metamaterials since they can give rise to extraordinary properties like negative effective mass and stiffness. However, they are challenging to realize in three dimensions. Closed-cell, crystalline foams are a particularly advantageous basis to develop metamaterials as they intrinsically have a complex microstructure, exhibiting internal resonances. Recently self-assembly techniques have been implemented to produce such foams: a Kelvin (body centered cubic) foam, a face centered cubic foam, and a Weaire-Phelan structure. Numerical models are employed to demonstrate that such foams are superanisotropic, selectively behaving as a fluid or a solid, pentamode solids as a result of fluid-structure interaction, in addition to having regimes characterized by film resonances and high density of states. Microstructural deformations obtained from numerical models allow the derivation of equivalent mechanical models.

Fast Response, Open-Celled Porous, Shape Memory Effect Actuators with Integrated Attachments

NASA Technical Reports Server (NTRS)

Jardine, Andrew Peter (Inventor)

2015-01-01

This invention relates to the exploitation of porous foam articles exhibiting the Shape Memory Effect as actuators. Each foam article is composed of a plurality of geometric shapes, such that some geometric shapes can fit snugly into or around rigid mating connectors that attach the Shape Memory foam article intimately into the load path between a static structure and a moveable structure. The foam is open-celled, composed of a plurality of interconnected struts whose mean diameter can vary from approximately 50 to 500 microns. Gases and fluids flowing through the foam transfer heat rapidly with the struts, providing rapid Shape Memory Effect transformations. Embodiments of porous foam articles as torsional actuators and approximately planar structures are disposed. Simple, integral connection systems exploiting the ability to supply large loads to a structure, and that can also supply hot and cold gases and fluids to effect rapid actuation are also disposed.

Hypersonic simulations using open-source CFD and DSMC solvers

NASA Astrophysics Data System (ADS)

Casseau, V.; Scanlon, T. J.; John, B.; Emerson, D. R.; Brown, R. E.

2016-11-01

Hypersonic hybrid hydrodynamic-molecular gas flow solvers are required to satisfy the two essential requirements of any high-speed reacting code, these being physical accuracy and computational efficiency. The James Weir Fluids Laboratory at the University of Strathclyde is currently developing an open-source hybrid code which will eventually reconcile the direct simulation Monte-Carlo method, making use of the OpenFOAM application called dsmcFoam, and the newly coded open-source two-temperature computational fluid dynamics solver named hy2Foam. In conjunction with employing the CVDV chemistry-vibration model in hy2Foam, novel use is made of the QK rates in a CFD solver. In this paper, further testing is performed, in particular with the CFD solver, to ensure its efficacy before considering more advanced test cases. The hy2Foam and dsmcFoam codes have shown to compare reasonably well, thus providing a useful basis for other codes to compare against.

PUFoam : A novel open-source CFD solver for the simulation of polyurethane foams

NASA Astrophysics Data System (ADS)

Karimi, M.; Droghetti, H.; Marchisio, D. L.

2017-08-01

In this work a transient three-dimensional mathematical model is formulated and validated for the simulation of polyurethane (PU) foams. The model is based on computational fluid dynamics (CFD) and is coupled with a population balance equation (PBE) to describe the evolution of the gas bubbles/cells within the PU foam. The front face of the expanding foam is monitored on the basis of the volume-of-fluid (VOF) method using a compressible solver available in OpenFOAM version 3.0.1. The solver is additionally supplemented to include the PBE, solved with the quadrature method of moments (QMOM), the polymerization kinetics, an adequate rheological model and a simple model for the foam thermal conductivity. The new solver is labelled as PUFoam and is, for the first time in this work, validated for 12 different mixing-cup experiments. Comparison of the time evolution of the predicted and experimentally measured density and temperature of the PU foam shows the potentials and limitations of the approach.

Wall effects in Stokes experiment with a liquid foam

NASA Astrophysics Data System (ADS)

Gao, Haijing; Subramani, Hariprasad; Harris, Michael; Basaran, Osman

2011-11-01

Liquid foams are widely used in numerous applications ranging from the oil and gas industry to beauty, healthcare, and household products industries. A fundamental understanding of the relationships between the properties of liquid foams and their flow responses is, however, still in its infancy compared to that involving the fluid dynamics of simple fluids. In this talk, the flow of a dry liquid foam around a spherical bead, i.e. the Stokes problem for liquid foams, is studied experimentally. In contrast to previous work (cf. Cantat 2006), the focus of the present research is to probe the effect of a solid wall that is located a few bubble radii from the bead. The new experimental results show that the elastic modulus of dry liquid foams is directly proportional to the surface tension of the foaming agents and inversely proportional to the average bubble size in the foams, in agreement with previous theoretical and experimental studies. The experiments further show that the close proximity of the solid wall causes profound structural changes to the gas bubbles as the foam flows past the bead. A good understanding of these structural changes and how they can affect the elastic modulus of foams can be indispensable in formulating improved models for accurately describing the dynamical response of foams within the realm of continuum mechanics.

Structural Continuum Modeling of Space Shuttle External Tank Foam Insulation

NASA Technical Reports Server (NTRS)

Steeve, Brian; Ayala, Sam; Purlee, T. Eric; Shaw, Phillip

2006-01-01

The Space Shuttle External Tank is covered with rigid polymeric closed-cell foam insulation to prevent ice formation, protect the metallic tank from aerodynamic heating, and control the breakup of the tank during re-entry. The cryogenic state of the tank, as well as the ascent into a vacuum environment, places this foam under significant stress. Because the loss of the foam during ascent poses a critical risk to the shuttle orbiter, there is much interest in understanding the stress state in the foam insulation and how it may contribute to fracture and debris loss. Several foam applications on the external tank have been analyzed using finite element methods. This presentation describes the approach used to model the foam material behavior and compares analytical results to experiments.

Optimising the Parallelisation of OpenFOAM Simulations

DTIC Science & Technology

2014-06-01

UNCLASSIFIED UNCLASSIFIED Optimising the Parallelisation of OpenFOAM Simulations Shannon Keough Maritime Division Defence...Science and Technology Organisation DSTO-TR-2987 ABSTRACT The OpenFOAM computational fluid dynamics toolbox allows parallel computation of...performance of a given high performance computing cluster with several OpenFOAM cases, running using a combination of MPI libraries and corresponding MPI

Visualizing Oil Process Dynamics in Porous Media with Micromodels

NASA Astrophysics Data System (ADS)

Biswal, S. L.

2016-12-01

The use of foam in enhanced oil recovery (EOR) applications is being considered for gas mobility control to ensure pore-trapped oil can be effectively displaced. In fractured reservoirs, gas tends to channel only through the highly permeability regions, bypassing the less permeable porous matrix, where most of the residual oil remains. Because of the unique transport problems presented by the large permeability contrast between fractures and adjacent porous media, we aim to understand the mechanism by which foam transitions from the fracture to the matrix and how initially trapped oil can be displaced and ultimately recovered. My lab has generated micromodels, which are combined with high-speed imaging to visualize foam transport in models with permeability contrasts, fractures, and multiple phases. The wettability of these surfaces can be altered to mimic the heterogeneous wettability found in reservoir systems. We have shown how foam quality can be modulated by adjusting the ratio of gas flow ratio to aqueous flow rate in a flow focusing system and this foam quality influences sweep efficiency in heterogeneous porous media systems. I will discuss how this understanding has allowed us to design better foam EOR processes. I will also highlight our recent efforts in ashaltene deposition. Asphaltene deposition is a common cause of significant flow assurance problems in wellbores and production equipment as well as near-wellbore regions in oil reservoirs. I will present our results for visualizing real time asphaltene deposition from model and crude oils using microfluidic devices. In particular, we consider porous-media micromodel designs to represent various flow conditions typical of that found in oil flow processes. Also, four stages of deposition have been found and investigated in the pore scale and with qualitatively macroscopic total collector efficiency as well as Hamaker expressions for interacting asphaltenes with surfaces. By understanding the nature and the mechanisms of asphaltene deposits, we increase our ability to design cost effective mitigation strategies that includes the development of a new generation of asphaltene deposition inhibitors and improved methods for prevention and treatment of this problem.

Shooting in a foam.

PubMed

Le Goff, Anne; Quéré, David; Clanet, Christophe

2014-09-21

We study the motion of a solid sphere after its fast impact on a bath of liquid foam. We identify two regimes of deceleration. At short times, the velocity is still large and the foam behaves similar to a Newtonian fluid of constant viscosity. Then we measure a velocity threshold below which the sphere starts experiencing the foam's elasticity. We interpret this behavior using a visco-elasto-plastic model for foam rheology. Finally we discuss the possibility of stopping a projectile in the foam, and evaluate the capture efficiency.

Encapsulated proppants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.

2018-01-30

A capsule for carrying a proppant for emplaced in a formation containing formation fluid by a hydraulic fracture operation using a fracturing fluid. The capsule includes a capsule body. The capsule body includes a proppant. There is a surface layer on the capsule body that is permeable to the formation fluid or the fracturing fluid or is permeable to both the formation fluid and the fracturing fluid. The proppant material is dry cement that interacts with the formation fluid or the fracturing fluid or both the formation fluid and the fracturing fluid that migrate through the surface layer and ismore » taken up by the dry cement causing the dry cement to harden.« less

Encapsulated proppants

DOEpatents

Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Roberts, Jeffery James; Spadaccini, Christopher M.; Stolaroff, Joshuah K.

2018-01-09

A capsule for carrying a proppant for emplaced in a formation containing formation fluid by a hydraulic fracture operation using a fracturing fluid. The capsule includes a capsule body. The capsule body includes a proppant. There is a surface layer on the capsule body that is permeable to the formation fluid or the fracturing fluid or is permeable to both the formation fluid and the fracturing fluid. The proppant material is dry cement that interacts with the formation fluid or the fracturing fluid or both the formation fluid and the fracturing fluid that migrate through the surface layer and is taken up by the dry cement causing the dry cement to harden.

An overview on the characterization and mechanical behavior of nanoporous Gold

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hodge, A M; Hayes, J R; Caro, J A

2005-09-13

In this paper we present what we believe are the most pressing issues in understanding the mechanical behavior of nanoporous foams. We have postulated that a gold foam presents the best candidate for a systematic study of nanoporous foams since it can be synthesized with a wide range of ligaments sizes and densities. We have also conducted preliminary tests that demonstrate (a) Au foams have a fracture behavior dictated by the ligament size, and (b) nanoporous Au is a high yield strength material. Thus, we have demonstrated the potential in developing nanoporous foams as a new class of high yieldmore » strength/low density materials.« less

Using Shock Waves to Improve the Acoustic Properties of Closed-Cell Foams

NASA Astrophysics Data System (ADS)

Brouillette, M.; Hébert, C.; Atalla, N.; Doutres, O.

Foam microstructure can be seen as a collection of interlinked struts forming a packing of cells interconnected to others through pores. Materials with a totality of pores closed by thin membranes are called closed-cell foams. The filtration and acoustic efficiency of closed-cell foams is poor compared to open-cell foams since it is very difficult for the fluid or the acoustic waves to penetrate inside the material.

Processing of poly(hydroxybutyrate-co-hydroxyvalerate)-based bionanocomposite foams using supercritical fluids

Treesearch

Alireza Javadi; Yottha Srithep; Craig C. Clemons; L-S. Turng; Shaoqin Gong

2012-01-01

Supercritical fluid (SCF) N2 was used as a physical foaming agent to fabricate microcellular injection-molded poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV)–poly(butylene adipate-co-terephthalate) (PBAT)–hyperbranched-polymer (HBP)–nanoclay (NC) bionanocomposites. The effects of incorporating HBP and NC on the morphological, mechanical, and...

Cryogenic foam insulation: Abstracted publications

NASA Technical Reports Server (NTRS)

Williamson, F. R.

1977-01-01

A group of documents were chosen and abstracted which contain information on the properties of foam materials and on the use of foams as thermal insulation at cryogenic temperatures. The properties include thermal properties, mechanical properties, and compatibility properties with oxygen and other cryogenic fluids. Uses of foams include applications as thermal insulation for spacecraft propellant tanks, and for liquefied natural gas storage tanks and pipelines.

The control of ultrasonic transmission by the metamaterials structure of electrorheological fluid and metal foam

NASA Astrophysics Data System (ADS)

Li, Linlin; Wang, Mingzhong; Wang, Jiahui; Zhao, Xiaopeng

2017-11-01

A metamaterial structure formed by foamed metal and starch and oil-based electrorheological (ER) fluid is designed in this paper. Experiments show that the metamaterial structure exhibits a regulation effect on the amplitude and phase of the transmitted waves of 35-80 kHz ultra-wideband ultrasonic waves in water. With the increase of the electric field, the transmission amplitude and phase of the ultrasonic wave increases, whereas the control ability of the same gradient electric field decreases. The amplitude of the transmission controlled by the metamaterial structure and electric field increases at first, and then decreases with the increase in volume fraction of the ER fluid. Thus, it is thought that the interaction between the microstructure produced by the rheological properties of the ER fluid and the porous foam metal affects the propagation of the acoustic wave.

Additive Manufacturing of Syntactic Foams: Part 2: Specimen Printing and Mechanical Property Characterization

NASA Astrophysics Data System (ADS)

Singh, Ashish Kumar; Saltonstall, Brooks; Patil, Balu; Hoffmann, Niklas; Doddamani, Mrityunjay; Gupta, Nikhil

2018-03-01

High-density polyethylene (HDPE) and its fly ash cenosphere-filled syntactic foam filaments have been recently developed. These filaments are used for three-dimensional (3D) printing using a commercial printer. The developed syntactic foam filament (HDPE40) contains 40 wt.% cenospheres in the HDPE matrix. Printing parameters for HDPE and HDPE40 were optimized for use in widely available commercial printers, and specimens were three-dimensionally (3D) printed for tensile testing at strain rate of 10-3 s-1. Process optimization resulted in smooth operation of the 3D printer without nozzle clogging or cenosphere fracture during the printing process. Characterization results revealed that the tensile modulus values of 3D-printed HDPE and HDPE40 specimens were higher than those of injection-molded specimens, while the tensile strength was comparable, but the fracture strain and density were lower.

Dynamics of poroelastic foams

NASA Astrophysics Data System (ADS)

Forterre, Yoel; Sobac, Benjamin

2010-11-01

Soft poroelastic structures are widespread in biological tissues such as cartilaginous joints in bones, blood-filled placentae or plant organs. Here we investigate the dynamics of open elastic foams immersed in viscous fluids, as model soft poroelastic materials. The experiment consists in slowly compacting blocs of polyurethane solid foam embedded in silicon oil-tanks and studying their relaxation to equilibrium when the confining stress is suddenly released. Measurements of the local fluid pressure and foam velocity field are compared with a simple two-phase flow approach. For small initial compactions, the results show quantitative agreement with the classical diffusion theory of soil consolidation (Terzaghi, Biot). On the other hand, for large initial compactions, the dynamics exhibits long relaxation times and decompaction fronts, which are mainly controlled by the highly non-linear mechanical response of the foam. The analogy between this process and the evaporation of a polymer melt close to the glass transition will be briefly discussed.

Development of an Improved Simulator for Chemical and Microbial EOR Methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pope, Gary A.; Sepehrnoori, Kamy; Delshad, Mojdeh

2000-09-11

The objective of this research was to extend the capability of an existing simulator (UTCHEM) to improved oil recovery methods that use surfactants, polymers, gels, alkaline chemicals, microorganisms and foam as well as various combinations of these in both conventional and naturally fractured oil reservoirs. Task 1 is the addition of a dual-porosity model for chemical improved of recovery processes in naturally fractured oil reservoirs. Task 2 is the addition of a foam model. Task 3 addresses several numerical and coding enhancements that will greatly improve the versatility and performance of UTCHEM. Task 4 is the enhancements of physical propertymore » models.« less

A Novel CO2-Responsive Viscoelastic Amphiphilic Surfactant Fluid for Fracking in Enhanced Oil/Gas Recovery

NASA Astrophysics Data System (ADS)

Zhong, L.; Wu, X.; Dai, C.

2017-12-01

Over the past decade, the rapid rise of unconventional shale gas and tight sandstone oil development through horizontal drilling and high volume hydraulic fracturing has expanded the extraction of hydrocarbon resources. Hydraulic fracturing fluids play very important roles in enhanced oil/gas recovery. However, damage to the reservoir rock and environmental contamination caused by hydraulic fracturing flowback fluids has raised serious concerns. The development of reservoir rock friendly and environmental benign fracturing fluids is in immediate demand. Studies to improve properties of hydraulic fracturing fluids have found that viscoelastic surfactant (VES) fracturing fluid can increase the productivity of gas/oil and be efficiently extracted after fracturing. Compared to conventional polymer fracturing fluid, VES fracturing fluid has many advantages, such as few components, easy preparation, good proppant transport capacity, low damage to cracks and formations, and environment friendly. In this work, we are developing a novel CO2-responsive VES fracking fluid that can readily be reused. This fluid has a gelling-breaking process that can be easily controlled by the presence of CO2 and its pressure. We synthesized erucamidopropyl dimethylamine (EA) as a thickening agent for hydraulic fracturing fluid. The influence of temperature, presence of CO2 and pressure on the viscoelastic behavior of this fluid was then investigated through rheological measurements. The fracturing fluid performance and recycle property were lastly studied using core flooding tests. We expect this fluid finds applications not only in enhanced oil/gas recovery, but also in areas such as controlling groundwater pollution and microfluidics.

AC induction field heating of graphite foam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klett, James W.; Rios, Orlando; Kisner, Roger

A magneto-energy apparatus includes an electromagnetic field source for generating a time-varying electromagnetic field. A graphite foam conductor is disposed within the electromagnetic field. The graphite foam when exposed to the time-varying electromagnetic field conducts an induced electric current, the electric current heating the graphite foam. An energy conversion device utilizes heat energy from the heated graphite foam to perform a heat energy consuming function. A device for heating a fluid and a method of converting energy are also disclosed.

Assessment of flushing methods for the removal of heavy chlorinated compounds DNAPL in an alluvial aquifer.

PubMed

Maire, Julien; Joubert, Antoine; Kaifas, Delphine; Invernizzi, Thomas; Marduel, Julien; Colombano, Stéfan; Cazaux, David; Marion, Cédric; Klein, Pierre-Yves; Dumestre, Alain; Fatin-Rouge, Nicolas

2018-01-15

Immiscible mobilization and foam flushing were assessed as low surfactant consuming technologies, for the enhanced recovery of dense non-aqueous phase liquid (DNAPL) residual at a site contaminated by heavy chlorinated compounds. Preliminary experiments in well-controlled conditions demonstrated the phenomena involved in these remediation technologies and their limitations. Furthermore, we characterized the technologies according to by their surfactant consumption (per kg of DNAPL recovered) and the final DNAPL saturation reached. Surfactant foam flushing (SFF) produced lower DNAPL saturation than immiscible mobilization, thanks to its higher viscosity. However, its efficiency is strongly correlated to the pressure gradient (▽P) used during injection, and that is limited by risks of soil fracturing. The two technologies were tested in field cells (10m×10m×10m) delimited by cement/bentonite walls anchored in the clayey substratum. The deepest soil layer was the most contaminated. It was composed of silt-sandy soil and had an average hydraulic conductivity of 10 -4 ms -1 . Field results show that we should now model flushing fluid propagation to design efficient set-ups for recovering the displaced DNAPL. Copyright © 2017 Elsevier B.V. All rights reserved.

Investigation of foam flotation and phase partitioning techniques

NASA Technical Reports Server (NTRS)

Currin, B. L.

1985-01-01

The present status of foam flotation as a separation process is evaluated and limitations for cells and proteins are determined. Possible applications of foam flotation to separations in microgravity are discussed. Application of the fluid mechanical aspects of foam separation techniques is made to phase partitioning in order to investigate the viscous drag forces that may effect the partitioning of cells in a two phase poly(ethylene glycol) and dextran system.

SediFoam: A general-purpose, open-source CFD-DEM solver for particle-laden flow with emphasis on sediment transport

NASA Astrophysics Data System (ADS)

Sun, Rui; Xiao, Heng

2016-04-01

With the growth of available computational resource, CFD-DEM (computational fluid dynamics-discrete element method) becomes an increasingly promising and feasible approach for the study of sediment transport. Several existing CFD-DEM solvers are applied in chemical engineering and mining industry. However, a robust CFD-DEM solver for the simulation of sediment transport is still desirable. In this work, the development of a three-dimensional, massively parallel, and open-source CFD-DEM solver SediFoam is detailed. This solver is built based on open-source solvers OpenFOAM and LAMMPS. OpenFOAM is a CFD toolbox that can perform three-dimensional fluid flow simulations on unstructured meshes; LAMMPS is a massively parallel DEM solver for molecular dynamics. Several validation tests of SediFoam are performed using cases of a wide range of complexities. The results obtained in the present simulations are consistent with those in the literature, which demonstrates the capability of SediFoam for sediment transport applications. In addition to the validation test, the parallel efficiency of SediFoam is studied to test the performance of the code for large-scale and complex simulations. The parallel efficiency tests show that the scalability of SediFoam is satisfactory in the simulations using up to O(107) particles.

Flow of foams in two-dimensional disordered porous media

NASA Astrophysics Data System (ADS)

Dollet, Benjamin; Geraud, Baudouin; Jones, Sian A.; Meheust, Yves; Cantat, Isabelle; Institut de Physique de Rennes Team; Geosciences Rennes Team

2015-11-01

Liquid foams are a yield stress fluid with elastic properties. When a foam flow is confined by solid walls, viscous dissipation arises from the contact zones between soap films and walls, giving very peculiar friction laws. In particular, foams potentially invade narrow pores much more efficiently than Newtonian fluids, which is of great importance for enhanced oil recovery. To quantify this effect, we study experimentally flows of foam in a model two-dimensional porous medium, consisting of an assembly of circular obstacles placed randomly in a Hele-Shaw cell, and use image analysis to quantify foam flow at the local scale. We show that bubbles split as they flow through the porous medium, by a mechanism of film pinching during contact with an obstacle, yielding two daughter bubbles per split bubble. We quantify the evolution of the bubble size distribution as a function of the distance along the porous medium, the splitting probability as a function of bubble size, and the probability distribution function of the daughter bubbles. We propose an evolution equation to model this splitting phenomenon and compare it successfully to the experiments, showing how at long distance, the porous medium itself dictates the size distribution of the foam.

Investigation of foam flow in a 3D printed porous medium in the presence of oil.

PubMed

Osei-Bonsu, Kofi; Grassia, Paul; Shokri, Nima

2017-03-15

Foams demonstrate great potential for displacing fluids in porous media which is applicable to a variety of subsurface operations such as the enhanced oil recovery and soil remediation. The application of foam in these processes is due to its unique ability to reduce gas mobility by increasing its effective viscosity and to divert gas to un-swept low permeability zones in porous media. The presence of oil in porous media is detrimental to the stability of foams which can influence its success as a displacing fluid. In the present work, we have conducted a systematic series of experiments using a well-characterised porous medium manufactured by 3D printing technique to evaluate the influence of oil on the dynamics of foam displacement under different boundary conditions. The effects of the type of oil, foam quality and foam flow rate were investigated. Our results reveal that generation of stable foam is delayed in the presence of light oil in the porous medium compared to heavy oil. Additionally, it was observed that the dynamics of oil entrapment was dictated by the stability of foam in the presence of oil. Furthermore, foams with high gas fraction appeared to be less stable in the presence of oil lowering its recovery efficiency. Pore-scale inspection of foam-oil dynamics during displacement revealed formation of a less stable front as the foam quality increased, leading to less oil recovery. This study extends the physical understanding of oil displacement by foam in porous media and provides new physical insights regarding the parameters influencing this process. Copyright © 2016. Published by Elsevier Inc.

Long-period events, the most characteristic seismicity accompanying the emplacement and extrusion of a lava dome in Galeras Volcano, Colombia, in 1991

USGS Publications Warehouse

Gil, Cruz F.; Chouet, B.A.

1997-01-01

Since its reactivation in 1988 the principal eruptions of Galeras Volcano occurred on May 4-9, 1989, July 16, 1992, and January 14, March 23, April 3, April 14 and June 7, 1993. The initial eruption was a phreatic event which clearly marked a new period of activity. A lava dome was extruded within the main crater in October 1991 and subsequently destroyed in an explosive eruption on July 16, 1992. The eruptions that followed were all vulcanian-type explosions. The seismicity accompanying the emplacement, extrusion, and destruction of the lava dome was dominated by a mix of long-period (LP) events and tremor displaying a variety of waveforms. Repetitive LP events with dominant periods in the range 0.2-1 s were observed in October and November 1991 and visually correlated with short energetic pulses of gas venting through a crack bisecting the dome surface. Each LP event was characterized by a weak precursory signal with dominant periods in the range 0.05-0.1 s lasting roughly 7 s. Using the fluid-driven crack model of Chouet (1988, 1992), we infer that two distinct cracks may have acted as sources for the LP and precursor signals. Spectral analyses of the data yield the following parameters for the LP source: crack length, 240-360 m; crack width, 130-150 m; crack aperture, 0.5-3.4 mm; crack stiffness, 100-500; sound speed of fluid, 880 m/s; and excess pressure, 0.01-0.19 MPa. Similar analyses yield the parameters of the precursor source: crack length, 20-30 m; crack width, 15-25 m; crack aperture, 2.3-8.7 mm; crack stiffness, 5-15; sound speed of fluid, 140 m/s; and excess pressure, 0.06-0.15 MPa. Combined with geologic and thermodynamic constraints obtained from field observations, these seismic parameters suggest a gas-release mechanism in which the episodic collapse of a foam layer trapped at the top of the magma column subjacent to the dome releases a slug of pressurized gas which escapes to the surface while dilating a preexisting system of cracks in the dome structure. Accordingly, the fracture observed on the crystallized dome body is the surface extension of the LP-source crack, where LP activity is induced by the rapid emission and expansion of gas flowing through this conduit. The width and aperture of the crack estimated in the model are in good agreement with the length and aperture of the fracture estimated from visual observations. The source parameters of the precursor signal are suggestive of a nozzle-like conduit connecting the LP-source crack to the underlying magma reservoir. Excitation of this conduit segment is attributed to the rapid emission and acceleration of the frothy fluid resulting from the collapse of the foam layer at the top of the reservoir. The calculated periodicity of foam collapse events is in agreement with the observed average rate of thirteen LP events per hour.

Fabrication of Aluminum Foam-Filled Thin-Wall Steel Tube by Friction Welding and Its Compression Properties.

PubMed

Hangai, Yoshihiko; Saito, Masaki; Utsunomiya, Takao; Kitahara, Soichiro; Kuwazuru, Osamu; Yoshikawa, Nobuhiro

2014-09-19

Aluminum foam has received considerable attention in various fields and is expected to be used as an engineering material owing to its high energy absorption properties and light weight. To improve the mechanical properties of aluminum foam, combining it with dense tubes, such as aluminum foam-filled tubes, was considered necessary. In this study, an aluminum foam-filled steel tube, which consisted of ADC12 aluminum foam and a thin-wall steel tube, was successfully fabricated by friction welding. It was shown that a diffusion bonding layer with a thickness of approximately 10 μm was formed, indicating that strong bonding between the aluminum foam and the steel tube was realized. By the X-ray computed tomography observation of pore structures, the fabrication of an aluminum foam-filled tube with almost uniform pore structures over the entire specimen was confirmed. In addition, it was confirmed that the aluminum foam-filled steel tube exhibited mechanical properties superior to those of the ADC12 aluminum foam and steel tube. This is considered to be attributed to the combination of the aluminum foam and steel tube, which particularly prevents the brittle fracture and collapse of the ADC12 foam by the steel tube, along with the strong metal bonding between the aluminum foam and the steel tube.

The Influence of Fracturing Fluids on Fracturing Processes: A Comparison Between Water, Oil and SC-CO2

NASA Astrophysics Data System (ADS)

Wang, Jiehao; Elsworth, Derek; Wu, Yu; Liu, Jishan; Zhu, Wancheng; Liu, Yu

2018-01-01

Conventional water-based fracturing treatments may not work well for many shale gas reservoirs. This is due to the fact that shale gas formations are much more sensitive to water because of the significant capillary effects and the potentially high contents of swelling clay, each of which may result in the impairment of productivity. As an alternative to water-based fluids, gaseous stimulants not only avoid this potential impairment in productivity, but also conserve water as a resource and may sequester greenhouse gases underground. However, experimental observations have shown that different fracturing fluids yield variations in the induced fracture. During the hydraulic fracturing process, fracturing fluids will penetrate into the borehole wall, and the evolution of the fracture(s) then results from the coupled phenomena of fluid flow, solid deformation and damage. To represent this, coupled models of rock damage mechanics and fluid flow for both slightly compressible fluids and CO2 are presented. We investigate the fracturing processes driven by pressurization of three kinds of fluids: water, viscous oil and supercritical CO2. Simulation results indicate that SC-CO2-based fracturing indeed has a lower breakdown pressure, as observed in experiments, and may develop fractures with greater complexity than those developed with water-based and oil-based fracturing. We explore the relation between the breakdown pressure to both the dynamic viscosity and the interfacial tension of the fracturing fluids. Modeling demonstrates an increase in the breakdown pressure with an increase both in the dynamic viscosity and in the interfacial tension, consistent with experimental observations.

A Numerical Study of Factors Affecting Fracture-Fluid Cleanup and Produced Gas/Water in Marcellus Shale: Part II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seales, Maxian B.; Dilmore, Robert; Ertekin, Turgay

Horizontal wells combined with successful multistage-hydraulic-fracture treatments are currently the most-established method for effectively stimulating and enabling economic development of gas-bearing organic-rich shale formations. Fracture cleanup in the stimulated reservoir volume (SRV) is critical to stimulation effectiveness and long-term well performance. But, fluid cleanup is often hampered by formation damage, and post-fracture well performance frequently falls to less than expectations. A systematic study of the factors that hinder fracture-fluid cleanup in shale formations can help optimize fracture treatments and better quantify long-term volumes of produced water and gas. Fracture-fluid cleanup is a complex process influenced by mutliphase flow through porousmore » media (relative permeability hysteresis, capillary pressure), reservoir-rock and -fluid properties, fracture-fluid properties, proppant placement, fracture-treatment parameters, and subsequent flowback and field operations. Changing SRV and fracture conductivity as production progresses further adds to the complexity of this problem. Numerical simulation is the best and most-practical approach to investigate such a complicated blend of mechanisms, parameters, their interactions, and subsequent effect on fracture-fluid cleanup and well deliverability. Here, a 3D, two-phase, dual-porosity model was used to investigate the effect of mutliphase flow, proppant crushing, proppant diagenesis, shut-in time, reservoir-rock compaction, gas slippage, and gas desorption on fracture-fluid cleanup and well performance in Marcellus Shale. Our findings have shed light on the factors that substantially constrain efficient fracture-fluid cleanup in gas shales, and we have provided guidelines for improved fracture-treatment designs and water management.« less

A Numerical Study of Factors Affecting Fracture-Fluid Cleanup and Produced Gas/Water in Marcellus Shale: Part II

DOE PAGES

Seales, Maxian B.; Dilmore, Robert; Ertekin, Turgay; ...

2017-04-01

Horizontal wells combined with successful multistage-hydraulic-fracture treatments are currently the most-established method for effectively stimulating and enabling economic development of gas-bearing organic-rich shale formations. Fracture cleanup in the stimulated reservoir volume (SRV) is critical to stimulation effectiveness and long-term well performance. But, fluid cleanup is often hampered by formation damage, and post-fracture well performance frequently falls to less than expectations. A systematic study of the factors that hinder fracture-fluid cleanup in shale formations can help optimize fracture treatments and better quantify long-term volumes of produced water and gas. Fracture-fluid cleanup is a complex process influenced by mutliphase flow through porousmore » media (relative permeability hysteresis, capillary pressure), reservoir-rock and -fluid properties, fracture-fluid properties, proppant placement, fracture-treatment parameters, and subsequent flowback and field operations. Changing SRV and fracture conductivity as production progresses further adds to the complexity of this problem. Numerical simulation is the best and most-practical approach to investigate such a complicated blend of mechanisms, parameters, their interactions, and subsequent effect on fracture-fluid cleanup and well deliverability. Here, a 3D, two-phase, dual-porosity model was used to investigate the effect of mutliphase flow, proppant crushing, proppant diagenesis, shut-in time, reservoir-rock compaction, gas slippage, and gas desorption on fracture-fluid cleanup and well performance in Marcellus Shale. Our findings have shed light on the factors that substantially constrain efficient fracture-fluid cleanup in gas shales, and we have provided guidelines for improved fracture-treatment designs and water management.« less

The Effect of Loading Rate on Hydraulic Fracturing in Synthetic Granite - a Discrete Element Study

NASA Astrophysics Data System (ADS)

Tomac, I.; Gutierrez, M.

2015-12-01

Hydraulic fracture initiation and propagation from a borehole in hard synthetic rock is modeled using the two dimensional Discrete Element Method (DEM). DEM uses previously established procedure for modeling the strength and deformation parameters of quasi-brittle rocks with the Bonded Particle Model (Itasca, 2004). A series of simulations of laboratory tests on granite in DEM serve as a reference for synthetic rock behavior. Fracturing is enabled by breaking parallel bonds between DEM particles as a result of the local stress state. Subsequent bond breakage induces fracture propagation during a time-stepping procedure. Hydraulic fracturing occurs when pressurized fluid induces hoop stresses around the wellbore which cause rock fracturing and serves for geo-reservoir permeability enhancement in oil, gas and geothermal industries. In DEM, a network of fluid pipes and reservoirs is used for mathematical calculation of fluid flow through narrow channels between DEM particles, where the hydro-mechanical coupling is fully enabled. The fluid flow calculation is superimposed with DEM stress-strain calculation at each time step. As a result, the fluid pressures during borehole pressurization in hydraulic fracturing, as well as, during the fracture propagation from the borehole, can be simulated. The objective of this study is to investigate numerically a hypothesis that fluid pressurization rate, or the fluid flow rate, influences upon character, shape and velocity of fracture propagation in rock. The second objective is to better understand and define constraints which are important for successful fracture propagation in quasi-brittle rock from the perspective of flow rate, fluid density, viscosity and compressibility relative to the rock physical properties. Results from this study indicate that not only too high fluid flow rates cause fracture arrest and multiple fracture branching from the borehole, but also that the relative compressibility of fracturing fluid and rock plays a significant role in fracture propagation velocity. Fluid viscosity effects are similar to the loading rate effects, because in both cases the rapid buildup of the pressure in the wellbore in absence of the inflow of the fluid into initiated fracture causes induction of multiple simultaneous fracture branches at the wellbore wall.

Non-Newtonian fluid flow in 2D fracture networks

NASA Astrophysics Data System (ADS)

Zou, L.; Håkansson, U.; Cvetkovic, V.

2017-12-01

Modeling of non-Newtonian fluid (e.g., drilling fluids and cement grouts) flow in fractured rocks is of interest in many geophysical and industrial practices, such as drilling operations, enhanced oil recovery and rock grouting. In fractured rock masses, the flow paths are dominated by fractures, which are often represented as discrete fracture networks (DFN). In the literature, many studies have been devoted to Newtonian fluid (e.g., groundwater) flow in fractured rock using the DFN concept, but few works are dedicated to non-Newtonian fluids.In this study, a generalized flow equation for common non-Newtonian fluids (such as Bingham, power-law and Herschel-Bulkley) in a single fracture is obtained from the analytical solutions for non-Newtonian fluid discharge between smooth parallel plates. Using Monte Carlo sampling based on site characterization data for the distribution of geometrical features (e.g., density, length, aperture and orientations) in crystalline fractured rock, a two dimensional (2D) DFN model is constructed for generic flow simulations. Due to complex properties of non-Newtonian fluids, the relationship between fluid discharge and the pressure gradient is nonlinear. A Galerkin finite element method solver is developed to iteratively solve the obtained nonlinear governing equations for the 2D DFN model. Using DFN realizations, simulation results for different geometrical distributions of the fracture network and different non-Newtonian fluid properties are presented to illustrate the spatial discharge distributions. The impact of geometrical structures and the fluid properties on the non-Newtonian fluid flow in 2D DFN is examined statistically. The results generally show that modeling non-Newtonian fluid flow in fractured rock as a DFN is feasible, and that the discharge distribution may be significantly affected by the geometrical structures as well as by the fluid constitutive properties.

Porous Foam Based Wick Structures for Loop Heat Pipes

NASA Technical Reports Server (NTRS)

Silk, Eric A.

2012-01-01

As part of an effort to identify cost efficient fabrication techniques for Loop Heat Pipe (LHP) construction, NASA Goddard Space Flight Center's Cryogenics and Fluids Branch collaborated with the U.S. Naval Academy s Aerospace Engineering Department in Spring 2012 to investigate the viability of carbon foam as a wick material within LHPs. The carbon foam was manufactured by ERG Aerospace and machined to geometric specifications at the U.S. Naval Academy s Materials, Mechanics and Structures Machine Shop. NASA GSFC s Fractal Loop Heat Pipe (developed under SBIR contract #NAS5-02112) was used as the validation LHP platform. In a horizontal orientation, the FLHP system demonstrated a heat flux of 75 Watts per square centimeter with deionized water as the working fluid. Also, no failed start-ups occurred during the 6 week performance testing period. The success of this study validated that foam can be used as a wick structure. Furthermore, given the COTS status of foam materials this study is one more step towards development of a low cost LHP.

How to Study Thermal Applications of Open-Cell Metal Foam: Experiments and Computational Fluid Dynamics

PubMed Central

De Schampheleire, Sven; De Jaeger, Peter; De Kerpel, Kathleen; Ameel, Bernd; Huisseune, Henk; De Paepe, Michel

2016-01-01

This paper reviews the available methods to study thermal applications with open-cell metal foam. Both experimental and numerical work are discussed. For experimental research, the focus of this review is on the repeatability of the results. This is a major concern, as most studies only report the dependence of thermal properties on porosity and a number of pores per linear inch (PPI-value). A different approach, which is studied in this paper, is to characterize the foam using micro tomography scans with small voxel sizes. The results of these scans are compared to correlations from the open literature. Large differences are observed. For the numerical work, the focus is on studies using computational fluid dynamics. A novel way of determining the closure terms is proposed in this work. This is done through a numerical foam model based on micro tomography scan data. With this foam model, the closure terms are determined numerically. PMID:28787894

Effectiveness of using a new polyurethane foam multi-layer dressing in the sacral area to prevent the onset of pressure ulcer in the elderly with hip fractures: A pragmatic randomised controlled trial.

PubMed

Forni, Cristiana; D'Alessandro, Fabio; Gallerani, Pina; Genco, Rossana; Bolzon, Andrea; Bombino, Caterina; Mini, Sandra; Rocchegiani, Laura; Notarnicola, Teresa; Vitulli, Arianna; Amodeo, Alfredo; Celli, Guglielmo; Taddia, Patrizia

2018-06-01

Hip fractures in the elderly are a serious problem for the health service due to the high rate of complications. One of these complications is pressure ulcers that, according to the literature, occur in 8.8% to 55% of patients and mainly arise in the sacral area. The present randomised controlled trial tests whether applying a new innovative multi-layer polyurethane foam dressing (ALLEVYN LIFE™), reduces the onset of pressure ulcers in the sacral area. From March to December 2016, 359 fragility hip fracture patients were randomly divided into 2 groups: 182 in the control group and 177 in the experimental group. Pressure ulcers occurred overall in 36 patients (10%): 8 patients (4.5%) in the experimental group compared to 28 (15.4%) in the control group: P = 0.001, relative risk 0.29 (95% CI 0.14-0.61) with NNT of 9 (95% CI 6-21). In the experimental group the onset of pressure ulcers occurred on average on the 6th day compared to the 4th day in the control group (HR 4.4). Using polyurethane foam is effective at reducing the rate of pressure ulcers in the sacrum in elderly patients with hip fracture. The adhesiveness of this device also enables costs to be kept down. © 2018 The Authors. International Wound Journal published by Medicalhelplines.com Inc and John Wiley & Sons Ltd.

Kinetics of thermal and photo-initiated release of tris (1,3-dichloro-2-propyl) phosphate (TDCP) flame retardant from polyurethane foam materials.

PubMed

Ghanem, Raed A

2015-01-01

Kinetics of thermal and photo-initiated release of Tris (1.3-dichloro-2-propyl) phosphate (TDCP) from the polyurethane foam (PUF) materials were studied using a validated chromatographic method with linear calibration curve in the range of 0.03-400 μg mL(-1). Time dependence of TDCP leaching from foam samples was found to follow first-order kinetics; with rate constants directly dependent on ageing temperatures and intensity of UV radiation, rate constants for the thermally and photo initiated were 3.6 × 10(-3), 1.03 × 10(-2), 3.6 × 10(-2) and 3.94 × 10(-2) day(-1), respectively. Migration of TDCP from foam samples simulating skin or oral exposure were observed from all samples regardless of their ageing history, the presence of biological fluids found to enhance the migration rate. Oral exposure to foam material contains TDCP, which was simulated using the Head-over-Heels test, reveals that an average amount of ∼ 1.7% wt./wt. of the total amount of TDCP was found to leach into biological fluids, and it significantly increased to ∼ 6.0% wt./wt. due to ageing conditions. Direct contact between foam material and skin simulated by using the Contact Blotting test reveals that TDCP is transferred from both aged and un-aged samples at different rates, due to the presence of biological fluids; the transferred amount is increased with ageing conditions.

Nonequilibrium Interfacial Tension in Simple and Complex Fluids

NASA Astrophysics Data System (ADS)

Truzzolillo, Domenico; Mora, Serge; Dupas, Christelle; Cipelletti, Luca

2016-10-01

Interfacial tension between immiscible phases is a well-known phenomenon, which manifests itself in everyday life, from the shape of droplets and foam bubbles to the capillary rise of sap in plants or the locomotion of insects on a water surface. More than a century ago, Korteweg generalized this notion by arguing that stresses at the interface between two miscible fluids act transiently as an effective, nonequilibrium interfacial tension, before homogenization is eventually reached. In spite of its relevance in fields as diverse as geosciences, polymer physics, multiphase flows, and fluid removal, experiments and theoretical works on the interfacial tension of miscible systems are still scarce, and mostly restricted to molecular fluids. This leaves crucial questions unanswered, concerning the very existence of the effective interfacial tension, its stabilizing or destabilizing character, and its dependence on the fluid's composition and concentration gradients. We present an extensive set of measurements on miscible complex fluids that demonstrate the existence and the stabilizing character of the effective interfacial tension, unveil new regimes beyond Korteweg's predictions, and quantify its dependence on the nature of the fluids and the composition gradient at the interface. We introduce a simple yet general model that rationalizes nonequilibrium interfacial stresses to arbitrary mixtures, beyond Korteweg's small gradient regime, and show that the model captures remarkably well both our new measurements and literature data on molecular and polymer fluids. Finally, we briefly discuss the relevance of our model to a variety of interface-driven problems, from phase separation to fracture, which are not adequately captured by current approaches based on the assumption of small gradients.

Chemical Signatures of and Precursors to Fractures Using Fluid Inclusion Stratigraphy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lorie M. Dilley

Enhanced Geothermal Systems (EGS) are designed to recover heat from the subsurface by mechanically creating fractures in subsurface rocks. Open or recently closed fractures would be more susceptible to enhancing the permeability of the system. Identifying dense fracture areas as well as large open fractures from small fracture systems will assist in fracture stimulation site selection. Geothermal systems are constantly generating fractures (Moore, Morrow et al. 1987), and fluids and gases passing through rocks in these systems leave small fluid and gas samples trapped in healed microfractures. These fluid inclusions are faithful records of pore fluid chemistry. Fluid inclusions trappedmore » in minerals as the fractures heal are characteristic of the fluids that formed them, and this signature can be seen in fluid inclusion gas analysis. This report presents the results of the project to determine fracture locations by the chemical signatures from gas analysis of fluid inclusions. With this project we hope to test our assumptions that gas chemistry can distinguish if the fractures are open and bearing production fluids or represent prior active fractures and whether there are chemical signs of open fracture systems in the wall rock above the fracture. Fluid Inclusion Stratigraphy (FIS) is a method developed for the geothermal industry which applies the mass quantification of fluid inclusion gas data from drill cuttings and applying known gas ratios and compositions to determine depth profiles of fluid barriers in a modern geothermal system (Dilley, 2009; Dilley et al., 2005; Norman et al., 2005). Identifying key gas signatures associated with fractures for isolating geothermal fluid production is the latest advancement in the application of FIS to geothermal systems (Dilley and Norman, 2005; Dilley and Norman, 2007). Our hypothesis is that peaks in FIS data are related to location of fractures. Previous work (DOE Grant DE-FG36-06GO16057) has indicated differences in the chemical signature of fluid inclusions between open and closed fractures as well as differences in the chemical signature of open fractures between geothermal systems. Our hypothesis is that open fracture systems can be identified by their FIS chemical signature; that there are differences based on the mineral assemblages and geology of the system; and that there are chemical precursors in the wall rock above open, large fractures. Specific goals for this project are: (1) To build on the preliminary results which indicate that there are differences in the FIS signatures between open and closed fractures by identifying which chemical species indicate open fractures in both active geothermal systems and in hot, dry rock; (2) To evaluate the FIS signatures based on the geology of the fields; (3) To evaluate the FIS signatures based on the mineral assemblages in the fracture; and (4) To determine if there are specific chemical signatures in the wall rock above open, large fractures. This method promises to lower the cost of geothermal energy production in several ways. Knowledge of productive fractures in the boreholes will allow engineers to optimize well production. This information can aid in well testing decisions, well completion strategies, and in resource calculations. It will assist in determining the areas for future fracture enhancement. This will develop into one of the techniques in the 'tool bag' for creating and managing Enhanced Geothermal Systems.« less

A Numerical Study of Factors Affecting Fracture-Fluid Cleanup and Produced Gas/Water in Marcellus Shale: Part II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seales, Maxian B.; Dilmore, Robert; Ertekin, Turgay

Horizontal wells combined with successful multi-stage hydraulic fracture treatments are currently the most established method for effectively stimulating and enabling economic development of gas bearing organic-rich shale formations. Fracture cleanup in the Stimulated Reservoir Volume (SRV) is critical to stimulation effectiveness and long-term well performance. However, fluid cleanup is often hampered by formation damage, and post-fracture well performance frequently falls below expectations. A systematic study of the factors that hinder fracture fluid cleanup in shale formations can help optimize fracture treatments and better quantify long term volumes of produced water and gas. Fracture fluid cleanup is a complex process influencedmore » by multi-phase flow through porous media (relative permeability hysteresis, capillary pressure etc.), reservoir rock and fluid properties, fracture fluid properties, proppant placement, fracture treatment parameters, and subsequent flowback and field operations. Changing SRV and fracture conductivity as production progresses further adds to the complexity of this problem. Numerical simulation is the best, and most practical approach to investigate such a complicated blend of mechanisms, parameters, their interactions, and subsequent impact on fracture fluid cleanup and well deliverability. In this paper, a 3-dimensional, 2-phase, dual-porosity model was used to investigate the impact of multiphase flow, proppant crushing, proppant diagenesis, shut-in time, reservoir rock compaction, gas slippage, and gas desorption on fracture fluid cleanup, and well performance in Marcellus shale. The research findings have shed light on the factors that substantially constrains efficient fracture fluid cleanup in gas shales, and provided guidelines for improved fracture treatment designs and water management.« less

On the Versatility of Rheoreversible, Stimuli-responsive Hydraulic-Fracturing Fluids for Enhanced Geothermal Systems: Effect of Reservoir pH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernandez, Carlos A.; Shao, Hongbo; Bonneville, Alain

Abstract The primary challenge for the feasibility of enhanced geothermal systems (EGS) is to cost-effectively create high-permeability reservoirs inside deep crystalline bedrock. Although fracturing fluids are commonly used for oil/gas, standard fracturing methods are not developed or proven for EGS temperatures and pressures. Furthermore, the environmental impacts of currently used fracturing methods are only recently being determined. These authors recently reported an environmentally benign, CO2-activated, rheoreversible fracturing fluid that enhances permeability through fracturing due to in situ volume expansion and gel formation. The potential of this novel fracturing fluid is evaluated in this work towards its application at geothermal sitesmore » under different pH conditions. Laboratory-scale fracturing experiments using Coso Geothermal rock cores under different pH environments were performed followed by X-ray microtomography characterization. The results demonstrate that CO2-reactive aqueous solutions of environmentally amenable polyallylamine (PAA) consistently and reproducibly creates/propagates fracture networks through highly impermeable crystalline rock from Coso EGS sites at considerably lower effective stress as compared to conventional fracturing fluids. In addition, permeability was significantly enhanced in a wide range of formation-water pH values. This effective, and environmentally-friendly fracturing fluid technology represents a potential alternative to conventional fracturing fluids.« less

An instrumented pendulum system for measuring energy absorption during fracture insult to large animal joints in vivo.

PubMed

Diestelmeier, B W; Rudert, M J; Tochigi, Y; Baer, T E; Fredericks, D C; Brown, T D

2014-06-01

For systematic laboratory studies of bone fractures in general and intra-articular fractures in particular, it is often necessary to control for injury severity. Quantitatively, a parameter of primary interest in that regard is the energy absorbed during the injury event. For this purpose, a novel technique has been developed to measure energy absorption in experimental impaction. The specific application is for fracture insult to porcine hock (tibiotalar) joints in vivo, for which illustrative intra-operative data are reported. The instrumentation allowed for the measurement of the delivered kinetic energy and of the energy passed through the specimen during impaction. The energy absorbed by the specimen was calculated as the difference between those two values. A foam specimen validation study was first performed to compare the energy absorption measurements from the pendulum instrumentation versus the work of indentation performed by an MTS machine. Following validation, the pendulum apparatus was used to measure the energy absorbed during intra-articular fractures created in 14 minipig hock joints in vivo. The foam validation study showed close correspondence between the pendulum-measured energy absorption and MTS-performed work of indentation. In the survival animal series, the energy delivered ranged from 31.5 to 48.3 Js (41.3±4.0, mean±s.d.) and the proportion of energy absorbed to energy delivered ranged from 44.2% to 64.7% (53.6%±4.5%). The foam validation results support the reliability of the energy absorption measure provided by the instrumented pendulum system. Given that a very substantial proportion of delivered energy passed--unabsorbed--through the specimens, the energy absorption measure provided by this novel technique arguably provides better characterization of injury severity than is provided simply by energy delivery.

Invasion-Flowback Processes During Hydraulic Fracturing Well Interference

NASA Astrophysics Data System (ADS)

Kenzhekhanov, Shaken; He, Kai; Xu, Liang; Lord, Paul; Lozano, Martin; Neeves, Keith; Yin, Xiaolong

2017-11-01

Drainage-imbibition cycles that simulate hydraulic fracturing fluid's invasion and flowback during well interference were investigated using NOA81 microfluidic micromodels. Well interference is quite common in unconventional oil and gas fields. It is not unusual for the fracturing fluid injected into a well to be discovered in a nearby well. Normally, the effect of such interference is considered to be negative, as fracturing fluid will be imbibed into the porous rock and block the flow path of hydrocarbons. However, field data show that some interferences are beneficial, and microfluidic experiments presented in this study show that surfactant in the fracturing fluid may be a reason for the observed positive interference. Two fluid drainage-imbibition cycles were conducted in micromodels. The first cycle simulates fracturing of the old well and the second cycle simulates fluid invasion from the new well into the old well's fracture network. The experimental data show that while most such interferences indeed can cause production loss, when the old well's fracturing fluid does not contain surfactant yet the new well's fracturing fluid does, interference can be positive, as the residual water saturation in the porous medium is effectively reduced by surfactants.

Estimation of Dry Fracture Weakness, Porosity, and Fluid Modulus Using Observable Seismic Reflection Data in a Gas-Bearing Reservoir

NASA Astrophysics Data System (ADS)

Chen, Huaizhen; Zhang, Guangzhi

2017-05-01

Fracture detection and fluid identification are important tasks for a fractured reservoir characterization. Our goal is to demonstrate a direct approach to utilize azimuthal seismic data to estimate fluid bulk modulus, porosity, and dry fracture weaknesses, which decreases the uncertainty of fluid identification. Combining Gassmann's (Vier. der Natur. Gesellschaft Zürich 96:1-23, 1951) equations and linear-slip model, we first establish new simplified expressions of stiffness parameters for a gas-bearing saturated fractured rock with low porosity and small fracture density, and then we derive a novel PP-wave reflection coefficient in terms of dry background rock properties (P-wave and S-wave moduli, and density), fracture (dry fracture weaknesses), porosity, and fluid (fluid bulk modulus). A Bayesian Markov chain Monte Carlo nonlinear inversion method is proposed to estimate fluid bulk modulus, porosity, and fracture weaknesses directly from azimuthal seismic data. The inversion method yields reasonable estimates in the case of synthetic data containing a moderate noise and stable results on real data.

Implications of interfacial characteristics of food foaming agents in foam formulations.

PubMed

Rodríguez Patino, Juan M; Carrera Sánchez, Cecilio; Rodríguez Niño, Ma Rosario

2008-08-05

The manufacture of food dispersions (emulsions and foams) with specific quality attributes depends on the selection of the most appropriate raw materials and processing conditions. These dispersions being thermodynamically unstable require the use of emulsifiers (proteins, lipids, phospholipids, surfactants etc.). Emulsifiers typically coexist in the interfacial layer with specific functions in the processing and properties of the final product. The optimum use of emulsifiers depends on our knowledge of their interfacial physico-chemical characteristics - such as surface activity, amount adsorbed, structure, thickness, topography, ability to desorb (stability), lateral mobility, interactions between adsorbed molecules, ability to change conformation, interfacial rheological properties, etc. -, the kinetics of film formation and other associated physico-chemical properties at fluid interfaces. These monolayers constitute well defined systems for the analysis of food colloids at the micro- and nano-scale level, with several advantages for fundamental studies. In the present review we are concerned with the analysis of physico-chemical properties of emulsifier films at fluid interfaces in relation to foaming. Information about the above properties would be very helpful in the prediction of optimised formulations for food foams. We concluded that at surface pressures lower than that of monolayer saturation the foaming capacity is low, or even zero. A close relationship was observed between foaming capacity and the rate of diffusion of the foaming agent to the air-water interface. However, the foam stability correlates with the properties of the film at long-term adsorption.

Assessments of low emission asphalt mixtures produced using combinations of foaming agents

NASA Astrophysics Data System (ADS)

Mohd Hasan, Mohd Rosli

The asphalt foaming techniques have been used over the last couple of decades as an alternative to the traditional method of preparing asphalt mixtures. Based on positive feedback from the industry, this study was initiated to explore and evaluate the performance of the Warm Mix Asphalt (WMA) mixture produced through a foaming process using physical and chemical foaming agents, which are ethanol and sodium bicarbonate (NaHCO3), respectively. The success of this project may lead to new theories and provide an environmentally friendly technique to produce asphalt mixtures. This may advance the understanding of the foaming process and improve the performance of WMA to support sustainable development. Theoretically, ethanol can function in the same manner as water but requires less energy to foam due to its lower boiling point, 78°C. During the asphalt foaming process, numerous bubbles were generated by the vaporized ethanol, which significantly increased the volume of the asphalt binder, hence the coating potential of aggregates improves. The sodium bicarbonate was incorporated to enhance the quantity of bubbles and its stability. Therefore, understanding foaming agents, their solubility, chemical reactions, chemical function groups and rheological properties of the foamed binder are essential to help control the foam structure and final properties of the foamed WMA mixture. In order to understand the overall performance of newly developed foaming WMA, this material was evaluated for moisture susceptibility, rutting potential, and resistance to fracture and thermal cracking. The coatability, workability and compactability of foamed asphalt mixtures during production were also evaluated. Based on the results, it was found that the newly proposed foaming WMA has high potential to promote sustainable development by lowering the energy consumption and impacts on the environment. The ethanol is efficient in lowering the viscosity of asphalt binders, enhancing the workability, and having a higher expulsion rate from the foamed binder compared to water as a foaming agent. The addition of foaming agents to the asphalt binder has also lowered the activation energy of the asphalt binder, which has high potential in lowering the energy demand during production processes. The foamed WMA mixture prepared at 100°C was found to have behavior comparable with the control Hot Mix Asphalt (HMA) prepared at 155°C in terms of coatability, workability and compactability. Based on the mixture performance tests, the foamed WMA has a comparable or better performance than the HMA in terms of resistance to moisture damage, permanent deformation, fracture cracking and thermal cracking. The application of nano-hydrated lime is efficient in enhancing the aggregate coatability and improving the bearing capacity of asphalt pavement to lower the rutting potential and moisture susceptibility of foamed WMA mixtures. Limitations for each of the related parameters are also reported in this dissertation for the lab production of foamed WMA mixtures using ethanol and NaHCO 3 as foaming agents. The specified values were made based on the binder test, service characteristics and performance of foamed WMA mixtures in order to yield a comparable or better performance than the control HMA. Field validations should be carried out to understand the overall performance and durability of the proposed foaming WMA.

Group invariant solution for a pre-existing fluid-driven fracture in impermeable rock

NASA Astrophysics Data System (ADS)

Fitt, A. D.; Mason, D. P.; Moss, E. A.

2007-11-01

The propagation of a two-dimensional fluid-driven fracture in impermeable rock is considered. The fluid flow in the fracture is laminar. By applying lubrication theory a partial differential equation relating the half-width of the fracture to the fluid pressure is derived. To close the model the PKN formulation is adopted in which the fluid pressure is proportional to the half-width of the fracture. By considering a linear combination of the Lie point symmetries of the resulting non-linear diffusion equation the boundary value problem is expressed in a form appropriate for a similarity solution. The boundary value problem is reformulated as two initial value problems which are readily solved numerically. The similarity solution describes a preexisting fracture since both the total volume and length of the fracture are initially finite and non-zero. Applications in which the rate of fluid injection into the fracture and the pressure at the fracture entry are independent of time are considered.

Polyurethane foam pica in a patient with excessive interdialytic weight gain

PubMed Central

Iyasere, Osasuyi; Allington, Ying; Cafferkey, Michele

2010-01-01

Maintaining fluid balance in haemodialysis patients is important because of the adverse effects of excessive interdialytic weight gain. This often requires fluid restriction that patients often struggle with. We report a case of a 31-year-old female diabetic patient on haemodialysis with repeated excessive interdialytic weight gains despite fluid restriction and dry weight adjustment. It was subsequently discovered that she devised an unusual, albeit unsuccessful, strategy of eating the polyurethane foam from her dialysis chair while increasing her fluid intake hoping that it would absorb excess water in the gut! This under-diagnosed phenomenon known as pica has been reported in renal patients with substances such as ice, clay and baking soda. PMID:22767521

Fabrication of Aluminum Foam-Filled Thin-Wall Steel Tube by Friction Welding and Its Compression Properties

PubMed Central

Hangai, Yoshihiko; Saito, Masaki; Utsunomiya, Takao; Kitahara, Soichiro; Kuwazuru, Osamu; Yoshikawa, Nobuhiro

2014-01-01

Aluminum foam has received considerable attention in various fields and is expected to be used as an engineering material owing to its high energy absorption properties and light weight. To improve the mechanical properties of aluminum foam, combining it with dense tubes, such as aluminum foam-filled tubes, was considered necessary. In this study, an aluminum foam-filled steel tube, which consisted of ADC12 aluminum foam and a thin-wall steel tube, was successfully fabricated by friction welding. It was shown that a diffusion bonding layer with a thickness of approximately 10 μm was formed, indicating that strong bonding between the aluminum foam and the steel tube was realized. By the X-ray computed tomography observation of pore structures, the fabrication of an aluminum foam-filled tube with almost uniform pore structures over the entire specimen was confirmed. In addition, it was confirmed that the aluminum foam-filled steel tube exhibited mechanical properties superior to those of the ADC12 aluminum foam and steel tube. This is considered to be attributed to the combination of the aluminum foam and steel tube, which particularly prevents the brittle fracture and collapse of the ADC12 foam by the steel tube, along with the strong metal bonding between the aluminum foam and the steel tube. PMID:28788213

Preventing fall-related vertebral fractures: effect of floor stiffness on peak impact forces during backward falls.

PubMed

Sran, Meena M; Robinovitch, Stephen N

2008-08-01

In vivo biomechanical study of 11 male volunteers. To measure the peak forces applied to the buttocks in a backward fall from standing, and to determine whether this force is lowered by reductions in floor stiffness. Fall-related vertebral fractures are common and backward falls result in impact to the buttocks. Compliant flooring may reduce impact force and risk for vertebral fracture during a fall. However, we have little knowledge of the peak forces applied to the body during a backward fall, or how floor stiffness affects this force. Eleven males, mean age 25 +/- 5 (SD) years, were suddenly released from a backward lean of 15 degrees , falling backward onto the ground which was covered with 4.5, 7.5, or 10.5 cm of ethylene vinyl acetate foam rubber. We measured 3-dimensional impact forces applied to the buttocks at 960 Hz with a force plate. We used repeated measures analysis of variance and post hoc t tests to compare peak forces between conditions. We also modeled peak vertical force for falls onto a bare floor. RESULTS.: There was a significant difference in peak vertical force between falls onto the 10.5 cm foam condition compared with the 7.5 cm (P = 0.002) and 4.5 cm (P < 0.001) conditions. Peak vertical force (N) was (mean +/- SD) 5099 +/- 868, 4788 +/- 702, and 4544 +/- 672 for the 4.5, 7.5, and 10.5 cm foam conditions, respectively, and estimated at 6027 +/- 988 for the rigid (bare floor) condition. Compared with the bare floor, these foam floors provided, on average, 24, 20, and 15% force attenuation respectively. In a backward fall onto the buttocks, peak impact forces are 6.4 to 9.0 times body weight in a fall onto a bare floor. Reducing floor stiffness using even a thin (4.5 cm) layer of foam may provide 15% vertical force attenuation during a fall onto the buttocks.

Destabilization, Propagation, and Generation of Surfactant-Stabilized Foam during Crude Oil Displacement in Heterogeneous Model Porous Media.

PubMed

Xiao, Siyang; Zeng, Yongchao; Vavra, Eric D; He, Peng; Puerto, Maura; Hirasaki, George J; Biswal, Sibani L

2018-01-23

Foam flooding in porous media is of increasing interest due to its numerous applications such as enhanced oil recovery, aquifer remediation, and hydraulic fracturing. However, the mechanisms of oil-foam interactions have yet to be fully understood at the pore level. Here, we present three characteristic zones identified in experiments involving the displacement of crude oil from model porous media via surfactant-stabilized foam, and we describe a series of pore-level dynamics in these zones which were not observed in experiments involving paraffin oil. In the displacement front zone, foam coalesces upon initial contact with crude oil, which is known to destabilize the liquid lamellae of the foam. Directly upstream, a transition zone occurs where surface wettability is altered from oil-wet to water-wet. After this transition takes place, a strong foam bank zone exists where foam is generated within the porous media. We visualized each zone using a microfluidic platform, and we discuss the unique physicochemical phenomena that define each zone. In our analysis, we also provide an updated mechanistic understanding of the "smart rheology" of foam which builds upon simple "phase separation" observations in the literature.

Effect of fluid penetration on tensile failure during fracturing of an open-hole wellbore

NASA Astrophysics Data System (ADS)

Zeng, Fanhui; Cheng, Xiaozhao; Guo, Jianchun; Chen, Zhangxin; Tao, Liang; Liu, Xiaohua; Jiang, Qifeng; Xiang, Jianhua

2018-06-01

It is widely accepted that a fracture can be induced at a wellbore surface when the fluid pressure overcomes the rock tensile strength. However, few models of this phenomenon account for the fluid penetration effect. A rock is a typical permeable, porous medium, and the transmission of pressure from a wellbore to the surrounding rock temporally and spatially perturbs the effective stresses. In addition, these induced stresses influence the fracture initiation pressure. To gain a better understanding of the penetration effect on the initiation pressure of a permeable formation, a comprehensive formula is presented to study the effects of the in situ stresses, rock mechanical properties, injection rate, rock permeability, fluid viscosity, fluid compressibility and wellbore size on the magnitude of the initiation pressure during fracturing of an open-hole wellbore. In this context, the penetration effect is treated as a consequence of the interaction among these parameters by using Darcy’s law of radial flow. A fully coupled analytical procedure is developed to show how the fracturing fluid infiltrates the rock around the wellbore and considerably reduces the magnitude of the initiation pressure. Moreover, the calculation results are validated by hydraulic fracturing experiments in hydrostone. An exhaustive sensitivity study is performed, indicating that the local fluid pressure induced from a seepage effect strongly influences the fracture evolution. For permeable reservoirs, a low injection rate and a low viscosity of the injected fluid have a significant impact on the fracture initiation pressure. In this case, the Hubbert and Haimson equations to predict the fracture initiation pressure are not valid. The open-hole fracture initiation pressure increases with the fracturing fluid viscosity and fluid compressibility, while it decreases as the rock permeability, injection rate and wellbore size increase.

Effect of rock rheology on fluid leak- off during hydraulic fracturing

NASA Astrophysics Data System (ADS)

Yarushina, V. M.; Bercovici, D.; Oristaglio, M. L.

2012-04-01

In this communication, we evaluate the effect of rock rheology on fluid leak­off during hydraulic fracturing of reservoirs. Fluid leak-off in hydraulic fracturing is often nonlinear. The simple linear model developed by Carter (1957) for flow of fracturing fluid into a reservoir has three different regions in the fractured zone: a filter cake on the fracture face, formed by solid additives from the fracturing fluid; a filtrate zone affected by invasion of the fracturing fluid; and a reservoir zone with the original formation fluid. The width of each zone, as well as its permeability and pressure drop, is assumed to remain constant. Physical intuition suggests some straightforward corrections to this classical theory to take into account the pressure dependence of permeability, the compressibility or non-Newtonian rheology of fracturing fluid, and the radial (versus linear) geometry of fluid leak­off from the borehole. All of these refinements, however, still assume that the reservoir rock adjacent to the fracture face is non­deformable. Although the effect of poroelastic stress changes on leak-off is usually thought to be negligible, at the very high fluid pressures used in hydraulic fracturing, where the stresses exceed the rock strength, elastic rheology may not be the best choice. For example, calculations show that perfectly elastic rock formations do not undergo the degree of compaction typically seen in sedimentary basins. Therefore, pseudo-elastic or elastoplastic models are used to fit observed porosity profiles with depth. Starting from balance equations for mass and momentum for fluid and rock, we derive a hydraulic flow equation coupled with a porosity equation describing rock compaction. The result resembles a pressure diffusion equation with the total compressibility being a sum of fluid, rock and pore-space compressibilities. With linear elastic rheology, the bulk formation compressibility is dominated by fluid compressibility. But the possibility of permanent, time-independent (plastic) rock deformation significantly increases the pore space compressibility (compaction), which becomes a leading term in the total compressibility. Inclusion of rock and fluid compressibilities in the model can explain both linear and nonlinear leak­off. In particular, inclusion of rock compaction and decompaction may be important for description of naturally fractured and tight gas reservoirs for which very strong dependence of permeability on porosity has been reported. Carter R.D. Derivation of the general equation for estimating the extent of the fractured area. Appendix I of "Optimum fluid characteristics for fracture extension", Drilling and Production Practice, G.C. Howard and C.R.Fast, New York, New York, USA, American Petroleum Institute (1957), 261-269.

Influence of mechanical rock properties and fracture healing rate on crustal fluid flow dynamics

NASA Astrophysics Data System (ADS)

Sachau, Till; Bons, Paul; Gomez-Rivas, Enrique; Koehn, Daniel; de Riese, Tamara

2016-04-01

Fluid flow in the Earth's crust is very slow over extended periods of time, during which it occurs within the connected pore space of rocks. If the fluid production rate exceeds a certain threshold, matrix permeability alone is insufficient to drain the fluid volume and fluid pressure builds up, thereby reducing the effective stress supported by the rock matrix. Hydraulic fractures form once the effective pressure exceeds the tensile strength of the rock matrix and act subsequently as highly effective fluid conduits. Once local fluid pressure is sufficiently low again, flow ceases and fractures begin to heal. Since fluid flow is controlled by the alternation of fracture permeability and matrix permeability, the flow rate in the system is strongly discontinuous and occurs in intermittent pulses. Resulting hydraulic fracture networks are largely self-organized: opening and subsequent healing of hydraulic fractures depends on the local fluid pressure and on the time-span between fluid pulses. We simulate this process with a computer model and describe the resulting dynamics statistically. Special interest is given to a) the spatially and temporally discontinuous formation and closure of fractures and fracture networks and b) the total flow rate over time. The computer model consists of a crustal-scale dual-porosity setup. Control parameters are the pressure- and time-dependent fracture healing rate, and the strength and the permeability of the intact rock. Statistical analysis involves determination of the multifractal properties and of the power spectral density of the temporal development of the total drainage rate and hydraulic fractures. References Bons, P. D. (2001). The formation of large quartz veins by rapid ascent of fluids in mobile hydrofractures. Tectonophysics, 336, 1-17. Miller, S. a., & Nur, A. (2000). Permeability as a toggle switch in fluid-controlled crustal processes. Earth and Planetary Science Letters, 183(1-2), 133-146. Sachau, T., Bons, P. D., & Gomez-Rivas, E. (2015). Transport efficiency and dynamics of hydraulic fracture networks. Frontiers in Physics, 3.

Re-injection feasibility study of fracturing flow-back fluid in shale gas mining

NASA Astrophysics Data System (ADS)

Kang, Dingyu; Xue, Chen; Chen, Xinjian; Du, Jiajia; Shi, Shengwei; Qu, Chengtun; Yu, Tao

2018-02-01

Fracturing flow-back fluid in shale gas mining is usually treated by re-injecting into formation. After treatment, the fracturing flow-back fluid is injected back into the formation. In order to ensure that it will not cause too much damage to the bottom layer, feasibility evaluations of re-injection of two kinds of fracturing fluid with different salinity were researched. The experimental research of the compatibility of mixed water samples based on the static simulation method was conducted. Through the analysis of ion concentration, the amount of scale buildup and clay swelling rate, the feasibility of re-injection of different fracturing fluid were studied. The result shows that the swelling of the clay expansion rate of treated fracturing fluid is lower than the mixed water of treated fracturing fluid and the distilled water, indicating that in terms of clay expansion rate, the treated fracturing flow-back fluid is better than that of water injection after re-injection. In the compatibility test, the maximum amount of fouling in the Yangzhou oilfield is 12mg/L, and the maximum value of calcium loss rate is 1.47%, indicating that the compatibility is good. For the fracturing fluid with high salinity in the Yanchang oilfield, the maximum amount of scaling is 72mg/L, and the maximum calcium loss rate is 3.50%, indicating that the compatibility is better.

Strengthening of phosphate ceramic foam by silicon carbide whiskers

NASA Technical Reports Server (NTRS)

Schetanov, B. V.; Prilepskiy, V. N.; Lapidovskaya, L. A.; Chernyak, A. I.; Romanovich, I. V.

1987-01-01

The influence of additions of SiC whiskers on the elastic modulus and flexural strength of phosphate ceramic foam is assessed. It is shown that the incorporation into the material composition of even small amounts (2.4 vol%) of SiC whiskers enhances the impact toughness and heat resistance of the ceramic foam. A 12.3 vol% of SiC whiskers leads to a more than threefold increase of the flexural strength. Strengthening of the phosphate ceramic foam is due to the fact that the whiskers hinder the propagation of matrix crack by increasing the work of matrix fracture. The whiskers reinforce only that volume of material which is occupied by solid matter, whereas they do not reinforce the pores.

Electrophilic acid gas-reactive fluid, proppant, and process for enhanced fracturing and recovery of energy producing materials

DOEpatents

Fernandez, Carlos A.; Heldebrant, David J.; Bonneville, Alain H. R.; Jung, Hun Bok; Carroll, Kenneth

2016-09-20

An electrophilic acid gas-reactive fracturing and recovery fluid, proppant, and process are detailed. The fluid expands in volume to provide rapid and controlled increases in pressure that enhances fracturing in subterranean bedrock for recovery of energy-producing materials. Proppants stabilize openings in fractures and fissures following fracturing.

Fluid identification based on P-wave anisotropy dispersion gradient inversion for fractured reservoirs

NASA Astrophysics Data System (ADS)

Zhang, J. W.; Huang, H. D.; Zhu, B. H.; Liao, W.

2017-10-01

Fluid identification in fractured reservoirs is a challenging issue and has drawn increasing attentions. As aligned fractures in subsurface formations can induce anisotropy, we must choose parameters independent with azimuths to characterize fractures and fluid effects such as anisotropy parameters for fractured reservoirs. Anisotropy is often frequency dependent due to wave-induced fluid flow between pores and fractures. This property is conducive for identifying fluid type using azimuthal seismic data in fractured reservoirs. Through the numerical simulation based on Chapman model, we choose the P-wave anisotropy parameter dispersion gradient (PADG) as the new fluid factor. PADG is dependent both on average fracture radius and fluid type but independent on azimuths. When the aligned fractures in the reservoir are meter-scaled, gas-bearing layer could be accurately identified using PADG attribute. The reflection coefficient formula for horizontal transverse isotropy media by Rüger is reformulated and simplified according to frequency and the target function for inverting PADG based on frequency-dependent amplitude versus azimuth is derived. A spectral decomposition method combining Orthogonal Matching Pursuit and Wigner-Ville distribution is used to prepare the frequency-division data. Through application to synthetic data and real seismic data, the results suggest that the method is useful for gas identification in reservoirs with meter-scaled fractures using high-qualified seismic data.

Air contamination in the sclerosing foam for the treatment of varicose veins.

PubMed

de Franciscis, S; Nobile, Cga; Larosa, E; Montemurro, R; Serra, R

2016-03-01

Fluids and drugs formulated for intravenous infusion may potentially promote the growth of microorganisms that can cause infections. The aim of this study is to test the sterility of sclerosing foam. Polidocanol was used for the production of the foam. The Tessari method was used in order to generate the foam. The preparation was carried out both in the operating theater and in an outpatient room. A validation test with microorganisms was also performed. The measurements showed no evident growth of microorganisms and in the validation tests the foam appeared to even display bacteriostatic and/or bactericide properties. Sclerosing foam seems to be safe from a microbiological point of view. © The Author(s) 2014.

Fluid-phase pinocytosis of LDL by macrophages: a novel target to reduce macrophage cholesterol accumulation in atherosclerotic lesions.

PubMed

Kruth, Howar S

2013-01-01

Circulating low-density lipoprotein (LDL) that enters the blood vessel wall is the main source of cholesterol that accumulates within atherosclerotic plaques. Much of the deposited cholesterol accumulates within plaque macrophages converting these macrophages into cholesterol-rich foamy looking cells. Cholesterol accumulation in macrophages contributes to cholesterol retention within the vessel wall, and promotes vessel wall inflammation and thrombogenicity. Thus, how macrophages accumulate cholesterol and become foam cells has been the subject of intense investigation. It is generally believed that macrophages accumulate cholesterol only through scavenger receptor-mediated uptake of modified LDL. However, an alternative mechanism for macrophage foam cell formation that does not depend on LDL modification or macrophage receptors has been elucidated. By this alternative mechanism, macrophages show receptor-independent uptake of unmodified native LDL that is mediated by fluid-phase pinocytosis. In receptor-independent, fluid-phase pinocytosis, macrophages take up LDL as part of the fluid that they ingest during micropinocytosis within small vesicles called micropinosomes, and by macropinocytosis within larger vacuoles called macropinosomes. This produces cholesterol accumulation in macrophages to levels characteristic of macrophage foam cells in atherosclerotic plaques. Fluid-phase pinocytosis of LDL is a plausible mechanism that can explain how macrophages accumulate cholesterol and become disease-causing foam cells. Fluid-phase pinocytosis of LDL is a relevant pathway to target for modulating macrophage cholesterol accumulation in atherosclerosis. Recent studies show that phosphoinositide 3-kinase (PI3K), liver X receptors (LXRs), the macrophage colony-stimulating factor (M-CSF) receptor, and protein kinase C (PKC) mediate macrophage macropinocytosis of LDL, and thus, these may be relevant targets to inhibit macrophage cholesterol accumulation in atherosclerosis.

Design and Implementation of Energized Fracture Treatment in Tight Gas Sands

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukul Sharma; Kyle Friehauf

2009-12-31

Hydraulic fracturing is essential for producing gas and oil at an economic rate from low permeability sands. Most fracturing treatments use water and polymers with a gelling agent as a fracturing fluid. The water is held in the small pore spaces by capillary pressure and is not recovered when drawdown pressures are low. The un-recovered water leaves a water saturated zone around the fracture face that stops the flow of gas into the fracture. This is a particularly acute problem in low permeability formations where capillary pressures are high. Depletion (lower reservoir pressures) causes a limitation on the drawdown pressuremore » that can be applied. A hydraulic fracturing process can be energized by the addition of a compressible, sometimes soluble, gas phase into the treatment fluid. When the well is produced, the energized fluid expands and gas comes out of solution. Energizing the fluid creates high gas saturation in the invaded zone, thereby facilitating gas flowback. A new compositional hydraulic fracturing model has been created (EFRAC). This is the first model to include changes in composition, temperature, and phase behavior of the fluid inside the fracture. An equation of state is used to evaluate the phase behavior of the fluid. These compositional effects are coupled with the fluid rheology, proppant transport, and mechanics of fracture growth to create a general model for fracture creation when energized fluids are used. In addition to the fracture propagation model, we have also introduced another new model for hydraulically fractured well productivity. This is the first and only model that takes into account both finite fracture conductivity and damage in the invaded zone in a simple analytical way. EFRAC was successfully used to simulate several fracture treatments in a gas field in South Texas. Based on production estimates, energized fluids may be required when drawdown pressures are smaller than the capillary forces in the formation. For this field, the minimum CO{sub 2} gas quality (volume % of gas) recommended is 30% for moderate differences between fracture and reservoir pressures (2900 psi reservoir, 5300 psi fracture). The minimum quality is reduced to 20% when the difference between pressures is larger, resulting in additional gas expansion in the invaded zone. Inlet fluid temperature, flow rate, and base viscosity did not have a large impact on fracture production. Finally, every stage of the fracturing treatment should be energized with a gas component to ensure high gas saturation in the invaded zone. A second, more general, sensitivity study was conducted. Simulations show that CO{sub 2} outperforms N{sub 2} as a fluid component because it has higher solubility in water at fracturing temperatures and pressures. In fact, all gas components with higher solubility in water will increase the fluid's ability to reduce damage in the invaded zone. Adding methanol to the fracturing solution can increase the solubility of CO{sub 2}. N{sub 2} should only be used if the gas leaks-off either during the creation of the fracture or during closure, resulting in gas going into the invaded zone. Experimental data is needed to determine if the gas phase leaks-off during the creation of the fracture. Simulations show that the bubbles in a fluid traveling across the face of a porous medium are not likely to attach to the surface of the rock, the filter cake, or penetrate far into the porous medium. In summary, this research has created the first compositional fracturing simulator, a useful tool to aid in energized fracture design. We have made several important and original conclusions about the best practices when using energized fluids in tight gas sands. The models and tools presented here may be used in the future to predict behavior of any multi-phase or multi-component fracturing fluid system.« less

Application of foam-extend on turbulent fluid-structure interaction

NASA Astrophysics Data System (ADS)

Rege, K.; Hjertager, B. H.

