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1

Vertical fracture containment during massive hydraulic fracturing  

SciTech Connect

Massive hydraulic fractures are projected to play a major role in the recovery of the tremendous reserves of gas tied up in the tight gas sands of the Deep Basin of N. Alberta and British Columbia. One of the major problems in designing fractures in such formations is the uncertain vertical extent of these fractures: fracture containment. This work presents a procedure for predicting the vertical extent of fractures in multi-layered formations with varying material properties and tectonic stresses. The numeric procedure uses the finite element technique for the rock deformation calculations and employs special high order, crack-tip elements to improve the accuracy of stress intensity calculations. Furthermore, it makes use of the powerful numeric technique of static condensation to reduce computer memory and computation time. The elastic deformation calculation can be coupled to a fluid flow model to predict dynamic fracture growth.

Cormack, D.E.; Fung, R.L.; Vijayakumar, S.

1983-01-01

2

On the Design of Vertical Hydraulic Fractures  

Microsoft Academic Search

Some of the assumptions involved in designing vertical hydraulic fractures should be critically examined as to their validity. This is done on the basis of a new width equation and a numerical design procedure. It is found that some of the assumptions related to the fluid mechanics of the problem greatly affect the computed results and therefore deserve special attention.

Abbas Daneshy

1973-01-01

3

Hydraulic fracturing-1  

SciTech Connect

This book contains papers on hydraulic fracturing. Topics covered include: An overview of recent advances in hydraulic fracturing technology; Containment of massive hydraulic fracture; and Fracturing with a high-strength proppant.

Not Available

1990-01-01

4

Verification and monitoring of deep granular iron permeable reactive barriers emplaced by vertical hydraulic fracturing and injection for groundwater remediation  

Microsoft Academic Search

This study evaluated the use of vertical hydraulic fracturing and injection (VHFI) to emplace granular iron as a deep passive treatment system to remove organic contaminants from groundwater at the Massachusetts Military Reservation on Cape Cod, Massachusetts. It was the first permeable reactive barrier (PRB) constructed at a depth greater than 15 m below the ground surface. VHFI propagates a

David Wallace Hubble

2003-01-01

5

What Is Hydraulic Fracturing?  

NSDL National Science Digital Library

Hydraulic fracturing is a process used in nine out of 10 natural gas wells in the United States, where millions of gallons of water, sand and chemicals are pumped underground to break apart the rock and release the gas. Scientists are worried that the chemicals used in fracturing may pose a threat either underground or when waste fluids are handled and sometimes spilled on the surface. This poster presentation illustrates the under surface process of hydraulic fracking and the distribution flow to the market.

2012-01-01

6

Computer simulation of hydraulic fractures  

Microsoft Academic Search

We provide a brief historical background of the development of hydraulic fracturing models for use in the petroleum and other industries. We discuss scaling laws and the propagation regimes that control the growth of hydraulic fractures from the laboratory to the field scale. We introduce the mathematical equations and boundary conditions that govern the hydraulic fracturing process, and discuss numerical

J. Adachi; E. Siebrits; A. Peirce; J. Desroches

2007-01-01

7

Hydraulic Fracture Propagation in Layered Rock: Experimental Studies of Fracture Containment  

Microsoft Academic Search

Fracture geometry is an important concern in the design of a massive hydraulic fracture for improved natural gas recovery from low-permeability reservoirs. Determination of the extent of vertical fracture growth and containment in layered rock, a priori, requires an improved understanding of the parameters that may control fracture growth across layer interfaces. We have conducted laboratory hydraulic fracture experiments and

Lawrence Teufel; James Clark

1984-01-01

8

Effect of Natural Fractures on Hydraulic Fracturing  

NASA Astrophysics Data System (ADS)

Hydraulic Fracturing has been used successfully in the oil and gas industry to enhance oil and gas production in the past few decades. Recent years have seen the great development of tight gas, coal bed methane and shale gas. Natural fractures are believed to play an important role in the hydraulic fracturing of such formations. Whether natural fractures can benefit the fracture propagation and enhance final production needs to be studied. Various methods have been used to study the effect of natural fractures on hydraulic fracturing. Discontinuous Deformation Analysis (DDA) is a numerical method which belongs to the family of discrete element methods. In this paper, DDA is coupled with a fluid pipe network model to simulate the pressure response in the formation during hydraulic fracturing. The focus is to study the effect of natural fractures on hydraulic fracturing. In particular, the effect of rock joint properties, joint orientations and rock properties on fracture initiation and propagation will be analyzed. The result shows that DDA is a promising tool to study such complex behavior of rocks. Finally, the advantages of disadvantages of our current model and future research directions will be discussed.

Ben, Y.; Wang, Y.; Shi, G.

2012-12-01

9

Hydraulic-fracture-treatment design simulation  

SciTech Connect

Hydraulic fracturing is a technique for simulating wells completed in low-permeability reservoirs. The process involves the pressurization of an isolated perforated section of the wellbore with a viscous fluid until the induced stresses exceed the formation strength, which causes a failure and thus creates the fracture. Proppants are then pumped into the newly created fracture with viscous fracturing fluid as a carrier. Once initiated, the fracture propagates as additional fracturing fluid is injected. Following the release of the fracturing pressure, the proppants hold the fracture open and provide a conductive channel through which the reservoir fluids flow to the wellbore. Only vertical fractures are considered here. Hydraulic-fracturing simulators are used to design the treatment volume, proppant size and type, and pumping schedules to obtain the desired fracture geometry and conductivities. The pumping schedules are designed by running these simulators on a trial-and-error basis until a desired propped geometry is obtained that will ensure maximum proppant coverage at the end of pumping. With these propped fracture geometry and conductivity data, an economic estimate is usually made for the treatment for a given fracture length and an optimal design is selected for the maximum return of the well.

Acharya, R.

1988-02-01

10

Study of Nordgren's Equation of Hydraulic Fracturing  

Microsoft Academic Search

A nonlinear partial differential equation modeling the propagation of a vertical hydraulic fracture first derived by Nordgren is studied. When properly posed, Nordgren's derivation constitutes a Stefan problem and requires another boundary condition-namely, that the velocity of the fluid at the crack tip equals the velocity of crack propagation. With this addition, Nordgren's similarity solution in the no-leakoff case is

L. Kemp

1990-01-01

11

Method for directional hydraulic fracturing  

DOEpatents

A method for directional hydraulic fracturing using borehole seals to confine pressurized fluid in planar permeable regions, comprising: placing a sealant in the hole of a structure selected from geologic or cemented formations to fill the space between a permeable planar component and the geologic or cemented formation in the vicinity of the permeable planar component; making a hydraulic connection between the permeable planar component and a pump; permitting the sealant to cure and thereby provide both mechanical and hydraulic confinement to the permeable planar component; and pumping a fluid from the pump into the permeable planar component to internally pressurize the permeable planar component to initiate a fracture in the formation, the fracture being disposed in the same orientation as the permeable planar component.

Swanson, David E. (West St. Paul, MN); Daly, Daniel W. (Crystal, MN)

1994-01-01

12

Characterization of the hydraulic properties of fractures in chalk.  

PubMed

The fracture systems intersecting Eocene chalk formations in the Negev desert, Israel, and their hydraulic properties were characterized using a variety of geologic and hydrologic techniques. These included identification of the prevailing directions of fracture systems in outcrops, in cores retrieved from inclined coreholes, in coreholes using video logs, and in trenches. The orientation and inclination of these fracture systems were determined, and evidence of ground water flow on the fracture surfaces was described and ranked. Their hydraulic conductivity was determined through slug and pumping tests performed at discrete intervals. Temperature, electrical conductivity, caliper, gamma and heat-pulse logs were conducted in the same coreholes. The results from the logs, tests, and core descriptions were compared to identify reliable and cost-effective tools for investigating the hydraulic characteristics of fracture systems. We concluded that in the study area: (1) fracture mapping in outcrops and coreholes (including downhole video and caliper logs) must be supplemented by hydraulic testing of the mapped fracture sets in the coreholes; (2) inclined coreholes provide information regarding the orientation of the hydraulically active fracture systems that cannot be obtained from vertical boreholes; (3) hydraulic testing of unpacked holes provides a reasonable estimate of the maximum hydraulic conductivity; and (4) the hydraulic conductivity distribution with depth is log normal and all significant ground water flow takes place within the upper 25 m. PMID:12873016

Nativ, Ronit; Adar, Eilon; Assaf, Lior; Nygaard, Erik

2003-01-01

13

Monitoring hydraulic fracture growth: Laboratory experiments  

SciTech Connect

The authors carry out small-scale hydraulic fracture experiments to investigate the physics of hydraulic fracturing. The laboratory experiments are combined with time-lapse ultrasonic measurements with active sources using both compressional and shear-wave transducers. For the time-lapse measurements they focus on ultrasonic measurement changes during fracture growth. As a consequence they can detect the hydraulic fracture and characterize its shape and geometry during growth. Hence, this paper deals with fracture characterization using time-lapse acoustic data. Hydraulic fracturing is used in the oil and gas industry to stimulate reservoir production.

Groenenboom, J.; Dam, D.B. van

2000-04-01

14

Hydraulic Fracturing Return Waters and Legacy Landscapes  

Microsoft Academic Search

Hydraulic fracturing of gas-bearing shales to enhance recovery is growing increasingly common globally. However, disposal of return water remains a challenge, particularly in humid environments where evapoconcentration potential is limited. Further, return water typical of recent activity in the Marcellus Shale in the eastern United States is substantially saltier relative to other shales where hydraulic fracturing has been employed. This

D. J. Bain; A. R. Michanowicz; K. J. Ferrar

2010-01-01

15

The crack tip region in hydraulic fracturing  

Microsoft Academic Search

We present analytical tip region solutions for fracture width and pressure when a power law fluid drives a plane strain fracture in an impermeable linear elastic solid. Our main result is an intermediate asymptotic solution in which the tip region stress is dominated by a singularity which is particular to the hydraulic fracturing problem. Moreover this singularity is weaker than

J. Desroches; E. Detournay; B. Lenoach; P. Papanastasiou; J. R. A. Pearson; M. Thiercelin; A. Cheng

1994-01-01

16

DEMONSTRATION BULLETIN: HYDRAULIC FRACTURING OF CONTAMINATED SOIL  

EPA Science Inventory

Hydraulic fracturing is a physical process that creates fractures in silty clay soil to enhance its permeability. The technology, developed by the Risk Reduction Engineering Laboratory (RREL) and the University of Cincinnati, creates sand-filled horizontal fractures up to 1 in. i...

17

Hydraulic Fracturing and the Environment  

NASA Astrophysics Data System (ADS)

In this presentation, we highlight two key environmental concerns of hydraulic fracturing (HF), namely induced seismicity and groundwater contamination (GC). We examine the induced seismicity (IS) associated with different subsurface fluid injection and production (SFIP) operations and the key operational parameters of SFIP impacting it. In addition we review the key potential sources for possible water contamination. Both in the case of IS and GC we propose modeling and data analysis methods to quantify the risk factors to be used for monitoring and risk reduction. SFIP include presents a risk in hydraulic fracturing, waste water injection, enhanced oil recovery as well as geothermal energy operations. Although a recent report (NRC 2012) documents that HF is not responsible for most of the induced seismicities, we primarily focus on HF here. We look into vaious operational parameters such as volume and rate of water injection, the direction of the well versus the natural fracture network, the depth of the target and the local stress field and fault system, as well as other geological features. The latter would determine the potential for triggering tectonic related events by small induced seismicity events. We provide the building blocks for IS risk assessment and monitoring. The system we propose will involve adequate layers of complexity based on mapped seismic attributes as well as results from ANN and probabilistic predictive modeling workflows. This leads to a set of guidelines which further defines 'safe operating conditions' and 'safe operating zones' which will be a valuable reference for future SFIP operations. We also illustrate how HF can lead to groundwater aquifer contamination. The source of aquifer contamination can be the hydrocarbon gas or the chemicals used in the injected liquid in the formation. We explore possible pathways of contamination within and discuss the likelihood of contamination from each source. Many of the chemical compounds used in HF fluids are carcinogenic and may pose risk to humans. In addition, recovered HF fluids can be contaminated. We illustrate how different pathways can lead to the risk of aquifer contamination and consequently, risk to human health.

Ayatollahy Tafti, T.; Aminzadeh, F.; Jafarpour, B.; de Barros, F.

2013-12-01

18

Sensitivity of time-lapse seismic data to fracture compliance in hydraulic fracturing  

NASA Astrophysics Data System (ADS)

We study the sensitivity of seismic waves to changes in the fracture normal and tangential compliances by analysing and numerically solving the fracture sensitivity wave equation, which is derived by differentiating the elastic wave equation with respect to the fracture compliance. The sources for the sensitivity wavefield are the sensitivity moments, which are functions of fracture compliance, background elastic properties and the stress acting on the fracture surface. Based on the analysis of the fracture sensitivity wave equation, we give the condition for the weak scattering approximation to be valid for fracture scattering. We study the sensitivity of P and S waves to fracture normal and tangential compliances, respectively, by separating the seismic wavefield and the sensitivity field into P and S components. In the numerical simulations of a single fracture in a homogeneous medium, we study the effect of fracture compliances, source incident angle and background elastic properties on the sensitivity field. We also discuss the sensitivity of seismic data to the compliances of vertical and horizontal fractures, respectively, for surface and borehole acquisitions. Under the weak scattering approximation, we find that the percentage change of fracture compliance in hydraulic fracturing is equal to the percentage change of the recorded time-lapse seismic data. This could provide a means for designing and interpreting experiments that can potentially be used to monitor the opening/closing of a fracture in hydraulic fracturing through time-lapse seismic surveys.

Fang, Xinding; Shang, Xuefeng; Fehler, Michael

2013-12-01

19

Numerical model of massive hydraulic fracture. Final report. [SYMFRAC1  

SciTech Connect

This project has involved development of a hydraulic fracture simulator which calculates fracture height as a function of distance from the wellbore in a situation in which a payzone is bounded by two zones in which the minimum in-situ stress is higher (the fracture is vertical). The fracture must be highly elongated (length/height ratio approximately greater than 4) and variations in elastic modulus across zones are ignored. First, we describe the leakoff and spurt loss calculations employed in the modeling. Second, we discuss a revised version of the vertically symmetric simulator (bounding zone stresses equal). The addition of non-Newtonian flow and leakoff (including spurt loss) is described in detail. An illustrative result is given. Third, we describe in detail the vertically asymmetric simulator (bounding zone stresses not equal). To illustrate the last results, we present design calculations for a 30,000 gallon fracture, which was the first stimulation in the Multi-Well Experiment. The 80 ft fracture interval in the Paludal zone has at its upper edge a 520 psi stress contrast, and at its lower edge a 1195 psi contrast. Computed fracture height growth above and below the perforated interval, bottomhole pressure, and width profiles in vertical sections are displayed. Comparison is made with diagnostic measurements of fracture length, height, and bottomhole pressure. The appropriate computer codes are included in this report. 21 references, 11 figures, 4 tables.

Palmer, I.D.; Craig, H.R.; Luiskutty, C.T.

1985-03-01

20

New proppant for deep hydraulic fracturing  

SciTech Connect

Much work has focused on developing and evaluating various materials for use as proppants for hydraulic fracturing. Sand is used most often as a fracturing proppant in shallow wells. Deep wells with high closure stresses require a proppant, such as sintered bauxite, that will not crush under adverse conditions. Ceramic and zirconium oxide beads and resin-coated sand proppants also have been developed for deep hydraulic fracturing. A new fracturing proppant has been developed that exhibits the properties necessary for use in deep hydraulic fracturing. This proppant is produced by precuring a specially modified phenolformaldehyde resin onto sand. The new proppant maintains conductivity and resists crushing much better than does sand. The new proppant was compared to intermediate-density sintered bauxitic proppants and cured-in-place proppants and the tests were confirmed by an independent laboratory.

Das, K.; Underdown, D.R.

1985-01-01

21

Hydraulic Fracturing Mineback Experiment in Complex Media  

NASA Astrophysics Data System (ADS)

Hydraulic fracturing (or "fracking") for the recovery of gas and liquids from tight shale formations has gained much attention. This operation which involves horizontal well drilling and massive hydraulic fracturing has been developed over the last decade to produce fluids from extremely low permeability mudstone and siltstone rocks with high organic content. Nearly thirteen thousand wells and about one hundred and fifty thousand stages within the wells were fractured in the US in 2011. This operation has proven to be successful, causing hundreds of billions of dollars to be invested and has produced an abundance of natural gas and is making billions of barrels of hydrocarbon liquids available for the US. But, even with this commercial success, relatively little is clearly known about the complexity--or lack of complexity--of the hydraulic fracture, the extent that the newly created surface area contacts the high Reservoir Quality rock, nor the connectivity and conductivity of the hydraulic fractures created. To better understand this phenomena in order to improve efficiency, a large-scale mine-back experiment is progressing. The mine-back experiment is a full-scale hydraulic fracture carried out in a well-characterized environment, with comprehensive instrumentation deployed to measure fracture growth. A tight shale mudstone rock geologic setting is selected, near the edge of a formation where one to two thousand feet difference in elevation occurs. From the top of the formation, drilling, well logging, and hydraulic fracture pumping will occur. From the bottom of the formation a horizontal tunnel will be mined using conventional mining techniques into the rock formation towards the drilled well. Certain instrumentation will be located within this tunnel for observations during the hydraulic fracturing. After the hydraulic fracturing, the tunnel will be extended toward the well, with careful mapping of the created hydraulic fracture. Fracturing fluid will be traceable, as will injected proppant, in order to demarcate in-situ fracture paths and fluid and proppant progression. This underground experiment is referred to as a "mine-back experiment". Several mine-back experiments have been conducted in the past, and have demonstrated complex, diffuse fracture systems in coals and bundled fracture systems in some sandstones. No mine-back experiment has been conducted in the tight shales; but, economics and environmental considerations dictate that more definitive measurements will be extremely helpful to establish fracture growth patterns and to validate monitoring methods such as micro-seismic measurements. This presentation discusses the mine-back experiment and presents details of geologic setting, hydraulic fracturing, and the excavation required before and after the hydraulic fracture. The mine-back experiment will provide ground-truth assessment of hydraulic fracturing, geologic forecasting, micro-seismicity, and other information.

Green, S. J.; McLennan, J. D.

2012-12-01

22

The influence of plasticity in hydraulic fracturing  

Microsoft Academic Search

This paper examines the influence of plasticity in hydraulic fracturing. Fluid flow in the fracture is modelled by lubrication theory. Rock deformation is modelled by the Mohr–Coulomb flow theory of plasticity and the propagation criterion is based on the softening behaviour of rocks. The coupled, nonlinear problem is solved by a combined finite difference–finite element scheme. The results show that

Panos Papanastasiou

1997-01-01

23

Laboratory Hydraulic Fracture Characterization Using Acoustic Emission  

NASA Astrophysics Data System (ADS)

For many years Acoustic Emission (AE) testing has aided in the understanding of fracture initiation and propagation in geologic materials. AEs occur when a material emits elastic waves caused by the sudden occurrence of fractures or frictional sliding along discontinuous surfaces and grain boundaries. One important application of AE is the monitoring of hydraulic fracturing of underground formations to create functional reservoirs at sites where the permeability of the rock is too limited to allow for cost effective fluid extraction. However, several challenges remain in the use of AE to locate and characterize fractures that are created hydraulically. Chief among these challenges is the often large scatter of the AE data that are generated during the fracturing process and the difficulty of interpreting the AE data so that hydraulic fractures can be reliably characterized. To improve the understanding of the link between AE and hydraulic fracturing, laboratory scale model testing of hydraulic fracturing were performed using a cubical true triaxial device. This device consist of a loading frame capable of loading a 30x30x30 cm3 rock sample with three independent principal stresses up to 13 MPa while simultaneously providing heating up to 180 degrees C. Several laboratory scale hydraulic fracture stimulation treatments were performed on granite and rock analogue fabricated using medium strength concrete. A six sensor acoustic emission (AE) array, using wideband piezoelectric transducers, is employed to monitor the fracturing process. AE monitoring of laboratory hydraulic fracturing experiments showed multiple phenomena including winged fracture growth from a borehole, cross-field well communication, fracture reorientation, borehole casing failure and much more. AE data analysis consisted of event source location determination, fracture surface generation and validation, source mechanism determination, and determining the overall effectiveness of the induced fracture network. Source mechanisms were identified using a simplified moment tensor analysis which utilizes the first AE arrival characteristics to determine crack type classifications from a unified decomposition of eigenvalues. The AE event source mechanism locations were plotted to determine if spatial relationships exist and to delineate tensile, shear and mixed mode fractures throughout the testing. Based on the classification of the AE data and the moment tensor analysis, an algorithm was developed to predict the location, extent and geometry of the induced fracture. Differing factors were investigated on how they affect the distribution of tensile and shear fractures including viscosity of fracturing fluid, brittleness of source material, homogeneity of source material, presence of natural fractures and stress conditions. Post-test sample coring and slicing were performed to validate the AE event source locations and the fracture characterization algorithm. Fracture and reservoir condition data from the cores and slices were plotted with the AE event source mechanism locations to validate hypotheses regarding spatial relationships of source mechanisms and test conditions. It was shown that the proposed algorithm can reliably delineate hydraulic fracture characteristics in terms of location, extent and geometry.

Gutierrez, M.

2013-05-01

24

Distribution, Origin, and Hydraulic Influence of Fractures in a Clay-rich Glacial Deposit  

Microsoft Academic Search

In the unconsolidated clay-rich glacial deposits underlying a site in southwestern Ontario, fractures and root casts greatly influence hydraulic conductivity and groundwater flow. The fractures are predominantly vertical and have visible oxidation staining from surface to a depth of 6 m. Root casts commonly occur along fracture surfaces in the upper 3?m, but can also occur as holes in apparently

Larry McKay; J. Fredericia

1995-01-01

25

Economic Recovery of Oil Trapped at Fan Margins Using High Angle Wells and Multiple Hydraulic Fractures  

SciTech Connect

This project attempts to demonstrate the effectiveness of exploiting thin-layered, low-energy deposits at the distal margin of a propagating turbidite complex through the use of hydraulically-fractured horizontal or high-angle wells. The combination of a horizontal or high-angled well and hydraulic fracturing will allow greater pay exposure than can be achieved with conventional vertical wells while maintaining vertical communication between thininterbedded layers and the well bore.

Mike L. Laue

1997-05-08

26

Hydraulic fracturing slurry transport in horizontal pipes  

SciTech Connect

Horizontal-well activity has increased throughout the industry in the past few years. To design a successful hydraulic fracturing treatment for horizontal wells, accurate information on the transport properties of slurry in horizontal pipe is required. Limited information exists that can be used to estimate critical deposition and resuspension velocities when proppants are transported in horizontal wells with non-Newtonian fracturing gels. This paper presents a study of transport properties of various hydraulic fracturing slurries in horizontal pipes. Flow data are gathered in three transparent horizontal pipes with different diameters. Linear and crosslinked fracturing gels were studied, and the effects of variables--e.g., pipe size; polymer-gelling-agent concentration; fluid rheological properties; crosslinking effects; proppant size, density, and concentrations; fluid density; and slurry pump rate--on critical deposition and resuspension velocities were investigated. Also, equations to estimate the critical deposition and resuspension velocities of fracturing gels are provided.

Shah, S.N.; Lord, D.L. (Halliburton Services (US))

1990-09-01

27

New proppant for deep hydraulic fracturing  

SciTech Connect

Much work has been done in the development and evaluation of various materials for use as proppants for hydraulic fracturing. Sand is most often used as a frac proppant in shallow wells. Deep wells having high closure stresses require a proppant such as sintered bauxite which will not crush under such adverse conditions. Proppants such as ceramic and zirconium oxide beads and resin coated sand have been developed for deep hydraulic fracturing; however, use of these materials has been limited. A new frac proppant has been developed which exhibits the properties necessary for use in deep hydraulic fracturing. This frac proppant is produced by precuring a specially modified phenol-formaldehyde resin onto sand. The new frac proppant maintains conductivity and resists crushing, similar to that of sintered bauxite at high closure stress. 11 references.

Underdown, D.R.; Das, K.

1982-01-01

28

The hydraulic fracturing of geothermal formations  

SciTech Connect

Hydraulic fracturing has been attempted in geothermal formations as a means to stimulate both production and injection wells. Since most geothermal formations contain fissures and on occasion massive natural fissures, the production behavior of the man-made fractures results in certain characteristic trends. A model is offered that allows the presence of a finite or infinite conductivity fracture intercepting a fissured medium. The method is based on a numerical discretization of the formation allowing transient interporosity flow. Type curves for pressure drawdown and cumulative production are given for infinite acting and closed reservoirs. Since most of the fissured formations exhibit a degree of anisotropy, the effects of the orientation of the hydraulic fracture with respect to the fissure planes, and of the ratio between the directional permeabilities are then discussed. Guidelines are offered as to the size of appropriate stimulation treatments based on the observed fissured behavior of the reservoir.

Naceur, K. Ben; Economides, M.J.; Schlumberger, Dowell

1988-01-01

29

Characterizing the dynamic behavior of hydraulically-induced fracture networks associated with hydraulic fracture stimulations (Invited)  

NASA Astrophysics Data System (ADS)

Seismic Moment Tensor Inversion (SMTI) analysis of microseismicity recorded with multi-well multi-array configurations allows for the potential determination of fracture growth, both spatially and temporally away from a treatment well, as well as the identification of fracture interactions within the reservoir. Based on these analyses, it may be possible to identify the role of pre-existing fracture networks in fracture development as well as, for example, failure type, fracture connectivity, and fracture intensity. Here, we present our observations based on evaluating event sequences associated with multiple injection programs in shale plays throughout North America. In our analysis we identify that, generally, local hydraulically induced variations in the stress-strain field during stimulation result in mixed-mode shear/tensile failures along predominantly pre-existing fractures/joints emplaced during current- and paleo-stress regimes rather than in the creation of new fractures. Away from treatment intervals, failures tend to be dominated by shear and are heavily influenced by the regional stress conditions. Utilizing Hudson plots (k-T), it appears that the fracture process can be further broken down into four types of activity relative to the treatment well and the start of the injection, namely initiation/reactivation of fractures (k ~ 0, double couple dominated), breakout into formation (explosive isotropic), progression of fracture from the treatment well (mostly explosive isotropic), and fracture infill behind the fracture front (decreasing k with treatment time, i.e., explosive to implosive). Breakout events comprised of crack-opening type failures followed by closure events close to the treatment well could be considered to be a canonical fracture, and that the observed behavior can be thought of as the superposition of many of these canonical fractures. Based on our observations, we suggest that by mapping these mechanisms, we can begin to delineate the development of hydraulically-induced fracture networks during hydraulic fracture stimulations and further establish the underlying fracturing process.

Urbancic, T.; Baig, A. M.

2013-12-01

30

An analytical model for hydraulic fracturing in shallow bedrock formations.  

PubMed

A theoretical method is proposed to estimate post-fracturing fracture size and transmissivity, and as a test of the methodology, data collected from two wells were used for verification. This method can be employed before hydrofracturing in order to obtain estimates of the potential hydraulic benefits of hydraulic fracturing. Five different pumping test analysis methods were used to evaluate the well hydraulic data. The most effective methods were the Papadopulos-Cooper model (1967), which includes wellbore storage effects, and the Gringarten-Ramey model (1974), known as the single horizontal fracture model. The hydraulic parameters resulting from fitting these models to the field data revealed that as a result of hydraulic fracturing, the transmissivity increased more than 46 times in one well and increased 285 times in the other well. The model developed by dos Santos (2008), which considers horizontal radial fracture propagation from the hydraulically fractured well, was used to estimate potential fracture geometry after hydrofracturing. For the two studied wells, their fractures could have propagated to distances of almost 175 m or more and developed maximum apertures of about 2.20 mm and hydraulic apertures close to 0.30 mm. Fracturing at this site appears to have expanded and propagated existing fractures and not created new fractures. Hydraulic apertures calculated from pumping test analyses closely matched the results obtained from the hydraulic fracturing model. As a result of this model, post-fracturing geometry and resulting post-fracturing well yield can be estimated before the actual hydrofracturing. PMID:20572875

dos Santos, José Sérgio; Ballestero, Thomas Paul; Pitombeira, Ernesto da Silva

2011-01-01

31

Uncertainty Analysis of Simulated Hydraulic Fracturing  

NASA Astrophysics Data System (ADS)

Artificial hydraulic fracturing is being used widely to stimulate production of oil, natural gas, and geothermal reservoirs with low natural permeability. Optimization of field design and operation is limited by the incomplete characterization of the reservoir, as well as the complexity of hydrological and geomechanical processes that control the fracturing. Thus, there are a variety of uncertainties associated with the pre-existing fracture distribution, rock mechanics, and hydraulic-fracture engineering that require evaluation of their impact on the optimized design. In this study, a multiple-stage scheme was employed to evaluate the uncertainty. We first define the ranges and distributions of 11 input parameters that characterize the natural fracture topology, in situ stress, geomechanical behavior of the rock matrix and joint interfaces, and pumping operation, to cover a wide spectrum of potential conditions expected for a natural reservoir. These parameters were then sampled 1,000 times in an 11-dimensional parameter space constrained by the specified ranges using the Latin-hypercube method. These 1,000 parameter sets were fed into the fracture simulators, and the outputs were used to construct three designed objective functions, i.e. fracture density, opened fracture length and area density. Using PSUADE, three response surfaces (11-dimensional) of the objective functions were developed and global sensitivity was analyzed to identify the most sensitive parameters for the objective functions representing fracture connectivity, which are critical for sweep efficiency of the recovery process. The second-stage high resolution response surfaces were constructed with dimension reduced to the number of the most sensitive parameters. An additional response surface with respect to the objective function of the fractal dimension for fracture distributions was constructed in this stage. Based on these response surfaces, comprehensive uncertainty analyses were conducted among input parameters and objective functions. In addition, reduced-order emulation models resulting from this analysis can be used for optimal control of hydraulic fracturing. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Chen, M.; Sun, Y.; Fu, P.; Carrigan, C. R.; Lu, Z.

2012-12-01

32

Hydraulic fracturing in granite under geothermal conditions  

USGS Publications Warehouse

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.

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

1980-01-01

33

Fracturing Demonstration using a Hydraulic Press  

NSDL National Science Digital Library

To prepare for the demonstration students are assigned homework problems dealing with brittle deformation in which they must plot Mohr diagrams and determine shear plane orientations and Coulomb coefficients. In class we examine an undeformed core of Yazoo clay (Eocene) taken from a test site on campus. The core is then uniaxially compressed using a hydraulic press. The students are then asked to observe and describe the development of shear fractures (including conjugate shear surfaces) and measure their orientations. In addition, they are asked to speculate on the development of extension fractures that develop during unloading. The fracture data are then used to estimate the Coulomb coefficient for the Yazoo clay sample and comparisons are made to values obtained from samples of differing lithologies. We wrap up with a class discussion summarizing observations from the fracture demonstration.

Harris, James B.

34

Hydromechanical interactions in a fractured carbonate reservoir inferred from hydraulic and mechanical measurements  

Microsoft Academic Search

Hydromechanical coupled processes in a shallow fractured carbonate reservoir rock were investigated through field experiments coupled with analytical and numerical analyses. The experiments consist of hydraulic loading\\/unloading of a water reservoir in which fluid flow occurs mainly inside a heterogeneous fracture network made up of vertical faults and bedding planes. Hydromechanical response of the reservoir was measured using six pressure–normal

F. Cappa; Y. Guglielmi; P. Fénart; V. Merrien-Soukatchoff; A. Thoraval

2005-01-01

35

Economic Recovery of Oil Trapped at Fan Margins Using High Angle Wells and Multiple Hydraulic Fractures  

SciTech Connect

The distal fan margin in the northeast portion of the Yowlumne field contains significant reserves but is not economical to develop using vertical wells. Numerous interbedded shales and deteriorating rock properties limit producibility. In addition, extreme depths (13,000 ft) present a challenging environment for hydraulic fracturing and artificial lift. Lastly, a mature waterflood increases risk because of the uncertainty with size and location of flood fronts. This project attempts to demonstrate the effectiveness of exploiting the distal fan margin of this slope-basin clastic reservoir through the use of a high-angle well completed with multiple hydraulic-fracture treatments. The combination of a high-angle (or horizontal) well and hydraulic fracturing will allow greater pay exposure than can be achieved with conventional vertical wells while maintaining vertical communication between thin interbedded layers and the wellbore. The equivalent production rate and reserves of three vertical wells are anticipated at one-half to two-thirds the cost.

Mike L. Laue

1997-05-30

36

Hydraulic Fracturing Return Waters and Legacy Landscapes  

NASA Astrophysics Data System (ADS)

Hydraulic fracturing of gas-bearing shales to enhance recovery is growing increasingly common globally. However, disposal of return water remains a challenge, particularly in humid environments where evapoconcentration potential is limited. Further, return water typical of recent activity in the Marcellus Shale in the eastern United States is substantially saltier relative to other shales where hydraulic fracturing has been employed. This presentation explores scenarios of both traditional return water disposal and accidental releases of return water to fluvial systems using simple exchange modeling, with particular attention to conditions in landscapes typical of Marcellus country. That is, these simulations will incorporate a historic context, acknowledging decades of coal extraction from surface and sub-surface mines and energy production via combustion of said coal. The interactions between “naturally attenuated” historic contamination and rapidly changing water chemistry are critical to accurate risk assessment in this uncertain environment.

Bain, D. J.; Michanowicz, A. R.; Ferrar, K. J.

2010-12-01

37

Self-potential observations during hydraulic fracturing  

Microsoft Academic Search

The self-potential (SP) response during hydraulic fracturing of intact Sierra granite was investigated in the laboratory. Excellent correlation of pressure drop and SP suggests that the SP response is created primarily by electrokinetic coupling. For low pressures, the variation of SP with pressure drop is linear, indicating a constant coupling coefficient (Cc) of ?200 mV\\/MPa. However, for pressure drops >2

Jeffrey R. Moore; Steven D. Glaser

2007-01-01

38

Self-potential observations during hydraulic fracturing  

Microsoft Academic Search

The self-potential (SP) response during hydraulic fracturing of intact Sierra granite was investigated in the laboratory. Excellent correlation of pressure drop and SP suggests that the SP response is created primarily by electrokinetic coupling. For low pressures, the variation of SP with pressure drop is linear, indicating a constant coupling coefficient (Cc) of -200 mV\\/MPa. However for pressure drops >2

Jeffrey R. Moore; Steven D. Glaser

2007-01-01

39

Potential contaminant pathways from hydraulically fractured shale to aquifers.  

PubMed

Hydraulic fracturing of deep shale beds to develop natural gas has caused concern regarding the potential for various forms of water pollution. Two potential pathways-advective transport through bulk media and preferential flow through fractures-could allow the transport of contaminants from the fractured shale to aquifers. There is substantial geologic evidence that natural vertical flow drives contaminants, mostly brine, to near the surface from deep evaporite sources. Interpretative modeling shows that advective transport could require up to tens of thousands of years to move contaminants to the surface, but also that fracking the shale could reduce that transport time to tens or hundreds of years. Conductive faults or fracture zones, as found throughout the Marcellus shale region, could reduce the travel time further. Injection of up to 15,000,000 L of fluid into the shale generates high pressure at the well, which decreases with distance from the well and with time after injection as the fluid advects through the shale. The advection displaces native fluids, mostly brine, and fractures the bulk media widening existing fractures. Simulated pressure returns to pre-injection levels in about 300 d. The overall system requires from 3 to 6 years to reach a new equilibrium reflecting the significant changes caused by fracking the shale, which could allow advective transport to aquifers in less than 10 years. The rapid expansion of hydraulic fracturing requires that monitoring systems be employed to track the movement of contaminants and that gas wells have a reasonable offset from faults. PMID:22509908

Myers, Tom

2012-01-01

40

INVESTIGATION OF EFFICIENCY IMPROVEMENTS DURING CO2 INJECTION IN HYDRAULICALLY AND NATURALLY FRACTURED RESERVOIRS  

SciTech Connect

This report describes the work performed during the fourth year of the project, ''Investigating of Efficiency Improvements during CO{sub 2} Injection in Hydraulically and Naturally Fractured Reservoirs.'' The objective of this project is to perform unique laboratory experiments with artificially fractured cores (AFCs) and X-ray CT scanner to examine the physical mechanisms of bypassing in hydraulically fractured reservoirs (HFR) and naturally fractured reservoirs (NFR) that eventually result in more efficient CO{sub 2} flooding in heterogeneous or fracture-dominated reservoirs. In Chapter 1, we worked with DOE-RMOTC to investigate fracture properties in the Tensleep Formation at Teapot Dome Naval Reserve as part of their CO{sub 2} sequestration project. In Chapter 2, we continue our investigation to determine the primary oil recovery mechanism in a short vertically fractured core. Finally in Chapter 3, we report our numerical modeling efforts to develop compositional simulator with irregular grid blocks.

David S. Schechter

2005-04-27

41

Hydraulic Fracturing and Drinking Water Resources: Update on EPA Hydraulic Fracturing Study  

EPA Science Inventory

Natural gas plays a key role in our nation's energy future and the process known as hydraulic fracturing (HF) is one way of accessing that resource. Over the past few years, several key technical, economic, and energy developments have spurred increased use of HF for gas extracti...

42

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

PubMed

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. PMID:23552653

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

2013-01-01

43

[Hydraulic fracturing - a hazard for drinking water?].  

PubMed

Hydraulic fracturing (fracking) is a technique used to release and promote the extraction of natural gas (including shale gas, tight gas, and coal bed methane) from deep natural gas deposits. Among the German public there is great concern with regard to the potential environmental impacts of fracking including the contamination of ground water, the most important source of drinking water in Germany. In the present article the risks of ground water contamination through fracking are discussed. Due to the present safety requirements and the obligatory geological and hydrogeological scrutiny of the underground, which has to be performed prior to fracking, the risk of ground water contamination by fracking can be regarded as very low. The toxicity of chemical additives of fracking fluids is discussed. It is recommended that in the future environmental impact assessment and approval of fracs should be performed by the mining authorities in close cooperation with the water authorities. Furthermore, it is recommended that hydraulic fracturing in the future should be accompanied by obligatory ground water monitoring. PMID:24285158

Ewers, U; Gordalla, B; Frimmel, F

2013-11-01

44

Seismic monitoring of the growth of a hydraulic fracture zone at Fenton Hill, New Mexico  

SciTech Connect

The hydraulic fracturing technique is an important method for enhancing hydrocarbon recovery, geothermal energy extraction, and solid waste disposal. Determination of the geometry and growth process of a hydraulic fracture zone is important for monitoring and assessing subsurface fractures. A relative-source-location approach, based on a waveform correlation and a grid search method, has been developed to estimate relative hypocenter locations for a cluster of 157 microearthquakes induced by hydraulic fracturing at the Los Alamos Hot Dry Rock (HDR) geothermal site. Among the 157 events, 147 microearthquakes occurred in a tight cluster with a dimension of 40 m, roughly defining a vertical hydraulic fracture zone with an orientation of N40{degree}W. The length, height, and width of the hydraulic fracture zone are estimated to be 40, 35, and 5 m, respectively. Analysis of the spatial-temporal pattern of the induced microearthquakes reveals that the fracture zone grew significantly, averaging 0.2m/ minute in a two-hour period toward the northwest along the fracture zone strike.

Li, Y.; Cheng, C.H.; Toksoez, M.N. [Massachusetts Inst. of Tech., Cambridge, MA (United States)] [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1998-01-01

45

40 CFR 147.52 - administered program--Hydraulic Fracturing of Coal Beds.  

Code of Federal Regulations, 2010 CFR

...State - administered program--Hydraulic Fracturing of Coal Beds.] 40 PROTECTION...State-administered program--Hydraulic Fracturing of Coal Beds. The UIC program for hydraulic fracturing of coal beds in the State...

2009-07-01

46

77 FR 38024 - Oil and Gas; Well Stimulation, Including Hydraulic Fracturing, on Federal and Indian Lands  

Federal Register 2010, 2011, 2012, 2013

...Well Stimulation, Including Hydraulic Fracturing, on Federal and Indian Lands...proposed rule to regulate hydraulic fracturing on public land and Indian...public of chemicals used in hydraulic fracturing on public land and...

2012-06-26

47

75 FR 35023 - Informational Public Meetings for Hydraulic Fracturing Research Study  

Federal Register 2010, 2011, 2012, 2013

...Informational Public Meetings for Hydraulic Fracturing Research Study AGENCY: Environmental...the relationship between hydraulic fracturing and drinking water. The...the meetings. DATES: The Hydraulic Fracturing Study informational...

2010-06-21

48

77 FR 67361 - Request for Information To Inform Hydraulic Fracturing Research Related to Drinking Water Resources  

Federal Register 2010, 2011, 2012, 2013

...for Information To Inform Hydraulic Fracturing Research Related to Drinking...the potential impacts of hydraulic fracturing on drinking water resources...the relationship between hydraulic fracturing and drinking water...

2012-11-09

49

78 FR 20637 - Notification of Public Meeting and a Public Teleconference of the Hydraulic Fracturing Research...  

Federal Register 2010, 2011, 2012, 2013

...Public Teleconference of the Hydraulic Fracturing Research Advisory Panel AGENCY...public teleconference of the Hydraulic Fracturing Research Advisory Panel to...the Potential Impacts of Hydraulic Fracturing on Drinking Water...

2013-04-05

50

78 FR 25267 - Request for Information To Inform Hydraulic Fracturing Research Related to Drinking Water Resources  

Federal Register 2010, 2011, 2012, 2013

...for Information To Inform Hydraulic Fracturing Research Related to Drinking...the potential impacts of hydraulic fracturing on drinking water resources...the relationship between hydraulic fracturing and drinking water...

2013-04-30

51

78 FR 55253 - Notification of Public Teleconference of the Hydraulic Fracturing Research Advisory Panel  

Federal Register 2010, 2011, 2012, 2013

...Public Teleconference of the Hydraulic Fracturing Research Advisory Panel AGENCY...public teleconference of the Hydraulic Fracturing Research Advisory Panel to...emerging information related to hydraulic fracturing and drinking water...

2013-09-10

52

Observations of long period earthquakes accompanying hydraulic fracturing  

Microsoft Academic Search

Waveforms of most seismic events accompanying hydraulic fracturing have been reported to contain clear P and S waves and have fault plane solutions consistent with shear displacement across a fault. This observation is surprising since classical hydraulic fracturing theory predicts the creation of a tensile opening of a cavity in response to fluid pressure. Very small long period events, similar

Dorthe Bame; Michael Fehler

1986-01-01

53

FEASIBILITY OF HYDRAULIC FRACTURING OF SOILS TO IMPROVE REMEDIAL ACTIONS  

EPA Science Inventory

Hydraulic fracturing, a technique commonly used to increase the yields of oil wells, could improve the effectiveness of several methods of in situ remediation. This project consisted of laboratory and field tests in which hydraulic fractures were created in soil. Laboratory te...