2017-12-01

Turbulent flow around flexible structures is likely to induce structural vibrations which may eventually lead to fatigue failure. In order to assess the fatigue life of these structures, it is necessary to take the action of the flow on the structure into account, but also the influence of the vibrating structure on the fluid flow. This is achieved by performing fluid-structure interaction (FSI) simulations. In this work, we have investigated the capability of a FSI toolkit for the finite volume computational fluid dynamics software foam-extend to simulate turbulence-induced vibrations of a flexible structure. A large-eddy simulation (LES) turbulence model has been implemented to a basic FSI problem of a flexible wall which is placed in a confined, turbulent flow. This problem was simulated for 2.32 seconds. This short simulation required over 200 computation hours, using 20 processor cores. Thereby, it has been shown that the simulation of FSI with LES is possible, but also computationally demanding. In order to make turbulent FSI simulations with foam-extend more applicable, more sophisticated turbulence models and/or faster FSI iteration schemes should be applied.

Rheological and Performance Research on a Regenerable Polyvinyl Alcohol Fracturing Fluid

PubMed Central

Shang, Xiaosen; Ding, Yunhong; Wang, Yonghui; Yang, Lifeng

2015-01-01

A regenerable polyvinyl alcohol/organic boron fracturing fluid system with 1.6 wt% polyvinyl alcohol (PVOH) and 1.2 wt% organic boron (OBT) was studied, and its main regeneration mechanism is the reversible cross-linking reaction between B(OH)4 - and hydroxyl groups of PVOH as the change of pH. Results of rheology evaluations show that both the apparent viscosity and the thermal stability of the fracturing fluid decreased with the regeneration number of times increasing. In addition, the apparent viscosity of the fluid which was without regeneration was more sensitive to the shear action compared with that of the fluid with regeneration once or twice. When the fracturing fluid was without regeneration, the elasticity was dominating due to the three-dimensional network structure of the formed gel; the viscosity gradually occupied the advantage when the fracturing fluid was regenerated once or twice. The settling velocity of proppant was accelerated by both the regeneration process and the increasing temperature, but it was decelerated when the proppant ratio increased. Results of core damage tests indicate that less permeability damage was caused by the PVOH/OBT fracturing fluid compared with that caused by the guar gum fracturing fluid after gel breaking. PMID:26641857

Rheological and Performance Research on a Regenerable Polyvinyl Alcohol Fracturing Fluid.

PubMed

Shang, Xiaosen; Ding, Yunhong; Wang, Yonghui; Yang, Lifeng

2015-01-01

A regenerable polyvinyl alcohol/organic boron fracturing fluid system with 1.6 wt% polyvinyl alcohol (PVOH) and 1.2 wt% organic boron (OBT) was studied, and its main regeneration mechanism is the reversible cross-linking reaction between B(OH)4- and hydroxyl groups of PVOH as the change of pH. Results of rheology evaluations show that both the apparent viscosity and the thermal stability of the fracturing fluid decreased with the regeneration number of times increasing. In addition, the apparent viscosity of the fluid which was without regeneration was more sensitive to the shear action compared with that of the fluid with regeneration once or twice. When the fracturing fluid was without regeneration, the elasticity was dominating due to the three-dimensional network structure of the formed gel; the viscosity gradually occupied the advantage when the fracturing fluid was regenerated once or twice. The settling velocity of proppant was accelerated by both the regeneration process and the increasing temperature, but it was decelerated when the proppant ratio increased. Results of core damage tests indicate that less permeability damage was caused by the PVOH/OBT fracturing fluid compared with that caused by the guar gum fracturing fluid after gel breaking.

SedFoam-2.0: a 3-D two-phase flow numerical model for sediment transport

NASA Astrophysics Data System (ADS)

Chauchat, Julien; Cheng, Zhen; Nagel, Tim; Bonamy, Cyrille; Hsu, Tian-Jian

2017-11-01

In this paper, a three-dimensional two-phase flow solver, SedFoam-2.0, is presented for sediment transport applications. The solver is extended from twoPhaseEulerFoam available in the 2.1.0 release of the open-source CFD (computational fluid dynamics) toolbox OpenFOAM. In this approach the sediment phase is modeled as a continuum, and constitutive laws have to be prescribed for the sediment stresses. In the proposed solver, two different intergranular stress models are implemented: the kinetic theory of granular flows and the dense granular flow rheology μ(I). For the fluid stress, laminar or turbulent flow regimes can be simulated and three different turbulence models are available for sediment transport: a simple mixing length model (one-dimensional configuration only), a k - ɛ, and a k - ω model. The numerical implementation is demonstrated on four test cases: sedimentation of suspended particles, laminar bed load, sheet flow, and scour at an apron. These test cases illustrate the capabilities of SedFoam-2.0 to deal with complex turbulent sediment transport problems with different combinations of intergranular stress and turbulence models.

Hydraulic Fracturing Fluid Analysis for Regulatory Parameters - A Progress Report

EPA Pesticide Factsheets

This presentation is a progress report on the analysis of Hydraulic Fracturing Fluids for regulatory compounds outlined in the various US EPA methodologies. Fracturing fluids vary significantly in consistency and viscosity prior to fracturing. Due to the nature of the fluids the analytical challenges will have to be addressed. This presentation also outlines the sampling issues associated with the collection of dissolved gas samples.

Phase field model of fluid-driven fracture in elastic media: Immersed-fracture formulation and validation with analytical solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Santillán, David; Juanes, Ruben; Cueto-Felgueroso, Luis

Propagation of fluid-driven fractures plays an important role in natural and engineering processes, including transport of magma in the lithosphere, geologic sequestration of carbon dioxide, and oil and gas recovery from low-permeability formations, among many others. The simulation of fracture propagation poses a computational challenge as a result of the complex physics of fracture and the need to capture disparate length scales. Phase field models represent fractures as a diffuse interface and enjoy the advantage that fracture nucleation, propagation, branching, or twisting can be simulated without ad hoc computational strategies like remeshing or local enrichment of the solution space. Heremore » we propose a new quasi-static phase field formulation for modeling fluid-driven fracturing in elastic media at small strains. The approach fully couples the fluid flow in the fracture (described via the Reynolds lubrication approximation) and the deformation of the surrounding medium. The flow is solved on a lower dimensionality mesh immersed in the elastic medium. This approach leads to accurate coupling of both physics. We assessed the performance of the model extensively by comparing results for the evolution of fracture length, aperture, and fracture fluid pressure against analytical solutions under different fracture propagation regimes. Thus, the excellent performance of the numerical model in all regimes builds confidence in the applicability of phase field approaches to simulate fluid-driven fracture.« less

Phase field model of fluid-driven fracture in elastic media: Immersed-fracture formulation and validation with analytical solutions

DOE PAGES

Santillán, David; Juanes, Ruben; Cueto-Felgueroso, Luis

2017-04-20

Propagation of fluid-driven fractures plays an important role in natural and engineering processes, including transport of magma in the lithosphere, geologic sequestration of carbon dioxide, and oil and gas recovery from low-permeability formations, among many others. The simulation of fracture propagation poses a computational challenge as a result of the complex physics of fracture and the need to capture disparate length scales. Phase field models represent fractures as a diffuse interface and enjoy the advantage that fracture nucleation, propagation, branching, or twisting can be simulated without ad hoc computational strategies like remeshing or local enrichment of the solution space. Heremore » we propose a new quasi-static phase field formulation for modeling fluid-driven fracturing in elastic media at small strains. The approach fully couples the fluid flow in the fracture (described via the Reynolds lubrication approximation) and the deformation of the surrounding medium. The flow is solved on a lower dimensionality mesh immersed in the elastic medium. This approach leads to accurate coupling of both physics. We assessed the performance of the model extensively by comparing results for the evolution of fracture length, aperture, and fracture fluid pressure against analytical solutions under different fracture propagation regimes. Thus, the excellent performance of the numerical model in all regimes builds confidence in the applicability of phase field approaches to simulate fluid-driven fracture.« less

Stimuli-Responsive/Rheoreversible Hydraulic Fracturing Fluids as a Greener Alternative to Support Geothermal and Fossil Energy Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jung, Hun Bok; Carroll, KC; Kabilan, Senthil

2015-01-01

Cost-effective yet safe creation of high-permeability reservoirs within deep bedrock is the primary challenge for the viability of enhanced geothermal systems (EGS) and unconventional oil/gas recovery. Although fracturing fluids are commonly used for oil/gas, standard fracturing methods are not developed or proven for EGS temperatures and pressures. Furthermore, the environmental impacts of currently used fracturing methods are only recently being determined. Widespread concerns about the environmental contamination have resulted in a number of regulations for fracturing fluids advocating for greener fracturing processes. To enable EGS feasibility and lessen environmental impact of reservoir stimulation, an environmentally benign, CO2-activated, rheoreversible fracturing fluidmore » that enhances permeability through fracturing (at significantly lower effective stress than standard fracturing fluids) due to in situ volume expansion and gel formation is investigated herein. The chemical mechanism, stability, phase-change behavior, and rheology for a novel polyallylamine (PAA)-CO2 fracturing fluid was characterized at EGS temperatures and pressures. Hydrogel is formed upon reaction with CO2 and this process is reversible (via CO2 depressurization or solubilizing with a mild acid) allowing removal from the formation and recycling, decreasing environmental impact. Rock obtained from the Coso geothermal field was fractured in laboratory experiments under various EGS temperatures and pressures with comparison to standard fracturing fluids, and the fractures were characterized with imaging, permeability measurement, and flow modeling. This novel fracturing fluid and process may vastly reduce water usage and the environmental impact of fracturing practices and effectively make EGS production and unconventional oil/gas exploitation cost-effective and cleaner.« less

The Mechanical Strength of Si Foams in the Mushy Zone during Solidification of Al–Si Alloys

PubMed Central

Lim, Jeon Taik; Youn, Ji Won; Seo, Seok Yong; Kim, Ki Young; Kim, Suk Jun

2017-01-01

The mechanical strength of an Al-30% Si alloy in the mushy zone was estimated by using a novel centrifugation apparatus. In the apparatus, the alloy melt was partially solidified, forming a porous structure made of primary Si platelets (Si foam) while cooling. Subsequently, pressure generated by centrifugal force pushed the liquid phase out of the foam. The estimated mechanical strength of the Si foam in the temperature range 850–993 K was very low (62 kPa to 81 kPa). This is about two orders of magnitude lower than the mechanical strength at room temperature as measured by compressive tests. When the centrifugal stress was higher than the mechanical strength of the foam, the foam fractured, and the primary Si crystallites were extracted along with the Al-rich melt. Therefore, to maximize the centrifugal separation efficiency of the Al-30% Si alloy, the centrifugal stress should be in the range of 62–81 kPa. PMID:28772695

Application of Video Image Correlation Techniques to the Space Shuttle External Tank Foam Materials

NASA Technical Reports Server (NTRS)

Hilburger, Mark W.; Nemeth, Michael P.

2005-01-01

Results that illustrate the use of a video-image-correlation-based displacement and strain measurement system to assess the effects of material nonuniformities on the behavior of the sprayed-on foam insulation (SOFI) used for the thermal protection system on the Space Shuttle External Tank are presented. Standard structural verification specimens for the SOFI material with and without cracks and subjected to mechanical or thermal loading conditions were tested. Measured full-field displacements and strains are presented for selected loading conditions to illustrate the behavior of the foam and the viability of the measurement technology. The results indicate that significant strain localization can occur in the foam because of material nonuniformities. In particular, elongated cells in the foam can interact with other geometric or material discontinuities in the foam and develop large-magnitude localized strain concentrations that likely initiate failures. Furthermore, some of the results suggest that continuum mechanics and linear elastic fracture mechanics might not adequately represent the physical behavior of the foam, and failure predictions based on homogeneous linear material models are likely to be inadequate.

Application of Video Image Correlation Techniques to the Space Shuttle External Tank Foam Materials

NASA Technical Reports Server (NTRS)

Hilburger, Mark W.; Nemeth, Michael P.

2006-01-01

Results that illustrate the use of a video-image-correlation-based displacement and strain measurement system to assess the effects of material nonuniformities on the behavior of the sprayed-on foam insulation (SOFI) used for the thermal protection system on the Space Shuttle External Tank are presented. Standard structural verification specimens for the SOFI material with and without cracks and subjected to mechanical or thermal loading conditions were tested. Measured full-field displacements and strains are presented for selected loading conditions to illustrate the behavior of the foam and the viability of the measurement technology. The results indicate that significant strain localization can occur in the foam because of material nonuniformities. In particular, elongated cells in the foam can interact with other geometric or material discontinuities in the foam and develop large-magnitude localized strain concentrations that likely initiate failures. Furthermore, some of the results suggest that continuum mechanics and linear elastic fracture mechanics might not adequately represent the physical behavior of the foam, and failure predictions based on homogeneous linear material models are likely to be inadequate.

Electrophoretic deposition of mesoporous bioactive glass on glass-ceramic foam scaffolds for bone tissue engineering.

PubMed

Fiorilli, Sonia; Baino, Francesco; Cauda, Valentina; Crepaldi, Marco; Vitale-Brovarone, Chiara; Demarchi, Danilo; Onida, Barbara

2015-01-01

In this work, the coating of 3-D foam-like glass-ceramic scaffolds with a bioactive mesoporous glass (MBG) was investigated. The starting scaffolds, based on a non-commercial silicate glass, were fabricated by the polymer sponge replica technique followed by sintering; then, electrophoretic deposition (EPD) was applied to deposit a MBG layer on the scaffold struts. EPD was also compared with other techniques (dipping and direct in situ gelation) and it was shown to lead to the most promising results. The scaffold pore structure was maintained after the MBG coating by EPD, as assessed by SEM and micro-CT. In vitro bioactivity of the scaffolds was assessed by immersion in simulated body fluid and subsequent evaluation of hydroxyapatite (HA) formation. The deposition of a MBG coating can be a smart strategy to impart bioactive properties to the scaffold, allowing the formation of nano-structured HA agglomerates within 48 h from immersion, which does not occur on uncoated scaffold surfaces. The mechanical properties of the scaffold do not vary after the EPD (compressive strength ~19 MPa, fracture energy ~1.2 × 10(6) J m(-3)) and suggest the suitability of the prepared highly bioactive constructs as bone tissue engineering implants for load-bearing applications.

Mathematical modeling and simulation analysis of hydraulic fracture propagation in three-layered poro-elastic media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moon, H.Y.; Advani, S.H.; Lee, T.S.

1992-11-01

Hydraulic fracturing plays a pivotal role in the enhancement of oil and gas production recovery from low permeability reservoirs. The process of hydraulic fracturing entails the generation of a fracture by pumping fluids blended with special chemicals and proppants into the payzone at high injection rates and pressures to extend and wedge fractures. The mathematical modeling of hydraulically induced fractures generally incorporates coupling between the formation elasticity, fracture fluid flow, and fracture mechanics equations governing the formation structural responses, fluid pressure profile, and fracture growth. Two allied unsymmetric elliptic fracture models are developed for fracture configuration evolutions in three-layered rockmore » formations. The first approach is based on a Lagrangian formulation incorporating pertinent energy components associated with the formation structural responses and fracture fluid flow. The second model is based on a generalized variational principle, introducing an energy rate related functional. These models initially simulate a penny-shaped fracture, which becomes elliptic if the crack tips encounters (upper and/or lower) barriers with differential reservoir properties (in situ stresses, 16 elastic moduli, and fracture toughness-contrasts and fluid leak-off characteristics). The energy rate component magnitudes are determined to interpret the governing hydraulic fracture mechanisms during fracture evolution. The variational principle is extended to study the phenomenon and consequences of fluid lag in fractures. Finally, parametric sensitivity and energy rate investigations to evaluate the roles of controllable hydraulic treatment variables and uncontrollable reservoir property characterization parameters are performed. The presented field applications demonstrate the overall capabilities of the developed models. These studies provide stimulation treatment guidelines for fracture configuration design, control, and optimization.« less

A review of aqueous foam in microscale.

PubMed

Anazadehsayed, Abdolhamid; Rezaee, Nastaran; Naser, Jamal; Nguyen, Anh V

2018-06-01

In recent years, significant progress has been achieved in the study of aqueous foams. Having said this, a better understanding of foam physics requires a deeper and profound study of foam elements. This paper reviews the studies in the microscale of aqueous foams. The elements of aqueous foams are interior Plateau borders, exterior Plateau borders, nodes, and films. Furthermore, these elements' contribution to the drainage of foam and hydraulic resistance are studied. The Marangoni phenomena that can happen in aqueous foams are listed as Marangoni recirculation in the transition region, Marangoni-driven flow from Plateau border towards the film in the foam fractionation process, and Marangoni flow caused by exposure of foam containing photosurfactants under UV. Then, the flow analysis of combined elements of foam such as PB-film along with Marangoni flow and PB-node are studied. Next, we contrast the behavior of foams in different conditions. These various conditions can be perturbation in the foam structure caused by injected water droplets or waves or using a non-Newtonian fluid to make the foam. Further review is about the effect of oil droplets and particles on the characteristics of foam such as drainage, stability and interfacial mobility. Copyright © 2018 Elsevier B.V. All rights reserved.

Dynamics of Polydisperse Foam-like Emulsion

NASA Astrophysics Data System (ADS)

Hicock, Harry; Feitosa, Klebert

2011-10-01

Foam is a complex fluid whose relaxation properties are associated with the continuous diffusion of gas from small to large bubbles driven by differences in Laplace pressures. We study the dynamics of bubble rearrangements by tracking droplets of a clear, buoyantly neutral emulsion that coarsens like a foam. The droplets are imaged in three dimensions using confocal microscopy. Analysis of the images allows us to measure their positions and radii, and track their evolution in time. We find that the droplet size distribution fits a Weibull distribution characteristics of foam systems. Additionally, we observe that droplets undergo continuous evolution interspersed by occasional large rearrangements in par with local relaxation behavior typical of foams.

XFEM modeling of hydraulic fracture in porous rocks with natural fractures

NASA Astrophysics Data System (ADS)

Wang, Tao; Liu, ZhanLi; Zeng, QingLei; Gao, Yue; Zhuang, Zhuo

2017-08-01

Hydraulic fracture (HF) in porous rocks is a complex multi-physics coupling process which involves fluid flow, diffusion and solid deformation. In this paper, the extended finite element method (XFEM) coupling with Biot theory is developed to study the HF in permeable rocks with natural fractures (NFs). In the recent XFEM based computational HF models, the fluid flow in fractures and interstitials of the porous media are mostly solved separately, which brings difficulties in dealing with complex fracture morphology. In our new model the fluid flow is solved in a unified framework by considering the fractures as a kind of special porous media and introducing Poiseuille-type flow inside them instead of Darcy-type flow. The most advantage is that it is very convenient to deal with fluid flow inside the complex fracture network, which is important in shale gas extraction. The weak formulation for the new coupled model is derived based on virtual work principle, which includes the XFEM formulation for multiple fractures and fractures intersection in porous media and finite element formulation for the unified fluid flow. Then the plane strain Kristianovic-Geertsma-de Klerk (KGD) model and the fluid flow inside the fracture network are simulated to validate the accuracy and applicability of this method. The numerical results show that large injection rate, low rock permeability and isotropic in-situ stresses tend to lead to a more uniform and productive fracture network.

High Density Polyetherurethane Foam as a Fragmentation and Radiographic Surrogate for Cortical Bone

PubMed Central

Beardsley, Christina L; Heiner, Anneliese D; Brandser, Eric A; Marsh, J Lawrence; Brown, Thomas D

2000-01-01

Background Although one of the most important factors in predicting outcome of articular fracture, the comminution of the fracture is only subjectively assessed. To facilitate development of objective, quantitative measures of comminution phenomena, there is need for a bone fragmentation surrogate. Methods Laboratory investigation was undertaken to develop and characterize a novel synthetic material capable of emulating the fragmentation and radiographic behavior of human cortical bone. Result Screening tests performed with a drop tower apparatus identified high-density polyetherurethane foam as having suitable fragmentation properties. The material's impact behavior and its quasi-static mechanical properties are here described. Dispersal of barium sulfate (BaSO4) in the resin achieved radio-density closely resembling that of bone, without detectably altering mechanical behavior. The surrogate material's ultimate strength, elastic modulus, and quasi-static toughness are within an order of magnitude of those of mammalian cortical bone. The spectrum of comminution patterns produced by this material when impacted with varying amounts of energy is very comparable to the spectrum of bone fragment comminution seen clinically. Conclusions A novel high-density polyetherurethane foam, when subjected to impact loading, sustains comminuted fracture in a manner strikingly similar to cortical bone. Moreover, since the material also can be doped with radio-opacifier so as to closely emulate bone's radiographic signature, it opens many new possibilities for CT-based systematic study of comminution phenomena. PMID:10934621

Multiphase flow in geometrically simple fracture intersections

USGS Publications Warehouse

Basagaoglu, H.; Meakin, P.; Green, C.T.; Mathew, M.; ,

2006-01-01

A two-dimensional lattice Boltzmann (LB) model with fluid-fluid and solid-fluid interaction potentials was used to study gravity-driven flow in geometrically simple fracture intersections. Simulated scenarios included fluid dripping from a fracture aperture, two-phase flow through intersecting fractures and thin-film flow on smooth and undulating solid surfaces. Qualitative comparisons with recently published experimental findings indicate that for these scenarios the LB model captured the underlying physics reasonably well.

Violent flows in aqueous foams III: physical multi-phase model comparison with aqueous foam shock tube experiments

NASA Astrophysics Data System (ADS)

Redford, J. A.; Ghidaglia, J.-M.; Faure, S.

2018-06-01

Mitigation of blast waves in aqueous foams is a problem that has a strong dependence on multi-phase effects. Here, a simplified model is developed from the previous articles treating violent flows (D'Alesio et al. in Eur J Mech B Fluids 54:105-124, 2015; Faure and Ghidaglia in Eur J Mech B Fluids 30:341-359, 2011) to capture the essential phenomena. The key is to have two fluids with separate velocities to represent the liquid and gas phases. This allows for the interaction between the two phases, which may include terms for drag, heat transfer, mass transfer due to phase change, added mass effects, to be included explicitly in the model. A good test for the proposed model is provided by two experimental data sets that use a specially designed shock tube. The first experiment has a test section filled with spray droplets, and the second has a range of aqueous foams in the test section. A substantial attenuation of the shock wave is seen in both cases, but a large difference is observed in the sound speeds. The droplets cause no observable change from the air sound speed, while the foams have a reduced sound speed of approximately 50-75 m/s . In the model given here, an added mass term is introduced in the governing equations to capture the low sound speed. The match between simulation and experiment is found to be satisfactory for both droplets and the foam. This is especially good when considering the complexity of the physics and the effects that are unaccounted for, such as three-dimensionality and droplet atomisation. The resulting statistics illuminate the processes occurring in such flows.

Reactivation of a Propped Hydraulic Fracture

NASA Astrophysics Data System (ADS)

Sarvaramini, E.; Garagash, D.

2014-12-01

The problem of massive fluid injection into a pre-existing fracture has many applications in petroleum industry including underground liquid waste disposal and waterflooding to increase recovery from a hydrocarbon reservoir. Understanding the conditions leading to the re-activation of pre-existing fractures and ensuing propagation is critical for a successful injection project design, and it may also help to mitigate potential environmental hazards, such as contamination of underground aquifers and induced seismicity. The problem of injection of a low viscosity fluid into a permeable formation can be distinguished from conventional hydraulic fracture by the mechanism of fluid leak-off. In conventional fracturing, high viscosity and cake building properties of injected fluid limit leak-off to a 1-D boundary layer incasing the crack. In the case of injection of low viscosity fluid into a fracture, leak-off and related pore fluid diffusion will take place over wider range of scales, from 1-D to 2 or 3-D. We consider a pre-existing stationary propped hydraulic fracture with constrained height into which a fluid is injected under constant flow rate. Although the net effective stress on the crack is initially compressive, the proppant keeps the crack open. It is worthwhile to note that during injection and related pressurization of a propped crack, the fracture breakdown is to be achieved prior to the fracture re-opening. Therefore, the effect of the change of the propped fracture storage on the pressurization dynamics can be neglected. The objective of this work is to study the transient pressurization and the onset of the propagation for a propped fracture. To the end, we formulate and solve a general problem of injection into a fracture accounting for viscous dissipation (i.e. non-uniform pressure distribution). We quantify how the fracture breakdown condition depends upon the rock and fluid properties, the in-situ stress and the fluid injection rate. We also establish a criterion when the assumption of negligible viscous dissipation is justified. The obtained solution is also transportable to the production well test analysis of a fractured well (Cinco et al., SPE 1978).

Experimental insights into geochemical changes in hydraulically fractured Marcellus Shale

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marcon, Virginia; Joseph, Craig; Carter, Kimberly E.

Hydraulic fracturing applied to organic-rich shales has significantly increased the recoverable volume of methane available for U.S. energy consumption. Fluid-shale reactions in the reservoir may affect long-term reservoir productivity and waste management needs through changes to fracture mineral composition and produced fluid chemical composition. We performed laboratory experiments with Marcellus Shale and lab-generated hydraulic fracturing fluid at elevated pressures and temperatures to evaluate mineral reactions and the release of trace elements into solution. Results from the experiment containing fracturing chemicals show evidence for clay and carbonate dissolution, secondary clay and anhydrite precipitation, and early-stage (24-48 h) fluid enrichment of certainmore » elements followed by depletion in later stages (i.e. Al, Cd, Co, Cr, Cu, Ni, Sc, Zn). Other elements such as As, Fe, Mn, Sr, and Y increased in concentration and remained elevated throughout the duration of the experiment with fracturing fluid. Geochemical modeling of experimental fluid data indicates primary clay dissolution, and secondary formation of smectites and barite, after reaction with fracturing fluid. Changes in aqueous organic composition were observed, indicating organic additives may be chemically transformed or sequestered by the formation after hydraulic fracturing. The NaCl concentrations in our fluids are similar to measured concentrations in Marcellus Shale produced waters, showing that these experiments are representative of reservoir fluid chemistries and can provide insight on geochemical reactions that occur in the field. These results can be applied towards evaluating the evolution of hydraulically-fractured reservoirs, and towards understanding geochemical processes that control the composition of produced water from unconventional shales.« less

Experimental insights into geochemical changes in hydraulically fractured Marcellus Shale

DOE PAGES

Marcon, Virginia; Joseph, Craig; Carter, Kimberly E.; ...

2016-11-09

Hydraulic fracturing applied to organic-rich shales has significantly increased the recoverable volume of methane available for U.S. energy consumption. Fluid-shale reactions in the reservoir may affect long-term reservoir productivity and waste management needs through changes to fracture mineral composition and produced fluid chemical composition. We performed laboratory experiments with Marcellus Shale and lab-generated hydraulic fracturing fluid at elevated pressures and temperatures to evaluate mineral reactions and the release of trace elements into solution. Results from the experiment containing fracturing chemicals show evidence for clay and carbonate dissolution, secondary clay and anhydrite precipitation, and early-stage (24-48 h) fluid enrichment of certainmore » elements followed by depletion in later stages (i.e. Al, Cd, Co, Cr, Cu, Ni, Sc, Zn). Other elements such as As, Fe, Mn, Sr, and Y increased in concentration and remained elevated throughout the duration of the experiment with fracturing fluid. Geochemical modeling of experimental fluid data indicates primary clay dissolution, and secondary formation of smectites and barite, after reaction with fracturing fluid. Changes in aqueous organic composition were observed, indicating organic additives may be chemically transformed or sequestered by the formation after hydraulic fracturing. The NaCl concentrations in our fluids are similar to measured concentrations in Marcellus Shale produced waters, showing that these experiments are representative of reservoir fluid chemistries and can provide insight on geochemical reactions that occur in the field. These results can be applied towards evaluating the evolution of hydraulically-fractured reservoirs, and towards understanding geochemical processes that control the composition of produced water from unconventional shales.« less

Dikes, joints, and faults in the upper mantle

NASA Astrophysics Data System (ADS)

Wilshire, H. G.; Kirby, S. H.

1989-04-01

Three different types of macroscopic fractures are recognized in upper-mantle and lower-crustal xenoliths in volcanic rocks from around the world: (1) joints that are tensile fractures not occupied by crystallized magma products (2) dikes that are tensile fractures occupied by mafic magmas crystallized to pyroxenites, gabbros or hydrous-mineral-rich rocks, (3) faults that are unfilled shear fractures with surface markings indicative of shear displacement. In addition to intra-xenolith fractures, xenoliths commonly have polygonal or faceted shapes that represent fractures exploited during incorporation of the xenoliths into the host magma that brought them to the surface. The various types of fractures are considered to have formed in response to the pressures associated with magmatic fluids and to the ambient tectonic stress field. The presence of fracture sets and crosscutting relations indicate that both magma-filled and unfilled fractures can be contemporaneous and that the local stress field can change with time, leading to repeated episodes of fracture. These observations give insight into the nature of deep fracture processes and the importance of fluid-peridotite interactions in the mantle. We suggest that unfilled fractures were opened by volatile fluids exsolved from ascending magmas to the tops of growing dikes. These volatile fluids are important because they are of low viscosity and can rapidly transmit fluid pressure to dike and fault tips and because they lower the energy and tectonic stresses required to extend macroscopic cracks and to allow sliding on pre-existing fractures. Mantle seismicity at depths of 20-65 km beneath active volcanic centers in Hawaii corresponds to the depth interval where CO 2-rich fluids are expected to be liberated from ascending basaltic magmas, suggesting that such fluids play an important role in facilitating earthquake instabilities in the presence of tectonic stresses. Other phenomena related to the fractures include permeation of peridotite by fluid inclusions derived by degassing of magmas, partial melting of peridotite and dike rocks, and metasomatic alteration of peridotite host rock by magmas emplaced in fractures. These effects of magmatism generally reduce the bulk density of peridotite and might also reduce seismic velocities. The velocity contrasts between fractured and unfractured peridotite might be detected by seismic-velocity profiling techniques.

Compressive properties of commercially available polyurethane foams as mechanical models for osteoporotic human cancellous bone

PubMed Central

Patel, Purvi SD; Shepherd, Duncan ET; Hukins, David WL

2008-01-01

Background Polyurethane (PU) foam is widely used as a model for cancellous bone. The higher density foams are used as standard biomechanical test materials, but none of the low density PU foams are universally accepted as models for osteoporotic (OP) bone. The aim of this study was to determine whether low density PU foam might be suitable for mimicking human OP cancellous bone. Methods Quasi-static compression tests were performed on PU foam cylinders of different lengths (3.9 and 7.7 mm) and of different densities (0.09, 0.16 and 0.32 g.cm-3), to determine the Young's modulus, yield strength and energy absorbed to yield. Results Young's modulus values were 0.08–0.93 MPa for the 0.09 g.cm-3 foam and from 15.1–151.4 MPa for the 0.16 and 0.32 g.cm-3 foam. Yield strength values were 0.01–0.07 MPa for the 0.09 g.cm-3 foam and from 0.9–4.5 MPa for the 0.16 and 0.32 g.cm-3 foam. The energy absorbed to yield was found to be negligible for all foam cylinders. Conclusion Based on these results, it is concluded that 0.16 g.cm-3 PU foam may prove to be suitable as an OP cancellous bone model when fracture stress, but not energy dissipation, is of concern. PMID:18844988

Consequences of Fluid Lag in Three-Dimensional Hydraulic Fractures

NASA Astrophysics Data System (ADS)

Advani (Deceased), S. H.; Lee, T. S.; Dean, R. H.; Pak, C. K.; Avasthi, J. M.

1997-04-01

Research investigations on three-dimensional (3-D) rectangular hydraulic fracture configurations with varying degrees of fluid lag are reported. This paper demonstrates that a 3-D fracture model coupled with fluid lag (a small region of reduced pressure) at the fracture tip can predict very large excess pressure measurements for hydraulic fracture processes. Predictions of fracture propagation based on critical stress intensity factors are extremely sensitive to the pressure profile at the tip of a propagating fracture. This strong sensitivity to the pressure profile at the tip of a hydraulic fracture is more strongly pronounced in 3-D models versus 2-D models because 3-D fractures are clamped at the top and bottom, and pressures in the 3-D fractures that are far removed from the fracture tip have little effect on the stress intensity factor at the fracture tip. This rationale for the excess pressure mechanism is in marked contrast to the crack tip process damage zone assumptions and attendant high rock fracture toughness value hypotheses advanced in the literature. A comparison with field data is presented to illustrate the proposed fracture fluid pressure sensitivity phenomenon. This paper does not attempt to calculate the length of the fluid lag region in a propagating fracture but instead attempts to show that the pressure profile at the tip of the propagating fracture plays a major role in fracture propagation, and this role is magnified in 3-D models. Int. J. Numer. Anal. Meth. Geomech., vol. 21, 229-240 (1997).

Fluid Production Induced Stress Analysis Surrounding an Elliptic Fracture

NASA Astrophysics Data System (ADS)

Pandit, Harshad Rajendra

Hydraulic fracturing is an effective technique used in well stimulation to increase petroleum well production. A combination of multi-stage hydraulic fracturing and horizontal drilling has led to the recent boom in shale gas production which has changed the energy landscape of North America. During the fracking process, highly pressurized mixture of water and proppants (sand and chemicals) is injected into to a crack, which fractures the surrounding rock structure and proppants help in keeping the fracture open. Over a longer period, however, these fractures tend to close due to the difference between the compressive stress exerted by the reservoir on the fracture and the fluid pressure inside the fracture. During production, fluid pressure inside the fracture is reduced further which can accelerate the closure of a fracture. In this thesis, we study the stress distribution around a hydraulic fracture caused by fluid production. It is shown that fluid flow can induce a very high hoop stress near the fracture tip. As the pressure gradient increases stress concentration increases. If a fracture is very thin, the flow induced stress along the fracture decreases, but the stress concentration at the fracture tip increases and become unbounded for an infinitely thin fracture. The result from the present study can be used for studying the fracture closure problem, and ultimately this in turn can lead to the development of better proppants so that prolific well production can be sustained for a long period of time.

Proceedings of the International Symposium on Dynamics of Fluids in Fractured Rocks: Concepts and Recent Advances

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faybishenko, B.

1999-02-01

This publication contains extended abstracts of papers presented at the International Symposium ''Dynamics of Fluids in Fractured Rocks: Concepts and Recent Advances'' held at Ernest Orlando Lawrence Berkeley National Laboratory on February 10-12, 1999. This Symposium is organized in Honor of the 80th Birthday of Paul A. Witherspoon, who initiated some of the early investigations on flow and transport in fractured rocks at the University of California, Berkeley, and at Lawrence Berkeley National Laboratory. He is a key figure in the development of basic concepts, modeling, and field measurements of fluid flow and contaminant transport in fractured rock systems. Themore » technical problems of assessing fluid flow, radionuclide transport, site characterization, modeling, and performance assessment in fractured rocks remain the most challenging aspects of subsurface flow and transport investigations. An understanding of these important aspects of hydrogeology is needed to assess disposal of nu clear wastes, development of geothermal resources, production of oil and gas resources, and remediation of contaminated sites. These Proceedings of more than 100 papers from 12 countries discuss recent scientific and practical developments and the status of our understanding of fluid flow and radionuclide transport in fractured rocks. The main topics of the papers are: Theoretical studies of fluid flow in fractured rocks; Multi-phase flow and reactive chemical transport in fractured rocks; Fracture/matrix interactions; Hydrogeological and transport testing; Fracture flow models; Vadose zone studies; Isotopic studies of flow in fractured systems; Fractures in geothermal systems; Remediation and colloid transport in fractured systems; and Nuclear waste disposal in fractured rocks.« less

Influence of foam on the stability characteristics of immiscible flow in porous media

NASA Astrophysics Data System (ADS)

van der Meer, J. M.; Farajzadeh, R.; Rossen, W. R.; Jansen, J. D.

2018-01-01

Accurate field-scale simulations of foam enhanced oil recovery are challenging, due to the sharp transition between gas and foam. Hence, unpredictable numerical and physical behavior is often observed, casting doubt on the validity of the simulation results. In this paper, a thorough stability analysis of the foam model is presented to validate the simulation results. We study the effect of a strongly non-monotonous total mobility function arising from foam models on the stability characteristics of the flow. To this end, we apply the linear stability analysis to nearly discontinuous relative permeability functions and compare the results with those of highly accurate numerical simulations. In addition, we present a qualitative analysis of the effect of different reservoir and fluid properties on the foam fingering behavior. In particular, we consider the effect of heterogeneity of the reservoir, injection rates, and foam quality. Relative permeability functions play an important role in the onset of fingering behavior of the injected fluid. Hence, we can deduce that stability properties are highly dependent on the non-linearity of the foam transition. The foam-water interface is governed by a very small total mobility ratio, implying a stable front. The transition between gas and foam, however, exhibits a huge total mobility ratio, leading to instabilities in the form of viscous fingering. This implies that there is an unstable pattern behind the front. We deduce that instabilities are able to grow behind the front but are later absorbed by the expanding wave. Moreover, the stability analysis, validated by numerical simulations, provides valuable insights about the important scales and wavelengths of the foam model. In this way, we remove the ambiguity regarding the effect of grid resolution on the convergence of the solutions. This insight forms an essential step toward the design of a suitable computational solver that captures all the appropriate scales, while retaining computational efficiency.

Foam imbibition in a Hele-Shaw cell via laminated microfluidic ``T-junction'' device

NASA Astrophysics Data System (ADS)

Parra, Dina; Ward, Thomas

2013-11-01

In this talk we analyze experimental results of a novel microfluidic ``T-junction'' device, made from laminated plastic, that is used to produce foam in porous media. The fluids, both Newtonian and non-Newtonian liquids and air, are driven using constant-static pressure fluid pumping. For the T-junction geometry studied there are novel observations with this type of pumping: 1) at low pressure ratios there is an increase in the liquid and total flow rates and 2) at higher pressure ratios there is a decrease in the liquid flow rate. To understand this phenomenon we visualize the drop production process near the T-junction. Furthermore, flow rates for the liquid and total volume are estimated by imbibing the foam into a Hele-Shaw cell. Foam is produced by using a mixture containing aqueous polyacrylamide of concentrations ranging from 0.01-0.10% by weight and several solution also containing a sodium-lauryl-sulfate (SLS) surfactant at concentrations ranging 0.01-0.1% by weight.

Primary drainage in geological fractures: Effects of aperture variability and wettability

NASA Astrophysics Data System (ADS)

Yang, Z.; Méheust, Y.; Neuweiler, I.

2017-12-01

Understanding and controlling fluid-fluid displacement in porous and fractured media is a key asset for many practical applications, such as the geological storage of CO2, hydrocarbon recovery, groundwater remediation, etc. We numerically investigate fluid-fluid displacement in rough-walled fractures with a focus on the combined effect of wettability, the viscous contrast between the two fluids, and fracture surface topography on drainage patterns and interface growth. A model has been developed to simulate the dynamic displacement of one fluid by another immiscible one in a rough geological fracture; the model takes both capillary and viscous forces into account. Capillary pressures at the fluid-fluid interface are calculated based on the Young-Laplace equation using the two principal curvatures (aperture-induced curvature and in-plane curvature) [1], while viscous forces are calculated by continuously solving the fluid pressure field in the fracture. The aperture field of a fracture is represented by a spatially correlated random field, with a power spectral density of the fracture wall topographies scaling as a power law, and a cutoff wave-length above which the Fourier modes of the two walls are identical [2]. We consider flow scenarios with both rectangular and radial configurations. Results show that the model is able to produce displacement patterns of compact displacement, capillary fingering, and viscous fingering, as well as the transitions between them. Both reducing the aperture variability and increasing the contact angle (from drainage to weak imbibition) can stabilize the displacement due to the influence of the in-plane curvature, an effect analogous to that of the cooperative pore filling in porous media. These results suggest that for geometries typical of geological fractures we can extend the phase diagram in the parameter space of capillary number and mobility ratio by another dimension to take into account the combined effect of wettability and fracture aperture topography. References: [1] Yang, Z. et al. (2012), A generalized approach for estimation of in-plane curvature in invasion percolation models for drainage in fractures. Wat. Resour. Res., 48(9), W09507. [2] Yang, Z. et al. (2016), Fluid trapping during capillary displacement in fractures. Adv. Water Resour., 95, 264-275.

Seismic Waves in Rocks with Fluids and Fractures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berryman, J G

2006-02-06

Seismic wave propagation through the earth is often strongly affected by the presence of fractures. When these fractures are filled with fluids (oil, gas, water, CO{sub 2}, etc.), the type and state of the fluid (liquid or gas) can make a large difference in the response of the seismic waves. This paper will summarize some early work of the author on methods of deconstructing the effects of fractures, and any fluids within these fractures, on seismic wave propagation as observed in reflection seismic data. Methods to be explored here include Thomsen's anisotropy parameters for wave moveout (since fractures often inducemore » elastic anisotropy), and some very convenient fracture parameters introduced by Sayers and Kachanov that permit a relatively simple deconstruction of the elastic behavior in terms of fracture parameters (whenever this is appropriate).« less

Mechanics of Hydraulic Fractures

NASA Astrophysics Data System (ADS)

Detournay, Emmanuel

2016-01-01

Hydraulic fractures represent a particular class of tensile fractures that propagate in solid media under pre-existing compressive stresses as a result of internal pressurization by an injected viscous fluid. The main application of engineered hydraulic fractures is the stimulation of oil and gas wells to increase production. Several physical processes affect the propagation of these fractures, including the flow of viscous fluid, creation of solid surfaces, and leak-off of fracturing fluid. The interplay and the competition between these processes lead to multiple length scales and timescales in the system, which reveal the shifting influence of the far-field stress, viscous dissipation, fracture energy, and leak-off as the fracture propagates.

Rheology of Foam Near the Order-Disorder Phase Transition

NASA Technical Reports Server (NTRS)

Holt, R. Glynn; McDaniel, J. Gregory

1999-01-01

Foams are extremely important in a variety of industrial applications. Foams are widely used in fire-fighting applications, and are especially effective in fighting flammable liquid fires. In fact the Fire Suppression System aboard the Space Shuttle utilizes cylinders of Halon foam, which, when fired, force a rapidly expanding foam into the convoluted spaces behind instrument panels. Foams are critical in the process of enhanced oil recovery, due to their surface-active and highly viscous nature. They are also used as drilling fluids in underpressurized geologic formations. They are used as transport agents, and as trapping agents. They are also used as separation agents, where ore refinement is accomplished by froth flotation of the typically lighter and hydrophobic contaminants. The goal of the proposed investigation is the determination of the mechanical and rheological properties of foams, utilizing the microgravity environment to explore foam rheology for foams which cannot exist, or only exist for a short time, in 1g.

Fluid driven fracture mechanics in highly anisotropic shale: a laboratory study with application to hydraulic fracturing

NASA Astrophysics Data System (ADS)

Gehne, Stephan; Benson, Philip; Koor, Nick; Enfield, Mark

2017-04-01

The finding of considerable volumes of hydrocarbon resources within tight sedimentary rock formations in the UK led to focused attention on the fundamental fracture properties of low permeability rock types and hydraulic fracturing. Despite much research in these fields, there remains a scarcity of available experimental data concerning the fracture mechanics of fluid driven fracturing and the fracture properties of anisotropic, low permeability rock types. In this study, hydraulic fracturing is simulated in a controlled laboratory environment to track fracture nucleation (location) and propagation (velocity) in space and time and assess how environmental factors and rock properties influence the fracture process and the developing fracture network. Here we report data on employing fluid overpressure to generate a permeable network of micro tensile fractures in a highly anisotropic shale ( 50% P-wave velocity anisotropy). Experiments are carried out in a triaxial deformation apparatus using cylindrical samples. The bedding planes are orientated either parallel or normal to the major principal stress direction (σ1). A newly developed technique, using a steel guide arrangement to direct pressurised fluid into a sealed section of an axially drilled conduit, allows the pore fluid to contact the rock directly and to initiate tensile fractures from the pre-defined zone inside the sample. Acoustic Emission location is used to record and map the nucleation and development of the micro-fracture network. Indirect tensile strength measurements at atmospheric pressure show a high tensile strength anisotropy ( 60%) of the shale. Depending on the relative bedding orientation within the stress field, we find that fluid induced fractures in the sample propagate in two of the three principal fracture orientations: Divider and Short-Transverse. The fracture progresses parallel to the bedding plane (Short-Transverse orientation) if the bedding plane is aligned (parallel) with the direction of σ1. Conversely, the crack plane develops perpendicular to the bedding plane, if the bedding plane is orientated normal to σ1. Fracture initiation pressures are higher in the Divider orientation ( 24MPa) than in the Short-Transverse orientation ( 14MPa) showing a tensile strength anisotropy ( 42%) comparable to ambient tensile strength results. We then use X-Ray Computed Tomography (CT) 3D-images to evaluate the evolved fracture network in terms of fracture pattern, aperture and post-test water permeability. For both fracture orientations, very fine, axial fractures evolve over the entire length of the sample. For the fracturing in the Divider orientation, it has been observed, that in some cases, secondary fractures are branching of the main fracture. Test data from fluid driven fracturing experiments suggest that fracture pattern, fracture propagation trajectories and fracturing fluid pressure (initiation and propagation pressure) are predominantly controlled by the interaction between the anisotropic mechanical properties of the shale and the anisotropic stress environment. The orientation of inherent rock anisotropy relative to the principal stress directions seems to be the main control on fracture orientation and required fracturing pressure.

Influence of patchy saturation on seismic dispersion and attenuation in fractured porous media

NASA Astrophysics Data System (ADS)

Jinwei, Zhang; Handong, Huang; Chunhua, Wu; Sheng, Zhang; Gang, Wu; Fang, Chen

2018-04-01

Wave induced fluid flow due to mesoscopic heterogeneity can explain seismic dispersion and attenuation in the seismic frequency band. The mesoscopic heterogeneity mainly contains lithological variations, patchy saturation and mesoscopic fractures. The patchy saturation models which are locally based on Biot theory for porous media have been deeply studied, but the patchy saturation model for fractured porous media is rarely studied. In this paper, we develop a model to describe the poroelastic characteristics in fractured porous media where the background and fractures are filled with different fluids based on two scales of squirt flow. The seismic dispersion and attenuation in fractured porous media occur in two scales, the microscale due to fluid flow between pores and micro-cracks and mesoscale due to fluid flow between background and heterogeneities. We derive the complex stiffness tensor through the solution of stress equivalence and fluid conservation. Two new parameters embodying the fluid effects are introduced into the model compared with the single fluid phase model. The model is consistent with Gassmann-Wood equation at low frequency limit and consistent with the isolated fracture model at high frequency limit. After the frequency dependent stiffness tensor is obtained, the variations of velocities and inverse quality factors with frequency are analyzed through several numerical examples. We investigated three poroelastic cases: medium including pores and micro-cracks, media including pores, micro-cracks and fractures, media including pores and fractures. The frequency dependent characteristics of patchy saturation model are different with those of single fluid model not only in characteristic frequency but also in the magnitude of the attenuation. Finally, we discuss the results obtained and the special case where the fractures are saturated with gas or dry and the background is filled with water. We also compare our results with those of patchy saturation model and double porosity model. The results will contribute to the actual exploration work to a certain extent, such as the fluid identification in fractured reservoirs.

Influence of patchy saturation on seismic dispersion and attenuation in fractured porous media

NASA Astrophysics Data System (ADS)

Zhang, Jinwei; Huang, Handong; Wu, Chunhua; Zhang, Sheng; Wu, Gang; Chen, Fang

2018-07-01

Wave-induced fluid flow due to mesoscopic heterogeneity can explain seismic dispersion and attenuation in the seismic frequency band. The mesoscopic heterogeneity mainly contains lithological variations, patchy saturation and mesoscopic fractures. The patchy saturation models which are locally based on Biot theory for porous media have been deeply studied, but the patchy saturation model for fractured porous media is rarely studied. In this paper, we develop a model to describe the poroelastic characteristics in fractured porous media where the background and fractures are filled with different fluids based on two scales of squirt flow. The seismic dispersion and attenuation in fractured porous media occur in two scales, the microscale due to fluid flow between pores and microcracks and mesoscale due to fluid flow between background and heterogeneities. We derive the complex stiffness tensor through the solution of stress equivalence and fluid conservation. Two new parameters embodying the fluid effects are introduced into the model compared with the single fluid phase model. The model is consistent with Gassmann-Wood equation at low-frequency limit and consistent with the isolated fracture model at high-frequency limit. After the frequency-dependent stiffness tensor is obtained, the variations of velocities and inverse quality factors with frequency are analysed through several numerical examples. We investigated three poroelastic cases: medium including pores and microcracks; media including pores, microcracks and fractures; media including pores and fractures. The frequency-dependent characteristics of patchy saturation model are different with those of single fluid model not only in characteristic frequency but also in the magnitude of the attenuation. Finally, we discuss the results obtained and the special case where the fractures are saturated with gas or dry and the background is filled with water. We also compare our results with those of patchy saturation model and double porosity model. The results will contribute to the actual exploration work to a certain extent, such as the fluid identification in fractured reservoirs.

Laboratory and numerical decompression experiments: an insight into the nucleation and growth of bubbles

NASA Astrophysics Data System (ADS)

Spina, L.; Colucci, S.; De'Michieli Vitturi, M.; Scheu, B.; Dingwell, D. B.

2014-12-01

Numerical modeling, joined with experimental investigations, is fundamental for studying the dynamics of magmatic fluid into the conduit, where direct observations are unattainable. Furthermore, laboratory experiments can provide invaluable data to vunalidate complex multiphase codes. With the aim on unveil the essence of nucleation process, as well as the behavior of the multiphase magmatic fluid, we performed slow decompression experiments in a shock tube system. We choose silicon oil as analogue for the magmatic melt, and saturated it with Argon at 10 MPa for 72h. The slow decompression to atmospheric conditions was monitored through a high speed camera and pressure sensors, located into the experimental conduit. The experimental conditions of the decompression process have then been reproduced numerically with a compressible multiphase solver based on OpenFOAM. Numerical simulations have been performed by the OpenFOAM compressibleInterFoam solver for 2 compressible, non-isothermal immiscible fluids, using a VOF (volume of fluid) phase-fraction based interface capturing approach. The data extracted from 2D images obtained from laboratory analyses were compared to the outcome of numerical investigation, showing the capability of the model to capture the main processes studied.

Electrophilic acid gas-reactive fluid, proppant, and process for enhanced fracturing and recovery of energy producing materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernandez, Carlos A.; Heldebrant, David J.; Bonneville, Alain

An electrophilic acid gas-reactive fracturing fluid, proppant, and process are detailed. The fluid expands in volume to provide rapid and controlled increases in pressure that enhances fracturing in subterranean bedrock for recovery of energy-producing materials. The proppant stabilizes fracture openings in the bedrock to enhance recovery of energy-producing materials.

Modeling of Propagation of Interacting Cracks Under Hydraulic Pressure Gradient

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Hai; Mattson, Earl Douglas; Podgorney, Robert Karl

A robust and reliable numerical model for fracture initiation and propagation, which includes the interactions among propagating fractures and the coupling between deformation, fracturing and fluid flow in fracture apertures and in the permeable rock matrix, would be an important tool for developing a better understanding of fracturing behaviors of crystalline brittle rocks driven by thermal and (or) hydraulic pressure gradients. In this paper, we present a physics-based hydraulic fracturing simulator based on coupling a quasi-static discrete element model (DEM) for deformation and fracturing with conjugate lattice network flow model for fluid flow in both fractures and porous matrix. Fracturingmore » is represented explicitly by removing broken bonds from the network to represent microcracks. Initiation of new microfractures and growth and coalescence of the microcracks leads to the formation of macroscopic fractures when external and/or internal loads are applied. The coupled DEM-network flow model reproduces realistic growth pattern of hydraulic fractures. In particular, simulation results of perforated horizontal wellbore clearly demonstrate that elastic interactions among multiple propagating fractures, fluid viscosity, strong coupling between fluid pressure fluctuations within fractures and fracturing, and lower length scale heterogeneities, collectively lead to complicated fracturing patterns.« less

Making a frothy shampoo or beer

NASA Astrophysics Data System (ADS)

Durian, Douglas

2011-03-01

The terms ``foam'' and ``froth'' refer to a dispersion of gas bubbles in a liquid. Why do certain liquids show a tendency to foam while others do not? For example, bubbles can be produced in pure water by vigorous agitation, but then they rapidly coalesce and disappear. While foams cannot be produced with pure water, foams associated with beer or shampoo can persist for several minutes or even hours. What ingredient(s) in shampoo and beer make their foams stable, and what physical concepts control their stability? In this talk I'll review three basic mechanisms underlying foam stability, and I'll make connection with current research on coarsening by the diffusion of gas from smaller to larger bubbles. With thanks to Srinivasa Raghavan, Adam Roth, and NASA Microgravity Fluid Physics Grant NNX07AP20G.

Streaming Potential Modeling to Understand the Identification of Hydraulically Active Fractures and Fracture-Matrix Fluid Interactions Using the Self-Potential Method

NASA Astrophysics Data System (ADS)

Jougnot, D.; Roubinet, D.; Linde, N.; Irving, J.

2016-12-01

Quantifying fluid flow in fractured media is a critical challenge in a wide variety of research fields and applications. To this end, geophysics offers a variety of tools that can provide important information on subsurface physical properties in a noninvasive manner. Most geophysical techniques infer fluid flow by data or model differencing in time or space (i.e., they are not directly sensitive to flow occurring at the time of the measurements). An exception is the self-potential (SP) method. When water flows in the subsurface, an excess of charge in the pore water that counterbalances electric charges at the mineral-pore water interface gives rise to a streaming current and an associated streaming potential. The latter can be measured with the SP technique, meaning that the method is directly sensitive to fluid flow. Whereas numerous field experiments suggest that the SP method may allow for the detection of hydraulically active fractures, suitable tools for numerically modeling streaming potentials in fractured media do not exist. Here, we present a highly efficient two-dimensional discrete-dual-porosity approach for solving the fluid-flow and associated self-potential problems in fractured domains. Our approach is specifically designed for complex fracture networks that cannot be investigated using standard numerical methods due to computational limitations. We then simulate SP signals associated with pumping conditions for a number of examples to show that (i) accounting for matrix fluid flow is essential for accurate SP modeling and (ii) the sensitivity of SP to hydraulically active fractures is intimately linked with fracture-matrix fluid interactions. This implies that fractures associated with strong SP amplitudes are likely to be hydraulically conductive, attracting fluid flow from the surrounding matrix.

Multiwell fracturing experiments. [Nitrogen foam fracture treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warpinski, N.

The objective of the Multiwell fracturing experiments is to test and develop the technology for the efficient stimulation of tight, lenticular gas sands. This requires basic understanding of: (1) fracture behavior and geometry in this complex lithologic environment, and (2) subsequent production into the created fracture. The intricate interplay of the hydraulic fracture with the lens geometry, the internal reservoir characteristics (fractures, reservoir breaks, etc.), the in situ stresses, and the mechanical defects (fracture, bedding, etc.) need to be defined in order to develop a successful stimulation program. The stimulation phase of the Multiwell Experiment is concerned with: (1) determiningmore » important rock/reservoir properties that influence or control fracture geometry and behavior, (2) designing fracture treatments to achieve a desired size and objectives, and (3) conducting post-treatment analyses to evaluate the effectiveness of the treatment. Background statement, project description, results and evaluation of future plans are presented. 5 refs., 2 figs., 2 tabs.« less

Rock deformation models and fluid leak-off in hydraulic fracturing

NASA Astrophysics Data System (ADS)

Yarushina, Viktoriya M.; Bercovici, David; Oristaglio, Michael L.

2013-09-01

Fluid loss into reservoir rocks during hydraulic fracturing is modelled via a poro-elastoplastic pressure diffusion equation in which the total compressibility is a sum of fluid, rock and pore space compressibilities. Inclusion of pore compressibility and porosity-dependent permeability in the model leads to a strong pressure dependence of leak-off (i.e. drainage rate). Dilation of the matrix due to fluid invasion causes higher rates of fluid leak-off. The present model is appropriate for naturally fractured and tight gas reservoirs as well as for soft and poorly consolidated formations whose mechanical behaviour departs from simple elastic laws. Enhancement of the leak-off coefficient by dilation, predicted by the new model, may help explain the low percentage recovery of fracturing fluid (usually between 5 and 50 per cent) in shale gas stimulation by hydraulic fracturing.

Experiments and Simulations of Fully Hydro-Mechanically Coupled Response of Rough Fractures Exposed to High-Pressure Fluid Injection

NASA Astrophysics Data System (ADS)

Vogler, D.; Settgast, R. R.; Annavarapu, C.; Madonna, C.; Bayer, P.; Amann, F.

2018-02-01

In this work, we present the application of a fully coupled hydro-mechanical method to investigate the effect of fracture heterogeneity on fluid flow through fractures at the laboratory scale. Experimental and numerical studies of fracture closure behavior in the presence of heterogeneous mechanical and hydraulic properties are presented. We compare the results of two sets of laboratory experiments on granodiorite specimens against numerical simulations in order to investigate the mechanical fracture closure and the hydro-mechanical effects, respectively. The model captures fracture closure behavior and predicts a nonlinear increase in fluid injection pressure with loading. Results from this study indicate that the heterogeneous aperture distributions measured for experiment specimens can be used as model input for a local cubic law model in a heterogeneous fracture to capture fracture closure behavior and corresponding fluid pressure response.

Coalescence of Fluid-Driven Fractures

NASA Astrophysics Data System (ADS)

O'Keeffe, Niall; Zheng, Zhong; Huppert, Herbert; Linden, Paul

2017-11-01

We present an experimental study on the coalescence of two in-plane fluid-driven penny-shaped fractures in a brittle elastic medium. Initially, two fluid-driven fractures propagate independently of each other in the same plane. Then when the radial extent of each fracture reaches a certain distance the fractures begin to interact and coalesce. This coalescence forms a bridge between the fractures and then, in an intermediate period following the contact of the two fractures, most growth is observed to focus along this bridge, perpendicular to the line connecting the injection sources. We analyse the growth and shape of this bridge at various stages after coalescence and the transitions between different stages of growth. We also investigate the influence of the injection rate, the distance between two injection points, the viscosity of the fluid and the Young's modulus of the elastic medium on the coalescence of the fractures.

Foam flows through a local constriction

NASA Astrophysics Data System (ADS)

Chevalier, T.; Koivisto, J.; Shmakova, N.; Alava, M. J.; Puisto, A.; Raufaste, C.; Santucci, S.

2017-11-01

We present an experimental study of the flow of a liquid foam, composed of a monolayer of millimetric bubbles, forced to invade an inhomogeneous medium at a constant flow rate. To model the simplest heterogeneous fracture medium, we use a Hele-Shaw cell consisting of two glass plates separated by a millimetric gap, with a local constriction. This single defect localized in the middle of the cell reduces locally its gap thickness, and thus its local permeability. We investigate here the influence of the geometrical property of the defect, specifically its height, on the average steady-state flow of the foam. In the frame of the flowing foam, we can observe a clear recirculation around the obstacle, characterized by a quadrupolar velocity field with a negative wake downstream the obstacle, which intensity evolves systematically with the obstacle height.

Study on Microstructures and Mechanical Properties of Foam Titanium Carbide Ceramics Fabricated by Reaction Sintering Process

NASA Astrophysics Data System (ADS)

Ma, Yana; Bao, Chonggao; Chen, Jie; Song, Suocheng; Han, Longhao

2018-05-01

Foam titanium carbide (TiC) ceramics with a three-dimensional network structure were fabricated by the reaction sintering process, in which polyurethane foam was taken as the template, and TiO2 and phenolic resin were used as the reactants. Phase, microstructures and fracture morphologies of foam TiC ceramics were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results show that when the mass ratios of phenolic resin and TiO2 (F/T) are (0.8-1.2): 1, foam TiC ceramics with pure TiC phase can be formed. As the F/T ratios increase, crystal lattice parameters of fabricated foam TiC ceramics become bigger. When the value of F/T decreases from 1.2 to 0.8, grain size of TiC grows larger and microstructures get denser; meanwhile, the compressive strength increases from 0.10 to 1.05 MPa. Additionally, either raising the sintering temperatures or extending holding time can facilitate the completion of the reaction process and increase the compressive strength.

Hydraulic Fracturing and Production Optimization in Eagle Ford Shale Using Coupled Geomechanics and Fluid Flow Model

NASA Astrophysics Data System (ADS)

Suppachoknirun, Theerapat; Tutuncu, Azra N.

2017-12-01

With increasing production from shale gas and tight oil reservoirs, horizontal drilling and multistage hydraulic fracturing processes have become a routine procedure in unconventional field development efforts. Natural fractures play a critical role in hydraulic fracture growth, subsequently affecting stimulated reservoir volume and the production efficiency. Moreover, the existing fractures can also contribute to the pressure-dependent fluid leak-off during the operations. Hence, a reliable identification of the discrete fracture network covering the zone of interest prior to the hydraulic fracturing design needs to be incorporated into the hydraulic fracturing and reservoir simulations for realistic representation of the in situ reservoir conditions. In this research study, an integrated 3-D fracture and fluid flow model have been developed using a new approach to simulate the fluid flow and deliver reliable production forecasting in naturally fractured and hydraulically stimulated tight reservoirs. The model was created with three key modules. A complex 3-D discrete fracture network model introduces realistic natural fracture geometry with the associated fractured reservoir characteristics. A hydraulic fracturing model is created utilizing the discrete fracture network for simulation of the hydraulic fracture and flow in the complex discrete fracture network. Finally, a reservoir model with the production grid system is used allowing the user to efficiently perform the fluid flow simulation in tight formations with complex fracture networks. The complex discrete natural fracture model, the integrated discrete fracture model for the hydraulic fracturing, the fluid flow model, and the input dataset have been validated against microseismic fracture mapping and commingled production data obtained from a well pad with three horizontal production wells located in the Eagle Ford oil window in south Texas. Two other fracturing geometries were also evaluated to optimize the cumulative production and for the three wells individually. Significant reduction in the production rate in early production times is anticipated in tight reservoirs regardless of the fracturing techniques implemented. The simulations conducted using the alternating fracturing technique led to more oil production than when zipper fracturing was used for a 20-year production period. Yet, due to the decline experienced, the differences in cumulative production get smaller, and the alternating fracturing is not practically implementable while field application of zipper fracturing technique is more practical and widely used.

Group invariant solution for a pre-existing fracture driven by a power-law fluid in permeable rock

NASA Astrophysics Data System (ADS)

Fareo, A. G.; Mason, D. P.

2016-06-01

Group invariant analytical and numerical solutions for the evolution of a two-dimensional fracture with nonzero initial length in permeable rock and driven by an incompressible non-Newtonian fluid of power-law rheology are obtained. The effect of fluid leak-off on the evolution of the power-law fluid fracture is investigated.

Domain Growth Kinetics in Stratifying Foam Films

NASA Astrophysics Data System (ADS)

Zhang, Yiran; Sharma, Vivek

2015-03-01

Baking bread, brewing cappuccino, pouring beer, washing dishes, shaving, shampooing, whipping eggs and blowing bubbles all involve creation of aqueous foam films. Typical foam films consist of two surfactant-laden surfaces that are μ 5 nm - 10 micron apart. Sandwiched between these interfacial layers is a fluid that drains primarily under the influence of viscous and interfacial forces, including disjoining pressure. Interestingly, for certain low molecular weight surfactants, a layered ordering of micelles inside the foam films (thickness <100 nm) leads to a stepwise thinning phenomena called stratification. We experimentally elucidate the influence of these different driving forces, and confinement on drainage kinetics of horizontal stratifying foam films. Thinner, darker domains spontaneously grow within foam films. Quantitative characterization of domain growth visualized in a using Scheludko-type thin film cell and a theoretical model based on lubrication analysis, provide critical insights into hydrodynamics of thin foam films, and the strength and nature of surface forces, including supramolecular oscillatory structural forces.

Simulation of two-phase flow in horizontal fracture networks with numerical manifold method

NASA Astrophysics Data System (ADS)

Ma, G. W.; Wang, H. D.; Fan, L. F.; Wang, B.

2017-10-01

The paper presents simulation of two-phase flow in discrete fracture networks with numerical manifold method (NMM). Each phase of fluids is considered to be confined within the assumed discrete interfaces in the present method. The homogeneous model is modified to approach the mixed fluids. A new mathematical cover formation for fracture intersection is proposed to satisfy the mass conservation. NMM simulations of two-phase flow in a single fracture, intersection, and fracture network are illustrated graphically and validated by the analytical method or the finite element method. Results show that the motion status of discrete interface significantly depends on the ratio of mobility of two fluids rather than the value of the mobility. The variation of fluid velocity in each fracture segment and the driven fluid content are also influenced by the ratio of mobility. The advantages of NMM in the simulation of two-phase flow in a fracture network are demonstrated in the present study, which can be further developed for practical engineering applications.

Vibrational modes of hydraulic fractures: Inference of fracture geometry from resonant frequencies and attenuation

NASA Astrophysics Data System (ADS)

Lipovsky, Bradley P.; Dunham, Eric M.

2015-02-01

Oscillatory seismic signals arising from resonant vibrations of hydraulic fractures are observed in many geologic systems, including volcanoes, glaciers and ice sheets, and hydrocarbon and geothermal reservoirs. To better quantify the physical dimensions of fluid-filled cracks and properties of the fluids within them, we study wave motion along a thin hydraulic fracture waveguide. We present a linearized analysis, valid at wavelengths greater than the fracture aperture, that accounts for quasi-static elastic deformation of the fracture walls, as well as fluid viscosity, inertia, and compressibility. In the long-wavelength limit, anomalously dispersed guided waves known as crack or Krauklis waves propagate with restoring force from fracture wall elasticity. At shorter wavelengths, the waves become sound waves within the fluid channel. Wave attenuation in our model is due to fluid viscosity, rather than seismic radiation from crack tips or fracture wall roughness. We characterize viscous damping at both low frequencies, where the flow is always fully developed, and at high frequencies, where the flow has a nearly constant velocity profile away from viscous boundary layers near the fracture walls. Most observable seismic signals from resonating fractures likely arise in the boundary layer crack wave limit, where fluid-solid coupling is pronounced and attenuation is minimal. We present a method to estimate the aperture and length of a resonating hydraulic fracture using both the seismically observed quality factor and characteristic frequency. Finally, we develop scaling relations between seismic moment and characteristic frequency that might be useful when interpreting the statistics of hydraulic fracture events.

Feasibility of Use of Plastic Foams for Small Vessel Flotation Devices.

DTIC Science & Technology

1976-01-01

waterproofing agents, namely, Dow Corning Silicone 200 fluid, zinc stearate, sodium silicate, Fisher Bath Wax , Carnauba wax , and paraffin wax . Some of...these materials (e.g., waxes ) did not mix well with the foam solution. None of these materials was effective in preventing water absorption by polystyrene

Hydraulic Properties of Closely Spaced Dipping Open Fractures Intersecting a Fluid-Filled Borehole Derived From Tube Wave Generation and Scattering

NASA Astrophysics Data System (ADS)

Minato, Shohei; Ghose, Ranajit; Tsuji, Takeshi; Ikeda, Michiharu; Onishi, Kozo

2017-10-01

Fluid-filled fractures and fissures often determine the pathways and volume of fluid movement. They are critically important in crustal seismology and in the exploration of geothermal and hydrocarbon reservoirs. We introduce a model for tube wave scattering and generation at dipping, parallel-wall fractures intersecting a fluid-filled borehole. A new equation reveals the interaction of tube wavefield with multiple, closely spaced fractures, showing that the fracture dip significantly affects the tube waves. Numerical modeling demonstrates the possibility of imaging these fractures using a focusing analysis. The focused traces correspond well with the known fracture density, aperture, and dip angles. Testing the method on a VSP data set obtained at a fault-damaged zone in the Median Tectonic Line, Japan, presents evidences of tube waves being generated and scattered at open fractures and thin cataclasite layers. This finding leads to a new possibility for imaging, characterizing, and monitoring in situ hydraulic properties of dipping fractures using the tube wavefield.

Fully Coupled 3D Finite Element Model of Hydraulic Fracturing in a Permeable Rock Formation

NASA Astrophysics Data System (ADS)

Salimzadeh, S.; Paluszny, A.; Zimmerman, R. W.

2015-12-01

Hydraulic fracturing in permeable rock formations is a complex three-dimensional multi-physics phenomenon. Numerous analytical models of hydraulic fracturing processes have been proposed that typically simplify the physical processes, or somehow reduce the problem from three dimensions to two dimensions. Moreover, although such simplified models are able to model the growth of a single hydraulic fracture into an initially intact, homogeneous rock mass, they are generally not able to model fracturing of heterogeneous rock formations, or to account for interactions between multiple induced fractures, or between an induced fracture and pre-existing natural fractures. We have developed a numerical finite-element model for hydraulic fracturing that does not suffer from any of the limitations mentioned above. The model accounts for fluid flow within a fracture, the propagation of the fracture, and the leak-off of fluid from the fracture into the host rock. Fluid flow through the permeable rock matrix is modelled using Darcy's law, and is coupled with the laminar flow within the fracture. Fractures are discretely modelled in the three-dimensional mesh. Growth of a fracture is modelled using the concepts of linear elastic fracture mechanics (LEFM), with the onset and direction of growth based on stress intensity factors that are computed for arbitrary tetrahedral meshes. The model has been verified against several analytical solutions available in the literature for plane-strain (2D) and penny-shaped (3D) fractures, for various regimes of domination: viscosity, toughness, storage and leak-off. The interaction of the hydraulically driven fracture with pre-existing fractures and other fluid-driven fractures in terms of fluid leak-off, stress interaction and fracture arrest is investigated and the results are presented. Finally, some preliminary results are presented regarding the interaction of a hydraulically-induced fracture with a set of pre-existing natural fractures.

FRACTURING FLUID CHARACTERIZATION FACILITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Subhash Shah

2000-08-01

Hydraulic fracturing technology has been successfully applied for well stimulation of low and high permeability reservoirs for numerous years. Treatment optimization and improved economics have always been the key to the success and it is more so when the reservoirs under consideration are marginal. Fluids are widely used for the stimulation of wells. The Fracturing Fluid Characterization Facility (FFCF) has been established to provide the accurate prediction of the behavior of complex fracturing fluids under downhole conditions. The primary focus of the facility is to provide valuable insight into the various mechanisms that govern the flow of fracturing fluids andmore » slurries through hydraulically created fractures. During the time between September 30, 1992, and March 31, 2000, the research efforts were devoted to the areas of fluid rheology, proppant transport, proppant flowback, dynamic fluid loss, perforation pressure losses, and frictional pressure losses. In this regard, a unique above-the-ground fracture simulator was designed and constructed at the FFCF, labeled ''The High Pressure Simulator'' (HPS). The FFCF is now available to industry for characterizing and understanding the behavior of complex fluid systems. To better reflect and encompass the broad spectrum of the petroleum industry, the FFCF now operates under a new name of ''The Well Construction Technology Center'' (WCTC). This report documents the summary of the activities performed during 1992-2000 at the FFCF.« less

Drainage and Stratification Kinetics of Foam Films

NASA Astrophysics Data System (ADS)

Zhang, Yiran; Sharma, Vivek

2014-03-01

Baking bread, brewing cappuccino, pouring beer, washing dishes, shaving, shampooing, whipping eggs and blowing bubbles all involve creation of aqueous foam films. Foam lifetime, drainage kinetics and stability are strongly influenced by surfactant type (ionic vs non-ionic), and added proteins, particles or polymers modify typical responses. The rate at which fluid drains out from a foam film, i.e. drainage kinetics, is determined in the last stages primarily by molecular interactions and capillarity. Interestingly, for certain low molecular weight surfactants, colloids and polyelectrolyte-surfactant mixtures, a layered ordering of molecules, micelles or particles inside the foam films leads to a stepwise thinning phenomena called stratification. Though stratification is observed in many confined systems including foam films containing particles or polyelectrolytes, films containing globular proteins seem not to show this behavior. Using a Scheludko-type cell, we experimentally study the drainage and stratification kinetics of horizontal foam films formed by protein-surfactant mixtures, and carefully determine how the presence of proteins influences the hydrodynamics and thermodynamics of foam films.

Dynamics of foam flow in porous media in the presence of oil

NASA Astrophysics Data System (ADS)

Shokri, N.; Osei-Bonsu, K.

2016-12-01

Foams demonstrate great potential for fluid displacement in porous media which is important in a number of subsurface operations such as the enhanced oil recovery and soil remediation. The application of foam in these processes is down to its unique ability to reduce gas mobility by increasing its effective viscosity and to divert gas to un-swept low permeability zones in porous media [1-4]. To investigate the fundamental aspects of foam flow in porous media, we have conducted a systematic series of experiment using a well-characterised porous medium manufactured by a high resolution 3D printer. This enabled us to design and control the properties of porous media with high accuracy. The model porous medium was initially saturated with oil. Then the pre-generated foam was injected into the model at well-defined injection rates to displace oil. The dynamics of foam-oil displacement in porous media was recorded using a digital camera controlled by a computer [5]. The recorded images were analysed in MATLAB to determine the dynamics of foam-oil displacement under different boundary conditions. Effects of the type of oil, foam quality and foam flow rate were investigated. Our results reveal that generation of stable foam is delayed in the presence of light oil in the porous medium compared to the heavy oil. Furthermore, higher foam quality appears to be less stable in the presence of oil lowering its recovery efficiency. Pore-scale inspection of foam-oil patterns formed during displacement revealed formation of a more stable front in the case of lower foam quality which affected the oil recovery efficiency. This study extends the physical understanding of governing mechanisms controlling oil displacement by foam in porous media. Grassia, P., E. Mas-Hernandez, N. Shokri, S.J. Cox, G. Mishuris, W.R. Rossen (2014), J. Fluid Mech., 751, 346-405. Grassia, P., C. Torres-Ulloa, S. Berres, E. Mas-Hernandez, N. Shokri (2016), European Physical Journal E, 39 (4), 42. Mas-Hernandez, E., P. Grassia, N. Shokri (2015), Colloids and Surfaces A: Physicochem. Eng. Aspects, 473, 123-132. Osei-Bonsu, K., N. Shokri, P. Grassia (2015), Colloids and Surfaces A: Physicochem. Eng. Aspects, 481, 514-526. Osei-Bonsu, K., N. Shokri, P. Grassia (2016), J. Colloid Interface Sci., 462, 288-296.

SURFACTANT BASED ENHANCED OIL RECOVERY AND FOAM MOBILITY CONTROL

DOE Office of Scientific and Technical Information (OSTI.GOV)

George J. Hirasaki; Clarence A. Miller; Gary A. Pope

2004-07-01

Surfactant flooding has the potential to significantly increase recovery over that of conventional waterflooding. The availability of a large number of surfactants makes it possible to conduct a systematic study of the relation between surfactant structure and its efficacy for oil recovery. Also, the addition of an alkali such as sodium carbonate makes possible in situ generation of surfactant and significant reduction of surfactant adsorption. In addition to reduction of interfacial tension to ultra-low values, surfactants and alkali can be designed to alter wettability to enhance oil recovery. An alkaline surfactant process is designed to enhance spontaneous imbibition in fractured,more » oil-wet, carbonate formations. It is able to recover oil from dolomite core samples from which there was no oil recovery when placed in formation brine. Mobility control is essential for surfactant EOR. Foam is evaluted to improve the sweep efficiency of surfactant injected into fractured reservoirs. UTCHEM is a reservoir simulator specially designed for surfactant EOR. A dual-porosity version is demonstrated as a potential scale-up tool for fractured reservoirs.« less

Determination of the effect of formation water on fracture-fluid cleanup

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1998-03-01

Understanding hydraulic-fracture cleanup is essential for improving well stimulation. Residual gel damages fracture conductivity, shortens effective fracture half-length, and limits well productivity. The drive to develop fluids, additives, and procedures that minimize this damage continues to be a dominant theme in fracture-fluid-development programs. Fracture cleanup is a complex problem, and many parameters (e.g., fluid system, job design, flowback procedure, and reservoir conditions) can influence polymer and fluid recovery efficiencies. Often, specific products and methods that work well in one reservoir have little effect in another. Systematic analysis of fluid and polymer returns after a treatment is completed is the onlymore » way to quantify fracture cleanup. This is referred to as flowback analysis. This paper discusses a flowback-analysis field study on large hydraulic-fracturing treatments in the Taylor zone of the Cotton Valley formation in east Texas. This is a low-permeability (approximately 0.01 md) tight gas formation. It is a heterogeneous zone with layers of productive sandstone interspersed with relatively impermeable layers of shale. A typical well in this field initially produces approximately 0.75 to 1.3 MMcf/D gas and 35 to 40 bbl of water/MMcf of gas. The returns from 10 wells in this field were analyzed thoroughly.« less

Streaming potential modeling in fractured rock: Insights into the identification of hydraulically active fractures

NASA Astrophysics Data System (ADS)

Roubinet, D.; Linde, N.; Jougnot, D.; Irving, J.

2016-05-01

Numerous field experiments suggest that the self-potential (SP) geophysical method may allow for the detection of hydraulically active fractures and provide information about fracture properties. However, a lack of suitable numerical tools for modeling streaming potentials in fractured media prevents quantitative interpretation and limits our understanding of how the SP method can be used in this regard. To address this issue, we present a highly efficient two-dimensional discrete-dual-porosity approach for solving the fluid flow and associated self-potential problems in fractured rock. Our approach is specifically designed for complex fracture networks that cannot be investigated using standard numerical methods. We then simulate SP signals associated with pumping conditions for a number of examples to show that (i) accounting for matrix fluid flow is essential for accurate SP modeling and (ii) the sensitivity of SP to hydraulically active fractures is intimately linked with fracture-matrix fluid interactions. This implies that fractures associated with strong SP amplitudes are likely to be hydraulically conductive, attracting fluid flow from the surrounding matrix.

Experimental Analysis of the Role of Fluid Transport Properties in Fluid-Induced Fracture Initiation and Propagation

NASA Astrophysics Data System (ADS)

Boutt, D.; McPherson, B. J.; Cook, B. K.; Goodwin, L. B.; Williams, J. R.; Lee, M. Y.; Patteson, R.

2003-12-01

It is well known that pore fluid pressure fundamentally influences a rock's mechanical response to stress. However, most measures of the mechanical behavior of rock (e.g. shear strength, Young's modulus) do not incorporate, either explicitly or implicitly, pore fluid pressure or transport properties of rock. Current empirical and theoretical criteria that define the amount of stress a given body of rock can support before fracturing also lack a direct connection between fluid transport and mechanical properties. Our research goal is to use laboratory experimental results to elucidate correlations between rock transport properties and fracture behavior under idealized loading conditions. In strongly coupled fluid-solid systems the evolution of the solid framework is influenced by the fluid and vice versa. These couplings often result in changes of the bulk material properties (i.e. permeability and failure strength) with respect to the fluid's ability to move through the solid and the solids ability to transmit momentum. Feedbacks between fluid and solid framework ultimately play key roles in understanding the spatial and temporal evolution of the coupled fluid-solid system. Discretely coupled models of fluid and solid mechanics were developed a priori to design an experimental approach for testing the role of fluid transport parameters in rock fracture. The experimental approach consists of first loading a fluid saturated cylindrical rock specimen under hydrostatic conditions and then applying a differential stress such that the maximum stress is perpendicular to the cylinder long axis. At the beginning of the test the minimum stress and the fluid pressure are dropped at the same time such that the resulting difference in the initial fluid pressure and the final fluid pressure is greater than the final minimum stress. These loading conditions should produce a fluid driven tensile fracture that is perpendicular to the cylinder long axis. Initial analyses using numerical simulations with similar boundary conditions suggest that resulting fracture propagation rates and fracture spacing are controlled by the rocks hydraulic diffusivity. Modeled rocks with higher permeability had fractures with larger apertures, more localized deformation, and greater fracture spacing. Intuitively, these results are consistent with permeability controlling the time required for pressure to come to equilibrium with the new boundary conditions. Finally, more general goals of this research include using these core-scale experimental data and discrete simulation results to calibrate larger-scale, more traditional continuum models of geologic deformation.

Fluid Pocket Generation in Response to Heterogeneous Reactivity of a Rock Fracture Under Hydrothermal Conditions

NASA Astrophysics Data System (ADS)

Okamoto, A.; Tanaka, H.; Watanabe, N.; Saishu, H.; Tsuchiya, N.

2017-10-01

Fractures are the location of various water-rock interactions within the Earth's crust; however, the impact of the chemical heterogeneity of fractures on hydraulic properties is poorly understood. We conducted flow-through experiments on the dissolution of granite with a tensile fracture at 350°C and fluid pressure of 20 MPa with confining pressure of 40 MPa. The aperture structures were evaluated by X-ray computed tomography before and after the experiments. Under the experimental conditions, quartz grains dissolve rapidly to produce grain-scale pockets on the fracture surface, whereas altered feldspar grains act as asperities to sustain the open cavities. The fracture contained gouge with large surface area. The feedback between fluid flow and the rapid dissolution of gouge material produced large fluid pockets, whereas permeability did not always increase significantly. Such intense hydrological-chemical interactions could strongly influence the porosity-permeability relationship of fractured reservoirs in the crust.

Disclosure of hydraulic fracturing fluid chemical additives: analysis of regulations.

PubMed

Maule, Alexis L; Makey, Colleen M; Benson, Eugene B; Burrows, Isaac J; Scammell, Madeleine K

2013-01-01

Hydraulic fracturing is used to extract natural gas from shale formations. The process involves injecting into the ground fracturing fluids that contain thousands of gallons of chemical additives. Companies are not mandated by federal regulations to disclose the identities or quantities of chemicals used during hydraulic fracturing operations on private or public lands. States have begun to regulate hydraulic fracturing fluids by mandating chemical disclosure. These laws have shortcomings including nondisclosure of proprietary or "trade secret" mixtures, insufficient penalties for reporting inaccurate or incomplete information, and timelines that allow for after-the-fact reporting. These limitations leave lawmakers, regulators, public safety officers, and the public uninformed and ill-prepared to anticipate and respond to possible environmental and human health hazards associated with hydraulic fracturing fluids. We explore hydraulic fracturing exemptions from federal regulations, as well as current and future efforts to mandate chemical disclosure at the federal and state level.

Hydraulic fracture height limits and fault interactions in tight oil and gas formations

NASA Astrophysics Data System (ADS)

Flewelling, Samuel A.; Tymchak, Matthew P.; Warpinski, Norm

2013-07-01

widespread use of hydraulic fracturing (HF) has raised concerns about potential upward migration of HF fluid and brine via induced fractures and faults. We developed a relationship that predicts maximum fracture height as a function of HF fluid volume. These predictions generally bound the vertical extent of microseismicity from over 12,000 HF stimulations across North America. All microseismic events were less than 600 m above well perforations, although most were much closer. Areas of shear displacement (including faults) estimated from microseismic data were comparatively small (radii on the order of 10 m or less). These findings suggest that fracture heights are limited by HF fluid volume regardless of whether the fluid interacts with faults. Direct hydraulic communication between tight formations and shallow groundwater via induced fractures and faults is not a realistic expectation based on the limitations on fracture height growth and potential fault slip.

Comparison/Validation Study of Lattice Boltzmann and Navier Stokes for Various Benchmark Applications: Report 1 in Discrete Nano-Scale Mechanics and Simulations Series

DTIC Science & Technology

2014-09-15

solver, OpenFOAM version 2.1.‡ In particular, the incompressible laminar flow equations (Eq. 6-8) were solved in conjunction with the pressure im- plicit...central differencing and upwinding schemes, respectively. Since the OpenFOAM code is inherently transient, steady-state conditions were ob- tained...collaborative effort between Kitware and Los Alamos National Laboratory. ‡ OpenFOAM is a free, open-source computational fluid dynamics software developed

Foam structure :from soap froth to solid foams.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kraynik, Andrew Michael

2003-01-01

The properties of solid foams depend on their structure, which usually evolves in the fluid state as gas bubbles expand to form polyhedral cells. The characteristic feature of foam structure-randomly packed cells of different sizes and shapes-is examined in this article by considering soap froth. This material can be modeled as a network of minimal surfaces that divide space into polyhedral cells. The cell-level geometry of random soap froth is calculated with Brakke's Surface Evolver software. The distribution of cell volumes ranges from monodisperse to highly polydisperse. Topological and geometric properties, such as surface area and edge length, of themore » entire foam and individual cells, are discussed. The shape of struts in solid foams is related to Plateau borders in liquid foams and calculated for different volume fractions of material. The models of soap froth are used as templates to produce finite element models of open-cell foams. Three-dimensional images of open-cell foams obtained with x-ray microtomography allow virtual reconstruction of skeletal structures that compare well with the Surface Evolver simulations of soap-froth geometry.« less

Environmentally Friendly, Rheoreversible, Hydraulic-fracturing Fluids for Enhanced Geothermal Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shao, Hongbo; Kabilan, Senthil; Stephens, Sean A.

Cost-effective creation of high-permeability reservoirs inside deep crystalline bedrock is the primary challenge for the feasibility of enhanced geothermal systems (EGS). Current reservoir stimulation entails adverse environmental impacts and substantial economic costs due to the utilization of large volumes of water “doped” with chemicals including rheology modifiers, scale and corrosion inhibitors, biocides, friction reducers among others where, typically, little or no information of composition and toxicity is disclosed. An environmentally benign, CO2-activated, rheoreversible fracturing fluid has recently been developed that significantly enhances rock permeability at effective stress significantly lower than current technology. We evaluate the potential of this novel fracturingmore » fluid for application on geothermal sites under different chemical and geomechanical conditions, by performing laboratory-scale fracturing experiments with different rock sources under different confining pressures, temperatures, and pH environments. The results demonstrate that CO2-reactive aqueous solutions of environmentally amenable Polyallylamine (PAA) represent a highly versatile fracturing fluid technology. This fracturing fluid creates/propagates fracture networks through highly impermeable crystalline rock at significantly lower effective stress as compared to control experiments where no PAA was present, and permeability enhancement was significantly increased for PAA compared to conventional hydraulic fracturing controls. This was evident in all experiments, including variable rock source/type, operation pressure and temperature (over the entire range for EGS applications), as well as over a wide range of formation-water pH values. This versatile novel fracturing fluid technology represents a great alternative to industrially available fracturing fluids for cost-effective and competitive geothermal energy production.« less

Fluid transport in reaction induced fractures

NASA Astrophysics Data System (ADS)

Ulven, Ole Ivar; Sun, WaiChing; Malthe-Sørenssen, Anders

2015-04-01

The process of fracture formation due to a volume increasing chemical reaction has been studied in a variety of different settings, e.g. weathering of dolerites by Røyne et al. te{royne}, serpentinization and carbonation of peridotite by Rudge et al. te{rudge} and replacement reactions in silica-poor igneous rocks by Jamtveit et al. te{jamtveit}. It is generally assumed that fracture formation will increase the net permeability of the rock, and thus increase the reactant transport rate and subsequently the total rate of material conversion, as summarised by Kelemen et al. te{kelemen}. Ulven et al. te{ulven_1} have shown that for fluid-mediated processes the ratio between chemical reaction rate and fluid transport rate in bulk rock controls the fracture pattern formed, and Ulven et al. te{ulven_2} have shown that instantaneous fluid transport in fractures lead to a significant increase in the total rate of the volume expanding process. However, instantaneous fluid transport in fractures is clearly an overestimate, and achievable fluid transport rates in fractures have apparently not been studied in any detail. Fractures cutting through an entire domain might experience relatively fast advective reactant transport, whereas dead-end fractures will be limited to diffusion of reactants in the fluid, internal fluid mixing in the fracture or capillary flow into newly formed fractures. Understanding the feedback process between fracture formation and permeability changes is essential in assessing industrial scale CO2 sequestration in ultramafic rock, but little is seemingly known about how large the permeability change will be in reaction-induced fracturing. In this work, we study the feedback between fracture formation during volume expansion and fluid transport in different fracture settings. We combine a discrete element model (DEM) describing a volume expanding process and the related fracture formation with different models that describe the fluid transport in the fractures. This provides new information on how much reaction induced fracturing might accelerate a volume expanding process. Jamtveit, B, Putnis, C. V., and Malthe-Sørenssen, A., ``Reaction induced fracturing during replacement processes,'' Contrib. Mineral Petrol. 157, 2009, pp. 127 - 133. Kelemen, P., Matter, J., Streit, E. E., Rudge, J. F., Curry, W. B., and Blusztajn, J., ``Rates and Mechanisms of Mineral Carbonation in Peridotite: Natural Processes and Recipes for Enhanced, in situ CO2 Capture and Storage,'' Annu. Rev. Earth Planet. Sci. 2011. 39:545 - 76. Rudge, J. F., Kelemen, P. B., and Spiegelman, M., ``A simple model of reaction induced cracking applied to serpentinization and carbonation of peridotite,'' Earth Planet. Sc. Lett. 291, Issues 1-4, 2010, pp. 215 - 227. Røyne, A., Jamtveit, B., and Malthe-Sørenssen, A., ``Controls on rock weathering rates by reaction-induced hierarchial fracturing,'' Earth Planet. Sc. Lett. 275, 2008, pp. 364 - 369. Ulven, O. I., Storheim, H., Austrheim, H., and Malthe-Sørenssen, A. ``Fracture initiation during volume increasing reactions in rocks and applications for CO2 sequestration'', Earth Planet. Sc. Lett. 389C, 2014, pp. 132 - 142, doi:10.1016/j.epsl.2013.12.039. Ulven, O. I., Jamtveit, B., and Malthe-Sørenssen, A., ``Reaction-driven fracturing of porous rock'', J. Geophys. Res. Solid Earth 119, 2014, doi:10.1002/2014JB011102.

A simplified model to evaluate the effect of fluid rheology on non-Newtonian flow in variable aperture fractures

NASA Astrophysics Data System (ADS)

Felisa, Giada; Ciriello, Valentina; Longo, Sandro; Di Federico, Vittorio

2017-04-01

Modeling of non-Newtonian flow in fractured media is essential in hydraulic fracturing operations, largely used for optimal exploitation of oil, gas and thermal reservoirs. Complex fluids interact with pre-existing rock fractures also during drilling operations, enhanced oil recovery, environmental remediation, and other natural phenomena such as magma and sand intrusions, and mud volcanoes. A first step in the modeling effort is a detailed understanding of flow in a single fracture, as the fracture aperture is typically spatially variable. A large bibliography exists on Newtonian flow in single, variable aperture fractures. Ultimately, stochastic modeling of aperture variability at the single fracture scale leads to determination of the flowrate under a given pressure gradient as a function of the parameters describing the variability of the aperture field and the fluid rheological behaviour. From the flowrate, a flow, or 'hydraulic', aperture can then be derived. The equivalent flow aperture for non-Newtonian fluids of power-law nature in single, variable aperture fractures has been obtained in the past both for deterministic and stochastic variations. Detailed numerical modeling of power-law fluid flow in a variable aperture fracture demonstrated that pronounced channelization effects are associated to a nonlinear fluid rheology. The availability of an equivalent flow aperture as a function of the parameters describing the fluid rheology and the aperture variability is enticing, as it allows taking their interaction into account when modeling flow in fracture networks at a larger scale. A relevant issue in non-Newtonian fracture flow is the rheological nature of the fluid. The constitutive model routinely used for hydro-fracturing modeling is the simple, two-parameter power-law. Yet this model does not characterize real fluids at low and high shear rates, as it implies, for shear-thinning fluids, an apparent viscosity which becomes unbounded for zero shear rate and tends to zero for infinite shear rate. On the contrary, the four-parameter Carreau constitutive equation includes asymptotic values of the apparent viscosity at those limits; in turn, the Carreau rheological equation is well approximated by the more tractable truncated power-law model. Results for flow of such fluids between parallel walls are already available. This study extends the adoption of the truncated power-law model to variable aperture fractures, with the aim of understanding the joint influence of rheology and aperture spatial variability. The aperture variation, modeled within a stochastic or deterministic framework, is taken to be one-dimensional and perpendicular to the flow direction; for stochastic modeling, the influence of different distribution functions is examined. Results are then compared with those obtained for pure power-law fluids for different combinations of model parameters. It is seen that the adoption of the pure power law model leads to significant overestimation of the flowrate with respect to the truncated model, more so for large external pressure gradient and/or aperture variability.

The fluid mechanics of channel fracturing flows: experiment

NASA Astrophysics Data System (ADS)

Rashedi, Ahmadreza; Tucker, Zachery; Ovarlez, Guillaume; Hormozi, Sarah

2017-11-01

We show our preliminary experimental results on the role of fluid mechanics in channel fracturing flows, particularly yield stress fracturing fluids. Recent trends in the oil industry have included the use of cyclic pumping of a proppant slurry interspersed with a yield stress fracturing fluid, which is found to increase wells productivity, if particles disperse in a certain fashion. Our experimental study aims to investigate the physical mechanisms responsible for dispersing the particles (proppant) within a yield stress carrier fluid, and to measure the dispersion of proppant slugs in various fracturing regimes. To this end we have designed and built a unique experimental setup that resembles a fracture configuration coupled with a particle image/tracking velocimetry setup operating at micro to macro dimensions. Moreover, we have designed optically engineered suspensions of complex fluids with tunable yield stress and consistency, well controlled density match-mismatch properties and refractive indices for both X-rays and visible lights. We present our experimental system and preliminary results. NSF (Grant No. CBET-1554044- CAREER), ACS PRF (Grant No. 55661-DNI9).

Group invariant solution for a pre-existing fracture driven by a power-law fluid in impermeable rock

NASA Astrophysics Data System (ADS)

Fareo, A. G.; Mason, D. P.

2013-12-01

The effect of power-law rheology on hydraulic fracturing is investigated. The evolution of a two-dimensional fracture with non-zero initial length and driven by a power-law fluid is analyzed. Only fluid injection into the fracture is considered. The surrounding rock mass is impermeable. With the aid of lubrication theory and the PKN approximation a partial differential equation for the fracture half-width is derived. Using a linear combination of the Lie-point symmetry generators of the partial differential equation, the group invariant solution is obtained and the problem is reduced to a boundary value problem for an ordinary differential equation. Exact analytical solutions are derived for hydraulic fractures with constant volume and with constant propagation speed. The asymptotic solution near the fracture tip is found. The numerical solution for general working conditions is obtained by transforming the boundary value problem to a pair of initial value problems. Throughout the paper, hydraulic fracturing with shear thinning, Newtonian and shear thickening fluids are compared.

Numerical Modeling of Complex Targets for High-Energy- Density Experiments with Ion Beams and other Drivers

DOE PAGES

Koniges, Alice; Liu, Wangyi; Lidia, Steven; ...

2016-04-01

We explore the simulation challenges and requirements for experiments planned on facilities such as the NDCX-II ion accelerator at LBNL, currently undergoing commissioning. Hydrodynamic modeling of NDCX-II experiments include certain lower temperature effects, e.g., surface tension and target fragmentation, that are not generally present in extreme high-energy laser facility experiments, where targets are completely vaporized in an extremely short period of time. Target designs proposed for NDCX-II range from metal foils of order one micron thick (thin targets) to metallic foam targets several tens of microns thick (thick targets). These high-energy-density experiments allow for the study of fracture as wellmore » as the process of bubble and droplet formation. We incorporate these physics effects into a code called ALE-AMR that uses a combination of Arbitrary Lagrangian Eulerian hydrodynamics and Adaptive Mesh Refinement. Inclusion of certain effects becomes tricky as we must deal with non-orthogonal meshes of various levels of refinement in three dimensions. A surface tension model used for droplet dynamics is implemented in ALE-AMR using curvature calculated from volume fractions. Thick foam target experiments provide information on how ion beam induced shock waves couple into kinetic energy of fluid flow. Although NDCX-II is not fully commissioned, experiments are being conducted that explore material defect production and dynamics.« less

Coupling Hydraulic Fracturing Propagation and Gas Well Performance for Simulation of Production in Unconventional Shale Gas Reservoirs

NASA Astrophysics Data System (ADS)

Wang, C.; Winterfeld, P. H.; Wu, Y. S.; Wang, Y.; Chen, D.; Yin, C.; Pan, Z.

2014-12-01

Hydraulic fracturing combined with horizontal drilling has made it possible to economically produce natural gas from unconventional shale gas reservoirs. An efficient methodology for evaluating hydraulic fracturing operation parameters, such as fluid and proppant properties, injection rates, and wellhead pressure, is essential for the evaluation and efficient design of these processes. Traditional numerical evaluation and optimization approaches are usually based on simulated fracture properties such as the fracture area. In our opinion, a methodology based on simulated production data is better, because production is the goal of hydraulic fracturing and we can calibrate this approach with production data that is already known. This numerical methodology requires a fully-coupled hydraulic fracture propagation and multi-phase flow model. In this paper, we present a general fully-coupled numerical framework to simulate hydraulic fracturing and post-fracture gas well performance. This three-dimensional, multi-phase simulator focuses on: (1) fracture width increase and fracture propagation that occurs as slurry is injected into the fracture, (2) erosion caused by fracture fluids and leakoff, (3) proppant subsidence and flowback, and (4) multi-phase fluid flow through various-scaled anisotropic natural and man-made fractures. Mathematical and numerical details on how to fully couple the fracture propagation and fluid flow parts are discussed. Hydraulic fracturing and production operation parameters, and properties of the reservoir, fluids, and proppants, are taken into account. The well may be horizontal, vertical, or deviated, as well as open-hole or cemented. The simulator is verified based on benchmarks from the literature and we show its application by simulating fracture network (hydraulic and natural fractures) propagation and production data history matching of a field in China. We also conduct a series of real-data modeling studies with different combinations of hydraulic fracturing parameters and present the methodology to design these operations with feedback of simulated production data. The unified model aids in the optimization of hydraulic fracturing design, operations, and production.

Performance evaluation of OpenFOAM on many-core architectures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brzobohatý, Tomáš; Říha, Lubomír; Karásek, Tomáš, E-mail: tomas.karasek@vsb.cz

In this article application of Open Source Field Operation and Manipulation (OpenFOAM) C++ libraries for solving engineering problems on many-core architectures is presented. Objective of this article is to present scalability of OpenFOAM on parallel platforms solving real engineering problems of fluid dynamics. Scalability test of OpenFOAM is performed using various hardware and different implementation of standard PCG and PBiCG Krylov iterative methods. Speed up of various implementations of linear solvers using GPU and MIC accelerators are presented in this paper. Numerical experiments of 3D lid-driven cavity flow for several cases with various number of cells are presented.

A Numerical Modeling Framework for Cohesive Sediment Transport Driven by Waves and Tidal Currents

DTIC Science & Technology

2012-09-30

for sediment transport. The successful extension to multi-dimensions is benefited from an open-source CFD package, OpenFOAM (www.openfoam.org). This...linz.at/Drupal/), which couples the fluid solver OpenFOAM with the Discrete Element Model (DEM) solver LIGGGHTS (an improved LAMMPS for granular flow

Electrical Conductivity Distributions in Discrete Fluid-Filled Fractures

NASA Astrophysics Data System (ADS)

James, S. C.; Ahmmed, B.; Knox, H. A.; Johnson, T.; Dunbar, J. A.

2017-12-01

It is commonly asserted that hydraulic fracturing enhances permeability by generating new fractures in the reservoir. Furthermore, it is assumed that in the fractured system predominant flow occurs in these newly formed and pre-existing fractures. Among the phenomenology that remains enigmatic are fluid distributions inside fractures. Therefore, determining fluid distribution and their associated temporal and spatial evolution in fractures is critical for safe and efficient hydraulic fracturing. Previous studies have used both forward modeling and inversion of electrical data to show that a geologic system consisting of fluid filled fractures has a conductivity distribution, where fractures act as electrically conductive bodies when the fluids are more conductive than the host material. We will use electrical inversion for estimating electrical conductivity distribution within multiple fractures from synthetic and measured data. Specifically, we will use data and well geometries from an experiment performed at Blue Canyon Dome in Socorro, NM, which was used as a study site for subsurface technology, engineering, and research (SubTER) funded by DOE. This project used a central borehole for energetically stimulating the system and four monitoring boreholes, emplaced in the cardinal directions. The electrical data taken during this project used 16 temporary electrodes deployed in the stimulation borehole and 64 permanent electrodes in the monitoring wells (16 each). We present results derived using E4D from scenarios with two discrete fractures, thereby discovering the electric potential response of both spatially and temporarily variant fluid distribution and the resolution of fluid and fracture boundaries. These two fractures have dimensions of 3m × 0.01m × 7m and are separated by 1m. These results can be used to develop stimulation and flow tests at the meso-scale that will be important for model validation. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525.

Natural thermal convection in fractured porous media

NASA Astrophysics Data System (ADS)

Adler, P. M.; Mezon, C.; Mourzenko, V.; Thovert, J. F.; Antoine, R.; Finizola, A.

2015-12-01

In the crust, fractures/faults can provide preferential pathways for fluid flow or act as barriers preventing the flow across these structures. In hydrothermal systems (usually found in fractured rock masses), these discontinuities may play a critical role at various scales, controlling fluid flows and heat transfer. The thermal convection is numerically computed in 3D fluid satured fractured porous media. Fractures are inserted as discrete objects, randomly distributed over a damaged volume, which is a fraction of the total volume. The fluid is assumed to satisfy Darcy's law in the fractures and in the porous medium with exchanges between them. All simulations were made for Rayleigh numbers (Ra) < 150 (hence, the fluid is in thermal equilibrium with the medium), cubic boxes and closed-top conditions. Checks were performed on an unfractured porous medium and the convection cells do start for the theoretical value of Ra, namely 4p². 2D convection was verified up to Ra=800. The influence of parameters such as fracture aperture (or fracture transmissivity), fracture density and fracture length is studied. Moreover, these models are compared to porous media with the same macroscopic permeability. Preliminary results show that the non-uniqueness associated with initial conditions which makes possible either 2D or 3D convection in porous media (Schubert & Straus 1979) is no longer true for fractured porous media (at least for 50

Numerical Simulation of Permeability Change in Wellbore Cement Fractures after Geomechanical Stress and Geochemical Reactions Using X-ray Computed Tomography Imaging.

PubMed

Kabilan, Senthil; Jung, Hun Bok; Kuprat, Andrew P; Beck, Anthon N; Varga, Tamas; Fernandez, Carlos A; Um, Wooyong

2016-06-21

X-ray microtomography (XMT) imaging combined with three-dimensional (3D) computational fluid dynamics (CFD) modeling technique was used to study the effect of geochemical and geomechanical processes on fracture permeability in composite Portland cement-basalt caprock core samples. The effect of fluid density and viscosity and two different pressure gradient conditions on fracture permeability was numerically studied by using fluids with varying density and viscosity and simulating two different pressure gradient conditions. After the application of geomechanical stress but before CO2-reaction, CFD revealed fluid flow increase, which resulted in increased fracture permeability. After CO2-reaction, XMT images displayed preferential precipitation of calcium carbonate within the fractures in the cement matrix and less precipitation in fractures located at the cement-basalt interface. CFD estimated changes in flow profile and differences in absolute values of flow velocity due to different pressure gradients. CFD was able to highlight the profound effect of fluid viscosity on velocity profile and fracture permeability. This study demonstrates the applicability of XMT imaging and CFD as powerful tools for characterizing the hydraulic properties of fractures in a number of applications like geologic carbon sequestration and storage, hydraulic fracturing for shale gas production, and enhanced geothermal systems.

Numerical Simulation of Permeability Change in Wellbore Cement Fractures after Geomechanical Stress and Geochemical Reactions Using X-ray Computed Tomography Imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kabilan, Senthil; Jung, Hun Bok; Kuprat, Andrew P.

X-ray microtomography (XMT) imaging combined with a three-dimensional (3D) computational fluid dynamics (CFD) modeling technique was used to study the effect of geochemical and geomechanical processes on fracture properties in composite Portland cement–basalt caprock core samples. The effect of fluid properties and flow conditions on fracture permeability was numerically studied by using fluids with varying physical properties and simulating different pressure conditions. CFD revealed that the application of geomechanical stress led to increased fluid flow, which resulted in increased fracture permeability. After CO2-reaction, XMT images displayed preferential precipitation of calcium carbonate within the fractures in the cement matrix and lessmore » precipitation in fractures located at the cement–basalt interface. CFD predicted changes in flow characteristics and differences in absolute values of flow properties due to different pressure gradients. CFD was able to highlight the profound effect of fluid properties on flow characteristics and hydraulic properties of fractures. This study demonstrates the applicability of XMT imaging and CFD as powerful tools for characterizing the hydraulic properties of fractures in a number of applications like geologic carbon sequestration and storage, hydraulic fracturing for shale gas production, and enhanced geothermal systems.« less

DEVELOPMENT OF AN IMPROVED SIMULATOR FOR CHEMICAL AND MICROBIAL IOR METHODS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gary A. Pope; Kamy Sepehrnoori; Mojdeh Delshad

2001-10-01

This is the final report of a three-year research project on further development of a chemical and microbial improved oil recovery reservoir simulator. The objective of this research was to extend the capability of an existing simulator (UTCHEM) to improved oil recovery methods which use surfactants, polymers, gels, alkaline chemicals, microorganisms and foam as well as various combinations of these in both conventional and naturally fractured oil reservoirs. The first task was the addition of a dual-porosity model for chemical IOR in naturally fractured oil reservoirs. They formulated and implemented a multiphase, multicomponent dual porosity model for enhanced oil recoverymore » from naturally fractured reservoirs. The multiphase dual porosity model was tested against analytical solutions, coreflood data, and commercial simulators. The second task was the addition of a foam model. They implemented a semi-empirical surfactant/foam model in UTCHEM and validated the foam model by comparison with published laboratory data. The third task addressed several numerical and coding enhancements that will greatly improve its versatility and performance. Major enhancements were made in UTCHEM output files and memory management. A graphical user interface to set up the simulation input and to process the output data on a Windows PC was developed. New solvers for solving the pressure equation and geochemical system of equations were implemented and tested. A corner point grid geometry option for gridding complex reservoirs was implemented and tested. Enhancements of physical property models for both chemical and microbial IOR simulations were included in the final task of this proposal. Additional options for calculating the physical properties such as relative permeability and capillary pressure were added. A microbiological population model was developed and incorporated into UTCHEM. They have applied the model to microbial enhanced oil recovery (MEOR) processes by including the capability of permeability reduction due to biomass growth and retention. The formations of bio-products such as surfactant and polymer surfactant have also been incorporated.« less

Post-processing of polymer foam tissue scaffolds with high power ultrasound: a route to increased pore interconnectivity, pore size and fluid transport.

PubMed

Watson, N J; Johal, R K; Glover, Z; Reinwald, Y; White, L J; Ghaemmaghami, A M; Morgan, S P; Rose, F R A J; Povey, M J W; Parker, N G

2013-12-01

The aim of this work is to demonstrate that the structural and fluidic properties of polymer foam tissue scaffolds, post-fabrication but prior to the introduction of cells, can be engineered via exposure to high power ultrasound. Our analysis is supported by measurements of fluid uptake during insonification and imaging of the scaffold microstructure via X-ray computed tomography, scanning electron microscopy and acoustic microscopy. The ultrasonic treatment is performed with a frequency of 30 kHz, average intensities up to 80,000 Wm(-2) and exposure times up to 20 h. The treatment is found to increase the mean pore size by over 10%. More striking is the improvement in fluid uptake: for scaffolds with only 40% water uptake via standard immersion techniques, we can routinely achieve full saturation of the scaffold over approximately one hour of exposure. These desirable modifications occur with negligible loss of scaffold integrity and mass, and are optimized when the ultrasound treatment is coupled to a pre-wetting stage with ethanol. Our findings suggest that high power ultrasound is highly targeted towards flow obstructions in the scaffold architecture, thereby providing an efficient means to promote pore interconnectivity and fluid transport in thick foam tissue scaffolds. © 2013.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seales, Maxian B.; Dilmore, Robert; Ertekin, Turgay

Fracture fluid comprises fresh water, proppant, and a small percentage of other additives, which support the hydraulic fracturing process. Excluding situations in which flowback water is recycled and reused, total dissolve solids in fracture fluid is limited to the fluid additives, such as potassium chloride (1-7 weight percent KCL), which is used as a clay stabilizer to minimize clay swelling, and clay particle migration. However, the composition of recovered fluid, especially as it relates to the total dissolve solids (TDS), is always substantially different than the injected fracture fluid. The ability to predict flowback water volume and composition is usefulmore » when planning for the management or reuse of this aqueous byproduct stream. In this work, an ion transport and halite dissolution model was coupled with a fully implicit, dual porosity, numerical simulator, to study the source of the excess solutes in flowback water, and to predict the concentration of both Na+ and Cl- species seen in recovered water. The results showed that mixing alone, between the injected fracture fluid and concentrated in situ formation brine, could not account for the substantial rise in TDS seen in flowback water. Instead, the results proved that halite dissolution is a major contributor to the change in TDS seen in fracture fluid during injection and recovery. Halite dissolution can account for as much as 81% of Cl- and 86.5% of Na+ species seen in 90-day flowback water; mixing, between the injected fracture fluid and in situ concentrated brine, accounts for approximately 19% Cl- and 13% Na+.« less

Overview of Chronic Oral Toxicity Values for Chemicals Present in Hydraulic Fracturing Fluids, Flowback and Produced Waters

EPA Pesticide Factsheets

as part of EPA's Hydraulic Fracturing Drinking Water Assessment, EPA is summarizing existing toxicity data for chemicals reported to be used in hydraulic fracturing fluids and/or found in flowback or produced waters from hydraulically fractured wells

Ultrasonic measurements of the reflection coefficient at a water/polyurethane foam interface.

PubMed

Sagers, Jason D; Haberman, Michael R; Wilson, Preston S

2013-09-01

Measured ultrasonic reflection coefficients as a function of normal incidence angle are reported for several samples of polyurethane foam submerged in a water bath. Three reflection coefficient models are employed as needed in this analysis to approximate the measured data: (1) an infinite plane wave impinging on an elastic halfspace, (2) an infinite plane wave impinging on a single fluid layer overlying a fluid halfspace, and (3) a finite acoustic beam impinging on an elastic halfspace. The compressional wave speed in each sample is calculated by minimizing the sum of squared error (SSE) between the measured and modeled data.

Fracture Fluid Additive and Formation Degradations

EPA Pesticide Factsheets

This presentation is on reactions that describe the degradation of fracturing fluids & formations during the hydraulic fracturing process & the clean‐up period. It contains a description of primary chemical reaction controls, & common degradation reactions

A shape memory foam composite with enhanced fluid uptake and bactericidal properties as a hemostatic agent.

PubMed

Landsman, T L; Touchet, T; Hasan, S M; Smith, C; Russell, B; Rivera, J; Maitland, D J; Cosgriff-Hernandez, E

2017-01-01

Uncontrolled hemorrhage accounts for more than 30% of trauma deaths worldwide. Current hemostatic devices focus primarily on time to hemostasis, but prevention of bacterial infection is also critical for improving survival rates. In this study, we sought to improve on current devices used for hemorrhage control by combining the large volume-filling capabilities and rapid clotting of shape memory polymer (SMP) foams with the swelling capacity of hydrogels. In addition, a hydrogel composition was selected that readily complexes with elemental iodine to impart bactericidal properties to the device. The focus of this work was to verify that the advantages of each respective material (SMP foam and hydrogel) are retained when combined in a composite device. The iodine-doped hydrogel demonstrated an 80% reduction in bacteria viability when cultured with a high bioburden of Staphylococcus aureus. Hydrogel coating of the SMP foam increased fluid uptake by 19× over the uncoated SMP foam. The composite device retained the shape memory behavior of the foam with more than 15× volume expansion after being submerged in 37°C water for 15 min. Finally, the expansion force of the composite was tested to assess potential tissue damage within the wound during device expansion. Expansion forces did not exceed 0.6N, making tissue damage during device expansion unlikely, even when the expanded device diameter is substantially larger than the target wound site. Overall, the enhanced fluid uptake and bactericidal properties of the shape memory foam composite indicate its strong potential as a hemostatic agent to treat non-compressible wounds. No hemostatic device currently used in civilian and combat trauma situations satisfies all the desired criteria for an optimal hemostatic wound dressing. The research presented here sought to improve on current devices by combining the large volume-filling capabilities and rapid clotting of shape memory polymer (SMP) foams with the swelling capacity of hydrogels. In addition, a hydrogel composition was selected that readily complexes with elemental iodine to impart bactericidal properties to the device. The focus of this work was to verify that the advantages of each respective material are retained when combined into a composite device. This research opens the door to generating novel composites with a focus on both hemostasis, as well as wound healing and microbial prevention. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Evolution of a fracture network in an elastic medium with internal fluid generation and expulsion

NASA Astrophysics Data System (ADS)

Kobchenko, Maya; Hafver, Andreas; Jettestuen, Espen; Renard, François; Galland, Olivier; Jamtveit, Bjørn; Meakin, Paul; Dysthe, Dag Kristian

2014-11-01

A simple and reproducible analog experiment was used to simulate fracture formation in a low-permeability elastic solid during internal fluid/gas production, with the objective of developing a better understanding of the mechanisms that control the dynamics of fracturing, fracture opening and closing, and fluid transport. In the experiment, nucleation, propagation, and coalescence of fractures within an elastic gelatin matrix, confined in a Hele-Shaw cell, occurred due to CO2 production via fermentation of sugar, and it was monitored by optical means. We first quantified how a fracture network develops, and then how intermittent fluid transport is controlled by the dynamics of opening and closing of fractures. The gas escape dynamics exhibited three characteristic behaviors: (1) Quasiperiodic release of gas with a characteristic frequency that depends on the gas production rate but not on the system size. (2) A 1 /f power spectrum for the fluctuations in the total open fracture area over an intermediate range of frequencies (f ), which we attribute to collective effects caused by interaction between fractures in the drainage network. (3) A 1 /f2 power spectrum was observed at high frequencies, which can be explained by the characteristic behavior of single fractures.

Characterization of the Oriskany and Berea Sandstones: Evaluating Biogeochemical Reactions of Potential Sandstone–Hydraulic Fracturing Fluid Interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verba, Circe; Harris, Aubrey

The Marcellus shale, located in the mid-Atlantic Appalachian Basin, has been identified as a source for natural gas and targeted for hydraulic fracturing recovery methods. Hydraulic fracturing is a technique used by the oil and gas industry to access petroleum reserves in geologic formations that cannot be accessed with conventional drilling techniques (Capo et al., 2014). This unconventional technique fractures rock formations that have low permeability by pumping pressurized hydraulic fracturing fluids into the subsurface. Although the major components of hydraulic fracturing fluid are water and sand, chemicals, such as recalcitrant biocides and polyacrylamide, are also used (Frac Focus, 2015).more » There is domestic concern that the chemicals could reach groundwater or surface water during transport, storage, or the fracturing process (Chapman et al., 2012). In the event of a surface spill, understanding the natural attenuation of the chemicals in hydraulic fracturing fluid, as well as the physical and chemical properties of the aquifers surrounding the spill site, will help mitigate potential dangers to drinking water. However, reports on the degradation pathways of these chemicals are limited in existing literature. The Appalachian Basin Marcellus shale and its surrounding sandstones host diverse mineralogical suites. During the hydraulic fracturing process, the hydraulic fracturing fluids come into contact with variable mineral compositions. The reactions between the fracturing fluid chemicals and the minerals are very diverse. This report: 1) describes common minerals (e.g. quartz, clay, pyrite, and carbonates) present in the Marcellus shale, as well as the Oriskany and Berea sandstones, which are located stratigraphically below and above the Marcellus shale; 2) summarizes the existing literature of the degradation pathways for common hydraulic fracturing fluid chemicals [polyacrylamide, ethylene glycol, poly(diallyldimethylammonium chloride), glutaraldehyde, guar gum, and isopropanol]; 3) reviews the known research about the interactions between several hydraulic fracturing chemicals [e.g. polyacrylamide, ethylene glycol, poly(diallyldimethylammonium chloride), and glutaraldehyde] with the minerals (quartz, clay, pyrite, and carbonates) common to the lithologies of the Marcellus shale and its surrounding sandstones; and 4) characterizes the Berea sandstone and analyzes the physical and chemical effects of flowing guar gum through a Berea sandstone core.« less

Investigation of Chemical-Foam Design as a Novel Approach toward Immiscible Foam Flooding for Enhanced Oil Recovery

PubMed Central

2017-01-01

Strong foam can be generated in porous media containing oil, resulting in incremental oil recovery; however, oil recovery factor is restricted. A large fraction of oil recovered by foam flooding forms an oil-in-water emulsion, so that costly methods may need to be used to separate the oil. Moreover, strong foam could create a large pressure gradient, which may cause fractures in the reservoir. This study presents a novel chemical-foam flooding process for enhanced oil recovery (EOR) from water-flooded reservoirs. The presented method involved the use of chemically designed foam to mobilize the remaining oil after water flooding and then to displace the mobilized oil to the production well. A blend of two anionic surfactant formulations was formulated for this method: (a) IOS, for achieving ultralow interfacial tension (IFT), and (b) AOS, for generating a strong foam. Experiments were performed using Bentheimer sandstone cores, where X-ray CT images were taken during foam generation to find the stability of the advancing front of foam propagation and to map the gas saturation for both the transient and the steady-state flow regimes. Then the proposed chemical-foam strategy for incremental oil recovery was tested through the coinjection of immiscible nitrogen gas and surfactant solutions with three different formulation properties in terms of IFT reduction and foaming strength capability. The discovered optimal formulation contains a foaming agent surfactant, a low IFT surfactant, and a cosolvent, which has a high foam stability and a considerably low IFT (1.6 × 10–2 mN/m). Coinjection resulted in higher oil recovery and much less MRF than the same process with only using a foaming agent. The oil displacement experiment revealed that coinjection of gas with a blend of surfactants, containing a cosolvent, can recover a significant amount of oil (33% OIIP) over water flooding with a larger amount of clean oil and less emulsion. PMID:29093612

Investigation of Chemical-Foam Design as a Novel Approach toward Immiscible Foam Flooding for Enhanced Oil Recovery.

PubMed

Hosseini-Nasab, S M; Zitha, P L J

2017-10-19

Strong foam can be generated in porous media containing oil, resulting in incremental oil recovery; however, oil recovery factor is restricted. A large fraction of oil recovered by foam flooding forms an oil-in-water emulsion, so that costly methods may need to be used to separate the oil. Moreover, strong foam could create a large pressure gradient, which may cause fractures in the reservoir. This study presents a novel chemical-foam flooding process for enhanced oil recovery (EOR) from water-flooded reservoirs. The presented method involved the use of chemically designed foam to mobilize the remaining oil after water flooding and then to displace the mobilized oil to the production well. A blend of two anionic surfactant formulations was formulated for this method: (a) IOS, for achieving ultralow interfacial tension (IFT), and (b) AOS, for generating a strong foam. Experiments were performed using Bentheimer sandstone cores, where X-ray CT images were taken during foam generation to find the stability of the advancing front of foam propagation and to map the gas saturation for both the transient and the steady-state flow regimes. Then the proposed chemical-foam strategy for incremental oil recovery was tested through the coinjection of immiscible nitrogen gas and surfactant solutions with three different formulation properties in terms of IFT reduction and foaming strength capability. The discovered optimal formulation contains a foaming agent surfactant, a low IFT surfactant, and a cosolvent, which has a high foam stability and a considerably low IFT (1.6 × 10 -2 mN/m). Coinjection resulted in higher oil recovery and much less MRF than the same process with only using a foaming agent. The oil displacement experiment revealed that coinjection of gas with a blend of surfactants, containing a cosolvent, can recover a significant amount of oil (33% OIIP) over water flooding with a larger amount of clean oil and less emulsion.

An Eulerian two-phase flow model for sediment transport under realistic surface waves

NASA Astrophysics Data System (ADS)

Hsu, T. J.; Kim, Y.; Cheng, Z.; Chauchat, J.

2017-12-01

Wave-driven sediment transport is of major importance in driving beach morphology. However, the complex mechanisms associated with unsteadiness, free-surface effects, and wave-breaking turbulence have not been fully understood. Particularly, most existing models for sediment transport adopt bottom boundary layer approximation that mimics the flow condition in oscillating water tunnel (U-tube). However, it is well-known that there are key differences in sediment transport when comparing to large wave flume datasets, although the number of wave flume experiments are relatively limited regardless of its importance. Thus, a numerical model which can resolve the entire water column from the bottom boundary layer to the free surface can be a powerful tool. This study reports an on-going effort to better understand and quantify sediment transport under shoaling and breaking surface waves through the creation of open-source numerical models in the OpenFOAM framework. An Eulerian two-phase flow model, SedFoam (Cheng et al., 2017, Coastal Eng.) is fully coupled with a volume-of-fluid solver, interFoam/waves2Foam (Jacobsen et al., 2011, Int. J. Num. Fluid). The fully coupled model, named SedWaveFoam, regards the air and water phases as two immiscible fluids with the interfaces evolution resolved, and the sediment particles as dispersed phase. We carried out model-data comparisons with the large wave flume sheet flow data for nonbreaking waves reported by Dohmen-Janssen and Hanes (2002, J. Geophysical Res.) and good agreements were obtained for sediment concentration and net transport rate. By further simulating a case without free-surface (mimic U-tube condition), the effects of free-surface, most notably the boundary layer streaming effect on total transport, can be quantified.

The Effect of Matrix Composition on the Deformation and Failure Mechanisms in Metal Matrix Syntactic Foams during Compression

PubMed Central

Kádár, Csilla; Máthis, Kristián; Knapek, Michal; Chmelík, František

2017-01-01

The influence of the matrix material on the deformation and failure mechanisms in metal matrix syntactic foams was investigated in this study. Samples with commercially pure Al (Al) and Al-12 wt % Si (AlSi12) eutectic aluminum matrix, reinforced by hollow ceramic spheres, were compressed at room temperature. Concurrently, the acoustic emission response and the strain field development on the surface were monitored in-situ. The results indicate that the plastic deformation of the cell walls is the governing mechanism in the early stage of straining for both types of foams. At large stresses, deformation bands form both in the Al and AlSi12 foam. In Al foam, cell walls collapse in a large volume. In contrast, the AlSi12 foam is more brittle; therefore, the fracture of precipitates and the crushing of the matrix take place within a distinctive deformation band, along with an occurrence of a significant stress drop. The onset stress of ceramic sphere failure was shown to be not influenced by the matrix material. The in-situ methods provided complementary data which further support these results. PMID:28772556

The Effect of Matrix Composition on the Deformation and Failure Mechanisms in Metal Matrix Syntactic Foams during Compression.

PubMed

Kádár, Csilla; Máthis, Kristián; Knapek, Michal; Chmelík, František

2017-02-17

The influence of the matrix material on the deformation and failure mechanisms in metal matrix syntactic foams was investigated in this study. Samples with commercially pure Al (Al) and Al-12 wt % Si (AlSi12) eutectic aluminum matrix, reinforced by hollow ceramic spheres, were compressed at room temperature. Concurrently, the acoustic emission response and the strain field development on the surface were monitored in-situ. The results indicate that the plastic deformation of the cell walls is the governing mechanism in the early stage of straining for both types of foams. At large stresses, deformation bands form both in the Al and AlSi12 foam. In Al foam, cell walls collapse in a large volume. In contrast, the AlSi12 foam is more brittle; therefore, the fracture of precipitates and the crushing of the matrix take place within a distinctive deformation band, along with an occurrence of a significant stress drop. The onset stress of ceramic sphere failure was shown to be not influenced by the matrix material. The in-situ methods provided complementary data which further support these results.

Porous Media Approach for Modeling Closed Cell Foam

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Sullivan, Roy M.

2006-01-01

In order to minimize boil off of the liquid oxygen and liquid hydrogen and to prevent the formation of ice on its exterior surface, the Space Shuttle External Tank (ET) is insulated using various low-density, closed-cell polymeric foams. Improved analysis methods for these foam materials are needed to predict the foam structural response and to help identify the foam fracture behavior in order to help minimize foam shedding occurrences. This presentation describes a continuum based approach to modeling the foam thermo-mechanical behavior that accounts for the cellular nature of the material and explicitly addresses the effect of the internal cell gas pressure. A porous media approach is implemented in a finite element frame work to model the mechanical behavior of the closed cell foam. The ABAQUS general purpose finite element program is used to simulate the continuum behavior of the foam. The soil mechanics element is implemented to account for the cell internal pressure and its effect on the stress and strain fields. The pressure variation inside the closed cells is calculated using the ideal gas laws. The soil mechanics element is compatible with an orthotropic materials model to capture the different behavior between the rise and in-plane directions of the foam. The porous media approach is applied to model the foam thermal strain and calculate the foam effective coefficient of thermal expansion. The calculated foam coefficients of thermal expansion were able to simulate the measured thermal strain during heat up from cryogenic temperature to room temperature in vacuum. The porous media approach was applied to an insulated substrate with one inch foam and compared to a simple elastic solution without pore pressure. The porous media approach is also applied to model the foam mechanical behavior during subscale laboratory experiments. In this test, a foam layer sprayed on a metal substrate is subjected to a temperature variation while the metal substrate is stretched to simulate the structural response of the tank during operation. The thermal expansion mismatch between the foam and the metal substrate and the thermal gradient in the foam layer causes high tensile stresses near the metal/foam interface that can lead to delamination.

An overview of polyurethane foams in higher specification foam mattresses.

PubMed

Soppi, Esa; Lehtiö, Juha; Saarinen, Hannu

2015-02-01

Soft polyurethane foams exist in thousands of grades and constitute essential components of hospital mattresses. For pressure ulcer prevention, the ability of foams to control the immersion and envelopment of patients is essential. Higher specification foam mattresses (i.e., foam mattresses that relieve pressure via optimum patient immersion and envelopment while enabling patient position changes) are claimed to be more effective for preventing pressure ulcers than standard mattresses. Foam grade evaluations should include resiliency, density, hardness, indentation force/load deflection, progressive hardness, tensile strength, and elongation along with essential criteria for higher specification foam mattresses. Patient-specific requirements may include optimal control of patient immersion and envelopment. Mattress cover characteristics should include breathability, impermeability to fluids, and fire safety and not affect mattress function. Additional determinations such as hardness are assessed according to the guidelines of the American Society for Testing and Materials and the International Organization for Standardization. At this time, no single foam grade provides an optimal combination of the above key requirements, but the literature suggests a combination of at least 2 foams may create an optimal higher specification foam mattress for pressure ulcer prevention. Future research and the development of product specification accuracy standards are needed to help clinicians make evidence-based decisions about mattress use.

Effects of aperture variability and wettability on immiscible displacement in fractures

NASA Astrophysics Data System (ADS)

Yang, Zhibing; Méheust, Yves; Neuweiler, Insa

2017-04-01

Fluid-fluid displacement in porous and fractured media is an important process. Understanding and controlling this process is key to many practical applications, such as hydrocarbon recovery, geological storage of CO2, groundwater remediation, etc. Here, we numerically study fluid-fluid displacement in rough-walled fractures. We focus on the combined effect of wettability and fracture surface topography on displacement patterns and interface growth. We develop a novel numerical model to simulate dynamic fluid invasion under the influence of capillary and viscous forces. The capillary force is calculated using the two principal curvatures (aperture-induced curvature and in-plane curvature) at the fluid-fluid interface, and the viscous force is taken into account by solving the fluid pressure distribution. The aperture field of a fracture is represented by a spatially correlated random field, which is described by a power spectrum for the fracture wall topography and a cutoff wave-length. We numerically produce displacement patterns ranging from stable displacement, capillary fingering, and viscous fingering, as well as the transitions between them. We show that both reducing the aperture variability and increasing the contact angle (from drainage to weak imbibition) stabilize the displacement due to the influence of the in-plane curvature, an effect analogous to that of the cooperative pore filling in porous media. Implications of these results will be discussed.

The Shear Mechanisms of Natural Fractures during the Hydraulic Stimulation of Shale Gas Reservoirs.

PubMed

Zhang, Zhaobin; Li, Xiao

2016-08-23

The shearing of natural fractures is important in the permeability enhancement of shale gas reservoirs during hydraulic fracturing treatment. In this work, the shearing mechanisms of natural fractures are analyzed using a newly proposed numerical model based on the displacement discontinuities method. The fluid-rock coupling system of the model is carefully designed to calculate the shearing of fractures. Both a single fracture and a complex fracture network are used to investigate the shear mechanisms. The investigation based on a single fracture shows that the non-ignorable shearing length of a natural fracture could be formed before the natural fracture is filled by pressurized fluid. Therefore, for the hydraulic fracturing treatment of the naturally fractured shale gas reservoirs, the shear strength of shale is generally more important than the tensile strength. The fluid-rock coupling propagation processes of a complex fracture network are simulated under different crustal stress conditions and the results agree well with those of the single fracture. The propagation processes of complex fracture network show that a smaller crustal stress difference is unfavorable to the shearing of natural fractures, but is favorable to the formation of complex fracture network.

The Shear Mechanisms of Natural Fractures during the Hydraulic Stimulation of Shale Gas Reservoirs

PubMed Central

Zhang, Zhaobin; Li, Xiao

2016-01-01

The shearing of natural fractures is important in the permeability enhancement of shale gas reservoirs during hydraulic fracturing treatment. In this work, the shearing mechanisms of natural fractures are analyzed using a newly proposed numerical model based on the displacement discontinuities method. The fluid-rock coupling system of the model is carefully designed to calculate the shearing of fractures. Both a single fracture and a complex fracture network are used to investigate the shear mechanisms. The investigation based on a single fracture shows that the non-ignorable shearing length of a natural fracture could be formed before the natural fracture is filled by pressurized fluid. Therefore, for the hydraulic fracturing treatment of the naturally fractured shale gas reservoirs, the shear strength of shale is generally more important than the tensile strength. The fluid-rock coupling propagation processes of a complex fracture network are simulated under different crustal stress conditions and the results agree well with those of the single fracture. The propagation processes of complex fracture network show that a smaller crustal stress difference is unfavorable to the shearing of natural fractures, but is favorable to the formation of complex fracture network. PMID:28773834

Viscosity and stability of ultra-high internal phase CO2-in-water foams stabilized with surfactants and nanoparticles with or without polyelectrolytes.

PubMed

Xue, Zheng; Worthen, Andrew; Qajar, Ali; Robert, Isaiah; Bryant, Steven L; Huh, Chun; Prodanović, Maša; Johnston, Keith P

2016-01-01

To date, relatively few examples of ultra-high internal phase supercritical CO2-in-water foams (also referred to as macroemulsions) have been observed, despite interest in applications including "waterless" hydraulic fracturing in energy production. The viscosities and stabilities of foams up to 0.98 CO2 volume fraction were investigated in terms of foam bubble size, interfacial tension, and bulk and surface viscosity. The foams were stabilized with laurylamidopropyl betaine (LAPB) surfactant and silica nanoparticles (NPs), with and without partially hydrolyzed polyacrylamide (HPAM). For foams stabilized with mixture of LAPB and NPs, fine ∼70 μm bubbles and high viscosities on the order of 100 cP at>0.90 internal phase fraction were stabilized for hours to days. The surfactant reduces interfacial tension, and thus facilitates bubble generation and decreases the capillary pressure to reduce the drainage rate of the lamella. The LAPB, which is in the cationic protonated form, also attracts anionic NPs (and anionic HPAM in systems containing polymer) to the interface. The adsorbed NPs at the interface are shown to slow down Ostwald ripening (with or without polymer added) and increase foam stability. In systems with added HPAM, the increase in the bulk and surface viscosity of the aqueous phase further decreases the lamella drainage rate and inhibits coalescence of foams. Thus, the added polymer increases the foam viscosity by threefold. Scaling law analysis shows the viscosity of 0.90 volume fraction foams is inversely proportional to the bubble size. Copyright © 2015 Elsevier Inc. All rights reserved.

Biomechanical Assessment of Locked Plating for the Fixation of Patella Fractures.

PubMed

Wurm, Simone; Augat, Peter; Bühren, Volker

2015-09-01

To analyze the mechanical stability of locked plating in comparison with tension-band wiring for the fixation of fractures of the patella. Biomechanical tests were performed on artificial foam patella specimens comparing an angular stable plate and monocortical screws with tension-band wiring. Tests were performed under combined tension and bending until failure simulating physiological loading of the tibia during walking. Tension-band wiring failed at 66% of the failure load of plating (1052 N, P = 0.002) and had 5 times larger fracture gap displacements (P = 0.002). Based on the biomechanical advantages, locked plating of the patella may constitute a reasonable alternative in the treatment of patella fractures.

Frequency-dependent processing and interpretation (FDPI) of seismic data for identifying, imaging and monitoring fluid-saturated underground reservoirs

DOEpatents

Goloshubin, Gennady M.; Korneev, Valeri A.

2006-11-14

A method for identifying, imaging and monitoring dry or fluid-saturated underground reservoirs using seismic waves reflected from target porous or fractured layers is set forth. Seismic imaging the porous or fractured layer occurs by low pass filtering of the windowed reflections from the target porous or fractured layers leaving frequencies below low-most corner (or full width at half maximum) of a recorded frequency spectra. Additionally, the ratio of image amplitudes is shown to be approximately proportional to reservoir permeability, viscosity of fluid, and the fluid saturation of the porous or fractured layers.

Frequency-dependent processing and interpretation (FDPI) of seismic data for identifying, imaging and monitoring fluid-saturated underground reservoirs

DOEpatents

Goloshubin, Gennady M.; Korneev, Valeri A.

2005-09-06

A method for identifying, imaging and monitoring dry or fluid-saturated underground reservoirs using seismic waves reflected from target porous or fractured layers is set forth. Seismic imaging the porous or fractured layer occurs by low pass filtering of the windowed reflections from the target porous or fractured layers leaving frequencies below low-most corner (or full width at half maximum) of a recorded frequency spectra. Additionally, the ratio of image amplitudes is shown to be approximately proportional to reservoir permeability, viscosity of fluid, and the fluid saturation of the porous or fractured layers.

Experimental and numerical study of hydraulic fracture geometry in shale formations with complex geologic conditions

NASA Astrophysics Data System (ADS)

Ma, Xinfang; Zhou, Tong; Zou, Yushi

2017-05-01

Strike-slip fault geostress and dipping laminated structures in Lujiaping shale formation typically result in difficultly predicting hydraulic fracture (HF) geometries. In this study, a novel 3D fracture propagation model based on discrete element method (DEM) is established. A series of simulations is performed to illustrate the influence of vertical stress difference (△σv = σv-σh), fluid viscosity, and injection rate, on HF growth geometry in the dipping layered formation. Results reveal that the fracturing fluid can easily infiltrate the dipping bedding plane (BP) interfaces with low net pressure for △σv = 1 MPa. HF height growth is also restricted. With increased △σv, fracture propagation in the vertical direction is enhanced, and a fracture network is formed by VF and partially opened dipping BPs. However, it is likely to create simple VF for △σv = 20 MPa. Appropriately increasing fracturing fluid viscosity and injection rate is conductive to weakening the containment effect of BPs on HF growth by increasing the fluid net pressure. However, no indication is found on whether a higher fracturing fluid viscosity is better. Higher viscosity can reduce the activation of BPs, so a stimulated reservoir volume is not necessarily increased. All these results can serve as theoretical guidance for the optimization of fracturing treatments in Lujiaping shale formation.

Fracture Propagation, Fluid Flow, and Geomechanics of Water-Based Hydraulic Fracturing in Shale Gas Systems and Electromagnetic Geophysical Monitoring of Fluid Migration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Jihoon; Um, Evan; Moridis, George

2014-12-01

We investigate fracture propagation induced by hydraulic fracturing with water injection, using numerical simulation. For rigorous, full 3D modeling, we employ a numerical method that can model failure resulting from tensile and shear stresses, dynamic nonlinear permeability, leak-off in all directions, and thermo-poro-mechanical effects with the double porosity approach. Our numerical results indicate that fracture propagation is not the same as propagation of the water front, because fracturing is governed by geomechanics, whereas water saturation is determined by fluid flow. At early times, the water saturation front is almost identical to the fracture tip, suggesting that the fracture is mostlymore » filled with injected water. However, at late times, advance of the water front is retarded compared to fracture propagation, yielding a significant gap between the water front and the fracture top, which is filled with reservoir gas. We also find considerable leak-off of water to the reservoir. The inconsistency between the fracture volume and the volume of injected water cannot properly calculate the fracture length, when it is estimated based on the simple assumption that the fracture is fully saturated with injected water. As an example of flow-geomechanical responses, we identify pressure fluctuation under constant water injection, because hydraulic fracturing is itself a set of many failure processes, in which pressure consistently drops when failure occurs, but fluctuation decreases as the fracture length grows. We also study application of electromagnetic (EM) geophysical methods, because these methods are highly sensitive to changes in porosity and pore-fluid properties due to water injection into gas reservoirs. Employing a 3D finite-element EM geophysical simulator, we evaluate the sensitivity of the crosswell EM method for monitoring fluid movements in shaly reservoirs. For this sensitivity evaluation, reservoir models are generated through the coupled flow-geomechanical simulator and are transformed via a rock-physics model into electrical conductivity models. It is shown that anomalous conductivity distribution in the resulting models is closely related to injected water saturation, but not closely related to newly created unsaturated fractures. Our numerical modeling experiments demonstrate that the crosswell EM method can be highly sensitive to conductivity changes that directly indicate the migration pathways of the injected fluid. Accordingly, the EM method can serve as an effective monitoring tool for distribution of injected fluids (i.e., migration pathways) during hydraulic fracturing operations« less

Edge Fracture in Complex Fluids.

PubMed

Hemingway, Ewan J; Kusumaatmaja, Halim; Fielding, Suzanne M

2017-07-14

We study theoretically the edge fracture instability in sheared complex fluids, by means of linear stability analysis and direct nonlinear simulations. We derive an exact analytical expression for the onset of edge fracture in terms of the shear-rate derivative of the fluid's second normal stress difference, the shear-rate derivative of the shear stress, the jump in shear stress across the interface between the fluid and the outside medium (usually air), the surface tension of that interface, and the rheometer gap size. We provide a full mechanistic understanding of the edge fracture instability, carefully validated against our simulations. These findings, which are robust with respect to choice of rheological constitutive model, also suggest a possible route to mitigating edge fracture, potentially allowing experimentalists to achieve and accurately measure flows stronger than hitherto possible.

Modeling the Impact of Fracture Growth on Fluid Displacements in Deformable Porous Media

NASA Astrophysics Data System (ADS)

Santillán, D.; Cueto-Felgueroso, L.; Juanes, R.

2015-12-01

Coupled flow and geomechanics is a critical research challenge in engineering and the geosciences. The flow of a fluid through a deformable porous media is present in manyenvironmental, industrial, and biological processes,such as the removal of pollutants from underground water bodies, enhanced geothermal systems, unconventional hydrocarbon resources or enhanced oil recovery techniques. However, the injection of a fluid can generate or propagate fractures, which are preferential flow paths. Using numerical simulation, we study the interplay between injection and rock mechanics, and elucidate fracture propagation as a function of injection rate, initial crack topology and mechanical rock properties. Finally, we discuss the role of fracture growth on fluid displacements in porous media. Figure: An example of fracture (in red) propagated in a porous media (in blue)

Predicting Fluid Flow in Stressed Fractures: A Quantitative Evaluation of Methods

NASA Astrophysics Data System (ADS)

Weihmann, S. A.; Healy, D.

2015-12-01

Reliable estimation of fracture stability in the subsurface is crucial to the success of exploration and production in the petroleum industry, and also for wider applications to earthquake mechanics, hydrogeology and waste disposal. Previous work suggests that fracture stability is related to fluid flow in crystalline basement rocks through shear or tensile instabilities of fractures. Our preliminary scoping analysis compares the fracture stability of 60 partly open (apertures 1.5-3 cm) and electrically conductive (low acoustic amplitudes relative to matrix) fractures from a 16 m section of a producing zone in a basement well in Bayoot field, Yemen, to a non-producing zone in the same well (also 16 m). We determine the Critically Stressed Fractures (CSF; Barton et al., 1995) and dilatation tendency (Td; Ferrill et al., 1999). We find that: 1. CSF (Fig. 1) is a poor predictor of high fluid flow in the inflow zone; 88% of the fractures are predicted to be NOT critically stressed and yet they all occur within a zone of high fluid flow rate 2. Td (Fig. 2) is also a poor predictor of high fluid flow in the inflow zone; 67% of the fractures have a LOW Td(< 0.6) 3. For the non-producing zone CSF is a very reliable predictor (100% are not critically stressed) whereas the values of Tdare consistent with their location in non-producing interval (81% are < 0.6) (Fig. 3 & 4). In summary, neither method correlates well with the observed abundance of hydraulically conductive fractures within the producing zone. Within the non-producing zone CSF and Td make reasonably accurate predictions. Fractures may be filled or partially filled with drilling mud or a lower density and electrically conductive fill such as clay in the producing zone and therefore appear (partly) open. In situ stress, fluid pressure, rock properties (friction, strength) and fracture orientation data used as inputs for the CSF and Td calculations are all subject to uncertainty. Our results suggest that scope exists to systematically quantify and explore the impacts of these uncertainties for better predictions of geomechanical stability and fluid conductivity in the subsurface.

Hydraulic fracturing fluid migration in the subsurface: A review and expanded modeling results

NASA Astrophysics Data System (ADS)

Birdsell, Daniel T.; Rajaram, Harihar; Dempsey, David; Viswanathan, Hari S.

2015-09-01

Understanding the transport of hydraulic fracturing (HF) fluid that is injected into the deep subsurface for shale gas extraction is important to ensure that shallow drinking water aquifers are not contaminated. Topographically driven flow, overpressured shale reservoirs, permeable pathways such as faults or leaky wellbores, the increased formation pressure due to HF fluid injection, and the density contrast of the HF fluid to the surrounding brine can encourage upward HF fluid migration. In contrast, the very low shale permeability and capillary imbibition of water into partially saturated shale may sequester much of the HF fluid, and well production will remove HF fluid from the subsurface. We review the literature on important aspects of HF fluid migration. Single-phase flow and transport simulations are performed to quantify how much HF fluid is removed via the wellbore with flowback and produced water, how much reaches overlying aquifers, and how much is permanently sequestered by capillary imbibition, which is treated as a sink term based on a semianalytical, one-dimensional solution for two-phase flow. These simulations include all of the important aspects of HF fluid migration identified in the literature review and are performed in five stages to faithfully represent the typical operation of a hydraulically fractured well. No fracturing fluid reaches the aquifer without a permeable pathway. In the presence of a permeable pathway, 10 times more fracturing fluid reaches the aquifer if well production and capillary imbibition are not included in the model.

Flow of viscoplastic suspensions in a hydraulic fracture: implications to overflush

NASA Astrophysics Data System (ADS)

Boronin, S. A.; Osiptsov, A. A.; Desroches, J.

2017-10-01

The study is devoted to modeling of multiphase flows of immiscible viscoplastic fluids in a hydraulic fracture. In the framework of the lubrication approximation, three-dimensional Navier-Stokes equations are reduced to hyperbolic transport equations for the fluid tracers and a quasi-linear elliptic equation in terms of the fluid pressure. The governing equations are solved numerically using the finite-difference approach. A parametric study of the displacement of Bingham fluids in a Hele-Shaw cell is carried out. It is found that fingers developed through the pillar of a yield-stress suspension trigger the development of unyielded zones. An increase in the Bingham number leads to an increase in the so-called finger shielding effect, which manifests itself via an increase in the overall finger penetration zone and a decrease in the total number of fingers. The effect of flow parameters on the displacement of hydraulic fracturing proppant-laden suspension by a clean fluid in the vicinity of the perforation zone is carried out. This particular case is considered in application to overflush at the end of a stimulation treatment, when a small portion of a thin clean fluid is injected to wash out the particles from the wellbore into the fracture. It is found that an increase in the yield stress and the viscosity contrast between the fracturing and the overflush fluids typically reduces the area of the cavity thus mitigating the risk of loosing the conductive path between the wellbore and the fracture after the fracture closure.

Initiation and propagation of a PKN hydraulic fracture in permeable rock: Toughness dominated regime

NASA Astrophysics Data System (ADS)

Sarvaramini, E.; Garagash, D.

2011-12-01

The present work investigates the injection of a low-viscosity fluid into a pre-existing fracture with constrained height (PKN), as in waterflooding or supercritical CO2 injection. Contrary to conventional hydraulic fracturing, where 'cake build up' limits diffusion to a small zone, the low viscosity fluid allows for diffusion over a wider range of scales. Over large injection times the pattern becomes 2 or 3-D, necessitating a full-space diffusion modeling. In addition, the dissipation of energy associated with fracturing of rock dominates the energy needed for the low-viscosity fluid flow into the propagating crack. As a result, the fracture toughness is important in evaluating both the initiation and the ensuing propagation of these fractures. Classical PKN hydraulic fracturing model, amended to account for full-space leak-off and the toughness [Garagash, unpublished 2009], is used to evaluate the pressure history and fluid leak-off volume during the injection of low viscosity fluid into a pre-existing and initially stationary. In order to find the pressure history, the stationary crack is first subject to a step pressure increase. The response of the porous medium to the step pressure increase in terms of fluid leak-off volume provides the fundamental solution, which then can be used to find the transient pressurization using Duhamel theorem [Detournay & Cheng, IJSS 1991]. For the step pressure increase an integral equation technique is used to find the leak-off rate history. For small time the solution must converge to short time asymptote, which corresponds to 1-D diffusion pattern. However, as the diffusion length in the zone around the fracture increases the assumption of a 1-D pattern is no longer valid and the diffusion follows a 2-D pattern. The solution to the corresponding integral equation gives the leak-off rate history, which is used to find the cumulative leak-off volume. The transient pressurization solution is obtained using global conservation of fluid injected into the fracture. With increasing pressure in the fracture due to the fluid injection, the energy release rate eventually becomes equal to the toughness and fracture propagates. The evolution of the fracture length is established using the method similar to the one employed for the stationary crack.

An approximate solution for a penny-shaped hydraulic fracture that accounts for fracture toughness, fluid viscosity and leak-off.

PubMed

Dontsov, E V

2016-12-01

This paper develops a closed-form approximate solution for a penny-shaped hydraulic fracture whose behaviour is determined by an interplay of three competing physical processes that are associated with fluid viscosity, fracture toughness and fluid leak-off. The primary assumption that permits one to construct the solution is that the fracture behaviour is mainly determined by the three-process multiscale tip asymptotics and the global fluid volume balance. First, the developed approximation is compared with the existing solutions for all limiting regimes of propagation. Then, a solution map, which indicates applicability regions of the limiting solutions, is constructed. It is also shown that the constructed approximation accurately captures the scaling that is associated with the transition from any one limiting solution to another. The developed approximation is tested against a reference numerical solution, showing that accuracy of the fracture width and radius predictions lie within a fraction of a per cent for a wide range of parameters. As a result, the constructed approximation provides a rapid solution for a penny-shaped hydraulic fracture, which can be used for quick fracture design calculations or as a reference solution to evaluate accuracy of various hydraulic fracture simulators.

An approximate solution for a penny-shaped hydraulic fracture that accounts for fracture toughness, fluid viscosity and leak-off

NASA Astrophysics Data System (ADS)

Dontsov, E. V.

2016-12-01

This paper develops a closed-form approximate solution for a penny-shaped hydraulic fracture whose behaviour is determined by an interplay of three competing physical processes that are associated with fluid viscosity, fracture toughness and fluid leak-off. The primary assumption that permits one to construct the solution is that the fracture behaviour is mainly determined by the three-process multiscale tip asymptotics and the global fluid volume balance. First, the developed approximation is compared with the existing solutions for all limiting regimes of propagation. Then, a solution map, which indicates applicability regions of the limiting solutions, is constructed. It is also shown that the constructed approximation accurately captures the scaling that is associated with the transition from any one limiting solution to another. The developed approximation is tested against a reference numerical solution, showing that accuracy of the fracture width and radius predictions lie within a fraction of a per cent for a wide range of parameters. As a result, the constructed approximation provides a rapid solution for a penny-shaped hydraulic fracture, which can be used for quick fracture design calculations or as a reference solution to evaluate accuracy of various hydraulic fracture simulators.

Increasing the production efficiency and reducing the environmental impacts of hydraulic fracturing

NASA Astrophysics Data System (ADS)

Viswanathan, H. S.

2016-12-01

Shale gas is an unconventional fossil energy resource profoundly impacting US energy independence and is projected to last for at least 100 years. Production of methane and other hydrocarbons from low permeability shale involves hydraulic fracturing of rock, establishing fracture connectivity, and multiphase fluid-flow and reaction processes all of which are poorly understood. The result is inefficient extraction with many environmental concerns. A science-based capability is required to quantify the governing mesoscale fluid-solid interactions, including microstructural control of fracture patterns and the interaction of engineered fluids with hydrocarbon flow. These interactions depend on coupled thermo-hydro-mechanical-chemical (THMC) processes over scales from microns to tens of meters. Determining the key mechanisms in subsurface THMC systems has been impeded due to the lack of sophisticated experimental methods to measure fracture aperture and connectivity, multiphase permeability, and chemical exchange capacities at the high temperature, pressure, and stresses present in the subsurface. In this study, we developed and prototyped the microfluidic and triaxial core flood experiments required to reveal the fundamental dynamics of fracture-fluid interactions. The goal is transformation of hydraulic fracturing from present ad hoc approaches to science-based strategies while safely enhancing production. Specifically, we have demonstrated an integrated experimental/modeling approach that allows for a comprehensive characterization of fluid-solid interactions and develop models that can be used to determine the reservoir operating conditions necessary to gain a degree of control over fracture generation, fluid flow, and interfacial processes over a range of subsurface conditions.

Fully Coupled Nonlinear Fluid Flow and Poroelasticity in Arbitrarily Fractured Porous Media: A Hybrid-Dimensional Computational Model

NASA Astrophysics Data System (ADS)

Jin, L.; Zoback, M. D.

2017-10-01

We formulate the problem of fully coupled transient fluid flow and quasi-static poroelasticity in arbitrarily fractured, deformable porous media saturated with a single-phase compressible fluid. The fractures we consider are hydraulically highly conductive, allowing discontinuous fluid flux across them; mechanically, they act as finite-thickness shear deformation zones prior to failure (i.e., nonslipping and nonpropagating), leading to "apparent discontinuity" in strain and stress across them. Local nonlinearity arising from pressure-dependent permeability of fractures is also included. Taking advantage of typically high aspect ratio of a fracture, we do not resolve transversal variations and instead assume uniform flow velocity and simple shear strain within each fracture, rendering the coupled problem numerically more tractable. Fractures are discretized as lower dimensional zero-thickness elements tangentially conforming to unstructured matrix elements. A hybrid-dimensional, equal-low-order, two-field mixed finite element method is developed, which is free from stability issues for a drained coupled system. The fully implicit backward Euler scheme is employed for advancing the fully coupled solution in time, and the Newton-Raphson scheme is implemented for linearization. We show that the fully discretized system retains a canonical form of a fracture-free poromechanical problem; the effect of fractures is translated to the modification of some existing terms as well as the addition of several terms to the capacity, conductivity, and stiffness matrices therefore allowing the development of independent subroutines for treating fractures within a standard computational framework. Our computational model provides more realistic inputs for some fracture-dominated poromechanical problems like fluid-induced seismicity.

Fracture Characterization in Reactive Fluid-Fractured Rock Systems Using Tracer Transport Data

NASA Astrophysics Data System (ADS)

Mukhopadhyay, S.

2014-12-01

Fractures, whether natural or engineered, exert significant controls over resource exploitation from contemporary energy sources including enhanced geothermal systems and unconventional oil and gas reserves. Consequently, fracture characterization, i.e., estimating the permeability, connectivity, and spacing of the fractures is of critical importance for determining the viability of any energy recovery program. While some progress has recently been made towards estimating these critical fracture parameters, significant uncertainties still remain. A review of tracer technology, which has a long history in fracture characterization, reveals that uncertainties exist in the estimated parameters not only because of paucity of scale-specific data but also because of knowledge gaps in the interpretation methods, particularly in interpretation of tracer data in reactive fluid-rock systems. We have recently demonstrated that the transient tracer evolution signatures in reactive fluid-rock systems are significantly different from those in non-reactive systems (Mukhopadhyay et al., 2013, 2014). For example, the tracer breakthrough curves in reactive fluid-fractured rock systems are expected to exhibit a long pseudo-state condition, during which tracer concentration does not change by any appreciable amount with passage of time. Such a pseudo-steady state condition is not observed in a non-reactive system. In this paper, we show that the presence of this pseudo-steady state condition in tracer breakthrough patterns in reactive fluid-rock systems can have important connotations for fracture characterization. We show that the time of onset of the pseudo-steady state condition and the value of tracer concentration in the pseudo-state condition can be used to reliably estimate fracture spacing and fracture-matrix interface areas.

Integrated Modeling and Experiments to Characterize Coupled Thermo-hydro-geomechanical-chemical processes in Hydraulic Fracturing

NASA Astrophysics Data System (ADS)

Viswanathan, H. S.; Carey, J. W.; Karra, S.; Porter, M. L.; Rougier, E.; Kang, Q.; Makedonska, N.; Hyman, J.; Jimenez Martinez, J.; Frash, L.; Chen, L.

2015-12-01

Hydraulic fracturing phenomena involve fluid-solid interactions embedded within coupled thermo-hydro-mechanical-chemical (THMC) processes over scales from microns to tens of meters. Feedbacks between processes result in complex dynamics that must be unraveled if one is to predict and, in the case of unconventional resources, facilitate fracture propagation, fluid flow, and interfacial transport processes. The proposed work is part of a broader class of complex systems involving coupled fluid flow and fractures that are critical to subsurface energy issues, such as shale oil, geothermal, carbon sequestration, and nuclear waste disposal. We use unique LANL microfluidic and triaxial core flood experiments integrated with state-of-the-art numerical simulation to reveal the fundamental dynamics of fracture-fluid interactions to characterize the key coupled processes that impact hydrocarbon production. We are also comparing CO2-based fracturing and aqueous fluids to enhance production, greatly reduce waste water, while simultaneously sequestering CO2. We will show pore, core and reservoir scale simulations/experiments that investigate the contolling mechanisms that control hydrocarbon production.

FIELD TESTING & OPTIMIZATION OF CO2/SAND FRACTURING TECHNOLOGY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raymond L. Mazza

2004-11-30

These contract efforts involved the demonstration of a unique liquid free stimulation technology which was, at the beginning of these efforts, in 1993 unavailable in the US. The process had been developed, and patented in Canada in 1981, and held promise for stimulating liquid sensitive reservoirs in the US. The technology differs from that conventionally used in that liquid carbon dioxide (CO{sub 2}), instead of water is the base fluid. The CO{sub 2} is pumped as a liquid and then vaporizes at reservoir conditions, and because no other liquids or chemicals are used, a liquid free fracture is created. Themore » process requires a specialized closed system blender to mix the liquid CO{sub 2} with proppant under pressure. These efforts were funded to consist of up to 21 cost-shared stimulation events. Because of the vagaries of CO{sub 2} supplies, service company support and operator interest only 19 stimulation events were performed in Montana, New Mexico, and Texas. Final reports have been prepared for each of the four demonstration groups, and the specifics of those demonstrations are summarized. A summary of the demonstrations of a novel liquid-free stimulation process which was performed in four groups of ''Candidate Wells'' situated in Crockett Co., TX; San Juan Co., NM; Phillips Co., MT; and Blaine Co., MT. The stimulation process which employs CO{sub 2} as the working fluid and the production responses were compared with those from wells treated with conventional stimulation technologies, primarily N{sub 2} foam, excepting those in Blaine Co., MT where the reservoir pressure is too low to clean up spent stimulation liquids. A total of 19 liquid-free CO{sub 2}/sand stimulations were performed in 16 wells and the production improvements were generally uneconomic.« less

Characterization of the chemicals used in hydraulic fracturing fluids for wells located in the Marcellus Shale Play.

PubMed

Chen, Huan; Carter, Kimberly E

2017-09-15

Hydraulic fracturing, coupled with the advances in horizontal drilling, has been used for recovering oil and natural gas from shale formations and has aided in increasing the production of these energy resources. The large volumes of hydraulic fracturing fluids used in this technology contain chemical additives, which may be toxic organics or produce toxic degradation byproducts. This paper investigated the chemicals introduced into the hydraulic fracturing fluids for completed wells located in Pennsylvania and West Virginia from data provided by the well operators. The results showed a total of 5071 wells, with average water volumes of 5,383,743 ± 2,789,077 gal (mean ± standard deviation). A total of 517 chemicals was introduced into the formulated hydraulic fracturing fluids. Of the 517 chemicals listed by the operators, 96 were inorganic compounds, 358 chemicals were organic species, and the remaining 63 cannot be identified. Many toxic organics were used in the hydraulic fracturing fluids. Some of them are carcinogenic, including formaldehyde, naphthalene, and acrylamide. The degradation of alkylphenol ethoxylates would produce more toxic, persistent, and estrogenic intermediates. Acrylamide monomer as a primary degradation intermediate of polyacrylamides is carcinogenic. Most of the chemicals appearing in the hydraulic fracturing fluids can be removed when adopting the appropriate treatments. Copyright © 2017 Elsevier Ltd. All rights reserved.

How reactive fluids alter fracture walls and affect shale-matrix accessibility

NASA Astrophysics Data System (ADS)

Fitts, J. P.; Deng, H.; Peters, C. A.