54

Toughness-Dominated Regime of Hydraulic Fracturing in Cohesionless Materials  

NASA Astrophysics Data System (ADS)

This work examines the mechanisms of hydraulic fracturing in cohesionless particulate materials with geotechnical, geological, and petroleum applications. For this purpose, experimental techniques have been developed, and used to quantify the initiation and propagation of hydraulic fractures in saturated particulate materials. The fracturing liquid is injected into particulate materials, which are practically cohesionless. The liquid flow is localized in thin self-propagating crack-like conduits. By analogy we call them 'cracks' or 'hydraulic fractures.' When a fracture propagates in a solid, new surfaces are created by breaking material bonds. Consequently, the material is in tension at the fracture tip. Because the particulate material is already 'fractured,' no new surface is created and no fracturing process per se is involved. Therefore, the conventional fracture mechanics principles cannot be directly applied. Based on the laboratory observations, performed on three particulate materials (Georgia Red Clay, silica flour, and fine sand, and their mixtures), this work offers physical concepts to explain the observed phenomena. The goal is to determine the controlling parameters of fracture behavior and to quantify their effects. An important conclusion of our work is that all parts of the cohesionless particulate material (including the tip zone of hydraulic fracture) are likely to be in compression. The compressive stress state is an important characteristic of hydraulic fracturing in particulate materials with low, or no, cohesion (such as were used in our experiments). At present, two kinematic mechanisms of fracture propagation, consistent with the compressive stress regime, can be offered. The first mechanism is based on shear bands propagating ahead of the tip of an open fracture. The second is based on the tensile strain ahead of the fracture tip and reduction of the effective stresses to zero within the leak-off zone. Scaling indicates that in our experiments, there is a high pressure gradient in the leak-off zone in the direction normal to the fracture. Fluid pressure does not decrease considerably along the fracture, however, due to the relatively wide fracture aperture. This suggests that hydraulically induced fractures in unconsolidated materials may be considered to be within the toughness-dominated regime of hydraulic fracturing. Our results indicate that the primary influence on peak or initiation pressure comes from the remote stresses. However, fracture morphology changes significantly with other chosen parameters (stress, flow rate, rheology and permeability). Additionally, an important characteristic feature of fractures in our experiments is the frequent bluntness of the fracture tip, which suggests that plastic deformation at the fracture tip is important. Modeling shows that large openings at the fracture tip correspond to relatively large 'effective' fracture (surface) energy, which can be orders of magnitude greater than for typical (solid) rocks.

Germanovich, L. N.; Hurt, R. S.; Ayoub, J.; Norman, W. D.

2011-12-01

55

ECONOMIC RECOVERY OF OIL TRAPPED AT FAN MARGINS USING HIGH ANGLE WELLS AND MULTIPLE HYDRAULIC FRACTURES  

SciTech Connect

This project attempts to demonstrate the effectiveness of exploiting thin-layered, low-energy deposits at the distal margin of a prograding turbidite complex through the use of hydraulically fractured horizontal or high-angle wells. The combination of a horizontal or high-angle well and hydraulic fracturing will allow greater pay exposure than can be achieved with conventional vertical wells while maintaining vertical communication between thin interbedded layers and the wellbore. A high-angle well will be drilled in the fan-margin portion of a slope-basin clastic reservoir and will be completed with multiple hydraulic-fracture treatments. Geologic modeling, reservoir characterization, and fine-grid reservoir simulation will be used to select the well location and orientation. Design parameters for the hydraulic-fracture treatments will be determined, in part, by fracturing an existing test well. Fracture azimuth will be predicted by passive seismic monitoring of a fracture-stimulation treatment in the test well using logging tools in an offset well.

Mike L. Laue

1998-11-06

56

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

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

57

Sensors for hydraulic-induced fracturing characterization  

NASA Astrophysics Data System (ADS)

Hydraulic induced fracturing (HIF) in oil wells is used to increase oil productivity by making the subterranean terrain more deep and permeable. In some cases HIF connects multiple oil pockets to the main well. Currently there is a need to understand and control with a high degree of precision the geometry, direction, and the physical properties of fractures. By knowing these characteristics (the specifications of fractures), other drill well locations and set-ups of wells can be designed to increase the probability of connection of the oil pockets to main well(s), thus, increasing productivity. The current state of the art of HIF characterization does not meet the requirements of the oil industry. In Mexico, the SENER-CONACyT funding program recently supported a three party collaborative effort between the Mexican Petroleum Institute, Schlumberger Dowell Mexico, and the Autonomous University of Juarez to develop a sensing scheme to measure physical parameters of a HIF like, but not limited to pressure, temperature, density and viscosity. We present in this paper a review of HIF process, its challenges and the progress of sensing development for down hole measurement parameters of wells for the Chicontepec region of Mexico.

Mireles, Jose, Jr.; Estrada, Horacio; Ambrosio, Roberto C.

2011-05-01

58

A magnetic method for determining the geometry of hydraulic fractures  

USGS Publications Warehouse

We propose a method that may be used to determine the spatial orientation of the fracture plane developed during hydraulic fracture. In the method, magnetic particles are injected into the crack with the fracturing fluid so as to generate a sheet of magnetized material. Since the magnetization of a body with extreme dimension ratios, such as a crack, exceeds that of an equidimensional body and since this magnetization is sensitive both to orientation and geometry, this could be used to obtain information about the crack. By measuring the vertical and horizontal components of the magnetic field and field gradients at the earth's surface surrounding the injection well with superconducting magnetometers having 10-4 gamma sensitivity and also by measuring field direction within the well itself, it should be possible to calculate the orientation and perhaps infer the approximate geometry of the fracture surface. Experiments on electric field potential operated in conjunction with this experiment could further constrain estimates of shape and orientation. ?? 1976 Birkha??user Verlag.

Byerlee, J. D.; Johnston, M. J. S.

1976-01-01

59

Convective Instabilities in Vertical Fractures and Faults  

Microsoft Academic Search

Natural convection of water contained in a vertical fracture or fault in which the temperature increases with depth is strongly influenced by the heat transport processes not only within the water itself but also by the heat transferred to and from the surrounding rock mass. The results of a linear stability analysis indicate that the critical Rayleigh number R* is

Hugh D. Murphy; Geosciences Division

1979-01-01

60

Public health and high volume hydraulic fracturing.  

PubMed

High-volume horizontal hydraulic fracturing (HVHF) in unconventional gas reserves has vastly increased the potential for domestic natural gas production. HVHF has been promoted as a way to decrease dependence on foreign energy sources, replace dirtier energy sources like coal, and generate economic development. At the same time, activities related to expanded HVHF pose potential risks including ground- and surface water contamination, climate change, air pollution, and effects on worker health. HVHF has been largely approached as an issue of energy economics and environmental regulation, but it also has significant implications for public health. We argue that public health provides an important perspective on policymaking in this arena. The American Public Health Association (APHA) recently adopted a policy position for involvement of public health professionals in this issue. Building on that foundation, this commentary lays out a set of five perspectives that guide how public health can contribute to this conversation. PMID:23552646

Korfmacher, Katrina Smith; Jones, Walter A; Malone, Samantha L; Vinci, Leon F

2013-01-01

61

Mixed-mode Mechanism of Hydraulic Fracture Segmentation  

NASA Astrophysics Data System (ADS)

Mixed-mode I+III loading is one of the primary causes of fracture front segmentation. Although such segmented fractures have been observed both in nature and laboratory, we are not aware of direct laboratory experiments on the mode III mechanism of segmentation of hydraulically induced fractures. In this work, we developed a laboratory technique and a theoretical model for studying not only the effect of mode III loading on the onset of hydraulic fracture segmentation, but also the effect of segmentation on the subsequent growth of hydraulic fractures. In quasi-brittle materials, even a small mode III component may cause fracture segmentation due to a tensile stress field induced near the fracture front [Rice, 1968]. Previously, this has been confirmed in experiments with non-hydraulic fractures [Knauss, 1970; Cooke and Pollard, 1996]. In one occasion, quasi-hydraulic fractures propagated in fast, uncontrollable manner [Sommer, 1969]. This is why, we focused on controlled hydraulic fractures with a rather small KIII/KI ratio (1-10 %). For mixed mode I+III experiments, we used transparent, cylindrical PMMA samples with circular internal fractures perpendicular to the sample axis. Fracture orientation was controlled by thermoelastic stresses induced in each sample by preheating it before creating a fracture. In order to apply mode III loading to the initial fracture, a constant torque was applied to the specimen while fluid was injected into the fracture at a constant rate to pressurize it and to induce mode I loading. The velocity of fracture propagation was constrained by controlling the rate of fluid injection. In spite of a small magnitude of the mode III component, we observed segmented fracture fronts in all tested samples. The segments had similar dimensions and shape elongated around the perimeter of the initial fracture. When the fractures were further pressurized by injecting additional fluid into the sample, second-order segments developed along the fronts of the first-order segments. The obtained results indicate that, similar to the case of non-hydraulic fractures, a KIII/KI ratio as small as 1 % is sufficient for fracture front segmentation, even in materials as homogeneous and fracture resistant as PMMA. In reality, a small component of mode III is always expected, for example, due to slight deviations of a fracture shape from planar or interaction with boundaries or other fractures. As a result, front segmentation (at an appropriate scale) is likely to accompany the growth of most (if not all) real, sufficiently large fractures (hydraulic or not) in quasi-brittle materials, which is consistent with many observations of hydraulic fractures and magmatic dikes. However, the described above shape of segments in stable, controllable hydraulic fractures, which appeared in our experiments, was dramatically different from narrow lance-like segments, elongated in the direction of growth, of uncontrollable, unstable, non-hydraulic fractures that were propagated in a similar setting [Sommer, 1969; Hull, 1995]. We also developed a simple theoretical model, which is based on the beam asymptotic approximation. It appears that mechanical interaction between the segments and the parent fracture can be taken into account by considering an effective single fracture of equal total size. The model has one fitting parameter and shows good agreement with the experimental observations.

Hurt, R. S.; Germanovich, L.; Wu, R.

2006-12-01

62

Advanced hydraulic fracturing methods to create in situ reactive barriers  

SciTech Connect

This article describes the use of hydraulic fracturing to increase permeability in geologic formations where in-situ remedial action of contaminant plumes will be performed. Several in-situ treatment strategies are discussed including the use of hydraulic fracturing to create in situ redox zones for treatment of organics and inorganics. Hydraulic fracturing methods offer a mechanism for the in-situ treatment of gently dipping layers of reactive compounds. Specialized methods using real-time monitoring and a high-energy jet during fracturing allow the form of the fracture to be influenced, such as creation of assymmetric fractures beneath potential sources (i.e. tanks, pits, buildings) that should not be penetrated by boring. Some examples of field applications of this technique such as creating fractures filled with zero-valent iron to reductively dechlorinate halogenated hydrocarbons, and the use of granular activated carbon to adsorb compounds are discussed.

Murdoch, L. [FRX Inc., Cincinnati, OH (United States)]|[Clemson Univ., SC (United States). Dept. of Geological Sciences; Siegrist, B.; Meiggs, T. [Oak Ridge National Lab., TN (United States)] [and others

1997-12-31

63

Hydraulic-fracturing controlled dynamics of microseismic clouds  

Microsoft Academic Search

Several dynamic processes related to propagation of hydraulic fracture modify the stress state in rocks and, therefore, they are relevant for triggering of microseismicity. For instance, these are the creation of a new fracture volume, fracturing fluid loss and its infiltration into reservoir rocks as well as diffusion of the injection pressure into the pore space of surrounding rocks and

S. A. Shapiro; C. Dinske; E. Rothert

2006-01-01

64

Theoretical and experimental research on hydraulic fracturing  

SciTech Connect

We are conducting a joint theoretical/experimental research program on hydraulic fracturing. Newly developed two-dimensional numerical models (which include complete descriptions of the elastic continuum and porous flow fluids) have been applied to analyze the effecs of pore pressure on the fracturing process. By means of small-scale experiments, we are acquiring a better understanding of the effects of the in-situ stress field, the porosity and permeability of the solid, and the presence of interfaces or layering in the solid. Experimentally, we have been studying the growth of cracks near an interface in several materials, including polymethylmethacrylate (PMMA), Nugget sandstone, and Indiana limestone. Results have shown that the mechanical properties of the interface relative to the properties of the materials on either side are important. A crack will not cross a well-bonded interface between two pieces of PMMA, even in the presence of a 13.79-MPa (2000-psi) normal load. Cracks will cross a well-bonded interface from PMMA to limestone, but not vice versa. Similarly, cracks will propagate across a bonded interface from Nugget sandstone to limestone, but not the other way. Pressure-driven cracks will cross an unbonded interface between limestone blocks at normal loads as low as 3.45 MPa (500 psi).

Hanson, M.E.; Anderson, G.D.; Shaffer, R.J.

1980-06-01

65

Studies investigate effects of hydraulic fracturing  

NASA Astrophysics Data System (ADS)

The use of hydraulic fracturing, also known as fracking, to enhance the retrieval of natural gas from shale has been increasing dramatically—the number of natural gas wells rose about 50% since 2000. Shale gas has been hailed as a relatively low-cost, abundant energy source that is cleaner than coal. However, fracking involves injecting large volumes of water, sand, and chemicals into deep shale gas reservoirs under high pressure to open fractures through which the gas can travel, and the process has generated much controversy. The popular press, advocacy organizations, and the documentary film Gasland by Josh Fox have helped bring this issue to a broad audience. Many have suggested that fracking has resulted in contaminated drinking water supplies, enhanced seismic activity, demands for large quantities of water that compete with other uses, and challenges in managing large volumes of resulting wastewater. As demand for expanded domestic energy production intensifies, there is potential for substantially increased use of fracking together with other recovery techniques for “unconventional gas resources,” like extended horizontal drilling.

Balcerak, Ernie

2012-11-01

66

Electrokinetic coupling in hydraulic fracture propagation  

NASA Astrophysics Data System (ADS)

Electrokinetic coupling is the most popular mechanism proposed to explain observed electromagnetic signals associated with the hydraulic fracturing of rocks. Measurements in both controlled laboratory and in situ conditions show clear evidence of the phenomenon. However there have been no reports on the description of the source mechanism, its relationship to a propagating crack, nor the electromagnetic field distribution due to such a source advancing through an electrically conductive medium. In this work it is shown that a surface electric current density arising on the walls of a fluid driven propagating crack can explain the measurements of electric streaming potential recorded during hydraulic fracturing experiments. The properties of the streaming current source are studied at the microscopic scale in light of the electrokinetic coupling expected at the outermost grains of the crack's surface. Expressions are derived for the average macroscopic transport equations describing the coupled fluid, and electrical current flow, at the interface between a fluid continuum and a homogeneous porous medium, where a Darcy flow regime (porous medium) competes with a rather Poiseuille type (fracture channels). The properties of the electrokinetic boundary sources are analyzed in light of the average electrical current density arising on the interface, as the fluid electrolyte flows in both the porous media and the adjacent fluid continuum. It is found that two coupling coefficients are required to describe the streaming current density. Indeed the flow is driven by both, a tangential pressure gradient, as well as by forward momentum transfer across the permeable boundary. The coupling coefficients are obtained from the spatial average of the tangential stress exerted on the pore surfaces, and they are found to be position dependent, as the tangential stress transitions from that on the porous conduits, to that on the surface of the outer most grains. Furthermore each coefficient gives rise to both a volumetric current density, due to the flow along the pore conduits, as well as a surface current density, due to the flow along the outer most surface. The latter contribution is found to dominate, as the tangential stress scales with the macroscopic characteristic length of the system. From a macroscopic stand point a source space-time function is established for the average current density prescribed by the pressure profile expected at the walls of a crack, which propagates under mobile equilibrium, in the context of linear elasticity theory. Expressions for the electromagnetic fields due to such a source are derived for a crack propagating with a constant velocity, in a homogeneous isotropic conducting medium. It is found that the spatial and temporal behavior of the fields reasonably agree with measurements performed under controlled laboratory experiments. In situ measurements are only studied qualitatively. Nevertheless, despite the obvious fact that a homogeneous whole-space medium does not appropriately describe a realistic earth model, the magnitude of the fields and the temporal behavior of the signals can be well reproduced using typical parameters of a hydraulic fracturing procedure. Electrokinetic coupling has also been proposed in the context of earthquake precursory signals, due to dilatant crack growth at depth. Several ideas have been discussed in the literature in order to justify experimental measurements of electromagnetic field which presumably appear before the onset of an earthquake. The source mechanism described in the present report, occurring at depth ranges of earthquake slip zones, yields electromagnetic signal levels which are 3 orders of magnitude smaller than the noise floor of currently available commercial instrumentation. This suggests that observing this type of phenomenon as an earthquake precursor would then be very challenging.

Cuevas, Nestor Herman

67

Hydraulic Fracturing: Paving the Way for a Sustainable Future?  

PubMed Central

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.

Chen, Jiangang; Al-Wadei, Mohammed H.; Kennedy, Rebekah C. M.; Terry, Paul D.

2014-01-01

68

Hydraulic fracturing: paving the way for a sustainable future?  

PubMed

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

Chen, Jiangang; Al-Wadei, Mohammed H; Kennedy, Rebekah C M; Terry, Paul D

2014-01-01

69

How to choose a hydraulic fracture treatment: MHF versus conventional  

SciTech Connect

Points out that open-hole log evaluation, especially compensated neutron density logs, is the primary tool in determining whether a conventional fracture treatment or MHF treatment is required. Ultimate goal of hydraulic fracture treatment, regardless of size or type, is to increase well performance to an optimum economic advantage for the operator. Coring is the best way to obtain reservoir rock parameters. In designing a conventional hydraulic fracturing treatment, reservoir parameters need to be known, but the data need not be as accurate as with MHF treatments. Fluid viscosity in either MHF or conventional fracturing treatments is a critical factor. Proppant type and placement in the hydraulic fracture are critical to the success of both MHF and conventional fracture treatments. Suggests that information relating to reservoir, fluids, proppants, and mechanics of the treatment should be integrated and computer simulation of the treatment should be performed.

Holcomb, B.

1982-08-01

70

ECONOMIC RECOVERY OF OIL TRAPPED AT FAN MARGINS USING HIGH ANGLE WELLS AND MULTIPLE HYDRAULIC FRACTURES  

SciTech Connect

This project attempts to demonstrate the effectiveness of exploiting thin-layered, low-energy deposits at the distal margin of a prograding turbidite complex through the use of hydraulically fractured horizontal or high-angle wells. The combination of a horizontal or high-angle well and hydraulic fracturing will allow greater pay exposure than can be achieved with conventional vertical wells while maintaining vertical communication between thin interbedded layers and the wellbore. A high-angle well will be drilled in the fan-margin portion of a slope-basin clastic reservoir and will be completed with multiple hydraulic-fracture treatments. Geologic modeling, reservoir characterization, and fine-grid reservoir simulation will be used to select the well location and orientation. Design parameters for the hydraulic-fracture treatments will be determined, in part, by fracturing an existing test well. Fracture azimuth will be predicted by passive seismic monitoring of a fracture-stimulation treatment in the test well using logging tools in an offset well. The long radius, near horizontal well was drilled during the first quarter of 1996. Well conditions resulted in the 7 in. production liner sticking approximately 900 ft off bottom. Therefore, a 5 in. production liner was necessary to case this portion of the target formation. Swept-out sand intervals and a poor cement bond behind the 5 in. liner precluded two of the three originally planned hydraulic fracture treatments. As a result, all pay intervals behind the 5 in. liner were perforated and stimulated with a non-acid reactive fluid. Following a short production period, the remaining pay intervals in the well (behind the 7 in. liner) were perforated. The well was returned to production to observe production trends and pressure behavior and assess the need to stimulate the new perforations.

Mike L. Laue

2001-09-28

71

Stimulating Tight Sands in the Presence of Weak Stress Barriers by Modified Hydraulic Fracturing Techniques: A Status Report  

Microsoft Academic Search

Tight gas formations bounded by base rock and\\/or overlain by an overburden rock, that are not barriers to vertical fracture migration, are not amenable to successful large stimulation treatments by hydraulic fracturing as practiced today. Reservoirs of this nature are abundant. The example considered is the North Douglas Creek Arch field, east of Rangeley, Colorado. This work presents the preliminary

Usman Ahmed; Jon Strawn; Rich Schmidt; Patrick OShea; Richard Veghte

1983-01-01

72

Correlating fracture trends and hydraulic head using semivariogram cloud analysis.  

PubMed

Fracture trends (defined as kilometer-scale linear features interpolated between field observations of fractures along their strikes) often have a dominant orientation. Finding a correlation between this orientation and hydraulic data could shed light on their hydraulic influence. A significant correlation between head residuals from first-order regional drift and the orientation of 2- to 4-km-long fracture trends was found in a study site in the Negev, Israel, using the semivariogram cloud analysis. Correlation of head residuals rather than the head itself implies that the orientation of the fracture trends controls the anisotropy and heterogeneity at this scale, mainly because the fracture trends define the orientation of blocks, which differ in their hydraulic properties. Preferential transmissive pathways are probably shorter than the full extent of the fracture trends, causing a relatively high head difference along the trends on the 2- to 4-km scale. Fracture trend density and additional data from short-range hydraulic tests helped characterize two blocks separated by a fault zone. The identification of hydraulic features on a kilometer scale is necessary for better modeling of regional ground water flow and transport. Hydraulic tests at this scale are not feasible, thereby rendering combined analyses of head and structural data, such as the one presented here, essential. PMID:15819946

Kurtzman, Daniel; Nativ, Ronit; Adar, Eilon M

2005-01-01

73

Non-double-couple mechanisms of microearthquakes induced by hydraulic fracturing  

USGS Publications Warehouse

We have inverted polarity and amplitude information of representative microearthquakes to investigate source mechanisms of seismicity induced by hydraulic fracturing in the Carthage Cotton Valley, east Texas, gas field. With vertical arrays of four and eight three-component geophones in two monitoring wells, respectively, we were able to reliably determine source mechanisms of the strongest events with the best signal-to-noise ratio. Our analysis indicates predominantly non-double-couple source mechanisms with positive volumetric component consistent with opening cracks oriented close to expected hydraulic fracture orientation. Our observations suggest the induced events are directly the result of opening cracks by fluid injection, in contrast to many previous studies where the seismicity is interpreted to be primarily shearing caused by pore pressure diffusion into the surrounding rock or associated with shear stresses created at the hydraulic fracture tip. Copyright 2009 by the American Geophysical Union.

Sileny, J.; Hill, D. P.; Eisner, L.; Cornet, F. H.

2009-01-01

74

Non-double-couple mechanisms of microearthquakes induced by hydraulic fracturing  

NASA Astrophysics Data System (ADS)

We have inverted polarity and amplitude information of representative microearthquakes to investigate source mechanisms of seismicity induced by hydraulic fracturing in the Carthage Cotton Valley, east Texas, gas field. With vertical arrays of four and eight three-component geophones in two monitoring wells, respectively, we were able to reliably determine source mechanisms of the strongest events with the best signal-to-noise ratio. Our analysis indicates predominantly non-double-couple source mechanisms with positive volumetric component consistent with opening cracks oriented close to expected hydraulic fracture orientation. Our observations suggest the induced events are directly the result of opening cracks by fluid injection, in contrast to many previous studies where the seismicity is interpreted to be primarily shearing caused by pore pressure diffusion into the surrounding rock or associated with shear stresses created at the hydraulic fracture tip.

Šílený, Jan; Hill, David P.; Eisner, Leo; Cornet, Francois H.

2009-08-01

75

EPA Study of Hydraulic Fracturing and Drinking Water Resources  

EPA Science Inventory

In its FY2010 Appropriations Committee Conference Report, Congress directed EPA to study the relationship between hydraulic fracturing and drinking water, using: ? Best available science ? Independent sources of information ? Transparent, peer-reviewed process ? Consultatio...

76

An integrated geophysical and hydraulic investigation to characterize a fractured-rock aquifer, Norwalk, Connecticut  

USGS Publications Warehouse

The U.S. Geological Survey conducted an integrated geophysical and hydraulic investigation at the Norden Systems, Inc. site in Norwalk, Connecticut, where chlorinated solvents have contaminated a fractured-rock aquifer. Borehole, borehole-to-borehole, surface-geophysical, and hydraulic methods were used to characterize the site bedrock lithology and structure, fractures, and transmissive zone hydraulic properties. The geophysical and hydraulic methods included conventional logs, borehole imagery, borehole radar, flowmeter under ambient and stressed hydraulic conditions, and azimuthal square-array direct-current resistivity soundings. Integrated interpretation of geophysical logs at borehole and borehole-to-borehole scales indicates that the bedrock foliation strikes northwest and dips northeast, and strikes north-northeast to northeast and dips both southeast and northwest. Although steeply dipping fractures that cross-cut foliation are observed, most fractures are parallel or sub-parallel to foliation. Steeply dipping reflectors observed in the radar reflection data from three boreholes near the main building delineate a north-northeast trending feature interpreted as a fracture zone. Results of radar tomography conducted close to a suspected contaminant source area indicate that a zone of low electromagnetic (EM) velocity and high EM attenuation is present above 50 ft in depth - the region containing the highest density of fractures. Flowmeter logging was used to estimate hydraulic properties in the boreholes. Thirty-three transmissive fracture zones were identified in 11 of the boreholes. The vertical separation between transmissive zones typically is 10 to 20 ft. Open-hole and discrete-zone transmissivity was estimated from heat-pulse flowmeter data acquired under ambient and stressed conditions. The open-hole transmissivity ranges from 2 to 86 ft2/d. The estimated transmissivity of individual transmissive zones ranges from 0.4 to 68 ft2/d. Drawdown monitoring in nearby boreholes under pumping conditions identified hydraulic connections along a northeast-southwest trend between boreholes as far as 560 ft apart. The vertical distribution of fractures can be described by power law functions, which suggest that the fracture network contains transmissive zones consisting of closely spaced fractures surrounded by a less fractured and much less permeable rock mass.

Lane, J. W., Jr.; Williams, J. H.; Johnson, C. D.; Savino, D. M.; Haeni, F. P.

2002-01-01

77

Shear and tension hydraulic fractures in low permeability rocks  

USGS Publications Warehouse

Laboratory hydrofracture experiments were performed on triaxially stressed specimens of oil shale and low-permeability granite. The results show that either shear or tension fractures could develop depending on the level of differentials stress, even in specimens containing preexisting fractures. With 1 kb of confining pressure and differential stress greater than 2kb, hydraulic fluid diffusion into the specimens reduced the effective confining pressure until failure occurred by shear fracture. Below 2kb of differential stress, tension fractures occurred. These results suggest that hydraulic fracturing in regions of significant tectonic stress may produce shear rather than tension fractures. In this case in situ stress determinations based on presumed tension fractures would lead to erroneous results. ?? 1977 Birkha??user Verlag.

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

1977-01-01

78

Hydraulic Fracture Along Glacier Beds by Turbulent Flow of Meltwater  

NASA Astrophysics Data System (ADS)

The problem of hydraulic fracture has been studied extensively, with focus ranging from enhanced hydrocarbon flow to boreholes, to water-driven glacial cracking, to magma eruption through Earth's crust. Although some of this work has addressed fast-flowing fracture, the work applied to glaciers has, so far, focused either on static or relatively long timescale conditions. However, glaciological observations suggest that the fluid-induced fracture process may occur quickly, possibly driven by turbulently flowing water during crack growth. Here, we take the approximation of a fully turbulent flow into an elastic ice medium with small fracture toughness to derive an approximate expression for the crack-tip speed. We accomplish this by first showing that a Manning channel model for wall resistance to turbulent flow leads to the same mathematical structure as for resistance to laminar flow of a power-law viscous fluid. We then make use of the asymptotic crack solution for that case by Desroches et al. [Proc. R. Soc. Lond. A, 1994], and finally estimate the pressure scale appropriate for a finite crack. Comparison of this estimated solution with an exact self-similar solution of Adachi and Detournay [Int. J. Numer. Anal. Meth. Geomech., 2002] validates the approximation. To apply this model, we use parameter values thought appropriate for a basal crack driven by the rapid drainage of a surface meltwater lake near the margin of the Greenland Ice Sheet (Das et al. [Science, 2008]). Thus, we take a maximum excess crack inlet pressure of 0.9 MPa, corresponding to neglect of any hydraulic head loss in flow from the glacier surface to crack entry at the bed, a horizontal basal crack length of 1 km, and a wall roughness scale for flow resistance of 10 mm, and hence estimate a crack-tip speed of about 8 m/s. Loss of ten percent of the surface head on descent to the bed would reduce that speed by slightly more than ten percent. Making various plate theory and linear elastic fracture mechanics approximations perhaps relevant to this setting, we additionally model both vertical and horizontal surface displacements and find rough agreement with the meter-scale displacements observed through GPS by Das et al. [Science, 2008].

Tsai, V. C.; Rice, J. R.

2008-12-01

79

Economic recovery of oil trapped at fan margins using high angle wells and multiple hydraulic fractures. Quarterly report, April 1, 1996--June 30, 1996  

SciTech Connect

This project attempts to demonstrate the effectiveness of exploiting thin-layered, low-energy deposits at the distal margin of a prograding turbidite complex through the use of hydraulically-fractured, horizontal or high-angle wells. The combination of a horizontal or high-angle well and hydraulic fracturing will allow greater pay exposure than can be achieved with conventional vertical wells while maintaining vertical communication between thin interbedded layers and the wellbore. A high-angle well will be drilled in the fan margin portion of a slope-basin clastic reservoir and will be completed with multiple hydraulic-fracture treatments. Geologic modeling, reservoir characterization, and fine-grid reservoir simulation will be used to select the well location and orientation. Design parameters for the hydraulic fracture treatments will be determined by fracturing an existing test well. Fracture azimuth will be predicted, in part, by passive seismic monitoring from an offset well during fracture stimulation of the test well.

Niemeyer, B.L.

1996-07-29

80

Locating microearthquakes induced by hydraulic fracturing in crystalline rock  

Microsoft Academic Search

Microearthquakes induced by hydraulic fracturing in crystalline rock at a depth of 3.5 km were located with a precision of better than 30 m to obtain information about the geometry and dimensions of the fracture system produced. The induced microseismicity was monitored by a network of five vorehole seismic stations; a total of about 800 induced events were reliably located

Leigh House

1987-01-01

81

Distinct element modeling of hydraulically fractured Lac du Bonnet granite  

Microsoft Academic Search

The aim of this study is to better understand the mechanics of fracture development and propagation during hydraulic fracturing. This paper presents some development and applications of discrete particle modeling of this problem. A discontinuum modeling approach idealizes the material as separate particles bonded together at their contact points and utilizes the breakage of individual structural units or bonds to

A. Al-Busaidi; J. F. Hazzard; R. P. Young

2005-01-01

82

Effectiveness of Different Hydraulic Fracturing Treatments in Low Permeability Reservoirs  

Microsoft Academic Search

Various hydraulic fracturing techniques have been used in the completion of oil wells in reservoirs that have low permeability. Reservoir information from over 100 wells in the same geographical area, such as production records, bottom-hole pressure buildup tests, and geophysical well logs were used to determine the effectiveness of different fracturing techniques. Two independent methods were used in the analysis,

Leo Schrider; C. D. Locke; R. D. Haynes

1973-01-01

83

Evaluation of a downhole tiltmeter array for monitoring hydraulic fractures  

SciTech Connect

A series of hydraulic-fracture experiments using a downhole tiltmeter array, called an inclinometer array, was conducted at the Department of Energy (DOE)/Gas Research Institute (GRI) Multi-Site facility in Colorado. The inclinometer array was used to measure the deformation of the reservoir rock in response to hydraulic fracture opening and confirm microseismically measured results. In addition, the inclinometer array was found to be a useful tool for accurately measuring closure stress, measuring residual widths of both propped and unpropped fractures, estimating proppant distribution, and evaluating values of in situ moduli.

Warpinski, N.R.; Engler, B.P. [Sandia National Labs., Albuquerque, NM (United States); Branagan, P.T.; Wilmer, R. [Branagan and Associates, Las Vegas, NV (United States); Wolhart, S.L. [Gas Research Inst., Chicago, IL (United States)

1997-03-01

84

A Thermoelastic Hydraulic Fracture Design Tool for Geothermal Reservoir Development  

SciTech Connect

Geothermal energy is recovered by circulating water through heat exchange areas within a hot rock mass. Geothermal reservoir rock masses generally consist of igneous and metamorphic rocks that have low matrix permeability. Therefore, cracks and fractures play a significant role in extraction of geothermal energy by providing the major pathways for fluid flow and heat exchange. Thus, knowledge of conditions leading to formation of fractures and fracture networks is of paramount importance. Furthermore, in the absence of natural fractures or adequate connectivity, artificial fracture are created in the reservoir using hydraulic fracturing. At times, the practice aims to create a number of parallel fractures connecting a pair of wells. Multiple fractures are preferred because of the large size necessary when using only a single fracture. Although the basic idea is rather simple, hydraulic fracturing is a complex process involving interactions of high pressure fluid injections with a stressed hot rock mass, mechanical interaction of induced fractures with existing natural fractures, and the spatial and temporal variations of in-situ stress. As a result it is necessary to develop tools that can be used to study these interactions as an integral part of a comprehensive approach to geothermal reservoir development, particularly enhanced geothermal systems. In response to this need we have set out to develop advanced thermo-mechanical models for design of artificial fractures and rock fracture research in geothermal reservoirs. These models consider the significant hydraulic and thermo-mechanical processes and their interaction with the in-situ stress state. Wellbore failure and fracture initiation is studied using a model that fully couples poro-mechanical and thermo-mechanical effects. The fracture propagation model is based on a complex variable and regular displacement discontinuity formulations. In the complex variable approach the displacement discontinuities are defined from the numerical solution of a complex hypersingular integral equation written for a given fracture configuration and loading. The fracture propagation studies include modeling interaction of induced fractures with existing discontinuities such as faults and joints. In addition to the fracture propagation studies, two- and three-dimensional heat extraction solution algorithms have been developed and used to estimate heat extraction and the variations of the reservoir stress with cooling. The numerical models have been developed in a user-friendly environment to create a tool for improving fracture design and investigating single or multiple fracture propagation in rock.

Ahmad Ghassemi

2003-06-30

85

Prediction of effects of hydraulic fracturing using reservoir and well flow simulation  

SciTech Connect

This paper presents a method to predict and evaluate effects of hydraulic fracturing jobs by using reservoir and well flow numerical simulation. The concept of the method i5 that steam production rate at the operating well head pressure is predicted with different fracture conditions which would be attained by the hydraulic fracturing jobs. Then, the effects of the hydraulic fracturing is evaluated by comparing the predicted steam production rate and that before the hydraulic fracturing. This course of analysis will suggest how large fracture should be created by the fracturing job to attain large enough increase in steam production at the operating condition and the best scheme of the hydraulic fracturing job.

Mineyuki Hanano; Tayuki Kondo

1992-01-01

86

Etude sur la Propagation des Fractures Hydrauliques dans les Roches (Study on the Propagation of Hydraulic Fractures in Rocks).  

National Technical Information Service (NTIS)

The possibility of forming multiple hydraulic links between two deep wells by means of hydraulic fracturing was investigated. Isotropic rocks and those whose fracture behavior is anisotropic were considered. A mathematical model showed that for isotropic ...

F. H. Cornet

1981-01-01

87

On Mechanisms of Hydraulic Fracturing in Cohesionless Materials  

NASA Astrophysics Data System (ADS)

Based on the developed experimental techniques, hydraulic fracturing in particulate materials has been directly observed in the laboratory. We have conducted an experimental series by varying such controlling parameters as the properties of particulate materials and fracturing fluids, boundary conditions, initial stress states, and injection volumes and rates. As a result, we suggested some (hopefully, fundamental) mechanisms of hydraulic fracturing in particulate materials and determined some (hopefully, relevant) scaling relationships (e.g., the interplay between elastic and plastic processes). While the ongoing work is likely to change at least some conclusions, it is important that the results reported in this paper appear to form the framework for modeling and, perhaps, even for (qualitative) interpretation of some field data. The main conclusion of our work is that hydraulic fracturing in particulate materials is not only possible, but even probable if the fluid leakoff is minimized (e.g., high flow rate, high viscosity, or low permeability). The observed fracture geometry and the measured pressure injection curves suggest that hydraulic fracturing occurs in soft sediments in the following sequence: (i) cavity expansion before the injection pressure reaches its peak; (ii) fracture front initiation from the expanding cavity near the pressure peak; and (iii) propagation of the developed fracture after the peak. Another important conclusion of our work is that all parts of the particulate material (including the tip zone of hydraulic fracture) are likely to be in compression. The compressive stress state is an important characteristic of hydraulic fracturing in particulate materials with low, or no, cohesion (such as were used in our experiments). For the fracture initiation at the peak pressure (i.e., following the initial cavity expansion), there exists a threshold value of cohesion that results in compressive stresses everywhere in the particulate material. For less cohesion, the cohesive materials can be considered to be effectively cohesionless. Three main types of fracture fronts were observed in our laboratory experiments: round, beveled and fingered. Accordingly, three physical mechanisms of fracture propagation corresponding to the three observed front types were suggested. These are ``pile driving'' or cavity expansion, shear banding, and induced cohesion, which appear to be consistent with round, beveled, and fingered fracture fronts, respectively. It is important to emphasize the importance of leakoff effect on hydraulic fractures in particulate materials. In our experiments, fractures appear rather different compared to those in the no-leakoff case. The fluid leakoff region manifests itself as a (bubbly) layer around the fracture, which thins towards the fracture tip, which is similar to brittle fractures. Furthermore, even the tip details of these fractures remarkably resemble cracks in brittle materials. Therefore, currently available experimental observations suggest that even small leakoff may change the fracture pattern rather dramatically. For example, while at the stage of fracture initiation, the cavity expansion mechanism may still be important, the mechanism of induced cohesion may prevail at the developed stage of fracture growth.

Hurt, R. S.; Wu, R.; Germanovich, L.; Chang, H.; Dyke, P. V.

2005-12-01

88

Quantifying Representative Hydraulic Conductivity for Three-Dimensional Fractured Formations  

NASA Astrophysics Data System (ADS)

The fractures and pores in rock formations are the fundamental units for flow and contaminant transport simulations. Due to technical and logical limitations it is difficult in reality to account for such small units to model flow and transport in large-scale problems. The concept of continuum representations of fractured rocks is then used as an alternative to solve for flow and transport in complex fractured formations. For these types of approaches the determinations of the representative parameters such as hydraulic conductivity and dispersion coefficient play important roles in controlling the accuracy of simulation results for large-scale problems. The objective of this study is to develop a discrete fracture network (DFN) model and the associated unstructured mesh generation system to characterize the continuum hydraulic conductivity for fractured rocks on different scales. In this study a coupled three-dimensional model of water flow, thermal transport, solute transport, and geochemical kinetic/equilibrium reactions in saturated/unsaturated porous media (HYDROGEOCHEM) is employed to be the flow simulator to analyze the flow behaviors in fracture formations. The fracture network model and the corresponding continuum model are simulated for same scale problems. Based on the concept of mass conservation in flow, the correlations between statistics of fracture structure and the representative continuum parameters are quantified for a variety of fracture distribution scenarios and scales. The results of this study are expected to provide general insight into the procedures and the associated techniques for analyzing flow in complex large-scale fractured rock systems.

Lee, I.; Ni, C.

2013-12-01

89

Hydraulic transience and the role of bedding fractures in a bedrock aquitard, southeastern Wisconsin, USA  

NASA Astrophysics Data System (ADS)

Hydraulic heads in a dolomitic shale bedrock aquitard in Wisconsin, USA, are apparently not in equilibrium with drawdown in the underlying aquifer system caused by pumping for municipal supply over the last century. Measurements of head with depth, downhole geophysical logs, and estimates of hydraulic conductivity indicate very low vertical hydraulic diffusivity, and show that high horizontal permeability within the aquitard due to bedding-plane fracture zones can allow lateral groundwater flow. Unlike the hydrogeological conceptual models used in many investigations, flow in aquitards cannot always be inferred to be primarily one-dimensional and vertical. Failure to account for transient conditions and lateral flow in similar settings of intensive groundwater pumping could lead to error in estimates of aquitard leakage and underlying aquifer properties.

Eaton, Timothy T.; Bradbury, Kenneth R.

2003-09-01

90

Using seismic tomography to characterize fracture systems induced by hydraulic fracturing  

SciTech Connect

Microearthquakes induced by hydraulic fracturing have been studied by many investigators to characterize fracture systems created by the fracturing process and to better understand the locations of energy resources in the earth`s subsurface. The pattern of the locations often contains a great deal of information about the fracture system stimulated during the hydraulic fracturing. Seismic tomography has found applications in many areas for characterizing the subsurface of the earth. It is well known that fractures in rock influence both the P and S velocities of the rock. The influence of the fractures is a function of the geometry of the fractures, the apertures and number of fractures, and the presence of fluids in the fractures. In addition, the temporal evolution of the created fracture system can be inferred from the temporal changes in seismic velocity and the pattern of microearthquake locations. Seismic tomography has been used to infer the spatial location of a fracture system in a reservoir that was created by hydraulic fracturing.

Fehler, M.; Rutledge, J.

1995-01-01

91

Overview of microseismic monitoring of hydraulic fracturing for unconventional oil and gas plays  

NASA Astrophysics Data System (ADS)

The exponential growth of unconventional resources for oil and gas production has been driven by the use of horizontal drilling and hydraulic fracturing. These drilling and completion methods increase the contact area of the low permeability and porosity hydrocarbon bearing formations and allow for economic production in what was previously considered uncommercial rock. These new resource plays have sparked an enormous interest in microseismic monitoring of hydraulic fracture treatments. As a hydraulic fracture is pumped, microseismic events are emitted in a volume of rock surrounding the stimulated fracture. The goal of the monitoring is to identify and locate the microseismic events to a high degree of precision and to map the position of the induced hydraulic fracture in time and space. The microseismic events are very small, typically having a moment-magnitude range of -4 to 0. The microseismic data are collected using a variety of seismic array designs and instrumentation, including borehole, shallow borehole, near-surface and surface arrays, using either of three-component clamped 15 Hz borehole sondes to simple vertical 10 Hz geophones for surface monitoring. The collection and processing of these data is currently under rapid technical development. Each monitoring method has technical challenges which include accurate velocity modeling, correct seismic phase identification and signal to noise issues. The microseismic locations are used to guide hydrocarbon exploration and production companies in crucial reservoir development decisions such as the direction to drill the horizontal well bores and the appropriate inter-well spacing between horizontal wells to optimally drain the resource. The fracture mapping is also used to guide fracture and reservoir engineers in designing and calibrating the fluid volumes and types, injection rates and pressures for the hydraulic fracture treatments. The microseismic data can be located and mapped in near real-time during an injection and used to assist the operators in the avoidance of geohazards (such as a karst feature or fault) or fracture height growth into undesirable formations such as water-bearing zones (that could ruin the well). An important objective for hydraulic fracture mapping is to map the effective fracture geometry: the specific volume of rock that is contributing to hydrocarbon flow in to the well. This, however, still remains an elusive goal that has yet to be completely understood with the current mapping technology.