2014-12-01

Predictions of mass transfer across fracture boundaries and fluid flow in fracture networks provide fundamental inputs into risk and life cycle assessments of geologic energy technologies including oil and gas extraction, geothermal energy systems and geologic CO2 storage. However, major knowledge gaps exist due to the lack of experimental observations of how reactive fluids alter the pore structures and accessible surface area within fracture boundaries that control the mass transfer of organics, metals and salts, and influence fluid flow within the fracture. To investigate the fracture and rock matrix properties governing fracture boundary alteration, we developed a new flow-through cell that enables time-dependent 2D x-ray imaging of mineral dissolution and/or precipitation at a fracture surface. The parallel plate design provides an idealized fracture geometry to investigate the relationship between flow rate, reaction rate, and mineral spatial heterogeneity and variation. In the flow-cell, a carbonate-rich sample of Eagle Ford shale was reacted with acidified brine. The extent and rate of mineral dissolution were correlated with calcite abundance relative to less soluble silicate minerals. Three-dimensional x-ray tomography of the reacted fracture wall shows how calcite dissolution left behind a porous network of silicate minerals. And while this silicate network essentially preserved the location of the initial fracture wall, the pore network structures within the fracture boundary were dramatically altered, such that the accessible surface area of matrix components increased significantly. In a second set of experiments with a limestone specimen, however, the extent of dissolution and retreat of the fracture wall was not strictly correlated with the occurrence of calcite. Instead, the pattern and extent of dissolution suggested secondary causes such as calcite morphology, the presence of argillaceous minerals and other diagenetic features. Our experiments show that while calcite dissolution is the primary geochemical driver of fracture wall alterations, hydrodynamic properties and matrix accessibility within fracture boundaries evolve based on a complex relationship between mineral spatial heterogeneity and variation, fluid chemistry and flow rate.

Electrical connection structure for a superconductor element

DOEpatents

Lallouet, Nicolas; Maguire, James

2010-05-04

The invention relates to an electrical connection structure for a superconductor element cooled by a cryogenic fluid and connected to an electrical bushing, which bushing passes successively through an enclosure at an intermediate temperature between ambient temperature and the temperature of the cryogenic fluid, and an enclosure at ambient temperature, said bushing projecting outside the ambient temperature enclosure. According to the invention, said intermediate enclosure is filled at least in part with a solid material of low thermal conductivity, such as a polyurethane foam or a cellular glass foam. The invention is applicable to connecting a superconductor cable at cryogenic temperature to a device for equipment at ambient temperature.

Fabrication of porous titanium scaffold materials by a fugitive filler method.

PubMed

Hong, T F; Guo, Z X; Yang, R

2008-12-01

A clean powder metallurgy route was developed here to produce Ti foams, using a fugitive polymeric filler, polypropylene carbonate (PPC), to create porosities in a metal-polymer compact at the pre-processing stage. The as-produced foams were studied by scanning electron microscopy (SEM), LECO combustion analyses and X-ray diffraction (XRD). Compression tests were performed to assess their mechanical properties. The results show that titanium foams with open pores can be successfully produced by the method. The compressive strength and modulus of the foams decrease with an increasing level of porosity and can be tailored to those of the human bones. After alkali treatment and soaking in a simulated body fluid (SBF) for 3 days, a thin apatite layer was formed along the Ti foam surfaces, which provides favourable bioactive conditions for bone bonding and growth.

Deducing multiple interfacial dynamics during polymeric foaming.

PubMed

Chandan, Mohammed Rehaan; Naskar, Nilanjon; Das, Anuja; Mukherjee, Rabibrata; Harikrishnan, Gopalakrishna Pillai

2018-06-15

Several interfacial phenomena are active during polymeric foaming, the dynamics of which significantly influence terminal stability, cell structure and in turn the thermo-mechanical properties of temporally evolved foam. Understanding these dynamics is important in achieving desired foam properties. Here, we introduce a method to simultaneously portray the time evolution of bubble growth, lamella thinning and Plateau border drainage, occurring during reactive polymeric foaming. In this method, we initially conduct bulk and surface shear rheology under polymerizing and non-foaming conditions. In a subsequent step, foaming experiments were conducted in a rheometer. The microscopic structural dimensions pertaining to the terminal values of the dynamics of each interfacial phenomena are then measured using a combination of scanning electron microscopy, optical microscopy and imaging ellipsometry, after the foaming is over. The measured surface and bulk rheological parameters are incorporated in time evolution equations that are derived from mass and momentum transport occurring when a model viscoelastic fluid is foamed by gas dispersion. Analytical and numerical solutions to these equations portray the dynamics. We demonstrate this method for a series of reactive polyurethane foams generated from different chemical sources. The effectiveness of our method is in simultaneously obtaining these dynamics that are difficult to directly monitor due to short active durations over multiple length scales.

Fractal Viscous Fingering in Fracture Networks

NASA Astrophysics Data System (ADS)

Boyle, E.; Sams, W.; Ferer, M.; Smith, D. H.

2007-12-01

We have used two very different physical models and computer codes to study miscible injection of a low- viscosity fluid into a simple fracture network, where it displaces a much-more viscous "defending" fluid through "rock" that is otherwise impermeable. The one code (NETfLow) is a standard pore level model, originally intended to treat laboratory-scale experiments; it assumes negligible mixing of the two fluids. The other code (NFFLOW) was written to treat reservoir-scale engineering problems; It explicitly treats the flow through the fractures and allows for significant mixing of the fluids at the interface. Both codes treat the fractures as parallel plates, of different effective apertures. Results are presented for the composition profiles from both codes. Independent of the degree of fluid-mixing, the profiles from both models have a functional form identical to that for fractal viscous fingering (i.e., diffusion limited aggregation, DLA). The two codes that solve the equations for different models gave similar results; together they suggest that the injection of a low-viscosity fluid into large- scale fracture networks may be much more significantly affected by fractal fingering than previously illustrated.

Fluid-driven Fractures and Backflow in a Multilayered Elastic Matrix

NASA Astrophysics Data System (ADS)

Smiddy, Samuel; Lai, Ching-Yao; Stone, Howard

2016-11-01

We study the dynamics when pressurized fluid is injected at a constant flow rate into a multi-layered elastic matrix. In particular, we report experiments of such crack propagation as a function of orientation and distance from the contact of the layers. Subsequently we study the shape and propagation of the fluid along the contact of layers as well as volume of fluid remaining in the matrix once the injection pressure is released and "flowback" occurs. The experiments presented here may mimic the interaction between hydraulic fractures and pre-existing fractures and the dynamics of flowback in hydraulic fracturing. Study made possible by the Andlinger Center for Energy and the Environment and the Fred Fox Fund.

Urban Flow and Pollutant Dispersion Simulation with Multi-scale coupling of Meteorological Model with Computational Fluid Dynamic Analysis

NASA Astrophysics Data System (ADS)

Liu, Yushi; Poh, Hee Joo

2014-11-01

The Computational Fluid Dynamics analysis has become increasingly important in modern urban planning in order to create highly livable city. This paper presents a multi-scale modeling methodology which couples Weather Research and Forecasting (WRF) Model with open source CFD simulation tool, OpenFOAM. This coupling enables the simulation of the wind flow and pollutant dispersion in urban built-up area with high resolution mesh. In this methodology meso-scale model WRF provides the boundary condition for the micro-scale CFD model OpenFOAM. The advantage is that the realistic weather condition is taken into account in the CFD simulation and complexity of building layout can be handled with ease by meshing utility of OpenFOAM. The result is validated against the Joint Urban 2003 Tracer Field Tests in Oklahoma City and there is reasonably good agreement between the CFD simulation and field observation. The coupling of WRF- OpenFOAM provide urban planners with reliable environmental modeling tool in actual urban built-up area; and it can be further extended with consideration of future weather conditions for the scenario studies on climate change impact.

Experimental Evidence of Volcanic Earthquakes Induced by Different Fluid Types

NASA Astrophysics Data System (ADS)

Clarke, J. A.; Adam, L.; Sarout, J.; van Wijk, K.; Dautriat, J. D.; Kennedy, B.

2017-12-01

Low Frequency volcanic seismicity has long been associated with resonance in fluid-filled cracks or conduits driven by pressure perturbations at depth. In volcano monitoring, fluid movement, fracturing and the conduit geometry are interpreted based on field observations, laboratory experiments, and numerical models. Fluids in a volcanic environment include gasses, brine and magmas with different viscosities. Magma viscosity is a key influence on eruptive behaviour. For example, increasing magma viscosity is known to favour explosive eruptions. How different fluids affect volcano seismicity is not well understood. Here, we explore the effects of fluid type on volcano seismic signals. Frequency content in the signal, frequency of the events, source mechanism and quality factor are studied. We simulate volcano tectonic (fracturing) and volcano seismic (fluid movement) signatures in a controlled laboratory environment using a range of rock samples, fluid types and pressure conditions. The viscosity of the fluids spans six orders of magnitude, representing realistic volcanic fluids. Microseismicity is generated by venting pressurised fluids through pre-generated fracture networks in cylindrical rock core samples and detected by an array of 18 ultrasonic transducers. We fracture samples of two lithologies: 1) low porosity impermeable granite samples and 2) a permeable volcanic ash tuff sample. Permeability and porosity in the granites are due to a fracture network, while in the tuff a high porosity matrix ( 40 %) and a fracture network interact. The fluids used are nitrogen gas, water, and mixtures of water and glycerol. We generate and detect a myriad of seismic event types, some of which resemble well-known families of volcano-tectonic, low-frequency, hybrid and tremor-type seismicity. Samples with fluids of lower density and viscosity generate a higher number of seismic events. We will present an integrated analysis of the event types, frequency content, source locations and mechanisms. In addition, we explore the importance of seismic wave attenuation by studying the relationship between wave path and event frequency content.

The Multi-Porosity Multi-Permeability and Electrokinetic Natures of Shales and Their Effects in Hydraulic Fracturing of Unconventional Shale Reservoirs

NASA Astrophysics Data System (ADS)

Liu, C.; Hoang, S. K.; Tran, M. H.; Abousleiman, Y. N.

2013-12-01

Imaging studies of unconventional shale reservoir rocks have recently revealed the multi-porosity multi-permeability nature of these intricate formations. In particular, the porosity spectrum of shale reservoir rocks often comprises of the nano-porosity in the organic matters, the inter-particle micro-porosity, and the macroscopic porosity of the natural fracture network. Shale is also well-known for its chemically active behaviors, especially shrinking and swelling when exposed to aqueous solutions, as the results of pore fluid exchange with external environment due to the difference in electro-chemical potentials. In this work, the effects of natural fractures and electrokinetic nature of shale on the formation responses during hydraulic fracturing are examined using the dual-poro-chemo-electro-elasticity approach which is a generalization of the classical Biot's poroelastic formulation. The analyses show that the presence of natural fractures can substantially increase the leak-off rate of fracturing fluid into the formation and create a larger region of high pore pressure near the fracture face as shown in Fig.1a. Due to the additional fluid invasion, the naturally fractured shale swells up more and the fracture aperture closes faster compared to an intrinsically low permeability non-fractured shale formation as shown in Fig.1b. Since naturally fractured zones are commonly targeted as pay zones, it is important to account for the faster fracture closing rate in fractured shales in hydraulic fracturing design. Our results also show that the presence of negative fixed charges on the surface of clay minerals creates an osmotic pressure at the interface of the shale and the external fluid as shown in Fig.1c. This additional Donnan-induced pore pressure can result in significant tensile effective stresses and tensile damage in the shale as shown in Fig.1d. The induced tensile damage can exacerbate the problem of proppant embedment resulting in more fracture closure and reduction of fracture length and productivity. The results also suggest that a fracturing fluid with appropriately designed salinity can minimize the chemically induced tensile damage and, thus, maximize the productivity from the created hydraulic fractures.

Capturing poromechanical coupling effects of the reactive fracturing process in porous rock via a DEM-network model

NASA Astrophysics Data System (ADS)

Ulven, Ole Ivar; Sun, WaiChing

2016-04-01

Fluid transport in a porous medium has important implications for understanding natural geological processes. At a sufficiently large scale, a fluid-saturated porous medium can be regarded as a two-phase continuum, with the fluid constituent flowing in the Darcian regime. Nevertheless, a fluid mediated chemical reaction can in some cases change the permeability of the rock locally: Mineral dissolution can cause increased permeability, whereas mineral precipitation can reduce the permeability. This might trigger a complicated hydro-chemo-mechanical coupling effect that causes channeling of fluids or clogging of the system. If the fluid is injected or produced at a sufficiently high rate, the pressure might increase enough to cause the onset and propagation of fractures. Fractures in return create preferential flow paths that enhance permeability, localize fluid flow and chemical reaction, prevent build-up of pore pressure and cause anisotropy of the hydro-mechanical responses of the effective medium. This leads to a complex coupled process of solid deformation, chemical reaction and fluid transport enhanced by the fracture formation. In this work, we develop a new coupled numerical model to study the complexities of feedback among fluid pressure evolution, fracture formation and permeability changes due to a chemical process in a 2D system. We combine a discrete element model (DEM) previously used to study a volume expanding process[1, 2] with a new fluid transport model based on poroelasticity[3] and a fluid-mediated chemical reaction that changes the permeability of the medium. This provides new insights into the hydro-chemo-mechanical process of a transforming porous medium. References [1] Ulven, O. I., Storheim, H., Austrheim, H., and Malthe-Sørenssen, A. "Fracture Initiation During Volume Increasing Reactions in Rocks and Applications for CO2 Sequestration", Earth Planet. Sc. Lett. 389C, 2014a, pp. 132 - 142, doi:10.1016/j.epsl.2013.12.039. [2] Ulven, O. I., Jamtveit, B., and Malthe-Sørenssen, A., "Reaction-driven fracturing of porous rock", J. Geophys. Res. Solid Earth 119, 2014b, doi:10.1002/2014JB011102. [3] Ulven, O. I., and Sun, W.C., "A locally mass-conserving dual-graph lattice model for fluid-driven fracture", in prep.

Low-frequency fluid waves in fractures and pipes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Korneev, Valeri

2010-09-01

Low-frequency analytical solutions have been obtained for phase velocities of symmetrical fluid waves within both an infinite fracture and a pipe filled with a viscous fluid. Three different fluid wave regimes can exist in such objects, depending on the various combinations of parameters, such as fluid density, fluid viscosity, walls shear modulus, channel thickness, and frequency. Equations for velocities of all these regimes have explicit forms and are verified by comparisons with the exact solutions. The dominant role of fractures in rock permeability at field scales and the strong amplitude and frequency effects of Stoneley guided waves suggest the importancemore » of including these wave effects into poroelastic theories.« less

Integrated Experimental and Computational Study of Hydraulic Fracturing and the Use of Alternative Fracking Fluids

NASA Astrophysics Data System (ADS)

Viswanathan, H.; Carey, J. W.; Karra, S.; Porter, M. L.; Rougier, E.; Zhang, D.; Makedonska, N.; Middleton, R. S.; Currier, R.; Gupta, R.; Lei, Z.; Kang, Q.; O'Malley, D.; Hyman, J.

2014-12-01

Shale gas is an unconventional fossil energy resource that is already having a profound impact on US energy independence and is projected to last for at least 100 years. Production of methane and other hydrocarbons from low permeability shale involves hydrofracturing of rock, establishing fracture connectivity, and multiphase fluid-flow and reaction processes all of which are poorly understood. The result is inefficient extraction with many environmental concerns. A science-based capability is required to quantify the governing mesoscale fluid-solid interactions, including microstructural control of fracture patterns and the interaction of engineered fluids with hydrocarbon flow. These interactions depend on coupled thermo-hydro-mechanical-chemical (THMC) processes over scales from microns to tens of meters. Determining the key mechanisms in subsurface THMC systems has been impeded due to the lack of sophisticated experimental methods to measure fracture aperture and connectivity, multiphase permeability, and chemical exchange capacities at the high temperature, pressure, and stresses present in the subsurface. This project uses innovative high-pressure microfluidic and triaxial core flood experiments on shale to explore fracture-permeability relations and the extraction of hydrocarbon. These data are integrated with simulations including lattice Boltzmann modeling of pore-scale processes, finite-element/discrete element models of fracture development in the near-well environment, discrete-fracture modeling of the reservoir, and system-scale models to assess the economics of alternative fracturing fluids. The ultimate goal is to make the necessary measurements to develop models that can be used to determine the reservoir operating conditions necessary to gain a degree of control over fracture generation, fluid flow, and interfacial processes over a range of subsurface conditions.

Fault Weakening due to Erosion by Fluids: A Possible Origin of Intraplate Earthquake Swarms

NASA Astrophysics Data System (ADS)

Vavrycuk, V.; Hrubcova, P.

2016-12-01

The occurrence and specific properties of earthquake swarms in geothermal areas are usually attributed to a highly fractured rock and/or heterogeneous stress within the rock mass being triggered by magmatic or hydrothermal fluid intrusion. The increase of fluid pressure destabilizes fractures and causes their opening and subsequent shear-tensile rupture. The spreading and evolution of the seismic activity is controlled by fluid flow due to diffusion in a permeable rock and/or by the redistribution of Coulomb stress. The `fluid-injection model', however, is not valid universally. We provide evidence that this model is inconsistent with observations of earthquake swarms in West Bohemia, Czech Republic. Full seismic moment tensors of micro-earthquakes in the 1997 and 2008 swarms in West Bohemia indicate that fracturing at the starting phase of the swarm was not associated with fault openings caused by pressurized fluids but rather with fault compactions. This can physically be explained by a `fluid-erosion model', when the essential role in the swarm triggering is attributed to chemical and hydrothermal fluid-rock interactions in the focal zone. Since the rock is exposed to circulating hydrothermal, CO2-saturated fluids, the walls of fractures are weakened by dissolving and altering various minerals. If fault strength lowers to a critical value, the seismicity is triggered. The fractures are compacted during failure, the fault strength recovers and a new cycle begins.

Thermal Effect on Fracture Integrity in Enhanced Geothermal Systems

NASA Astrophysics Data System (ADS)

Zeng, C.; Deng, W.; Wu, C.; Insall, M.

2017-12-01

In enhanced geothermal systems (EGS), cold fluid is injected to be heated up for electricity generation purpose, and pre-existing fractures are the major conduits for fluid transport. Due to the relative cold fluid injection, the rock-fluid temperature difference will induce thermal stress along the fracture wall. Such large thermal stress could cause the failure of self-propping asperities and therefore change the fracture integrity, which could affect the heat recovery efficiency and fluid recycling. To study the thermal effect on fracture integrity, two mechanisms pertinent to thermal stress are proposed to cause asperity contact failure: (1) the crushing between two pairing asperities leads to the failure at contact area, and (2) the thermal spalling expedites this process. Finite element modeling is utilized to investigate both failure mechanisms by idealizing the asperities as hemispheres. In the numerical analysis, we have implemented meso-scale damage model to investigate coupled failure mechanism induced by thermomechanical stress field and original overburden pressure at the vicinity of contact point. Our results have shown that both the overburden pressure and a critical temperature determine the threshold of asperity failure. Since the overburden pressure implies the depth of fractures in EGS and the critical temperature implies the distance of fractures to the injection well, our ultimate goal is to locate a region of EGS where the fracture integrity is vulnerable to such thermal effect and estimate the influences.

Microbial community changes in hydraulic fracturing fluids and produced water from shale gas extraction.

PubMed

Murali Mohan, Arvind; Hartsock, Angela; Bibby, Kyle J; Hammack, Richard W; Vidic, Radisav D; Gregory, Kelvin B

2013-11-19

Microbial communities associated with produced water from hydraulic fracturing are not well understood, and their deleterious activity can lead to significant increases in production costs and adverse environmental impacts. In this study, we compared the microbial ecology in prefracturing fluids (fracturing source water and fracturing fluid) and produced water at multiple time points from a natural gas well in southwestern Pennsylvania using 16S rRNA gene-based clone libraries, pyrosequencing, and quantitative PCR. The majority of the bacterial community in prefracturing fluids constituted aerobic species affiliated with the class Alphaproteobacteria. However, their relative abundance decreased in produced water with an increase in halotolerant, anaerobic/facultative anaerobic species affiliated with the classes Clostridia, Bacilli, Gammaproteobacteria, Epsilonproteobacteria, Bacteroidia, and Fusobacteria. Produced water collected at the last time point (day 187) consisted almost entirely of sequences similar to Clostridia and showed a decrease in bacterial abundance by 3 orders of magnitude compared to the prefracturing fluids and produced water samplesfrom earlier time points. Geochemical analysis showed that produced water contained higher concentrations of salts and total radioactivity compared to prefracturing fluids. This study provides evidence of long-term subsurface selection of the microbial community introduced through hydraulic fracturing, which may include significant implications for disinfection as well as reuse of produced water in future fracturing operations.

A Computational/Experimental Platform for Investigating Three-Dimensional Puzzle Solving of Comminuted Articular Fractures

PubMed Central

Thomas, Thaddeus P.; Anderson, Donald D.; Willis, Andrew R.; Liu, Pengcheng; Frank, Matthew C.; Marsh, J. Lawrence; Brown, Thomas D.

2011-01-01

Reconstructing highly comminuted articular fractures poses a difficult surgical challenge, akin to solving a complicated three-dimensional (3D) puzzle. Pre-operative planning using CT is critically important, given the desirability of less invasive surgical approaches. The goal of this work is to advance 3D puzzle solving methods toward use as a pre-operative tool for reconstructing these complex fractures. Methodology for generating typical fragmentation/dispersal patterns was developed. Five identical replicas of human distal tibia anatomy, were machined from blocks of high-density polyetherurethane foam (bone fragmentation surrogate), and were fractured using an instrumented drop tower. Pre- and post-fracture geometries were obtained using laser scans and CT. A semi-automatic virtual reconstruction computer program aligned fragment native (non-fracture) surfaces to a pre-fracture template. The tibias were precisely reconstructed with alignment accuracies ranging from 0.03-0.4mm. This novel technology has potential to significantly enhance surgical techniques for reconstructing comminuted intra-articular fractures, as illustrated for a representative clinical case. PMID:20924863

Garden City Vein Complex, Gale Crater, Mars: Implications for Late Diagenetic Fluid Flow

NASA Astrophysics Data System (ADS)

Kronyak, R. E.; Kah, L. C.; Blaney, D. L.; Sumner, D. Y.; Fisk, M. R.; Rapin, W.; Nachon, M.; Mangold, N.; Grotzinger, J. P.; Wiens, R. C.

2015-12-01

Calcium sulfate filled fractures are observed in nearly all stratigraphic units encountered by the Mars Science Laboratory (MSL) Curiosity rover. The mm-scale of veins, however, provides little evidence for emplacement style. From sols 924-949, Curiosity observed a vein rich outcrop called Garden City, which shows variation in both thickness and complexity of veins. Extensive Mastcam and MAHLI imaging was conducted across the outcrop to provide textural detail that can be related to emplacement mechanisms. Additionally, Curiosity collected geochemical data on 17 ChemCam targets and 7 APXS targets, shedding light on the composition and variety of potential vein fluids. The Garden City vein system records (1) the presence of distinct dark-toned and light-toned (calcium sulfate) mineralization, and (2) the presence of laminated, epitaxial, and brecciated fabrics that suggest multiple emplacement modes. Dark-toned mineralization is observed as erosionally resistant ridges predominantly along fracture walls. Although erosional resistance may reflect the permeability of host rock to fracture-borne fluids, at Garden City, laminated textures suggest that at least some mineralization may have occurred as fracture-fill. Light-toned mineralization often bisects dark-toned material, indicating re-use of fluid pathways. Light-toned veinlets permeate fracture walls, and the largest veins entrain host rock and dark-toned material within calcium sulfate matrix. Such brecciation indicates high forces associated with fluid expulsion. Elsewhere, linear patterns occur broadly perpendicular to fracture walls, and are interpreted to represent epitaxial crystal growth, suggesting lower flow rates and fluid flow pressures within the fracture system. Together these observations indicate multiple episodes of fluid flow in the Gale Crater system.

Potential Impacts of Spilled Hydraulic Fracturing Fluid Chemicals on Water Resources: Types, volumes, and physical-chemical properties of chemicals

EPA Science Inventory

Hydraulic fracturing (HF) fluid chemicals spilled on-site may impact drinking water resources. While chemicals generally make up <2% of the total injected fluid composition by mass, spills may have undiluted concentrations. HF fluids typically consist of a mixture of base flui...

Fracture propagation and fluid transport in palaeogeothermal fields and man-made reservoirs in limestone

NASA Astrophysics Data System (ADS)

Philipp, S. L.; Reyer, D.; Meier, S.

2009-04-01

Geothermal reservoirs are rock units from which the internal heat can be extracted using water as a transport means in an economically efficient manner. In geothermal reservoirs in limestone (and similar in other rocks with low matrix permeability), fluid flow is largely, and may be almost entirely, controlled by the permeability of the fracture network. No flow, however, takes place along a particular fracture network unless the fractures are interconnected. For fluid flow to occur from one site to another there must be at least one interconnected cluster of fractures that links these sites (the percolation threshold must be reached). In order to generate permeability in man-made reservoirs, interconnected fracture systems are formed either by creating hydraulic fractures or by massive hydraulic stimulation of the existing fracture system in the host rock. For effective stimulation, the geometry of the fracture system and the mechanical properties of the host rock (particularly rock stiffnesses and strengths) must be known. Here we present results of a study of fracture systems in rocks that could be used to host man-made geothermal reservoirs: the Muschelkalk (Middle Triassic) limestones in Germany. Studies of fracture systems in exposed palaeogeothermal fields can also help understand the permeability development in stimulated reservoirs. We therefore present data on the infrastructures of extinct fracture-controlled geothermal fields in fault zones in the Blue Lias (Lower Jurassic), Great Britain. In fault zones there are normally two main mechanical and hydrogeological units. The fault core, along which fault slip mostly occurs, consists mainly of breccia and other cataclastic rocks. The fault damage zone comprises numerous fractures of various sizes. During fault slip, the fault core may transport water (if its orientation is favourable to the hydraulic gradient in the area). In the damage zone, however, fluid transport through fracture networks depends particularly on the current local stress field. One reason for this is that fractures are sensitive to changes in the stress field and deform much more easily than circular pores. If the maximum horizontal compression is oriented perpendicular to the fault strike, its fractures (mainly in the damage zone) tend to be closed and lead less water than if the maximum horizontal compression is oriented parallel to the fault strike, in which case its fractures tend to open up and be favourable to fluid transport. In areas of potential geothermal reservoirs, fault zones must be studied, keeping in mind that the permeability structure of a fault zone depends partly on the mechanical units of the fault zone and partly on the local stress field. To explore stress fields affecting fracture propagation we have run numerical models using the finite-element and the boundary-element methods. We focus on the influence of changes in mechanical properties (particularly Young's modulus) between host rock layers in geothrmal reservoirs in limestone. The numerical models show that stresses commonly concentrate in stiff layers. Also, at the contacts between soft marl and stiffer limestone layers, the stress trajectories (directions of the principal stresses) may become rotated. Depending on the external loading conditions, certain layers may become stress barriers to fracture propagation. In a reservoir where most hydrofractures become stratabound (confined to individual layers), interconnected fracture systems are less likely to develop than in one with non-stratabound hydrofractures. Reservoirs with stratabound fractures may not reach the percolation threshold needed for significant permeability. We also used the field data to investigate the fracture-related permeability of fluid reservoirs in limestone with numerical models. We simulated different scenarios, in which potential fluid pathways were added successively (vertical extension fractures, inclined shear fractures and open layer contacts). Short and straight fluid pathways parallel to the flow direction lead to the highest permeabilities. The better the connectivity of the fracture system, the higher is the resulting permeability. Only in well-interconnected, continuous systems of fluid pathways there is a correlation between the apertures of the fractures and the permeability. Our results suggest that fluid transport along faults, and the propagation and aperture variation of hydrofractures, are important parameters in the permeability development of geothermal reservoirs. These studies provide a basis for models of fracture networks and fluid transport in future man-made reservoirs. We conclude that the likely permeability of a man-made geothermal reservoir can be inferred from field data, natural analogues, laboratory measurements, and numerical models.

Effect of the oxygen content in solution on the static and cyclic deformation of titanium foams.

PubMed

Lefebvre, L P; Baril, E; Bureau, M N

2009-11-01

It is well known that interstitials affect the mechanical properties of titanium and titanium alloys. Their effects on the fatigue properties of titanium foams have not, however, been documented in the literature. This paper presents the effect of the oxygen content on the static and dynamic compression properties of titanium foams. Increasing the oxygen content from 0.24 to 0.51 wt% O in solution significantly increases the yield strength and reduces the ductility of the foams. However, the fatigue limit is not significantly affected by the oxygen content and falls within the 92 MPa +/- 12 MPa range for all specimens investigated in this study. During cyclic loading, deformation is initially coming from cumulative creep followed by the formation of microcracks. The coalescence of these microcracks is responsible for the rupture of the specimens. Fracture surfaces of the specimens having lower oxygen content show a more ductile aspect than the specimens having higher oxygen content.

In-Situ Ultra Low Frequency Poroelastic Response of a Natural Macro-Fracture

NASA Astrophysics Data System (ADS)

Guglielmi, Y.; Cappa, F.; Rutqvist, J.; Tsang, C.; Gaffet, S.

2008-12-01

The seismic visibility of macro-fractures filled with fluids is a central problem in the exploration of thermo- hydro-mechanical and chemical processes that occur in Earth' s subsurface. Most studies have been concerned (1) with cracks of a small size relative to the seismic wavelength (2) with "core-sized" samples of single macro-fractures. In comparison, in-situ studies of macro-fractures are very rare and no real estimate is made of the relevance of this convenient "core-sized" data to in-situ reservoirs in general. In this study, we present a new experimental approach to in-situ characterize mechanical and hydraulic properties of fractures using the innovative HPPP protocol. This protocol allows simultaneous high-frequency (120.2 Hz) sampling of normal displacement and fluid pressure in a borehole intersecting the fracture. We show preliminary results conducted in a single fracture vertically embedded in a carbonate reservoir that contains 3 sets of macro-fractures with an average 2m spacing. Two HPPP probes were set, spaced one meter vertically in the fracture. Two types of ULF seismic sources are applied: a fluid pressure pulse injected in the fracture and a hammer hit at a point located 5m far from the fracture plane. There is a highly non-linear variation of fracture normal displacement-versus- fluid pressure as a function of frequency, the higher the frequency, the lower the displacement spectral amplitude is. The pressure pulse and the hammer hit allow exploring the fracture poroelastic response in the [0 - 3Hz] frequency range. The fracture plays the role of a "low-pass" filter for fluid pressure waves; only a quasi-static pressure signal being registered at the receiver. The displacement wave propagation is more complex resulting in uncoupled quasi-static-pressure-2Hz-deformation signals at the receiver. For low magnitude seismic sources (low amplitude pulse and seismic wave), the fracture natural resonance is amplified resulting in separate signals power spectral peaks. When fluid pressure is enough increased, hydraulic diffusion takes place at frequencies lower than 1.2 Hz. Poroelastic effects related to static hydraulic diffusion and to wave propagation were described separately using a linear elastic model where the fracture was treated as a displacement discontinuity across which stresses are continuous but displacement are discontinuous. It appears that the dynamic fracture normal stiffness at 2 to 3 Hz is a factor of 2.8 higher than the static stiffness although the fracture displays a high hydraulic aperture of 10-4 m. This surprising result is related to a high heterogeneity of the fracture channel network with a large porosity/permeability contrast that does not allow fluid displacement under dynamic loading. The HPPP approach appears as a possibility to in-situ characterize such fractures static to seismic poroelastic heterogeneous properties.

Hydro-fracture in the laboratory: matching diagnostic seismic signals to fracture networks

NASA Astrophysics Data System (ADS)

Gehne, S.; Benson, P. M.; Koor, N.; Dobson, K. J.; Enfield, M.; Barber, A.

2017-12-01

Hydraulic fracturing is a key process in both natural (e.g. dyke intrusion) and engineered environments (e.g. shale gas). To better understand this process, we present new data from simulated hydraulic fracturing in a controlled laboratory environment in order to track fracture nucleation (location) and propagation (velocity) in space and time to assess the fracture mechanics and developing fracture network. Fluid overpressure is used to generate a permeable network of micro tensile fractures in an anisotropic sandstone and a highly anisotropic shale. A newly developed technique, using a steel guide arrangement to direct pressurised fluid into a sealed section of an axially drilled conduit, allows the pore fluid to contact the rock directly and to initiate tensile fractures from a pre-defined zone inside the sample. Acoustic emission location is used to record and map the nucleation and development of the micro-fracture network. For both rock types, fractures progresses parallel to the bedding plane (short-transverse) if the bedding plane is aligned with the direction of σ1 requiring breakdown pressures of approximately 7 and 13MPa respectively at a confining pressure of 8MPa. The data also indicates a more ductile behaviour of the shale than expected. We use X-Ray Computed Tomography (CT) to evaluate the evolved fracture network in terms of fracture pattern and aperture. Hydraulic fracturing produces very planar fractures in the shale, with axial fractures over the entire length of the sample broadly following the bedding. In contrast, fractures in the sandstone are more diffuse, linking pore spaces as they propagate. However, secondary micro cracking, branching of the main fracture, are also observed. These new experiments suggest that fracture pattern, fracture propagation trajectories, and fracturing fluid pressures are predominantly controlled by the interaction between the anisotropic mechanical properties of the rock and the anisotropic stress environment.

Damping of liquid sloshing by foams: from everyday observations to liquid transport

NASA Astrophysics Data System (ADS)

Sauret, Alban; Boulogne, Francois; Cappello, Jean; Stone, Howard

2014-11-01

When a liquid-filled container is set in motion, the free surface of the liquid starts to slosh, i.e. oscillate. Such effects can be observed when a glass of water is handled carelessly and the fluid sloshes or even spills over the rim of the container. However, beer does not slosh as readily, which suggests that the presence of foam could be used to damp sloshing. In this work, we study experimentally the effect on sloshing of liquid foam placed on top of a liquid bath in a Hele-Shaw cell. We generate a monodisperse 2D liquid foam and track its motion. The influence of the foam on the sloshing dynamics is characterized: 2 to 3 layers of bubbles are sufficient to significantly damp the oscillations. For more than 5 layers of bubbles, the original vertical motion of the foam becomes mainly horizontal. We rationalize our experimental findings with a model that describes the foam contribution to the damping coefficient. This study motivated by everyday observations has promising applications in numerous industrial applications such as the transport of liquid in cargoes.

Construction and geometric stability of physiological flow rate wall-less stenosis phantoms.

PubMed

Ramnarine, K V; Anderson, T; Hoskins, P R

2001-02-01

Wall-less flow phantoms are preferred for ultrasound (US) because tissue-mimicking material (TMM) with good acoustical properties can be made and cast to form anatomical models. The construction and geometrical stability of wall-less TMM flow phantoms is described using a novel method of sealing to prevent leakage of the blood-mimicking fluid (BMF). Wall-less stenosis flow models were constructed using a robust agar-based TMM and sealed using reticulated foam at the inlet and outlet tubes. There was no BMF leakage at the highest flow rate of 2.8 L/min in 0%, 35% and 57% diameter reduction stenoses models. Failure of the 75% stenosis model, due to TMM fracture, occurred at maximum flow rate of 2 L/min (mean velocity 10 m/s within the stenosis). No change of stenosis geometry was measured over 4 days. The construction is simple and effective and extends the possibility for high flow rate studies using robust TMM wall-less phantoms.

The kinetics of polyurethane structural foam formation: Foaming and polymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rao, Rekha R.; Mondy, Lisa A.; Long, Kevin N.

We are developing kinetic models to understand the manufacturing of polymeric foams, which evolve from low viscosity Newtonian liquids, to bubbly liquids, finally producing solid foam. Closed-form kinetics are formulated and parameterized for PMDI-10, a fast curing polyurethane, including polymerization and foaming. PMDI- 10 is chemically blown, where water and isocyanate react to form carbon dioxide. The isocyanate reacts with polyol in a competing reaction, producing polymer. Our approach is unique, though it builds on our previous work and the polymerization literature. This kinetic model follows a simplified mathematical formalism that decouples foaming and curing, including an evolving glass transitionmore » temperature to represent vitrification. This approach is based on IR, DSC, and volume evolution data, where we observed that the isocyanate is always in excess and does not affect the kinetics. Finally, the kinetics are suitable for implementation into a computational fluid dynamics framework, which will be explored in subsequent papers.« less

The kinetics of polyurethane structural foam formation: Foaming and polymerization

DOE PAGES

Rao, Rekha R.; Mondy, Lisa A.; Long, Kevin N.; ...

2017-02-15

We are developing kinetic models to understand the manufacturing of polymeric foams, which evolve from low viscosity Newtonian liquids, to bubbly liquids, finally producing solid foam. Closed-form kinetics are formulated and parameterized for PMDI-10, a fast curing polyurethane, including polymerization and foaming. PMDI- 10 is chemically blown, where water and isocyanate react to form carbon dioxide. The isocyanate reacts with polyol in a competing reaction, producing polymer. Our approach is unique, though it builds on our previous work and the polymerization literature. This kinetic model follows a simplified mathematical formalism that decouples foaming and curing, including an evolving glass transitionmore » temperature to represent vitrification. This approach is based on IR, DSC, and volume evolution data, where we observed that the isocyanate is always in excess and does not affect the kinetics. Finally, the kinetics are suitable for implementation into a computational fluid dynamics framework, which will be explored in subsequent papers.« less

Abyssal Sequestration of Nuclear Waste in Earth's Crust

NASA Astrophysics Data System (ADS)

Germanovich, L. N.; Garagash, D.; Murdoch, L. C.; Robinowitz, M.

2013-12-01

This work outlines a new method for disposing of hazardous (e.g., nuclear) waste. The technique is called Abyssal Sequestration, and it involves placing the waste at extreme depths in Earth's crust where it could achieve the geologically-long period of isolation. Abyssal Sequestration involves storing the waste in hydraulic fractures driven by gravity, a process we term gravity fracturing. In short, we suggest creating a dense fluid (slurry) containing waste, introducing the fluid into a fracture, and extending the fracture downward until it becomes long enough to propagate independently. The fracture will continue to propagate downward to great depth, permanently isolating the waste. Storing solid wastes by mixing them with fluids and injecting them into hydraulic fractures is a well-known technology. The essence of our idea differs from conventional hydraulic fracturing techniques only slightly in that it uses fracturing fluid heavier than the surrounding rock. This difference is fundamental, however, because it allows hydraulic fractures to propagate downward and carry wastes by gravity instead of or in addition to being injected by pumping. An example of similar gravity-driven fractures with positive buoyancy is given by magmatic dikes that may serve as an analog of Abyssal Sequestration occurring in nature. Mechanics of fracture propagation in conditions of positive (diking) and negative (heavy waste slurry) buoyancy is similar and considered in this work for both cases. Analog experiments in gelatin show that fracture breadth (horizontal dimension) remains nearly stationary when fracturing process in the fracture 'head' (where breadth is 'created') is dominated by solid toughness, as opposed to the viscous fluid dissipation dominant in the fracture tail. We model propagation of the resulting 'buoyant' or 'sinking' finger-like fracture of stationary breadth with slowly varying opening along the crack length. The elastic response of the crack to fluid loading in a horizontal cross-section is local and can be treated similar to the classical Perkins-Kern-Nordgren (PKN) model of hydraulic fracturing. The propagation condition for a finger-like crack is based on balancing the global energy release rate due to unit crack extension and the rock fracture toughness. It allows to relate the net fluid pressure at the tip to the fracture breadth and rock toughness. Unlike the PKN fracture, which breadth is known a priori, the final breadth of a finger-like fracture is a result of the fracturing process in the fracture head. To resolve the breadth, we relax the local elasticity assumption in the fracture head by neglecting viscous pressure drop there. The resulting fracture head model is a 3D analog of the Weertman's hydrostatic pulse, and yields expressions for the terminal breadth, b = 0.34 (K / Delta rho g))^(2/3), and for the head volume, V = 10.4 K b^(5/2) / E'. We then combine the finger crack solution for the viscous tail with the 3-D pulse solution for the fracture head. The obtained closed-form solution is compared to numerical simulations. Based on this solution, we analyzed the gravity fracture propagation in conditions of either continuous injection or finite volume release for sets of parameters representative of the heavy waste injection technique and low viscosity magma diking.

Leaching of TCIPP from furniture foam is rapid and substantial.

PubMed

Stubbings, William A; Harrad, Stuart

2018-02-01

A series of laboratory experiments were conducted, in which waste furniture polyurethane foam samples containing tris (1-chloro-2-propyl) phosphate (TCIPP) were contacted with a range of leaching fluids, formulated to simulate the composition of landfill leachate. Leaching was examined under a number of different scenarios, such as: dissolved humic matter concentration, pH, and temperature, as well as the effect of agitation, and waste:leaching fluid contact duration. In addition to single batch (no replenishment of leaching fluid), serial batch (draining of leachate and replenishment with fresh leaching fluid at various time intervals) experiments were conducted. Leaching of TCIPP from PUF appears to be a first order process. Concentrations of TCIPP in leachate generated by the experiments in this study ranged from 13 mg L -1 to 130 mg L -1 . In serial batch leaching experiments, >95% of TCIPP was depleted from PUF after 168 h total contact with leaching fluid. Our experiments indicate leaching is potentially a very significant pathway of TCIPP emissions to the environment. Copyright © 2017. Published by Elsevier Ltd.

Discrete fracture modeling of multiphase flow and hydrocarbon production in fractured shale or low permeability reservoirs

NASA Astrophysics Data System (ADS)

Hao, Y.; Settgast, R. R.; Fu, P.; Tompson, A. F. B.; Morris, J.; Ryerson, F. J.

2016-12-01

It has long been recognized that multiphase flow and transport in fractured porous media is very important for various subsurface applications. Hydrocarbon fluid flow and production from hydraulically fractured shale reservoirs is an important and complicated example of multiphase flow in fractured formations. The combination of horizontal drilling and hydraulic fracturing is able to create extensive fracture networks in low permeability shale rocks, leading to increased formation permeability and enhanced hydrocarbon production. However, unconventional wells experience a much faster production decline than conventional hydrocarbon recovery. Maintaining sustainable and economically viable shale gas/oil production requires additional wells and re-fracturing. Excessive fracturing fluid loss during hydraulic fracturing operations may also drive up operation costs and raise potential environmental concerns. Understanding and modeling processes that contribute to decreasing productivity and fracturing fluid loss represent a critical component for unconventional hydrocarbon recovery analysis. Towards this effort we develop a discrete fracture model (DFM) in GEOS (LLNL multi-physics computational code) to simulate multiphase flow and transfer in hydraulically fractured reservoirs. The DFM model is able to explicitly account for both individual fractures and their surrounding rocks, therefore allowing for an accurate prediction of impacts of fracture-matrix interactions on hydrocarbon production. We apply the DFM model to simulate three-phase (water, oil, and gas) flow behaviors in fractured shale rocks as a result of different hydraulic stimulation scenarios. Numerical results show that multiphase flow behaviors at the fracture-matrix interface play a major role in controlling both hydrocarbon production and fracturing fluid recovery rates. The DFM model developed in this study will be coupled with the existing hydro-fracture model to provide a fully integrated geomechanical and reservoir simulation capability for an accurate prediction and assessment of hydrocarbon production and hydraulic fracturing performance. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Modelling Laccoliths: Fluid-Driven Fracturing in the Lab

NASA Astrophysics Data System (ADS)

Ball, T. V.; Neufeld, J. A.

2017-12-01

Current modelling of the formation of laccoliths neglects the necessity to fracture rock layers for propagation to occur [1]. In magmatic intrusions at depth the idea of fracture toughness is used to characterise fracturing, however an analogue for near surface intrusions has yet to be explored [2]. We propose an analytical model for laccolith emplacement that accounts for the energy required to fracture at the tip of an intrusion. For realistic physical parameters we find that a lag region exists between the fluid magma front and the crack tip where large negative pressures in the tip cause volatiles to exsolve from the magma. Crucially, the dynamics of this tip region controls the spreading due to the competition between viscous forces and fracture energy. We conduct a series of complementary experiments to investigate fluid-driven fracturing of adhered layers and confirm the existence of two regimes: viscosity dominant spreading, controlled by the pressure in the lag region, and fracture energy dominant spreading, controlled by the energy required to fracture layers. Our experiments provide the first observations, and evolution, of a vapour tip. These experiments and our simplified model provide insight into the key physical processes in near surface magmatic intrusions with applications to fluid-driven fracturing more generally. Michaut J. Geophys. Res. 116(B5), B05205. Bunger & Cruden J. Geophys. Res. 116(B2), B02203.

Shallow fluid pressure transients caused by seismogenic normal faults

NASA Astrophysics Data System (ADS)

Fleischmann, Karl Henry

1993-10-01

Clastic dikes, induced by paleo-seismic slip along the Jonesboro Fault, can be used to estimate the magnitude of shallow fluid pressure transients. Fractures show evidence of two phases of seismically induced dilation by escaping fluids. Initial dilation and propagation through brittle rocks was caused by expulsion of trapped reducing fluids from beneath a clay cap. Second phase fluids were thixotropic clays which flowed vertically from clay beds upwards into the main fracture. Using the differential dilation and fracture trace lengths, the fluid pressure pulse is estimated to have ranged from 0.312-0.49 MPa, which is approximately equal to the vertical load during deformation. Field observations in adjacent rocks record evidence of large-magnitude seismic events, which are consistent with the large nature of the fluid pressure fluctuation.

Permeability evolution due to dissolution of natural shale fractures reactivated by fracking

NASA Astrophysics Data System (ADS)

Kwiatkowski, Kamil; Kwiatkowski, Tomasz; Szymczak, Piotr

2015-04-01

Investigation of cores drilled from gas-bearing shale formations reveals a relatively large number of calcite-cemented fractures. During fracking, some of these fractures will be reactivated [1-2] and may become important flow paths in the resulting fracture system. In this communication, we investigate numerically the effect of low-pH reactive fluid on such fractures. The low-pH fluids can either be pumped during the initial fracking stage (as suggested e.g. by Grieser et al., [3]) or injected later, as part of enhanced gas recovery (EGR) processes. In particular, it has been suggested that CO2 injection can be considered as a method of EGR [4], which is attractive as it can potentially be combined with simultaneous CO2 sequestration. However, when mixed with brine, CO2 becomes acidic and thus can be a dissolving agent for the carbonate cement in the fractures. The dissolution of the cement leads to the enhancement of permeability and interconnectivity of the fracture network and, as a result, increases the overall capacity of the reservoir. Importantly, we show that the dissolution of such fractures proceeds in a highly non-homogeneous manner - a positive feedback between fluid transport and mineral dissolution leads to the spontaneous formation of pronounced flow channels, frequently referred to as "wormholes". The wormholes carry the chemically active fluid deeper inside the system, which dramatically speeds up the overall permeability increase. If the low-pH fluids are used during fracking, then the non-uniform dissolution becomes important for retaining the fracture permeability, even in the absence of the proppant. Whereas a uniformly etched fracture will close tightly under the overburden once the fluid pressure is removed, the nonuniform etching will tend to maintain the permeability since the less dissolved regions will act as supports to keep more dissolved regions open. [1] Gale, J. F., Reed, R. M., Holder, J. (2007). Natural fractures in the Barnett Shale and their importance for hydraulic fracture treatments. AAPG bulletin, 91(4), 603-622. [2] Walton, I., & McLennan, J. (2013, May). The Role of Natural Fractures in Shale Gas Production. In ISRM International Conference for Effective and Sustainable Hydraulic Fracturing. International Society for Rock Mechanics. [3] Grieser, W. et al. "Surface Reactive Fluid's Effect on Shale." Proceedings of the Production and Operations Symposium, 31 March-3 April 2007, Oklahoma City (SPE-106815-MS) [4] Khosrokhavar, R., Griffiths, S., & Wolf, K. H. (2014). Shale Gas Formations and Their Potential for Carbon Storage: Opportunities and Outlook. Environmental Processes, 1(4), 595-611.

Cellular thermosetting fluoropolymers and process for making them

NASA Technical Reports Server (NTRS)

Lee, Sheng Y.

1988-01-01

Thermosetting fluoropolymer foams are made by mixing fluid from thermosetting fluoropolymer components having a substantial fluoride content, placing the mixture in a pressure tight chamber, filling the chamber with a gas, at a relatively low pressure, that is unreactive with the fluoropolymer components, allowing the mixture to gel, removing the gelled fluoropolymer from the chamber and therafter heating the fluoropolymer at a relatively low temperature to simultaneously cure and foam the fluoropolymer. The resulting fluoropolymer product is closed celled with the cells storing the gas employed for foaming. The fluoropolymer resins employed may be any thermosetting fluoropolymer including fluoroepoxies, fluoropolyurethanes and fluoroacrylates.

Cellular thermosetting fluorodiepoxide polymers

NASA Technical Reports Server (NTRS)

Lee, Sheng Y. (Inventor)

1989-01-01

Thermosetting fluoropolymer foams are made by mixing fluid form thermosetting fluoropolymer components having a substantial fluorine content, placing the mixture in a pressure tight chamber, filling the chamber with a gas, at relatively low pressure, that is unreactive with the fluoropolymer components, allowing the mixture to gel, removing the gelled fluoropolymer from the chamber and thereafter heating the fluoropolymer at a relatively low temperature to simultaneously sure and foam the fluoropolymer. The resulting fluoropolymer product is closed celled with the cells storing the gas employed for foaming. The fluoropolymer resins employed may be any thermosetting fluoropolymer including fluoroepoxies, fluoropolyurethanes and fluoroacrylates.

Laboratory hydraulic fracturing experiments in intact and pre-fractured rock

USGS Publications Warehouse

Zoback, M.D.; Rummel, F.; Jung, R.; Raleigh, C.B.

1977-01-01

Laboratory hydraulic fracturing experiments were conducted to investigate two factors which could influence the use of the hydrofrac technique for in-situ stress determinations; the possible dependence of the breakdown pressure upon the rate of borehole pressurization, and the influence of pre-existing cracks on the orientation of generated fractures. The experiments have shown that while the rate of borehole pressurization has a marked effect on breakdown pressures, the pressure at which hydraulic fractures initiate (and thus tensile strength) is independent of the rate of borehole pressurization when the effect of fluid penetration is negligible. Thus, the experiments indicate that use of breakdown pressures rather than fracture initiation pressures may lead to an erroneous estimate of tectonic stresses. A conceptual model is proposed to explain anomalously high breakdown pressures observed when fracturing with high viscosity fluids. In this model, initial fracture propagation is presumed to be stable due to large differences between the borehole pressure and that within the fracture. In samples which contained pre-existing fractures which were 'leaky' to water, we found it possible to generate hydraulic fractures oriented parallel to the direction of maximum compression if high viscosity drilling mud was used as the fracturing fluid. ?? 1977.

Water saturation effects on P-wave anisotropy in synthetic sandstone with aligned fractures

NASA Astrophysics Data System (ADS)

Amalokwu, Kelvin; Chapman, Mark; Best, Angus I.; Minshull, Timothy A.; Li, Xiang-Yang

2015-08-01

The seismic properties of rocks are known to be sensitive to partial liquid or gas saturation, and to aligned fractures. P-wave anisotropy is widely used for fracture characterization and is known to be sensitive to the saturating fluid. However, studies combining the effect of multiphase saturation and aligned fractures are limited even though such conditions are common in the subsurface. An understanding of the effects of partial liquid or gas saturation on P-wave anisotropy could help improve seismic characterization of fractured, gas bearing reservoirs. Using octagonal-shaped synthetic sandstone samples, one containing aligned penny-shaped fractures and the other without fractures, we examined the influence of water saturation on P-wave anisotropy in fractured rocks. In the fractured rock, the saturation related stiffening effect at higher water saturation values is larger in the direction across the fractures than along the fractures. Consequently, the anisotropy parameter `ε' decreases as a result of this fluid stiffening effect. These effects are frequency dependent as a result of wave-induced fluid flow mechanisms. Our observations can be explained by combining a frequency-dependent fractured rock model and a frequency-dependent partial saturation model.

Phase Field Model of Hydraulic Fracturing in Poroelastic Media: Fracture Propagation, Arrest, and Branching Under Fluid Injection and Extraction

NASA Astrophysics Data System (ADS)

Santillán, David; Juanes, Ruben; Cueto-Felgueroso, Luis

2018-03-01

The simulation of fluid-driven fracture propagation in a porous medium is a major computational challenge, with applications in geosciences and engineering. The two main families of modeling approaches are those models that represent fractures as explicit discontinuities and solve the moving boundary problem and those that represent fractures as thin damaged zones, solving a continuum problem throughout. The latter family includes the so-called phase field models. Continuum approaches to fracture face validation and verification challenges, in particular grid convergence, well posedness, and physical relevance in practical scenarios. Here we propose a new quasi-static phase field formulation. The approach fully couples fluid flow in the fracture with deformation and flow in the porous medium, discretizes flow in the fracture on a lower-dimension manifold, and employs the fluid flux between the fracture and the porous solid as coupling variable. We present a numerical assessment of the model by studying the propagation of a fracture in the quarter five-spot configuration. We study the interplay between injection flow rate and rock properties and elucidate fracture propagation patterns under the leak-off toughness dominated regime as a function of injection rate, initial fracture length, and poromechanical properties. For the considered injection scenario, we show that the final fracture length depends on the injection rate, and three distinct patterns are observed. We also rationalize the system response using dimensional analysis to collapse the model results. Finally, we propose some simplifications that alleviate the computational cost of the simulations without significant loss of accuracy.

Foam generation and sample composition optimization for the FOAM-C experiment of the ISS

NASA Astrophysics Data System (ADS)

Carpy, R.; Picker, G.; Amann, B.; Ranebo, H.; Vincent-Bonnieu, S.; Minster, O.; Winter, J.; Dettmann, J.; Castiglione, L.; Höhler, R.; Langevin, D.

2011-12-01

End of 2009 and early 2010 a sealed cell, for foam generation and observation, has been designed and manufactured at Astrium Friedrichshafen facilities. With the use of this cell, different sample compositions of "wet foams" have been optimized for mixtures of chemicals such as water, dodecanol, pluronic, aethoxisclerol, glycerol, CTAB, SDS, as well as glass beads. This development is performed in the frame of the breadboarding development activities of the Experiment Container FOAM-C for operation in the ISS Fluid Science Laboratory (ISS). The sample cell supports multiple observation methods such as: Diffusing-Wave and Diffuse Transmission Spectrometry, Time Resolved Correlation Spectroscopy [1] and microscope observation, all of these methods are applied in the cell with a relatively small experiment volume <3cm3. These units, will be on orbit replaceable sets, that will allow multiple sample compositions processing (in the range of >40).

Soft and Flexible Bilayer Thermoplastic Polyurethane Foam for Development of Bioinspired Artificial Skin.

PubMed

Li, Huan; Sinha, Tridib K; Oh, Jeong Seok; Kim, Jin Kuk

2018-04-25

Inspired by the epidermis-dermis composition of human skin, here we have simply developed a lightweight, robust, flexible, and biocompatible single-electrode triboelectric nanogenerator (S-TENG)-based prototype of bilayer artificial skin, by attaching one induction electrode with unfoamed skin layer of microcellular thermoplastic polyurethane (TPU) foam, which shows high-performance object manipulation [by responding differently toward different objects, viz., aluminum foil, balloon, cotton glove, human finger, glass, rubber glove, artificial leather, polyimide, poly(tetrafluoroethylene) (PTFE), paper, and wood], due to electrification and electrostatic induction during contact with the objects having different chemical functionalities. Comparative foaming behavior of ecofriendly supercritical fluids, viz., CO 2 over N 2 under variable temperatures (e.g., 130 and 150 °C) and constant pressure (15 MPa), have been examined here to pursue the soft and flexible triboelectric TPU foam. The foam derived by CO 2 foaming at 150 °C has been prioritized for development of S-TENG. Foam derived by CO 2 foaming at 130 °C did not respond as well due to the smaller cell size, higher hardness, and thicker skin. Inflexible N 2 -derived foam was not considered for S-TENG fabrication. Object manipulation performance has been visualized by principal component analysis (PCA), which shows good discrimination among responses to different objects.

Fabrication of cellular materials

NASA Astrophysics Data System (ADS)

Prud'homme, Robert K.; Aksay, Ilhan A.; Garg, Rajeev

1996-02-01

Nature uses cellular materials in applications requiring strength while, simultaneously, minimizing raw materials requirements. Minimizing raw materials is efficient both in terms of the energy expended by the organism to synthesize the structure and in terms of the strength- to-weight ratio of the structure. Wood is the most obvious example of cellular bio-materials, and it is the focus of other presentations in this symposium. The lightweight bone structure of birds is another excellent example where weight is a key criterion. The anchoring foot of the common muscle [Mytilus edulis] whereby it attaches itself to objects is a further example of a biological system that uses a foam to fill space and yet conserve on raw materials. In the case of the muscle the foam is water filled and the foot structure distributes stress over a larger area so that the strength of the byssal thread from which it is suspended is matched to the strength of interfacial attachment of the foot to a substrate. In these examples the synthesis and fabrication of the cellular material is directed by intercellular, genetically coded, biochemical reactions. The resulting cell sizes are microns in scale. Cellular materials at the next larger scale are created by organisms at the next higher level of integration. For example an African tree frog lays her eggs in a gas/fluid foam sack she builds on a branch overhanging a pond. The outside of the foam sack hardens in the sun and prevents water evaporation. The foam structure minimizes the amount of fluid that needs to be incorporated into the sack and minimizes its weight. However, as far as the developing eggs are concerned, they are in an aqueous medium, i.e. the continuous fluid phase of the foam. After precisely six days the eggs hatch, and the solidified outer wall re-liquefies and dumps the emerging tadpoles into the pond below. The bee honeycomb is an example of a cellular material with exquisite periodicity at millimeter length scales. The cellular structure provides strength through geometric regularity and functions as both honey storage vessels and incubators.

Numerical modeling of fracking fluid migration through fault zones and fractures in the North German Basin

NASA Astrophysics Data System (ADS)

Pfunt, Helena; Houben, Georg; Himmelsbach, Thomas

2016-09-01

Gas production from shale formations by hydraulic fracturing has raised concerns about the effects on the quality of fresh groundwater. The migration of injected fracking fluids towards the surface was investigated in the North German Basin, based on the known standard lithology. This included cases with natural preferential pathways such as permeable fault zones and fracture networks. Conservative assumptions were applied in the simulation of flow and mass transport triggered by a high pressure boundary of up to 50 MPa excess pressure. The results show no significant fluid migration for a case with undisturbed cap rocks and a maximum of 41 m vertical transport within a permeable fault zone during the pressurization. Open fractures, if present, strongly control the flow field and migration; here vertical transport of fracking fluids reaches up to 200 m during hydraulic fracturing simulation. Long-term transport of the injected water was simulated for 300 years. The fracking fluid rises vertically within the fault zone up to 485 m due to buoyancy. Progressively, it is transported horizontally into sandstone layers, following the natural groundwater flow direction. In the long-term, the injected fluids are diluted to minor concentrations. Despite the presence of permeable pathways, the injected fracking fluids in the reported model did not reach near-surface aquifers, either during the hydraulic fracturing or in the long term. Therefore, the probability of impacts on shallow groundwater by the rise of fracking fluids from a deep shale-gas formation through the geological underground to the surface is small.

Geochemical and Geomechanical Effects on Wellbore Cement Fractures

DOE PAGES

Um, Wooyong; Jung, Hun Bok; Kabilan, Senthil; ...

2014-12-31

Experimental studies were conducted using batch reactors, X-ray microtomograpy (XMT), and computational fluid dynamics (CFD) simulation to determine changes in cement fracture surfaces, fluid flow pathways, and permeability with geochemical and geomechanical processes. Composite Portland cement-basalt caprock core with artificial fractures was prepared and reacted with CO2-saturated groundwater at 50°C and 10 MPa for 3 to 3.5 months under static conditions to understand the geochemical and geomechanical effects on the integrity of wellbores containing defects. Cement-basalt interface samples were subjected to mechanical stress at 2.7 MPa before the CO2 reaction. XMT provided three-dimensional (3-D) visualization of the opening and interconnectionmore » of cement fractures due to mechanical stress. After the CO2 reaction, XMT images revealed that calcium carbonate precipitation occurred extensively within the fractures in the cement matrix, but only partially along fractures located at the cement-basalt interface. The permeability calculated based on CFD simulation was in agreement with the experimentally measured permeability. The experimental results imply that the wellbore cement with fractures is likely to be healed during exposure to CO2-saturated groundwater under static conditions, whereas fractures along the cement-caprock interface are still likely to remain vulnerable to the leakage of CO2. CFD simulation for the flow of different fluids (CO2-saturated brine and supercritical CO2) using a pressure difference of 20 kPa and 200 kPa along ~2 cm-long cement fractures showed that a pressure gradient increase resulted in an increase of CO2 fluids flux by a factor of only ~3-9 because the friction of CO2 fluids on cement fracture surfaces increased with higher flow rate as well. At the same pressure gradient, the simulated flow rate was higher for supercritical CO2 than CO2-saturated brine by a factor of only ~2-3, because the viscosity of supercritical CO2 is much lower than that of CO2-saturated brine. The study suggests that in deep geological reservoirs the geochemical and geomechanical processes have coupled effects on the wellbore cement fracture evolution and fluid flow along the fracture surfaces.« less

Stress dependence of permeability of intact and fractured shale cores.

NASA Astrophysics Data System (ADS)

van Noort, Reinier; Yarushina, Viktoriya

2016-04-01

Whether a shale acts as a caprock, source rock, or reservoir, understanding fluid flow through shale is of major importance for understanding fluid flow in geological systems. Because of the low permeability of shale, flow is thought to be largely confined to fractures and similar features. In fracking operations, fractures are induced specifically to allow for hydrocarbon exploration. We have constructed an experimental setup to measure core permeabilities, using constant flow or a transient pulse. In this setup, we have measured the permeability of intact and fractured shale core samples, using either water or supercritical CO2 as the transporting fluid. Our measurements show decreasing permeability with increasing confining pressure, mainly due to time-dependent creep. Furthermore, our measurements show that for a simple splitting fracture, time-dependent creep will also eliminate any significant effect of this fracture on permeability. This effect of confinement on fracture permeability can have important implications regarding the effects of fracturing on shale permeability, and hence for operations depending on that.

Thermal-hydraulic performance of metal foam heat exchangers under dry operating conditions

DOE PAGES

Nawaz, Kashif; Bock, Jessica; Jacobi, Anthony M.

2017-03-14

High porosity metal foams with novel thermal, mechanical, electrical, and acoustic properties are being more widely adopted for application. Due to their large surface-area-to-volume ratio and complex structure which induces better fluid mixing, boundary layer restarting and wake destruction, they hold promise for heat transfer applications. In this study, the thermal-hydraulic performance of open-cell aluminum metal foam heat exchanger has been evaluated. The impact of flow conditions and metal foam geometry on the heat transfer coefficient and gradient have been investigated. Metal foam heat exchanger with same geometry (face area, flow depth and fin dimensions) consisting of four different typemore » of metal foams have been built for the study. Experiments are conducted in a closed-loop wind tunnel at different flow rate under dry operating condition. Metal foams with a smaller pore size (40 PPI) have a larger heat transfer coefficient compared to foams with a larger pore size (5 PPI). However, foams with larger pores result in relatively smaller pressure gradients. Current thermal-hydraulic modeling practices have been reviewed and potential issues have been identified. Permeability and inertia coefficients are determined and compared to data reported in open literature. Finally, on the basis of the new experimental results, correlations are developed relating the foam characteristics and flow conditions through the friction factor f and the Colburn j factor.« less

Thermal-hydraulic performance of metal foam heat exchangers under dry operating conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nawaz, Kashif; Bock, Jessica; Jacobi, Anthony M.

High porosity metal foams with novel thermal, mechanical, electrical, and acoustic properties are being more widely adopted for application. Due to their large surface-area-to-volume ratio and complex structure which induces better fluid mixing, boundary layer restarting and wake destruction, they hold promise for heat transfer applications. In this study, the thermal-hydraulic performance of open-cell aluminum metal foam heat exchanger has been evaluated. The impact of flow conditions and metal foam geometry on the heat transfer coefficient and gradient have been investigated. Metal foam heat exchanger with same geometry (face area, flow depth and fin dimensions) consisting of four different typemore » of metal foams have been built for the study. Experiments are conducted in a closed-loop wind tunnel at different flow rate under dry operating condition. Metal foams with a smaller pore size (40 PPI) have a larger heat transfer coefficient compared to foams with a larger pore size (5 PPI). However, foams with larger pores result in relatively smaller pressure gradients. Current thermal-hydraulic modeling practices have been reviewed and potential issues have been identified. Permeability and inertia coefficients are determined and compared to data reported in open literature. Finally, on the basis of the new experimental results, correlations are developed relating the foam characteristics and flow conditions through the friction factor f and the Colburn j factor.« less

Impact of fluid-rock chemical interactions on tracer transport in fractured rocks.

PubMed

Mukhopadhyay, Sumit; Liu, H-H; Spycher, N; Kennedy, B M

2013-11-01

In this paper, we investigate the impact of chemical interactions, in the form of mineral precipitation and dissolution reactions, on tracer transport in fractured rocks. When a tracer is introduced in fractured rocks, it moves through the fracture primarily by advection and it also enters the stagnant water of the surrounding rock matrix through diffusion. Inside the porous rock matrix, the tracer chemically interacts with the solid materials of the rock, where it can precipitate depending on the local equilibrium conditions. Alternatively, it can be dissolved from the solid phase of the rock matrix into the matrix pore water, diffuse into the flowing fluids of the fracture and is advected out of it. We show that such chemical interactions between the fluid and solid phases have significant impact on tracer transport in fractured rocks. We invoke the dual-porosity conceptualization to represent the fractured rocks and develop a semi-analytical solution to describe the transient transport of tracers in interacting fluid-rock systems. To test the accuracy and stability of the semi-analytical solution, we compare it with simulation results obtained with the TOUGHREACT simulator. We observe that, in a chemically interacting system, the tracer breakthrough curve exhibits a pseudo-steady state, where the tracer concentration remains more or less constant over a finite period of time. Such a pseudo-steady condition is not observed in a non-reactive fluid-rock system. We show that the duration of the pseudo-state depends on the physical and chemical parameters of the system, and can be exploited to extract information about the fractured rock system, such as the fracture spacing and fracture-matrix interface area. © 2013.

Compressive Properties of Metal Matrix Syntactic Foams in Free and Constrained Compression

NASA Astrophysics Data System (ADS)

Orbulov, Imre Norbert; Májlinger, Kornél

2014-06-01

Metal matrix syntactic foam (MMSF) blocks were produced by an inert gas-assisted pressure infiltration technique. MMSFs are advanced hollow sphere reinforced-composite materials having promising application in the fields of aviation, transport, and automotive engineering, as well as in civil engineering. The produced blocks were investigated in free and constrained compression modes, and besides the characteristic mechanical properties, their deformation mechanisms and failure modes were studied. In the tests, the chemical composition of the matrix material, the size of the reinforcing ceramic hollow spheres, the applied heat treatment, and the compression mode were considered as investigation parameters. The monitored mechanical properties were the compressive strength, the fracture strain, the structural stiffness, the fracture energy, and the overall absorbed energy. These characteristics were strongly influenced by the test parameters. By the proper selection of the matrix and the reinforcement and by proper design, the mechanical properties of the MMSFs can be effectively tailored for specific and given applications.

4D synchrotron X-ray imaging to understand porosity development in shales during exposure to hydraulic fracturing fluid

NASA Astrophysics Data System (ADS)

Kiss, A. M.; Bargar, J.; Kohli, A. H.; Harrison, A. L.; Jew, A. D.; Lim, J. H.; Liu, Y.; Maher, K.; Zoback, M. D.; Brown, G. E.

2016-12-01

Unconventional (shale) reservoirs have emerged as the most important source of petroleum resources in the United States and represent a two-fold decrease in greenhouse gas emissions compared to coal. Despite recent progress, hydraulic fracturing operations present substantial technical, economic, and environmental challenges, including inefficient recovery, wastewater production and disposal, contaminant and greenhouse gas pollution, and induced seismicity. A relatively unexplored facet of hydraulic fracturing operations is the fluid-rock interface, where hydraulic fracturing fluid (HFF) contacts shale along faults and fractures. Widely used, water-based fracturing fluids contain oxidants and acid, which react strongly with shale minerals. Consequently, fluid injection and soaking induces a host of fluid-rock interactions, most notably the dissolution of carbonates and sulfides, producing enhanced or "secondary" porosity networks, as well as mineral precipitation. The competition between these mechanisms determines how HFF affects reactive surface area and permeability of the shale matrix. The resultant microstructural and chemical changes may also create capillary barriers that can trap hydrocarbons and water. A mechanistic understanding of the microstructure and chemistry of the shale-HFF interface is needed to design new methodologies and fracturing fluids. Shales were imaged using synchrotron micro-X-ray computed tomography before, during, and after exposure to HFF to characterize changes to the initial 3D structure. CT reconstructions reveal how the secondary porosity networks advance into the shale matrix. Shale samples span a range of lithologies from siliceous to calcareous to organic-rich. By testing shales of different lithologies, we have obtained insights into the mineralogic controls on secondary pore network development and the morphologies at the shale-HFF interface and the ultimate composition of produced water from different facies. These results show that mineral texture is a major control over secondary porosity network morphology.

Microbial Community Changes in Hydraulic Fracturing Fluids and Produced Water from Shale Gas Extraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohan, Arvind Murali; Hartsock, Angela; Bibby, Kyle J

2013-11-19

Microbial communities associated with produced water from hydraulic fracturing are not well understood, and their deleterious activity can lead to significant increases in production costs and adverse environmental impacts. In this study, we compared the microbial ecology in prefracturing fluids (fracturing source water and fracturing fluid) and produced water at multiple time points from a natural gas well in southwestern Pennsylvania using 16S rRNA gene-based clone libraries, pyrosequencing, and quantitative PCR. The majority of the bacterial community in prefracturing fluids constituted aerobic species affiliated with the class Alphaproteobacteria. However, their relative abundance decreased in produced water with an increase inmore » halotolerant, anaerobic/facultative anaerobic species affiliated with the classes Clostridia, Bacilli, Gammaproteobacteria, Epsilonproteobacteria, Bacteroidia, and Fusobacteria. Produced water collected at the last time point (day 187) consisted almost entirely of sequences similar to Clostridia and showed a decrease in bacterial abundance by 3 orders of magnitude compared to the prefracturing fluids and produced water samplesfrom earlier time points. Geochemical analysis showed that produced water contained higher concentrations of salts and total radioactivity compared to prefracturing fluids. This study provides evidence of long-term subsurface selection of the microbial community introduced through hydraulic fracturing, which may include significant implications for disinfection as well as reuse of produced water in future fracturing operations.« less

Hydraulic Fracturing for Oil and Gas: Impacts from the ...

EPA Pesticide Factsheets

This final report provides a review and synthesis of available scientific information concerning the relationship between hydraulic fracturing activities and drinking water resources in the United States. The report is organized around activities in the hydraulic fracturing water cycle and their potential to impact drinking water resources.  The stages include: (1) acquiring water to be used for hydraulic fracturing (Water Acquisition), (2) mixing the water with chemical additives to prepare hydraulic fracturing fluids (Chemical Mixing), (3) injecting the hydraulic fracturing fluids into the production well to create fractures in the targeted production zone (Well Injection), (4) collecting the wastewater that returns through the well after injection (Produced Water Handling), and (5) managing the wastewater via disposal or reuse methods (Wastewater Disposal and Reuse). EPA found scientific evidence that hydraulic fracturing activities can impact drinking water resources under some circumstances. The report identifies certain conditions under which impacts from hydraulic fracturing activities can be more frequent or severe: Water withdrawals for hydraulic fracturing in times or areas of low water availability, particularly in areas with limited or declining groundwater resources; Spills during the handling of hydraulic fracturing fluids and chemicals or produced water that result in large volumes or high concentrations of chem

Study on fracturing flowback fluid treatment technology for shale gas in Yangzhou

NASA Astrophysics Data System (ADS)

Shi, Shengwei; Du, Jiajia; Kang, Dingyu; Chen, Xinjian; Qu, Chengtun; Yu, Tao

2018-02-01

Shale gas fracturing flowback fluid has the characteristics of high viscosity, large displacement, complex components and difficult to deal with. Therefore, it is of great significance for environmental protection to treat and reuse it. In this paper, Yangzhou shale gas is taken as an object to study the treatment of shale gas fracturing flowback fluid. The results shown that the viscosity of the fracturing flowback fluid before treatment was 16.75mPa·s, and when the pH was adjusted to 3.5, with Cerium(III) sulfate and ferrous sulfate as catalyst and the dosage were 60mg/L and 120 mg/L respectively, and hydrogen peroxide dosage was 0.5%, the viscosity of fracturing folwback fluid was reduced from 16.75mPa·s to 1.97mPa·s After the oxidation treatment, adjusting pH to 7.5, and treating it with inorganic flocculant and organic flocculant, the water quality met the reinjection requirement of the average air permeability of less than or equal to 0.01 μm2.

Experimental Observation of Dispersion Phenomenon for Non-Newtonian flow in Porous Media

NASA Astrophysics Data System (ADS)

Bowers, C.; Schultz, P. B.; Fowler, C. P.; McClure, J. E.; Miller, C. T.

2017-12-01

The EPA has identified over 100 toxic species which are commonly found in hydraulic fracturing fluids, leading to concerns about their movement into endangered water supplies through spills and accelerated geological pathways. Before these concerns can be allayed, detailed study of the transport of dissolved species in non-Newtonian fluids is required. Up until now, most research into non-Newtonian flow has focused on two-parameter models, such as the Power law model; however, these models have been found to be insufficient when applied to hydraulic fracturing applications, due to high pressure flow through thin fractures and pore-throats. This work is focused on the Cross model, a four parameter model which has been found to accurately represent the flow of fracturing fluids. A series of one-dimensional flow through tracer tests have been conducted using a tritiated water tracer and an aqueous guar gum solution, a non-Newtonian fluid commonly used in the fracturing process, to investigate the effects of dispersion on species transport. These tests are compared to modeling results, and may be used to develop macroscale models for Cross model non-Newtonian fluids.

Analysis of Effective Interconnectivity of DegraPol-foams Designed for Negative Pressure Wound Therapy

PubMed Central

Milleret, Vincent; Bittermann, Anne Greet; Mayer, Dieter; Hall, Heike

2009-01-01

Many wounds heal slowly and are difficult to manage. Therefore Negative Pressure Wound Therapy (NPWT) was developed where polymer foams are applied and a defined negative pressure removes wound fluid, reduces bacterial burden and increases the formation of granulation tissue. Although NPWT is used successfully, its mechanisms are not well understood. In particular, different NPWT dressings were never compared. Here a poly-ester urethane Degrapol® (DP)-foam was produced and compared with commercially available dressings (polyurethane-based and polyvinyl-alcohol-based) in terms of apparent pore sizes, swelling and effective interconnectivity of foam pores. DP-foams contain relatively small interconnected pores; PU-foams showed large pore size and interconnectivity; whereas PVA-foams displayed heterogeneous and poorly interconnected pores. PVA-foams swelled by 40 %, whereas DP- and PU-foams remained almost without swelling. Effective interconnectivity was investigated by submitting fluorescent beads of 3, 20 and 45 μm diameter through the foams. DP- and PU-foams removed 70-90 % of all beads within 4 h, independent of the bead diameter or bead pre-adsorption with serum albumin. For PVA-foams albumin pre-adsorbed beads circulated longer, where 20 % of 3 μm and 10 % of 20 μm diameter beads circulated after 96 h. The studies indicate that efficient bead perfusion does not only depend on pore size and swelling capacity, but effective interconnectivity might also depend on chemical composition of the foam itself. In addition due to the efficient sieve-effect of the foams uptake of wound components in vivo might occur only for short time suggesting other mechanisms being decisive for success of NPWT.

Failure of cap-rock seals as determined from mechanical stratigraphy, stress history, and tensile-failure analysis of exhumed analogs

DOE PAGES

Petrie, E. S.; Evans, J. P.; Bauer, S. J.

2014-11-01

In this study, the sedimentologic and tectonic histories of clastic cap rocks and their inherent mechanical properties control the nature of permeable fractures within them. The migration of fluid through mm- to cm-scale fracture networks can result in focused fluid flow allowing hydrocarbon production from unconventional reservoirs or compromising the seal integrity of fluid traps. To understand the nature and distribution of subsurface fluid-flow pathways through fracture networks in cap-rock seals we examine four exhumed Paleozoic and Mesozoic seal analogs in Utah. We combine these outcrop analyses with subsidence analysis, paleoloading histories, and rock-strength testing data in modified Mohr–Coulomb–Griffith analysesmore » to evaluate the effects of differential stress and rock type on fracture mode.« less

Adjustable Polyurethane Foam as Filling Material for a Novel Spondyloplasty: Biomechanics and Biocompatibility.

PubMed

Jiang, Hongzhen; Sitoci-Ficici, Kerim Hakan; Reinshagen, Clemens; Molcanyi, Marek; Zivcak, Jozef; Hudak, Radovan; Laube, Thorsten; Schnabelrauch, Matthias; Weisser, Jürgen; Schäfer, Ute; Pinzer, Thomas; Schackert, Gabriele; Zhang, Xifeng; Wähler, Mario; Brautferger, Uta; Rieger, Bernhard

2018-04-01

To investigate the biomechanics and biocompatibility of polyurethane (PU) foam with adjustable stiffness as a filling material for a novel spondyloplasty that is designed to reduce the risk of postoperative adjacent level fractures. Sixty individual porcine lumbar vertebrae were randomly split into 4 groups: A, B, C, and D. Group A served as unmodified vertebral body controls. Groups B, C, and D consisted of hollowed vertebral bodies. Vertebrae of groups C and D were filled with adjustable PU foams of different stiffness. The compressive strength and stiffness of vertebrae from groups A-D were recorded and analyzed. 3T3 mouse fibroblasts were cultured with preformed PU foams for 4 days to test biocompatibility. The strength and stiffness of the hollowed groups were lower than in group A. However, the differences were not statistically significant between group A and group C (P > 0.05), and were obviously different between group A and group B or group D (P < 0.01 and <0.05, respectively). Moreover, the strength and stiffness after filling foams in group C or group D were significantly greater than in group B (P < 0.01 and <0.05, respectively). Live/dead staining of 3T3 cells confirmed the biocompatibility of the PU foam. The new PU foam shows adaptability regarding its stiffness and excellent cytocompatibility in vitro. The results support the clinical translation of the new PU foams as augmentation material in the development of a novel spondyloplasty. Copyright © 2018 Elsevier Inc. All rights reserved.