Shemeta, J. E.

2011-12-01

92

Occupational exposures to respirable crystalline silica during hydraulic fracturing.  

PubMed

This report describes a previously uncharacterized occupational health hazard: work crew exposures to respirable crystalline silica during hydraulic fracturing. Hydraulic fracturing involves high pressure injection of large volumes of water and sand, and smaller quantities of well treatment chemicals, into a gas or oil well to fracture shale or other rock formations, allowing more efficient recovery of hydrocarbons from a petroleum-bearing reservoir. Crystalline silica ("frac sand") is commonly used as a proppant to hold open cracks and fissures created by hydraulic pressure. Each stage of the process requires hundreds of thousands of pounds of quartz-containing sand; millions of pounds may be needed for all zones of a well. Mechanical handling of frac sand creates respirable crystalline silica dust, a potential exposure hazard for workers. Researchers at the National Institute for Occupational Safety and Health collected 111 personal breathing zone samples at 11 sites in five states to evaluate worker exposures to respirable crystalline silica during hydraulic fracturing. At each of the 11 sites, full-shift samples exceeded occupational health criteria (e.g., the Occupational Safety and Health Administration calculated permissible exposure limit, the NIOSH recommended exposure limit, or the ACGIH threshold limit value), in some cases, by 10 or more times the occupational health criteria. Based on these evaluations, an occupational health hazard was determined to exist for workplace exposures to crystalline silica. Seven points of dust generation were identified, including sand handling machinery and dust generated from the work site itself. Recommendations to control exposures include product substitution (when feasible), engineering controls or modifications to sand handling machinery, administrative controls, and use of personal protective equipment. To our knowledge, this represents the first systematic study of work crew exposures to crystalline silica during hydraulic fracturing. Companies that conduct hydraulic fracturing using silica sand should evaluate their operations to determine the potential for worker exposure to respirable crystalline silica and implement controls as necessary to protect workers. PMID:23679563

Esswein, Eric J; Breitenstein, Michael; Snawder, John; Kiefer, Max; Sieber, W Karl

2013-01-01

93

77 FR 36273 - Public Meeting on Draft Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using...  

Federal Register 2010, 2011, 2012, 2013

...Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel Fuels...diesel fuels in oil and gas hydraulic fracturing and to solicit input during...Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel...

2012-06-18

94

77 FR 40354 - Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel Fuels-Draft  

Federal Register 2010, 2011, 2012, 2013

...Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel Fuels...Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel Fuels...Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel...

2012-07-09

95

Characterizing Fracture Connectivity and Hydraulic Conductivity Heterogeneity in Sedimentary Rocks Using Hydraulic Tomography  

NASA Astrophysics Data System (ADS)

At sites of groundwater contamination in fractured rocks, detailed characterization of flow paths and hydraulic properties at small spatial scales is critical for designing and monitoring remediation. Characterization remains a challenge owing to the extreme hydraulic conductivity heterogeneity of fractured rock aquifers combined with the expense of installing boreholes in these systems. Hydraulic tomography - conducting and analyzing multiple short-duration cross-hole aquifer tests in discrete borehole intervals - holds promise for achieving the degree of characterization needed in contaminated fractured rocks and for maximizing the flow system information gained from a set of boreholes. A hydraulic tomography experiment was performed in shallow dipping fractured mudstones at a contaminated site in the Newark Basin near Trenton, NJ, using a network of seven boreholes separated by horizontal distances of 4.5 to 9 m. Pneumatic packers were installed to separate each open borehole into three or four isolated intervals. Thirteen one-hour aquifer tests were conducted by pumping from intervals intersected by permeable fractures, while continuously measuring drawdown in all isolated intervals. The test data are being analyzed using numerical groundwater flow models and inverse methods to estimate the hydraulic conductivity distribution in the rock. In this sedimentary rock system, high-permeability bedding-plane-parting fractures often can be inferred from qualitative analysis of the drawdown data. This information, together with the detailed geologic framework model for the site, can be used to guide the representation of heterogeneity within beds in the flow models. The drawdowns also suggest that connectivity between the bedding plane fractures occurs along permeable cross-bed fractures. Determining the locations of these cross-bed fractures is much more difficult, partly because the geologic framework typically does not provide clues to their whereabouts. Inverse modeling of the hydraulic tomography data is being tested for its ability to estimate the locations of these fractures, which are important to identify because of their strong control on contaminant transport and remediation. Subsurface view of boreholes at which hydraulic tomography experiment was conducted. Red and blue regions depict high-permeability bedding-plane-parting fracture zones.

Tiedeman, C. R.

2013-12-01

96

Experimental determination of hydraulic anisotropy in fractured formations  

SciTech Connect

Discontinuities in a rock mass are defined as the planes of weakness of structural origin and commonly include fractures, faults, and joints. Many numerical solutions have been proposed which are based on stochastic generation of fractures to represent the actual field conditions; however, this approach neglects the role of the actual discontinuities, and results in misleading conclusions. A model was constructed based on fracture trace mapping. Fracture traces are the surficial expressions of the planes of weakness present in the underlying rock mass and can be seen on aerial photographs and Landsat images. Two fractured formations present in the Black Hills region of South Dakota were selected as prototypes. The Madison Formation composed of limestone and dolomite, and the Minnelusa Formation consisting of sandstone and shale with interbeds of limestone and dolomite. Fracture trace patterns served as overlays for the laboratory flow experiments. A two-dimensional flow cell was constructed. To simulate the field conditions, cuts were made of the fracture trace patterns in impervious glazed vinyl sheets. This resulted in smooth walled polygonal shaped pieces which were glued firmly onto the flow cell. The flow was thus restricted within the fracture walls, conforming to the parallel plate analogy. By scaling down the hydrodynamic field conditions, outflow was measured for each run. The plot of the measured data resulted in the best fit ellipse. The major and minor principal axes of this ellipse indicate the maximum and minimum hydraulic conductivities. A close match of the experimental hydraulic conductivity values with that of the field data validated the use of fracture trace analysis for determining the hydraulic anisotropy in fractured formations.

Cheema, T.J.; Islam, M.R. (South Dakota School of Mines and Technology, Rapid City, SD (United States). Dept. of Geology and Geological Engineering)

1994-09-01

97

Interwell Tracer Analyses of a Hydraulically Fractured Granitic Geothermal Reservoir  

Microsoft Academic Search

Radioisotopic tracer techniques using I¹³¹ and Br⁸² with downhole gamma logging have been used successfully at temperatures up to 200°C (392°F) and depths to 3 km (10,000 ft) to characterize quantitatively flow at injection and production points in hydraulically fractured regions in granite, including mapping of fracture intersections with wellbores. RTD techniques using sodium fluorescein and Br⁸² tracers were developed

Jefferson Tester; Robert Bivins; Robert Potter

1982-01-01

98

Hydraulic fracturing of a moderate permeability reservoir, Kuparuk River Unit  

SciTech Connect

Sixty-five percent of the proven reserves in one of the United States' largest oil fields, the Kuparuk River Unit, are contained in the lower of two producing horizons. This zone, commonly referred to as the ''A'' sand, has a permeability of between 30 and 100 md. Unfortunately this interval is easily damaged during drilling and completion operations. Low initial flow efficiencies have been confirmed by numerous pressure transient tests. A program of hydraulic fracturing was initiated in March 1984 to overcome near wellbore damage and provide stimulation to more efficiently tap ''A'' sand reserves. More than 300 fracture stimulations have been completed to date in the arctic setting of the Kuparuk River Unit. These jobs have used a variety of fluids, proppants, and pumping schedules. The current hydraulic fracture design was evolved by continual interpretation of field results and related data from these previous stimulations. Success of the overall program has been impressive. Average post-fracture flow efficiency has been in excess of 100%. Post-fracture rate increase has averaged approximately 300%, accounting for a total rate increase of over 125,000 BOPD (19,900 m/sup 3//d). Based on these results, fracturing will continue to play an important part in future field development. This paper is the first review of the Kuparuk River Unit fracture program. It provides a case history of the development of a standard fracture design. In addition, the findings of this study would be applicable to reservoirs elsewhere with similar characteristics.

Niemeyer, B.L.; Reinart, M.R.

1986-01-01

99

Coordinated Studies in Support of Hydraulic Fracturing of Coalbed Methane. Annual Report, January 1993-April 1994.  

National Technical Information Service (NTIS)

The production of natural gas from coal typically requires stimulation in the form of hydraulic fracturing and, more recently, cavity completions. The results of hydraulic fracturing treatments have ranged from extremely successful to less than satisfacto...

G. S. Penny M. W. Conway

1994-01-01

100

75 FR 36387 - Informational Public Meetings for Hydraulic Fracturing Research Study; Correction  

Federal Register 2010, 2011, 2012, 2013

...FRL-9168-2] Informational Public Meetings for Hydraulic Fracturing Research Study; Correction AGENCY: Environmental...21, 2010, announcing public meetings for the Hydraulic Fracturing Research Study. The document contained an...

2010-06-25

101

The use of broadband microseisms for hydraulic fracture mapping  

SciTech Connect

When a hydrocarbon reservoir is subjected to a hydraulic fracture treatment, the cracking and slipping of the formation results in the emission of seismic energy. The objective of this study was to determine the advantages of using broadband (100 Hz to 1500 M) microseismic emissions to map a hydraulic fracture treatment. A hydraulic fracture experiment was performed in the Piceance Basin of Western Colorado to induce and record broadband microseismic events. The formation was subjected to four processes; break-down/ballout, step-rate test, KCL mini-fracture, and linear-gel mini-fracture. Broadband microseisms were successfully recorded by a novel three-component wall-locked seismic accelerometer package, placed in an observation well 211 ft (64 m) offset from the treatment well. During the two hours of formation treatment, more than 1200 significant microseismic events were observed. The occurrences of the events strongly correlated with the injection bore-bole pressures during the treatments. Using both hodogram analysis and time of arrival information, estimates of the origination point of the seismic events were computed. A map of the event locations yielded a fracture orientation estimate consistent with the known orientation of the field in the formation. This paper describes the technique for acquiring and analyzing broadband microseismic events and illustrate how the new broadband approach can enhance signal detectability and event location resolution.

Sleefe, G.E.; Warpinski, N.R.; Engler, B.P.

1993-08-01

102

Aligned vertical fractures, HTI reservoir symmetry, and Thomsenseismic anisotropy parameters  

SciTech Connect

The Sayers and Kachanov (1991) crack-influence parametersare shown to be directly related to Thomsen (1986) weak-anisotropyseismic parameters for fractured reservoirs when the crack density issmall enough. These results are then applied to seismic wave propagationin reservoirs having HTI symmetry due to aligned vertical fractures. Theapproach suggests a method of inverting for fracture density from wavespeed data.

Berryman, James G.

2007-06-27

103

Hydraulic fracturing to improve nutrient and oxygen delivery for in-situ bioreclamation  

SciTech Connect

A serious problem in the implementation of in situ bioreclamation is the delivery of nutrients and oxygen to soil of low permeability. The problem commonly requires contaminated soil to be excavated for bioreclamation, resulting in increased exposure to toxic materials, liability and cost. The authors demonstrated that is feasible to create hydraulic fractures at shallow depths (several m) in silty clay till. Fractures created during a recent field test were flat-lying and roughly equant in plan with a maximum dimension of 8 m. Coarse sand was pumped into the fractures to hold them open. The sand was an average of 1.1 cm in maximum thickness. As many as four fractures were created from the same borehole, stacked at vertical spacing of 15 or 30 cm. The technique will be used to deliver slow-releasing granules of nutrients and encapsulated oxygen compounds in an effort to enhance in situ bioreclamation of contaminated soil.

Versper, S.J.; Davis-Hoover, W.J.; Murdoch, L.C.; Pahren, H.R.; Sprockel, O.L.

1991-01-01

104

Monitoring the width of hydraulic fractures with acoustic waves  

Microsoft Academic Search

For a direct determination of the width, the resolution of the signal is required to distinguish the reflections that are related with two distinct fluid\\/solid interfaces delimiting the hydraulic fracture from its solid embedding. To make this distinction, the solid\\/fluid interfaces must be separated at least one eighth of a wavelength and represent sufficient impedance contrast. The applicability of the

Jeroen Groenenboom; Jacob T. Fokkema

1998-01-01

105

FEASIBILITY OF HYDRAULIC FRACTURING OF SOILS TO IMPROVE REMEDIAL ACTIONS  

EPA Science Inventory

Hydraulic fracturing, a method of increasing fluid flow within the subsurface, should improve the effectiveness of several remedial techniques, including pump and treat, vapor extraction, bio-remediation, and soil-flushing. he technique is widely used to increase the yields of oi...

106

Potential Relationships Between Hydraulic Fracturing and Drinking Water Resources  

EPA Science Inventory

The conferees urge the Agency to carry out a study on the relationship between hydraulic fracturing and drinking water, using a credible approach that relies on the best available science, as well as independent sources of information. The conferees expect the study to be conduct...

107

Hydraulic Fracturing and Shale Gas Production: Technology, Impacts, and Policy.  

National Technical Information Service (NTIS)

Hydraulic fracturing is a key technique that has enabled the economic production of natural gas from shale deposits, or plays. The development of large-scale shale gas production is changing the U.S. energy market, generating expanded interest in the usag...

A. Burnham C. Clark C. Harto R. Horner

2012-01-01

108

Inverse modeling of the hydraulic properties of fractured media : development of a flow tomography approach  

NASA Astrophysics Data System (ADS)

Inverse modeling of hydraulic and geometrical properties of fractured media is a very challenging objective due to the spatial heterogeneity of the medium and the scarcity of data. Here we present a flow tomography approach that permits to characterize the location, the connectivity and the hydraulic properties of main flow paths in fractured media. The accurate characterization of the location, hydraulic properties and connectivity of major fracture zones is essential to model flow and solute transport in fractured media. Cross-borehole flowmeter tests, which consist of measuring changes in vertical borehole flows when pumping a neighboring borehole, were shown to be an efficient technique to provide information on the properties of the flow zones that connect borehole pairs [Paillet, 1998; Le Borgne et al., 2006]. The interpretation of such experiments may however be quite uncertain when multiple connections exist. In this study, we explore the potential of flow tomography (i.e., sequential cross-borehole flowmeter tests) for characterizing aquifer heterogeneity. We first propose a framework for inverting flow and drawdown data to infer fracture connectivity and transmissivities. Here we use a simplified discrete fracture network approach that highlights main connectivity structures. This conceptual model attempts to reproduce fracture network connectivity without taking fracture geometry (length, orientation, dip) into account. We then explore the potential of the method for simplified synthetic fracture network models and quantify the sensitivity of drawdown and borehole flow velocities to the transmissivity of the connecting flowpaths. Flow tomography is expected to be most effective if cross-borehole pumping induces large changes in vertical borehole velocities. The uncertainty of the transmissivity estimates increases for small borehole flow velocities. The uncertainty about the transmissivity of fractures that connect the main flowpath but not the boreholes is generally higher. We demonstrate that successively changing pumping and observation boreholes improves the quality of available information and reduces the indetermination of the problem. The inverse method is validated for different synthetic flow scenarios. It is shown to provide a good estimation of connectivity patterns and transmissivities of main flowpaths. Although the chosen fracture network geometry has been simplified, flow tomography appears to be a promising approach for characterizing connectivity patterns and transmissivities of fractured media.

Bour, O.; Klepikova, M.; Le Borgne, T.; De Dreuzy, J.

2013-12-01

109

Laboratory hydraulic fracturing experiments in intact and pre-fractured rock  

USGS Publications Warehouse

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.

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

1977-01-01

110

Analytic crack solutions for tilt fields around hydraulic fractures  

SciTech Connect

The recent development of downhole tiltmeter arrays for monitoring hydraulic fractures has provided new information on fracture growth and geometry. These downhole arrays offer the significant advantages of being close to the fracture (large signal) and being unaffected by the free surface. As with surface tiltmeter data, analysis of these measurements requires the inversion of a crack or dislocation model. To supplement the dislocation models of Davis [1983], Okada [1992] and others, this work has extended several elastic crack solutions to provide tilt calculations. The solutions include constant-pressure 2D, penny-shaped, and 3D-elliptic cracks and a 2D-variable-pressure crack. Equations are developed for an arbitrary inclined fracture in an infinite elastic space. Effects of fracture height, fracture length, fracture dip, fracture azimuth, fracture width and monitoring distance on the tilt distribution are given, as well as comparisons with the dislocation model. The results show that the tilt measurements are very sensitive to the fracture dimensions, but also that it is difficult to separate the competing effects of the various parameters.

Warpinski, N.R.

2000-01-05

111

Laboratory hydraulic fracturing experiments in intact and pre-fractured rock  

Microsoft Academic Search

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

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

1977-01-01

112

Settling and slumping in a Newtonian slurry, and implications for proppant placement during hydraulic fracturing of gas wells  

Microsoft Academic Search

Analytical estimates of the amount of gravity-driven vertical motion of proppant which can occur within a hydraulic fracture during placement are derived, and used to investigate the conditions under which large gravity driven flows can occur. Two major types of gravity-driven rearrangement are considered; settling and slumping. Slumping refers to motion driven by large scale density differences within an effectively

P. S. Hammond

1995-01-01

113

Application of a 3D Hydraulic-Fracturing Simulator for Design of Acid-Fracturing Treatments  

Microsoft Academic Search

Field experience during 1989--90 shows that application of a 3D hydraulic-fracturing simulator increases success of acid-fracturing well treatments. Fracture extension can be limited to the oil-bearing pay, maximum lateral extension can be realized within the height constraint, and acid\\/rock contact time can be increased by a factor of between 3 and 30. Oil-production response can be improved over other stimulation

L. N. Morgenthaler

1994-01-01

114

Understanding Hydraulic Fracture Growth in Tight Oil Reservoirs by Integrating Microseismic Mapping and Fracture Modeling  

Microsoft Academic Search

In this case study, fracture treatments in three tight-oi l reservoirs in the giant Ordos basin of northern China were investigated using microseismic mapping and fracture modeling techniques to understand hydraulic fracture growth behavior and post-frac performance. Reservoirs of intere sts consist of stacked fluvial sand\\/shale deposits, and the ta rget pay zones occur at depths between 1,820 and 2,186

Xinghui Liu; Zongqiang Zhou; Xianwen Li; Zhongxing Li; Yonggao Xu; Baochun Chen

2006-01-01

115

A Rapid Method of Predicting Width and Extent of Hydraulically Induced Fractures  

Microsoft Academic Search

During the hydraulic-fracturing treatment of an oil or gas well, the liquid pressure in the borehole is increased until tensile stress in the surrounding rock exceeds tensile strength. Once a tensile fracture is initiated, it is penetrated by liquid from the borehole and fracture propagation under continuous hydraulic action takes place. The fracturing liquid carries a propping agent to insure

J. Geertsma; F. de Klerk

1969-01-01

116

Hydraulic tomography offers improved imaging of heterogeneity in fractured rocks  

NASA Astrophysics Data System (ADS)

Fractured rocks have presented formidable challenges for accurately predicting groundwater flow and contaminant transport. This is mainly due to our difficulty in mapping the fracture-rock matrix system, their hydraulic properties and connectivity at resolutions that are meaningful for groundwater flow and especially transport modeling. Over the last several decades, considerable effort has gone into creating maps of subsurface heterogeneity in hydraulic conductivity (K) and specific storage (Ss) of fractured rocks. Developed methods include kriging, stochastic simulation, stochastic inverse modeling, and hydraulic tomography. In this presentation, I review the evolution of various heterogeneity mapping approaches and contend that hydraulic tomography, a recently developed aquifer characterization technique for unconsolidated deposits, is also a promising approach in yielding robust maps (or tomograms) of K and Ss heterogeneity for fractured rocks. While hydraulic tomography has recently been shown to be a robust technique, the resolution of the K and Ss tomograms mainly depends on the density of pumping and monitoring locations and the quality of data. The resolution will be improved through the development of new devices for higher density monitoring of pressure responses at discrete intervals in boreholes and potentially through the integration of other data from single-hole tests, borehole flowmeter profiling and tracer tests. Other data from temperature and geophysical surveys as well as geological investigations may improve the accuracy of the maps, but more research is needed. Technological advances will undoubtedly lead to more accurate maps. However, more effort should go into evaluating these maps so that one can gain more confidence in their reliability.

Illman, W. A.

2013-12-01

117

Ipsilateral femoral shaft and vertical patella fracture: a case report  

PubMed Central

Introduction A femoral shaft fracture with an ipsilateral patella fracture has been, to our knowledge, given only cursory attention in English-speaking literature. Case presentation A 15 year old male patient had hitten by a car to his motorcycle came to emergency room and he had been operated for his femoral shaft freacture and vertical patellar fracture which was iniatally missed. Conclusion To us it is vital to obtain CT scan of the patient’s knee if there is an ipsilateral femoral fracture with an ipsilateral knee effusion and a punction which reveals hematoma even in the absence of a fracture line seen in AP and lateral projections.

Ozkan, Korhan; Eceviz, Engin; Sahin, Adem; Ugutmen, Ender

2009-01-01

118

Mathematical modeling of hydraulic fracturing in coal seams  

SciTech Connect

Hydraulic fracturing of coal seam is considered as a process of development of discontinuities in rock mass elements due to change in hydrogeomechanical situation on filtration of fluid under pressure. Failure is associated with excess of the effective stresses over the rock tension strength. The problem on filtration and failure of massif is solved by the finite-element method using the procedure of fictitious nodal forces.