Genetic research of fractures in carbonate reservoir: a case study of NT carbonate reservoir in the pre-Caspian basin

NASA Astrophysics Data System (ADS)

Fan, Zifei; Wang, Shuqin; Li, Jianxin; Zhao, Wenqi; Sun, Meng; Li, Weiqiang; Li, Changhai

2018-02-01

The degree of development and characteristics of fractures are key factors for the appraisal of carbonate reservoirs. In this paper, core data and well logging data from the NT oilfield in the Pre-Caspian Basin are used to study the formation mechanism and distribution characteristics of different genetic fractures, and analyze their influence on reservoir properties. Fractures in carbonate reservoirs can be divided into three categories according to their formation mechanism; these are tectonic fracture, dissolved fracture, and diagenetic fracture,which is further divided into interlayer fracture and stylolite. Fractures of different formation mechanism influence fluid seepage in different degree, tectonic fractures possessing strong connecting ability to pores, and dissolved fractures also improving reservoir properties effectively, however, diagenetic fractures contributing relatively little to fluid seepage.

Assessment of the Potential Impacts of Hydraulic Fracturing for ...

EPA Pesticide Factsheets

This assessment provides a review and synthesis of available scientific literature and data to assess the potential for hydraulic fracturing for oil and gas to impact the quality or quantity of drinking water resources, and identifies factors affecting the frequency or severity of any potential impacts. The scope of this assessment is defined by the hydraulic fracturing water cycle which includes five main activities: Water acquisition – the withdrawal of ground or surface water needed for hydraulic fracturing fluids;Chemical mixing – the mixing of water, chemicals, and proppant on the well pad to create the hydraulic fracturing fluid;Well injection – the injection of hydraulic fracturing fluids into the well to fracture the geologic formation; Flowback and Produced water – the return of injected fluid and water produced from the formation to the surface, and subsequent transport for reuse, treatment, or disposal; andWastewater treatment and waste disposal – the reuse, treatment and release, or disposal of wastewater generated at the well pad, including produced water. This report can be used by federal, tribal, state, and local officials; industry; and the public to better understand and address vulnerabilities of drinking water resources to hydraulic fracturing activities. To assess the potential impacts of hydraulic fracturing on drinking water resources, if any, and to identify the driving factors that may affect the severity and frequency of s

Symptomatic relevance of intravertebral cleft in patients with osteoporotic vertebral fracture.

PubMed

Kawaguchi, Satoshi; Horigome, Keiko; Yajima, Hideki; Oda, Takashi; Kii, Yuichiro; Ida, Kazunori; Yoshimoto, Mitsunori; Iba, Kousuke; Takebayashi, Tsuneo; Yamashita, Toshihiko

2010-08-01

The present study was designed to determine clinical and radiographic characteristics of unhealed osteoporotic vertebral fractures (OVFs) and the role of fracture mobility and an intravertebral cleft in the regulation of pain symptoms in patients with an OVF. Patients who had persistent low-back pain for 3 months or longer and a collapsed thoracic or lumbar vertebra that had an intervertebral cleft and abnormal mobility were referred to as having unhealed OVFs. Twenty-four patients with an unhealed OVF and 30 patients with an acute OVF were compared with regard to several clinical and radiographic features including the presence of an intravertebral fluid sign. Subsequently, the extent of dynamic mobility of the fractured vertebra was analyzed for correlation with the patients' age, duration of symptoms, back pain visual analog scale (VAS) score, and performance status. Finally, in cases of unhealed OVFs, the subgroup of patients with positive fluid signs was compared with the subgroup of patients with negative fluid signs. Patients with an unhealed OVF were more likely to have a crush-type fracture, shorter vertebral height of the fractured vertebra, and a fracture with a positive fluid sign than those with an acute OVF. The extent of dynamic mobility of the vertebra correlated significantly with the VAS score in patients with an unhealed OVF. In addition, a significant correlation with the extent of dynamic vertebral mobility with performance status was seen in patients with an unhealed OVF and those with an acute OVF. Of the 24 patients with an unhealed OVF, 14 had a positive fluid sign in the affected vertebra. Patients with a positive fluid sign exhibited a statistically significantly greater extent of dynamic vertebral mobility, a higher VAS score, a higher performance status grade, and a greater likelihood of having a crush-type fracture than those with a negative fluid sign. All but 1 patient with an unhealed OVF and a positive fluid sign had an Eastern Cooperative Oncology Group Performance Status Grade 3 or 4 (bedridden most or all of the time). In sharp contrast, all 10 patients with an unhealed OVF and a negative fluid sign were Grade 1 or 2. Unhealed OVFs form a group of fractures that are distinct from acute OVFs regarding radiographic morphometry and contents of the intravertebral cleft. Dynamic vertebral mobility serves as a primal pain determinant in patients with an unhealed OVF and potentially in those with an acute OVF. Fluid accumulation in the intravertebral cleft of unhealed OVFs likely reflects long-term bedridden positioning of the patients in daily activity.

3D convection in a fractured porous medium : influence of fracture network parameters and comparison to homogeneous approach.

NASA Astrophysics Data System (ADS)

Mezon, Cécile; Mourzenko, Valeri; François Thovert, Jean; Antoine, Raphael; Fontaine, Fabrice; Finizola, Anthony; Adler, Pierre Michel

2016-04-01

In the crust, fractures/faults can provide preferential pathways for fluid flow or act as barriers preventing the flow across these structures. In hydrothermal systems (usually found in fractured rock masses), these discontinuities may play a critical role at various scales, controlling fluid flows and heat transfer. The thermal convection is numerically computed in 3D fluid satured isotropically fractured porous media. Fractures are inserted as 2D convex polygons, which are randomly located. The fluid is assumed to satisfy 2D and 3D Darcy's law in the fractures and in the porous medium, respectively; exchanges take place between these two structures. First, checks were performed on an unfractured porous medium and the convection cells do start for the theoretical value of Ra, namely 4pi². 2D convection was verified up to Ra=800. Second, all fractured simulations were made for Rayleigh numbers (Ra) < 150, cubic boxes and closed-top conditions. The influence of parameters such as fracture aperture (or fracture transmissivity) and fracture density on the heat released by the whole system is studied. Then, the effective permeability of each fractured system is calculated. This last calculation enables the comparison between all fractured models and models of homogeneous medium with the same macroscopic properties. First, the heat increase released by the system as a function of fracture transmissivity and fracture density is determined. Second, results show that the effective approach is valid for low Ra (< 70), and that the mismatch between the full calculations and the effective medium approach for Ra higher than 70 depends on the fracture density in a crucial way. Third, the study also reveals that equivalent properties could be deduced from these computations in order to estimate the heat released by a fractured system from an homogeneous approach.

The inverse problem of acoustic wave scattering by an air-saturated poroelastic cylinder.

PubMed

Ogam, Erick; Fellah, Z E A; Baki, Paul

2013-03-01

The efficient use of plastic foams in a diverse range of structural applications like in noise reduction, cushioning, and sleeping mattresses requires detailed characterization of their permeability and deformation (load-bearing) behavior. The elastic moduli and airflow resistance properties of foams are often measured using two separate techniques, one employing mechanical vibration methods and the other, flow rates of fluids based on fluid mechanics technology, respectively. A multi-parameter inverse acoustic scattering problem to recover airflow resistivity (AR) and mechanical properties of an air-saturated foam cylinder is solved. A wave-fluid saturated poroelastic structure interaction model based on the modified Biot theory and plane-wave decomposition using orthogonal cylindrical functions is employed to solve the inverse problem. The solutions to the inverse problem are obtained by constructing the objective functional given by the total square of the difference between predictions from the model and scattered acoustic field data acquired in an anechoic chamber. The value of the recovered AR is in good agreement with that of a slab sample cut from the cylinder and characterized using a method employing low frequency transmitted and reflected acoustic waves in a long waveguide developed by Fellah et al. [Rev. Sci. Instrum. 78(11), 114902 (2007)].

On the Feasibility of Very-Low-Density Pure Metal Foams as Bright High-Energy X-ray Sources

NASA Astrophysics Data System (ADS)

Colvin, Jeffrey; Felter, Thomas

2003-10-01

We have used the Busquet approximation (M. Busquet, Phys. Fluids B 5(11), 4191 (1993)) to explore calculationally what the possible x-ray conversion efficiencies into the K-band would be from irradiating very-low-density pure metal foams with tens of kilojoules of 1/3-micron laser light. We will discuss the advantages of pure metal foams as bright high-energy x-ray sources, and some results of this calculational study. We will also present our ideas for how to fabricate pure metal foams with densities of a few milligrams per cubic centimeter. This work was performed under the auspices of the US Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

The seismogenic Gole Larghe Fault Zone (Italian Southern Alps): quantitative 3D characterization of the fault/fracture network, mapping of evidences of fluid-rock interaction, and modelling of the hydraulic structure through the seismic cycle

NASA Astrophysics Data System (ADS)

Bistacchi, A.; Mittempergher, S.; Di Toro, G.; Smith, S. A. F.; Garofalo, P. S.

2016-12-01

The Gole Larghe Fault Zone (GLFZ) was exhumed from 8 km depth, where it was characterized by seismic activity (pseudotachylytes) and hydrous fluid flow (alteration halos and precipitation of hydrothermal minerals in veins and cataclasites). Thanks to glacier-polished outcrops exposing the 400 m-thick fault zone over a continuous area > 1.5 km2, the fault zone architecture has been quantitatively described with an unprecedented detail, providing a rich dataset to generate 3D Discrete Fracture Network (DFN) models and simulate the fault zone hydraulic properties. The fault and fracture network has been characterized combining > 2 km of scanlines and semi-automatic mapping of faults and fractures on several photogrammetric 3D Digital Outcrop Models (3D DOMs). This allowed obtaining robust probability density functions for parameters of fault and fracture sets: orientation, fracture intensity and density, spacing, persistency, length, thickness/aperture, termination. The spatial distribution of fractures (random, clustered, anticlustered…) has been characterized with geostatistics. Evidences of fluid/rock interaction (alteration halos, hydrothermal veins, etc.) have been mapped on the same outcrops, revealing sectors of the fault zone strongly impacted, vs. completely unaffected, by fluid/rock interaction, separated by convolute infiltration fronts. Field and microstructural evidence revealed that higher permeability was obtained in the syn- to early post-seismic period, when fractures were (re)opened by off-fault deformation. We have developed a parametric hydraulic model of the GLFZ and calibrated it, varying the fraction of faults/fractures that were open in the post-seismic, with the goal of obtaining realistic fluid flow and permeability values, and a flow pattern consistent with the observed alteration/mineralization pattern. The fraction of open fractures is very close to the percolation threshold of the DFN, and the permeability tensor is strongly anisotropic, resulting in a marked channelling of fluid flow in the inner part of the fault zone. Amongst possible seismological applications of our study, we will discuss the possibility to evaluate the coseismic fracture intensity due to off-fault damage, a fundamental mechanical parameter in the energy balance of earthquakes.

A case-controlled, retrospective, comparative study on the use of biodegradable synthetic polyurethane foam versus polyvinyl acetate sponge after nasal fracture reduction.

PubMed

Jeong, H-S; Lee, H-K; Kim, H-S; Moon, M-S; Tark, K-C

2014-06-01

One of the most frequently used packing materials in closed reduction of a nasal bone fracture is the hydroxylated polyvinyl acetate sponge (PVAS; Merocel(®)); however this may cause synechia, epistaxis, and pain. Synthetic polyurethane foam (SPF; Nasopore(®) Forte) has recently been used in septoplasty to prevent synechia or restenosis and haematoma formation. The purpose of this study was to compare the effects of PVAS and SPF on postoperative appearance and discomfort following the reduction of nasal bone fractures. We retrospectively reviewed all patient questionnaires and medical histories, and clinical photographs and computed tomography scans obtained before and after surgery. Outcomes were assessed using the Global Aesthetic Improvement Scale (GAIS) score and visual analogue scale (VAS) scores, which were used to assess discomfort during the 6-month follow-up period. Postoperatively, there was no statistically significant difference in the GAIS for the two packing materials (P > 0.05). Postoperative epistaxis was observed at a significantly lower rate in the SPF group than in the PVAS group, whereas anterior rhinorrhea and posterior nasal drip occurred at significantly higher rates following removal of packing in the SPF group (P < 0.05). The results of this study suggest that synthetic dissolvable polyurethane may be a reliable alternative material for nasal packing and postoperative management following the reduction of nasal bone fractures. Copyright © 2014 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

RANS Simulations using OpenFOAM Software

DTIC Science & Technology

2016-01-01

Averaged Navier- Stokes (RANS) simulations is described and illustrated by applying the simpleFoam solver to two case studies; two dimensional flow...to run in parallel over large processor arrays. The purpose of this report is to illustrate and test the use of the steady-state Reynolds Averaged ...Group in the Maritime Platforms Division he has been simulating fluid flow around ships and submarines using finite element codes, Lagrangian vortex

The Effect of Cushion Properties on Skin Temperature and Humidity at the Body-Support Interface.

PubMed

Hsu, Tzu-Wen; Yang, Shu-Yu; Liu, Jung-Tai; Pan, Cheng-Tang; Yang, Yu-Sheng

2016-09-29

To explore the effects of various cushions on skin temperature and moisture at the body-seat interface during a 2-h period of continuous sitting. Seventy-eight participants were randomly assigned to sit on one of the three types of wheelchair cushion for unrelieved sitting over 2 h. Skin temperature and relative humidity (RH) were measured under the subjects' ischial tuberosities and thighs bilaterally with digital temperature and humidity sensors. Data were collected before sitting and at 15-min intervals thereafter. Participants sitting on foam-fluid hybrid cushions showed significantly lower skin temperatures than those sitting on air-filled and foam cushions (p < 0.05), but RH did not differ significantly among the cushions (p = 0.97). The three cushions produced a similar increasing trend in RH over time and RH reached a plateau during the 2-h sitting period. In order to select the appropriate wheelchair cushion, the microclimate (heat and moisture control) between the body-seat interface should be considered as well as pressure distribution. In comparison with foam-fluid hybrid cushions, the air-filled rubber and foam cushions tended to increase skin temperature by several degrees after prolonged sitting. However, cushion materials did not have significant differences in moisture accumulations.

The effect of cushion properties on skin temperature and humidity at the body-support interface.

PubMed

Hsu, Tzu-Wen; Yang, Shu-Yu; Liu, Jung-Tai; Pan, Cheng-Tang; Yang, Yu-Sheng

2016-09-29

The purpose of this study is to explore the effects of various cushions on skin temperature and moisture at the body-seat interface during a 2-hour period of continuous sitting. Seventy-eight participants were randomly assigned to sit on one of the three types of wheelchair cushions for unrelieved sitting for over 2 hours. Skin temperature and relative humidity (RH) were measured under the subjects' ischial tuberosities and thighs bilaterally with digital temperature and humidity sensors. Data were collected before sitting and at 15-minute intervals thereafter. Participants sitting on foam-fluid hybrid cushions showed significantly lower skin temperatures than those sitting on air-filled and foam cushions (p < 0.05), but RH did not differ significantly among the cushions (p = 0.97). The three cushions produced a similar increasing trend in RH over time and RH reached a plateau during the 2-hour sitting period. To select the appropriate wheelchair cushion, the microclimate (heat and moisture control) between the body-seat interface should be considered as well as pressure distribution. In comparison with foam-fluid hybrid cushions, the air-filled rubber and foam cushions tended to increase skin temperature by several degrees after prolonged sitting. However, cushion materials did not have significant differences in moisture accumulations.

Foam Flow Through a 2D Porous Medium: Evolution of the Bubble Size Distribution

NASA Astrophysics Data System (ADS)

Meheust, Y.; Géraud, B.; Cantat, I.; Dollet, B.

2017-12-01

Foams have been used for decades as displacing fluids for EOR and aquifer remediation, and more recently as carriers of chemical amendments for remediation of the vadose zone. Bulk foams are shear-thinning fluids; but for foams with bubbles of order at least the typical pore size of the porous medium, the rheology cannot be described at the continuum scale, as viscous dissipation occurs mostly at the contact between soap films and solid walls. We have investigated the flow of an initially monodisperse foam through a transparent 2D porous medium[1]. The resulting complex flow phenomenology has been characterized quantitatively from optical measurements of the bubble dynamics. In addition to preferential flow path and local flow intermittency, we observe an irreversible evolution of the probability density function (PDF) for bubbles size as bubbles travel along the porous medium. This evolution is due to bubble fragmentation by lamella division, which is by far the dominant mechanism of film creation/destruction. We measure and characterize this evolution of the PDF as a function of the experimental parameters, and model it numerically based on a fragmentation equation, with excellent agreement. The model uses two ingredients obtained from the experimental data, namely the statistics of the bubble fragmentation rate and of the fragment size distributions[2]. It predicts a nearly-universal scaling of all PDFs as a function of the bubble area normalized by the initial mean bubble area. All the PDFs measured in various experiments, with different mean flow velocities, initial bubble sizes and foam qualities, collapse on a master distribution which is only dependent on the geometry of the medium.References:[1] B. Géraud, S. A. Jones, I. Cantat, B. Dollet & Y. Méheust (2016), WRR 52(2), 773-790. [2] B. Géraud, Y. Méheust, I. Cantat & B. Dollet (2017), Lamella division in a foam flowing through a two-dimensional porous medium: A model fragmentation process, PRL 118, 098003.

Apparatus and method for handling magnetic particles in a fluid

DOEpatents

Holman, David A.; Grate, Jay W.; Bruckner-Lea, Cynthia J.

2000-01-01

The present invention is an apparatus and method for handling magnetic particles suspended in a fluid, relying upon the known features of a magnetic flux conductor that is permeable thereby permitting the magnetic particles and fluid to flow therethrough; and a controllable magnetic field for the handling. The present invention is an improvement wherein the magnetic flux conductor is a monolithic porous foam.

A Comprehensive Numerical Model for Simulating Fluid Transport in Nanopores

PubMed Central

Zhang, Yuan; Yu, Wei; Sepehrnoori, Kamy; Di, Yuan

2017-01-01

Since a large amount of nanopores exist in tight oil reservoirs, fluid transport in nanopores is complex due to large capillary pressure. Recent studies only focus on the effect of nanopore confinement on single-well performance with simple planar fractures in tight oil reservoirs. Its impacts on multi-well performance with complex fracture geometries have not been reported. In this study, a numerical model was developed to investigate the effect of confined phase behavior on cumulative oil and gas production of four horizontal wells with different fracture geometries. Its pore sizes were divided into five regions based on nanopore size distribution. Then, fluid properties were evaluated under different levels of capillary pressure using Peng-Robinson equation of state. Afterwards, an efficient approach of Embedded Discrete Fracture Model (EDFM) was applied to explicitly model hydraulic and natural fractures in the reservoirs. Finally, three fracture geometries, i.e. non-planar hydraulic fractures, non-planar hydraulic fractures with one set natural fractures, and non-planar hydraulic fractures with two sets natural fractures, are evaluated. The multi-well performance with confined phase behavior is analyzed with permeabilities of 0.01 md and 0.1 md. This work improves the analysis of capillarity effect on multi-well performance with complex fracture geometries in tight oil reservoirs. PMID:28091599

A Comprehensive Numerical Model for Simulating Fluid Transport in Nanopores

NASA Astrophysics Data System (ADS)

Zhang, Yuan; Yu, Wei; Sepehrnoori, Kamy; di, Yuan

2017-01-01

Since a large amount of nanopores exist in tight oil reservoirs, fluid transport in nanopores is complex due to large capillary pressure. Recent studies only focus on the effect of nanopore confinement on single-well performance with simple planar fractures in tight oil reservoirs. Its impacts on multi-well performance with complex fracture geometries have not been reported. In this study, a numerical model was developed to investigate the effect of confined phase behavior on cumulative oil and gas production of four horizontal wells with different fracture geometries. Its pore sizes were divided into five regions based on nanopore size distribution. Then, fluid properties were evaluated under different levels of capillary pressure using Peng-Robinson equation of state. Afterwards, an efficient approach of Embedded Discrete Fracture Model (EDFM) was applied to explicitly model hydraulic and natural fractures in the reservoirs. Finally, three fracture geometries, i.e. non-planar hydraulic fractures, non-planar hydraulic fractures with one set natural fractures, and non-planar hydraulic fractures with two sets natural fractures, are evaluated. The multi-well performance with confined phase behavior is analyzed with permeabilities of 0.01 md and 0.1 md. This work improves the analysis of capillarity effect on multi-well performance with complex fracture geometries in tight oil reservoirs.

Seismic Characterizations of Fractures: Dynamic Diagnostics

NASA Astrophysics Data System (ADS)

Pyrak-Nolte, L. J.

2017-12-01

Fracture geometry controls fluid flow in a fracture, affects mechanical stability and influences energy partitioning that affects wave scattering. Our ability to detect and monitor fracture evolution is controlled by the frequency of the signal used to probe a fracture system, i.e. frequency selects the scales. No matter the frequency chosen, some set of discontinuities will be optimal for detection because different wavelengths sample different subsets of fractures. The select subset of fractures is based on the stiffness of the fractures which in turn is linked to fluid flow. A goal is obtaining information from scales outside the optimal detection regime. Fracture geometry trajectories are a potential approach to drive a fracture system across observation scales, i.e. moving systems between effective medium and scattering regimes. Dynamic trajectories (such as perturbing stress, fluid pressure, chemical alteration, etc.) can be used to perturb fracture geometry to enhance scattering or give rise to discrete modes that are intimately related to the micro-structural evolution of a fracture. However, identification of these signal features will require methods for identifying these micro-structural signatures in complicated scattered fields. Acknowledgment: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Geosciences Research Program under Award Number (DE-FG02-09ER16022).

Shale gas and non-aqueous fracturing fluids: Opportunities and challenges for supercritical CO₂

DOE PAGES

Middleton, Richard S.; Carey, James William; Currier, Robert P.; ...

2015-06-01

Hydraulic fracturing of shale formations in the United States has led to a domestic energy boom. Currently, water is the only fracturing fluid regularly used in commercial shale oil and gas production. Industry and researchers are interested in non-aqueous working fluids due to their potential to increase production, reduce water requirements, and to minimize environmental impacts. Using a combination of new experimental and modeling data at multiple scales, we analyze the benefits and drawbacks of using CO₂ as a working fluid for shale gas production. We theorize and outline potential advantages of CO₂ including enhanced fracturing and fracture propagation, reductionmore » of flow-blocking mechanisms, increased desorption of methane adsorbed in organic-rich parts of the shale, and a reduction or elimination of the deep re-injection of flow-back water that has been linked to induced seismicity and other environmental concerns. We also examine likely disadvantages including costs and safety issues associated with handling large volumes of supercritical CO₂. The advantages could have a significant impact over time leading to substantially increased gas production. In addition, if CO₂ proves to be an effective fracturing fluid, then shale gas formations could become a major utilization option for carbon sequestration.« less

The Role of Electrical Anisotropy in Modeling and Interpreting Controlled-Source Electromagnetic Responses for Hydraulic Fracture Monitoring

NASA Astrophysics Data System (ADS)

Trevino, S., III; Hickey, M. S.; Everett, M. E.

2017-12-01

Controlled-Source Electromagnetics (CSEM) can be used to monitor the movement and extent of injection fluid during a hydraulic fracture. The response of the fluid to energization by a CSEM source is dependent upon the electrical conductivity difference between the fluid and background geological formation. An important property that must be taken into account when modeling and interpreting CSEM responses is that electrical conductivity may be anisotropic. We study the effect of electrical anisotropy in both the background formation and the fluid-injection zone. First, various properties of the background formation can affect anisotropy including variations in grain size, composition and bedding-plane orientation. In certain formations, such as shale, the horizontal component of the conductivity can be more than an order of magnitude larger than the vertical component. We study this effect by computing differences in surface CSEM responses using the analytic 1-D anisotropic primary solution of a horizontal electric dipole positioned at the surface. Second, during hydraulic fracturing, the injected fluid can create new fractures and infill existing natural fractures. To include the explicit fracture geometry in modeling, a large increase in the number of nodes and computational time is required which may not be feasible. An alternative is to instead model the large-scale fracture geometry as a uniform slab with an appropriate bulk conductivity. Micro-scale fracture geometry may cause preferential fluid propagation in a single direction or plane which can be represented by electrical anisotropy of the slab. To study such effects of bulk anisotropy on CSEM responses we present results from multiple scenarios of surface to surface hydraulic fracture monitoring using 3-D finite element modeling. The model uses Coulomb-gauged potentials to solve Maxwell's equations in the frequency domain and we have updated the code to allow a triaxial electrical conductivity tensor to be specified. By allowing for formation and target electrical anisotropy these modeling results contribute to a better understanding and faster interpretation of field data.

An Embedded 3D Fracture Modeling Approach for Simulating Fracture-Dominated Fluid Flow and Heat Transfer in Geothermal Reservoirs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnston, Henry; Wang, Cong; Winterfeld, Philip

An efficient modeling approach is described for incorporating arbitrary 3D, discrete fractures, such as hydraulic fractures or faults, into modeling fracture-dominated fluid flow and heat transfer in fractured geothermal reservoirs. This technique allows 3D discrete fractures to be discretized independently from surrounding rock volume and inserted explicitly into a primary fracture/matrix grid, generated without including 3D discrete fractures in prior. An effective computational algorithm is developed to discretize these 3D discrete fractures and construct local connections between 3D fractures and fracture/matrix grid blocks of representing the surrounding rock volume. The constructed gridding information on 3D fractures is then added tomore » the primary grid. This embedded fracture modeling approach can be directly implemented into a developed geothermal reservoir simulator via the integral finite difference (IFD) method or with TOUGH2 technology This embedded fracture modeling approach is very promising and computationally efficient to handle realistic 3D discrete fractures with complicated geometries, connections, and spatial distributions. Compared with other fracture modeling approaches, it avoids cumbersome 3D unstructured, local refining procedures, and increases computational efficiency by simplifying Jacobian matrix size and sparsity, while keeps sufficient accuracy. Several numeral simulations are present to demonstrate the utility and robustness of the proposed technique. Our numerical experiments show that this approach captures all the key patterns about fluid flow and heat transfer dominated by fractures in these cases. Thus, this approach is readily available to simulation of fractured geothermal reservoirs with both artificial and natural fractures.« less

Using well casing as an electrical source to monitor hydraulic fracture fluid injection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilt, Michael; Nieuwenhuis, Greg; MacLennan, Kris

2016-03-09

The depth to surface resistivity (DSR) method transmits current from a source located in a cased or openhole well to a distant surface return electrode while electric field measurements are made at the surface over the target of interest. This paper presents both numerical modelling results and measured data from a hydraulic fracturing field test where conductive water was injected into a resistive shale reservoir during a hydraulic fracturing operation. Modelling experiments show that anomalies due to hydraulic fracturing are small but measureable with highly sensitive sensor technology. The field measurements confirm the model results,showing that measured differences in themore » surface fields due to hydraulic fracturing have been detected above the noise floor. Our results show that the DSR method is sensitive to the injection of frac fluids; they are detectable above the noise floor in a commercially active hydraulic fracturing operation, and therefore this method can be used for monitoring fracture fluid movement.« less

Along fault friction and fluid pressure effects on the spatial distribution of fault-related fractures

NASA Astrophysics Data System (ADS)

Maerten, Laurent; Maerten, Frantz; Lejri, Mostfa

2018-03-01

Whatever the processes involved in the natural fracture development in the subsurface, fracture patterns are often affected by the local stress field during propagation. This homogeneous or heterogeneous local stress field can be of mechanical and/or tectonic origin. In this contribution, we focus on the fracture-pattern development where active faults perturb the stress field, and are affected by fluid pressure and sliding friction along the faults. We analyse and geomechanically model two fractured outcrops in UK (Nash Point) and in France (Les Matelles). We demonstrate that the observed local radial joint pattern is best explained by local fluid pressure along the faults and that observed fracture pattern can only be reproduced when fault friction is very low (μ < 0.2). Additionally, in the case of sub-vertical faults, we emphasize that the far field horizontal stress ratio does not affect stress trajectories, or fracture patterns, unless fault normal displacement (dilation or contraction) is relatively large.

Investigation of heat transfer of tube line of staggered tube bank in two-phase flow

NASA Astrophysics Data System (ADS)

Jakubcionis, Mindaugas

2015-06-01

This article presents the results of experimental investigation of heat transfer process, carried out using the model of heat exchanger. Two-phase statically stable foam flow was used as a heat transfer fluid. Heat exchanger model consisted of staggered tube bank. Experimental results are presented with the focus on influence of tube position in the line of the bank, volumetric void component and velocity of gas component of the foam. The phenomena of liquid draining in cellular foam flow and its influence on heat transfer rate has also been discussed. The experimental results have been generalized by relationship between Nusselt, Reynolds and Prandtl numbers.

Transport and Clogging of Particulate Flow in Fracture Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koplik, Joel

The aim of the project is to understand the effects of confinement in narrow rough-walled fractures on the transport behavior of fluids and suspended particles in subsurface hydro- carbon reservoirs. A key motivation for the study is that such fracture systems provide the highest throughput in oil and gas extraction and have been the focus of recent industrial activity. The scientific challenge is to understand how the confined geometry alters transport phenomena, and in particular its influence on (diagnostic) tracer transport and the effects of flow channeling and clogging on fluid motion. An important complicating feature of geological fractures ismore » the self-affine fractal nature of their surface roughness, leading to irregular but correlated fluid and particle motion. The key technique used is computer simulation, augmented by analytical calculations and collaboration with outside experimental colleagues when possible. The principal topics studied were fluid permeability, tracer dispersion, flow channeling and anisotropy, particle transport in narrow channels and particle trapping in tight fractures.« less

Damping of liquid sloshing by foams

NASA Astrophysics Data System (ADS)

Sauret, A.; Boulogne, F.; Cappello, J.; Dressaire, E.; Stone, H. A.

2015-02-01

When a container is set in motion, the free surface of the liquid starts to oscillate or slosh. Such effects can be observed when a glass of water is handled carelessly and the fluid sloshes or even spills over the rims of the container. However, beer does not slosh as readily as water, which suggests that foam could be used to damp sloshing. In this work, we study experimentally the effect on sloshing of a liquid foam placed on top of a liquid bath. We generate a monodisperse two-dimensional liquid foam in a rectangular container and track the motion of the foam. The influence of the foam on the sloshing dynamics is experimentally characterized: only a few layers of bubbles are sufficient to significantly damp the oscillations. We rationalize our experimental findings with a model that describes the foam contribution to the damping coefficient through viscous dissipation on the walls of the container. Then we extend our study to confined three-dimensional liquid foam and observe that the behavior of 2D and confined 3D systems are very similar. Thus, we conclude that only the bubbles close to the walls have a significant impact on the dissipation of energy. The possibility to damp liquid sloshing using foam is promising in numerous industrial applications such as the transport of liquefied gas in tankers or for propellants in rocket engines.

Effect of crumb-rubber particle size on mechanical response of polyurethane foam composites

NASA Astrophysics Data System (ADS)

Sanjay, Omer Sheik

The compression properties of foam are governed by by three factors: i) cell edge bending ii) compression of cell fluid iii) membrane stresses in the cell faces. The effect of reinforcement, granular form of scrap tire rubber on contribution of each of these effects along with the physical properties of polyurethane foam is investigated. It is seen that the addition of crumb-rubber hinders the formation of cell membranes during the foaming process. Four different sizes of particles were chosen to closely study the effect of particle size on the physical properties of the foam composite. There is a definite pattern seen in each of the physical property of the composite with change in the particle size. Addition of crumb-rubber decreases the compressive strength but in turn increases the elastic modulus of the composite. The rubber particles act as the sites for stress concentration and hence the inclusion of rubber particles induces the capability to transfer the axial load laterally along the surface of the foam. Also, the filler material induces porosity into the foam, which is seen in the SEM images, and hence the addition of rubber particles induces brittleness, which makes the foam composites extensively applicable for structural application in sandwich components. The lightweight composite therefore is a potential substitute to the heavier metal foams and honeycombs as a protective layer.

A comparison of the in vitro moisture vapour transmission rate and in vivo fluid-handling capacity of six adhesive foam dressings to a newly reformulated adhesive foam dressing.

PubMed

Zehrer, Cindy L; Holm, David; Solfest, Staci E; Walters, Shelley-Ann

2014-12-01

This study compared moisture vapour transmission rate (MVTR) and wear time or fluid-handling capacities of six adhesive foam dressings to a reformulated control dressing. Standardised in vitro MVTR methodology and a previously published in vivo artificial wound model (AWM) were used. Mean inverted MVTR for the reformulated dressing was 12 750 g/m(2) /24 hours and was significantly higher than four of the six comparator dressings (P < 0·0001), which ranged from 830 to 11 360 g/m(2) /24 hours. Mean upright MVTR for the reformulated dressing was 980 g/m(2) /24 hours and was significantly different than all of the comparator dressings (P < 0·0001), which ranged from 80 to 1620 g/m(2) /24 hours (three higher/three lower). The reformulated dressing median wear time ranged from 6·1 to >7·0 days, compared with 1·0 to 3·5 days for the comparator dressings (P = 0·0012 to P < 0·0001). The median fluid volume handled ranged from 78·0 to >87 ml compared with 13·0 to 44·5 ml for the comparator dressings (P = 0·0007 to P < 0·001). Interestingly, inverted MVTR did not correspond well to the AWM. These results suggest that marked differences exist between the dressings in terms of both MVTR and wear time or fluid-handling capacity. Furthermore, high inverted MVTR does not necessarily predict longer wear time or fluid-handling capacities of absorbent dressings. © 2013 The Authors. International Wound Journal © 2013 Medicalhelplines.com Inc and John Wiley & Sons Ltd.

Analogue modelling of caprock failure and sediment mobilisation due to pore fluid overpressure in shallow reservoirs

NASA Astrophysics Data System (ADS)

Warsitzka, Michael; Kukowski, Nina; May, Franz

2017-04-01

Injection of CO2 in geological formations may cause excess pore fluid pressure by enhancing the fluid volume in the reservoir rock and by buoyancy-driven flow. If sediments in the reservoir and the caprock are undercompacted, pore fluid overpressure can lead to hydro-fractures in the caprock and fluidisation of sediments. Eventually, these processes trigger the formation of pipe structures, gas chimneys, gas domes or sand injections. Generally, such structures serve as high permeable pathways for fluid migration through a low-permeable seal layer and have to be considered in risk assessment or modelling of caprock integrity of CO2 storage sites. We applied scaled analogue experiments to characterise and quantify mechanisms determining the onset and migration of hydro-fractures in a low-permeable, cohesive caprock and fluidisation of unconsolidated sediments of the reservoir layer. The caprock is simulated by different types of cohesive powder. The reservoir layer consists of granulates with small particle density. Air injected through the base of the experiment and additionally through a single needle valve reaching into the analogue material is applied to generate fluid pressure within the materials. With this procedure, regional fluid pressure increase or a point-like local fluid pressure increase (e.g. injection well), respectively, can be simulated. The deformation in the analogue materials is analysed with a particle tracking imaging velocimetry technique. Pressure sensors at the base of the experiment and in the needle valve record the air pressure during an experimental run. The structural evolution observed in the experiments reveal that the cohesive cap rock first forms a dome-like anticline. Extensional fractures occur at the hinges of the anticline. A further increase of fluid pressure causes a migration of this fractures towards the surface, which is followed by intrusion of reservoir material into the fractures and the collapse of the anticline. The breakthrough of the fractures at the surface is accompanied by a significant drop of air pressure at the base of the analogue materials. The width of the dome shaped uplift is narrower and the initiating fluid pressure in the needle valve is lower, if the fluid pressure at the base of the experiment is larger. The experimental outcomes help to evaluate if the injection of CO2 into a reservoir potentially provokes initiation or reactivation of fractures and sediment mobilisation structures.

Sources and drains: Major controls of hydrothermal fluid flow in the Kokanee Range, British Columbia, Canada

NASA Astrophysics Data System (ADS)

Beaudoin, Georges; Therrien, René

1999-10-01

Vein fields are fractured domains of the lithosphere that have been infiltrated by hydrothermal fluids, which deposited minerals in response to changing physico-chemical conditions. Because oxygen is a major component of the infiltrating fluid and the surrounding rock matrix, the oxygen isotope composition of minerals found in veins is used to decipher ancient fluid flow within the lithosphere. We use a numerical model to simulate oxygen isotope transport in the Kokanee Range silver-lead-zinc vein field. The model considers advective, dispersive, and reactive transport in a three-dimensional porous rock matrix intersected by high-permeability planes representing fracture zones. Here we show that it is the geometrical configuration of the sources and of the drains of hydrothermal fluids, combined with the fracture pattern, that exerts the main control on the oxygen isotope distribution. Other factors that affect, to a lesser extent, the values and positions of oxygen isopleths are the fluids and rock-matrix isotopic compositions, the isotopic fractionation, the reaction rate constant, and hydraulic conductivities of the rock matrix and fracture zones.

Roughness-Dominated Hydraulic Fracture Propagation

NASA Astrophysics Data System (ADS)

Garagash, D.

2015-12-01

Current understanding suggests that the energy to propagate a hydraulic fracture is defined by the viscous fluid pressure drop along the fracture channel, while the energy dissipation in the immediate vicinity of the fracture front (i.e. fracture toughness) is negligible. This status quo relies on the assumption of Poiseuille flow in the fracture, which transmissivity varies as cube of the aperture. We re-evaluate this assumption in the vicinity of the fracture tip, where the aperture roughness and/or branching of the fracture path may lead to very significant deviations from the cubic law. Existing relationships suggest rough fracture transmissivity power laws ~ wr with 4.5 ≤ r ≤ 6, when aperture w is smaller than the roughness. Solving for the tip region of a steadily propagating hydraulic fracture with the "rough fracture" transmissivity, we are able to show (a) larger energy dissipation than predicted by the Poiseuille flow model; (b) localization of the fluid pressure drop into the low-transmissivity, rough tip region; and (c) emergence of potentially preeminent "toughness-dominated" fracture propagation regime where most of the energy is dissipated at the tip and can be described in the context of classical fracture mechanics by invoking the effective fracture toughness dependent upon the details of the pressure drop in the rough tip. We establish that the ratio of the roughness scale wc to the viscous aperture scale wμ = μVE / σ02, controls the pressure drop localization. (Here V - propagation speed, μ - fluid viscosity, E - rock modulus, and σ0 - in-situ stress). For a range of industrial fracturing fluids (from slick-water to linear gels) and treatment conditions, wc/wμ is large, suggesting a fully-localized pressure drop and energy dissipation. The latter is adequately described by the effective toughness - a function of the propagation velocity, confining stress and material parameters, which estimated values are much larger than the "dry" rock fracture toughness measured in the lab. Using the effective, velocity-dependent fracture toughness to predict the evolution of a penny-shape fracture, we are able to show how/when the classical viscosity-dominated and toughness-dominated solutions based upon the Poiseuille law and the "dry", laboratory fracture toughness values, respectively, may become inadequate.

Multiphase flow models for hydraulic fracturing technology

NASA Astrophysics Data System (ADS)

Osiptsov, Andrei A.

2017-10-01

The technology of hydraulic fracturing of a hydrocarbon-bearing formation is based on pumping a fluid with particles into a well to create fractures in porous medium. After the end of pumping, the fractures filled with closely packed proppant particles create highly conductive channels for hydrocarbon flow from far-field reservoir to the well to surface. The design of the hydraulic fracturing treatment is carried out with a simulator. Those simulators are based on mathematical models, which need to be accurate and close to physical reality. The entire process of fracture placement and flowback/cleanup can be conventionally split into the following four stages: (i) quasi-steady state effectively single-phase suspension flow down the wellbore, (ii) particle transport in an open vertical fracture, (iii) displacement of fracturing fluid by hydrocarbons from the closed fracture filled with a random close pack of proppant particles, and, finally, (iv) highly transient gas-liquid flow in a well during cleanup. The stage (i) is relatively well described by the existing hydralics models, while the models for the other three stages of the process need revisiting and considerable improvement, which was the focus of the author’s research presented in this review paper. For stage (ii), we consider the derivation of a multi-fluid model for suspension flow in a narrow vertical hydraulic fracture at moderate Re on the scale of fracture height and length and also the migration of particles across the flow on the scale of fracture width. At the stage of fracture cleanaup (iii), a novel multi-continua model for suspension filtration is developed. To provide closure relationships for permeability of proppant packings to be used in this model, a 3D direct numerical simulation of single phase flow is carried out using the lattice-Boltzmann method. For wellbore cleanup (iv), we present a combined 1D model for highly-transient gas-liquid flow based on the combination of multi-fluid and drift-flux approaches. The derivation of the drift-flux model from conservation olaws is criticall revisited in order to define the list of underlying assumptions and to mark the applicability margins of the model. All these fundamental problems share the same technological application (hydraulic fracturing) and the same method of research, namely, the multi-fluid approach to multiphase flow modeling and the consistent use of asymptotic methods. Multi-fluid models are then discussed in comparison with semi-empirical (often postulated) models widely used in the industry.

Seismic waves in rocks with fluids and fractures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berryman, J.G.

2007-05-14

Seismic wave propagation through the earth is often stronglyaffected by the presence of fractures. When these fractures are filledwith fluids (oil, gas, water, CO2, etc.), the type and state of the fluid(liquid or gas) can make a large difference in the response of theseismic waves. This paper summarizes recent work on methods ofdeconstructing the effects of fractures, and any fluids within thesefractures, on seismic wave propagation as observed in reflection seismicdata. One method explored here is Thomsen's weak anisotropy approximationfor wave moveout (since fractures often induce elastic anisotropy due tononuniform crack-orientation statistics). Another method makes use ofsome very convenient fracturemore » parameters introduced previously thatpermit a relatively simple deconstruction of the elastic and wavepropagation behavior in terms of a small number of fracture parameters(whenever this is appropriate, as is certainly the case for small crackdensities). Then, the quantitative effects of fluids on thesecrack-influence parameters are shown to be directly related to Skempton scoefficient B of undrained poroelasticity (where B typically ranges from0 to 1). In particular, the rigorous result obtained for the low crackdensity limit is that the crack-influence parameters are multiplied by afactor (1 ? B) for undrained systems. It is also shown how fractureanisotropy affects Rayleigh wave speed, and how measured Rayleigh wavespeeds can be used to infer shear wave speed of the fractured medium.Higher crack density results are also presented by incorporating recentsimulation data on such cracked systems.« less

Environmental risks associated with unconventional gas extraction: an Australian perspective

NASA Astrophysics Data System (ADS)

Mallants, Dirk; Bekele, Elise; Schmidt, Wolfgang; Miotlinski, Konrad; Gerke Gerke, Kirill

2015-04-01

Coal seam gas is naturally occurring methane gas (CH4) formed by the degradation of organic material in coal seam layers over geological times, typically over several millions of years. Unlike conventional gas resources, which occur as discrete accumulations in traps formed by folds and other structures in sedimentary layers, coal seam gas is generally trapped in low permeable rock by adsorption of the gas molecules within the rock formation and cannot migrate to a trap and form a conventional gas deposit. Extraction of coal seam gas requires producers to de pressurise the coal measures by abstracting large amounts of groundwater through pumping. For coal measures that have too low permeabilities for gas extraction to be economical, mechanical and chemical techniques are required to increase permeability and thus gas yield. One such technique is hydraulic fracturing (HF). Hydraulic fracturing increases the rate and total amount of gas extracted from coal seam gas reservoirs. The process of hydraulic fracturing involves injecting large volumes of hydraulic fracturing fluids under high pressure into the coal seam layers to open up (i.e. fracture) the gas-containing coal layers, thus facilitating extraction of methane gas through pumping. After a hydraulic fracturing operation has been completed in a coal seam gas well, the fracturing fluid pressure is lowered and a significant proportion of the injected fluid returns to the surface as "flowback" water via coal seam gas wells. Flowback water is fluid that returns to the surface after hydraulic fracturing has occurred but before the well is put into production; whereas produced water is fluid from the coal measure that is pumped to the surface after the well is in production. This paper summarises available literature data from Australian coal seam gas practices on i) spills from hydraulic fracturing-related fluids used during coal seam gas drilling and hydraulic fracturing operations, ii) leaks to soil and shallow groundwater of flowback water and produced water from surface impoundments, iii) risks from well integrity failure, and iv) increased gas in water bores.

Overview of Chronic Oral Toxicity Values for Chemicals Present in Hydraulic Fracturing Fluids, Flowback, and Produced Waters.

PubMed

Yost, Erin E; Stanek, John; DeWoskin, Robert S; Burgoon, Lyle D

2016-05-03

Concerns have been raised about potential public health effects that may arise if hydraulic fracturing-related chemicals were to impact drinking water resources. This study presents an overview of the chronic oral toxicity values-specifically, chronic oral reference values (RfVs) for noncancer effects, and oral slope factors (OSFs) for cancer-that are available for a list of 1173 chemicals that the United States (U.S.) Environmental Protection Agency (EPA) identified as being associated with hydraulic fracturing, including 1076 chemicals used in hydraulic fracturing fluids and 134 chemicals detected in flowback or produced waters from hydraulically fractured wells. The EPA compiled RfVs and OSFs using six governmental and intergovernmental data sources. Ninety (8%) of the 1076 chemicals reported in hydraulic fracturing fluids and 83 (62%) of the 134 chemicals reported in flowback/produced water had a chronic oral RfV or OSF available from one or more of the six sources. Furthermore, of the 36 chemicals reported in hydraulic fracturing fluids in at least 10% of wells nationwide (identified from EPA's analysis of the FracFocus Chemical Disclosure Registry 1.0), 8 chemicals (22%) had an available chronic oral RfV. The lack of chronic oral RfVs and OSFs for the majority of these chemicals highlights the significant knowledge gap that exists to assess the potential human health hazards associated with hydraulic fracturing.

Fracture stimulation treatment design optimization: What can the NPV vs X{sub f} plot tell us?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huffman, C.H.; Harkrider, J.D.; Thompson, R.S.

1996-12-31

Fracture stimulation production response coupled with the hydrocarbon sales price determines the value of a fracture stimulation treatment. Many factors can significantly effect the production response of a fracture stimulated well. Some examples include stimulation fluid selection, proppant selection, pumping rates, rock properties, reservoir fluid properties, in-situ stresses, stress variations, on-site execution, post-treatment stimulation fluid recovery, and operating practices. The production response in economic terms portrays the net effect of these variables. This paper presents a case study that demonstrates how post-treatment evaluations expressed in economic terms can be used to assess the performance of stimulations and to guide futuremore » design choices.« less

Bacterial communities associated with hydraulic fracturing fluids in thermogenic natural gas wells in North Central Texas, USA.

PubMed

Struchtemeyer, Christopher G; Elshahed, Mostafa S

2012-07-01

Hydraulic fracturing is used to increase the permeability of shale gas formations and involves pumping large volumes of fluids into these formations. A portion of the frac fluid remains in the formation after the fracturing process is complete, which could potentially contribute to deleterious microbially induced processes in natural gas wells. Here, we report on the geochemical and microbiological properties of frac and flowback waters from two newly drilled natural gas wells in the Barnett Shale in North Central Texas. Most probable number studies showed that biocide treatments did not kill all the bacteria in the fracturing fluids. Pyrosequencing-based 16S rRNA diversity analyses indicated that the microbial communities in the flowback waters were less diverse and completely distinct from the communities in frac waters. These differences in frac and flowback water communities appeared to reflect changes in the geochemistry of fracturing fluids that occurred during the frac process. The flowback communities also appeared well adapted to survive biocide treatments and the anoxic conditions and high temperatures encountered in the Barnett Shale. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

THERMO-HYDRO-MECHANICAL MODELING OF WORKING FLUID INJECTION AND THERMAL ENERGY EXTRACTION IN EGS FRACTURES AND ROCK MATRIX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robert Podgorney; Chuan Lu; Hai Huang

2012-01-01

Development of enhanced geothermal systems (EGS) will require creation of a reservoir of sufficient volume to enable commercial-scale heat transfer from the reservoir rocks to the working fluid. A key assumption associated with reservoir creation/stimulation is that sufficient rock volumes can be hydraulically fractured via both tensile and shear failure, and more importantly by reactivation of naturally existing fractures (by shearing), to create the reservoir. The advancement of EGS greatly depends on our understanding of the dynamics of the intimately coupled rock-fracture-fluid-heat system and our ability to reliably predict how reservoirs behave under stimulation and production. Reliable performance predictions ofmore » EGS reservoirs require accurate and robust modeling for strongly coupled thermal-hydrological-mechanical (THM) processes. Conventionally, these types of problems have been solved using operator-splitting methods, usually by coupling a subsurface flow and heat transport simulators with a solid mechanics simulator via input files. An alternative approach is to solve the system of nonlinear partial differential equations that govern multiphase fluid flow, heat transport, and rock mechanics simultaneously, using a fully coupled, fully implicit solution procedure, in which all solution variables (pressure, enthalpy, and rock displacement fields) are solved simultaneously. This paper describes numerical simulations used to investigate the poro- and thermal- elastic effects of working fluid injection and thermal energy extraction on the properties of the fractures and rock matrix of a hypothetical EGS reservoir, using a novel simulation software FALCON (Podgorney et al., 2011), a finite element based simulator solving fully coupled multiphase fluid flow, heat transport, rock deformation, and fracturing using a global implicit approach. Investigations are also conducted on how these poro- and thermal-elastic effects are related to fracture permeability evolution.« less

Hydraulic fracturing in granite under geothermal conditions

USGS Publications Warehouse

Solberg, P.; Lockner, D.; Byerlee, J.D.

1980-01-01

The experimental hydraulic fracturing of granite under geothermal conditions produces tensile fracture at rapid fluid injection rates and shear fracture at slow injection rates and elevated differential stress levels. A sudden burst of acoustic emission activity accompanies tensile fracture formation whereas the acoustic emission rate increases exponentially prior to shear fracture. Temperature does not significantly affect the failure mechanism, and the experimental results have not demonstrated the occurrence of thermal fracturing. A critical result of these experiments is that fluid injection at intermediate rates and elevated differential stress levels increases permeability by more than an order of magnitude without producing macroscopic fractures, and low-level acoustic emission activity occurs simultaneously near the borehole and propagates outward into the specimen with time. Permeability measurements conducted at atmospheric pressure both before and after these experiments show that increased permeability is produced by permanent structural changes in the rock. Although results of this study have not demonstrated the occurrence of thermal fracturing, they suggest that fluid injection at certain rates in situ may markedly increase local permeability. This could prove critical to increasing the efficiency of heat exchange for geothermal energy extraction from hot dry rock. ?? 1980.

Numerical simulation based on core analysis of a single fracture in an Enhanced Geothermal System

NASA Astrophysics Data System (ADS)

Jarrahi, Miad; Holländer, Hartmut

2017-04-01

The permeability of reservoirs is widely affected by the presence of fractures dispersed within them, as they form superior paths for fluid flow. Core analysis studies the fractures characteristics and explains the fluid-rock interactions to provide the information of permeability and saturation of a hydraulic fracturing reservoir or an enhanced geothermal system (EGS). This study conducted numerical simulations of a single fracture in a Granite core obtained from a depth of 1890 m in borehole EPS1 from Soultz-sous-Forêts, France. Blaisonneau et al. (2016) designed the apparatus to investigate the complex physical phenomena on this cylindrical sample. The method of the tests was to percolate a fluid through a natural fracture contained in a rock sample, under controlled thermo-hydro-mechanical conditions. A divergent radial flow within the fracture occurred due to the injection of fluid into the center of the fracture. The tests were performed within a containment cell with a normal stress of 2.6, 4.9, 7.2 and 9.4 MPa loading on the sample perpendicular to the fracture plane. This experiment was numerically performed to provide an efficient numerical method by modeling single phase flow in between the fracture walls. Detailed morphological features of the fracture such as tortuosity and roughness, were obtained by image processing. The results included injection pressure plots with respect to injection flow rate. Consequently, by utilizing Hagen-Poiseuille's cubic law, the equivalent hydraulic aperture size, of the fracture was derived. Then, as the sample is cylindrical, to modify the Hagen-Poiseuille's cubic law for circular parallel plates, the geometric relation was applied to obtain modified hydraulic aperture size. Finally, intrinsic permeability of the fracture under each mechanical normal stress was evaluated based on modified hydraulic aperture size. The results were presented in two different scenarios, before and after reactive percolation test, to demonstrate the effect of chemical reactive flow. The fracture after percolation test showed larger equivalent aperture size and higher permeability. Additionally, the higher the normal stress, the lower permeability was investigated. This confirmed the permeability evolution due to chemical percolation and mechanical loading. All results showed good agreements with corresponding experimental results provided by Blaisonneau et al. (2016). Keyword: Core analysis, Hydraulic fracturing, Enhanced geothermal system, Permeability, Fluid-rock interactions.

Self-Organizing Fluid Convection Patterns in an en Echelon Fault Array

NASA Astrophysics Data System (ADS)

Patterson, James W.; Driesner, Thomas; Matthai, Stephan K.

2018-05-01

We present three-dimensional numerical simulations of natural convection in buried, vertical en echelon faults in impermeable host rock. Despite the fractures being hydraulically disconnected, convection within each fracture alters the temperature field in the surrounding host rock, altering convection in neighboring fractures. This leads to self-organization of coherent patterns of upward/downward flow and heating/cooling of the host rock spanning the entire fault array. This "synchronization" effect occurs when fracture spacing is less than the width of convection cells within the fractures, which is controlled by fracture transmissivity (permeability times thickness) and heterogeneity. Narrow fracture spacing and synchronization enhance convective fluid flow within fractures and cause convection to initiate earlier, even lowering the critical transmissivity necessary for convection initiation. Heat flow through the en echelon region, however, is enhanced only in low-transmissivity fractures, while heat flow in high-permeability fractures is reduced due to thermal interference between fractures.

Impact of Stress on Anomalous Transport in Fractured Rock

NASA Astrophysics Data System (ADS)

Kang, P. K.; Lei, Q.; Lee, S.; Dentz, M.; Juanes, R.

2016-12-01

Fluid flow and transport in fractured rock controls many natural and engineered processes in the subsurface. However, characterizing flow and transport through fractured media is challenging due to the large heterogeneity of fractured rock properties. In addition to these "static" challenges, geologic fractures are always under significant overburden stress, and changes in the stress state can lead to changes in the fracture's ability to conduct fluids. While confining stress has been shown to impact fluid flow through fractures in a fundamental way, the impact of confining stress on transport through fractured rock remains largely unexplored. The link between anomalous (non-Fickian) transport and confining stress has been shown only recently, at the level of a single rough fracture [1]. Here, we investigate the impact of confining stress on flow and transport through discrete fracture networks. We model geomechanical effects in 2D fractured rock by means of a finite-discrete element method (FEMDEM), which can capture the deformation of matrix blocks, reactivation and propagation of cracks. We implement a joint constitutive model within the FEMDEM framework to simulate the effect of fracture roughness. We apply the model to a fracture network extracted from the geological map of an actual outcrop to obtain the aperture field at different stress conditions (Figure 1). We then simulate fluid flow and particle transport through the stressed fracture networks. We observe that anomalous transport emerges in response to confining stress on the fracture networks, and show that this anomalous behavior can be linked to the stress state of the rock. Finally, we develop an effective transport model that captures the anomalous transport through stressed fractures. Our results point to a heretofore unrecognized link between geomechanics and anomalous transport in discrete fractured networks. [1] P. K. Kang, S. Brown, and R. Juanes, Emergence of anomalous transport in stressed rough fractures. Earth and Planetary Science Letters, to appear (2016). Figure (a) Map of maximum principal stress with a vertical normal compressive stress of 3 MPa at top and bottom boundaries, and 1MPa at left and right boundaries. (b) Normal compressive stress of 15 MPa at top and bottom boundaries, and 5MPa at left and right boundaries.

Domain growth kinetics in stratifying foam films

NASA Astrophysics Data System (ADS)

Zhang, Yiran; Sharma, Vivek

2015-11-01

Baking bread, brewing cappuccino, pouring beer, washing dishes, shaving, shampooing, whipping eggs and blowing bubbles all involve creation of aqueous foam films. Typical foam films consist of two surfactant-laden surfaces that are ~ 5 nm - 10 micron apart. Sandwiched between these interfacial layers is a fluid that drains primarily under the influence of viscous and interfacial forces, including disjoining pressure. Interestingly, a layered ordering of micelles inside the foam films (thickness <100 nm) leads to a stepwise thinning phenomena called stratification, which results in a thickness-dependent variation in reflected light intensity, visualized as progressively darker shades of gray. Thinner, darker domains spontaneously grow within foam films. We show that the domain expansion dynamics exhibit two distinct growth regimes with characteristic scaling laws. Though several studies have focused on the expansion dynamics of isolated domains that exhibit a diffusion-like scaling, the change in expansion kinetics observed after domains contact with the Plateau border has not been reported and analyzed before.

The Effect of Boiling on Seismic Properties of Water-Saturated Fractured Rock

NASA Astrophysics Data System (ADS)

Grab, Melchior; Quintal, Beatriz; Caspari, Eva; Deuber, Claudia; Maurer, Hansruedi; Greenhalgh, Stewart

2017-11-01

Seismic campaigns for exploring geothermal systems aim at detecting permeable formations in the subsurface and evaluating the energy state of the pore fluids. High-enthalpy geothermal resources are known to contain fluids ranging from liquid water up to liquid-vapor mixtures in regions where boiling occurs and, ultimately, to vapor-dominated fluids, for instance, if hot parts of the reservoir get depressurized during production. In this study, we implement the properties of single- and two-phase fluids into a numerical poroelastic model to compute frequency-dependent seismic velocities and attenuation factors of a fractured rock as a function of fluid state. Fluid properties are computed while considering that thermodynamic interaction between the fluid phases takes place. This leads to frequency-dependent fluid properties and fluid internal attenuation. As shown in a first example, if the fluid contains very small amounts of vapor, fluid internal attenuation is of similar magnitude as attenuation in fractured rock due to other mechanisms. In a second example, seismic properties of a fractured geothermal reservoir with spatially varying fluid properties are calculated. Using the resulting seismic properties as an input model, the seismic response of the reservoir is then computed while the hydrothermal structure is assumed to vary over time. The resulting seismograms demonstrate that anomalies in the seismic response due to fluid state variability are small compared to variations caused by geological background heterogeneity. However, the hydrothermal structure in the reservoir can be delineated from amplitude anomalies when the variations due to geology can be ruled out such as in time-lapse experiments.

The Iceland Deep Drilling Project (IDDP): Deep Fluid Sampling in Fractured Quartz, Reykjanes Geothermal System, Iceland

NASA Astrophysics Data System (ADS)

Seward, R. J.; Reed, M. H.; Grist, H. R.; Fridriksson, T.; Danielsen, P.; Thorhallsson, S.; Elders, W. A.; Fridleifsson, G. O.

2011-12-01

In July of 2011 a fluid inclusion tool (FIT) was deployed in well RN-17b of the Reykjanes geothermal system, Iceland, with the goal of sampling fluids in situ at the deepest feed point in the well. The tool consists of a perforated stainless steel pipe containing eight stainless steel mesh canisters, each loaded with 10mm-scale blocks of thermally fractured quartz. Except for one control canister, in each canister the fractured quartz blocks were surrounded by a different grain size of SiO¬2 glass that ranged in size from 10μm-scale glass wool to cm-scale glass shards. The FIT was left in the well on a wireline at a depth of 2768m and retrieved after three weeks. The fluid at 2768m depth is known from November 2010 well logs to have a temperature of about 330°C and pressure of 170 bars, a pressure ~40 bar too high for boiling at that temperature. After retrieval, quartz in all of the canisters contained liquid-dominated fluid inclusions, but their quantity and size differed by canister. Groups of inclusions occur in healed fractures and both healed and open fracture surfaces are visible within single quartz blocks. Measurements on a heating and cooling stage yield approximant inclusion homogenization temperatures of 332°C and freezing points of -2.0°C. These measurements and a pressure of 170 bars yield trapping temperatures of 335°C and a NaCl weight percent of 3.4, both of which match known values, thus verifying that the device trapped fluids as intended. In upcoming studies, these fluids will be analyzed using bulk methods and LA-ICP-MS on individual inclusions. The glass added to the quartz blocks in the canisters allowed the Reykjanes fluids to precipitate enough quartz to heal fractures and trap fluids despite the fluid undersaturation in quartz. Almost all of the glass that was added to the canisters, 27 to 66 grams in each (except glass wool), was consumed in the experiment. Remaining glass was in the non-mesh bottom caps of the canisters where fluid flux may have been minimal, indicating that most of the dissolved SiO2 was carried away with flowing fluid. This may explain why not all fractures were healed, as they were in our previous closed-system laboratory experiments. Upon recovery from the well, the FIT and the canister contents were covered in fine black particles, the greatest quantity by far occurring in canisters that had contained glass wool as the SiO2 source. Preliminary SEM-EDS analyses show that the particles contain silica, iron, magnesium, and small amounts of zinc sulfide. The precipitation of sulfides from the fluid sampled in the quartz fractures provides a valuable constraint on interpretation of the fluid inclusion compositions.

Experimental analysis of multiple factors on hydraulic fracturing in coalbed methane reservoirs

PubMed Central

Ma, Geng; Liu, Xiao; Tao, Yunqi; Feng, Dan; Li, Rui

2018-01-01

Hydraulic fracturing can improve the permeability of coalbed methane (CBM) reservoirs effectively, which is of great significance to the commercial production of CBM. However, the efficiency of hydraulic fracturing is affected by multiple factors. The mechanism of fracture initiation, morphology and propagation in CBM reservoirs is not clear and need to be further explored. Hydraulic fracturing experiment is an accurate tool to explore these mechanisms. The quantity of experimental coal rock is large and processing method is complex, so specimen made of similar materials was applied to replace coal rock. The true triaxial hydraulic fracturing experimental apparatus, 3D scanning device for coal rock section were applied to carry out hydraulic fracturing experiment. The results show that the initiation pressure is inversely proportional to the horizontal stress difference (Δσ) and positively related to fracturing fluid injection rate. When vertical stress (σv) is constant, the initiation pressure and fracture width decrease with the increasing of Δσ. Natural fractures can be connected by main fracture when propagates perpendicular to the direction of minimum horizontal stress (σh), then secondary fractures and fracture network form in CBM reservoirs. When two stresses of crustal stress are close and far different from the third one, the fracture morphology and propagation become complex. Influenced by perforations and filtration of fracturing fluid in specimen, fracturing fluid flows to downward easily after comparing horizontal well fracturing with vertical well fracturing. Fracture width increases with the decreasing of elastic modulus, the intensity of fracture is positively related with the elastic modulus of coal rock. The research results can provide theoretical basis and technical support for the efficient development of CBM. PMID:29621295

Experimental analysis of multiple factors on hydraulic fracturing in coalbed methane reservoirs.

PubMed

Zhang, Fan; Ma, Geng; Liu, Xiao; Tao, Yunqi; Feng, Dan; Li, Rui

2018-01-01

Hydraulic fracturing can improve the permeability of coalbed methane (CBM) reservoirs effectively, which is of great significance to the commercial production of CBM. However, the efficiency of hydraulic fracturing is affected by multiple factors. The mechanism of fracture initiation, morphology and propagation in CBM reservoirs is not clear and need to be further explored. Hydraulic fracturing experiment is an accurate tool to explore these mechanisms. The quantity of experimental coal rock is large and processing method is complex, so specimen made of similar materials was applied to replace coal rock. The true triaxial hydraulic fracturing experimental apparatus, 3D scanning device for coal rock section were applied to carry out hydraulic fracturing experiment. The results show that the initiation pressure is inversely proportional to the horizontal stress difference (Δσ) and positively related to fracturing fluid injection rate. When vertical stress (σv) is constant, the initiation pressure and fracture width decrease with the increasing of Δσ. Natural fractures can be connected by main fracture when propagates perpendicular to the direction of minimum horizontal stress (σh), then secondary fractures and fracture network form in CBM reservoirs. When two stresses of crustal stress are close and far different from the third one, the fracture morphology and propagation become complex. Influenced by perforations and filtration of fracturing fluid in specimen, fracturing fluid flows to downward easily after comparing horizontal well fracturing with vertical well fracturing. Fracture width increases with the decreasing of elastic modulus, the intensity of fracture is positively related with the elastic modulus of coal rock. The research results can provide theoretical basis and technical support for the efficient development of CBM.

Trends in hydraulic fracturing distributions and treatment fluids, additives, proppants, and water volumes applied to wells drilled in the United States from 1947 through 2010: data analysis and comparison to the literature

USGS Publications Warehouse

Gallegos, Tanya J.; Varela, Brian A.

2015-01-01

Hydraulic fracturing is presently the primary stimulation technique for oil and gas production in low-permeability, unconventional reservoirs. Comprehensive, published, and publicly available information regarding the extent, location, and character of hydraulic fracturing in the United States is scarce. This national spatial and temporal analysis of data on nearly 1 million hydraulically fractured wells and 1.8 million fracturing treatment records from 1947 through 2010 (aggregated in Data Series 868) is used to identify hydraulic fracturing trends in drilling methods and use of proppants, treatment fluids, additives, and water in the United States. These trends are compared to the literature in an effort to establish a common understanding of the differences in drilling methods, treatment fluids, and chemical additives and of how the newer technology has affected the water use volumes and areal distribution of hydraulic fracturing. Historically, Texas has had the highest number of records of hydraulic fracturing treatments and associated wells in the United States documented in the datasets described herein. Water-intensive horizontal/directional drilling has also increased from 6 percent of new hydraulically fractured wells drilled in the United States in 2000 to 42 percent of new wells drilled in 2010. Increases in horizontal drilling also coincided with the emergence of water-based “slick water” fracturing fluids. As such, the most current hydraulic fracturing materials and methods are notably different from those used in previous decades and have contributed to the development of previously inaccessible unconventional oil and gas production target areas, namely in shale and tight-sand reservoirs. Publicly available derivative datasets and locations developed from these analyses are described.

Numerical Simulation of Dispersion from Urban Greenhouse Gas Sources

NASA Astrophysics Data System (ADS)

Nottrott, Anders; Tan, Sze; He, Yonggang; Winkler, Renato

2017-04-01

Cities are characterized by complex topography, inhomogeneous turbulence, and variable pollutant source distributions. These features create a scale separation between local sources and urban scale emissions estimates known as the Grey-Zone. Modern computational fluid dynamics (CFD) techniques provide a quasi-deterministic, physically based toolset to bridge the scale separation gap between source level dynamics, local measurements, and urban scale emissions inventories. CFD has the capability to represent complex building topography and capture detailed 3D turbulence fields in the urban boundary layer. This presentation discusses the application of OpenFOAM to urban CFD simulations of natural gas leaks in cities. OpenFOAM is an open source software for advanced numerical simulation of engineering and environmental fluid flows. When combined with free or low cost computer aided drawing and GIS, OpenFOAM generates a detailed, 3D representation of urban wind fields. OpenFOAM was applied to model scalar emissions from various components of the natural gas distribution system, to study the impact of urban meteorology on mobile greenhouse gas measurements. The numerical experiments demonstrate that CH4 concentration profiles are highly sensitive to the relative location of emission sources and buildings. Sources separated by distances of 5-10 meters showed significant differences in vertical dispersion of plumes, due to building wake effects. The OpenFOAM flow fields were combined with an inverse, stochastic dispersion model to quantify and visualize the sensitivity of point sensors to upwind sources in various built environments. The Boussinesq approximation was applied to investigate the effects of canopy layer temperature gradients and convection on sensor footprints.

Monitoring Fluid Flow in Fractured Carbonate Rocks Using Seismic Measurements

NASA Astrophysics Data System (ADS)

Li, W.; Pyrak-Nolte, L. J.

2008-12-01

The physical properties of carbonate rock are strongly influenced by the rock fabric which depends on the depositional environment, diagenetic and tectonic processes. The most common form of heterogeneity is layering caused by a variation in porosity among layers and within layers. The variation in porosity among layers leads to anisotropic behavior in the hydraulic, mechanical and seismic properties of carbonate rocks. We present the results of a laboratory study to examine the effect of fabric-controlled layering on fluid flow and seismic wave propagation through intact and fractured carbonate rock. Experiments were performed on cubic samples of Austin Chalk Cordova Cream. Samples AC1, AC5 and AC6 are cubic samples that measure 100 mm on edge. The samples were sealed and contained three inlet and three outlet ports for fluid invasion experiments. Two orthogonal seismic arrays were used to record both compressional and shear wave transmission through intact and fractured samples. The arrays used piezoelectric contact transducers with a central frequency 1.0 MHz. Between the two arrays, sixteen sources and sixteen receivers were used. Seismic measurements were made on the samples as a function of stress and during fluid saturation. The location of the invading fluid front as a function of time was monitored by using the peak-to-peak amplitude of the transmitted signals. The front was assumed to be between a source-receiver pair when the signal amplitude decreased by 50% over the initial value. The hydraulic gradient was parallel and perpendicular to the layers for AC5 and AC6, respectively. Sample AC1 was fractured and flow ports were established on the edges of the fracture plane. The weakly directed fabric controlled the rate at which fluid flowed through the samples. From the seismic data on AC6, the fluid first spread vertically along a layer before flowing across the layers. For AC6, it took the fluid two and half hours to flow between the inlet and the outlet across the layers. However, for AC5, the water flowed quickly along the layers and crossed the entire sample in one and a half hours. From the seismic data on fractured sample AC1, the water initially took more than 15 hours to transverse the sample though portions of the fracture were invaded after two hours. No water was produced at the outlet over a 15 hour period. Upon inspection, chemical precipitation was observed along the fracture plane and fracture- matrix interaction controlled the saturation of the matrix. Seismic monitoring of the fluid-front during saturation indicates that fine bedding affects the hydraulic properties of the sample while geochemical interactions in fractures affect fracture-matrix communication. Acknowledgments: The authors wish to acknowledge support of this work by the Geosciences Research Program, Office of Basic Energy Sciences US Department of Energy (DEFG02-97ER14785 08) and by Exxon Mobil Upstream Research Company.

The Impact of Mineralogy on the Geochemical Alteration of Shales During Hydraulic Fracturing Operations

NASA Astrophysics Data System (ADS)

Maher, K.; Harrison, A. L.; Jew, A. D.; Dustin, M. K.; Kiss, A. M.; Kohli, A. H.; Thomas, D.; Joe-Wong, C. M.; Brown, G. E.; Bargar, J.

2016-12-01

The extraction of oil and gas resources from low permeability shale reservoirs using hydraulic fracturing techniques has increased significantly in recent years. During hydraulic fracturing, large volumes of fluid are injected into subsurface shale formations, which drives substantial fluid-rock interaction that can release contaminants and alter rock permeability. Here, a combined experimental, imaging, and modeling approach was employed to systematically evaluate the impact of shale mineralogy on its physical and chemical alteration when exposed to fracturing fluids of different composition. Batch reactor experiments contained different shales with unique mineralogical compositions that were exposed to simulated hydraulic fracturing fluid. Experiments revealed that the balance between fluid acidity and acid neutralizing capacity of the rock was the strongest control on the evolution of fluid and rock chemistry. Carbonate mineral-rich shales rapidly recovered solution pH to circum-neutral conditions, whereas fluids in contact with carbonate mineral-poor shales remained acidic. The dissolution of shale minerals released metal contaminants, yet the precipitation of Fe(III)-bearing secondary phases helped to attenuate their release via co-precipitation or sorption. Post-reaction imaging illustrated that selective dissolution of carbonate minerals generated secondary porosity, the connectivity of which was dictated by initial carbonate distribution. Conversely, the precipitation of secondary Al- and Fe-bearing phases may occlude porosity, potentially inhibiting transport of water, contaminants, and hydrocarbons. The maturation of secondary Fe-bearing phases from amorphous to crystalline over time suggests that porosity will continue to evolve even after oxidation reactions have effectively ceased. These experiments reveal that the relative abundance and distribution of carbonate minerals is the master variable dictating both porosity alteration and contaminant release from shale formations, implying that the response of a reservoir to hydraulic fracturing can be better assessed using robust mineralogical data.

Influence of Concentration and Salinity on the Biodegradability of Organic Additives in Hydraulic Fracturing Fluid

NASA Astrophysics Data System (ADS)

Mouser, P. J.; Kekacs, D.

2014-12-01

One of the risks associated with the use of hydraulic fracturing technologies for energy development is the potential release of hydraulic fracturing-related fluids into surface waters or shallow aquifers. Many of the organic additives used in hydraulic fracturing fluids are individually biodegradable, but little is know on how they will attenuate within a complex organic fluid in the natural environment. We developed a synthetic hydraulic fracturing fluid based on disclosed recipes used by Marcellus shale operators to evaluate the biodegradation potential of organic additives across a concentration (25 to 200 mg/L DOC) and salinity gradient (0 to 60 g/L) similar to Marcellus shale injected fluids. In aerobic aqueous solutions, microorganisms removed 91% of bulk DOC from low SFF solutions and 57% DOC in solutions having field-used SFF concentrations within 7 days. Under high SFF concentrations, salinity in excess of 20 g/L inhibited organic compound biodegradation for several weeks, after which time the majority (57% to 75%) of DOC remained in solution. After SFF amendment, the initially biodiverse lake or sludge microbial communities were quickly dominated (>79%) by Pseudomonas spp. Approximately 20% of added carbon was converted to biomass while the remainder was respired to CO2 or other metabolites. Two alcohols, isopropanol and octanol, together accounted for 2-4% of the initial DOC, with both compounds decreasing to below detection limits within 7 days. Alcohol degradation was associated with an increase in acetone at mg/L concentrations. These data help to constrain the biodegradation potential of organic additives in hydraulic fracturing fluids and guide our understanding of the microbial communities that may contribute to attenuation in surface waters.

Low stiffness floors can attenuate fall-related femoral impact forces by up to 50% without substantially impairing balance in older women.

PubMed

Laing, Andrew C; Robinovitch, Stephen N

2009-05-01

Low stiffness floors such as carpet appear to decrease hip fracture risk by providing a modest degree of force attenuation during falls without impairing balance. It is unknown whether other compliant floors can more effectively reduce impact loads without coincident increases in fall risk. We used a hip impact simulator to assess femoral neck force for four energy-absorbing floors (SmartCell, SofTile, Firm Foam, Soft Foam) compared to a rigid floor. We also assessed the influence of these floors on balance/mobility in 15 elderly women. We observed differences in the mean attenuation in peak femoral neck force provided by the SmartCell (24.5%), SofTile (47.2%), Firm Foam (76.6%), and Soft Foam (52.4%) floors. As impact velocity increased from 2 to 4m/s, force attenuation increased for SmartCell (from 17.3% to 33.7%) and SofTile (from 44.9% to 51.2%), but decreased for the Firm Foam (from 87.0% to 64.5%) and Soft Foam (from 66.1% to 37.9%) conditions. Regarding balance, there were no significant differences between the rigid, SmartCell, and SofTile floors in proportion of successful trials, Get Up and Go time, balance confidence or utility ratings. SofTile, Firm Foam, and Soft Foam caused significant increases (when compared to the rigid floor) in postural sway in the anterior-posterior and medial-lateral directions during standing. However, SmartCell increased sway only in the anterior-posterior direction. This study demonstrates that two commercially available compliant floors can attenuate femoral impact force by up to 50% while having only limited influence on balance in older women, and supports development of clinical trials to test their effectiveness in high-risk settings.

Fracture development within a stratovolcano: The Karaha-Telaga Bodas geothermal field, Java volcanic arc

USGS Publications Warehouse

Nemcok, M.; Moore, J.N.; Allis, R.; McCulloch, J.

2004-01-01

Karaha-Telaga Bodas, a vapour-dominated geothermal system located in an active volcano in western Java, is penetrated by more than two dozen deep geothermal wells reaching depths of 3 km. Detailed paragenetic and fluid-inclusion studies from over 1000 natural fractures define the liquid-dominated, transitional and vapour-dominated stages in the evolution of this system. The liquid-dominated stage was initiated by ashallow magma intrusion into the base of the volcanic cone. Lava and pyroclastic flows capped a geothermal system. The uppermost andesite flows were only weakly fractured due to the insulating effect of the intervening altered pyroclastics, which absorbed the deformation. Shear and tensile fractures that developed were filled with carbonates at shallow depths, and by quartz, epidote and actinolite at depths and temperatures over 1 km and 300??C. The system underwent numerous cycles of overpressuring, documented by subhorizontal tensile fractures, anastomosing tensile fracture patterns and implosion breccias. The development of the liquidsystem was interrupted by a catastrophic drop in fluid pressures. As the fluids boiled in response to this pressure drop, chalcedony and quartz were selectively deposited in fractures that had the largest apertures and steep dips. The orientations of these fractures indicate that the escaping overpressured fluids used the shortest possible paths to the surface. Vapour-dominated conditions were initiated at this time within a vertical chimney overlying the still hot intrusion. As pressures declined, these conditions spread outward to form the marginal vapour-dominated region encountered in the drill holes. Downward migration of the chimney, accompanied by growth of the marginal vapour-dominated regime, occurred as the intrusion cooled and the brittle-ductile transition migrated to greater depths. As the liquids boiled off, condensate that formed at the top of the vapour-dominated zone percolated downward and low-salinity meteoric water entered the marginal parts of the system. Calcite, anhydrite and fluorite precipitated in fractures on heating. Progressive sealing of the fractures resulted in the downward migration of the cap rock. In response to decreased pore pressure in the expanding vapour zone, walls of the fracture system within the vapour-dominated reservoir progressively collapsed. It left only residual permeability in the remaining fracture volume, with apertures supported only by asperities or propping breccia. In places where normal stresses acting on the fracture walls exceeded the compressive strength of the wall rock, the fractures have completely collapsed. Fractures within the present-day cap rock include strike- and oblique-slip faults, normal faults and tensile fractures, all controlled by a strike-slip stress regime. The reservoir is characterized by normal faults and tensile fractures controlled by a normal-fault stress regime. The fractures show no evidence that the orientation of the stress field has changed since fracture propagation began. Fluid migration in the lava and pyroclastic flows is controlled by fractures. Matrix permeability controls fluid flow in the sedimentary sections of the reservoir. Productive fractures are typically roughly perpendicular to the minimum compressive stress, ??3, and are prone to slip and dilation within the modern stress regime. ?? The Geological Society of London 2004.

Fluid inclusions in calcite filled opening fractures of the Serra Alta Formation reveal paleotemperatures and composition of diagenetic fluids percolating Permian shales of the Paraná Basin

NASA Astrophysics Data System (ADS)

Teixeira, C. A. S.; Sawakuchi, A. O.; Bello, R. M. S.; Nomura, S. F.; Bertassoli, D. J.; Chamani, M. A. C.

2018-07-01

The thermal and diagenetic evolution of shale units has received renewed focus because of their emergence as unconventional hydrocarbon reservoirs. The Serra Alta Formation (SAF) is a Permian shale unit of the Paraná Basin, which is the largest South American cratonic basin. The SAF stands out as a pathway for aqueous fluids and hydrocarbon migration from the Irati organic-rich shales to the Pirambóia fluvial-eolian sandstone reservoirs. Vertical NNW and NNE opening fractures would be the main pathways for the migration of buried pore waters and aqueous fluids, besides the input of meteoric water. These fractures would be associated to the reactivation of basement discontinuities such as the Jacutinga (NE) and Guapiara (NW) faults. Thus, vertical NNE and NNW associated fractures would represent the main pathways for fluid migration in the studied area. The vertical calcite filled opening fractures from SAF record moderately low salinity (0-4.5 wt % of NaCl eq.) aqueous fluids, suggesting the input of meteoric water in the buried fracture system. Eutectic melting temperatures at -52±5 °C indicate an H2O + NaCl + CaCl2 system with CaCl2 or MgCl2 in solution. Homogenization temperatures recorded in fluid inclusion assemblages (FIAs) of calcite filled opening fractures indicate that the SAF in the studied area reached temperatures above 200 °C, suitable for generation of gaseous hydrocarbons. The recorded paleotemperatures point to a thermal peak associated with Serra Geral volcanic event during the Early Cretaceous, with the thermal effect of volcanic rock cap possibly overcoming the effect of intrusive igneous bodies. The detection of methane in SAF shale pores indicates conditions for hydrocarbon generation. However, additionally studies are necessary to confirm the thermogenic and/or biogenic origin of the methane within the SAF.