Olovyanny, A.G. [All Russian Science Research Institute for Mine Surveying, St. Petersburg (Russian Federation)

2005-02-01

119

Hydraulic fracturing theory for conditions of thermal stress  

Microsoft Academic Search

Thermal stresses associated with a temperature change of only 10°C are on the order of 10 to 100 bars. This illustrates the important influence thermal stresses can impose on the results of rock stress measurements by the hydraulic fracturing method. In order to examine the problem, expressions are derived to describe the stress field produced by non-steady state heat conduction

G. Stephens; B. Voight

1982-01-01

120

Interpretation of resonance frequencies recorded during hydraulic fracturing treatments  

NASA Astrophysics Data System (ADS)

Hydraulic fracturing treatments are often monitored by strings of geophones deployed in boreholes. Instead of picking discrete events only, we here use time-frequency representations of continuous recordings to identify resonances in two case studies. This paper outlines an interpretational procedure to identify their cause using a subdivision into source, path, and receiver-side effects. For the first case study, two main resonances are observed both at depth by the downhole geophones and on the surface by two broadband arrays. The two acquisition networks have different receiver and path effects, yet recorded the same resonances; these resonances are therefore likely generated by source effects. The amplitude pattern at the surface arrays indicates that these resonances are probably due to pumping operations. In the second case study, selective resonances are detected by the downhole geophones. Resonances coming from receiver effects are either lower or higher frequency, and wave propagation modeling shows that path effects are not significant. We identify two possible causes within the source area, namely, eigenvibrations of fractures or non-Darcian flow within the hydraulic fractures. In the first situation, 15-30 m long fluid-filled cracks could generate the observed resonances. An interconnected fracture network would then be required, corresponding to mesoscale deformation of the reservoir. Alternatively, systematic patterns in non-Darcian fluid flow within the hydraulic fracture could also be their leading cause. Resonances can be used to gain a better understanding of reservoir deformations or dynamic fluid flow perturbations during fluid injection into hydrocarbon and geothermal reservoirs, CO2 sequestration, or volcanic eruptions.

Tary, J. B.; Baan, M.; Eaton, D. W.

2014-02-01

121

Uncertainty in the maximum principal stress estimated from hydraulic fracturing measurements due to the presence of the induced fracture  

Microsoft Academic Search

The classical theory for hydraulic fracturing stress measurements assumes an ideal case with a linear elastic, homogenous, and isotropic medium; and a fracture that reopens distinctly when the minimum tangential borehole stress is exceeded. The induced fracture disturbs this ideal picture in several aspects, which are important for the evaluation of the maximum horizontal principal stress using the fracture reopening

Jonny Rutqvist; Chin-Fu Tsang; Ove Stephansson

2000-01-01

122

On the stability of open hydraulic fractures in the earth's crust  

Microsoft Academic Search

It has been suggested that a substantial amount of heat energy could be extracted from dry hot rocks near the earth's surface by circulating a fluid through large hydraulic fractures. However a theoretical analysis of propagation and closure of hydraulic fractures subject to realistic stress gradients indicates an upper limit for the size of a stable fracture. For example, if

Donald T. Secor; David D. Pollard

1975-01-01

123

Static and dynamic calculation of formation fluid displacement induced by hydraulic fracturing  

Microsoft Academic Search

Hydraulically fracturing a geological formation results in the displacement of the fluids that are distributed within the formation in response to fracturing fluid loss and poroelasticity effects. This process will limit the application of hydraulic fracturing in conjunction with groundwater contamination remediation if the resulting fluid displacement translates to deleterious mobilization of the target contaminants. A dynamic solution for determining

Andrew R. Piggott

1996-01-01

124

Using constant head step tests to determine hydraulic apertures in fractured rock  

Microsoft Academic Search

The initial step in the analysis of contaminant transport in fractured rock requires the consideration of groundwater velocity. Practical methods for estimating the average linear groundwater velocity (v¯) in fractured rock require determination of hydraulic apertures which are commonly calculated by applying the cubic law using transmissivity (T) values and the number of hydraulically active fractures in the test interval.

Patryk M. Quinn; Beth L. Parker; John A. Cherry

2011-01-01

125

Using constant head step tests to determine hydraulic apertures in fractured rock  

Microsoft Academic Search

The initial step in the analysis of contaminant transport in fractured rock requires the consideration of groundwater velocity. Practical methods for estimating the average linear groundwater velocity (v¯) in fractured rock require determination of hydraulic apertures which are commonly calculated by applying the cubic law using transmissivity (T) values and the number of hydraulically active fractures in the test interval.

Patryk M. Quinn; Beth L. Parker; John A. Cherry

126

Coordinated studies in support of hydraulic fracturing of coalbed methane. Annual report, January 1993April 1994  

Microsoft Academic Search

The production of natural gas from coal typically requires stimulation in the form of hydraulic fracturing and, more recently, cavity completions. The results of hydraulic fracturing treatments have ranged from extremely successful to less than satisfactory. The purpose of this work is to characterize common and potential fracturing fluids in terms of coal-fluid interactions to identify reasons for less than

G. S. Penny; M. W. Conway

1994-01-01

127

INVESTIGATION OF EFFICIENCY IMPROVEMENTS DURING CO2 INJECTION IN HYDRAULICALLY AND NATURALLY FRACTURED RESERVOIRS  

Microsoft Academic Search

This report describes the work performed during the fourth year of the project, ''Investigating of Efficiency Improvements during COâ Injection in Hydraulically and Naturally Fractured Reservoirs.'' The objective of this project is to perform unique laboratory experiments with artificially fractured cores (AFCs) and X-ray CT scanner to examine the physical mechanisms of bypassing in hydraulically fractured reservoirs (HFR) and naturally

David S. Schechter

2005-01-01

128

[Vertical root fracture--case report and clinical evaluation].  

PubMed

It is observed at the Dental OPD that some of the patients suffer from toothache are due to tooth fracture. Of the various types of tooth fracture, it is noted that vertical root fracture of molars which have never undergone endodontic treatment has rarely been reported. It is suggested that x-ray examination is the best diagnostic tool as it would show a certain section of the abnormally large root canal. This will indicate a fracture in the root. As the fractured root is mostly very poor in prognosis, the tooth in question should be extracted or it can be treated with root amputation or hemisection to eradicate the fractured root. Three cases of vertical root fracture are reported. The intent of this paper is to probe such cases, the means of diagnosis, and their treatments in clinical practices. Dental colleagues are thus advised to take into consideration the possibility of vertical root fracture whenever patients complain about toothache without any apparent cause. PMID:2637061

Wei, P C; Ju, Y R

1989-12-20

129

Hydraulic fracturing: insights from field, lab, and numerical studies  

NASA Astrophysics Data System (ADS)

Hydraulic fracturing has become an increasingly important technique in stimulating reservoirs for gas, oil, and geothermal energy production. In use commercially since the 1950's, the technique has been widely lauded, when combined with other techniques, for enabling the development of shale gas resources in the United States, providing a valuable and extensive source of domestic energy. However, the technique has also drawn a degree of notoriety from high-profile incidents involving contamination of drinking water associated with gas extraction operations in the Marcellus shale region. This work highlights some of the insights on the behavior of subsurface hydraulic fracturing operations that have been derived from field and laboratory observations as well as from numerical simulations. The sensitivity of fracture extent and orientation to parameters such as matrix material heterogeneity, presence and distribution of discontinuities, and stress orientation is of particular interest, and we discuss this in the context of knowledge derived from both observation and simulation. The limitations of these studies will also be addressed in terms of resolution, uncertainty, and assumptions as well as the balance of fidelity to cost, both in computation time (for numerical studies) and equipment / operation cost (for observational studies). We also identify a number of current knowledge gaps and propose alternatives for addressing those gaps. We especially focus on the role of numerical studies for elucidating key concepts and system sensitivities. The problem is inherently multi-scale in both space and time as well as highly coupled hydromechanically, and, in several applications, thermally as well. We will summarize the developments to date in analyzing these systems and present an approach for advancing the capabilities of our models in the short- to long-term and how these advances can help provide solutions to reduce risk and improve efficiency of hydraulic fracturing operations. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Walsh, S. D.; Johnson, S.; Fu, P.; Settgast, R. R.

2011-12-01

130

The performance of hydraulically fractured stimulated wells in tight gas sands: A southern North Sea example  

SciTech Connect

The development of the tight gas sands in the northwest flank of Shell/Esso's Leman field required massive hydraulic fracture (MHF) stimulation. Well tests were commissioned to help understand the link between fracture design and performance. A statistical analysis of the test results gave credence to the hypotheses that hydraulic fractures connected these wells to a large natural fracture system, that the hydraulic fractures were semiradial in shape, and that a minimal productivity loss arose from the limited communication between wellbore and fracture. These results have assisted in further stimulation design.

Ovens, J.E.V.

1993-09-01

131

Application of a 3D hydraulic-fracturing simulator for design of acid-fracturing treatments  

SciTech Connect

Field experience during 1989--90 shows that application of a 3D hydraulic-fracturing simulator increases success of acid-fracturing well treatments. Fracture extension can be limited to the oil-bearing pay, maximum lateral extension can be realized within the height constraint, and acid/rock contact time can be increased by a factor of between 3 and 30. Oil-production response can be improved over other stimulation designs while water-production response can be limited. These methods have been applied in mature waterfloods of the Permian Basin and Cedar Creek anticline.

Morgenthaler, L.N. (Shell Development Co., Houston, TX (United States))

1994-02-01

132

Constraints on upward migration of hydraulic fracturing fluid and brine.  

PubMed

Recent increases in the use of hydraulic fracturing (HF) to aid extraction of oil and gas from black shales have raised concerns regarding potential environmental effects associated with predictions of upward migration of HF fluid and brine. Some recent studies have suggested that such upward migration can be large and that timescales for migration can be as short as a few years. In this article, we discuss the physical constraints on upward fluid migration from black shales (e.g., the Marcellus, Bakken, and Eagle Ford) to shallow aquifers, taking into account the potential changes to the subsurface brought about by HF. Our review of the literature indicates that HF affects a very limited portion of the entire thickness of the overlying bedrock and therefore, is unable to create direct hydraulic communication between black shales and shallow aquifers via induced fractures. As a result, upward migration of HF fluid and brine is controlled by preexisting hydraulic gradients and bedrock permeability. We show that in cases where there is an upward gradient, permeability is low, upward flow rates are low, and mean travel times are long (often >10? ?years). Consequently, the recently proposed rapid upward migration of brine and HF fluid, predicted to occur as a result of increased HF activity, does not appear to be physically plausible. Unrealistically high estimates of upward flow are the result of invalid assumptions about HF and the hydrogeology of sedimentary basins. PMID:23895673

Flewelling, Samuel A; Sharma, Manu

2014-01-01

133

The Role of the Rock on Hydraulic Fracturing of Tight Shales  

NASA Astrophysics Data System (ADS)

Successful economic production of oil and gas from nano-darcy-range permeability, tight shale reservoirs, is achieved via massive hydraulic fracturing. This is so despite their limited hydrocarbon in place, on per unit rock volume basis. As a reference, consider a typical average porosity of 6% and an average hydrocarbon saturation of 50% to 75%. The importance of tight shales results from their large areal extent and vertical thickness. For example, the areal extent of the Anwar field in Saudi Arabia of 3230 square miles (and 300 ft thick), while the Marcellus shale alone is over 100,000 square miles (and 70 to 150 ft thick). The low permeability of the rock matrix, the predominantly mineralized rock fabric, and the high capillary forces to both brines and hydrocarbons, restrict the mobility of pore fluids in these reservoirs. Thus, one anticipates that fluids do not move very far within tight shales. Successful production, therefore results from maximizing the surface area of contact with the reservoir by massive hydraulic fracturing from horizontal bore holes. This was the conceptual breakthrough of the previous decade and the one that triggered the emergence of gas shales, and recently oily shales, as important economic sources of energy. It is now understood that the process can be made substantially more efficient, more sustainable, and more cost effective by understanding the rock. This will be the breakthrough of this decade. Microseismic monitoring, mass balance calculations, and laboratory experiments of hydraulic fracturing on tight shales indicate the development of fracture complexity and fracture propagation that can not be explained in detail in this layered heterogeneous media. It is now clear that in tight shales the large-scale formation fabric is responsible for fracture complexity. For example, the presence and pervasiveness of mineralized fractures, bed interfaces, lithologic contacts, and other types of discontinuities, and their orientation in relation to the in-situ stresses, have a dominant role in promoting fracture branching and abrupt changes in direction. In general, the problem can be conceptualized as a competition between the effect of stresses (traditional mechanics of homogeneous media) and the effect of rock fabric (the mechanics of heterogeneous media). When the stress difference is low and the rock fabric pronounced, the rock fabric defines the direction of propagation. When the stress difference is high and the fabric is weak, the stress contrast dominates the process. In real systems, both effects compete and result in the complexity that we infer from indirect observations. In this paper we discuss the role of rock fabric on fracture complexity during hydraulic fracture propagation. We show that understanding the far field stresses is not enough to understand fracture propagation and complexity. Understanding the rock-specifically the larger-scale textural features that define the reservoir fabric-is fundamental to understand fracture complexity and fracture containment. We use laboratory experiments with acoustic emission localization to monitor fracturing and making inferences about the large-scale rock behavior. We also show that the fracture geometry, even for the same connected surface area, has significant well production and reservoir recovery implications.

Suarez-Rivera, R.; Green, S.; Stanchits, S.; Yang, Y.

2011-12-01

134

Importance of Stratabound Fracture Networks for Seismic Hazard Assessment of Hydraulic Fracturing  

NASA Astrophysics Data System (ADS)

Hydraulic fracturing, a powerful completion technique used to enhance oil or gas production from impermeable strata, may trigger unintended earthquake activity. The primary basis for assessment of triggered and natural seismic hazard is the classic Gutenberg-Richter (G-R) relation, which expresses scale-independent behavior of earthquake magnitudes. Using a stochastic approach to simulate microseismicity from three monitoring programs in North America, we show that magnitude-distance trends for microearthquakes induced by hydraulic fracturing may deviate significantly from the G-R relation. This apparent breakdown in the power-law scaling paradigm, coupled with unusually high values for the b-parameter (slope) of the G-R relation, can be explained by a new model based on activation of stratabound fracture networks in which fracture height growth is limited by mechanical bed thickness. For the three areas considered, mechanical bed thickness is well represented by a lognormal distribution, which leads asymptotically to a Gaussian decay for induced magnitudes that fits the observations remarkably well. This new relationship has profound implications for understanding the scaling behavior of induced microearthquakes, as well as for forecasting the probability of larger earthquakes triggered by hydraulic fracturing in oil and gas development.

Eaton, D. W.; Davidsen, J.; Pedersen, P. K.; Boroumand, N.

2013-12-01

135

MEASURING VERTICAL PROFILES OF HYDRAULIC CONDUCTIVITY WITH IN SITU DIRECT-PUSH METHODS  

EPA Science Inventory

U.S. EPA (Environmental Protection Agency) staff developed a field procedure to measure hydraulic conductivity using a direct-push system to obtain vertical profiles of hydraulic conductivity. Vertical profiles were obtained using an in situ field device-composed of a Geopr...

136

Friction pressures of proppant-laden hydraulic fracturing fluids  

SciTech Connect

Friction-pressure calculations of proppant-laden fluids are very important not only in the design of any hydraulic fracturing treatment but also in real-time monitoring of fracturing treatments. Recent advances in real-time fracture analysis have necessitated an accurate knowledge of bottomhole treating pressure (BHTP). To estimate BHTP, an accurate prediction of friction pressures of fluids in the flow conduit is required. This paper presents a new approach for predicting friction pressures of proppant-laden fracturing fluids that is based on an analytical method and uses nondimensional quantities in the analysis of flow data. From the flow data with various proppant-laden gels in multiple pipes, generalized correlations are developed and presented that incorporate such variables as proppant size, proppant density, proppant concentration, fluid density, flow rate, polymer gel concentration, and pipe size. These correlations are valid for a wide range of terminal Froude number, N/sub Fr/* (8.4 x 10/sup -3/ to 1.3 x 10/sup -4/), and particle Froude number, N/sub Frp/ (20 to 200). These ranges include the calculated values of N/sub Fr/* and N/sub Frp/ for the majority of hydraulic fracturing treatments conducted today. The correlations are verified by comparison of the estimations with data gathered in field-size tubing and field-gathered data. The predictions agree more closely with field data than previously published methods. Unlike previous studies, this investigation indicates that besides other factors, proppant size, pump rate, flow geometry, and polymer gel concentration play a significant role in the friction-pressure predictions of proppant-laden fluids.

Shah, S.N.; Lee, Y.N.

1986-11-01

137

Estimation of response of fracture system to hydraulic stimulation by induced microseismic multiplet analysis  

NASA Astrophysics Data System (ADS)

Development of a commercial geothermal power plant using an artificially stimulated reservoir is underway at Cooper Basin, Australia. In 2003, they have made the first stimulation where openhole section from 3667-4421m inside granitic basement was stimulated. Researchers in Tohoku University have collected more than 32,000 microseismic events while the stimulation using a monitoring network consists of 4 near surface stations (horizontal offset around 5-7 km from the injection well) and one downhole station near the injection well. Sub-horizontal hypocentral cloud with a thickness around 100-200m have been obtained by JHD in the previous studies (Asanuma et al., SEG Exp. Abst., 2005). In this study, the authors clustered and re-located microseismic multiplets using coherence evaluation in the frequency domain and DD relocation technique. Evaluation of coherency of the seismic traces at the onset of P-wave revealed that 99.9% of the events, which are not saturated and overlapped two events, were clustered into one multiplet cluster. This is because of strong low-pass characteristics of the earth transfer function and simple rupture process. The events were then sub-clustered into 26 groups by their polarity of the first break of P wave at each station. Integrated interpretation of the multiplets using fault plane solutions (FPS) by the composite focal mechanism, spatio-temporal distribution of the hypocenter, and critical stress state for shear slip was made in this study. Results from the analyses revealed that most of the multiplets occurred on sub-horizontal fractures, and some of the multiplet events (a few percent) are very likely to origin from sub-vertical fractures which connect the sub-horizontal fractures. It has been also showed that the events from sub-vertical fracture started to occur after seismic activity in one sub-horizontal fracture became high, and other sub-horizontal fracture was seismically activated after appearance of sub-vertical seismic structure. Kumano et al. (SEG Exp. Abst., 2006) have made coherence analysis of multiplets including coda, and reported that two or three sub-parallel and sub-horizontal fractures were mainly stimulated at this site. It has been reported that several sub-horizontal permeable fractures have been found inside the basement rock while drilling of the injection well, and most of the pre-existing fractures were plugged by cement except for one. Integrated interpretation of the observed facts and results from the microseismic analysis is that (a) an existing fracture connected to the injection well was firstly stimulated, then (b) increased pore-pressure in the fracture induced shear slip on sub-vertical fractures and permeability improved, and (c) horizontal fractures, which were hydraulically connected by the sub-vertical fractures, were stimulated and seismically activated. A combination of multiplet analysis, FPS, and critical pore pressure was effectively used to interpret behavior of simulated fracture system.

Asanuma, H.; Kenmoku, Y.; Kawamura, Y.; Niitsuma, H.; Wyborn, D.

2009-12-01

138

Rock Springs Site 12 Hydraulic/Explosive True in Situ Oil Shale Fracturing Experiment.  

National Technical Information Service (NTIS)

The experiment plan involved the creation and characterization of three horizontal hydraulic fractures, followed by the insertion and simultaneous detonation of slurry explosive in the two lower fractures. Core analyses, wellbore logging, and airflow and ...

R. L. Parrish R. R. Boade A. L. Stevens A. Long T. F. Turner

1980-01-01

139

Mapping the Isotropic Component of Focal Mechanisms in Hydraulic Fractures  

NASA Astrophysics Data System (ADS)

We present the results of a hydraulic fracture monitoring study where the events induced by the treatment are recorded with a three-dimensional sensor distribution. The fact that the microseismicity is recorded over multiple azimuths allows not only for better convergence of the location algorithm, but also acheives sufficient coverage of the focal sphere to reliably invert for the full moment tensor. Unlike in tectonic settings, many of these focal mechanisms have very strong non-double-couple components, due to the intrusion of proppants into the surrounding rock, and are thus characterized by mechanisms consistant with tensile cracks opening or closing. Mapping these mechanisms in time and space offers insight into both the processes responsible for the fracturing, but also how effectively the treatment propped open the rock and identifying which areas may have opened and subsequently closed.

Baig, A. M.; Urbancic, T. I.