Comparison of Two-Phase Pipe Flow in OpenFOAM with a Mechanistic Model

NASA Astrophysics Data System (ADS)

Shuard, Adrian M.; Mahmud, Hisham B.; King, Andrew J.

2016-03-01

Two-phase pipe flow is a common occurrence in many industrial applications such as power generation and oil and gas transportation. Accurate prediction of liquid holdup and pressure drop is of vast importance to ensure effective design and operation of fluid transport systems. In this paper, a Computational Fluid Dynamics (CFD) study of a two-phase flow of air and water is performed using OpenFOAM. The two-phase solver, interFoam is used to identify flow patterns and generate values of liquid holdup and pressure drop, which are compared to results obtained from a two-phase mechanistic model developed by Petalas and Aziz (2002). A total of 60 simulations have been performed at three separate pipe inclinations of 0°, +10° and -10° respectively. A three dimensional, 0.052m diameter pipe of 4m length is used with the Shear Stress Transport (SST) k - ɷ turbulence model to solve the turbulent mixtures of air and water. Results show that the flow pattern behaviour and numerical values of liquid holdup and pressure drop compare reasonably well to the mechanistic model.

Noise reducing screen devices for in-flow pressure sensors

NASA Technical Reports Server (NTRS)

Schmitz, Fredric (Inventor); Liu, Sandy (Inventor); Jaeger, Stephen (Inventor); Horne, W. Clifton (Inventor)

1997-01-01

An acoustic sensor assembly is provided for sensing acoustic signals in a moving fluid such as high speed fluid stream. The assembly includes one or more acoustic sensors and a porous, acoustically transparent screen supported between the moving fluid stream and the sensor and having a major surface disposed so as to be tangent to the moving fluid. A layer of reduced velocity fluid separating the sensor from the porous screen. This reduced velocity fluid can comprise substantially still air. A foam filler material attenuates acoustic signals arriving at the assembly from other than a predetermined range of incident angles.

Capillary Imbibition of Hydraulic Fracturing Fluids into Partially Saturated Shale

NASA Astrophysics Data System (ADS)

Birdsell, D.; Rajaram, H.; Lackey, G.

2015-12-01

Understanding the migration of hydraulic fracturing fluids injected into unconventional reservoirs is important to assess the risk of aquifer contamination and to optimize oil and gas production. Capillary imbibition causes fracturing fluids to flow from fractures into the rock matrix where the fluids are sequestered for geologically long periods of time. Imbibition could explain the low amount of flowback water observed in the field (5-50% of the injected volume) and reduce the chance of fracturing fluid migrating out of formation towards overlying aquifers. We present calculations of spontaneous capillary imbibition in the form of an "imbibition rate parameter" (A) based on the only known exact analytical solution for spontaneous capillary imbibition. A depends on the hydraulic and capillary properties of the reservoir rock, the initial water saturation, and the viscosities of the wetting and nonwetting fluids. Imbibed volumes can be large for a high permeability shale gas reservoir (up to 95% of the injected volume) or quite small for a low permeability shale oil reservoir (as low as 3% of the injected volume). We also present a nondimensionalization of the imbibition rate parameter, which facilitates the calculation of A and clarifies the relation of A to initial saturation, porous medium properties, and fluid properties. Over the range of initial water saturations reported for the Marcellus shale (0.05-0.6), A varies by less than factors of ~1.8 and ~3.4 for gas and oil nonwetting phases respectively. However, A decreases significantly for larger initial water saturations. A is most sensitive to the intrinsic permeability of the reservoir rock and the viscosity of the fluids.

Impact of eliminating fracture intersection nodes in multiphase compositional flow simulation

NASA Astrophysics Data System (ADS)

Walton, Kenneth M.; Unger, Andre J. A.; Ioannidis, Marios A.; Parker, Beth L.

2017-04-01

Algebraic elimination of nodes at discrete fracture intersections via the star-delta technique has proven to be a valuable tool for making multiphase numerical simulations more tractable and efficient. This study examines the assumptions of the star-delta technique and exposes its effects in a 3-D, multiphase context for advective and dispersive/diffusive fluxes. Key issues of relative permeability-saturation-capillary pressure (kr-S-Pc) and capillary barriers at fracture-fracture intersections are discussed. This study uses a multiphase compositional, finite difference numerical model in discrete fracture network (DFN) and discrete fracture-matrix (DFM) modes. It verifies that the numerical model replicates analytical solutions and performs adequately in convergence exercises (conservative and decaying tracer, one and two-phase flow, DFM and DFN domains). The study culminates in simulations of a two-phase laboratory experiment in which a fluid invades a simple fracture intersection. The experiment and simulations evoke different invading fluid flow paths by varying fracture apertures as oil invades water-filled fractures and as water invades air-filled fractures. Results indicate that the node elimination technique as implemented in numerical model correctly reproduces the long-term flow path of the invading fluid, but that short-term temporal effects of the capillary traps and barriers arising from the intersection node are lost.

In Situ Triaxial Testing To Determine Fracture Permeability and Aperture Distribution for CO2 Sequestration in Svalbard, Norway.

PubMed

Van Stappen, Jeroen F; Meftah, Redouane; Boone, Marijn A; Bultreys, Tom; De Kock, Tim; Blykers, Benjamin K; Senger, Kim; Olaussen, Snorre; Cnudde, Veerle

2018-04-17

On Svalbard, Arctic Norway, an unconventional siliciclastic reservoir, relying on (micro)fractures for enhanced fluid flow in a low-permeable system, is investigated as a potential CO 2 sequestration site. The fractures' properties at depth are, however, poorly understood. High resolution X-ray computed tomography (micro-CT) imaging allows one to visualize such geomaterials at reservoir conditions. We investigated reservoir samples from the De Geerdalen Formation on Svalbard to understand the influence of fracture closure on the reservoir fluid flow behavior. Small rock plugs were brought to reservoir conditions, while permeability was measured through them during micro-CT imaging. Local fracture apertures were quantified down to a few micrometers wide. The permeability measurements were complemented with fracture permeability simulations based on the obtained micro-CT images. The relationship between fracture permeability and the imposed confining pressure was determined and linked to the fracture apertures. The investigated fractures closed due to the increased confining pressure, with apertures reducing to approximately 40% of their original size as the confining pressure increased from 1 to 10 MPa. This coincides with a permeability drop of more than 90%. Despite their closure, fluid flow is still controlled by the fractures at pressure conditions similar to those at the proposed storage depth of 800-1000 m.

Scale Effects in the Flow of a Shear-Thinning Fluid in Geological Fractures

NASA Astrophysics Data System (ADS)

Meheust, Y.; Roques, C.; Le Borgne, T.; Selker, J. S.

2017-12-01

Subsurface flow processes involving non-Newtonian fluids play a major role in many engineering applications, from in-situ remediation to enhanced oil recovery. The fluids of interest in such applications (f.e., polymers in remediation) often present shear-thinning properties, i.e., their viscosity decreases as a function of the local shear rate. We investigate how fracture wall roughness impacts the flow of a shear-thinning fluid. Numerical simulations of flow in 3D geological fractures are carried out by solving a modified Navier-Stokes equation incorporating the Carreau viscous-shear model. The numerical fractures consist of two isotropic self-affine surfaces which are correlated with each other above a characteristic scale (thecorrelation length of Méheust et al. PAGEOPH 2003). Perfect plastic closing is assumed when the surfaces are in contact. The statistical parameters describing a fracture are the standard deviation of the wall roughness, the mean aperture, the correlation length, and the fracture length, the Hurst exponent being fixed (equal to 0.8). The objective is to investigate how varying the correlation length impacts the flow behavior, for different degrees of closure, and how this behavior diverges from what is known for Newtonian fluids. The results from the 3D simulations are also compared to 2D simulations based on the lubrication theory, which we have developed as an extension of the Reynolds equation for Newtonian fluids. These 2D simulations run orders of magnitude faster, which allows considering a significant statistics of fractures of identical statistical parameters, and therefore draw general conclusions despite the large stochasticity of the media. We also discuss the implications of our results for solute transport by such flows. References:Méheust, Y., & Schmittbuhl, J. (2003). Scale effects related to flow in rough fractures. Pure and Applied Geophysics, 160(5-6), 1023-1050.

Anomalous Transport in Natural Fracture Networks Induced by Tectonic Stress

NASA Astrophysics Data System (ADS)

Kang, P. K.; Lei, Q.; Lee, S.; Dentz, M.; Juanes, R.

2017-12-01

Fluid flow and transport in fractured rock controls many natural and engineered processes in the subsurface. However, characterizing flow and transport through fractured media is challenging due to the high uncertainty and large heterogeneity associated with fractured rock properties. In addition to these "static" challenges, geologic fractures are always under significant overburden stress, and changes in the stress state can lead to changes in the fracture's ability to conduct fluids. While confining stress has been shown to impact fluid flow through fractures in a fundamental way, the impact of confining stress on transportthrough fractured rock remains poorly understood. The link between anomalous (non-Fickian) transport and confining stress has been shown, only recently, at the level of a single rough fracture [1]. Here, we investigate the impact of geologic (tectonic) stress on flow and tracer transport through natural fracture networks. We model geomechanical effects in 2D fractured rock by means of a finite-discrete element method (FEMDEM) [2], which can capture the deformation of matrix blocks, reactivation of pre-existing fractures, and propagation of new cracks, upon changes in the stress field. We apply the model to a fracture network extracted from the geological map of an actual rock outcrop to obtain the aperture field at different stress conditions. We then simulate fluid flow and particle transport through the stressed fracture networks. We observe that anomalous transport emerges in response to confining stress on the fracture network, and show that the stress state is a powerful determinant of transport behavior: (1) An anisotropic stress state induces preferential flow paths through shear dilation; (2) An increase in geologic stress increases aperture heterogeneity that induces late-time tailing of particle breakthrough curves. Finally, we develop an effective transport model that captures the anomalous transport through the stressed fracture network. Our results point to a heretofore unrecognized link between geomechanics and anomalous transport in natural fractured media. [1] P. K. Kang, S. Brown, and R. Juanes, Earth and Planetary Science Letters, 454, 46-54 (2016). [2] Q. Lei, J. P. Latham, and C. F. Tsang, Computers and Geotechnics, 85, 151-176 (2017).

Laboratory Simulation of Flow through Single Fractured Granite

NASA Astrophysics Data System (ADS)

Singh, K. K.; Singh, D. N.; Ranjith, P. G.

2015-05-01

Laboratory simulation on fluid flow through fractured rock is important in addressing the seepage/fluid-in-rush related problems that occur during the execution of any civil or geological engineering projects. To understand the mechanics and transport properties of fluid through a fractured rock in detail and to quantify the sources of non-linearity in the discharge and base pressure relationship, fluid flow experiments were carried out on a cylindrical sample of granite containing a `single rough walled fracture'. These experiments were performed under varied conditions of confining pressures, σ 3 (5-40 MPa), which can simulate the condition occurring about 1,000 m below in the earth crust, with elevated base pressure, b p (up to 25 MPa) and by changing fracture roughness. The details of the methodologies involved and the observations are discussed here. The obtained results indicate that most of the data in the Q verses b p plot, fall on the straight line and the flow through the single fracture in granite obeys Darcy's law or the well-known "cubic law" even at high value of b p (=4 MPa) and σ 3 (=5 MPa) combination. The Reynolds number is quite sensitive to the b p, σ 3 and fracture roughness, and there is a critical b p, beyond which transition in flow occurs from laminar to turbulent. It is believed that such studies will be quite useful in identifying the limits of applicability of well know `cubic law', which is required for precise calculation of discharge and/or aperture in any practical issues and in further improving theoretical/numerical models associated with fluid flow through a single fracture.

Characteristics and management of flowback/produced water from hydraulically fractured wells in California - findings from the California SB 4 assessment

NASA Astrophysics Data System (ADS)

Varadharajan, C.; Cooley, H.; Heberger, M. G.; Stringfellow, W. T.; Domen, J. K.; Sandelin, W.; Camarillo, M. K.; Jordan, P. D.; Reagan, M. T.; Donnelly, K.; Birkholzer, J. T.; Long, J. C. S.

2015-12-01

As part of a recent assessment of well stimulation in California, we analyzed the hazards and potential impacts of hydraulic fracturing (the primary form of well stimulation in California) on water resources, which included an analysis of the quantity and quality of flowback/produced water generated, current management and disposal practices, associated potential release mechanisms and transport pathways that can lead to contaminants being released into the environment, and practices to mitigate or avoid impacts from produced water on water resources. The wastewater returned after stimulation includes "recovered fluids" (flowback fluids collected into tanks following stimulation, but before the start of production) and "produced water" (water extracted with oil and gas during production). In contrast to hydraulic fracturing in regions with primarily gas production, the quantities of recovered fluids from hydraulically fractured wells in California are small in comparison to the fluids injected (typically <5%), and large quantities of produced water are generated. Our analysis indicates some fraction of returning fracturing fluids is likely present in produced water from wells that have been hydraulically fractured. Chemical measurements of recovered fluids show that some samples can contain high levels of some contaminants, including total carbohydrates (indicating the presence of guar, a component of fracturing fluid), total dissolved solids (TDS), trace elements and naturally occurring radioactive material (NORM). Data on produced water chemistry are more limited. In California, produced water is typically managed via pipelines and disposed or reused in many ways. A majority of produced water from hydraulically fractured wells in California is disposed in percolation pits, many of which may lie in areas with good groundwater quality. Some of the remaining produced water is injected into Class II wells; although a few of the wells are under review or have been shut down since they were injecting into aquifers. Other methods of management of produced water include reuse for irrigation and discharge into sewer systems. Each of these disposal and reuse methods presents its own unique set of concerns that need to be considered together, in designing a produced water management plan.

Effect of Discrete Fracture Network Characteristics on the Sustainability of Heat Production in Enhanced Geothermal Reservoirs

NASA Astrophysics Data System (ADS)

Riahi, A.; Damjanac, B.

2013-12-01

Viability of an enhanced or engineered geothermal reservoir is determined by the rate of produced fluid at production wells and the rate of temperature drawdown in the reservoir as well as that of the produced fluid. Meeting required targets demands sufficient permeability and flow circulation in a relatively large volume of rock mass. In-situ conditions such overall permeability of the bedrock formation, magnitude and orientation of stresses, and the characteristics of the existing Discrete Fracture Network (DFN) greatly affect sustainable heat production. Because much of the EGS resources are in formations with low permeability, different stimulation techniques are required prior to the production phase to enhance fluid circulation. Shear stimulation or hydro-shearing is the method of injecting a fluid into the reservoir with the aim of increasing the fluid pressure in the naturally fractured rock and inducing shear failure or slip events. This mechanism can enhance the system's permeability through permanent dilatational opening of the sheared fractures. Using a computational modeling approach, the correlation between heat production and DFN statistical characteristics, namely the fracture length distribution, fracture orientation, and also fracture density is studied in this paper. Numerical analyses were completed using two-dimensional distinct element code UDEC (Itasca, 2011), which represents rock masses as an assembly of interacting blocks separated by fractures. UDEC allows for simulation of fracture propagation along the predefined planes only (i.e., the trajectory of the hydraulic fracture is not part of the solution of the problem). Thus, the hydraulic fracture is assumed to be planar, aligned with the direction of the major principal stress. The pre-existing fractures were represented explicitly. They are discontinuities which deform elastically, but also can open and slip (Coulomb slip law) as a function of pressure and total stress changes. The fluid injection into the reservoir during stimulation phase was simulated using a fully coupled hydro-mechanical model. The heat production phase was simulated using a coupled thermo-hydro-mechanical model. In these simulations, both advective heat transfer by fluid flow and the conductive heat transfer within the rock blocks were modeled. The effect of temperature change on stresses and fracture aperture, and thus flow rates was considered. The response of formations with different DFN characteristics are analyzed by evaluating the production rate, produced power, and total energy extracted from the system over a period of five years. By simulating a full cycle of stimulation and production, the numerical modeling approach represents a realistic estimate of evolving permeability and evaluates how stimulation can be beneficial to the production phase. It is believed that these numerical sensitivity studies can provide valuable insight in evaluation of the potential of success of an EGS project, and can be used to better design the operational parameters in order to optimize heat production. Keywords: Numerical modeling, rock mechanics, discrete fracture network, stimulation, engineered geothermal reservoirs, heat production

Aerobic biodegradation of organic compounds in hydraulic fracturing fluids.

PubMed

Kekacs, Daniel; Drollette, Brian D; Brooker, Michael; Plata, Desiree L; Mouser, Paula J

2015-07-01

Little is known of the attenuation of chemical mixtures created for hydraulic fracturing within the natural environment. A synthetic hydraulic fracturing fluid was developed from disclosed industry formulas and produced for laboratory experiments using commercial additives in use by Marcellus shale field crews. The experiments employed an internationally accepted standard method (OECD 301A) to evaluate aerobic biodegradation potential of the fluid mixture by monitoring the removal of dissolved organic carbon (DOC) from an aqueous solution by activated sludge and lake water microbial consortia for two substrate concentrations and four salinities. Microbial degradation removed from 57 % to more than 90 % of added DOC within 6.5 days, with higher removal efficiency at more dilute concentrations and little difference in overall removal extent between sludge and lake microbe treatments. The alcohols isopropanol and octanol were degraded to levels below detection limits while the solvent acetone accumulated in biological treatments through time. Salinity concentrations of 40 g/L or more completely inhibited degradation during the first 6.5 days of incubation with the synthetic hydraulic fracturing fluid even though communities were pre-acclimated to salt. Initially diverse microbial communities became dominated by 16S rRNA sequences affiliated with Pseudomonas and other Pseudomonadaceae after incubation with the synthetic fracturing fluid, taxa which may be involved in acetone production. These data expand our understanding of constraints on the biodegradation potential of organic compounds in hydraulic fracturing fluids under aerobic conditions in the event that they are accidentally released to surface waters and shallow soils.

Foam flotation as a separation process

NASA Technical Reports Server (NTRS)

Currin, B. L.

1986-01-01

The basic principles of foam separation techniques are discussed. A review of the research concerning bubble-particle interaction and its role in the kinetics of the flotation process is given. Most of the research in this area deals with the use of theoretical models to predict the effects of bubble and particle sizes, of liquid flow, and of various forces on the aperture and retention of particles by bubbles. A discussion of fluid mechanical aspects of particle flotation is given.

Use of the high-resolution satellite images for detection of fractures related to the ore deposits

NASA Astrophysics Data System (ADS)

Cruz-Mondaca, M.; Soto-Pinto, C. A.; Arellano-Baeza, A. A.

2012-12-01

The Aster and GeoEye satellite high-resolution images were used to detect the structures related to the fracturing of the upper crust in the North of Chile. In particular, lineament analysis has been applied to detect the presence of epithermal fluids of low sulfurization associated with the Paleozoic ore deposits. These results have been compared with the location of the minerals altered by the presence of geothermal fluids detected using the spectral libraries. Later, the presence of fractures has been corroborated during recognition of fractures in situ and the geochemical analysis of samples of minerals altered by the presence of fluids. It was shown that the results obtained are relevant for the gold vein detection.

Evolution of fracture and fault-controlled fluid pathways in carbonates of the Albanides fold-thrust belt

USGS Publications Warehouse

Graham, Wall B.R.; Girbacea, R.; Mesonjesi, A.; Aydin, A.

2006-01-01

The process of fracture and fault formation in carbonates of the Albanides fold-thrust belt has been systematically documented using hierarchical development of structural elements from hand sample, outcrop, and geologic-map scales. The function of fractures and faults in fluid migration was elucidated using calcite cement and bitumen in these structures as a paleoflow indicator. Two prefolding pressure-solution and vein assemblages were identified: an overburden assemblage and a remote tectonic stress assemblage. Sheared layer-parallel pressure-solution surfaces of the overburden assemblage define mechanical layers. Shearing of mechanical layers associated with folding resulted in the formation of a series of folding assemblage fractures at different orientations, depending on the slip direction of individual mechanical layers. Prefolding- and folding-related fracture assemblages together formed fragmentation zones in mechanical layers and are the sites of incipient fault localization. Further deformation along these sites was accommodated by rotation and translation of fragmented rock, which formed breccia and facilitated fault offset across multiple mechanical layers. Strike-slip faults formed by this process are organized in two sets in an apparent conjugate pattern. Calcite cement and bitumen that accumulated along fractures and faults are evidence of localized fluid flow along fault zones. By systematic identification of fractures and faults, their evolution, and their fluid and bitumen contents, along with subsurface core and well-log data, we identify northeast-southwest-trending strike-slip faults and the associated structures as dominant fluid pathways in the Albanides fold-thrust belt. Copyright ?? 2006. The American Association of Petroleum Geologists. All rights reserved.

Gravity-Driven Hydraulic Fractures

NASA Astrophysics Data System (ADS)

Germanovich, L. N.; Garagash, D.; Murdoch, L. C.; Robinowitz, M.

2014-12-01

This study is motived by a new method for disposing of nuclear waste by injecting it as a dense slurry into a hydraulic fracture that grows downward to great enough depth to permanently isolate the waste. Disposing of nuclear waste using gravity-driven hydraulic fractures is mechanically similar to the upward growth of dikes filled with low density magma. A fundamental question in both applications is how the injected fluid controls the propagation dynamics and fracture geometry (depth and breadth) in three dimensions. Analog experiments in gelatin [e.g., Heimpel and Olson, 1994; Taisne and Tait, 2009] show that fracture breadth (the short horizontal dimension) remains nearly stationary when the process in the fracture "head" (where breadth is controlled) is dominated by solid toughness, whereas viscous fluid dissipation is dominant in the fracture tail. We model propagation of the resulting gravity-driven (buoyant or sinking), finger-like fracture of stationary breadth with slowly varying opening along the crack length. The elastic response to fluid loading in a horizontal cross-section is local and can be treated similar to the classical Perkins-Kern-Nordgren (PKN) model of hydraulic fracturing. The propagation condition for a finger-like crack is based on balancing the global energy release rate due to a unit crack extension with the rock fracture toughness. It allows us to relate the net fluid pressure at the tip to the fracture breadth and rock toughness. Unlike the PKN fracture, where breadth is known a priori, the final breadth of a finger-like fracture is a result of processes in the fracture head. Because the head is much more open than the tail, viscous pressure drop in the head can be neglected leading to a 3D analog of Weertman's hydrostatic pulse. This requires relaxing the local elasticity assumption of the PKN model in the fracture head. As a result, we resolve the breadth, and then match the viscosity-dominated tail with the 3-D, toughness-dominated head to obtain a complete closed-form solution. We then analyze the gravity fracture propagation in conditions of either continuous injection or finite volume release for sets of parameters representative of dense waste injection technique and low viscosity magma diking.

Fully coupled simulation of multiple hydraulic fractures to propagate simultaneously from a perforated horizontal wellbore

NASA Astrophysics Data System (ADS)

Zeng, Qinglei; Liu, Zhanli; Wang, Tao; Gao, Yue; Zhuang, Zhuo

2018-02-01

In hydraulic fracturing process in shale rock, multiple fractures perpendicular to a horizontal wellbore are usually driven to propagate simultaneously by the pumping operation. In this paper, a numerical method is developed for the propagation of multiple hydraulic fractures (HFs) by fully coupling the deformation and fracturing of solid formation, fluid flow in fractures, fluid partitioning through a horizontal wellbore and perforation entry loss effect. The extended finite element method (XFEM) is adopted to model arbitrary growth of the fractures. Newton's iteration is proposed to solve these fully coupled nonlinear equations, which is more efficient comparing to the widely adopted fixed-point iteration in the literatures and avoids the need to impose fluid pressure boundary condition when solving flow equations. A secant iterative method based on the stress intensity factor (SIF) is proposed to capture different propagation velocities of multiple fractures. The numerical results are compared with theoretical solutions in literatures to verify the accuracy of the method. The simultaneous propagation of multiple HFs is simulated by the newly proposed algorithm. The coupled influences of propagation regime, stress interaction, wellbore pressure loss and perforation entry loss on simultaneous propagation of multiple HFs are investigated.

Effective Wettability of Heterogenous Fracture Surfaces Using the Lattice-Boltzmann Method

NASA Astrophysics Data System (ADS)

E Santos, J.; Prodanovic, M.; Landry, C. J.

2017-12-01

Fracture walls in the subsurface are often structured by minerals of different composition (potentially further altered in contact with fluids during hydrocarbon extraction or CO2 sequestration), this yields in a heterogeneous wettability of the surface in contact with the fluids. The focus of our work is to study how surfaces presenting different mineralogy and roughness affect multiphase flow in fractures. Using the Shan-Chen model of the lattice-Boltzmann method (LBM) we define fluid interaction and surface attraction parameters to simulate a system of a wetting and a non-wetting fluid. In this work, we use synthetically created fractures presenting different arrangements of wetting and non-wetting patches, and with or without roughness; representative of different mineralogy, similar workflow can be applied to fractures extracted from X-ray microtomography images of fractures porous media. The results from the LBM simulations provide an insight on how the distribution of mineralogy and surface roughness are related with the observed macroscopic contact angle. We present a comparison between the published analytical models, and our results based on surface areas, spatial distribution and local fracture aperture. The understanding of the variables that affect the contact angle is useful for the comprehension of multiphase processes in naturally fractured reservoirs like primary oil production, enhanced oil recovery and CO2 sequestration. The macroscopic contact angle analytical equations for heterogeneous surfaces with variable roughness are no longer valid in highly heterogeneous systems; we quantify the difference thus offering an alternative to analytical models.

Optimizing for Large Planar Fractures in Multistage Horizontal Wells in Enhanced Geothermal Systems Using a Coupled Fluid and Geomechanics Simulator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Xiexiaomen; Tutuncu, Azra; Eustes, Alfred

Enhanced Geothermal Systems (EGS) could potentially use technological advancements in coupled implementation of horizontal drilling and multistage hydraulic fracturing techniques in tight oil and shale gas reservoirs along with improvements in reservoir simulation techniques to design and create EGS reservoirs. In this study, a commercial hydraulic fracture simulation package, Mangrove by Schlumberger, was used in an EGS model with largely distributed pre-existing natural fractures to model fracture propagation during the creation of a complex fracture network. The main goal of this study is to investigate optimum treatment parameters in creating multiple large, planar fractures to hydraulically connect a horizontal injectionmore » well and a horizontal production well that are 10,000 ft. deep and spaced 500 ft. apart from each other. A matrix of simulations for this study was carried out to determine the influence of reservoir and treatment parameters on preventing (or aiding) the creation of large planar fractures. The reservoir parameters investigated during the matrix simulations include the in-situ stress state and properties of the natural fracture set such as the primary and secondary fracture orientation, average fracture length, and average fracture spacing. The treatment parameters investigated during the simulations were fluid viscosity, proppant concentration, pump rate, and pump volume. A final simulation with optimized design parameters was performed. The optimized design simulation indicated that high fluid viscosity, high proppant concentration, large pump volume and pump rate tend to minimize the complexity of the created fracture network. Additionally, a reservoir with 'friendly' formation characteristics such as large stress anisotropy, natural fractures set parallel to the maximum horizontal principal stress (SHmax), and large natural fracture spacing also promote the creation of large planar fractures while minimizing fracture complexity.« less

Experimental investigation of heat transfer characteristics of guar-based polymer solutions and gels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Azouz, I.; Vinod, P.S.; Shah, S.N.

1996-12-31

An experimental investigation of the heat transfer characteristics of hydraulic fracturing fluids was conducted at the Fracturing Fluid Characterization Facility (FFCF) of the University of Oklahoma. The facility is equipped with a high pressure fracture simulator, coiled tubing fluid pre-conditioning system, and a full-scale, counter-current, double pipe heat exchanger. The fluids investigated include non-crosslinked and borate-crosslinked guar gum and hydroxypropyl guar (HPG). Results were also obtained for water and were used as a basis for comparison. The effects of flow rate, operating temperature, pH, and various levels of shear pre-conditioning, on the heat transfer behavior of the test fluids weremore » investigated. Results show a significant difference between the heat transfer coefficient of the pure solvent (water) and those of the polymer solutions tested. While all polymer solutions tested exhibited lower heat transfer coefficients than that of the pure solvent, crosslinking appears to enhance the heat transfer characteristics of the polymer fluids. It was also observed that shear preconditioning does not seem to have a significant effect on the heat transfer coefficient of the crosslinked gels. These findings are of great interest to the industry, especially to the petroleum industry where these fluids are commonly used during hydraulic fracturing of hydrocarbon reservoirs.« less

Different seismic signatures of fractures slip and their correlations with fluid pressures in in-situ rupture experiments

NASA Astrophysics Data System (ADS)

Derode, B.; Cappa, F.; Guglielmi, Y.

2012-04-01

The recent observations of non-volcanic tremors (NVT), slow-slip events (SSE), low- (LFE) and very-low (VLF) frequency earthquakes on seismogenic faults reveal that unexpected, large, non-linear transient deformations occur during the interseismic loading of the earthquake cycle. Such phenomena modify stress to the adjacent locked zones bringing them closer to failure. Recent studies indicated various driving factors such as high-fluid pressures and frictional processes. Here we focus on the role of fluids in the different seismic signatures observed in in-situ fractures slip experiments. Experiments were conducted in critically stressed fractures zone at 250 m-depth within the LSBB underground laboratory (south of France). This experiment seeks to explore the field measurements of temporal variations in fluid and stress through continuous monitoring of seismic waves, fluid pressures and mechanical deformations between boreholes and the ground surface. The fluid pressure was increased step-by-step in a fracture isolated between packers until a maximum value of 35 bars; a pressure analog to ones known to trigger earthquakes at crustal depths. We observed in the seismic signals: (1) Tremor-like signatures, (2) Low Frequency signatures, and (3) sudden and short ruptures like micro-earthquakes. By analogy, we suggest that fluid pressures may trigger these different seismic signatures in active faults.

Characterization and modeling of the stress and pore-fluid dependent acoustic properties of fractured porous rocks

NASA Astrophysics Data System (ADS)

Almrabat, Abdulhadi M.

The thesis presents the results of a study of the characterization and modeling of the stress and pore-fluid dependent acoustic properties of fractured porous rocks. A new laboratory High Pressure and High Temperature (HPHT) triaxial testing system was developed to characterize the seismic properties of sandstone under different levels of effective stress confinement and changes in pore-fluid composition. An intact and fractured of Berea sandstones core samples were used in the experimental studies. The laboratory test results were used to develop analytical models for stress-level and pore-fluid dependent seismic velocity of sandstones. Models for stress-dependent P and S-wave seismic velocities of sandstone were then developed based on the assumption that stress-dependencies come from the nonlinear elastic response of micro-fractures contained in the sample under normal and shear loading. The contact shear stiffness was assumed to increase linearly with the normal stress across a micro-fracture, while the contact normal stiffness was assumed to vary as a power law with the micro-fracture normal stress. Both nonlinear fracture normal and shear contact models were validated by experimental data available in the literature. To test the dependency of seismic velocity of sandstone on changes in pore-fluid composition, another series of tests were conducted where P and S-wave velocities were monitored during injection of supercritical CO 2 in samples of Berea sandstone initially saturated with saline water and under constant confining stress. Changes in seismic wave velocity were measured at different levels of supercritical CO2 saturation as the initial saline water as pore-fluid was displaced by supercritical CO 2. It was found that the P- iv wave velocity significantly decreased while the S-wave velocity remained almost constant as the sample supercritical CO2 saturation increased. The dependency of the seismic velocity on changes on pore fluid composition during injection of supercritical CO 2 in Berea sandstone was modeled using a re-derived Biot-Gassmann substitution theory. In using the Biot-Gassmann substitution theory, it was found necessary to account for the changes in the pore-fluid compressibility in terms of the volumetric proportion and distribution of saline water and supercritical CO 2 in the sample pore space. This was done by using the empirical model of Brie et al. to account for the compressibility of mixtures of two-phase immiscible fluids. The combined Biot-Gassman and Brie et al. models were found to represent adequately the changes in P-wave velocity of Berea sandstone during displacement of saline water by supercritical CO2. The third experimental and modeling study addressed shear-wave splitting due to the presence of fractures in a rock mass. Tests were conducted using the high temperature and high pressure (HPHT) triaxial device on samples of Berea sandstone, containing a single induced tensile fracture running along the height of the sample. The fracture was created via a modified Brazilian Split Test loading where the edges of cylindrical samples were loaded on diametrically opposite two points by sharp guillotines. The Joint Roughness Coefficient (JRC) values of the fractured core samples were determined by profilometry and tilt test. The effect of mismatching of the fracture surfaces on shear wave splitting was investigated by applying different amounts of shear displacements to three core samples. The degree of mismatching of the fracture surfaces in the core samples was evaluated using the Joint Matching Coefficient (JMC). Shear-wave splitting, as measured by the difference in magnitudes of shear-wave velocities parallel and perpendicular to the fracture, Vs1 and Vs2 respectively, increases with increasing mismatch of the fracture surfaces and decreases with increasing effective stress, and approaches zero in the effective stress range tested. A model for the stress and JMC dependent shear-wave splitting was developed based on the experimental observations. Finally, the magnitude of shear-wave splitting was correlated with the permeability of the fractured porous sandstone for fluid flow parallel to the induced fracture. (Abstract shortened by UMI.)

Elucidating Water Contamination by Fracturing Fluids and Formation Waters from Gas Wells: Integrating Isotopic and Geochemical Tracers

EPA Pesticide Factsheets

The objective of this presentation is to evaluate the potential and applicability of different geochemical and isotopic tracers for tracing the impacts of fracturing fluids and co-produced waters on water resources.

Approaching a universal scaling relationship between fracture stiffness and fluid flow

NASA Astrophysics Data System (ADS)

Pyrak-Nolte, Laura J.; Nolte, David D.

2016-02-01

A goal of subsurface geophysical monitoring is the detection and characterization of fracture alterations that affect the hydraulic integrity of a site. Achievement of this goal requires a link between the mechanical and hydraulic properties of a fracture. Here we present a scaling relationship between fluid flow and fracture-specific stiffness that approaches universality. Fracture-specific stiffness is a mechanical property dependent on fracture geometry that can be monitored remotely using seismic techniques. A Monte Carlo numerical approach demonstrates that a scaling relationship exists between flow and stiffness for fractures with strongly correlated aperture distributions, and continues to hold for fractures deformed by applied stress and by chemical erosion as well. This new scaling relationship provides a foundation for simulating changes in fracture behaviour as a function of stress or depth in the Earth and will aid risk assessment of the hydraulic integrity of subsurface sites.

Domain and rim growth kinetics in stratifying foam films

NASA Astrophysics Data System (ADS)

Zhang, Yiran; Yilixiati, Subinuer; Sharma, Vivek

Foam films are freely standing thin liquid films that typically consist of two surfactant-laden surfaces that are ~5 nm - 10 micron apart. Sandwiched between these interfacial layers is a fluid that drains primarily under the influence of viscous and interfacial forces, including disjoining pressure. Interestingly, a layered ordering of micelles inside the foam films (thickness <100 nm) leads to a stepwise thinning phenomena called stratification, which results in a thickness-dependent variation in reflected light intensity, visualized as progressively darker shades of gray. Thinner, darker domains spontaneously grow within foam films. During the initial expansion, a rim forms near the contact line between the growing thinner domain and the surrounding region, which influences the dynamics of domain growth as well as stratification Using newly developed interferometry digitial imaging optical microscopy (IDIOM) technique, we capture the rim evolution dynamics. Finally, we also develop a theoretical model to describe both rim evolution and domain growth dynamics.

Canyon Sand, Sonora basin: foam fracs hoped to slow production decline

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wash, R.

Rapid decline rates (60 to 80%/yr) in wells in the Conger-Penn field in Sterling County, Texas, have prompted Dorchester Exploration Corp. to try its first foam frac jobs on the Canyon Sand formation at 7000 to 7500 ft. Since Nov., the fracs have been performed on 3 wells: the Terry No. 31-4, the Terry No. 18-4, and the R.T. Foster No 11-4 in the southern portion of the field. Although it is still too early to tell whether the dramatic production drops have been arrested, personnel involved in the program seem pleased with the foam technique. The purpose behind Dorchester'smore » experimentation in this region is to decrease the amount of fluid that conventional frac jobs leave in the tight sand formation. The advantages of using foam fracs in this area are discussed.« less

Biomechanical Comparison of Inter-fragmentary Compression Pressures: Lag Screw versus Herbert Screw for Anterior Odontoid Screw Fixation.

PubMed

Park, Jin-Woo; Kim, Kyoung-Tae; Sung, Joo-Kyung; Park, Seong-Hyun; Seong, Ki-Woong; Cho, Dae-Chul

2017-09-01

The purpose of the present study was to compare inter-fragmentary compression pressures after fixation of a simulated type II odontoid fracture with the headless compression Herbert screw and a half threaded cannulated lag screw. We compared inter-fragmentary compression pressures between 40- and 45-mm long 4.5-mm Herbert screws (n=8 and n=9, respectively) and 40- and 45-mm long 4.0-mm cannulated lag screws (n=7 and n=10, respectively) after insertion into rigid polyurethane foam test blocks (Sawbones, Vashon, WA, USA). A washer load cell was placed between the two segments of test blocks to measure the compression force. Because the total length of each foam block was 42 mm, the 40-mm screws were embedded in the cancellous foam, while the 45-mm screws penetrated the denser cortical foam at the bottom. This enabled us to compare inter-fragmentary compression pressures as they are affected by the penetration of the apical dens tip by the screws. The mean compression pressures of the 40- and 45-mm long cannulated lag screws were 50.48±1.20 N and 53.88±1.02 N, respectively, which was not statistically significant (p=0.0551). The mean compression pressures of the 40-mm long Herbert screw was 52.82±2.17 N, and was not statistically significant compared with the 40-mm long cannulated lag screw (p=0.3679). However, 45-mm Herbert screw had significantly higher mean compression pressure (60.68±2.03 N) than both the 45-mm cannulated lag screw and the 40-mm Herbert screw (p=0.0049 and p=0.0246, respectively). Our results showed that inter-fragmentary compression pressures of the Herbert screw were significantly increased when the screw tip penetrated the opposite dens cortical foam. This can support the generally recommended surgical technique that, in order to facilitate maximal reduction of the fracture gap using anterior odontoid screws, it is essential to penetrate the apical dens tip with the screw.

Tracing ancient hydrogeological fracture network age and compartmentalisation using noble gases

NASA Astrophysics Data System (ADS)

Warr, Oliver; Sherwood Lollar, Barbara; Fellowes, Jonathan; Sutcliffe, Chelsea N.; McDermott, Jill M.; Holland, Greg; Mabry, Jennifer C.; Ballentine, Christopher J.

2018-02-01

We show that fluid volumes residing within the Precambrian crystalline basement account for ca 30% of the total groundwater inventory of the Earth (> 30 million km3). The residence times and scientific importance of this groundwater are only now receiving attention with ancient fracture fluids identified in Canada and South Africa showing: (1) microbial life which has existed in isolation for millions of years; (2) significant hydrogen and hydrocarbon production via water-rock reactions; and (3) preserving noble gas components from the early atmosphere. Noble gas (He, Ne, Ar, Kr, Xe) abundance and isotopic compositions provide the primary evidence for fluid mean residence time (MRT). Here we extend the noble gas data from the Kidd Creek Mine in Timmins Ontario Canada, a volcanogenic massive sulfide (VMS) deposit formed at 2.7 Ga, in which fracture fluids with MRTs of 1.1-1.7 Ga were identified at 2.4 km depth (Holland et al., 2013); to fracture fluids at 2.9 km depth. We compare here the Kidd Creek Mine study with noble gas compositions determined in fracture fluids taken from two mines (Mine 1 & Mine 2) at 1.7 and 1.4 km depth below surface in the Sudbury Basin formed by a meteorite impact at 1.849 Ga. The 2.9 km samples at Kidd Creek Mine show the highest radiogenic isotopic ratios observed to date in free fluids (e.g. 21Ne/22Ne = 0.6 and 40Ar/36Ar = 102,000) and have MRTs of 1.0-2.2 Ga. In contrast, resampled 2.4 km fluids indicated a less ancient MRT (0.2-0.6 Ga) compared with the previous study (1.1-1.7 Ga). This is consistent with a change in the age distribution of fluids feeding the fractures as they drain, with a decreasing proportion of the most ancient end-member fluids. 129Xe/136Xe ratios for these fluids confirm that boreholes at 2.4 km versus 2.9 km are sourced from hydrogeologically distinct systems. In contrast, results for the Sudbury mines have MRTs of 0.2-0.6 and 0.2-0.9 Ga for Mines 1 and 2 respectively. While still old compared to almost all groundwaters reported in the literature to date, these younger residence times compared to Kidd Creek Mine are consistent with significant fracturing created by the impact event, facilitating more hydrogeologic connection and mixing of fluids in the basin. In all samples from both Kidd Creek Mine and Sudbury, a 124-128Xe excess is identified over modern air values. This is attributed to an early atmospheric xenon component, previously identified at Kidd Creek Mine but which has to date not been observed in fluids with a residence time as recent as 0.2-0.6 Ga. The temporal and spatial sampling at Kidd Creek Mine is also used to verify our proposed conceptual model which provides key constraints regarding distribution, volumes and residence times of fracture fluids on the smaller, regional, scale.

Seismic characteristics of tensile fracture growth induced by hydraulic fracturing

NASA Astrophysics Data System (ADS)

Eaton, D. W. S.; Van der Baan, M.; Boroumand, N.

2014-12-01

Hydraulic fracturing is a process of injecting high-pressure slurry into a rockmass to enhance its permeability. Variants of this process are used for unconventional oil and gas development, engineered geothermal systems and block-cave mining; similar processes occur within volcanic systems. Opening of hydraulic fractures is well documented by mineback trials and tiltmeter monitoring and is a physical requirement to accommodate the volume of injected fluid. Numerous microseismic monitoring investigations acquired in the audio-frequency band are interpreted to show a prevalence of shear-dominated failure mechanisms surrounding the tensile fracture. Moreover, the radiated seismic energy in the audio-frequency band appears to be a miniscule fraction (<< 1%) of the net injected energy, i.e., the integral of the product of fluid pressure and injection rate. We use a simple penny-shaped crack model as a predictive framework to describe seismic characteristics of tensile opening during hydraulic fracturing. This model provides a useful scaling relation that links seismic moment to effective fluid pressure within the crack. Based on downhole recordings corrected for attenuation, a significant fraction of observed microseismic events are characterized by S/P amplitude ratio < 5. Despite the relatively small aperture of the monitoring arrays, which precludes both full moment-tensor analysis and definitive identification of nodal planes or axes, this ratio provides a strong indication that observed microseismic source mechanisms have a component of tensile failure. In addition, we find some instances of periodic spectral notches that can be explained by an opening/closing failure mechanism, in which fracture propagation outpaces fluid velocity within the crack. Finally, aseismic growth of tensile fractures may be indicative of a scenario in which injected energy is consumed to create new fracture surfaces. Taken together, our observations and modeling provide evidence that failure mechanisms documented by passive monitoring of hydraulic fractures may contain a significant component of tensile failure, including fracture opening and closing, although creation of extensive new fracture surfaces may be a seismically inefficient process that radiates at sub-audio frequencies.

Modeling thermal stress propagation during hydraulic stimulation of geothermal wells

NASA Astrophysics Data System (ADS)

Jansen, Gunnar; Miller, Stephen A.

2017-04-01

A large fraction of the world's water and energy resources are located in naturally fractured reservoirs within the earth's crust. Depending on the lithology and tectonic history of a formation, fracture networks can range from dense and homogeneous highly fractured networks to single large scale fractures dominating the flow behavior. Understanding the dynamics of such reservoirs in terms of flow and transport is crucial to successful application of engineered geothermal systems (also known as enhanced geothermal systems or EGS) for geothermal energy production in the future. Fractured reservoirs are considered to consist of two distinct separate media, namely the fracture and matrix space respectively. Fractures are generally thin, highly conductive containing only small amounts of fluid, whereas the matrix rock provides high fluid storage but typically has much smaller permeability. Simulation of flow and transport through fractured porous media is challenging due to the high permeability contrast between the fractures and the surrounding rock matrix. However, accurate and efficient simulation of flow through a fracture network is crucial in order to understand, optimize and engineer reservoirs. It has been a research topic for several decades and is still under active research. Accurate fluid flow simulations through field-scale fractured reservoirs are still limited by the power of current computer processing units (CPU). We present an efficient implementation of the embedded discrete fracture model, which is a promising new technique in modeling the behavior of enhanced geothermal systems. An efficient coupling strategy is determined for numerical performance of the model. We provide new insight into the coupled modeling of fluid flow, heat transport of engineered geothermal reservoirs with focus on the thermal stress changes during the stimulation process. We further investigate the interplay of thermal and poro-elastic stress changes in the reservoir. Combined with a analytical formulation for the injection temperatures in the open hole section of a geothermal well, the stress changes induced during the injection period of reservoir development can be studied.

An efficient hydro-mechanical model for coupled multi-porosity and discrete fracture porous media

NASA Astrophysics Data System (ADS)

Yan, Xia; Huang, Zhaoqin; Yao, Jun; Li, Yang; Fan, Dongyan; Zhang, Kai

2018-02-01

In this paper, a numerical model is developed for coupled analysis of deforming fractured porous media with multiscale fractures. In this model, the macro-fractures are modeled explicitly by the embedded discrete fracture model, and the supporting effects of fluid and fillings in these fractures are represented explicitly in the geomechanics model. On the other hand, matrix and micro-fractures are modeled by a multi-porosity model, which aims to accurately describe the transient matrix-fracture fluid exchange process. A stabilized extended finite element method scheme is developed based on the polynomial pressure projection technique to address the displacement oscillation along macro-fracture boundaries. After that, the mixed space discretization and modified fixed stress sequential implicit methods based on non-matching grids are applied to solve the coupling model. Finally, we demonstrate the accuracy and application of the proposed method to capture the coupled hydro-mechanical impacts of multiscale fractures on fractured porous media.

Acidization of shales with calcite cemented fractures

NASA Astrophysics Data System (ADS)

Kwiatkowski, Kamil; Szymczak, Piotr; Jarosiński, Marek

2017-04-01

Investigation of cores drilled from shale formations reveals a relatively large number of calcite-cemented fractures. Usually such fractures are reactivated during fracking and can contribute considerably to the permeability of the resulting fracture network. However, calcite coating on their surfaces effectively excludes them from production. Dissolution of the calcite cement by acidic fluids is investigated numerically with focus on the evolution of fracture morphology. Available surface area, breakthrough time, and reactant penetration length are calculated. Natural fractures in cores from Pomeranian shale formation (northern Poland) were analyzed and classified. Representative fractures are relatively thin (0.1 mm), flat and completely sealed with calcite. Next, the morphology evolution of reactivated natural fractures treated with low-pH fluids has been simulated numerically under various operating conditions. Depth-averaged equations for fracture flow and reactant transport has been solved by finite-difference method coupled with sparse-matrix solver. Transport-limited dissolution has been considered, which corresponds to the treatment with strong acids, such as HCl. Calcite coating in reactivated natural fractures dissolves in a highly non-homogeneous manner - a positive feedback between fluid transport and calcite dissolution leads to the spontaneous formation of wormhole-like patterns, in which most of the flow is focused. The wormholes carry reactive fluids deeper inside the system, which dramatically increases the range of the treatment. Non-uniformity of the dissolution patterns provides a way of retaining the fracture permeability even in the absence of the proppant, since the less dissolved regions will act as supports to keep more dissolved regions open. Evolution of fracture morphology is shown to depend strongly on the thickness of calcite layer - the thicker the coating the more pronounced wormholes are observed. However the interaction between wormholes is the strongest when coating thickness is a few times larger than the initial aperture of the fracture. This leads to formation of favorable complex networks of wormholes which provide adequate transport of reactive fluids to fracture surfaces and - at the same time - are capable of supporting fracture surfaces. As a conclusion, acidization of the reactivated fractures with hydrochloric acid seems to be an attractive treatment to apply at fracking stage or later on as EGR. The results contribute to the discussion on the use of acidization to enhance the gas production in the shale reservoirs. This communication stresses the importance of the dissolution of calcite cement in natural fractures in shale formations, which are initially sealed and become reactivated during fracking. While this research is based on the analysis of fractures in the Pomeranian shale basin its results are general enough to be applicable to different formations worldwide.

Pelvic fracture in multiple trauma: are we still up-to-date with massive fluid resuscitation?

PubMed

Burkhardt, Markus; Kristen, Alexander; Culemann, Ulf; Koehler, Daniel; Histing, Tina; Holstein, Joerg H; Pizanis, Antonius; Pohlemann, Tim

2014-10-01

Until today the mortality of complex pelvic trauma remains unacceptably high. On the one hand this could be attributed to a biological limit of the survivable trauma load, on the other hand side an ongoing inadequate treatment might be conceivable too. For the management of multiple trauma patients with life-threatening pelvic fractures, there is ongoing international debate on the adequate therapeutic strategy, e.g. arterial embolization or pelvic packing, as well as aggressive or restrained volume therapy. Whereas traditional pelvis-specific trauma algorithms still recommend massive fluid resuscitation, there is upcoming evidence that a restrained volume therapy in the preclinical setting may improve trauma outcomes. Less intravenous fluid administration may also reduce haemodilution and concomitant trauma-associated coagulopathy. After linking the data of the TraumaRegister DGU(®) and the German Pelvic Injury Register, for the first time, the initial fluid management for complex pelvic traumas as well as for different Tile/OTA types of pelvic ring fractures could be addressed. Unfortunately, the results could not answer the question of the adequate fluid resuscitation but confirmed the actuality of massive fluid resuscitation in the prehospital and emergency room setting. Low-volume resuscitation seems not yet accepted in practice in managing multiple trauma patients with pelvic fractures at least in Germany. Nevertheless, prevention of exsanguination and of complications like multiple organ dysfunction syndrome still poses a major challenge in the management of complex pelvic ring injuries. Even nowadays, fluid management for trauma, not only for pelvic fractures, remains a controversial area and further research is mandatory. Copyright © 2014 Elsevier Ltd. All rights reserved.

The Process of Hydraulic Fracturing

EPA Pesticide Factsheets

Hydraulic fracturing, know as fracking or hydrofracking, produces fractures in a rock formation by pumping fluids (water, proppant, and chemical additives) at high pressure down a wellbore. These fractures stimulate the flow of natural gas or oil.

Numerical tools to predict the environmental loads for offshore structures under extreme weather conditions

NASA Astrophysics Data System (ADS)

Wu, Yanling

2018-05-01

In this paper, the extreme waves were generated using the open source computational fluid dynamic (CFD) tools — OpenFOAM and Waves2FOAM — using linear and nonlinear NewWave input. They were used to conduct the numerical simulation of the wave impact process. Numerical tools based on first-order (with and without stretching) and second-order NewWave are investigated. The simulation to predict force loading for the offshore platform under the extreme weather condition is implemented and compared.

CFD RANS Simulations on a Generic Conventional Scale Model Submarine: Comparison between Fluent and OpenFOAM

DTIC Science & Technology

2015-09-01

lift and drag forces on two model car geometries (designated as the VRAK model and the S80 model). For the VRAK model the OpenFOAM drag coefficient was...lift coefficient was 16.5% higher than the Fluent value. Both model car geometries were meshed using Harpoon, which is a commercial software package...2. Clarke, G., Vun, S., Giacobello, M. and Reddy, R., “Estimation of ARH Tiger Fuselage Aerodynamic Characteristics Using Computational Fluid

Relative stability of tension band versus two-cortex screw fixation for treating fifth metatarsal base avulsion fractures.

PubMed

Husain, Z S; DeFronzo, D J

2000-01-01

This study assesses the strength of fixating avulsion fractures of the fifth metatarsal base with a 4.0-mm partially threaded cancellous screw crossing two cortices as compared to tension banding. Our data showed statistically significant fixation strength improvement over tension banding for avulsion fractures (p < 0.02) in both polystyrene foam models and fresh, nonpreserved frozen cadaveric samples. In cadavers, the screw fixations were able to withstand more than three times the load sustained by the tension band fixations. The study utilized the Instron 8500 tensiometer to apply physiologic loads to test the constructs until failure. The displacement and load data at failure show the limitations of both fixations. By increasing the load resistance while maintaining compression, the bicortical cancellous screw fixation created greater stability at the avulsion fracture of the fifth metatarsal base as compared to tension band stabilization.

Structural analysis characterization of permeability pathways across reservoir-seal interface - South-Eastern Utah; Results from integrated sedimentological, structural, and geochemical studies.

NASA Astrophysics Data System (ADS)

Petrie, E. S.; Evans, J. P.; Richey, D.; Flores, S.; Barton, C.; Mozley, P.

2015-12-01

Sedimentary rocks in the San Rafael Swell, Utah, were deformed by Laramide compression and subsequent Neogene extension. We evaluate the effect of fault damage zone morphology as a function of structural position, and changes in mechanical stratigraphy on the distribution of secondary minerals across the reservoir-seal pair of the Navajo Sandstone and overlying Carmel Formation. We decipher paleo-fluid migration and examine the effect faults and fractures have on reservoir permeability and efficacy of top seal for a range of geo-engineering applications. Map-scale faults have an increased probability of allowing upward migration of fluids along the fault plane and within the damage zone, potentially bypassing the top seal. Field mapping, mesoscopic structural analyses, petrography, and geochemical observations demonstrate that fault zone thickness increases at structural intersections, fault relay zones, fault-related folds, and fault tips. Higher densities of faults with meters of slip and dense fracture populations are present in relay zones relative to single, discrete faults. Curvature analysis of the San Rafael monocline and fracture density data show that fracture density is highest where curvature is highest in the syncline hinge and near faults. Fractures cross the reservoir-seal interface where fracture density is highest and structural diagensis includes mineralization events and bleaching and calcite and gypsum mineralization. The link between fracture distributions and structural setting implys that transmissive fractures have predictable orientations and density distributions. At the m- to cm- scale, deformation-band faults and joints in the Navajo Sandstone penetrate the reservoir-seal interface and transition into open-mode fractures in the caprock seal. Scanline analysis and petrography of veins provide evidence for subsurface mineralization and fracture reactivation, suggesting that the fractures act as loci for fluid flow through time. Heterolithic caprock seals with variable fracture distributions and morphology highlight the strong link between the variation in material properties and the response to changing stress conditions. The variable connectivity of fractures and the changes in fracture density plays a critical role in subsurface fluid flow.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verba, Circe; Montross, Scott; Spaulding, Richard

Geologic carbon storage (GCS) is a potentially viable strategy to reduce greenhouse emissions. Understanding the risks to engineered and geologic structures associated with GCS is an important first step towards developing practices for safe and effective storage. The widespread utilization of foamed cement in wells may mean that carbon dioxide (CO 2)/brine/foamed cement reactions may occur within these GCS sites. Characterizing the difference in alteration rates as well as the physical and mechanical impact of CO 2/brine/foamed cement is an important preliminary step to ensuring offshore and onshore GCS is a prudent anthropogenic CO 2 mitigation choice. In a typicalmore » oil and gas well, cement is placed in the annulus between the steel casing and formation rock for both zonal isolation and casing support. The cement must have sufficient strength to secure the casing in the hole and withstand the stress of drilling, perforating, and fracturing (e.g. API, 1997, 2010 Worldwide Cementing Practices). As such, measuring the mechanical and properties of cement is an important step in predicting cement behavior under applied downhole stresses (Nelson, 2006). Zonal isolation is the prevention of fluids migrating to different zones outside of the casing and is strongly impacted by the permeability of the wellbore cement (Nelson, 2006). Zonal isolation depends on both the mechanical behavior and permeability (a physical property) of the cement (Mueller and Eid, 2006; Nelson, 2006). Long-term integrity of cement depends on the mechanical properties of the cement sheath, such as Young’s Modulus (Griffith et al., 2004). The cement sheath’s ability to withstand the stresses from changes in pressure and temperature is predominantly determined by the mechanical properties, including Young’s modulus, Poisson’s ratio, and tensile strength. Any geochemical alteration may impact both the mechanical and physical properties of the cement, thus ultimately impacting the structural integrity of the wellbore. In this study, atmospheric foamed cements were generated using a neat cement and three foam qualities (volume of entrained gas in the cement) - 10%, 20%, and 30 % gas volume. The samples were immersed in a 0.25 M NaCl brine followed by the injection of supercritical CO 2 at 28.9 MPa and 50°C. Petrophysical properties were examined for representative samples using computed tomography (CT) and scanning electron microscopy (SEM). CT scanning of representative samples across the range of reacted cements revealed macroscopic changes in structure due to brine/CO 2/cement interactions. The high foam quality samples resulted in more CO 2-saturated brine infiltrating radially deeper into the cement and thus were more susceptible to alteration. After 56 days of exposure, the 30% foam quality sample had the most reaction resulting in an alteration depth of 8.35 ± 0.13 mm with a calculated 34.6 ± 0.2% reacted area and 5.76 ± 0.2% reacted pore space area. The neat sample on the other hand, had a reaction depth of 0.31 ± 0.13 mm with a calculated 0.15 ± 0.08% reacted area and 0.57 ± 0.05% reacted pore area. Physical measurements of the exposed samples were consistent with this degree of alteration having 47.02% porosity and the highest permeability of 0.041 mD. These results indicate that the greater surface area provided by the increase of pore space in the higher quality foam coupled with carbonate diffusion reactions enabled greater alteration.« less

Dispersion in Fractures with Ramified Dissolution Patterns

NASA Astrophysics Data System (ADS)

Xu, Le; Marks, Benjy; Toussaint, Renaud; Flekkøy, Eirik G.; Måløy, Knut J.

2018-04-01

The injection of a reactive fluid into an open fracture may modify the fracture surface locally and create a ramified structure around the injection point. This structure will have a significant impact on the dispersion of the injected fluid due to increased permeability, which will introduce large velocity fluctuations into the fluid. Here, we have injected a fluorescent tracer fluid into a transparent artificial fracture with such a ramified structure. The transparency of the model makes it possible to follow the detailed dispersion of the tracer concentration. The experiments have been compared to two dimensional (2D) computer simulations which include both convective motion and molecular diffusion. A comparison was also performed between the dispersion from an initially ramified dissolution structure and the dispersion from an initially circular region. A significant difference was seen both at small and large length scales. At large length scales, the persistence of the anisotropy of the concentration distribution far from the ramified structure is discussed with reference to some theoretical considerations and comparison with simulations.

Core Flooding Experiments Combined with X-rays and Micro-PET Imaging as a Tool to Calculate Fluid Saturations in a Fracture

NASA Astrophysics Data System (ADS)

Gran, M.; Zahasky, C.; Garing, C.; Pollyea, R. M.; Benson, S. M.

2017-12-01

One way to reduce CO2 emissions is to capture CO2 generated in power plants and other industrial sources to inject it into a geological formation. Sedimentary basins are the ones traditionally used to store CO2 but the emission sources are not always close to these type of basins. In this case, basalt rocks present a good storage alternative due their extent and also their potential for mineral trapping. Flow through basaltic rocks is governed by the permeable paths provided by rock fractures. Hence, knowing the behavior of the multiphase flow in these fractures becomes crucial. With the aim to describe how aperture and liquid-gas interface changes in the fracture affect relative permeability and what are the implications of permeability stress dependency, a series of core experiments were conducted. To calculate fracture apertures and fluid saturations, core flooding experiments combined with medical X-Ray CT scanner and micro-PET imaging (Micro Positron Emission Tomography) were performed. Capillary pressure and relative permeability drainage curves were simultaneously measured in a fractured basalt core under typical storage reservoir pressures and temperatures. The X-Ray scanner allows fracture apertures to be measured quite accurately even for fractures as small as 30 µ, but obtaining fluid saturations is not straightforward. The micro-PET imaging provides dynamic measurements of tracer distributions which can be used to calculate saturation. Here new experimental data is presented and the challenges associated with measuring fluid saturations using both X-Rays and micro-PET are discussed.

Smart magnetic markers use in hydraulic fracturing.

PubMed

Zawadzki, Jarosław; Bogacki, Jan

2016-11-01

One of the main challenges and unknowns during shale gas exploration is to assess the range and efficiency of hydraulic fracturing. It is also essential to assess the distribution of proppant, which keeps the fracture pathways open. Solving these problems may considerably increase the efficiency of the shale gas extraction. Because of that, the idea of smart magnetic marker, which can be detected when added to fracturing fluid, has been considered for a long time. This study provides overview of the possibilities of magnetic marker application for shale gas extraction. The imaging methods using electromagnetic markers, are considered or developed in two directions. The first possibility is the markers' electromagnetic activity throughout the whole volume of the fracturing fluid. Thus, it can be assumed that the whole fracturing fluid is the marker. Among these type of hydraulic fracturing solutions, ferrofluid could be considered. The second possibility is marker, which is just one of many components of the fracturing fluid. In this case feedstock magnetic materials, ferrites and nanomaterials could be considered. Magnetic properties of magnetite could be too low and ferrofluids' or nanomaterials' price is unacceptably high. Because of that, ferrites, especially ZnMn ferrites seems to be the best material for magnetic marker. Because of the numerous applications in electronics, it is cheap and easily available, although the price is higher, then that of magnetite. The disadvantage of using ferrite, could be too small mechanical strength. It creates an essential need for combining magnetic marker with proppant into magnetic-ceramic composite. Copyright © 2016 Elsevier Ltd. All rights reserved.

Application of Reservoir Flow Simulation Integrated with Geomechanics in Unconventional Tight Play

NASA Astrophysics Data System (ADS)

Lin, Menglu; Chen, Shengnan; Mbia, Ernest; Chen, Zhangxing

2018-01-01

Multistage hydraulic fracturing techniques, combined with horizontal drilling, have enabled commercial production from the vast reserves of unconventional tight formations. During hydraulic fracturing, fracturing fluid and proppants are pumped into the reservoir matrix to create the hydraulic fractures. Understanding the propagation mechanism of hydraulic fractures is essential to estimate their properties, such as half-length. In addition, natural fractures are often present in tight formations, which might be activated during the fracturing process and contribute to the post-stimulation well production rates. In this study, reservoir simulation is integrated with rock geomechanics to predict the well post-stimulation productivities. Firstly, a reservoir geological model is built based on the field data collected from the Montney formation in the Western Canadian Sedimentary Basin. The hydraulic fracturing process is then simulated through an integrated approach of fracturing fluid injection, rock geomechanics, and tensile failure criteria. In such a process, the reservoir pore pressure increases with a continuous injection of the fracturing fluid and proppants, decreasing the effective stress exerted on the rock matrix accordingly as the overburden pressure remains constant. Once the effective stress drops to a threshold value, tensile failure of the reservoir rock occurs, creating hydraulic fractures in the formation. The early production history of the stimulated well is history-matched to validate the predicted fracture geometries (e.g., half-length) generated from the fracturing simulation process. The effects of the natural fracture properties and well bottom-hole pressures on well productivity are also studied. It has been found that nearly 40% of hydraulic fractures propagate in the beginning stage (the pad step) of the fracturing schedule. In addition, well post-stimulation productivity will increase significantly if the natural fractures are propped or partially propped by the proppants. This paper provides insights on fracture propagation and can be a reference for fracturing treatments in unconventional tight reservoirs.

Micro- and macro-behaviour of fluid flow through rock fractures: an experimental study

NASA Astrophysics Data System (ADS)

Zhang, Zhenyu; Nemcik, Jan; Ma, Shuqi

2013-12-01

Microscopic and macroscopic behaviour of fluid flow through rough-walled rock fractures was experimentally investigated. Advanced microfluidic technology was introduced to examine the microscopic viscous and inertial effects of water flow through rock fractures in the vicinity of voids under different flow velocities, while the macroscopic behaviour of fracture flow was investigated by carrying out triaxial flow tests through fractured sandstone under confining stresses ranging from 0.5 to 3.0 MPa. The flow tests show that the microscopic inertial forces increase with the flow velocity with significant effects on the local flow pattern near the voids. With the increase in flow velocity, the deviation of the flow trajectories is reduced but small eddies appear inside the cavities. The results of the macroscopic flow tests show that the linear Darcy flow occurs for mated rock fractures due to small aperture, while a nonlinear deviation of the flow occurs at relatively high Reynolds numbers in non-mated rock fracture (Re > 32). The microscopic experiments suggest that the pressure loss consumed by the eddies inside cavities could contribute to the nonlinear fluid flow behaviour through rock joints. It is found that such nonlinear flow behaviour is best matched with the quadratic-termed Forchheimer equation.

Experimental observation of water saturation effects on shear wave splitting in synthetic rock with fractures aligned at oblique angles

NASA Astrophysics Data System (ADS)

Amalokwu, Kelvin; Chapman, Mark; Best, Angus I.; Sothcott, Jeremy; Minshull, Timothy A.; Li, Xiang-Yang

2015-01-01

Fractured rocks are known to exhibit seismic anisotropy and shear wave splitting (SWS). SWS is commonly used for fractured rock characterization and has been shown to be sensitive to fluid type. The presence of partial liquid/gas saturation is also known to affect the elastic properties of rocks. The combined effect of both fractures and partial liquid/gas saturation is still unknown. Using synthetic, silica-cemented sandstones with aligned penny-shaped voids, we conducted laboratory ultrasonic experiments to investigate the effect fractures aligned at an oblique angle to wave propagation would have on SWS under partial liquid/gas saturation conditions. The result for the fractured rock shows a saturation dependence which can be explained by combining a fractured rock model and a partial saturation model. At high to full water saturation values, SWS decreases as a result of the fluid bulk modulus effect on the quasi-shear wave. This bulk modulus effect is frequency dependent as a result of wave-induced fluid flow mechanisms, which would in turn lead to frequency dependent SWS. This result suggests the possible use of SWS for discriminating between full liquid saturation and partial liquid/gas saturation.

CO2 injection into fractured peridotites: a reactive percolation experiment

NASA Astrophysics Data System (ADS)

Escario, S.; Godard, M.; Gouze, P.; Leprovost, R.; Luquot, L.; Garcia-Rios, M.

2017-12-01

Mantle peridotites have the potential to trap CO2 as carbonates. This process observed in ophiolites and in oceanic environments provides a long term and safe storage for CO2. It occurs as a part of a complex suite of fluid-rock reactions involving silicate dissolution and precipitation of hydrous phases, carbonates and minor phases that may in turn modify the hydrodynamic properties and the reactivity of the reacted rocks. The efficiency and lastingness of the process require the renewal of fluids at the mineral-fluid interface. Fractures are dominant flow paths in exhumed mantle sections. This study aims at better understanding the effect of CO2-enriched saline fluids on hydrodynamic and chemical processes through fractured peridotites. Experiments were performed using the reactive percolation bench ICARE Lab 3 - Géosciences Montpellier. It allows monitoring the permeability changes during experiments. Effluents are recurrently sampled for analysing cation concentration, pH and alkalinity. Reacted rock samples were characterized by high resolution X-ray microtomography (ESRF ID19, Grenoble, France) and SEM. Experiments consisted in injecting CO2-enriched brines (NaCl 0.5 M) at a rate of 6 mL.h-1 into artificially fractured cores (9 mm diameter × 20 mm length) of Oman harzburgites at T=170°C and Ptotal = 25 MPa for up to 2 weeks. Fractures are of few µm apertures with rough walls. Three sets of experiments were performed at increasing value of [CO2] (0, 0.1 and 1 mol/kg). All experiments showed a decrease in permeability followed by steady state regime that can be caused by a decrease in the roughness of fracture walls (dissolution dominated process), thus favouring fracture closing, or by the precipitation of secondary phases. Maximum enrichments in Mg, Fe and Ca of the effluent fluids occur during the first 2 hours of the experiments whereas Si displays a maximum enrichment at t = 20 h, suggesting extensive dissolution. Maximum enrichments are observed with the highest values of the [CO2]. After one day, effluent fluid concentrations decrease and become constant. By analysing both the permeability and the outlet fluid concentration one can investigate the coupling processes controlling the transport and the reaction mechanisms that in turn act at maintaining the circulation in the fractures.

Application of borehole geophysics in defining the wellhead protection area for a fractured crystalline bedrock aquifer

USGS Publications Warehouse

Vernon, J.H.; Paillet, F.L.; Pedler, W.H.; Griswold, W.J.

1993-01-01

Wellbore geophysical techniques were used to characterize fractures and flow in a bedrock aquifer at a site near Blackwater Brook in Dover, New Hampshire. The primary focus ofthis study was the development of a model to assist in evaluating the area surrounding a planned water supply well where contaminants introduced at the land surface might be induced to flow towards a pumping well. Well logs and geophysical surveys used in this study included lithologic logs based on examination of cuttings obtained during drilling; conventional caliper and natural gamma logs; video camera and acoustic televiewer surveys; highresolution vertical flow measurements under ambient conditions and during pumping; and borehole fluid conductivity logs obtained after the borehole fluid was replaced with deionized water. These surveys were used for several applications: 1) to define a conceptual model of aquifer structure to be used in groundwater exploration; 2) to estimate optimum locations for test and observation wells; and 3) to delineate a wellhead protection area (WHPA) for a planned water supply well. Integration of borehole data with surface geophysical and geological mapping data indicated that the study site lies along a northeast-trending intensely fractured contact zone between surface exposures of quartz monzonite and metasedimentary rocks. Four of five bedrock boreholes at the site were estimated to produce more than 150 gallons per minute (gpm) (568 L/min) of water during drilling. Aquifer testing and other investigations indicated that water flowed to the test well along fractures parallel to the northeast-trending contact zone and along other northeast and north-northwest-trending fractures. Statistical plots of fracture strikes showed frequency maxima in the same northeast and north-northwest directions, although additional maxima occurred in other directions. Flowmeter surveys and borehole fluid conductivity logging after fluid replacement were used to identify water-producing zones in the boreholes; fractures associated with inflow into boreholes showed a dominant northeast orientation. Borehole fluid conductivity logging after fluid replacement also gave profiles of such water-quality parameters as fluid electrical conductivity (FEC), pH, temperature, and oxidation-reduction potential, strengthening the interpretation of crossconnection of boreholes by certain fracture zones. The results of this study showed that the application of these borehole geophysical techniques at the Blackwater Brook site led to an improved understanding of such parameters as fracture location, attitude, flow direction and velocity, and water quality; all of which are important in the determination of a WHPA.

Models to teach lung sonopathology and ultrasound-guided thoracentesis.

PubMed

Wojtczak, Jacek A

2014-12-01

Lung sonography allows rapid diagnosis of lung emergencies such as pulmonary edema, hemothorax or pneumothorax. The ability to timely diagnose an intraoperative pneumothorax is an important skill for the anesthesiologist. However, lung ultrasound exams require an interpretation of not only real images but also complex acoustic artifacts such as A-lines and B-lines. Therefore, appropriate training to gain proficiency is important. Simulated environment using ultrasound phantom models allows controlled, supervised learning. We have developed hybrid models that combine dry or wet polyurethane foams, porcine rib cages and human hand simulating a rib cage. These models simulate fairly accurately pulmonary sonopathology and allow supervised teaching of lung sonography with the immediate feedback. In-vitro models can also facilitate learning of procedural skills, improving transducer and needle positioning and movement, rapid recognition of thoracic anatomy and hand - eye coordination skills. We described a new model to teach an ultrasound guided thoracentesis. This model consists of the experimenter's hand placed on top of the water-filled container with a wet foam. Metacarpal bones of the human hand simulate a rib cage and a wet foam simulates a diseased lung immersed in the pleural fluid. Positive fluid flow offers users feedback when a simulated pleural effusion is accurately assessed.

The Effect of Contact Area on the Fluid Flow-Fracture Specific Stiffness Relationship

NASA Astrophysics Data System (ADS)

Petrovitch, C.; Pyrak-Nolte, L. J.; Nolte, D. D.

2009-12-01

The integrity of subsurface CO2 sequestration sites can be compromised by the presence of mechanical discontinuities such as fractures, joints and faults. The ability to detect, seismically, and determine whether a discontinuity poses a risk, requires an understanding of the interrelationships among the mechanical, hydraulic and seismic properties of fractures rock. We performed a computational study to investigate the effect of fracture geometry on the relationship between fluid flow and fracture specific stiffness. The form of this relationship and the ability to scale it among different sample sizes provides a key link between the hydraulic and seismic response of fractures. In this study, model fracture topologies were simulated using the stratified continuum percolation method. This method constructs a hierarchical aperture distribution with a tunable spatial correlation length. Fractures with correlated and uncorrelated aperture distributions were used. The contact area across the fracture plane ranged from approximately 5% to 40%. The fracture specific stiffness was calculated by deforming each fracture numerically under a normal load and extracting the stiffness from the displacement-stress curves. Single-phase flow was calculated for each increment of stress by modeling the fracture topology as a network of elliptical pipes and solving the corresponding linear system of equations. We analyzed the relationship between fracture displacement and contact area and found that the correlation length associated with the contact area distribution enables a scaling relationship between displacement and contact area. The collapse of the fluid flow - stress relationship required use of standard percolation functional forms that use average aperture (cubic law), the void area fraction, and the correlation length of the contact area clusters. A final scaling relationship between fluid flow and fracture specific was found for the class of correlated fractures while a separate relationship was found for the uncorrelated fractures. By expanding the scaling parameters to include additional length scales, it may be possible to unify all of the flow-stiffness relationships, independent of geometry. Acknowledgments: The authors wish to acknowledge support of this work by the Geosciences Research Program, Office of Basic Energy Sciences US Department of Energy (DEFG02-97ER14785 08), the GeoMathematical Imaging Group at Purdue University and from the Computer Research Institute At Purdue University.

Temporal dynamics of halogenated organic compounds in Marcellus Shale flowback.

PubMed

Luek, Jenna L; Harir, Mourad; Schmitt-Kopplin, Philippe; Mouser, Paula J; Gonsior, Michael

2018-06-01

The chemistry of hydraulic fracturing fluids and wastewaters is complex and is known to vary by operator, geologic formation, and fluid age. A time series of hydraulic fracturing fluids, flowback fluids, and produced waters was collected from two adjacent Marcellus Shale gas wells for organic chemical composition analyses using ultrahigh resolution mass spectrometry. Hierarchical clustering was used to compare and extract ions related to different fluid ages and many halogenated organic molecular ions were identified in flowback fluids and early produced waters based on exact mass. Iodinated organic compounds were the dominant halogen class in these clusters and were nearly undetectable in hydraulic fracturing fluid prior to injection. The iodinated ions increased in flowback and remained elevated after ten months of well production. We suggest that these trends are mainly driven by dissolved organic matter reacting with reactive halogen species formed abiotically through oxidizing chemical additives applied to the well and biotically via iodide-oxidizing bacteria. Understanding the implications of these identified halogenated organic compounds will require future investigation in to their structures and environmental fate. Copyright © 2018 Elsevier Ltd. All rights reserved.

Empirically assessing the potential release of rare earth elements from black shale under simulated hydraulic fracturing conditions

DOE PAGES

Yang, Jon; Verba, Circe; Torres, Marta; ...

2018-02-01

Rare earth elements (REEs) are economically important to modern society and the rapid growth of technologies dependent on REEs has placed considerable economic pressure on their sourcing. This study addresses whether REEs could be released as a byproduct of natural gas extraction from a series of experiments that were designed to simulate hydraulic fracturing of black shale under various pressure (25 and 27.5 MPa) and temperature (50, 90, 130 °C) conditions. The dissolved REEs in the reacted fluids displayed no propensity for the REEs to be released from black shale under high pressure and temperature conditions, a result that ismore » consistent across the different types of fluids investigated. Overall, there was a net loss of REEs from the fluid. These changes in dissolved REEs were greatest at the moment the fluids first contacted the shale and before the high temperature and high pressure conditions were imposed, although the magnitude of these changes (10 -4 μg/g) were small compared to the magnitude of the total REE content present in the solid shale samples (10 2 μg/g). These results highlight the variability and complexity of hydraulic fracturing systems and indicate that REE may not serve as robust tracers for fracturing fluid-shale reactions. Additionally, the results suggest that significant quantities of REEs may not be byproducts of hydraulically fractured shales.« less

Empirically assessing the potential release of rare earth elements from black shale under simulated hydraulic fracturing conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Jon; Verba, Circe; Torres, Marta

Rare earth elements (REEs) are economically important to modern society and the rapid growth of technologies dependent on REEs has placed considerable economic pressure on their sourcing. This study addresses whether REEs could be released as a byproduct of natural gas extraction from a series of experiments that were designed to simulate hydraulic fracturing of black shale under various pressure (25 and 27.5 MPa) and temperature (50, 90, 130 °C) conditions. The dissolved REEs in the reacted fluids displayed no propensity for the REEs to be released from black shale under high pressure and temperature conditions, a result that ismore » consistent across the different types of fluids investigated. Overall, there was a net loss of REEs from the fluid. These changes in dissolved REEs were greatest at the moment the fluids first contacted the shale and before the high temperature and high pressure conditions were imposed, although the magnitude of these changes (10 -4 μg/g) were small compared to the magnitude of the total REE content present in the solid shale samples (10 2 μg/g). These results highlight the variability and complexity of hydraulic fracturing systems and indicate that REE may not serve as robust tracers for fracturing fluid-shale reactions. Additionally, the results suggest that significant quantities of REEs may not be byproducts of hydraulically fractured shales.« less

Laboratory simulations of fluid-induced seismicity in shallow volcanic faults

NASA Astrophysics Data System (ADS)

Fazio, Marco; Benson, Philip; Vinciguerra, Sergio; Meredith, Philip

2015-04-01

Seismicity is a key tool used for monitoring fracturing and faulting in around volcanoes, with a particular emphasis placed on the frequency (Long period or Low Frequency, LF events) thought to be due to fluid movement, as compared to Volcano-Tectonic activity driven by pure fracture. To better understand these fundamental processes this research presents new rock deformation experiments designed to simulate shallow volcano-tectonic pressure/temperature conditions, linking pore fluid flow to the induced seismicity. A particular emphasis is placed on the conditions of pressure and temperature required to stimulate LF activity. Our setup imposes a rapid pore pressure release or "venting" via a small pre-drilled axial conduit to stimulate rapid fluid movement through an established fracture damage zone via a two stage process. Firstly experiments are conducted to generate a through-going shear fracture, with pore fluid connectivity to this fracture enhanced via the axial conduit. The shear failure is imaged via AE location with ~mm scale accuracy. The second stage vents pore fluid pressure via an electrical solenoid valve. We find that this second stage is accompanied by a swarm of LF activity akin to Long Period (LP) activity on active volcanoes. We find that a significant change in the dominant frequency of LF events is recorded as pore fluid pressure decrease through, and beyond, the water boiling point and the transition between LF and VLF occurred at the pressure at which the superheated water turn to vapour. In addition, we observe a significant dependence of the recorded LF upon the fluid flow rate. Finally, we present new data using low frequency (200 kHz) AE sensors, in conjunction with our standard 1 MHz-central-frequency sensors, which permit us to better constraint LF and VLF events with lower attenuation, and hence an improved characterization of these LF seismic signals. Data are used to forecast the final time of failure via the fracture forecast methods of Kilburn (2004), showing a good correlation between measured sample failure time and the forecast time based on AE event rate. Our data showed little change in forecast accuracy when using LF data compared to regular HF data, illustrating the importance of newly fracturing surfaces in the application of such models.