2009-12-01

140

Hydraulic Fracturing, Wastewater Injection and Unintended Earthquakes (Invited)  

NASA Astrophysics Data System (ADS)

It has long been known that increasing the pore pressure within a pre-stressed fault can induce an earthquake by reducing the effective normal stress and thereby the frictional strength of the fault. Underground fluid pressures are routinely modified by a wide range of industrial activities including impoundment of reservoirs, mining, and petroleum production, all of which are known to have potential for inducing earthquakes. Recently, attention has been drawn to the earthquake hazard associated with the production of oil and gas from previously unproductive formations. Earthquakes can be induced as part of the process to stimulate the production from tight shale formations, or by disposal of wastewater associated with stimulation and production. In this talk, I review recent investigations of both activities with a focus on the emerging understanding of the development of predictive models for both seismicity and risk. By design, hydraulic fracturing induces numerous high-frequency microseismic events as part of the process of creating a connected fracture network to enhance formation permeability. During the brief time (hours) that high fluid pressure is applied to the well bore, seismic events occur as a combination tensile (hydrofracture) and shear (hydroshear) failures. The fluid volume injected in a single hydrofrac stage is commonly of the order of several thousand cubic meters. Growth of the fracture network typically follows square-root scaling with time, suggesting a diffusive growth mechanism. Magnitudes are normally below zero for events in the target formation. Larger, unintended events sometimes occur and available evidence points to shear failure of pre-existing faults as their source. Earthquakes with magnitudes as large as Mw 3.6 occurred during hydraulic fracturing operations in the Horn River Basin, B. C., Canada. Some of these occurred before the diffusive pressure front would have reached the hypocenter, suggesting rapid transmission of pore pressure through conductive fractures or faults. In contrast with hydraulic fracturing treatments, wastewater wells commonly inject fluid for years or decades, with cumulative volumes occasionally in excess of 1 million cubic meters. By design, wastewater injection should never induce hydraulic fractures, as regulations require injection pressures to be less than the fracture pressure. Avoiding earthquakes has proven to be more problematic, at least for a small percentage of the more than 30,000 UIC Class II wells in the U.S. that are licensed for wastewater disposal. Case studies of some of the larger of the recent earthquakes induced by wastewater injection suggest triggering by transmission of the pore pressure increase to well-oriented faults in the basement. Ultimately, better knowledge of the stress and pressure conditions at depth; the hydrogeologic framework, including the presence and geometry of faults; and the location and mechanisms of natural seismicity at a few sites will be needed to develop a predictive understanding of the hazard posed by induced earthquakes.

Ellsworth, W. L.

2013-12-01

141

Modelling of of hydraulic fractures trajectories in inhomogeneous stress field  

NASA Astrophysics Data System (ADS)

The paper examines an actual problem of oil and gas production -- modelling of the hydro-fracture trajectories depending on ihomogeneous distributions of pore pressure. The results could serve for improvement of the design of hydraulic fracturing in the oil/gas fields. The methods of the plane elasticity theory and fracture mechanics are employed. It is assumed, that in addition to the homogeneous field of natural stress the reservoir is also subjected to additional stresses caused by technological reasons, which makes the total stress field to be inhomogeneous. Therefore, the objective is to model a curvilinear crack path in an elastic inhomogeneous-loaded plane depending on the different mechanical parameters that control the stress state of the reservoir. For the simulation of the trajectory of a crack the method of boundary integral equation is used. The algorithms of step-by-step determination of the crack's trajectory development using the criterion of maximum tensile stresses at the end of the cracks have been developed. For the numerical realization of the solution we used a special modification of the method of mechanical quadratures providing effective and fast solution of the corresponding system of singular integral equation. The solution for the hydro-fracture path have been simulated for the case of inhomogeneous stress field due to presence of injection well for several physical models.

Andreev, A. A.; Galybin, A.

2013-05-01

142

The Use of Hydraulic Head and Atmospheric Tritium to Identify Presence of Fractures in Clayey Aquitards: Numerical Analysis  

Microsoft Academic Search

Surficial clayey aquitards can provide underlying aquifers with strong protection from contamination if vertically connected open fractures are absent. Hence, methods are needed to identify such contaminant pathways. An existing two-dimensional model for steady-state groundwater flow and solute transport (FRACTRAN) was used for cross-sectional simulations to assess the prospects for using field measurements of hydraulic head and atmospheric (i.e. bomb)

E. A. Farah; B. L. Parker; J. A. Cherry

2003-01-01

143

Monitoring increases in fracture connectivity during hydraulic stimulations from temporal variations in shear wave splitting polarization  

NASA Astrophysics Data System (ADS)

Hydraulic overpressure can induce fractures and increase permeability in a range of geological settings, including volcanological, glacial and petroleum reservoirs. Here we consider an example of induced hydraulic fracture stimulation in a tight-gas sandstone. Successful exploitation of tight-gas reservoirs requires fracture networks, either naturally occurring, or generated through hydraulic stimulation. The study of seismic anisotropy provides a means to infer properties of fracture networks, such as the dominant orientation of fracture sets and fracture compliances. Shear wave splitting from microseismic data acquired during hydraulic fracture stimulation allows us to not only estimate anisotropy and fracture properties, but also to monitor their evolution through time. Here, we analyse shear wave splitting using microseismic events recorded during a multistage hydraulic fracture stimulation in a tight-gas sandstone reservoir. A substantial rotation in the dominant fast polarization direction (?) is observed between the events of stage 1 and those from later stages. Although large changes in ? have often been linked to stress-induced changes in crack orientation, here we argue that it can better be explained by a smaller fracture rotation coupled with an increase in the ratio of normal to tangential compliance (ZN/ZT) from 0.3 to 0.6. ZN/ZT is sensitive to elements of the internal architecture of the fracture, as well as fracture connectivity and permeability. Thus, monitoring ZN/ZT with shear wave splitting can potentially allow us to remotely detect changes in permeability caused by hydraulic stimulation in a range of geological settings.

Baird, Alan F.; Kendall, J.-Michael; Verdon, James P.; Wuestefeld, Andreas; Noble, Todd E.; Li, Yongyi; Dutko, Martin; Fisher, Quentin J.

2013-11-01

144

Application of harmonic analysis of water levels to determine vertical hydraulic conductivities in clay-rich aquitards.  

PubMed

A harmonic analysis method was used to determine vertical hydraulic conductivities (Kv) in geologic media between vertically separated piezometers using water level measurements. In this method, each water level time series was filtered and then decomposed using harmonic analysis into a sum of trigonometric components. The phase and amplitude of each harmonic function were calculated. These data were used to estimate Kv values between vertically separated data sets assuming one-dimensional transient flow. The method was applied to water level data collected from nested piezometers at two thick clay-rich till aquitards in Saskatchewan, Canada. At one site, routine water levels were measured in 12 piezometers (installed between 1 and 29 m below ground surface) since installation (1995). At the other site, water levels were measured in seven piezometers (installed between 4 and 53 m below ground surface) since installation (1998-1999). The Kv calculated using harmonic analysis decreased with depth below the water table at both sites, approaching matrix estimates of hydraulic conductivity between 10 and 11 m and between 21 and 43 m below ground surface. These depths reflected the depth of extensive vertical fracturing at the sites and showed that the depth of fracturing may be site specific. PMID:12873014

Boldt-Leppin, Brigitte E J; Hendry, M Jim

2003-01-01

145

Calculation of vertical fracture containment in layered formations  

SciTech Connect

An analytic procedure for calculating vertical fracture extent in symmetrical trilayered formations was extended to multilayered, asymmetrical formations using a semianalytic technique. The fracture extends computed by this method were compared with those calculated with the finite-element method. It was found that even for modulus variations between layers as large as a factor of 5, the semianalytic procedure gave exactly the same results as the finite-element solution in a fraction of the computation time and with significantly less manual data manipulation. It is recommended that the analytic and numerical procedures be used in a complementary manner to calculate fracture-width profiles in layered formations.

Fung, R.L.; Vijayakumar, S.; Cormack, D.E.

1987-12-01

146

Estimation of vertical fracturing from measured elastic moduli  

NASA Astrophysics Data System (ADS)

A finely layered medium or a system of parallel fractures in an otherwise homogeneous elastic background renders the medium anisotropic for long wavelengths. The anisotropy increases in complexity as the number of different systems incorporated into the medium increases. Using the group calculus formulation for layered media developed by Schoenberg and Muir, the effects of the individual constituents can be separated arithmetically after the properties of each constituent are transformed. When orthorhombic behavior results from a set of parallel fractures perpendicular to closely spaced bedding planes, the contribution of the fractures to the elastic stiffness matrix can be removed. The average fracture compliances can be evaluated by requiring the background to be transversely isotropic. The remaining stiffness matrix gives the elastic properties of the transversely isotropic background as if the background had no vertical fractures.

Hood, Julie A.; Schoenberg, Michael

1989-11-01

147

Fate of hydraulic fracturing chemicals under down-hole conditions  

NASA Astrophysics Data System (ADS)

Hydraulic fracturing is a method to increase the yield of oil and natural gas extraction from unconventional rock formations. The process of hydrofracturing occurs via injecting water, sand, and chemicals into the production well and subjecting this mixture to high pressures to crack the rock shale, allowing increased amounts of gas and oil to seep out of the target formation. Typical constituents of the chemical mixtures are biocides, which are applied to inhibit growth of sulfate reducing bacteria in order to prevent pipe corrosion and production of hazardous gases. However, very little is known about the persistence, fate, and activity of biocides when subjected to the high temperatures and pressures of down-hole conditions. Thus, the objective of this talk is to present data from ongoing experiments focused on determining the fate of biocides commonly used for hydraulic fracturing under conditions simulating down-hole environments. Using stainless steel reactors, the high pressures and temperatures of down-hole conditions in the Marcellus shale are simulated, while concentration, speciation, and degradation of priority biocides are observed as a function of time, using primarily LC/MS techniques. The impact of water quality, shale, temperature, and pressure on the transformation kinetics and pathways of biocides will be discussed. Finally, field samples (both sediments and flowback brine) from the Marcellus shale are analyzed to verify that our lab simulations mirror real-life conditions and results.

Blotevogel, J.; Kahrilas, G.; Corrin, E. R.; Borch, T.

2013-12-01

148

Hydraulic fracturing and wellbore completion of coalbed methane wells in the Powder River Basin, Wyoming: Implications for water and gas production  

SciTech Connect

Excessive water production (more than 7000 bbl/month per well) from many coalbed methane (CBM) wells in the Powder River Basin of Wyoming is also associated with significant delays in the time it takes for gas production to begin. Analysis of about 550 water-enhancement activities carried out during well completion demonstrates that such activities result in hydraulic fracturing of the coal. Water-enhancement activities, consists of pumping 60 bbl of water/min into the coal seam during approximately 15 min. This is done to clean the well-bore and to enhance CBM production. Hydraulic fracturing is of concern because vertical hydraulic fracture growth could extend into adjacent formations and potentially result in excess CBM water production and inefficient depressurization of coals. Analysis of the pressure-time records of the water-enhancement tests enabled us to determine the magnitude of the least principal stress (S{sub 3}) in the coal seams of 372 wells. These data reveal that because S{sub 3} switches between the minimum horizontal stress and the overburden at different locations, both vertical and horizontal hydraulic fracture growth is inferred to occur in the basin, depending on the exact location and coal layer. Relatively low water production is observed for wells with inferred horizontal fractures, whereas all of the wells associated with excessive water production are characterized by inferred vertical hydraulic fractures. The reason wells with exceptionally high water production show delays in gas production appears to be inefficient depressurization of the coal caused by water production from the formations outside the coal. To minimize CBM water production, we recommend that in areas of known vertical fracture propagation, the injection rate during the water-enhancement tests should be reduced to prevent the propagation of induced fractures into adjacent water-bearing formations.

Colmenares, L.B.; Zoback, M.D. [Stanford University, Stanford, CA (United States). Dept. of Geophysics

2007-01-15

149

Field Experiments in a Fractured Clay Till: 1. Hydraulic Conductivity and Fracture Aperture  

Microsoft Academic Search

Field values of horizontal hydraulic conductivity measured in the upper 1.5–5.5 m of a weathered and fractured clay-rich till were strongly influenced by smearing around piezometer intakes, which occurs during augering, and by the physical scale of the measuring device. Values measured in conventional augered piezometers were typically 1–2 orders of magnitude lower than those measured in piezometers designed to

Larry D. McKay; John A. Cherry; Robert W. Gillham

1993-01-01

150

Field experiments in a fractured clay till. 1. Hydraulic conductivity and fracture aperture  

Microsoft Academic Search

Field values of horizontal hydraulic conductivity measured in the upper 1.5-5.5 m of a weathered and fractured clay-rich till were strongly influenced by smearing around piezometer intakes, which occurs during augering, and by the physical scale of the measuring device. Values measured in conventional augered piezometers were typically 1-2 orders of magnitude lower than those measured in piezometers designed to

Larry D. McKay; John A. Cherry; Robert W. Gillham

1993-01-01

151

Field experiments in a fractured clay till: 1. Hydraulic conductivity and fracture aperture  

Microsoft Academic Search

Field values of horizontal hydraulic conductivity measured in the upper 1.5–5.5 m of a weathered and fractured clay-rich till were strongly influenced by smearing around piezometer intakes, which occurs during augering, and by the physical scale of the measuring device. Values measured in conventional augered piezometers were typically 1–2 orders of magnitude lower than those measured in piezometers designed to

Larry D. McKay; John A. Cherry; Robert W. Gillham

1993-01-01

152

OVERCOMING THE LIMITATIONS OF IN SITU BIOREMEDIATION IN LOW PERMEABILITY SOILS THROUGH HYDRAULIC SOIL FRACTURING  

Microsoft Academic Search

Hydraulic Soil Fracturing is a process that is used to enhance the in situ remediation of contaminants present in low permeability soils (i.e. soils with a hydraulic conductivity of less than 10-6 m\\/s). Soil fracturing has been successfully applied since the early 1990's to accelerate site clean-ups using physical \\

Gordon H. Bures; Kent S. Sorenson; Jennifer P. Martin; Richard F. Reinke

153

Final Plan to Study the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources  

EPA Science Inventory

The overall purpose of this study is to elucidate the relationship, if any, between hydraulic fracturing and drinking water resources. More specifically, the study has been designed to assess the potential impacts of hydraulic fracturing on drinking water resources and to identif...

154

Reviews of Science for Science Librarians: Hydraulic Fracturing: Geological, Engineering, and Environmental Literature  

Microsoft Academic Search

Hydraulic fracturing, an engineering process used to access previously unreachable reservoirs of oil and natural gas, is currently the subject of much interest and debate in local and national media. This article examines the literature of hydraulic fracturing from geological, engineering, and environmental perspectives. This growing body of literature includes academic journals, trade publications, newspaper and magazine articles, and websites.

James Bierman; Christina Kulp; Jody Bales Foote

2011-01-01

155

Plan to Study the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources (Monterey, CA)  

EPA Science Inventory

A summary of EPA's research relating to potential impacts of hydraulic fracturing on drinking water resources will be presented. Background about the study plan development will be presented along with an analysis of the water cycle as it relates to hydraulic fracturing processe...

156

78 FR 34611 - Oil and Gas; Hydraulic Fracturing on Federal and Indian Lands  

Federal Register 2010, 2011, 2012, 2013

...WO-300-L13100000.FJ0000] RIN 1004-AE26 Oil and Gas; Hydraulic Fracturing on Federal and Indian Lands AGENCY: Bureau of...the Federal Register a proposed rule to regulate hydraulic fracturing on Federal and Indian land. Due to the...

2013-06-10

157

A Study of Hydraulic Fracture Conductivity and Its Dependence on Proppant Wettability  

Microsoft Academic Search

Engineering design of hydraulic fracturing proppants typically focuses on maximizing permeability retention under stress, resistance to high temperatures, and controlling properties such as specific gravity and particle size; less attention is paid to the proppant's wetting characteristics and their potential impact on the deliverability of a hydraulic fracture. The purpose of this work is to investigate the effect of proppant

T. Mora; O. A. Orogbemi; Z. T. Karpyn

2010-01-01

158

LIMITING DRILLING SLURRY PRESSURES TO CONTROL HYDRAULIC FRACTURING DURING HDD THROUGH PURELY COHESIVE SOIL  

Microsoft Academic Search

Hydraulic fracturing is a problem associated with Horizontal Directional Drilling that is still inadequately understood and can result in serious consequences. During insertion of utility conduits and other buried pipe infrastructure, drilling slurry is used to stabilize the soil around the excavation zone prior to pulling the new pipeline into place. Hydraulic fracturing occurs when the drilling slurry flows through

Matthew J. Kennedy; Graeme D. Skinner; Ian D. Moore

159

Identifying fracture-zone geometry using simulated annealing and hydraulic-connection data  

USGS Publications Warehouse

A new approach is presented to condition geostatistical simulation of high-permeability zones in fractured rock to hydraulic-connection data. A simulated-annealing algorithm generates three-dimensional (3-D) realizations conditioned to borehole data, inferred hydraulic connections between packer-isolated borehole intervals, and an indicator (fracture zone or background-K bedrock) variogram model of spatial variability. We apply the method to data from the U.S. Geological Survey Mirror Lake Site in New Hampshire, where connected high-permeability fracture zones exert a strong control on fluid flow at the hundred-meter scale. Single-well hydraulic-packer tests indicate where permeable fracture zones intersect boreholes, and multiple-well pumping tests indicate the degree of hydraulic connection between boreholes. Borehole intervals connected by a fracture zone exhibit similar hydraulic responses, whereas intervals not connected by a fracture zone exhibit different responses. Our approach yields valuable insights into the 3-D geometry of fracture zones at Mirror Lake. Statistical analysis of the realizations yields maps of the probabilities of intersecting specific fracture zones with additional wells. Inverse flow modeling based on the assumption of equivalent porous media is used to estimate hydraulic conductivity and specific storage and to identify those fracture-zone geometries that are consistent with hydraulic test data.

Day-Lewis, F. D.; Hsieh, P. A.; Gorelick, S. M.

2000-01-01

160

TECHNOLOGY EVALUATION AND APPLICATIONS ANALYSIS REPORT: UNIVERSITY OF CINCINNATI/RISK REDUCTION ENGINEERING LABORATORY - HYDRAULIC FRACTURING TECHNOLOGY  

EPA Science Inventory

Two pilot-scale demonstrations of the hydraulic fracturing technology for enhancing the permeability of contaminated silty clays have been evaluated under the Superfund Innovative Technology Evaluation (SITE) Program.The hydraulic fracturing technology was demonstrated in 1991 an...

161

Periodontal healing after bonding treatment of vertical root fracture.  

PubMed

Vertical root fractures lead to advanced periodontal breakdown with deep periodontal pockets and vertical bone defects. The purpose of this study is to evaluate clinically the periodontal healing of root fracture treatment using adhesive resin cement. In 22 patients, 23 teeth with vertical root fractures were treated with 4-META/MMA-TBB resin cement. Eleven fractured roots were bonded through the root canal (group A) and 12 fractured roots were bonded extra-orally and replanted (group B). All teeth were then restored with full cast crowns (n=20) or coping (n=3). Mean probing depth was 6.6 mm at pre-treatment and 4.4 mm 6 months after the treatment in group A, and 7.4 mm and 4.6 mm, respectively, in group B. Bleeding scores were 100% at pre-treatment and 36.4% after 6 months in group A and 91.7% and 8.3%, respectively in group B. Radiographic bone level was 56.8% at pretreatment and 59.1% after 6 months in group A, and 18.8% and 29.2%, respectively, in group B. Two roots of group A and three roots of group B were extracted due to refracture, deterioration of periodontal inflammation, mobility, and luxation. The remaining roots (n=18) presented no discomfort to the patients and there was no deterioration of periodontal conditions over a mean period of 33 months (range 14-74 months) in group A and over a mean period of 22 months (range 6-48 months) in group B. There was no ankylosed teeth nor was any root resorption detected. The results suggested that the treatment of vertical root fracture using 4-META/MMA-TBB resin has good prognostic possibilities. PMID:11585144

Sugaya, T; Kawanami, M; Noguchi, H; Kato, H; Masaka, N

2001-08-01

162

Hydraulic Fracture Extending into Network in Shale: Reviewing Influence Factors and Their Mechanism  

PubMed Central

Hydraulic fracture in shale reservoir presents complex network propagation, which has essential difference with traditional plane biwing fracture at forming mechanism. Based on the research results of experiments, field fracturing practice, theory analysis, and numerical simulation, the influence factors and their mechanism of hydraulic fracture extending into network in shale have been systematically analyzed and discussed. Research results show that the fracture propagation in shale reservoir is influenced by the geological and the engineering factors, which includes rock mineral composition, rock mechanical properties, horizontal stress field, natural fractures, treating net pressure, fracturing fluid viscosity, and fracturing scale. This study has important theoretical value and practical significance to understand fracture network propagation mechanism in shale reservoir and contributes to improving the science and efficiency of shale reservoir fracturing design.

Ren, Lan; Zhao, Jinzhou; Hu, Yongquan

2014-01-01

163

Hydraulic fracture extending into network in shale: reviewing influence factors and their mechanism.  

PubMed

Hydraulic fracture in shale reservoir presents complex network propagation, which has essential difference with traditional plane biwing fracture at forming mechanism. Based on the research results of experiments, field fracturing practice, theory analysis, and numerical simulation, the influence factors and their mechanism of hydraulic fracture extending into network in shale have been systematically analyzed and discussed. Research results show that the fracture propagation in shale reservoir is influenced by the geological and the engineering factors, which includes rock mineral composition, rock mechanical properties, horizontal stress field, natural fractures, treating net pressure, fracturing fluid viscosity, and fracturing scale. This study has important theoretical value and practical significance to understand fracture network propagation mechanism in shale reservoir and contributes to improving the science and efficiency of shale reservoir fracturing design. PMID:25032240

Ren, Lan; Zhao, Jinzhou; Hu, Yongquan

2014-01-01

164

The vertical hydraulic conductivity of an aquitard at two spatial scales.  