Laboratory simulations of fluid-induced seismicity in shallow volcanic faults

NASA Astrophysics Data System (ADS)

Fazio, M.; Benson, P. M.; Vinciguerra, S.

2014-12-01

Seismicity is a key tool used for monitoring fracturing and faulting in around volcanoes, with a particular emphasis placed on the frequency (Long period or Low Frequency, LF events) thought to be due to fluid movement, as compared to Volcano-Tectonic activity driven by pure fracture. To better understand these fundamental processes this research presents new rock deformation experiments designed to simulate shallow volcano-tectonic pressure/temperature conditions, linking pore fluid flow to the induced seismicity. A particular emphasis is placed on the conditions of pressure and temperature required to stimulate LF activity. Our setup imposes a rapid pore pressure release or "venting" via a small pre-drilled axial conduit to stimulate rapid fluid movement through an established fracture damage zone via a two stage process. Firstly experiments are conducted to generate a through-going shear fracture, with pore fluid connectivity to this fracture enhanced via the axial conduit. The shear failure is imaged via AE location with ~mm scale accuracy. The second stage vents pore fluid pressure via an electrical solenoid valve. We find that this second stage is accompanied by a swarm of LF activity akin to Long Period (LP) activity on active volcanoes. We find that a significant change in the dominant frequency of LF events is recorded as pore fluid pressure decrease through, and beyond, the water boiling point and the transition between LF and VLF occurred at the pressure at which the superheated water turn to vapour. In addition, we observe a significant dependence of the recorded LF upon the fluid flow rate. Finally, we present new data using low frequency (200 kHz) AE sensors, in conjunction with our standard 1 MHz-central-frequency sensors, which permit us to better constraint LF and VLF events with lower attenuation, and hence an improved characterization of these LF seismic signals. Data are used to forecast the final time of failure via the fracture forecast methods of Kilburn (2004), showing a good correlation between measured sample failure time and the forecast time based on AE event rate. Our data showed little change in forecast accuracy when using LF data compared to regular HF data, illustrating the importance of newly fracturing surfaces in the application of such models.

Exploring the deep, ancient hydrogeosphere within Precambrian crystalline rocks using noble gases

NASA Astrophysics Data System (ADS)

Warr, O.; Sherwood Lollar, B.; Fellowes, J.; Sutcliffe, C. N.; McDermott, J. M.; Holland, G.; Mabry, J.; Ballentine, C. J.

2016-12-01

Serpentinization is a key long-term water-rock interaction occurring within isolated fractures in Precambrian crystalline rocks and is a significant source of global H2 production. Highly saline fracture fluids, containing in-situ produced dissolved gases (e.g. percent level He, abiogenic CH4 and mM H2), have revealed microbial ecosystems isolated from the surface photosphere for millions of years. Noble gases can provide crucial physical and temporal constraints on these serpentinizing and life-supporting environments via radiogenic-derived fluid residence times, while also providing evidence of isolation. New noble gas data is presented here from four locations on the Canadian Shield. Kidd Creek Mine in Ontario, where fluids with a mean residence time ≥ 1.1 Ga were identified in 2013, was revisited with resampling of the waters from 2.4 km bls (below land surface), and new samples collected from 2.9 km bls. The study was also expanded to include two mines from Sudbury, Ontario at 1.7 (Mine 1) and 1.4 (Mine 2) km bls. The radiogenic excesses within the fluids were greatest for the 2.9 km Kidd Creek samples and provided an average residence time of 1.6 Ga. Consistent with our hypothesis, the resampling of the 2.4 km fluids (80 months after the original study) reveal significantly reduced residence times (1.1 Ga to 390 Ma) due to stress-induced opening of younger, though nonetheless old, fractures. This is supported by recent sulphur isotope, and 2H & 18O data. Additional hydrogeological constraints are provided by the 129Xe & 136Xe data, which suggest distinct fracture networks feed the 2.4 km, and the 2.9 km systems. Fracture fluids in the Sudbury Basin were targeted to investigate the influence of a later 1.8 Ga bolide impact which formed major fractures in the underlying basement. As hypothesised the fluids in the Sudbury Archean basement are younger than those at Kidd Creek, with mean residence times of 313 and 544 Ma for Mine 1 and 2 respectively. Our results demonstrate that ancient fracture fluids in the Precambrian crust represent a previously under-investigated groundwater domain and H2 source. With mean residence times of 0.3-1.6 Ga, they provide an opportunity to explore an unprecedented ancient component of the Earth's hydrogeosphere.

Multiple pickering emulsions stabilized by microbowls.

PubMed

Nonomura, Yoshimune; Kobayashi, Naoto; Nakagawa, Naoki

2011-04-19

Some researchers have focused on the adsorption of solid particles at fluid-fluid interfaces and prepared emulsions and foams called "Pickering emulsions/foams". However, while several reports exist on simple spherical emulsions, few reports are available on the formation of more complex structures. Here, we show that holes on particle surfaces are a key factor in establishing the variety and complexity of mesoscale structures. Microbowls, which are hollow particles with holes on their surfaces, form multiple emulsions (water-in-oil-in-water and oil-in-water-in-oil emulsions) by simply mixing them with water and oil. Furthermore, stable potato-like or coffee-bean-like emulsions are also obtained, although nonspherical emulsions are usually unstable because of their larger interfacial energies. These findings are useful in designing the building blocks of complex supracolloidal systems for pharmaceutical, food, and cosmetic products. © 2011 American Chemical Society

Comparison of Hydrodynamic Load Predictions Between Engineering Models and Computational Fluid Dynamics for the OC4-DeepCwind Semi-Submersible: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benitz, M. A.; Schmidt, D. P.; Lackner, M. A.

Hydrodynamic loads on the platforms of floating offshore wind turbines are often predicted with computer-aided engineering tools that employ Morison's equation and/or potential-flow theory. This work compares results from one such tool, FAST, NREL's wind turbine computer-aided engineering tool, and the computational fluid dynamics package, OpenFOAM, for the OC4-DeepCwind semi-submersible analyzed in the International Energy Agency Wind Task 30 project. Load predictions from HydroDyn, the offshore hydrodynamics module of FAST, are compared with high-fidelity results from OpenFOAM. HydroDyn uses a combination of Morison's equations and potential flow to predict the hydrodynamic forces on the structure. The implications of the assumptionsmore » in HydroDyn are evaluated based on this code-to-code comparison.« less

D-foam-induced flavor condensates and breaking of supersymmetry in free Wess-Zumino fluids

NASA Astrophysics Data System (ADS)

Mavromatos, Nick E.; Sarkar, Sarben; Tarantino, Walter

2011-08-01

Recently [N. E. Mavromatos and S. Sarkar, New J. Phys. 10, 073009 (2008) NJOPFM1367-263010.1088/1367-2630/10/7/073009; N. E. Mavromatos, S. Sarkar, and W. Tarantino, Phys. Rev. DPRVDAQ1550-7998 80, 084046 (2009)10.1103/PhysRevD.80.084046], we argued that a particular model of string-inspired quantum space-time foam (D-foam) may induce oscillations and mixing among flavored particles. As a result, rather than the mass-eigenstate vacuum, the correct ground state to describe the underlying dynamics is the flavor vacuum, proposed some time ago by Blasone and Vitiello as a description of quantum field theories with mixing. At the microscopic level, the breaking of target-space supersymmetry is induced in our space-time foam model by the relative transverse motion of brane defects. Motivated by these results, we show that the flavor vacuum, introduced through an inequivalent representation of the canonical (anti-) commutation relations, provides a vehicle for the breaking of supersymmetry at a low-energy effective field-theory level; on considering the flavor-vacuum expectation value of the energy-momentum tensor and comparing with the form of a perfect relativistic fluid, it is found that the bosonic sector contributes as dark energy while the fermion contribution is like dust. This indicates a strong and novel breaking of supersymmetry, of a nonperturbative nature, which may characterize the low-energy field theory of certain quantum-gravity models.

Microbial Enrichment from Six Hydraulic Fracturing Fluids and Biogeochemical Characteristics of Flowback Waters in Oklahoma Shale Formations

NASA Astrophysics Data System (ADS)

Krzmarzick, M. J.; McCutchan, A.; Carroll, J.; Lozano, T.

2017-12-01

Hydraulic fracturing of oil and gas formations has revolutionized the industry, but little is known regarding the interactions of the microbiology in formations and the hydraulic fracturing chemicals used. In the first part of this study, six representative hydraulic fracturing fluids were incubated in bench scale microcosms with surface soils over six months at 1× concentrations used in the field. These fluids differed greatly in terms of biocide, surfactants, corrosion inhibitors and crosslinking agents (if any). The changes in microbial communities were measured by Illumina 16S rRNA gene analysis and quantitative-PCR. As a whole, the microbial communities enriched were significantly varied between fluids, with the magnitude of the difference tightly linked to the total organic carbon of each fluid. Most enriched bacteria heavily grew within just the first couple of weeks, and belonged to genera well-linked to xenobiotic degradation, such as Azospirillum, Ralstonia, and Comamonas. This, combined with bulk parameters such as chemical oxygen demand of the water, indicates that a significant fraction of these fluids are readily degradable, though individual chemicals were not monitored for recalcitrance. In the second component of this work, the flowback waters from sixteen newly completed wells in south-central Oklahoma were monitored over two months for compositions of boron, dissolved solids, BTEX, chloride, and their microbial communities. As expected, dissolved solids increased over time as the flowback waters became more characteristic of the formation waters. In these wells, boron, a carefully measured component of the fracturing fluid for cross-linking applications, was either stable or increased over time. The microbial community characteristics are pending but will be compared between formations, to the chemical data, and to the results in the bench-top degradation study.

Hydraulic fracturing to enhance the remediation of DNAPL in low permeability soils

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murdoch, L.; Slack, B.

1996-08-01

Meager rates of fluid flow are a major obstacle to in situ remediation of low permeability soils. This paper describes methods designed to avoid that obstacle by creating fractures and filling them with sand to increase well discharge and change paths of fluid flow in soil. Gently dipping fractures 10 m in maximum dimension and 1 to 2 cm thick can be created in some contaminated soils at depths of a few in or greater. Hydraulic fractures can also be used to create electrically conductive layers or to deliver granules of chemically or biologically active compounds that will degrade contaminantsmore » in place. Benefits of applying hydraulic fractures to DNAPL recovery include rates of fluid recovery, enhancing upward gradients to improve hydrodynamic stabilization, forming flat-lying reactive curtains to intersect compounds moving downward, or improving the performance of electrokinetics intended to recover compounds dissolved in water. 30 refs., 7 figs., 1 tab.« less

Lagrangian formulation for penny-shaped and Perkins-Kern geometry models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, W.S.

1989-09-01

This paper discusses basic theories for vertical penny-shaped and Perkins-Kern (PK) geometry models developed with a Lagrangian formulation combined with a virtual-work analysis. The Lagrangian formulation yields a pair of nonlinear equations in R/sub f/ or L/sub f/ and b/sub f/, the fracture radius or length and half-width. By introduction of a virtual-work analysis, a simple equation is obtained that can be solved numerically. This equation is written in a form that can be used to determine fracture geometry when the fluid-loss coefficient of the fracturing fluid is known. Also, this equation, coupled with a material-balance equation after shut-in, canmore » be used to analyze pressure-decline data after shut-in to determine the effective fluid-loss coefficient and fracture geometry.« less

Simulating Hydraulic Fracturing: Failure in soft versus hard rocks

NASA Astrophysics Data System (ADS)

Aleksans, J.; Koehn, D.; Toussaint, R.

2017-12-01

In this contribution we discuss the dynamic development of hydraulic fractures, their evolution and the resulting seismicity during fluid injection in a coupled numerical model. The model describes coupling between a solid that can fracture dynamically and a compressible fluid that can push back at the rock and open fractures. With a series of numerical simulations we show how the fracture pattern and seismicity change depending on changes in depth, injection rate, Young's Modulus and breaking strength. Our simulations indicate that the Young's Modulus has the largest influence on the fracture dynamics and also the related seismicity. Simulations of rocks with a Young's modulus smaller than 10 GPa show dominant mode I failure and a growth of fracture aperture with a decrease in Young's modulus. Simulations of rocks with a higher Young's modulus than 10 GPa show fractures with a constant aperture and fracture growth that is mainly governed by a growth in crack length and an increasing amount of mode II failure. We propose that two distinct failure regimes are observed in the simulations, above 10 GPa rocks break with a constant critical stress intensity factor whereas below 10 GPa they break reaching a critical cohesion, i.e. a critical tensile strength. These results are very important for the prediction of fracture dynamics and seismicity during fluid injection, especially since we see a transition from one failure regime to another at around 10 GPa, a Young's modulus that lies in the middle of possible values for natural shale rocks.

Translation by anisotropic peeling or fracturing in elastic media

NASA Astrophysics Data System (ADS)

Zheng, Zhong; Lister, John; Neufeld, Jerome

2017-11-01

The influence of rock anisotropy on the direction of hydraulic fracturing is an important open question. Two canonical systems have been proposed to investigate the fundamental aspects of such fluid-structure interaction problems: (i) Fluid injection and fracturing into an infinite elastic matrix (e.g., solid gelatin) and (ii) Fluid invasion and peeling beneath a deforming elastic sheet (e.g., bending plate). We investigate the second system and impose a non-uniform prewetting film thickness beneath the elastic sheet. We notice that while the bulk of the elastic sheet retains the static blister shape, a non-uniform prewetting film thickness can cause a horizontal translation of the blister. In particular, for a step jump in prewetting film thickness, asymptotic analysis indicates that, under constant fluid injection, the horizontal translation follows a t 7 / 17 time dependence in cartesian coordinates, and the prefactor of power-law translation depends on the ratio of the distinct prewetting film thicknesses on either side. We also provide numerical and experimental evidence demonstrating anisotropic blister evolution. This can be thought of as a model system for fluid-driven fracturing where the non-uniform prewetting film thickness mimics heterogeneity in material toughness.

Fluid, solid and fluid-structure interaction simulations on patient-based abdominal aortic aneurysm models.

PubMed

Kelly, Sinead; O'Rourke, Malachy

2012-04-01

This article describes the use of fluid, solid and fluid-structure interaction simulations on three patient-based abdominal aortic aneurysm geometries. All simulations were carried out using OpenFOAM, which uses the finite volume method to solve both fluid and solid equations. Initially a fluid-only simulation was carried out on a single patient-based geometry and results from this simulation were compared with experimental results. There was good qualitative and quantitative agreement between the experimental and numerical results, suggesting that OpenFOAM is capable of predicting the main features of unsteady flow through a complex patient-based abdominal aortic aneurysm geometry. The intraluminal thrombus and arterial wall were then included, and solid stress and fluid-structure interaction simulations were performed on this, and two other patient-based abdominal aortic aneurysm geometries. It was found that the solid stress simulations resulted in an under-estimation of the maximum stress by up to 5.9% when compared with the fluid-structure interaction simulations. In the fluid-structure interaction simulations, flow induced pressure within the aneurysm was found to be up to 4.8% higher than the value of peak systolic pressure imposed in the solid stress simulations, which is likely to be the cause of the variation in the stress results. In comparing the results from the initial fluid-only simulation with results from the fluid-structure interaction simulation on the same patient, it was found that wall shear stress values varied by up to 35% between the two simulation methods. It was concluded that solid stress simulations are adequate to predict the maximum stress in an aneurysm wall, while fluid-structure interaction simulations should be performed if accurate prediction of the fluid wall shear stress is necessary. Therefore, the decision to perform fluid-structure interaction simulations should be based on the particular variables of interest in a given study.

Characterization of seismic properties across scales: from the laboratory- to the field scale

NASA Astrophysics Data System (ADS)

Grab, Melchior; Quintal, Beatriz; Caspari, Eva; Maurer, Hansruedi; Greenhalgh, Stewart

2016-04-01

When exploring geothermal systems, the main interest is on factors controlling the efficiency of the heat exchanger. This includes the energy state of the pore fluids and the presence of permeable structures building part of the fluid transport system. Seismic methods are amongst the most common exploration techniques to image the deep subsurface in order to evaluate such a geothermal heat exchanger. They make use of the fact that a seismic wave caries information on the properties of the rocks in the subsurface through which it passes. This enables the derivation of the stiffness and the density of the host rock from the seismic velocities. Moreover, it is well-known that the seismic waveforms are modulated while propagating trough the subsurface by visco-elastic effects due to wave induced fluid flow, hence, delivering information about the fluids in the rock's pore space. To constrain the interpretation of seismic data, that is, to link seismic properties with the fluid state and host rock permeability, it is common practice to measure the rock properties of small rock specimens in the laboratory under in-situ conditions. However, in magmatic geothermal systems or in systems situated in the crystalline basement, the host rock is often highly impermeable and fluid transport predominately takes place in fracture networks, consisting of fractures larger than the rock samples investigated in the laboratory. Therefore, laboratory experiments only provide the properties of relatively intact rock and an up-scaling procedure is required to characterize the seismic properties of large rock volumes containing fractures and fracture networks and to study the effects of fluids in such fractured rock. We present a technique to parameterize fractured rock volumes as typically encountered in Icelandic magmatic geothermal systems, by combining laboratory experiments with effective medium calculations. The resulting models can be used to calculate the frequency-dependent bulk modulus K(ω) and shear modulus G(ω), from which the P- and S-wave velocities V P(ω) and V S(ω) and the quality factors QP(ω) and QS(ω) of fluid saturated fractured rock volumes can be estimated. These volumes are much larger and contain more complex structures than the rock samples investigated in the laboratory. Thus, the derived quantities describe the elastic and anelastic (energy loss due to wave induced fluid flow) short-term deformation induced by seismic waves at scales that are relevant for field-scale seismic exploration projects.

Micromechanical Aspects of Hydraulic Fracturing Processes

NASA Astrophysics Data System (ADS)

Galindo-torres, S. A.; Behraftar, S.; Scheuermann, A.; Li, L.; Williams, D.

2014-12-01

A micromechanical model is developed to simulate the hydraulic fracturing process. The model comprises two key components. Firstly, the solid matrix, assumed as a rock mass with pre-fabricated cracks, is represented by an array of bonded particles simulated by the Discrete Element Model (DEM)[1]. The interaction is ruled by the spheropolyhedra method, which was introduced by the authors previously and has been shown to realistically represent many of the features found in fracturing and communition processes. The second component is the fluid, which is modelled by the Lattice Boltzmann Method (LBM). It was recently coupled with the spheropolyhedra by the authors and validated. An advantage of this coupled LBM-DEM model is the control of many of the parameters of the fracturing fluid, such as its viscosity and the injection rate. To the best of the authors' knowledge this is the first application of such a coupled scheme for studying hydraulic fracturing[2]. In this first implementation, results are presented for a two-dimensional situation. Fig. 1 shows one snapshot of the LBM-DEM coupled simulation for the hydraulic fracturing where the elements with broken bonds can be identified and the fracture geometry quantified. The simulation involves a variation of the underground stress, particularly the difference between the two principal components of the stress tensor, to explore the effect on the fracture path. A second study focuses on the fluid viscosity to examine the effect of the time scales of different injection plans on the fracture geometry. The developed tool and the presented results have important implications for future studies of the hydraulic fracturing process and technology. references 1. Galindo-Torres, S.A., et al., Breaking processes in three-dimensional bonded granular materials with general shapes. Computer Physics Communications, 2012. 183(2): p. 266-277. 2. Galindo-Torres, S.A., A coupled Discrete Element Lattice Boltzmann Method for the simulation of fluid-solid interaction with particles of general shapes. Computer Methods in Applied Mechanics and Engineering, 2013. 265(0): p. 107-119.

Simulation of water flow in fractured porous medium by using discretized virtual internal bond

NASA Astrophysics Data System (ADS)

Peng, Shujun; Zhang, Zhennan; Li, Chunfang; He, Guofu; Miao, Guoqing

2017-12-01

The discretized virtual internal bond (DVIB) is adopted to simulate the water flow in fractured porous medium. The intact porous medium is permeable because it contains numerous micro cracks and pores. These micro discontinuities construct a fluid channel network. The representative volume of this fluid channel network is modeled as a lattice bond cell with finite number of bonds in statistical sense. Each bond serves as a fluid channel. In fractured porous medium, many bond cells are cut by macro fractures. The conductivity of the fracture facet in a bond cell is taken over by the bonds parallel to the flow direction. The equivalent permeability and volumetric storage coefficient of a micro bond are calibrated based on the ideal bond cell conception, which makes it unnecessary to consider the detailed geometry of a specific element. Such parameter calibration method is flexible and applicable to any type of element. The accuracy check results suggest this method has a satisfying accuracy in both the steady and transient flow simulation. To simulate the massive fractures in rockmass, the bond cells intersected by fracture are assigned aperture values, which are assumed random numbers following a certain distribution law. By this method, any number of fractures can be implicitly incorporated into the background mesh, avoiding the setup of fracture element and mesh modification. The fracture aperture heterogeneity is well represented by this means. The simulation examples suggest that the present method is a feasible, simple and efficient approach to the numerical simulation of water flow in fractured porous medium.

Fluid Merging Viscosity Measurement (FMVM)

NASA Technical Reports Server (NTRS)

2004-01-01

Astronaut Mike Fincke places droplets of honey onto the strings for the Fluid Merging Viscosity Measurement (FMVM) investigation onboard the International Space Station (ISS). The FMVM experiment measures the time it takes for two individual highly viscous fluid droplets to coalesce or merge into one droplet. Different fluids and droplet size combinations were tested in the series of experiments. By using the microgravity environment, researchers can measure the viscosity or 'thickness' of fluids without the influence of containers and gravity using this new technique. Understanding viscosity could help scientists understand industrially important materials such as paints, emulsions, polymer melts and even foams used to produce pharmaceutical, food, and cosmetic products.

Effect of matrix elasticity on the continuous foaming of food models.

PubMed

Narchi, I; Vial, Ch; Djelveh, G

2008-12-01

The aim is to understand the effect of matrix elasticity on continuous foaming using food models based on glucose syrup. This was modified by adding polyacrylamide (PAA) with 2% whey protein isolate (WPI) or Tween 80 as foaming agents. Foaming was conducted in a stirred column. Rotation speed N and gas-to-liquid flow ratio (G/L) were varied. Overrun, average bubble size d (32), texture and stability were measured using densimetry, image analysis, and rheometry, respectively. Experimental results showed that 0.01% PAA did not modify the viscosity of 2% WPI models, but conferred low elastic behavior. PAA (0.05%) doubled matrix viscosity and drastically increased elasticity. The increase of elasticity became slower for further PAA addition. Foaming experiments demonstrated that theoretical overrun could not be achieved for inelastic WPI models in two cases: for high viscosity and low N, as dispersion effectiveness was reduced; for high G/L and N because of enhanced coalescence. Matrix elasticity was shown to increase overrun at constant viscosity for high G/L by enhancing interface stabilization. However, in elastic models, gas dispersion was more difficult and d (32) was higher than in inelastic fluids of similar viscosity. Finally, when the limiting step was dispersion, foaming was shown to be negatively affected by matrix elasticity.

Fractured-aquifer hydrogeology from geophysical logs: Brunswick group and Lockatong Formation, Pennsylvania

USGS Publications Warehouse

Morin, Roger H.; Senior, Lisa A.; Decker, Edward R.

2000-01-01

The Brunswick Group and the underlying Lockatong Formation are composed of lithified Mesozoic sediments that constitute part of the Newark Basin in southeastern Pennsylvania. These fractured rocks form an important regional aquifer that consists of gradational sequences of shale, siltstone, and sandstone, with fluid transport occurring primarily in fractures. An extensive suite of geophysical logs was obtained in seven wells located at the borough of Lansdale, Pennsylvania, in order to better characterize the areal hydrogeologic system and provide guidelines for the refinement of numerical ground water models. Six of the seven wells are approximately 120 m deep and the seventh extends to a depth of 335 m. Temperature, fluid conductivity, and flowmeter logs are used to locate zones of fluid exchange and to quantify transmissivities. Electrical resistivity and natural gamma logs together yield detailed stratigraphic information, and digital acoustic televiewer data provide magnetically oriented images of the borehole wall from which almost 900 fractures are identified.Analyses of the geophysical data indicate that the aquifer penetrated by the deep well can be separated into two distinct structural domains, which may, in turn, reflect different mechanical responses to basin extension by different sedimentary units:1. In the shallow zone (above 125 m), the dominant fracture population consists of gently dipping bedding plane partings that strike N46°E and dip to the northwest at about 11 degrees. Fluid flow is concentrated in the upper 80 m along these subhorizontal fractures, with transmissivities rapidly diminishing in magnitude with depth.2. The zone below 125 m marks the appearance of numerous high-angle fractures that are orthogonal to the bedding planes, striking parallel but dipping steeply southeast at 77 degrees.This secondary set of fractures is associated with a fairly thick (approximately 60 m) high-resistivity, low-transmissivity sandstone unit that is abruptly terminated by a thin shale bed at a depth of 190 m. This lower contact effectively delineates the aquifer's vertical extent at this location because no detectable evidence of ground water movement is found below it. Thus, fluid flow is controlled by fractures, but fracture type and orientation are related to lithology. Finally, a transient thermal-conduction model is successfully applied to simulate observed temperature logs, thereby confirming the effects of ground-surface warming that occurred in the area as a result of urbanization at the turn of the century. The systematic warming of the upper 120 m has increased the transmissivity of this aquifer by almost 10%, simply due to changes in fluid viscosity and density.

Assessing Past Fracture Connectivity in Geothermal Reservoirs Using Clumped Isotopes: Proof of Concept in the Blue Mountain Geothermal Field, Nevada USA

NASA Astrophysics Data System (ADS)

Huntington, K. W.; Sumner, K. K.; Camp, E. R.; Cladouhos, T. T.; Uddenberg, M.; Swyer, M.; Garrison, G. H.

2015-12-01

Subsurface fluid flow is strongly influenced by faults and fractures, yet the transmissivity of faults and fractures changes through time due to deformation and cement precipitation, making flow paths difficult to predict. Here we assess past fracture connectivity in an active hydrothermal system in the Basin and Range, Nevada, USA, using clumped isotope geochemistry and cold cathodoluminescence (CL) analysis of fracture filling cements from the Blue Mountain geothermal field. Calcite cements were sampled from drill cuttings and two cores at varying distances from faults. CL microscopy of some of the cements shows banding parallel to the fracture walls as well as brecciation, indicating that the cements record variations in the composition and source of fluids that moved through the fractures as they opened episodically. CL microscopy, δ13C and δ18O values were used to screen homogeneous samples for clumped isotope analysis. Clumped isotope thermometry of most samples indicates paleofluid temperatures of around 150°C, with several wells peaking at above 200°C. We suggest that the consistency of these temperatures is related to upwelling of fluids in the convective hydrothermal system, and interpret the similarity of the clumped isotope temperatures to modern geothermal fluid temperatures of ~160-180°C as evidence that average reservoir temperatures have changed little since precipitation of the calcite cements. In contrast, two samples, one of which was associated with fault gauge observed in drill logs, record significantly cooler temperatures of 19 and 73°C and anomalous δ13C and δ18Owater values, which point to fault-controlled pathways for downwelling meteoric fluid. Finally, we interpret correspondence of paleofluid temperatures and δ18Owater values constrained by clumped isotope thermometry of calcite from different wells to suggest past connectivity of fractures among wells within the geothermal field. Results show the ability of clumped isotope geothermometry to assess fracture connectivity and geothermal reservoir characteristics in the past—with the potential to help optimize resource production and injection programs and better understand structural controls on mass and heat transfer in the subsurface.

Quartz c-axis orientation patterns in fracture cement as a measure of fracture opening rate and a validation tool for fracture pattern models

DOE PAGES

Ukar, Estibalitz; Laubach, Stephen E.; Marrett, Randall

2016-03-09

Here, we evaluate a published model for crystal growth patterns in quartz cement in sandstone fractures by comparing crystal fracture-spanning predictions to quartz c-axis orientation distributions measured by electron backscatter diffraction (EBSD) of spanning quartz deposits. Samples from eight subvertical opening-mode fractures in four sandstone formations, the Jurassic– Cretaceous Nikanassin Formation, northwestern Alberta Foothills (Canada), Cretaceous Mesaverde Group (USA; Cozzette Sandstone Member of the Iles Formation), Piceance Basin, Colorado (USA), and upper Jurassic–lower Cretaceous Cotton Valley Group (Taylor sandstone) and overlying Travis Peak Formation, east Texas, have similar quartzose composition and grain size but contain fractures with different temperature historiesmore » and opening rates based on fluid inclusion assemblages and burial history. Spherical statistical analysis shows that, in agreement with model predictions, bridging crystals have a preferred orientation with c-axis orientations at a high angle to fracture walls. The second form of validation is for spanning potential that depends on the size of cut substrate grains. Using measured cut substrate grain sizes and c-axis orientations of spanning bridges, we calculated the required orientation for the smallest cut grain to span the maximum gap size and the required orientation of the crystal with the least spanning potential to form overgrowths that span across maximum measured gap sizes. We find that within a 10° error all spanning crystals conform to model predictions. Using crystals with the lowest spanning potential based on crystallographic orientation (c-axis parallel to fracture wall) and a temperature range for fracture opening measured from fluid inclusion assemblages, we calculate maximum fracture opening rates that allow crystals to span. These rates are comparable to those derived independently from fracture temperature histories based on burial history and multiple sequential fluid inclusion assemblages. Results support the R. Lander and S. Laubach model, which predicts that for quartz deposited synchronously with fracture opening, spanning potential, or likelihood of quartz deposits that are thick enough to span between fracture walls, depends on temperature history, fracture opening rate, size of opening increments, and size, mineralogy, and crystallographic orientation of substrates in the fracture wall (transected grains). Results suggest that EBSD maps, which can be more rapidly acquired than measurement of tens to hundreds of fluid inclusion assemblages, can provide a useful measure of relative opening rates within populations of quartz-filled fractures formed under sedimentary basin conditions. Such data are useful for evaluating fracture pattern development models.« less

Quartz c-axis orientation patterns in fracture cement as a measure of fracture opening rate and a validation tool for fracture pattern models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ukar, Estibalitz; Laubach, Stephen E.; Marrett, Randall

Here, we evaluate a published model for crystal growth patterns in quartz cement in sandstone fractures by comparing crystal fracture-spanning predictions to quartz c-axis orientation distributions measured by electron backscatter diffraction (EBSD) of spanning quartz deposits. Samples from eight subvertical opening-mode fractures in four sandstone formations, the Jurassic– Cretaceous Nikanassin Formation, northwestern Alberta Foothills (Canada), Cretaceous Mesaverde Group (USA; Cozzette Sandstone Member of the Iles Formation), Piceance Basin, Colorado (USA), and upper Jurassic–lower Cretaceous Cotton Valley Group (Taylor sandstone) and overlying Travis Peak Formation, east Texas, have similar quartzose composition and grain size but contain fractures with different temperature historiesmore » and opening rates based on fluid inclusion assemblages and burial history. Spherical statistical analysis shows that, in agreement with model predictions, bridging crystals have a preferred orientation with c-axis orientations at a high angle to fracture walls. The second form of validation is for spanning potential that depends on the size of cut substrate grains. Using measured cut substrate grain sizes and c-axis orientations of spanning bridges, we calculated the required orientation for the smallest cut grain to span the maximum gap size and the required orientation of the crystal with the least spanning potential to form overgrowths that span across maximum measured gap sizes. We find that within a 10° error all spanning crystals conform to model predictions. Using crystals with the lowest spanning potential based on crystallographic orientation (c-axis parallel to fracture wall) and a temperature range for fracture opening measured from fluid inclusion assemblages, we calculate maximum fracture opening rates that allow crystals to span. These rates are comparable to those derived independently from fracture temperature histories based on burial history and multiple sequential fluid inclusion assemblages. Results support the R. Lander and S. Laubach model, which predicts that for quartz deposited synchronously with fracture opening, spanning potential, or likelihood of quartz deposits that are thick enough to span between fracture walls, depends on temperature history, fracture opening rate, size of opening increments, and size, mineralogy, and crystallographic orientation of substrates in the fracture wall (transected grains). Results suggest that EBSD maps, which can be more rapidly acquired than measurement of tens to hundreds of fluid inclusion assemblages, can provide a useful measure of relative opening rates within populations of quartz-filled fractures formed under sedimentary basin conditions. Such data are useful for evaluating fracture pattern development models.« less

Tracer Methods for Characterizing Fracture Creation in Engineered Geothermal Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rose, Peter; Harris, Joel

2014-05-08

The aim of this proposal is to develop, through novel high-temperature-tracing approaches, three technologies for characterizing fracture creation within Engineered Geothermal Systems (EGS). The objective of a first task is to identify, develop and demonstrate adsorbing tracers for characterizing interwell reservoir-rock surface areas and fracture spacing. The objective of a second task is to develop and demonstrate a methodology for measuring fracture surface areas adjacent to single wells. The objective of a third task is to design, fabricate and test an instrument that makes use of tracers for measuring fluid flow between newly created fractures and wellbores. In one methodmore » of deployment, it will be used to identify qualitatively which fractures were activated during a hydraulic stimulation experiment. In a second method of deployment, it will serve to measure quantitatively the rate of fluid flowing from one or more activated fracture during a production test following a hydraulic stimulation.« less

Fracture Development within the Karaha-Telaga Bodas Geothermal Field, Indonesia

USGS Publications Warehouse

Nemcok, M.; Moore, J.N.; Allis, R.; McCulloch, J.

2002-01-01

Karaha-Telaga Bodas is a partially vapor-dominated geothermal system located in an active volcano in western Java. More than 2 dozen geothermal wells have been drilled to depths of 3 km. Detailed paragenetic and fluid-inclusion studies have defined liquid-dominated, transitional and vapor-dominated stages in the evolution of this system. The liquid-dominated stage was initiated by shallow magma intrusion into the base of the volcanic cone. Lava and pyroclastic flows capped a geothermal system. The uppermost andesite flows were only weakly fractured due to the insulating effect of the intervening altered pyroclastics, which absorbed the deformation. Shear and tensile fractures were filled with carbonates at shallow depths and by quartz, epidote and actinolite at depths and temperatures over 1km and 300??C. The system underwent numerous local cycles of overpressuring, which are marked by subhorizontal tensile fractures, anastomosing tensile fractures and implosion breccias. The development of the liquid system was interrupted by a catastrophic drop in fluid pressures. As the fluids boiled in response to this pressure drop, chalcedony and quartz were deposited in fractures having the largest apertures and steep dips. The orientations of these fractures indicate that the escaping overpressured fluids used the shortest possible paths to the surface. Vapor-dominated conditions were initiated within a vertical chimney over the still hot intrusion. As pressures declined these conditions spread outward. Downward migration of the chimney occurred as the intrusion cooled and the brittle-ductile transition migrated to greater depths. Condensate that formed at the top of the vapor-dominated zone percolated downward and lowsalinity meteoric water entered the marginal parts of the system. Calcite, anhydrite, and fluorite precipitated in fractures upon heating. A progressive sealing of the fractures occurred, resulting in the downward migration of the cap rock. In response to decreasing pore pressures in the expanding vapor zone, the fracture system within the vapor-dominated reservoir progressively collapsed, leaving only residual permeability, with apertures supported by asperities or propping breccia. In places, the fractures have completely collapsed where normal stresses acting on the fracture walls exceeded the compressive strength of the wall rock.

Fluid circulations in the depths of accretionary prism: the record of quartz from the Shimanto Belt, Japan

NASA Astrophysics Data System (ADS)

Raimbourg, Hugues; Vacelet, Maxime; Ramboz, Claire; Famin, Vincent; Augier, Romain; Palazzin, Giulia

2014-05-01

Fluids present in the depths of subduction zones play a major role on seismogenesis, although fluid circulations paths and physico-chemical conditions are still largely unknown. Two main reservoirs of water, either in the pores of sediments or bound to hydrous minerals, release large amounts of water in the relatively shallow and deep domains of subduction zones, respectively. The usual model of circulation assumes then a bottom-up circulation driven by fluid pressure gradients. This study aims at reassessing this model, using the record of rocks from a paleo-accretionary prism, the Shimanto Belt in Japan. These rocks, buried to 5kbars and 300° C (Toriumi and Teruya, Modern Geology, 1988), were affected by pervasive fracturing throughout their history, from burial to exhumation. The quartz filling these fractures and the fluid inclusions that it contains keep the track of the fluid associated with the rock evolution. Using a combined approach of microstructural observations by optical microscopy and cathodoluminescence (CL), and chemical characterization by electron and ion microprobe as well as microthermometry, we show that there are actually two distinct fluids that have cyclically wetted the rock at depth. The first one is an 'external' fluid penetrating through macroscopic fractures and precipitating a quartz blue in CL. In contrast, a 'local' fluid attended the formation of quartz brown in CL, precipitating in microfractures or associated with ductile recrystallization. The two fluids are also chemically distinct: Both have a salinity close to seawater, but the local fluid is fresher than the external one. In addition, the external fluid is richer in aluminum than the local one. Finally, the external fluid is very slightly depleted in δ18O, although the difference is probably not significant and the first-order isotopic signal is a buffering by host rock. Our interpretation of microstructures and chemical signatures is that the external fluid is seawater, penetrating to accretionary prism depths during transient phases of large-scale fracturing and fluid circulation. Macroscale fractures then close, permeability drops, and the fluid is progressively reequilibrated at depth with water produced in-situ by metamorphic reactions. The general scheme is therefore a top-down circulation, contrasting with the usually proposed bottom-up flux. We finally discuss geodynamical scenarios, such as during the postseismic phase or in association with thermal anomalies, where such a counter-intuitive top-down flux of water could prevail in subduction zones.

3D Simulation of Multiple Simultaneous Hydraulic Fractures with Different Initial Lengths in Rock

NASA Astrophysics Data System (ADS)

Tang, X.; Rayudu, N. M.; Singh, G.

2017-12-01

Hydraulic fracturing is widely used technique for extracting shale gas. During this process, fractures with various initial lengths are induced in rock mass with hydraulic pressure. Understanding the mechanism of propagation and interaction between these induced hydraulic cracks is critical for optimizing the fracking process. In this work, numerical results are presented for investigating the effect of in-situ parameters and fluid properties on growth and interaction of multi simultaneous hydraulic fractures. A fully coupled 3D fracture simulator, TOUGH- GFEM is used for simulating the effect of different vital parameters, including in-situ stress, initial fracture length, fracture spacing, fluid viscosity and flow rate on induced hydraulic fractures growth. This TOUGH-GFEM simulator is based on 3D finite volume method (FVM) and partition of unity element method (PUM). Displacement correlation method (DCM) is used for calculating multi - mode (Mode I, II, III) stress intensity factors. Maximum principal stress criteria is used for crack propagation. Key words: hydraulic fracturing, TOUGH, partition of unity element method , displacement correlation method, 3D fracturing simulator

Water Resources Management for Shale Energy Development

NASA Astrophysics Data System (ADS)

Yoxtheimer, D.

2015-12-01

The increase in the exploration and extraction of hydrocarbons, especially natural gas, from shale formations has been facilitated by advents in horizontal drilling and hydraulic fracturing technologies. Shale energy resources are very promising as an abundant energy source, though environmental challenges exist with their development, including potential adverse impacts to water quality. The well drilling and construction process itself has the potential to impact groundwater quality, however if proper protocols are followed and well integrity is established then impacts such as methane migration or drilling fluids releases can be minimized. Once a shale well has been drilled and hydraulically fractured, approximately 10-50% of the volume of injected fluids (flowback fluids) may flow out of the well initially with continued generation of fluids (produced fluids) throughout the well's productive life. Produced fluid TDS concentrations often exceed 200,000 mg/L, with elevated levels of strontium (Sr), bromide (Br), sodium (Na), calcium (Ca), barium (Ba), chloride (Cl), radionuclides originating from the shale formation as well as fracturing additives. Storing, managing and properly disposisng of these fluids is critical to ensure water resources are not impacted by unintended releases. The most recent data in Pennsylvania suggests an estimated 85% of the produced fluids were being recycled for hydraulic fracturing operations, while many other states reuse less than 50% of these fluids and rely moreso on underground injection wells for disposal. Over the last few years there has been a shift to reuse more produced fluids during well fracturing operations in shale plays around the U.S., which has a combination of economic, regulatory, environmental, and technological drivers. The reuse of water is cost-competitive with sourcing of fresh water and disposal of flowback, especially when considering the costs of advanced treatment to or disposal well injection and lessens the use of fresh water and disposal needs thus is a major innovation for the industry. Proper water resource managment techniques from the begining of drilling through production are critical to ensure the energy necessary for society is produced while also protecting the environment.

Simulating Fragmentation and Fluid-Induced Fracture in Disordered Media Using Random Finite-Element Meshes

DOE PAGES

Bishop, Joseph E.; Martinez, Mario J.; Newell, Pania

2016-11-08

Fracture and fragmentation are extremely nonlinear multiscale processes in which microscale damage mechanisms emerge at the macroscale as new fracture surfaces. Numerous numerical methods have been developed for simulating fracture initiation, propagation, and coalescence. In this paper, we present a computational approach for modeling pervasive fracture in quasi-brittle materials based on random close-packed Voronoi tessellations. Each Voronoi cell is formulated as a polyhedral finite element containing an arbitrary number of vertices and faces. Fracture surfaces are allowed to nucleate only at the intercell faces. Cohesive softening tractions are applied to new fracture surfaces in order to model the energy dissipatedmore » during fracture growth. The randomly seeded Voronoi cells provide a regularized discrete random network for representing fracture surfaces. The potential crack paths within the random network are viewed as instances of realizable crack paths within the continuum material. Mesh convergence of fracture simulations is viewed in a weak, or distributional, sense. The explicit facet representation of fractures within this approach is advantageous for modeling contact on new fracture surfaces and fluid flow within the evolving fracture network. Finally, applications of interest include fracture and fragmentation in quasi-brittle materials and geomechanical applications such as hydraulic fracturing, engineered geothermal systems, compressed-air energy storage, and carbon sequestration.« less

Simulating Fragmentation and Fluid-Induced Fracture in Disordered Media Using Random Finite-Element Meshes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bishop, Joseph E.; Martinez, Mario J.; Newell, Pania

Fracture and fragmentation are extremely nonlinear multiscale processes in which microscale damage mechanisms emerge at the macroscale as new fracture surfaces. Numerous numerical methods have been developed for simulating fracture initiation, propagation, and coalescence. In this paper, we present a computational approach for modeling pervasive fracture in quasi-brittle materials based on random close-packed Voronoi tessellations. Each Voronoi cell is formulated as a polyhedral finite element containing an arbitrary number of vertices and faces. Fracture surfaces are allowed to nucleate only at the intercell faces. Cohesive softening tractions are applied to new fracture surfaces in order to model the energy dissipatedmore » during fracture growth. The randomly seeded Voronoi cells provide a regularized discrete random network for representing fracture surfaces. The potential crack paths within the random network are viewed as instances of realizable crack paths within the continuum material. Mesh convergence of fracture simulations is viewed in a weak, or distributional, sense. The explicit facet representation of fractures within this approach is advantageous for modeling contact on new fracture surfaces and fluid flow within the evolving fracture network. Finally, applications of interest include fracture and fragmentation in quasi-brittle materials and geomechanical applications such as hydraulic fracturing, engineered geothermal systems, compressed-air energy storage, and carbon sequestration.« less

A Temporal and Spatial Analysis of Wave-Generated Foam Patterns in the Surf Zone

DTIC Science & Technology

2017-01-10

region, rectange B depicts the gap region, rectangle C is the plunging breaker, circle D represents a foam hole, rectangle E depict a top box...structures: The hidden skeleton of fluid flows . Phys. Today, 66, 41–47. 35 V. CONCLUSION Unique surf zone imagery, acquired from a UAV at Sand City...MacMahan, J. H., E . B . Thornton, T. P. Stanton, and A. J. H. M. Reniers, 2005: RIPEX: Observations of a rip current system. Mar. Geol., 218, 113–134

[Evaluation of fetal lung maturity using a modified lecithin-sphingomyelin determination and Clements' foam test].

PubMed

Neumann, G; Gartzke, J; Faber, G

1978-01-01

The modified thin layer chromatographic method for the determination of the phospholipids lecithin and sphingomyelin from amniotic fluid is useful in estimating fetal pulmonary maturity. The foam test of Clements is a simple rapid method for screening of suspicious cases of pregnancies at risk and of great value as bed side test even performing by the doctor. In comparing Clements-Test with thin layer chromatographic for L/S-Ratio determination we found a good correlation of 81,8% of all cases.

Synthesis of α-Fe2O3 and Fe-Mn Oxide Foams with Highly Tunable Magnetic Properties by the Replication Method from Polyurethane Templates

PubMed Central

Feng, Yuping; Fornell, Jordina; Zhang, Huiyan; Solsona, Pau; Barό, Maria Dolors; Suriñach, Santiago; Sort, Jordi

2018-01-01

Open cell foams consisting of Fe and Fe-Mn oxides are prepared from metallic Fe and Mn powder precursors by the replication method using porous polyurethane (PU) templates. First, reticulated PU templates are coated by slurry impregnation. The templates are then thermally removed at 260 °C and the debinded powders are sintered at 1000 °C under N2 atmosphere. The morphology, structure, and magnetic properties are studied by scanning electron microscopy, X-ray diffraction and vibrating sample magnetometry, respectively. The obtained Fe and Fe-Mn oxide foams possess both high surface area and homogeneous open-cell structure. Hematite (α-Fe2O3) foams are obtained from the metallic iron slurry independently of the N2 flow. In contrast, the microstructure of the FeMn-based oxide foams can be tailored by adjusting the N2 flow. While the main phases for a N2 flow rate of 180 L/h are α-Fe2O3 and FeMnO3, the predominant phase for high N2 flow rates (e.g., 650 L/h) is Fe2MnO4. Accordingly, a linear magnetization versus field behavior is observed for the hematite foams, while clear hysteresis loops are obtained for the Fe2MnO4 foams. Actually, the saturation magnetization of the foams containing Mn increases from 5 emu/g to 52 emu/g when the N2 flow rate (i.e., the amount of Fe2MnO4) is increased. The obtained foams are appealing for a wide range of applications, such as electromagnetic absorbers, catalysts supports, thermal and acoustic insulation systems or wirelessly magnetically-guided porous objects in fluids. PMID:29439450

Synthesis of α-Fe₂O₃ and Fe-Mn Oxide Foams with Highly Tunable Magnetic Properties by the Replication Method from Polyurethane Templates.

PubMed

Feng, Yuping; Fornell, Jordina; Zhang, Huiyan; Solsona, Pau; Barό, Maria Dolors; Suriñach, Santiago; Pellicer, Eva; Sort, Jordi

2018-02-11

Open cell foams consisting of Fe and Fe-Mn oxides are prepared from metallic Fe and Mn powder precursors by the replication method using porous polyurethane (PU) templates. First, reticulated PU templates are coated by slurry impregnation. The templates are then thermally removed at 260 °C and the debinded powders are sintered at 1000 °C under N₂ atmosphere. The morphology, structure, and magnetic properties are studied by scanning electron microscopy, X-ray diffraction and vibrating sample magnetometry, respectively. The obtained Fe and Fe-Mn oxide foams possess both high surface area and homogeneous open-cell structure. Hematite (α-Fe₂O₃) foams are obtained from the metallic iron slurry independently of the N₂ flow. In contrast, the microstructure of the FeMn-based oxide foams can be tailored by adjusting the N₂ flow. While the main phases for a N₂ flow rate of 180 L/h are α-Fe₂O₃ and FeMnO₃, the predominant phase for high N₂ flow rates (e.g., 650 L/h) is Fe₂MnO₄. Accordingly, a linear magnetization versus field behavior is observed for the hematite foams, while clear hysteresis loops are obtained for the Fe₂MnO₄ foams. Actually, the saturation magnetization of the foams containing Mn increases from 5 emu/g to 52 emu/g when the N₂ flow rate (i.e., the amount of Fe₂MnO₄) is increased. The obtained foams are appealing for a wide range of applications, such as electromagnetic absorbers, catalysts supports, thermal and acoustic insulation systems or wirelessly magnetically-guided porous objects in fluids.

Bubbling and foaming assisted clearing of mucin plugs in microfluidic Y-junctions.

PubMed

Abdula, Daner; Lerud, Ryan; Rananavare, Shankar

2017-11-07

Microfluidic Y-junctions were used to study mechanical mechanisms involved in pig gastric mucin (PGM) plug removal from within one of two bifurcation branches with 2-phase air and liquid flow. Water control experiments showed moderate plug removal due to shear from vortex formation in the blockage branch and suggest a PGM yield stress of 35Pa, as determined by computational fluid dynamics. Addition of hexadecyltrimethylammonium bromide (CTAB) surfactant improved clearing effectiveness due to bubbling in 1mm diameter channels and foaming in 500μm diameter channels. Plug removal mechanisms have been identified as vortex shear, bubble scouring, and then foam scouring as air flow rate is increased with constant liquid flow. The onset of bubbling and foaming is attributed to a flow regime transition from slug to slug-annular. Flow rates explored for 1mm channels are typically experienced by bronchioles in generations 8 and 9 of lungs. Results have implications on treatment of cystic fibrosis and other lung diseases. Copyright © 2016 Elsevier Ltd. All rights reserved.

Liquefaction processes and systems and liquefaction process intermediate compositions

DOEpatents

Schmidt, Andrew J.; Hart, Todd R.; Billing, Justin M.; Maupin, Gary D.; Hallen, Richard T.; Anderson, Daniel B.

2014-07-12

Liquefaction processes are provided that can include: providing a biomass slurry solution having a temperature of at least 300.degree. C. at a pressure of at least 2000 psig; cooling the solution to a temperature of less than 150.degree. C.; and depressurizing the solution to release carbon dioxide from the solution and form at least part of a bio-oil foam. Liquefaction processes are also provided that can include: filtering the biomass slurry to remove particulates; and cooling and depressurizing the filtered solution to form the bio-oil foam. Liquefaction systems are provided that can include: a heated biomass slurry reaction zone maintained above 300.degree. C. and at least 2000 psig and in continuous fluid communication with a flash cooling/depressurization zone maintained below 150.degree. C. and between about 125 psig and about atmospheric pressure. Liquefaction systems are also provided that can include a foam/liquid separation system. Liquefaction process intermediate compositions are provided that can include a bio-oil foam phase separated from an aqueous biomass solids solution.

High temperature ultralow water content carbon dioxide-in-water foam stabilized with viscoelastic zwitterionic surfactants.

PubMed

Alzobaidi, Shehab; Da, Chang; Tran, Vu; Prodanović, Maša; Johnston, Keith P

2017-02-15

Ultralow water content carbon dioxide-in-water (C/W) foams with gas phase volume fractions (ϕ) above 0.95 (that is <0.05 water) tend to be inherently unstable given that the large capillary pressures that cause the lamellar films to thin. Herein, we demonstrate that these C/W foams may be stabilized with viscoelastic aqueous phases formed with a single zwitterionic surfactant at a concentration of only 1% (w/v) in DI water and over a wide range of salinity. Moreover, they are stable with a foam quality ϕ up to 0.98 even for temperatures up to 120°C. The properties of aqueous viscoelastic solutions and foams containing these solutions are examined for a series of zwitterionic amidopropylcarbobetaines, R-ONHC 3 H 6 N(CH 3 ) 2 CH 2 CO 2 , where R is varied from C 12 - 14 (coco) to C 18 (oleyl) to C 22 (erucyl). For the surfactants with long C 18 and C 22 tails, the relaxation times from complex rheology indicate the presence of viscoelastic wormlike micelles over a wide range in salinity and pH, given the high surfactant packing fraction. The apparent viscosities of these ultralow water content foams reached more than 120cP with stabilities more than 30-fold over those for foams formed with the non-viscoelastic C 12 - 14 surfactant. At 90°C, the foam morphology was composed of ∼35μm diameter bubbles with a polyhedral texture. The apparent foam viscosity typically increased with ϕ and then dropped at ϕ values higher than 0.95-0.98. The Ostwald ripening rate was slower for foams with viscoelastic versus non-viscoelastic lamellae as shown by optical microscopy, as a consequence of slower lamellar drainage rates. The ability to achieve high stabilities for ultralow water content C/W foams over a wide temperature range is of interest in various technologies including polymer and materials science, CO 2 enhanced oil recovery, CO 2 sequestration (by greater control of the CO 2 flow patterns), and possibly even hydraulic fracturing with minimal use of water to reduce the requirements for wastewater disposal. Copyright © 2016. Published by Elsevier Inc.

Injection-Sensitive Mechanics of Hydraulic Fracture Interaction with Discontinuities

NASA Astrophysics Data System (ADS)

Chuprakov, D.; Melchaeva, O.; Prioul, R.

2014-09-01

We develop a new analytical model, called OpenT, that solves the elasticity problem of a hydraulic fracture (HF) contact with a pre-existing discontinuity natural fracture (NF) and the condition for HF re-initiation at the NF. The model also accounts for fluid penetration into the permeable NFs. For any angle of fracture intersection, the elastic problem of a blunted dislocation discontinuity is solved for the opening and sliding generated at the discontinuity. The sites and orientations of a new tensile crack nucleation are determined based on a mixed stress- and energy-criterion. In the case of tilted fracture intersection, the finite offset of the new crack initiation point along the discontinuity is computed. We show that aside from known controlling parameters such stress contrast, cohesional and frictional properties of the NFs and angle of intersection, the fluid injection parameters such as the injection rate and the fluid viscosity are of first-order in the crossing behavior. The model is compared to three independent laboratory experiments, analytical criteria of Blanton, extended Renshaw-Pollard, as well as fully coupled numerical simulations. The relative computational efficiency of OpenT model (compared to the numerical models) makes the model attractive for implementation in modern engineering tools simulating hydraulic fracture propagation in naturally fractured environments.

Particle Swarms in Fractures: Open Versus Partially Closed Systems

NASA Astrophysics Data System (ADS)

Boomsma, E.; Pyrak-Nolte, L. J.

2014-12-01

In the field, fractures may be isolated or connected to fluid reservoirs anywhere along the perimeter of a fracture. These boundaries affect fluid circulation, flow paths and communication with external reservoirs. The transport of drop like collections of colloidal-sized particles (particle swarms) in open and partially closed systems was studied. A uniform aperture synthetic fracture was constructed using two blocks (100 x 100 x 50 mm) of transparent acrylic placed parallel to each other. The fracture was fully submerged a tank filled with 100cSt silicone oil. Fracture apertures were varied from 5-80 mm. Partially closed systems were created by sealing the sides of the fracture with plastic film. The four boundary conditions study were: (Case 1) open, (Case 2) closed on the sides, (Case 3) closed on the bottom, and (Case 4) closed on both the sides and bottom of the fracture. A 15 μL dilute suspension of soda-lime glass particles in oil (2% by mass) were released into the fracture. Particle swarms were illuminated using a green (525 nm) LED array and imaged with a CCD camera. The presence of the additional boundaries modified the speed of the particle swarms (see figure). In Case 1, enhanced swarm transport was observed for a range of apertures, traveling faster than either very small or very large apertures. In Case 2, swarm velocities were enhanced over a larger range of fracture apertures than in any of the other cases. Case 3 shifted the enhanced transport regime to lower apertures and also reduced swarm speed when compared to Case 2. Finally, Case 4 eliminated the enhanced transport regime entirely. Communication between the fluid in the fracture and an external fluid reservoir resulted in enhanced swarm transport in Cases 1-3. The non-rigid nature of a swarm enables drag from the fracture walls to modify the swarm geometry. The particles composing a swarm reorganize in response to the fracture, elongating the swarm and maintaining its density. Unlike a drop or solid sphere, fracture boundaries do not exclusively decelerate swarm motion but instead produce enhanced swarm transport. Acknowledgments: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Geosciences Research Program under Award Number (DE-FG02-09ER16022).

[Maturation diagnosis in full term hypotrophic fetuses].

PubMed

Scharnke, H D; Gartzke, J; Fleischer, G; Isbruch, E

1977-01-01

Foam-Test by Clements is a valuable method for determining the foetus maturity of lungs. We introduce this test along with other parameters for the maturity-diagnosis since one year. In 15% result, the Foam-Test was not applicable because of blood, or meconic amniotic fluid, other wise wrong negative and in 0% wrong positive results. By unmatured child, there was doubtable results with Foam-Test. Since it is important to determine the early delivery of unmatured children, particularly the case of foetus maturity of lungs must be exact, we therefore decided to use the Lecithin/Sphingomyelinquotients in some cases. The results of Lecithin/Sphingomyelinquotient in unmatured children are almost with the approximated date under two. From this, one must deduce from these children, that the intrauterine unmatured lungs lately took place.

Can serpentinization induce fracturing? Fluid pathway development and the volume increase enigma

NASA Astrophysics Data System (ADS)

Plümper, Oliver; Jamtveit, Bjørn; Røyne, Anja

2013-04-01

Serpentinization of ultramafic rocks has first-order effects on global element cycles, the rheology of the oceanic lithosphere, plays a key role in plate tectonics by lubricating subduction zones and has been linked to the origin of life due to the creation of abiogenic hydrocarbons. In addition, the capability of ultramafic rocks to safely store enormous amounts of carbon dioxide through mineral reactions may provide a unique solution to fight global warming. However, all the aforementioned processes are reliant on the creation and maintenance of fluid pathways to alter an originally impermeable rock. Although the forces that move tectonic plates can produce these fluid pathways by mechanical fracturing, there is ample evidence that serpentinization reactions can 'eat' their way through a rock. This process is facilitated by solid volume changes during mineral reactions that cause expansion, fracturing the rock to generate fluid pathways. Natural observations of serpentinization/carbonation in ultramafic rocks indicate that the associated positive solid volume change alone exerts enough stress on the surrounding rock to build up a fracture network and that the influence of external tectonic forces is not necessary. Through various feedbacks these systems can either become self-sustaining, when an interconnected fracture network is formed, or self-limiting due to fluid pathway obstruction. However, extensively serpentinized outcrops suggest that although crystal growth in newly opened spaces would reduce permeability, serpentinization is not always self-limiting as porosity generation can occur concomitantly, maintaining or even increasing permeability. This is consistent with theory and demonstrates that fluids transported through fracture networks can alter vast amounts of originally impermeable rock. Nevertheless, whether serpentinization can actually generate these fracture networks is still a matter of debate and only a few scientific investigations have focused on this topic so far. Here, we investigate the feasibility of reaction-induced fracturing and pore space evolution during serpentinization by combining microstructural investigations using scanning/transmission electron microscopy and synchrotron micro-tomography of natural samples with theoretical considerations on the forces exerted during solid volume increasing reactions. We particularly focus on the interface-scale mechanism of reaction-induced fracturing (Plümper et al. 2012) and the establishment of microstructural markers (e.g., inert exsolutions in olivine) to identify volume changes and estimate crystallization pressures (Kelemen and Hirth 2012). Our investigations suggest that reaction-induced fracturing during serpentinization is possible and during certain physico-chemical circumstances a positive feedback to alter vast amounts of originally impermeable rock is established. Plümper O., Røyne A., Magraso A., Jamtveit B. (2012) The interface-scale mechanism of reaction-induced fracturing during serpentinization. Geology. 40, 1103-1106. Kelemen, P. B. & Hirth, G. (2012) Reaction-driven cracking during retrograde metamorphism: Olivine hydration and carbonation. Earth and Planetary Science Letters 345, 81-89.

Multistage crack seal vein and hydrothermal Ni enrichment in serpentinized ultramafic rocks (Koniambo massif, New Caledonia)

NASA Astrophysics Data System (ADS)

Cathelineau, Michel; Myagkiy, Andrey; Quesnel, Benoit; Boiron, Marie-Christine; Gautier, Pierre; Boulvais, Philippe; Ulrich, Marc; Truche, Laurent; Golfier, Fabrice; Drouillet, Maxime

2017-10-01

Sets of fractures and breccia sealed by Ni-rich silicates and quartz occur within saprock of the New Caledonian regolith developed over ultramafic rocks. The crystallization sequence in fractures is as follows: (1) serpentine stage: lizardite > polygonal serpentine > white lizardite; (2) Ni stage: Ni-Mg kerolite followed by red-brown microcrystalline quartz; and (3) supergene stages. The red-brown microcrystalline quartz corresponds to the very last stage of the Ni sequence and is inferred to have precipitated within the 50-95 °C temperature range. It constitutes also the main cement of breccia that has all the typical features of hydraulic fracturing. The whole sequence is therefore interpreted as the result of hydrothermal fluid circulation under medium to low temperature and fluctuating fluid pressure. Although frequently described as the result of a single downward redistribution of Ni and Mg leached in the upper part of the regolith under ambient temperature, the Ni silicate veins thus appear as the result of recurrent crack and seal process, corresponding to upward medium temperature fluid convection, hydraulic fracturing and subsequent fluid mixing, and mineral deposition.

Study on the reutilization of clear fracturing flowback fluids in surfactant flooding with additives for Enhanced Oil Recovery (EOR).

PubMed

Dai, Caili; Wang, Kai; Liu, Yifei; Fang, Jichao; Zhao, Mingwei

2014-01-01

An investigation was conducted to study the reutilization of clear fracturing flowback fluids composed of viscoelastic surfactants (VES) with additives in surfactant flooding, making the process more efficient and cost-effective. The clear fracturing flowback fluids were used as surfactant flooding system with the addition of α-olefin sulfonate (AOS) for enhanced oil recovery (EOR). The interfacial activity, emulsification activity and oil recovery capability of the recycling system were studied. The interfacial tension (IFT) between recycling system and oil can be reduced by 2 orders of magnitude to 10(-3) mN/m, which satisfies the basic demand of surfactant flooding. The oil can be emulsified and dispersed more easily due to the synergetic effect of VES and AOS. The oil-wet surface of quartz can be easily converted to water-wet through adsorption of surfactants (VES/AOS) on the surface. Thirteen core plug flooding tests were conducted to investigate the effects of AOS concentrations, slug sizes and slug types of the recycling system on the incremental oil recovery. The investigations prove that reclaiming clear fracturing flowback fluids after fracturing operation and reuse it in surfactant flooding might have less impact on environment and be more economical.

Study on the Reutilization of Clear Fracturing Flowback Fluids in Surfactant Flooding with Additives for Enhanced Oil Recovery (EOR)

PubMed Central

Dai, Caili; Wang, Kai; Liu, Yifei; Fang, Jichao; Zhao, Mingwei

2014-01-01

An investigation was conducted to study the reutilization of clear fracturing flowback fluids composed of viscoelastic surfactants (VES) with additives in surfactant flooding, making the process more efficient and cost-effective. The clear fracturing flowback fluids were used as surfactant flooding system with the addition of α-olefin sulfonate (AOS) for enhanced oil recovery (EOR). The interfacial activity, emulsification activity and oil recovery capability of the recycling system were studied. The interfacial tension (IFT) between recycling system and oil can be reduced by 2 orders of magnitude to 10−3 mN/m, which satisfies the basic demand of surfactant flooding. The oil can be emulsified and dispersed more easily due to the synergetic effect of VES and AOS. The oil-wet surface of quartz can be easily converted to water-wet through adsorption of surfactants (VES/AOS) on the surface. Thirteen core plug flooding tests were conducted to investigate the effects of AOS concentrations, slug sizes and slug types of the recycling system on the incremental oil recovery. The investigations prove that reclaiming clear fracturing flowback fluids after fracturing operation and reuse it in surfactant flooding might have less impact on environment and be more economical. PMID:25409507

Complementary hydro-mechanical coupled finite/discrete element and microseismic modelling to predict hydraulic fracture propagation in tight shale reservoirs

NASA Astrophysics Data System (ADS)

Profit, Matthew; Dutko, Martin; Yu, Jianguo; Cole, Sarah; Angus, Doug; Baird, Alan

2016-04-01

This paper presents a novel approach to predict the propagation of hydraulic fractures in tight shale reservoirs. Many hydraulic fracture modelling schemes assume that the fracture direction is pre-seeded in the problem domain discretisation. This is a severe limitation as the reservoir often contains large numbers of pre-existing fractures that strongly influence the direction of the propagating fracture. To circumvent these shortcomings, a new fracture modelling treatment is proposed where the introduction of discrete fracture surfaces is based on new and dynamically updated geometrical entities rather than the topology of the underlying spatial discretisation. Hydraulic fracturing is an inherently coupled engineering problem with interactions between fluid flow and fracturing when the stress state of the reservoir rock attains a failure criterion. This work follows a staggered hydro-mechanical coupled finite/discrete element approach to capture the key interplay between fluid pressure and fracture growth. In field practice, the fracture growth is hidden from the design engineer and microseismicity is often used to infer hydraulic fracture lengths and directions. Microseismic output can also be computed from changes of the effective stress in the geomechanical model and compared against field microseismicity. A number of hydraulic fracture numerical examples are presented to illustrate the new technology.

Fault and fracture patterns in low porosity chalk and their potential influence on sub-surface fluid flow-A case study from Flamborough Head, UK

NASA Astrophysics Data System (ADS)

Sagi, D. A.; De Paola, N.; McCaffrey, K. J. W.; Holdsworth, R. E.

2016-10-01

To better understand fault zone architecture and fluid flow in mesoscale fault zones, we studied normal faults in chalks with displacements up to 20 m, at two representative localities in Flamborough Head (UK). At the first locality, chalk contains cm-thick, interlayered marl horizons, whereas at the second locality marl horizons were largely absent. Cm-scale displacement faults at both localities display ramp-flat geometries. Mesoscale fault patterns in the marl-free chalk, including a larger displacement fault (20 m) containing multiple fault strands, show widespread evidence of hydraulically-brecciated rocks, whereas clays smears along fault planes, and injected into open fractures, and a simpler fault zone architecture is observed where marl horizons are present. Hydraulic brecciation and veins observed in the marl-free chalk units suggest that mesoscale fault patterns acted as localized fault conduit allowing for widespread fluid flow. On the other hand, mesoscale fault patterns developed in highly fractured chalk, which contains interlayered marl horizons can act as localized barriers to fluid flow, due to the sealing effect of clays smears along fault planes and introduced into open fractures in the damage zone. To support our field observations, quantitative analyses carried out on the large faults suggest a simple fault zone in the chalk with marl units with fracture density/connectivity decreasing towards the protolith. Where marls are absent, density is high throughout the fault zone, while connectivity is high only in domains nearest the fault core. We suggest that fluid flow in fractured chalk is especially influenced by the presence of marls. When present, it can smear onto fault planes, forming localised barriers. Fluid flow along relatively large displacement faults is additionally controlled by the complexity of the fault zone, especially the size/geometry of weakly and intensely connected damage zone domains.

Nanocellular foam with solid flame retardant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Liang; Kelly-Rowley, Anne M.; Bunker, Shana P.

Prepare nanofoam by (a) providing an aqueous solution of a flame retardant dissolved in an aqueous solvent, wherein the flame retardant is a solid at 23.degree. C. and 101 kiloPascals pressure when in neat form; (b) providing a fluid polymer composition selected from a solution of polymer dissolved in a water-miscible solvent or a latex of polymer particles in a continuous aqueous phase; (c) mixing the aqueous solution of flame retardant with the fluid polymer composition to form a mixture; (d) removing water and, if present, solvent from the mixture to produce a polymeric composition having less than 74 weight-percentmore » flame retardant based on total polymeric composition weight; (e) compound the polymeric composition with a matrix polymer to form a matrix polymer composition; and (f) foam the matrix polymer composition into nanofoam having a porosity of at least 60 percent.« less

Dynamic bed reactor

DOEpatents

Stormo, Keith E.

1996-07-02

A dynamic bed reactor is disclosed in which a compressible open cell foam matrix is periodically compressed and expanded to move a liquid or fluid through the matrix. In preferred embodiments, the matrix contains an active material such as an enzyme, biological cell, chelating agent, oligonucleotide, adsorbent or other material that acts upon the liquid or fluid passing through the matrix. The active material may be physically immobilized in the matrix, or attached by covalent or ionic bonds. Microbeads, substantially all of which have diameters less than 50 microns, can be used to immobilize the active material in the matrix and further improve reactor efficiency. A particularly preferred matrix is made of open cell polyurethane foam, which adsorbs pollutants such as polychlorophenol or o-nitrophenol. The reactors of the present invention allow unidirectional non-laminar flow through the matrix, and promote intimate exposure of liquid reactants to active agents such as microorganisms immobilized in the matrix.

Fluid-driven fracture and melt transport through lithosphere on earth and terrestrial planets

NASA Astrophysics Data System (ADS)

Fialko, Yuri Alex

Fluid-driven fracture is a fundamental geophysical phenomenon operating in planetary interiors on many scales. A few examples of geological processes involving fluid transport via self-induced fractures include melt segregation in the mantle, magma ascent through the lithosphere, crustal accretion at mid-ocean ridges and volcanic "hot spots", migration of metamorphic and sedimentary fluids in the crust, etc. Overall, fluid-driven (in particular, magma-driven) fracture plays a major role in chemical differentiation of the upper mantle. Because our ability to make direct observations of the dynamics and styles of fluid-driven fracture is quite limited, our understanding of this phenomenon relies on theoretical models that use fundamental physical principles and available field data to constrain the behavior of fluid-driven cracks at depth. This thesis proposes new and more accurate ways of theoretical and experimental description of magma transport in self-induced fractures, or dikes. Dike propagation is a complex process that involves elastic and inelastic deformation of the host rocks, rock fracture, viscous flow of magma, heat transfer, and phase transitions (e.g., rock crystallization and fusion, volatile exolution etc.). We consider relationships between different physical processes associated with magma transport in dikes by solving appropriate boundary value problems of continuum mechanics and heat and mass transfer. The first chapter of this thesis revises existing interpretations of available experimental data bearing on the role of fracture resistance in the overall energy balance during dike propagation. It is shown for the first time that the experimental data indicate that the rock tensile fracture energy, which is not a material property at elevated confining pressures, may substantially increase under in-situ stress conditions. The second chapter concentrates on the interaction between magma flow, heat transfer and phase changes associated with dike emplacement, and discusses some important implications of our results for the generation of the Earth's crust at mid-ocean ridges. In particular, we find that the thermal arrest lengths of typical mid-ocean ridge dikes are of the order of the wavelength of crustal thickness variations and transform fault spacing along slow spreading ridges. This suggests that thermal controls on the crustal melt delivery system could be an important factor in modulating these variations. The third chapter deals with fluid-mechanical aspects of lateral dike propagation in volcanic rift zones. We demonstrate the existence of a feedback between viscous pressure losses during magma transport at depth and the along-strike surface topography of a rift zone. Our estimated values of the along-strike slopes resulting from such a feedback are in general agreement with observations in Hawaiian rift zones. The fourth chapter explores mechanisms of emplacement of giant dike swarms that might have played a role in splitting continents and producing mass extinctions. We reconcile field observations of chilled margins, low crustal contamination, and large dike thicknesses with the theoretically inferred turbulent mode of magma flow in such dikes.

Modeling of Compositional Effects of Foam Assisted CO2 Storage Processes

NASA Astrophysics Data System (ADS)

Naderi Beni, A.; Varavei, A.; Farajzadeh, R.; Delshad, M.

2012-12-01

Foaming of carbon dioxide (CO2, e.g. from fossil-fuel power plants) has been proposed as a possible strategy to resolve the limitations of direct disposal of CO2 into (saline) aquifers. Such limitations include gravity segregation that may damage the caprock and aquifer rock property alteration as a result of geochemical interactions. Foam may also block the CO2 leakage paths, resulting in an overall storage security enhancement. In this regard, specific aspects of composition and type of gas (N2 vs. CO2) may affect the foaming properties of gas-surfactant systems. The aim of this study is to determine these effects on the foaming properties of gas-surfactant solutions. To this end, we study the physics of foam assisted CO2 storage by modeling coreflood experiments. Different options such as simplified population balance foam model and a table-look-up approach were used to couple the fluid flow and mass transport equations in a reservoir simulator. Both laboratory and numerical results show that three regions along the flow direction can be distinguished: (i) an upstream region characterized by low liquid saturation, (ii) a region downstream of the foam front where the liquid saturation is still unchanged with a value of one and (iii) a frontal region characterized by a mixing of flowing foam and liquid, exhibiting fine fingering effects. It is also shown that the extent of the fingering behavior caused by the rock heterogeneity depends on foam strength. Additionally, permeation of gas through foam films is a strong function of water salinity and appears to have significant impact on foam in CO2 storage. It further turns out that the amount of dissolved CO2 in brine can be considerable and, therefore, the effect of water solubility cannot be neglected in simulation studies. In summary, the differences in the foaming behavior of nitrogen and carbon dioxide can be explained by the differences in their physical properties of solubility in water, interfacial tension, pH effect, and wettability. Among which solubility seems to be the most critical one because (1) the amount of available CO2 for foaming will be lower due to its higher dissolution compared to N2 at similar conditions and (2) it significantly affects gas permeability coefficient and thus the foam stability.

Insights on fluid-rock interaction evolution during deformation from fracture network geochemistry at reservoir-scale

NASA Astrophysics Data System (ADS)

Beaudoin, Nicolas; Koehn, Daniel; Lacombe, Olivier; Bellahsen, Nicolas; Emmanuel, Laurent

2015-04-01

Fluid migration and fluid-rock interactions during deformation is a challenging problematic to picture. Numerous interplays, as between porosity-permeability creation and clogging, or evolution of the mechanical properties of rock, are key features when it comes to monitor reservoir evolution, or to better understand seismic cycle n the shallow crust. These phenomenoms are especially important in foreland basins, where various fluids can invade strata and efficiently react with limestones, altering their physical properties. Stable isotopes (O, C, Sr) measurements and fluid inclusion microthermometry of faults cement and veins cement lead to efficient reconstruction of the origin, temperature and migration pathways for fluids (i.e. fluid system) that precipitated during joints opening or faults activation. Such a toolbox can be used on a diffuse fracture network that testifies the local and/or regional deformation history experienced by the rock at reservoir-scale. This contribution underlines the advantages and limits of geochemical studies of diffuse fracture network at reservoir-scale by presenting results of fluid system reconstruction during deformation in folded structures from various thrust-belts, tectonic context and deformation history. We compare reconstructions of fluid-rock interaction evolution during post-deposition, post-burial growth of basement-involved folds in the Sevier-Laramide American Rocky Mountains foreland, a reconstruction of fluid-rock interaction evolution during syn-depostion shallow detachment folding in the Southern Pyrenean foreland, and a preliminary reconstruction of fluid-rock interactions in a post-deposition, post-burial development of a detachment fold in the Appenines. Beyond regional specification for the nature of fluids, a common behavior appears during deformation as in every fold, curvature-related joints (related either to folding or to foreland flexure) connected vertically the pre-existing stratified fluid system. The lengthscale of the migration and the nature of invading fluids during these connections is different in every studied example, and can be related to the tectonic nature of the fold, along with the burial depth at the time of deformation. Thus, to decipher fluid-fracture relationships provides insights to better reconstruct the mechanisms of deformation at reservoir-scale.

Acoustic and vibrational damping in porous solids.

PubMed

Göransson, Peter

2006-01-15

A porous solid may be characterized as an elastic-viscoelastic and acoustic-viscoacoustic medium. For a flexible, open cell porous foam, the transport of energy is carried both through the sound pressure waves propagating through the fluid in the pores, and through the elastic stress waves carried through the solid frame of the material. For a given situation, the balance between energy dissipated through vibration of the solid frame, changes in the acoustic pressure and the coupling between the waves varies with the topological arrangement, choice of material properties, interfacial conditions, etc. Engineering of foams, i.e. designs built on systematic and continuous relationships between polymer chemistry, processing, micro-structure, is still a vision for the future. However, using state-of-the-art simulation techniques, multiple layer arrangements of foams may be tuned to provide acoustic and vibrational damping at a low-weight penalty. In this paper, Biot's modelling of porous foams is briefly reviewed from an acoustics and vibrations perspective with a focus on the energy dissipation mechanisms. Engineered foams will be discussed in terms of results from simulations performed using finite element solutions. A layered vehicle-type structure is used as an example.

Fracture network topology and characterization of structural permeability

NASA Astrophysics Data System (ADS)

Hansberry, Rowan; King, Rosalind; Holford, Simon

2017-04-01

There are two fundamental requirements for successful geothermal development: elevated temperatures at accessible depths, and a reservoir from which fluids can be extracted. The Australian geothermal sector has successfully targeted shallow heat, however, due in part to the inherent complexity of targeting permeability, obtaining adequate flow rates for commercial production has been problematic. Deep sedimentary aquifers are unlikely to be viable geothermal resources due to the effects of diagenetic mineral growth on rock permeability. Therefore, it is likely structural permeability targets, exploiting natural or induced fracture networks will provide the primary means for fluid flow in geothermal, as well as unconventional gas, reservoirs. Recent research has focused on the pattern and generation of crustal stresses across Australia, while less is known about the resultant networks of faults, joints, and veins that can constitute interconnected sub-surface permeability pathways. The ability of a fracture to transmit fluid is controlled by the orientation and magnitude of the in-situ stress field that acts on the fracture walls, rock strength, and pore pressure, as well as fracture properties such as aperture, orientation, and roughness. Understanding the distribution, orientation and character of fractures is key to predicting structural permeability. This project focuses on extensive mapping of fractures over various scales in four key Australian basins (Cooper, Otway, Surat and Perth) with the potential to host geothermal resources. Seismic attribute analysis is used in concert with image logs from petroleum wells, and field mapping to identify fracture networks that are usually not resolved in traditional seismic interpretation. We use fracture network topology to provide scale-invariant characterisation of fracture networks from multiple data sources to assess similarity between data sources, and fracture network connectivity. These results are compared with other permeability indicators such as drilling fluid losses, and pore pressure measurements. Initial work with these techniques has led to new developments in our ability to image subsurface faults and fractures at a variety of scales from independent datasets. We establish a strong relationship between features identified using seismic attribute analysis and interpreted natural fractures. However, care must be taken to use these methods in a case-by-case basis, as controls on fracture distribution and orientation can vary significantly with both regional and local influences. These results outline and effective method by which structural permeability can be assessed with existing petroleum datasets. However, unlike the broad stress field, mapping fracture orientation and characteristics within the Australian Continent is complicated as the distribution, geometry, areal extent and connectivity of fracture networks can vary significantly.

Nonlinear Fluid Migration Patterns in Fractured Reservoirs due to Stress-Pressure Coupling induced Changes in Reservoir Permeabilities

NASA Astrophysics Data System (ADS)

Annewandter, R.; Geiger, S.; Main, I. G.

2011-12-01

Sustainable storage of carbon dioxide (CO2) requires a thorough understanding of injection induced pressure build-up and its effects on the storage formation's integrity, since it determines the cap rock's sealing properties as well as the total storable amount of carbon dioxide. Fractures are abundant in the subsurface and difficult to detect due to their subseismic characteristic. If present in the cap during injection, they can be primary pathways for CO2 leakage. The North Sea is considered as Europe's most important carbon dioxide storage area. However, almost all of the potential storage formations have been exposed to post-glacial lithospheric flexure, possibly causing the generation of new fracture networks in the overburden whilst rebounding. Drawing upon, fast carbon dioxide uprise can be facilitated due to opening of fractures caused by changes in the stress field over time. The overall effective permeability, and hence possible leakage rates, of a fractured storage formation is highly sensitive to the fracture aperture which itself depends on the far field and in situ stress field. For this reason, our in-house general purpose reservoir simulator Complex System Modeling Platform (CSMP++) has been expanded, which is particularly designed to simulate multiphase flow on fractured porous media. It combines finite element (FE) and finite volume (FV) methods on mixed-dimensional hybrid-element meshes. The unstructured FE-FV based scheme allows us to model complex geological structures, such as fractures, at great detail. The simulator uses a compositional model for NaCl-H2O-CO2-systems for compressible fluids for computing thermophysical properties as a function of formation pressure and temperature. A fixed stress-split sequential procedure is being used to calculate coupled fluid flow and geomechanics. Numerical proof of concept studies will be presented showing the impact of fracture opening and closure on fluid migration patterns due to coupled stress-pressure induced changes in effective permeabilities.

Hydraulic Fracture Growth in a Layered Formation based on Fracturing Experiments and Discrete Element Modeling

NASA Astrophysics Data System (ADS)

Yushi, Zou; Xinfang, Ma; Tong, Zhou; Ning, Li; Ming, Chen; Sihai, Li; Yinuo, Zhang; Han, Li

2017-09-01

Hydraulic fracture (HF) height containment tends to occur in layered formations, and it significantly influences the entire HF geometry or the stimulated reservoir volume. This study aims to explore the influence of preexisting bedding planes (BPs) on the HF height growth in layered formations. Laboratory fracturing experiments were performed to confirm the occurrence of HF height containment in natural shale that contains multiple weak and high-permeability BPs under triaxial stresses. Numerical simulations were then conducted to further illustrate the manner in which vertical stress, BP permeability, BP density(or spacing), pump rate, and fluid viscosity control HF height growth using a 3D discrete element method-based fracturing model. In this model, the rock matrix was considered transversely isotropic and multiple BPs can be explicitly represented. Experimental and numerical results show that the vertically growing HF tends to be limited by multi-high-permeability BPs, even under higher vertical stress. When the vertically growing HF intersects with the multi-high-permeability BPs, the injection pressure will be sharply reduced. If a low pumping rate or a low-viscosity fluid is used, the excess fracturing fluid leak-off into the BPs obviously decreases the rate of pressure build up, which will then limit the growth of HF. Otherwise, a higher pumping rate and/or a higher viscosity will reduce the leak-off time and fluid volume, but increase the injection pressure to drive the HF to grow and to penetrate through the BPs.

Design of experimental system for supercritical CO2 fracturing under confining pressure conditions

NASA Astrophysics Data System (ADS)

Wang, H.; Lu, Q.; Li, X.; Yang, B.; Zheng, Y.; Shi, L.; Shi, X.

2018-03-01

Supercritical CO2 has the characteristics of low viscosity, high diffusion and zero surface tension, and it is considered as a new fluid for non-polluting and non-aqueous fracturing which can be used for shale gas development. Fracturing refers to a method of utilizing the high-pressure fluid to generate fractures in the rock formation so as to improve the oil and gas flow conditions and increase the oil and gas production. In this article, a new type of experimental system for supercritical CO2 fracturing under confining pressure conditions is designed, which is based on characteristics of supercritical CO2, shale reservoir and down-hole environment. The experimental system consists of three sub-systems, including supercritical CO2 generation system, supercritical CO2 fracturing system and data analysis system. It can be used to simulate supercritical CO2 fracturing under geo-stress conditions, thus to study the rock initiation pressure, the formation of the rock fractures, fractured surface morphology and so on. The experimental system has successfully carried out a series of supercritical CO2 fracturing experiments. The experimental results confirm the feasibility of the experimental system and the high efficiency of supercritical CO2 in fracturing tight rocks.

Fluid-driven fracture propagation in heterogeneous media: Probability distributions of fracture trajectories

NASA Astrophysics Data System (ADS)

Santillán, David; Mosquera, Juan-Carlos; Cueto-Felgueroso, Luis

2017-11-01

Hydraulic fracture trajectories in rocks and other materials are highly affected by spatial heterogeneity in their mechanical properties. Understanding the complexity and structure of fluid-driven fractures and their deviation from the predictions of homogenized theories is a practical problem in engineering and geoscience. We conduct a Monte Carlo simulation study to characterize the influence of heterogeneous mechanical properties on the trajectories of hydraulic fractures propagating in elastic media. We generate a large number of random fields of mechanical properties and simulate pressure-driven fracture propagation using a phase-field model. We model the mechanical response of the material as that of an elastic isotropic material with heterogeneous Young modulus and Griffith energy release rate, assuming that fractures propagate in the toughness-dominated regime. Our study shows that the variance and the spatial covariance of the mechanical properties are controlling factors in the tortuousness of the fracture paths. We characterize the deviation of fracture paths from the homogenous case statistically, and conclude that the maximum deviation grows linearly with the distance from the injection point. Additionally, fracture path deviations seem to be normally distributed, suggesting that fracture propagation in the toughness-dominated regime may be described as a random walk.

Fluid-driven fracture propagation in heterogeneous media: Probability distributions of fracture trajectories.

PubMed

Santillán, David; Mosquera, Juan-Carlos; Cueto-Felgueroso, Luis

2017-11-01

Hydraulic fracture trajectories in rocks and other materials are highly affected by spatial heterogeneity in their mechanical properties. Understanding the complexity and structure of fluid-driven fractures and their deviation from the predictions of homogenized theories is a practical problem in engineering and geoscience. We conduct a Monte Carlo simulation study to characterize the influence of heterogeneous mechanical properties on the trajectories of hydraulic fractures propagating in elastic media. We generate a large number of random fields of mechanical properties and simulate pressure-driven fracture propagation using a phase-field model. We model the mechanical response of the material as that of an elastic isotropic material with heterogeneous Young modulus and Griffith energy release rate, assuming that fractures propagate in the toughness-dominated regime. Our study shows that the variance and the spatial covariance of the mechanical properties are controlling factors in the tortuousness of the fracture paths. We characterize the deviation of fracture paths from the homogenous case statistically, and conclude that the maximum deviation grows linearly with the distance from the injection point. Additionally, fracture path deviations seem to be normally distributed, suggesting that fracture propagation in the toughness-dominated regime may be described as a random walk.

The influence of open fracture anisotropy on CO2 movement within geological storage complexes

NASA Astrophysics Data System (ADS)

Bond, C. E.; Wightman, R.; Ringrose, P. S.

2012-12-01

Carbon mitigation through the geological storage of carbon dioxide is dependent on the ability of geological formations to store CO2 trapping it within a geological storage complex. Secure long-term containment needs to be demonstrated, due to both political and social drivers, meaning that this containment must be verifiable over periods of 100-105 years. The effectiveness of sub-surface geological storage systems is dependent on trapping CO2 within a volume of rock and is reliant on the integrity of the surrounding rocks, including their chemical and physical properties, to inhibit migration to the surface. Oil and gas reservoir production data, and field evidence show that fracture networks have the potential to act as focused pathways for fluid movement. Fracture networks can allow large volumes of fluid to migrate to the surface within the time scales of interest. In this paper we demonstrate the importance of predicting the effects of fracture networks in storage, using a case study from the In Salah CO2 storage site, and show how the fracture permeability is closely controlled by the stress regime that determines the open fracture network. Our workflow combines well data of imaged fractures, with a discrete fracture network (DFN) model of tectonically induced fractures, within the horizon of interest. The modelled and observed fractures have been compared and combined with present day stress data to predict the open fracture network and its implications for anisotropic movement of CO2 in the sub-surface. The created fracture network model has been used to calculate the 2D permeability tensor for the reservoir for two scenarios: 1) a model in which all fractures are permeable, based on the whole DFN model and 2) those fractures determined to be in dilatational failure under the present day stress regime, a sub-set of the DFN. The resulting permeability anisotropy tensors show distinct anisotropies for the predicted CO2 movement within the reservoir. These predictions have been compared with InSAR imagery of surface uplift, used as an indicator of fluid pressure and movement in the sub-surface, around the CO2 injection wells. The analysis shows that the permeability tensor with the greatest anisotropy, that for the DFN sub-set of open fractures, matches well with the anisotropy in surface uplift imaged by InSAR. We demonstrate that predicting fracture networks alone does not predict fluid movement in the sub-surface, and that fracture permeability is closely controlled by the stress regime that determines the open fracture network. Our results show that a workflow of fracture network prediction combined with present day stress analysis can be used to successfully predict CO2 movement in the sub-surface at an active injection site.

A new estimation of equivalent matrix block sizes in fractured media with two-phase flow applications in dual porosity models

NASA Astrophysics Data System (ADS)

Jerbi, Chahir; Fourno, André; Noetinger, Benoit; Delay, Frederick

2017-05-01

Single and multiphase flows in fractured porous media at the scale of natural reservoirs are often handled by resorting to homogenized models that avoid the heavy computations associated with a complete discretization of both fractures and matrix blocks. For example, the two overlapping continua (fractures and matrix) of a dual porosity system are coupled by way of fluid flux exchanges that deeply condition flow at the large scale. This characteristic is a key to realistic flow simulations, especially for multiphase flow as capillary forces and contrasts of fluid mobility compete in the extraction of a fluid from a capacitive matrix then conveyed through the fractures. The exchange rate between fractures and matrix is conditioned by the so-called mean matrix block size which can be viewed as the size of a single matrix block neighboring a single fracture within a mesh of a dual porosity model. We propose a new evaluation of this matrix block size based on the analysis of discrete fracture networks. The fundaments rely upon establishing at the scale of a fractured block the equivalence between the actual fracture network and a Warren and Root network only made of three regularly spaced fracture families parallel to the facets of the fractured block. The resulting matrix block sizes are then compared via geometrical considerations and two-phase flow simulations to the few other available methods. It is shown that the new method is stable in the sense it provides accurate sizes irrespective of the type of fracture network investigated. The method also results in two-phase flow simulations from dual porosity models very close to that from references calculated in finely discretized networks. Finally, calculations of matrix block sizes by this new technique reveal very rapid, which opens the way to cumbersome applications such as preconditioning a dual porosity approach applied to regional fractured reservoirs.

Evaluation of geophysical logs, Phase II, November 1998 to May 1999, at Crossley Farms Superfund Site, Berks County, Pennsylvania

USGS Publications Warehouse

Conger, Randall W.

2000-01-01

Between November 1998 and May 1999, geophysical logging was conducted in 29 boreholes at the Crossley Farms Superfund Site, Hereford Township, Berks County, Pa., to determine the fluidproducing zones, fluid-receiving zones, zones of vertical borehole flow, and casing depth. The wells range in depth from 96 to 500 feet below land surface. Gamma logs only were collected in three bedrock wells. The geophysical logging determined the placement of well screens and packers, which allow monitoring and sampling of water-bearing zones in the fractured bedrock so that the horizontal and vertical distribution of contaminated ground water migrating from known sources could be determined. Geophysical logging included collection of caliper, video, fluid-temperature, fluid-resistivity, single-point-resistance, natural-gamma, fluid-flow, and acoustic-televiewer logs. Caliper and video logs were used to locate fractures, joints, and weathered zones. Inflections on fluidtemperature and fluid-resistivity logs indicated possible water-bearing fractures, and flowmeter measurements verified these locations. Single-point-resistance and natural-gamma logs provided information on stratigraphy. After interpretation of geophysical, video logs, and drillers notes, 24 of the wells were reconstructed such that water levels can be monitored and water samples collected from discrete water-bearing fractures in each well.

Visualizing and quantifying the crossover from capillary fingering to viscous fingering in a rough fracture

NASA Astrophysics Data System (ADS)

Chen, Yi-Feng; Fang, Shu; Wu, Dong-Sheng; Hu, Ran

2017-09-01

Immiscible fluid-fluid displacement in permeable media is important in many subsurface processes, including enhanced oil recovery and geological CO2 sequestration. Controlled by capillary and viscous forces, displacement patterns of one fluid displacing another more viscous one exhibit capillary and viscous fingering, and crossover between the two. Although extensive studies investigated viscous and capillary fingering in porous media, a few studies focused on the crossover in rough fractures, and how viscous and capillary forces affect the crossover remains unclear. Using a transparent fracture-visualization system, we studied how the two forces impact the crossover in a horizontal rough fracture. Drainage experiments of water displacing oil were conducted at seven flow rates (capillary number log10Ca ranging from -7.07 to -3.07) and four viscosity ratios (M=1/1000,1/500,1/100 and 1/50). We consistently observed lower invading fluid saturations in the crossover zone. We also proposed a phase diagram for the displacement patterns in a rough fracture that is consistent with similar studies in porous media. Based on real-time imaging and statistical analysis of the invasion morphology, we showed that the competition between capillary and viscous forces is responsible for the saturation reduction in the crossover zone. In this zone, finger propagation toward the outlet (characteristic of viscous fingering) as well as void-filling in the transverse/backward directions (characteristic of capillary fingering), are both suppressed. Therefore, the invading fluid tends to occupy larger apertures with higher characteristic front velocity, promoting void-filling toward the outlet with thinner finger growth and resulting in a larger volume of defending fluid left behind.

Surface Spills at Unconventional Oil and Gas Sites: a Contaminant Transport Modeling Study for the South Platte Alluvial Aquifer

NASA Astrophysics Data System (ADS)

McCray, J. E.; Kanno, C.; McLaughlin, M.; Blotevogel, J.; Borch, T.

2016-12-01

Hydraulic fracturing has revolutionized the U.S.'s energy portfolio by making shale reservoirs productive and commercially viable. However, the public is concerned that the chemical constituents in hydraulic fracturing fluid, produced water, or natural gas itself could potentially impact groundwater. Here, we present fate and transport simulations of aqueous fluid surface spills. Surface spills are the most likely contamination pathway to occur during oil and gas production operations. We have three primary goals: 1) evaluate whether or not these spills pose risks to groundwater quality in the South Platte aquifer system, 2) develop a screening level methodology that could be applied at other sites and for various pollutants, and 3) demonstrate the potential importance of co-contaminant interactions using selected chemicals. We considered two types of fluid that can be accidentally released at oil and gas sites: produced water and hydraulic fracturing fluid. Benzene was taken to be a representative contaminant of interest for produced water. Glutaraldehyde, polyethylene glycol, and polyacrylamide were the chemical additives considered for spills of hydraulic fracturing fluid. We focused on the South Platte Alluvial Aquifer, which is located in the greater Denver metro area and overlaps a zone of high-density oil and gas development. Risk of groundwater pollution was based on predicted concentration at the groundwater table. In general, results showed groundwater contamination due to produced water and hydraulic fracturing fluid spills is low in most areas of the South Platte system for the contaminants and spill conditions investigated. Substantial risk may exist in certain areas where the groundwater table is shallow (less than 10 ft below ground surface) and when large spills and large post-spill storms occur. Co-chemical interactions are an important consideration in certain cases when modeling hydraulic fracturing fluid spills. By helping to identify locations in the Front Range of Colorado that are at low or high risk for groundwater contamination due to a surface spill, this work will aid in improving prevention and mitigation practices so that decision-makers can be better prepared to address accidental releases in Colorado.

Hydraulic fracturing: paving the way for a sustainable future?

PubMed

Chen, Jiangang; Al-Wadei, Mohammed H; Kennedy, Rebekah C M; Terry, Paul D

2014-01-01

With the introduction of hydraulic fracturing technology, the United States has become the largest natural gas producer in the world with a substantial portion of the production coming from shale plays. In this review, we examined current hydraulic fracturing literature including associated wastewater management on quantity and quality of groundwater. We conclude that proper documentation/reporting systems for wastewater discharge and spills need to be enforced at the federal, state, and industrial level. Furthermore, Underground Injection Control (UIC) requirements under SDWA should be extended to hydraulic fracturing operations regardless if diesel fuel is used as a fracturing fluid or not. One of the biggest barriers that hinder the advancement of our knowledge on the hydraulic fracturing process is the lack of transparency of chemicals used in the practice. Federal laws mandating hydraulic companies to disclose fracturing fluid composition and concentration not only to federal and state regulatory agencies but also to health care professionals would encourage this practice. The full disclosure of fracturing chemicals will allow future research to fill knowledge gaps for a better understanding of the impacts of hydraulic fracturing on human health and the environment.

Hydraulic Fracturing: Paving the Way for a Sustainable Future?

PubMed Central

Chen, Jiangang; Al-Wadei, Mohammed H.; Kennedy, Rebekah C. M.; Terry, Paul D.

2014-01-01

With the introduction of hydraulic fracturing technology, the United States has become the largest natural gas producer in the world with a substantial portion of the production coming from shale plays. In this review, we examined current hydraulic fracturing literature including associated wastewater management on quantity and quality of groundwater. We conclude that proper documentation/reporting systems for wastewater discharge and spills need to be enforced at the federal, state, and industrial level. Furthermore, Underground Injection Control (UIC) requirements under SDWA should be extended to hydraulic fracturing operations regardless if diesel fuel is used as a fracturing fluid or not. One of the biggest barriers that hinder the advancement of our knowledge on the hydraulic fracturing process is the lack of transparency of chemicals used in the practice. Federal laws mandating hydraulic companies to disclose fracturing fluid composition and concentration not only to federal and state regulatory agencies but also to health care professionals would encourage this practice. The full disclosure of fracturing chemicals will allow future research to fill knowledge gaps for a better understanding of the impacts of hydraulic fracturing on human health and the environment. PMID:24790614

DOE Office of Scientific and Technical Information (OSTI.GOV)

Willis-Richards, J.; Watanable, K.; Yamaguchi, T.

A set of models of HDR systems is presented which attempts to explain the formation and operation of HDR systems using only the in-situ properties of the fractured rock mass, the earth stress field, the engineering intervention applied by way of stimulation and the relative positions and pressures of the well(s). A statistical and rock mechanics description of fractures in low permeability rocks provides the basis for modeling of stimulation, circulation and water loss in HDR systems. The model uses a large number of parameters, chiefly simple directly measurable quantities, describing the rock mass and fracture system. The effect ofmore » stimulation (raised fluid pressure allowing slip) on fracture apertures is calculated, and the volume of rock affected per volume of fluid pumped estimated. The total rock volume affected by stimulation is equated with the rock volume containing the associated AE (microseismicity). The aperture and compliance properties of the stimulated fractures are used to estimate impedance and flow within the reservoir. Fluid loss from the boundary of the stimulated volume is treated using radial leak-off with pressure-dependent permeability.« less

Numerical modeling of coupled variably saturated fluid flow and reactive transport with fast and slow chemical reactions

NASA Astrophysics Data System (ADS)

Yeh, Gour-Tsyh (George); Siegel, Malcolm D.; Li, Ming-Hsu

2001-02-01

The couplings among chemical reaction rates, advective and diffusive transport in fractured media or soils, and changes in hydraulic properties due to precipitation and dissolution within fractures and in rock matrix are important for both nuclear waste disposal and remediation of contaminated sites. This paper describes the development and application of LEHGC2.0, a mechanistically based numerical model for simulation of coupled fluid flow and reactive chemical transport, including both fast and slow reactions in variably saturated media. Theoretical bases and numerical implementations are summarized, and two example problems are demonstrated. The first example deals with the effect of precipitation/dissolution on fluid flow and matrix diffusion in a two-dimensional fractured media. Because of the precipitation and decreased diffusion of solute from the fracture into the matrix, retardation in the fractured medium is not as large as the case wherein interactions between chemical reactions and transport are not considered. The second example focuses on a complicated but realistic advective-dispersive-reactive transport problem. This example exemplifies the need for innovative numerical algorithms to solve problems involving stiff geochemical reactions.

Thermal single-well injection-withdrawal tracer tests for determining fracture-matrix heat transfer area

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pruess, K.; Doughty, C.

2010-01-15

Single-well injection-withdrawal (SWIW) tracer tests involve injection of traced fluid and subsequent tracer recovery from the same well, usually with some quiescent time between the injection and withdrawal periods. SWIW are insensitive to variations in advective processes that arise from formation heterogeneities, because upon withdrawal, fluid parcels tend to retrace the paths taken during injection. However, SWIW are sensitive to diffusive processes, such as diffusive exchange of conservative or reactive solutes between fractures and rock matrix. This paper focuses on SWIW tests in which temperature itself is used as a tracer. Numerical simulations demonstrate the sensitivity of temperature returns tomore » fracture-matrix interaction. We consider thermal SWIW response to the two primary reservoir improvements targeted with stimulation, (1) making additional fractures accessible to injected fluids, and (2) increasing the aperture and permeability of pre-existing fractures. It is found that temperature returns in SWIW tests are insensitive to (2), while providing a strong signal of more rapid temperature recovery during the withdrawal phase for (1).« less

Experimental determination of drag coefficients in low-density polyurethane foam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adams, M L

2006-04-18

We describe several experiments performed at the LLNL Site 300 firing range and on the LLNL 1/3 scale gun to investigate the deceleration of small projectiles (l {approx} 3-5 [mm]) in low-density foam ({rho} {approx} 0.08-0.32 [g/cm{sup 3}]). The experiments at the firing range researched a passive velocity diagnostic based on Faraday's law of induction, while experiments on the 1/3 scale gun investigated the effects of varying projectile surface area, projectile shape, and foam density on the drag coefficient c{sub d}. Analysis shows that the velocity diagnostic has an uncertainty on the order of 1 percent for projectiles with velocitymore » v {approx} 0.8-1.2 [km/s]. The 1/3 scale gun experiments, dubbed the Krispy Kreme series, included nine shots considering the combinations of 3 projectile surface areas with 3 target densities. The experiments used Tantalum square surface area block projectiles (with an initial velocity v{sub 0} {approx} 1.2 [km/s], a common thickness T = 2.67 [mm], and square side lengths of 3, 4, and 5 [mm]) decelerating in polyurethane foams (with densities {rho}{sub f} of 0.08, 0.16 and 0.32 [g/cm{sup 3}]). Standard fluid models of the Krispy Kreme experiments predict Reynolds numbers Re {approx} 10{sup 5} - 10{sup 6}, Mach numbers Ma {approx} 0.5-2.0, and drag coefficients c{sub d} {approx} 2-3. However, the data indicate that c{sub d} = 1.1-1.2 (c{sub d} = 1.7) for all three block projectiles in the 0.08 and 0.16 [g/cm{sup 3}] targets (0.32 [g/cm{sup 3}] target). First, we conclude that the drag force on projectiles in solid polyurethane foam is less than in fluids with equivalent dimensionless parameters. This result is also supported by an additional Krispy Kreme experiment that used a disk projectile (with diameter d = 4.51 [mm] and thickness T = 2.67 [mm]) penetrating a target with density {rho} = 0.16 [g/cm{sup 3}], i.e., the fluid-like c{sub d} = 1.15 while the measured c{sub d} = 0.63. Second, we conclude that the measured drag coefficient in the lower density foam targets is less than in the larger density foam target. This result is corroborated by firing range experiments with M855 NATO bullets (with diameter 5.56 [mm], mass 4.1 [g], and initial velocity {nu}{sub 0} {approx} 800 [m/s]) fired from an M16 rifle, i.e., c{sub d} = 0.3 (c{sub d} = 0.6) in the 0.16 [g/cm{sup 3}] (0.32 [g/cm{sup 3}]) target. We propose future 1/3 scale gun experiments using a passive velocity diagnostic with increased spatial resolution as well as simple spherical projectiles with 0.5 and 1.0 [cm] diameters.« less

Seismic properties of fluid bearing formations in magmatic geothermal systems: can we directly detect geothermal activity with seismic methods?

NASA Astrophysics Data System (ADS)

Grab, Melchior; Scott, Samuel; Quintal, Beatriz; Caspari, Eva; Maurer, Hansruedi; Greenhalgh, Stewart

2016-04-01

Seismic methods are amongst the most common techniques to explore the earth's subsurface. Seismic properties such as velocities, impedance contrasts and attenuation enable the characterization of the rocks in a geothermal system. The most important goal of geothermal exploration, however, is to describe the enthalpy state of the pore fluids, which act as the main transport medium for the geothermal heat, and to detect permeable structures such as fracture networks, which control the movement of these pore fluids in the subsurface. Since the quantities measured with seismic methods are only indirectly related with the fluid state and the rock permeability, the interpretation of seismic datasets is difficult and usually delivers ambiguous results. To help overcome this problem, we use a numerical modeling tool that quantifies the seismic properties of fractured rock formations that are typically found in magmatic geothermal systems. We incorporate the physics of the pore fluids, ranging from the liquid to the boiling and ultimately vapor state. Furthermore, we consider the hydromechanics of permeable structures at different scales from small cooling joints to large caldera faults as are known to be present in volcanic systems. Our modeling techniques simulate oscillatory compressibility and shear tests and yield the P- and S-wave velocities and attenuation factors of fluid saturated fractured rock volumes. To apply this modeling technique to realistic scenarios, numerous input parameters need to be indentified. The properties of the rock matrix and individual fractures were derived from extensive literature research including a large number of laboratory-based studies. The geometries of fracture networks were provided by structural geologists from their published studies of outcrops. Finally, the physical properties of the pore fluid, ranging from those at ambient pressures and temperatures up to the supercritical conditions, were taken from the fluid physics literature. The results of this study allow us to describe the seismic properties as a function of hydrothermal and geological features. We use it in a forward seismic modeling study to examine how the seismic response changes with temporally and/or spatially varying fluid properties.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malin, Peter E.; Shalev, Eylon; Onacha, Stepthen A.

In this final report, we discuss both theoretical and applied research resulting from our DOE project, ICEKAP 2004: A Collaborative Joint Geophysical Imaging Project at Krafla and IDDP. The abstract below begins with a general discussion of the problem we addressed: the location and characterization of “blind” geothermal resources using microearthquake and magnetotelluric measurements. The abstract then describes the scientific results and their application to the Krafla geothermal area in Iceland. The text following this abstract presents the full discussion of this work, in the form of the PhD thesis of Stephen A. Onacha. The work presented here was awardedmore » the “Best Geophysics Paper” at the 2005 Geothermal Resources Council meeting, Reno. This study presents the modeling of buried fault zones using microearthquake and electrical resistivity data based on the assumptions that fluid-filled fractures cause electrical and seismic anisotropy and polarization. In this study, joint imaging of electrical and seismic data is used to characterize the fracture porosity of the fracture zones. P-wave velocity models are generated from resistivity data and used in locating microearthquakes. Fracture porosity controls fluid circulation in the hydrothermal systems and the intersections of fracture zones close to the heat source form important upwelling zones for hydrothermal fluids. High fracture porosity sites occur along fault terminations, fault-intersection areas and fault traces. Hydrothermal fault zone imaging using resistivity and microearthquake data combines high-resolution multi-station seismic and electromagnetic data to locate rock fractures and the likely presence fluids in high temperature hydrothermal systems. The depths and locations of structural features and fracture porosity common in both the MT and MEQ data is incorporated into a joint imaging scheme to constrain resistivity, seismic velocities, and locations of fracture systems. The imaging of the fault zones is constrained by geological, drilling, and geothermal production data. The objective is to determine interpretation techniques for evaluating structural controls of fluid circulation in hydrothermal systems. The conclusions are: • directions of MT polarization and anisotropy and MEQ S-splitting correlate. Polarization and anisotropy are caused by fluid filled fractures at the base of the clay cap. •Microearthquakes occur mainly on the boundary of low resistivity within the fracture zone and high resistivity in the host rock. Resistivity is lowest within the core of the fracture zone and increases towards the margins of the fracture zone. The heat source and the clay cap for the hydrothermal have very low resistivity of less than 5Ωm. •Fracture porosity imaged by resistivity indicates that it varies between 45-5% with most between 10-20%, comparable to values from core samples in volcanic areas in Kenya and Iceland. For resistivity values above 60Ωm, the porosity reduces drastically and therefore this might be used as the upper limit for modeling fracture porosity from resistivity. When resistivity is lower than 5Ωm, the modeled fracture porosity increases drastically indicating that this is the low resistivity limit. This is because at very low resistivity in the heat source and the clay cap, the resistivity is dominated by ionic conduction rather than fracture porosity. •Microearthquakes occur mainly above the heat source which is defined by low resistivity at a depth of 3-4.5 km at the Krafla hydrothermal system and 4-7 km in the Longonot hydrothermal system. •Conversions of S to P waves occur for microearthquakes located above the heat source within the hydrothermal system. Shallow microearthquakes occur mainly in areas that show both MT and S-wave anisotropy. •S-wave splitting and MT anisotropy occurs at the base of the clay cap and therefore reflects the variations in fracture porosity on top of the hydrothermal system. •In the Krafla hydrothermal system in Iceland, both MT polarization and MEQ splitting directions align with zones that have high fracture porosity below the clay cap. These zones coincide with fault zones trending in the NNE-SSW and NW-SE directions in otherwise uniform volcanic rocks and laterally continuous geology. The NW-SE orientation is parallel to the regional shear fractures while the NNE-SSW trending polarizations align parallel to rift zone fracture swarms. This suggest that correlations between MT polarizations and MEQ splitting may be related to fluid filled fractures. •In areas of high resistivity (60Ωm), the P-wave velocity approaches that of the rock matrix. •S-wave splitting polarization is determined from measurements of angles of rotation to get the optimum direction of polarization. •The use of MEQ and resistivity for imaging fractures requires that the MEQ data acquisition system be located close to the fracture zone.« less

Acute management and outcome of multiple trauma patients with pelvic disruptions

PubMed Central

2012-01-01

Introduction Data on prehospital and trauma-room fluid management of multiple trauma patients with pelvic disruptions are rarely reported. Present trauma algorithms recommend early hemorrhage control and massive fluid resuscitation. By matching the German Pelvic Injury Register (PIR) with the TraumaRegister DGU (TR) for the first time, we attempt to assess the initial fluid management for different Tile/OTA types of pelvic-ring fractures. Special attention was given to the patient's posttraumatic course, particularly intensive care unit (ICU) data and patient outcome. Methods A specific match code was applied to identify certain patients with pelvic disruptions from both PIR and TR anonymous trauma databases, admitted between 2004 and 2009. From the resulting intersection set, a retrospective analysis was done of prehospital and trauma-room data, length of ICU stay, days of ventilation, incidence of multiple organ dysfunction syndrome (MODS), sepsis, and mortality. Results In total, 402 patients were identified. Mean ISS was 25.9 points, and the mean of patients with ISS ≥16 was 85.6%. The fracture distribution was as follows: 19.7% type A, 29.4% type B, 36.6% type C, and 14.3% isolated acetabular and/or sacrum fractures. The type B/C, compared with type A fractures, were related to constantly worse vital signs that necessitated a higher volume of fluid and blood administration in the prehospital and/or the trauma-room setting. This group of B/C fractures were also related to a significantly higher presence of concomitant injuries and related to increased ISS. This was related to increased ventilation and ICU stay, increased rate of MODS, sepsis, and increased rate of mortality, at least for the type C fractures. Approximately 80% of the dead had sustained type B/C fractures. Conclusions The present study confirms the actuality of traditional trauma algorithms with initial massive fluid resuscitation in the recent therapy of multiple trauma patients with pelvic disruptions. Low-volume resuscitation seems not yet to be accepted in practice in managing this special patient entity. Mechanically unstable pelvic-ring fractures type B/C (according to the Tile/OTA classification) form a distinct entity that must be considered notably in future trauma algorithms. PMID:22913820

Fracture Flow Characterization from Seismic and Electric Properties: Insight from Experimental and Numerical Approaches

NASA Astrophysics Data System (ADS)

Sawayama, K.; Kitamura, K.; Tsuji, T.; Fujimitsu, Y.

2017-12-01

The estimation of fluid flow and its distribution in the fracture is essential to evaluate subsurface fluid (e.g., geothermal water, ground water, oil and gas). Recently, fluid flow in the geothermal reservoir has been attracting attention to develop EGS (enhanced geothermal system) technique. To detect the fluid distribution under the ground, geophysical exploration such as seismic and electromagnetic methods have been broadly applied. For better interpretation of these exploration data, more detailed investigation about the effect of fluid on seismic and electric properties of fracture is required. In this study, we measured and calculated seismic and electric properties of a cracked rock to discuss the effect of water distribution and saturation on them as well as fluid flow. For the experimental observation, we developed the technique to measure electrical impedance, P-wave velocity and water saturation simultaneously during the fluid-flow test. The test has been conducted as follows; a cracked andesite core sample was filled with nitrogen gas (Pp = 10 MPa) under 20 MPa of confining pressure and then, brine (1wt.%-KCl, 1.75 S/m) was injected into the sample to replace the gas. During the test, water saturation, permeability, electrical impedance and P-wave velocity were measured. As a result of this experimental study, electrical impedance dramatically decreased from 105 to 103 Ω and P-wave velocity increased by 2% due to the brine injection. This remarkable change of the electrical impedance could be due to the replacement of pre-filled nitrogen gas to the brine in the broad fracture. After the brine injection, electrical impedance decreased with injection pressure by up to 40% while P-wave velocity was almost constant. This decrease of electrical impedance could be related to the flow to the narrow path (microcrack) which cannot be detected by P-wave velocity. These two types of fluid flow mechanism were also suggested from other parameters such as permeability, water saturation and saturation exponent of Archie's law. To quantify the fluid flow and its distribution in the fracture, we applied fluid flow simulation by LBM (Lattice Boltzmann Method). From this result, we calculate physical parameters by FEM and FDM and then discuss effect of fluid on them as well as their comparison with experimental results.

Long-period long-duration seismic events during hydraulic fracturing: Implications for tensile fracture development

NASA Astrophysics Data System (ADS)

Hu, Hongru; Li, Aibing; Zavala-Torres, Ricardo

2017-05-01

Long-period long-duration (LPLD) seismic events are observed from a microseismic data set acquired by surface receivers in the Eagle Ford Shale. These events are characterized by low frequencies of 10-60 Hz and long durations of 30-60 s. The seismograms are dominated with P waves, and the frequency spectra have peaks at several isolated frequencies, similar to volcanic tremors. The LPLD events are located close to the horizontal hydraulic treatment well and migrate away from the well with time. These observations suggest that the LPLD events are related to hydraulic fracturing and are possibly caused by the jerky opening and resonance of fluid-filled cracks. Imaging this type of LPLD events can potentially map fluid flow and tensile fracture development during hydraulic fracturing.

Astronaut Mike Fincke Conducts Fluid Merging Viscosity Measurement (FMVM) Experiment

NASA Technical Reports Server (NTRS)

2004-01-01

Astronaut Mike Fincke places droplets of honey onto the strings for the Fluid Merging Viscosity Measurement (FMVM) investigation onboard the International Space Station (ISS). The FMVM experiment measures the time it takes for two individual highly viscous fluid droplets to coalesce or merge into one droplet. Different fluids and droplet size combinations were tested in the series of experiments. By using the microgravity environment, researchers can measure the viscosity or 'thickness' of fluids without the influence of containers and gravity using this new technique. Understanding viscosity could help scientists understand industrially important materials such as paints, emulsions, polymer melts and even foams used to produce pharmaceutical, food, and cosmetic products.

Fluid-structure coupling for wind turbine blade analysis using OpenFOAM

NASA Astrophysics Data System (ADS)

Dose, Bastian; Herraez, Ivan; Peinke, Joachim

2015-11-01

Modern wind turbine rotor blades are designed increasingly large and flexible. This structural flexibility represents a problem for the field of Computational Fluid Dynamics (CFD), which is used for accurate load calculations and detailed investigations of rotor aerodynamics. As the blade geometries within CFD simulations are considered stiff, the effect of blade deformation caused by aerodynamic loads cannot be captured by the common CFD approach. Coupling the flow solver with a structural solver can overcome this restriction and enables the investigation of flexible wind turbine blades. For this purpose, a new Finite Element (FE) solver was implemented into the open source CFD code OpenFOAM. Using a beam element formulation based on the Geometrically Exact Beam Theory (GEBT), the structural model can capture geometric non-linearities such as large deformations. Coupled with CFD solvers of the OpenFOAM package, the new framework represents a powerful tool for aerodynamic investigations. In this work, we investigated the aerodynamic performance of a state of the art wind turbine. For different wind speeds, aerodynamic key parameters are evaluated and compared for both, rigid and flexible blade geometries. The present work is funded within the framework of the joint project Smart Blades (0325601D) by the German Federal Ministry for Economic Affairs and Energy (BMWi) under decision of the German Federal Parliament.

Fracture, fluid flow and paleostress at Sunrise Dam Gold Mine, W. Australia

NASA Astrophysics Data System (ADS)

Blenkinsop, Thomas; Sanderson, David; Nugus, Michael

2017-04-01

Some of the clearest examples of Interactions between fracture, fluid flow, pore fluid pressure and differential stress can be inferred from underground observations in mines. This study examines the inferred stress conditions and resulting fracture network that constitutes a stockwork type ore body at Sunrise Dam gold mine, Western Australia. Stockworks in mine workings are particularly instructive for such analyses, because the abundance of veins allows cross-cutting relationships to be observed, which are commonly hard to see in situations of lower fracture intensity or incomplete outcrop. Sunrise Dam has produced in excess of 8.5Moz of gold since 1989, with current Mineral Resources and Ore Reserves at 58.96Mt@2.41g/t Au (4.55Moz) and 21.45Mt@1.87g/t Au (1.29Moz), respectively. The stockwork examined is in the Astro ore body, and consists of three sets of extensional veins and one set of low-angle strike-slip shear veins. Cross-cutting relationships suggest broadly contemporaneous formation of all fracture sets, which are also related by a common quartz-carbonate mineralogy. The extensional veins intersect the shear veins along the direction of shear, a geometry that can be predicted for certain stress ratios. Combined with observations and paleostress inferences from other parts of the mine, the veining and gold mineralisation can be associated with a D4 strike-slip shearing event, which had a maximum compressive stress plunging gently NE. Fracture intensity varies by 50% on a scale of 10s of metres. The stockwork formed by repeated extensional and shear failure events, showing fluctuations in pore fluid pressure and stress conditions, which would have required fracture healing/sealing in order for the deformation to spread throughout the stockwork volume.

Stimuli Responsive/Rheoreversible Hydraulic Fracturing Fluids for Enhanced Geothermal Energy Production (Part I)

NASA Astrophysics Data System (ADS)

Fernandez, C. A.; Jung, H. B.; Shao, H.; Bonneville, A.; Heldebrant, D.; Hoyt, D.; Zhong, L.; Holladay, J.

2014-12-01

Cost-effective yet safe creation of high-permeability reservoirs inside deep crystalline bedrock is the primary challenge for the viability of enhanced geothermal systems and unconventional oil/gas recovery. Current reservoir stimulation processes utilize brute force (hydraulic pressures in the order of hundreds of bar) to create/propagate fractures in the bedrock. Such stimulation processes entail substantial economic costs ($3.3 million per reservoir as of 2011). Furthermore, the environmental impacts of reservoir stimulation are only recently being determined. Widespread concerns about the environmental contamination have resulted in a number of regulations for fracturing fluids advocating for greener fracturing processes. To reduce the costs and environmental impact of reservoir stimulation, we developed an environmentally friendly and recyclable hydraulic fracturing fluid that undergoes a controlled and large volume expansion with a simultaneous increase in viscosity triggered by CO2 at temperatures relevant for reservoir stimulation in Enhanced Geothermal System (EGS). The volume expansion, which will specifically occurs at EGS depths of interest, generates an exceptionally large mechanical stress in fracture networks of highly impermeable rock propagating fractures at effective stress an order of magnitude lower than current technology. This paper will concentrate on the presentation of this CO2-triggered expanding hydrogel formed from diluted aqueous solutions of polyallylamine (PAA). Aqueous PAA-CO2 mixtures also show significantly higher viscosities than conventional rheology modifiers at similar pressures and temperatures due to the cross-linking reaction of PAA with CO2, which was demonstrated by chemical speciation studies using in situ HP-HT 13C MAS-NMR. In addtion, PAA shows shear-thinning behavior, a critical advantage for the use of this fluid system in EGS reservoir stimulation. The high pressure/temperature experiments and their results as well as the CFD modeling are presented in a companion paper.

Mapping Fluid Injection and Associated Induced Seismicity Using InSAR Analysis

NASA Astrophysics Data System (ADS)

Thorpe, S. D.; Tiampo, K. F.

2016-12-01

In recent years there has been a rise in unconventional oil and gas production in western North America which has been coupled with an increase in the number of earthquakes recorded in these regions, commonly referred to as "induced seismicity" (Ellsworth, 2013). As fluid is pumped into the subsurface during hydraulic fracturing or fluid disposal, the state of stress within the subsurface changes, potentially reactivating pre-existing faults and/or causing subsidence or uplift of the surface. This anthropogenic surface deformation also provides significant hazard to communities and structures surrounding these hydraulic fracturing or fluid disposal sites (Barnhart et al., 2014; Shirzaei et al., 2016). This study aims to relate, both spatially and temporally, this surface deformation to hydraulic fracturing and fluid disposal operations in Alberta (AB) and British Columbia (BC) using Differential Interferometric Synthetic Aperture Radar (InSAR) analysis. Satellite-based geodetic methods such as InSAR provide frequent measurements of ground deformation at high spatial resolution. Based on locations of previously identified induced seismicity in areas throughout AB and BC, images were acquired for multiple locations from the Canadian RADARSAT-2 satellite, including Fort St. John and Fox Creek, AB (Atkinson et al., 2016). Using advanced processing techniques, these images then were stacked to generate coherent interferograms. We present results from this processing as a set of time series that are correlated with both hydraulic fracturing and fluid disposal sites at each location. These results reveal the temporal and spatial relationship between well injection activity and associated induced seismicity in western Canada. Future work will utilise these time series to model subsurface fluid flow, providing important information regarding the nature of the subsurface structure and associated aquifer due to fluid injection and withdrawal.

Modeling Studies to Constrain Fluid and Gas Migration Associated with Hydraulic Fracturing Operations

NASA Astrophysics Data System (ADS)

Rajaram, H.; Birdsell, D.; Lackey, G.; Karra, S.; Viswanathan, H. S.; Dempsey, D.

2015-12-01

The dramatic increase in the extraction of unconventional oil and gas resources using horizontal wells and hydraulic fracturing (fracking) technologies has raised concerns about potential environmental impacts. Large volumes of hydraulic fracturing fluids are injected during fracking. Incidents of stray gas occurrence in shallow aquifers overlying shale gas reservoirs have been reported; whether these are in any way related to fracking continues to be debated. Computational models serve as useful tools for evaluating potential environmental impacts. We present modeling studies of hydraulic fracturing fluid and gas migration during the various stages of well operation, production, and subsequent plugging. The fluid migration models account for overpressure in the gas reservoir, density contrast between injected fluids and brine, imbibition into partially saturated shale, and well operations. Our results highlight the importance of representing the different stages of well operation consistently. Most importantly, well suction and imbibition both play a significant role in limiting upward migration of injected fluids, even in the presence of permeable connecting pathways. In an overall assessment, our fluid migration simulations suggest very low risk to groundwater aquifers when the vertical separation from a shale gas reservoir is of the order of 1000' or more. Multi-phase models of gas migration were developed to couple flow and transport in compromised wellbores and subsurface formations. These models are useful for evaluating both short-term and long-term scenarios of stray methane release. We present simulation results to evaluate mechanisms controlling stray gas migration, and explore relationships between bradenhead pressures and the likelihood of methane release and transport.

Studying physical properties of deformed intact and fractured rocks by micro-scale hydro-mechanical-seismicity model

NASA Astrophysics Data System (ADS)

Raziperchikolaee, Samin

The pore pressure variation in an underground formation during hydraulic stimulation of low permeability formations or CO2 sequestration into saline aquifers can induce microseismicity due to fracture generation or pre-existing fracture activation. While the analysis of microseismic data mainly focuses on mapping the location of fractures, the seismic waves generated by the microseismic events also contain information for understanding of fracture mechanisms based on microseismic source analysis. We developed a micro-scale geomechanics, fluid-flow and seismic model that can predict transport and seismic source behavior during rock failure. This model features the incorporation of microseismic source analysis in fractured and intact rock transport properties during possible rock damage and failure. The modeling method considers comprehensive grains and cements interaction through a bonded-particle-model. As a result of grain deformation and microcrack development in the rock sample, forces and displacements in the grains involved in the bond breakage are measured to determine seismic moment tensor. In addition, geometric description of the complex pore structure is regenerated to predict fluid flow behavior of fractured samples. Numerical experiments are conducted for different intact and fractured digital rock samples, representing various mechanical behaviors of rocks and fracture surface properties, to consider their roles on seismic and transport properties of rocks during deformation. Studying rock deformation in detail provides an opportunity to understand the relationship between source mechanism of microseismic events and transport properties of damaged rocks to have a better characterizing of fluid flow behavior in subsurface formations.

A Microfluidics Study to Quantify the Impact of Microfracture Properties on Two-Phase Flow in Tight Rocks

NASA Astrophysics Data System (ADS)

Mehmani, A.; Kelly, S. A.; Torres-Verdin, C.; Balhoff, M.

2017-12-01

Microfluidics provides the opportunity for controlled experiments of immiscible fluid dynamics in quasi two-dimensional permeable media and allows their direct observation. We leverage microfluidics to investigate the impact of microfracture properties on water imbibition and drainage in a porous matrix. In the context of this work, microfractures are defined as apertures or preferential flow paths formed along planes of weakness, such as between two different rock fabrics. Patterns of pseudo-microfractures with orientations from parallel and perpendicular to fluid flow as well as variations in their connectivity were fabricated in glass micromodels; surface roughness of the micromodels was also varied utilizing a new method. Light microscopy and image analysis were used to quantify transient front advancement and trapped non-wetting phase saturation during imbibition as well as residual wetting phase saturation and its spatial distribution following drainage. Our experiments enable the assessment of quantitative relationships between fluid invasion rate and residual phase distributions as functions of microfracture network properties. Ultimately, the wide variety of microfluidic experiments performed in this study provide valuable insight into two-phase fluid dynamics in microfracture/matrix networks, the extent of fracture fluid invasion, and the saturation of trapped phases. In reservoir description, the geometries of subsurface fractures are often difficult to ascertain, but the distribution of rock types in a zone, from highly laminated to homogenous, can be reliably assessed with core data and well logs. Assuming that microcracks are functions of lamination planes (thin beds), then a priori predictions of the effect of microcracks on two-phase fluid flow across various geological conditions can possibly be upscaled via effective lamination properties. Such upscaling can significantly reduce the uncertainties associated with subsurface operations, including reservoir production, carbon storage and sequestration, and hazardous waste sequestration. A reliable prediction of capillary trapping, for instance, can determine the fracture fluid saturation subsequent to hydraulic fracturing of unconventional formations or the efficacy of water flooding in fractured reservoirs.

Using Fully Coupled Hydro-Geomechanical Numerical Test Bed to Study Reservoir Stimulation with Low Hydraulic Pressure

DOE Data Explorer

Fu, Pengcheng; Johnson, Scott M.; Carrigan, Charles R.

2012-01-31

This paper documents our effort to use a fully coupled hydro-geomechanical numerical test bed to study using low hydraulic pressure to stimulate geothermal reservoirs with existing fracture network. In this low pressure stimulation strategy, fluid pressure is lower than the minimum in situ compressive stress, so the fractures are not completely open but permeability improvement can be achieved through shear dilation. We found that in this low pressure regime, the coupling between the fluid phase and the rock solid phase becomes very simple, and the numerical model can achieve a low computational cost. Using this modified model, we study the behavior of a single fracture and a random fracture network.

Scaling of the flow-stiffness relationship in weakly correlated single fractures

NASA Astrophysics Data System (ADS)

Petrovitch, Christopher L.

The remote characterization of the hydraulic properties of fractures in rocks is important in many subsurface projects. Fractures create uncertainty in the hydraulic properties of the subsurface in that their topology controls the amount of flow that can occur in addition to that from the matrix. In turn, the fracture topology is also affected by stress which alters the topology as the stress changes directly. This alteration of fracture topology with stress is captured by fracture specific stiffness. The specific stiffness of a single fracture can be remotely probed from the attenuation and velocity of seismic waves. The hydromechanical coupling of single fractures, i.e. the relationship between flow and stiffness, holds the key to finding a method to remotely characterize a fractures hydraulic properties. This thesis is separated into two parts: (1) a description of the hydromechanical coupling of fractures based on numerical models used to generate synthetic fractures, compute the flow through a fracture, and deform fracture topologies to unravel the scaling function that is fundamental to the hydromechanical coupling of single fractures; (2) a Discontinuous Galerkin (DG) method was developed to accurately simulate the scattered seismic waves from realistic fracture topologies. The scaling regimes of fluid flow and specific stiffness in weakly correlated fractures are identified by using techniques from Percolation Theory and initially treating the two processes separately. The fixed points associated with fluid flow were found to display critical scaling while the fixed points for specific stiffness were trivial. The two processes could be indirectly related because the trivial scaling of the mechanical properties allowed the specific stiffness to be used as surrogate to the void area fraction. The dynamic transport exponent was extracted at threshold by deforming fracture geometries within the effective medium regime (near the ``cubic law'' regime) to the critical regime. From this, a scaling function was defined for the hydromechanical coupling. This scaling function provides the link between fluid flow and fracture specific stiffness so that seismic waves may be used to remotely probe the hydraulic properties of fractures. Then, the DG method is shown to be capable of measuring such fracture specific stiffnesses by numerically measuring the velocity of interface waves when propagated across laboratory measured fracture geometries of Austin Chalk.

Variations of permeability and pore size distribution of porous media with pressure.

PubMed

Chen, Quan; Kinzelbach, Wolfgang; Ye, Chaohui; Yue, Yong

2002-01-01

Porosity and permeability of porous and fractured geological media decrease with the exploitation of formation fluids such as petroleum, natural gas, or ground water. This may result in ground subsidence and a decrease of recovery of petroleum, natural gas, or ground water. Therefore, an evaluation of the behavior of permeability and porosity under formation fluid pressure changes is important to petroleum and ground water industries. This study for the first time establishes a method, which allows for the measurement of permeability, porosity, and pore size distribution of cores simultaneously. From the observation of the pore size distribution by low-field nuclear magnetic resonance (NMR) relaxation time spectrometry the mechanisms of pressure-dependent porosity and permeability change can be derived. This information cannot be obtained by traditional methods. As the large-size pores or fractures contribute significantly to the permeability, their change consequently leads to a large permeability change. The contribution of fractures to permeability is even larger than that of pores. Thus, the permeability of the cores with fractures decreased more than that of cores without fractures during formation pressure decrease. Furthermore, it did not recover during formation pressure increase. It can be concluded that in fractures, mainly plastic deformation takes place, while matrix pores mainly show elastic deformation. Therefore, it is very important to keep an appropriate formation fluid pressure during the exploitation of ground water and petroleum in a fractured formation.

Tuning Interfacial Properties and Processes by Controlling the Rheology and Structure of Poly( N-isopropylacrylamide) Particles at Air/Water Interfaces.

PubMed

Maestro, Armando; Jones, Daniel; Sánchez de Rojas Candela, Carmen; Guzman, Eduardo; Duits, Michel H G; Cicuta, Pietro

2018-06-05

By combining controlled experiments on single interfaces with measurements on solitary bubbles and liquid foams, we show that poly( N-isopropylacrylamide) (PNIPAM) microgels assembled at air/water interfaces exhibit a solid to liquid transition changing the temperature, and that this is associated with the change in the interfacial microstructure of the PNIPAM particles around their volume phase transition temperature. We show that the solid behaves as a soft 2D colloidal glass, and that the existence of this solid/liquid transition offers an ideal platform to tune the permeability of air bubbles covered by PNIPAM and to control macroscopic foam properties such as drainage, stability, and foamability. PNIPAM particles on fluid interfaces allow new tunable materials, for example foam structures with variable mechanical properties upon small temperature changes.

Material Science

NASA Image and Video Library

2004-07-03

Astronaut Mike Fincke places droplets of honey onto the strings for the Fluid Merging Viscosity Measurement (FMVM) investigation onboard the International Space Station (ISS). The FMVM experiment measures the time it takes for two individual highly viscous fluid droplets to coalesce or merge into one droplet. Different fluids and droplet size combinations were tested in the series of experiments. By using the microgravity environment, researchers can measure the viscosity or "thickness" of fluids without the influence of containers and gravity using this new technique. Understanding viscosity could help scientists understand industrially important materials such as paints, emulsions, polymer melts and even foams used to produce pharmaceutical, food, and cosmetic products.

Material Science

NASA Image and Video Library

2004-07-12

Astronaut Mike Fincke places droplets of honey onto the strings for the Fluid Merging Viscosity Measurement (FMVM) investigation onboard the International Space Station (ISS). The FMVM experiment measures the time it takes for two individual highly viscous fluid droplets to coalesce or merge into one droplet. Different fluids and droplet size combinations were tested in the series of experiments. By using the microgravity environment, researchers can measure the viscosity or "thickness" of fluids without the influence of containers and gravity using this new technique. Understanding viscosity could help scientists understand industrially important materials such as paints, emulsions, polymer melts and even foams used to produce pharmaceutical, food, and cosmetic products.

Fracturing of doleritic intrusions and associated contact zones: Implications for fluid flow in volcanic basins

NASA Astrophysics Data System (ADS)

Senger, Kim; Buckley, Simon J.; Chevallier, Luc; Fagereng, Åke; Galland, Olivier; Kurz, Tobias H.; Ogata, Kei; Planke, Sverre; Tveranger, Jan

2015-02-01

Igneous intrusions act as both carriers and barriers to subsurface fluid flow and are therefore expected to significantly influence the distribution and migration of groundwater and hydrocarbons in volcanic basins. Given the low matrix permeability of igneous rocks, the effective permeability in- and around intrusions is intimately linked to the characteristics of their associated fracture networks. Natural fracturing is caused by numerous processes including magma cooling, thermal contraction, magma emplacement and mechanical disturbance of the host rock. Fracturing may be locally enhanced along intrusion-host rock interfaces, at dyke-sill junctions, or at the base of curving sills, thereby potentially enhancing permeability associated with these features. In order to improve our understanding of fractures associated with intrusive bodies emplaced in sedimentary host rocks, we have investigated a series of outcrops from the Karoo Basin of the Eastern Cape province of South Africa, where the siliciclastic Burgersdorp Formation has been intruded by various intrusions (thin dykes, mid-sized sheet intrusions and thick sills) belonging to the Karoo dolerite. We present a quantified analysis of fracturing in- and around these igneous intrusions based on five outcrops at three individual study sites, utilizing a combination of field data, high-resolution lidar virtual outcrop models and image processing. Our results show a significant difference between the three sites in terms of fracture orientation. The observed differences can be attributed to contrasting intrusion geometries, outcrop geometry (for lidar data) and tectonic setting. Two main fracture sets were identified in the dolerite at two of the sites, oriented parallel and perpendicular to the contact respectively. Fracture spacing was consistent between the three sites, and exhibits a higher degree of variation in the dolerites compared to the host rock. At one of the study sites, fracture frequency in the surrounding host rock increases slightly toward the intrusion at approximately 3 m from the contact. We conclude by presenting a conceptual fluid flow model, showing permeability enhancement and a high potential for fluid flow-channeling along the intrusion-host rock interfaces.

Porous media fracturing dynamics: stepwise crack advancement and fluid pressure oscillations

NASA Astrophysics Data System (ADS)

Cao, Toan D.; Hussain, Fazle; Schrefler, Bernhard A.

2018-02-01

We present new results explaining why fracturing in saturated porous media is not smooth and continuous but is a distinct stepwise process concomitant with fluid pressure oscillations. All exact solutions and almost all numerical models yield smooth fracture advancement and fluid pressure evolution, while recent experimental results, mainly from the oil industry, observation from geophysics and a very few numerical results for the quasi-static case indeed reveal the stepwise phenomenon. We summarize first these new experiments and these few numerical solutions for the quasi-static case. Both mechanical loading and pressure driven fractures are considered because their behaviours differ in the direction of the pressure jumps. Then we explore stepwise crack tip advancement and pressure fluctuations in dynamic fracturing with a hydro-mechanical model of porous media based on the Hybrid Mixture Theory. Full dynamic analyses of examples dealing with both hydraulic fracturing and mechanical loading are presented. The stepwise fracture advancement is confirmed in the dynamic setting as well as in the pressure fluctuations, but there are substantial differences in the frequency contents of the pressure waves in the two loading cases. Comparison between the quasi-static and fully dynamic solutions reveals that the dynamic response gives much more information such as the type of pressure oscillations and related frequencies and should be applied whenever there is a doubt about inertia forces playing a role - the case in most fracturing events. In the absence of direct relevant dynamic tests on saturated media some experimental results on dynamic fracture in dry materials, a fast hydraulic fracturing test and observations from geophysics confirm qualitatively the obtained results such as the type of pressure oscillations and the substantial difference in the behaviour under the two loading cases.

Beyond-laboratory-scale prediction for channeling flows through subsurface rock fractures with heterogeneous aperture distributions revealed by laboratory evaluation

NASA Astrophysics Data System (ADS)

Ishibashi, Takuya; Watanabe, Noriaki; Hirano, Nobuo; Okamoto, Atsushi; Tsuchiya, Noriyoshi

2015-01-01

The present study evaluates aperture distributions and fluid flow characteristics for variously sized laboratory-scale granite fractures under confining stress. As a significant result of the laboratory investigation, the contact area in fracture plane was found to be virtually independent of scale. By combining this characteristic with the self-affine fractal nature of fracture surfaces, a novel method for predicting fracture aperture distributions beyond laboratory scale is developed. Validity of this method is revealed through reproduction of the results of laboratory investigation and the maximum aperture-fracture length relations, which are reported in the literature, for natural fractures. The present study finally predicts conceivable scale dependencies of fluid flows through joints (fractures without shear displacement) and faults (fractures with shear displacement). Both joint and fault aperture distributions are characterized by a scale-independent contact area, a scale-dependent geometric mean, and a scale-independent geometric standard deviation of aperture. The contact areas for joints and faults are approximately 60% and 40%. Changes in the geometric means of joint and fault apertures (µm), em, joint and em, fault, with fracture length (m), l, are approximated by em, joint = 1 × 102 l0.1 and em, fault = 1 × 103 l0.7, whereas the geometric standard deviations of both joint and fault apertures are approximately 3. Fluid flows through both joints and faults are characterized by formations of preferential flow paths (i.e., channeling flows) with scale-independent flow areas of approximately 10%, whereas the joint and fault permeabilities (m2), kjoint and kfault, are scale dependent and are approximated as kjoint = 1 × 10-12 l0.2 and kfault = 1 × 10-8 l1.1.

A numerical approach for assessing effects of shear on equivalent permeability and nonlinear flow characteristics of 2-D fracture networks

NASA Astrophysics Data System (ADS)

Liu, Richeng; Li, Bo; Jiang, Yujing; Yu, Liyuan

2018-01-01

Hydro-mechanical properties of rock fractures are core issues for many geoscience and geo-engineering practices. Previous experimental and numerical studies have revealed that shear processes could greatly enhance the permeability of single rock fractures, yet the shear effects on hydraulic properties of fractured rock masses have received little attention. In most previous fracture network models, single fractures are typically presumed to be formed by parallel plates and flow is presumed to obey the cubic law. However, related studies have suggested that the parallel plate model cannot realistically represent the surface characters of natural rock fractures, and the relationship between flow rate and pressure drop will no longer be linear at sufficiently large Reynolds numbers. In the present study, a numerical approach was established to assess the effects of shear on the hydraulic properties of 2-D discrete fracture networks (DFNs) in both linear and nonlinear regimes. DFNs considering fracture surface roughness and variation of aperture in space were generated using an originally developed code DFNGEN. Numerical simulations by solving Navier-Stokes equations were performed to simulate the fluid flow through these DFNs. A fracture that cuts through each model was sheared and by varying the shear and normal displacements, effects of shear on equivalent permeability and nonlinear flow characteristics of DFNs were estimated. The results show that the critical condition of quantifying the transition from a linear flow regime to a nonlinear flow regime is: 10-4 〈 J < 10-3, where J is the hydraulic gradient. When the fluid flow is in a linear regime (i.e., J < 10-4), the relative deviation of equivalent permeability induced by shear, δ2, is linearly correlated with J with small variations, while for fluid flow in the nonlinear regime (J 〉 10-3), δ2 is nonlinearly correlated with J. A shear process would reduce the equivalent permeability significantly in the orientation perpendicular to the sheared fracture as much as 53.86% when J = 1, shear displacement Ds = 7 mm, and normal displacement Dn = 1 mm. By fitting the calculated results, the mathematical expression for δ2 is established to help choose proper governing equations when solving fluid flow problems in fracture networks.

Impact of Casing Expansion on the Mechanical and Petro-Physical Properties of Wellbore Cements

NASA Astrophysics Data System (ADS)

Oyibo, A. E.

2014-12-01

The main objective of this research is to investigate the applicability of expandable casing technology as a remediation technique for leaky wells resulting in gas migration problems. Micro annulus is usually created at the cement-formation/cement-casing interface or within the cement matrix either due to poor primary cementing or as a result of activities such as temperature and pressure variation or fracturing operations. Recent reports on gas migration in hydraulically fractured wellbores, has raised concerns on the contamination of fresh water aquifers resulting from fluid migration though this flow path. A unique bench-scale physical model which utilizes expandable tubulars in the remediation of micro annular gas flow has been used to simulate expansion of a previously-cemented casing under field-like conditions. Three different designs of cement slurry: regular 16.4 lb. /gal, 16.4 lb. /gal base slurry foamed to 13 lb. /gal and 16.4 lb. /gal cement slurry with 10% salt concentration. Gas flow path (microannulus) was artificially created at the pipe-cement interface by rotating the inner pipe in a pipe inside pipe assembly with cement in the annulus within the first few hours of hydration to create debonding at the cement-casing interface. Nitrogen gas flow-through experiments were performed before and after the expansion to confirm the sealing of the microannulus. The results obtained confirmed the effectiveness of this technique in the complete closure of gas leakage path, providing seal-tight cement-formation interface free of microannulus. The manipulation of the cement sheath during the casing expansion resulted in improved porosity, permeability and the strength of the cement sheath. SEM micrographs revealed decrease in pore size and fracturing of unhydrated cement grains within the cement matrix. This technology has great potential to become one of the leading cement remediation techniques for leaks behind the casing if implemented. Keywords: Wellbore Integrity, Casing Expansion, Well Gas Leaks, CSH, Pore Collapse, Cement Pore Water.

Numerical Simulation of Potential Groundwater Contaminant Pathways from Hydraulically Fractured Oil Shale in the Nevada Basin and Range Province

NASA Astrophysics Data System (ADS)

Rybarski, S.; Pohll, G.; Pohlmann, K.; Plume, R.

2014-12-01

In recent years, hydraulic fracturing (fracking) has become an increasingly popular method for extraction of oil and natural gas from tight formations. Concerns have been raised over a number of environmental risks associated with fracking, including contamination of groundwater by fracking fluids, upwelling of deep subsurface brines, and methane migration. Given the potentially long time scale for contaminant transport associated with hydraulic fracturing, numerical modeling remains the best practice for risk assessment. Oil shale in the Humboldt basin of northeastern Nevada has now become a target for hydraulic fracturing operations. Analysis of regional and shallow groundwater flow is used to assess several potential migration pathways specific to the geology and hydrogeology of this basin. The model domain in all simulations is defined by the geologic structure of the basin as determined by deep oil and gas well bores and formation outcrops. Vertical transport of gaseous methane along a density gradient is simulated in TOUGH2, while fluid transport along faults and/or hydraulic fractures and lateral flow through more permeable units adjacent to the targeted shale are modeled in FEFLOW. Sensitivity analysis considers basin, fault, and hydraulic fracturing parameters, and results highlight key processes that control fracking fluid and methane migration and time scales under which it might occur.

A Particle Model for Prediction of Cement Infiltration of Cancellous Bone in Osteoporotic Bone Augmentation.

PubMed

Basafa, Ehsan; Murphy, Ryan J; Kutzer, Michael D; Otake, Yoshito; Armand, Mehran

2013-01-01

Femoroplasty is a potential preventive treatment for osteoporotic hip fractures. It involves augmenting mechanical properties of the femur by injecting Polymethylmethacrylate (PMMA) bone cement. To reduce the risks involved and maximize the outcome, however, the procedure needs to be carefully planned and executed. An important part of the planning system is predicting infiltration of cement into the porous medium of cancellous bone. We used the method of Smoothed Particle Hydrodynamics (SPH) to model the flow of PMMA inside porous media. We modified the standard formulation of SPH to incorporate the extreme viscosities associated with bone cement. Darcy creeping flow of fluids through isotropic porous media was simulated and the results were compared with those reported in the literature. Further validation involved injecting PMMA cement inside porous foam blocks - osteoporotic cancellous bone surrogates - and simulating the injections using our proposed SPH model. Millimeter accuracy was obtained in comparing the simulated and actual cement shapes. Also, strong correlations were found between the simulated and the experimental data of spreading distance (R(2) = 0.86) and normalized pressure (R(2) = 0.90). Results suggest that the proposed model is suitable for use in an osteoporotic femoral augmentation planning framework.

Modeling the Interaction Between Hydraulic and Natural Fractures Using Dual-Lattice Discrete Element Method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Jing; Huang, Hai; Deo, Milind

The interaction between hydraulic fractures (HF) and natural fractures (NF) will lead to complex fracture networks due to the branching and merging of natural and hydraulic fractures in unconventional reservoirs. In this paper, a newly developed hydraulic fracturing simulator based on discrete element method is used to predict the generation of complex fracture network in the presence of pre-existing natural fractures. By coupling geomechanics and reservoir flow within a dual lattice system, this simulator can effectively capture the poro-elastic effects and fluid leakoff into the formation. When HFs are intercepting single or multiple NFs, complex mechanisms such as direct crossing,more » arresting, dilating and branching can be simulated. Based on the model, the effects of injected fluid rate and viscosity, the orientation and permeability of NFs and stress anisotropy on the HF-NF interaction process are investigated. Combined impacts from multiple parameters are also examined in the paper. The numerical results show that large values of stress anisotropy, intercepting angle, injection rate and viscosity will impede the opening of NFs.« less

A Micromechanics Finite Element Model for Studying the Mechanical Behavior of Spray-On Foam Insulation (SOFI)

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Sullivan, Roy M.; Lerch, Bradley A.

2006-01-01

A micromechanics model has been constructed to study the mechanical behavior of spray-on foam insulation (SOFI) for the external tank. The model was constructed using finite elements representing the fundamental repeating unit of the SOFI microstructure. The details of the micromechanics model were based on cell observations and measured average cell dimensions discerned from photomicrographs. The unit cell model is an elongated Kelvin model (fourteen-sided polyhedron with 8 hexagonal and six quadrilateral faces), which will pack to a 100% density. The cell faces and cell edges are modeled using three-dimensional 20-node brick elements. Only one-eighth of the cell is modeled due to symmetry. By exercising the model and correlating the results with the macro-mechanical foam behavior obtained through material characterization testing, the intrinsic stiffness and Poisson s Ratio of the polymeric cell walls and edges are determined as a function of temperature. The model is then exercised to study the unique and complex temperature-dependent mechanical behavior as well as the fracture initiation and propagation at the microscopic unit cell level.

Advanced materials for thermal protection system

NASA Astrophysics Data System (ADS)

Heng, Sangvavann; Sherman, Andrew J.

1996-03-01

Reticulated open-cell ceramic foams (both vitreous carbon and silicon carbide) and ceramic composites (SiC-based, both monolithic and fiber-reinforced) were evaluated as candidate materials for use in a heat shield sandwich panel design as an advanced thermal protection system (TPS) for unmanned single-use hypersonic reentry vehicles. These materials were fabricated by chemical vapor deposition/infiltration (CVD/CVI) and evaluated extensively for their mechanical, thermal, and erosion/ablation performance. In the TPS, the ceramic foams were used as a structural core providing thermal insulation and mechanical load distribution, while the ceramic composites were used as facesheets providing resistance to aerodynamic, shear, and erosive forces. Tensile, compressive, and shear strength, elastic and shear modulus, fracture toughness, Poisson's ratio, and thermal conductivity were measured for the ceramic foams, while arcjet testing was conducted on the ceramic composites at heat flux levels up to 5.90 MW/m2 (520 Btu/ft2ṡsec). Two prototype test articles were fabricated and subjected to arcjet testing at heat flux levels of 1.70-3.40 MW/m2 (150-300 Btu/ft2ṡsec) under simulated reentry trajectories.

Fractured-aquifer hydrogeology from geophysical logs; the passaic formation, New Jersey

USGS Publications Warehouse

Morin, R.H.; Carleton, G.B.; Poirier, S.

1997-01-01

The Passaic Formation consists of gradational sequences of mudstone, siltstone, and sandstone, and is a principal aquifer in central New Jersey. Ground-water flow is primarily controlled by fractures interspersed throughout these sedimentary rocks and characterizing these fractures in terms of type, orientation, spatial distribution, frequency, and transmissivity is fundamental towards understanding local fluid-transport processes. To obtain this information, a comprehensive suite of geophysical logs was collected in 10 wells roughly 46 m in depth and located within a .05 km2 area in Hopewell Township, New Jersey. A seemingly complex, heterogeneous network of fractures identified with an acoustic televiewer was statistically reduced to two principal subsets corresponding to two distinct fracture types: (1) bedding-plane partings and (2) high-angle fractures. Bedding-plane partings are the most numerous and have an average strike of N84??W and dip of 20??N. The high-angle fractures are oriented subparallel to these features, with an average strike of N79??E and dip of 71??S, making the two fracture types roughly orthogonal. Their intersections form linear features that also retain this approximately east-west strike. Inspection of fluid temperature and conductance logs in conjunction with flowmeter measurements obtained during pumping allows the transmissive fractures to be distinguished from the general fracture population. These results show that, within the resolution capabilities of the logging tools, approximately 51 (or 18 percent) of the 280 total fractures are water producing. The bedding-plane partings exhibit transmissivities that average roughly 5 m2/day and that generally diminish in magnitude and frequency with depth. The high-angle fractures have average transmissivities that are about half those of the bedding-plane partings and show no apparent dependence upon depth. The geophysical logging results allow us to infer a distinct hydrogeologic structure within this aquifer that is defined by fracture type and orientation. Fluid flow near the surface is controlled primarily by the highly transmissive, subhorizontal bedding-plane partings. As depth increases, the high-angle fractures apparently become more dominant hydrologically.The Passaic Formation consists of gradational sequences of mudstone, siltstone, and sandstone, and is a principal aquifer in central New Jersey. Ground-water flow is primarily controlled by fractures interspersed throughout these sedimentary rocks and characterizing these fractures in terms of type, orientation, spatial distribution, frequency, and transmissivity is fundamental towards understanding local fluid-transport processes. To obtain this information, a comprehensive suite of geophysical logs was collected in 10 wells roughly 46 m in depth and located within a .05 km2 area in Hopewell Township, New Jersey. A seemingly complex, heterogeneous network of fractures identified with an acoustic televiewer was statistically reduced to two principal subsets corresponding to two distinct fracture types: (1) bedding-plane partings and (2) high-angle fractures. Bedding-plane partings are the most numerous and have an average strike of N84?? W and dip of 20?? N. The high-angle fractures are oriented subparallel to these features, with an average strike of N79?? E and dip of 71?? S, making the two fracture types roughly orthogonal. Their intersections form linear features that also retain this approximately east-west strike. Inspection of fluid temperature and conductance logs in conjunction with flowmeter measurements obtained during pumping allows the transmissive fractures to be distinguished from the general fracture population. These results show that, within the resolution capabilities of the logging tools, approximately 51 (or 18 percent) of the 280 total fractures are water producing. The bedding-plane partings exhibit transmissivities that average roughly 5 m2/day and that generally dimi

Fluid Interactions with Explosion-Induced Fractures

NASA Astrophysics Data System (ADS)

Swanson, E.; Sussman, A. J.; Wilson, J.; Broome, S.

2016-12-01

Fluids can chemically interact with the fractures they flow through, a process that may affect the movement of fluids in the subsurface. This is a topic of interest to a large variety of research areas, including (but not limited to) production of oil and gas, contaminant tracking, geothermal energy production, CO2 sequestration, and nuclear test monitoring. A study performed as part of the Source Physics Experiment, designed to look at the effects of underground chemical explosions, provides a rare opportunity to compare cores from pre-shot and post-shot rock, from damage created in situ. We present data on the variability of microfracture density with distance from the explosion, as well as the occurrence of fractures that either open or contain clay infill. We find that both open and filled fractures occur more frequently within the post-shot samples (by a factor of up to 4x), with similar spatial distributions. This calls into question the validity of the commonly made assumption that all filled fractures were present prior to the explosive shot, and only open fractures can represent explosion-induced damage. These results suggest that fluid-rock interactions might have a significant influence on the permeabilities that result from explosions, even within a few weeks. Additional data on the mechanical properties of the pre-shot and post-shot core samples show an unexpected pattern during unconfined compressive strength tests: the samples retrieved following 2 successive shots failed at higher stresses than did samples retrieved after 1 shot. We present these results, along with some evidence this behavior may arise from trace differences in water content during testing.

Crossover from capillary fingering to viscous fingering in a rough fracture

NASA Astrophysics Data System (ADS)

Hu, R.; Chen, Y.; Wu, D. S.

2017-12-01

Controlled by the competition between capillary and viscous forces, the displacement patterns of one fluid displacing another more viscous one exhibit capillary fingering, viscous fingering, and the crossover between the two. Although extensive studies have investigated viscous and capillary fingerings in porous and fractured media, a few studies focused on the crossover in rough fractures, and how viscous and capillary forces affect the crossover remains unclear. Using a transparent fracture visualization system, we studied how the competition impacts the crossover in a horizontal rough fracture. Drainage experiments of water displacing oil were conducted at seven flow rates (capillary number log10Ca ranging from -7.07 to -3.07) and four viscosity ratios (M = 1/1000, 1/500, 1/100 and 1/50). We consistently observed lower invading fluid saturations in the crossover zone. In addition, we proposed a phase diagram for the displacement patterns in a rough fracture that is consistent with similar studies in porous media. Based on real-time imaging and statistical analysis of the invasion morphology, we showed that the competition between the capillary and viscous forces is responsible for the saturation reduction in the crossover zone. In this zone, finger propagation toward the outlet (characteristic of viscous fingering) as well as void-filling in the transverse and backward directions (characteristic of capillary fingering), are both suppressed. Therefore, the invading fluid tends to occupy larger apertures with higher characteristic front velocity, promoting void-filling toward the outlet with thinner finger growth and resulting in a larger volume of defending fluid left behind.

Evaluation of borehole geophysical logging, aquifer-isolation tests, distribution of contaminants, and water-level measurements at the North Penn Area 5 Superfund Site, Bucks and Montgomery counties, Pennsylvania

USGS Publications Warehouse

Bird, Philip H.; Conger, Randall W.

2002-01-01

Borehole geophysical logging and aquifer-isolation (packer) tests were conducted at the North Penn Area 5 Superfund site in Bucks and Montgomery Counties, Pa. Caliper, naturalgamma, single-point-resistance, fluid-temperature, fluid-resistivity, heatpulse-flowmeter, and digital acoustic-televiewer logs and borehole television surveys were collected in 32 new and previously drilled wells that ranged in depth from 68 to 302 feet. Vertical borehole-fluid movement direction and rate were measured with a high-resolution heatpulse flowmeter under nonpumping conditions. The suite of logs was used to locate water-bearing fractures, determine zones of vertical borehole-fluid movement, select depths to set packers, and locate appropriate screen intervals for reconstructing new wells as monitoring wells. Aquifer-isolation tests were conducted in four wells to sample discrete intervals and to determine specific capacities of discrete water-bearing zones. Specific capacities of isolated zones during packer testing ranged from 0.12 to 15.30 gallons per minute per foot. Most fractures identified by borehole geophysical methods as water-producing or water-receiving zones produced water when isolated and pumped. The acoustic-televiewer logs define two basic fracture sets, bedding-plane partings with a mean strike of N. 62° E. and a mean dip of 27° NW., and high-angle fractures with a mean strike of N. 58° E. and a mean dip of 72° SE. Correlation of heatpulse-flowmeter data and acoustic-televiewer logs showed 83 percent of identified water-bearing fractures were high-angle fractures.

Quality assessment of reservoirs by means of outcrop data and "discrete fracture network" models: The case history of Rosario de La Frontera (NW Argentina) geothermal system

NASA Astrophysics Data System (ADS)

Maffucci, R.; Bigi, S.; Corrado, S.; Chiodi, A.; Di Paolo, L.; Giordano, G.; Invernizzi, C.

2015-04-01

We report the results of a systematic study carried out on the fracture systems exposed in the Sierra de La Candelaria anticline, in the central Andean retrowedge of northwestern Argentina. The aim was to elaborate a kinematic model of the anticline and to assess the dimensional and spatial properties of the fracture network characterizing the Cretaceous sandstone reservoir of the geothermal system of Rosario de La Frontera. Special regard was devoted to explore how tectonics may affect fluid circulation at depth and control fluids' natural upwelling at surface. With this aim we performed a Discrete Fracture Network model in order to evaluate the potential of the reservoir of the studied geothermal system. The results show that the Sierra de La Candelaria regional anticline developed according to a kinematic model of transpressional inversion compatible with the latest Andean regional WNW-ESE shortening, acting on a pre-orogenic N-S normal fault. A push-up geometry developed during positive inversion controlling the development of two minor anticlines: Termas and Balboa, separated by further NNW-SSE oblique-slip fault in the northern sector of the regional anticline. Brittle deformation recorded at the outcrop scale is robustly consistent with the extensional and transpressional events recognized at regional scale. In terms of fluid circulation, the NNW-SSE and NE-SW fault planes, associated to the late stage of the positive inversion, are considered the main structures controlling the migration paths of hot fluids from the reservoir to the surface. The results of the fracture modeling performed show that fractures related to the same deformation stage, are characterized by the highest values of secondary permeability. Moreover, the DFN models performed in the reservoir volume indicates that fracture network enhances its permeability: its secondary permeability is of about 49 mD and its fractured portion represents the 0.03% of the total volume.