PubMed

Aquitards protect underlying aquifers from contaminants and limit recharge to those aquifers. Understanding the mechanisms and quantity of ground water flow across aquitards to underlying aquifers is essential for ground water planning and assessment. We present results of laboratory testing for shale hydraulic conductivities, a methodology for determining the vertical hydraulic conductivity (K(v)) of aquitards at regional scales and demonstrate the importance of discrete flow pathways across aquitards. A regional shale aquitard in southeastern Wisconsin, the Maquoketa Formation, was studied to define the role that an aquitard plays in a regional ground water flow system. Calibration of a regional ground water flow model for southeastern Wisconsin using both predevelopment steady-state and transient targets suggested that the regional K(v) of the Maquoketa Formation is 1.8 x 10(-11) m/s. The core-scale measurements of the K(v) of the Maquoketa Formation range from 1.8 x 10(-14) to 4.1 x 10(-12) m/s. Flow through some additional pathways in the shale, potential fractures or open boreholes, can explain the apparent increase of the regional-scale K(v). Based on well logs, erosional windows or high-conductivity zones seem unlikely pathways. Fractures cutting through the entire thickness of the shale spaced 5 km apart with an aperture of 50 microns could provide enough flow across the aquitard to match that provided by an equivalent bulk K(v) of 1.8 x 10(-11) m/s. In a similar fashion, only 50 wells of 0.1 m radius open to aquifers above and below the shale and evenly spaced 10 km apart across southeastern Wisconsin can match the model K(v). PMID:16556202

Hart, David J; Bradbury, Kenneth R; Feinstein, Daniel T

2006-01-01

165

Hydraulic Fracture Propagation through Preexisting Discontinuity Monitored by Acoustic Emission and Ultrasonic Transmission  

NASA Astrophysics Data System (ADS)

Hydraulic fracturing is critical to enhance hydrocarbon production from ultra-low permeability unconventional reservoirs, and is the common completion methodology for tight formations around the world. Unfortunately, these reservoirs are often highly heterogeneous and their heterogeneity imparts a degree of geometrical complexity in hydraulic fractures that is poorly understood. Fracture complexity (e.g. branching) results in higher surface area and could be beneficial to production provided it remains conductive. Understanding the sources and consequences of fracture complexity is thus of high importance to completion and production operations. In this study we postulate that textural complexity in tight heterogeneous formations induces fracture complexity, and that the main sources of textural complexity are associated with veins, bed boundaries, lithologic contacts, and geologic interfaces. We thus study the effect of interfaces on hydraulic fracture propagation under laboratory conditions by Acoustic Emission (AE) and Ultrasonic Transmission (UT) monitoring techniques. The experiments were conducted on low permeability sandstone blocks of 279 x 279 x 381 mm length with saw cut discontinuities oriented orthogonally to the expected direction of fracture propagation. The rock is loaded in a poly-axial test frame to representative effective in-situ stress conditions of normal and deviatoric stress. Hydraulic fracturing was initiated by injection of silicon oil into a borehole drilled off center from the block. Acoustic emission (AE) events were continuously monitored during testing using nineteen P-wave sensors. Additional sensors were installed to periodically monitor ultrasonic transmission (UT) along various directions oblique and perpendicular to the fracture and the interface. The AE and UT data were recorded using a Vallen AMSY-6 system, with 16-bit amplitude resolution and 5 MHz sampling rate. Detailed analysis of AE localizations allowed us to identify various stages of hydraulic fracturing, including fracture initiation, fracture interaction with the preexisting interface, fracture propagation and fracture closing. Observed variations in UT amplitudes and velocities, during fracture propagation, were related to fracture propagation, as well as to the penetration of fracturing fluid to the conductive interface. Analysis of the combined AE and UT data provides additional insight into the fracturing process and significantly improved our understanding of the dynamics of hydraulic fracture propagation. Detailed post-test 3D mapping of the final fracture allowed us to make an independent comparison of actual fracture and the fracture monitored by the AE and UT measurements. This comparison is essential for validating the interpretation of microseismic monitoring during hydraulic fracturing in the lab and in the field.

Stanchits, S.; Lund, J.; Surdi, A.; Edelman, E.; Whitney, N.; Eldredge, R.; Suarez-Rivera, R.

2011-12-01

166

EVALUATION OF METHOD FOR DETERMINING THE VERTICAL DISTRIBUTION OF HYDRAULIC CONDUCTIVITY  

EPA Science Inventory

Six borehole methods for determining the vertical distribution of hydraulic conductivity in unconsolidated geologic formations are evaluated. taddle packer tests are inappropriate of there is a hydraulic path around the packer on the outside of the well screen. Methods based on g...

167

True vertical tooth root fracture: Case report and review  

PubMed Central

It is important for the clinician not only to gather as much information about a case as possible, but also to be able to correctly interpret the data to arrive at an accurate diagnosis. Occasionally, a case presents with symptoms that might be suggestive of a condition; however, the final diagnosis may be totally different. This paper reports on an interesting case of a true vertical root fracture, in an intact maxillary molar in a 55-year-old man. The case was misdiagnosed and treated as a periodontal defect for over two months. The paper discusses the various causes and diagnostic dilemmas of root fractures.

Bhaskar, U.; Logani, A.; Shah, Naseem

2011-01-01

168

Discussion of examination of a cored hydraulic fracture in a deep gas well  

SciTech Connect

Warpinski et al. document information found from a core through a formation after a hydraulic fracture treatment. As they indicate, the core provides the first detailed evaluation of an actual propped hydraulic fracture away from the well and at a significant depth, and this evaluation leads to findings that deviate substantially from the assumptions incorporated into current fracturing models. In this discussion, a defense of current fracture design assumptions is developed. The affirmation of current assumptions, for general industry applications, is based on an assessment of the global impact of the local complexity found in the core. The assessment leads to recommendations for the evolution of fracture design practice.

Nolte, K.G. (Dowell Schlumberger, Tulsa, OK (United States))

1993-08-01

169

Multiple vertical fractures from an inclined wellbore--a field experiment  

Microsoft Academic Search

A procedure is described in which multiple, vertical fractures are created from a single, directionally drilled well bore. The purpose is to increase fracture area over what can be achieved from a single vertical fracture initiated from a conventional vertical well bore. This will provide for more rapid and efficient drainage of a specific reservoir volume. A field experiment to

M. K. Strubhar; J. L. Fitch; E. E. Jr. Glenn

1974-01-01

170

Vertically Oriented Femoral Neck Fractures: Mechanical Analysis of Four Fixation Techniques  

Microsoft Academic Search

Objective: Femoral neck fractures inyoung individuals are typically high angled shear fractures. These injuries are difficult to stabilize due to a strong varus displacement force across the hip with weight bearing. The purpose of this study was to compare the biomechanical stability of four differing fixation techniques for stabilizing vertical shear femoral neck fractures. Methods: Vertical femoral neck fracture stability

Arash Aminian; Fan Gao; Wasyl W. Fedoriw; Li-Qun Zhang; David M. Kalainov; Bradley R. Merk

2007-01-01

171

Massive Hydraulic Fracture Design for the East Texas Cotton Valley Sands  

Microsoft Academic Search

The paper provides Amoco's current understanding of fracturing in the East Texas Cotton Valley Sands, outlines the massive hydraulic fracture (MHF) procedure used by Amoco, and documents the changes in the company's MHF stimulation designs in recent years. The subjects discussed include geology and reservoir properties; the effect of fracture length on gas recovery; leak-off control; pump rate scheduling; proppant

Bernard Schlottman; William Miller II; R. K. Lueders

1981-01-01

172

Theoretical size of hydraulically induced horizontal fractures and corresponding surface uplift in an idealized medium  

Microsoft Academic Search

For the disposal of radioactive wastes by hydraulic fracturing and grout injection, it is considered essential that the induced fractures be nearly horizontal. Bottom-hole injection pressure in excess of overburden pressure has been recognized as one indication that fracturing is horizontal. The amount of uplift of the ground surface caused by the injection can be used as another indicator. For

Ren Jen Sun

1969-01-01

173

Hydraulic fracture initiation and propagation: roles of wellbore trajectory, perforation and stress regimes  

Microsoft Academic Search

This paper develops a generic model for predicting hydraulic fracture initiation from arbitrarily oriented wellbores. For a given in-situ stress condition and wellbore orientation parameters, the model predicts the fracture initiation pressure and the orientation and location of fractures on the wellbore wall. The model has been applied in a series of in-situ stress conditions to study the effect of

M. M Hossain; M. K Rahman; S. S Rahman

2000-01-01

174

Fracture fluid flow properties investigation using GPR and hydraulic testing methods  

Microsoft Academic Search

Characterization of the fluid flow properties of fractures is of particular interest because fractures rapidly transmit fluids, such as groundwater, contaminants and hydrocarbons. We investigate the use of ground-penetrating radar (GPR) and hydraulic testing to characterize groundwater flow variability along two prominent horizontal fracture planes in a carbonate aquifer. Three-dimensional radar reflection surveying provided high- resolution imaging of the two

Georgios P. Tsoflias; T. Halihan; M. A. Muldoon

2004-01-01

175

Constrained Hydraulic Fracture Optimization Improves Recovery from Low Permeable Oil Reservoirs  

Microsoft Academic Search

The petroleum industry needs cost-effective hydraulic fracturing technique to increase recovery from low permeable reservoirs. That leads to the widespread use of various fracture optimization methods to find optimum values of controllable treatment design parameters. Inappropriate values of these parameters cause uncontrolled fracture, resulting in unnecessarily high treatment cost and finally low productivity. Application of the designed treatment parameters obtained

M. M. Rahman

2008-01-01

176

Application of microseismic technology to hydraulic fracture diagnostics: GRI/DOE Field Fracturing Multi-Sites Project  

SciTech Connect

The objective of the Field Fracturing Multi-Sites Project (M-Site) is to conduct field experiments and analyze data that will result in definitive determinations of hydraulic fracture dimensions using remote well and treatment well diagnostic techniques. In addition, experiments will be conducted to provide data that will resolve significant unknowns with regard to hydraulic fracture modeling, fracture fluid rheology and fracture treatment design. These experiments will be supported by a well-characterized subsurface environment as well as surface facilities and equipment conducive to acquiring high-quality data. It is anticipated that the project`s research advancements will provide a foundation for a fracture diagnostic service industry and hydraulic fracture optimization based on measured fracture response. The M-Site Project is jointly sponsored by the Gas Research Institute (GRI) and the US Department of Energy (DOE). The site developed for M-Site hydraulic fracture experimentation is the former DOE Multiwell Experiment (MWX) site located near Rifle, Colorado. The MWX project drilled three closely-spaced wells (MWX-1, MWX-2 and MWX-3) which were the basis for extensive reservoir analyses and tight gas sand characterizations in the blanket and lenticular sandstone bodies of the Mesaverde Group. The research results and background knowledge gained from the MWX project are directly applicable to research in the current M-Site Project.

Wilmer, R. [CER Corp., Las Vegas, NV (United States); Warpinski, N.R. [Sandia National Laboratories (United States); Wright, T.B. [Resources Engineering Systems (United States); Branagan, P.T. [Branagan & Associates (United States); Fix, J.E. [Fix & Associates (United States)

1995-06-01

177

Effect of reeds and feeding operations on hydraulic behaviour of vertical flow constructed wetlands under hydraulic overloads  

Microsoft Academic Search

Vertical flow constructed wetlands (VFCWs) have been very successful in France over the last 5 years. The sizing of VFCWs is still roughly based on organic load acceptance with slight clear water intrusion into the sewerage system which is often wrong in the context of small communities. To specify the hydraulic limits would be of great help to Water Authorities

P. Molle; A. Liénard; A. Grasmick; A. Iwema

2006-01-01

178

Laboratory imaging of stimulation fluid displacement from hydraulic fractures  

SciTech Connect

Laboratory experiments were conducted to physically investigate the processes governing stimulation fluid displacement from hydraulic fractures. Experiments were performed on two scales: meter-scale in a 1500 cm{sup 2} sand pack and core-scale in a 65 cm{sup 2} API linear conductivity cell. High-resolution light transmission imaging was employed at the meter-scale to visualize and quantify processes governing fluid displacement. For comparison, complimentary tests were performed using an API conductivity cell under ambient test conditions and at elevated closure stress. In these experiments viscous fingering and gravity drainage were identified as the dominant processes governing fluid displacement. Fluid viscosity was found to dictate the relative importance of the competing displacement processes and ultimately determine the residual liquid saturation of the sand pack. The process by which fluid displacement occurs was seen to effect the shape of both the gas and liquid phase relative permeability functions. Knowledge of such viscosity/relative permeability relationships may prove useful in bounding predictions of post-stimulation recovery of gels from the fracture pack.

Tidwell, V. [Sandia National Lab., Albuquerque, NM (United States); Parker, M. [SPE, Richardson, TX (United States)

1996-11-01

179

Economic recovery of oil trapped at fan margins using high-angle wells and multiple hydraulic fractures. [Quarterly report], January 1--March 31, 1996  

SciTech Connect

This project attempts to demonstrate the effectiveness of exploiting thin, layered, low-energy, deposits at the distal margin of a prograding turbidite complex through use of fractured horizontal or high-angle wells. The combination of hydraulic fracturing and horizontal drilling will allow greater pay exposure than conventional vertical wells while maintaining vertical communication between thin interbedded layers and the wellbore. A high-angle well will be drilled in the fan margin portion of a slope-basin clastic reservoir and will be completed with multiple hydraulic fracture treatments. Geologic modeling, reservoir characterization, and fine-grid reservoir simulation will be used to select the well location and orientation. Design parameters for hydraulic fracture treatments will be determined by fracturing an existing test well. Fracture azimuth will be predicted, in part, by passive seismic monitoring from an offset well during fracture stimulation of the test wellbore. An existing vertical well in the Yowlumne Field, Kern Co., California was hydraulically fractured. Microseismic and pressure data collected from this work are being used to predict fracture geometry and azimuth for future treatments in the proposed high-angle well. A detailed reservoir characterization of the field demonstration site is complete. This work include interpretation of a 3-D seismic survey, analysis of all available well logs, description of three whole cores, petrographic analysis of thin sections and incorporation of pressure and production data. A partial-field fine-grid model base on the reservoir characterization has been constructed and initialized. Efforts to history match the model to actual production and pressure data are underway.

Niemeyer, B.L.

1996-04-29

180

The EPA's Study on the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources  

NASA Astrophysics Data System (ADS)

Natural gas plays a key role in our nation's clean energy future. The United States has vast reserves of natural gas that are commercially viable as a result of advances in horizontal drilling and hydraulic fracturing technologies, which enable greater access to gas in rock formations deep underground. These advances have spurred a significant increase in the production of both natural gas and oil across the country. However, as the use of hydraulic fracturing has increased, so have concerns about its potential human health and environmental impacts, especially for drinking water. In response to public concern, the US Congress requested that the US Environmental Protection Agency (EPA) conduct scientific research to examine the relationship between hydraulic fracturing and drinking water resources. In 2011, the EPA began research 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 such impacts. The study is organized around the five stages of the hydraulic fracturing water cycle, from water acquisition through the mixing of chemicals and the injection of fracturing fluid to post-fracturing treatment and/or disposal of wastewater. EPA scientists are using a transdisciplinary research approach involving laboratory studies, computer modeling, toxicity assessments, and case studies to answer research questions associated with each stage of the water cycle. This talk will provide an overview of the EPA's study, including a description of the hydraulic fracturing water cycle and a summary of the ongoing research projects.

Burden, Susan

2013-03-01

181

Analysis of production tests of hydraulically fractured wells in a tight solution gas-drive reservoir  

SciTech Connect

A simulation study has been carried out to investigate how accurate existing techniques are to evaluate tests of non-ideal hydraulically fractured wells in tight solution gas drive reservoirs. In the reservoir under investigation some frac-jobs have been carried out in stages. Wells, deviating up to 45 degrees, can intersect several parallel vertical fractures. In that case a correct analysis of tests is almost impossible. In practice conclusive results can only be obtained if a prefrac test is available or when a postfrac test formation radial flow is evidently reached. Existing superposition methods were tested for constant pressure, constant rate and multirate cases to compare their applicabilities. In case radial flow superposition is applied in the time scale and if linear flow is significant results of multirate cases can show too optimistic kh values. Published pseudopressure techniques to find formation kh values for solution gas drive reservoirs are improved by using average fluid properties instead of those at wellbore conditions. To accurately define fracture and formation characteristics a pseudo time factor was needed to correct for drastic changes in viscosity and total compressibility.

Verbeek, C.M.J.

1982-09-01

182

Preliminary stress measurements in central California using the hydraulic fracturing technique  

USGS Publications Warehouse

Use of the hydraulic fracturing technique for determining in situ stress is reviewed, and stress measurements in wells near the towns of Livermore, San Ardo, and Menlo Park, California are described in detail. In the Livermore well, four measurements at depths between 110 and 155 m indicate that the least principal compressive stress is horizontal and increases from 1.62 to 2.66 MPa. The apparent direction of maximum compression is N 70?? E (??40??). At the San Ardo site the least principal stress is that due to the overburden weight. At depths of 240.2 and 270.7 m the minimum and maximum horizontal stresses are estimated to be 11.4 and 22.5 MPa, and 12.0 (??1.1) and 15.8 (??3.3) MPa, respectively. From an impression of the fracture at 240.2 m, the direction of maximum compression appears to be about N 15?? E. The rock in the Menlo Park well is too highly fractured to yield a reliable measurement of the horizontal stresses. The data indicate, however, that the least principal stress is vertical (due to the overburden weight) to a depth of 250 m. ?? 1977 Birkha??user Verlag.

Zoback, M. D.; Healy, J. H.; Roller, J. C.

1977-01-01

183

Impact of Vertical Hydraulic Conductivity Variations on Flow and Solute Transport in Chalk Groundwater  

Microsoft Academic Search

Borehole measurements provide valuable information about how aquifer properties vary in the vertical dimension. Such vertical hydraulic conductivity variations are typically excluded from regional groundwater flow models, as their implications for prediction of sustainable yields are usually small. However, the prediction of groundwater quality trends and the impacts of land use planning decisions (e.g. impact of agrochemical applications, delineation of

A. H. Parker; L. J. West; N. E. Odling

2008-01-01

184

Inverse modeling of hydraulic tests in fractured crystalline rock based on a transition probability geostatistical approach  

NASA Astrophysics Data System (ADS)

This paper presents numerical simulations of a series of hydraulic interference tests conducted in crystalline bedrock at Olkiluoto (Finland), a potential site for the disposal of the Finnish high-level nuclear waste. The tests are in a block of crystalline bedrock of about 0.03 km3 that contains low-transmissivity fractures. Fracture density, orientation, and fracture transmissivity are estimated from Posiva Flow Log (PFL) measurements in boreholes drilled in the rock block. On the basis of those data, a geostatistical approach relying on a transitional probability and Markov chain models is used to define a conceptual model based on stochastic fractured rock facies. Four facies are defined, from sparsely fractured bedrock to highly fractured bedrock. Using this conceptual model, three-dimensional groundwater flow is then simulated to reproduce interference pumping tests in either open or packed-off boreholes. Hydraulic conductivities of the fracture facies are estimated through automatic calibration using either hydraulic heads or both hydraulic heads and PFL flow rates as targets for calibration. The latter option produces a narrower confidence interval for the calibrated hydraulic conductivities, therefore reducing the associated uncertainty and demonstrating the usefulness of the measured PFL flow rates. Furthermore, the stochastic facies conceptual model is a suitable alternative to discrete fracture network models to simulate fluid flow in fractured geological media.

Blessent, Daniela; Therrien, René; Lemieux, Jean-Michel

2011-12-01

185

Using constant head step tests to determine hydraulic apertures in fractured rock  

NASA Astrophysics Data System (ADS)

The initial step in the analysis of contaminant transport in fractured rock requires the consideration of groundwater velocity. Practical methods for estimating the average linear groundwater velocity ( v¯) in fractured rock require determination of hydraulic apertures which are commonly calculated by applying the cubic law using transmissivity (T) values and the number of hydraulically active fractures in the test interval. High-resolution, constant-head step injection testing of cored boreholes in a 100 m thick fractured dolostone aquifer was conducted using inflatable packers to isolate specific test intervals from the rest of the borehole. The steps in each test interval were gradually increased from very low to much higher injection rates. At smaller injection rates, the flow rate vs. applied pressure graph projects through the origin and indicates Darcian flow; non Darcian flow is evident at higher injection rates. Non-Darcian flow results in significantly lower calculated T values, which translates to smaller hydraulic aperture values. Further error in the calculated hydraulic aperture stems from uncertainty in the number of hydraulically active fractures in each test interval. This estimate can be inferred from borehole image and core logs, however, all of the fractures identified are not necessarily hydraulically active. This study proposes a method based on Reynolds number calculations aimed at improving confidence in the selection of the number of active fractures in each test interval.

Quinn, Patryk M.; Parker, Beth L.; Cherry, John A.

2011-09-01

186

Real-time and post-frac' 3-D analysis of hydraulic fracture treatments in geothermal reservoirs  

SciTech Connect

Economic power production from Hot Dry Rock (HDR) requires the establishment of an efficient circulation system between wellbores in reservoir rock with extremely low matrix permeability. Hydraulic fracturing is employed to establish the necessary circulation system. Hydraulic fracturing has also been performed to increase production from hydrothermal reservoirs by enhancing the communication with the reservoir's natural fracture system. Optimal implementation of these hydraulic fracturing applications, as with any engineering application, requires the use of credible physical models and the reconciliation of the physical models with treatment data gathered in the field. Analysis of the collected data has shown that 2-D models and 'conventional' 3-D models of the hydraulic fracturing process apply very poorly to hydraulic fracturing in geothermal reservoirs. Engineering decisions based on these more 'conventional' fracture modeling techniques lead to serious errors in predicting the performance of hydraulic fracture treatments. These errors can lead to inappropriate fracture treatment design as well as grave errors in well placement for hydrothermal reservoirs or HDR reservoirs. This paper outlines the reasons why conventional modeling approaches fall short, and what types of physical models are needed to credibly estimate created hydraulic fracture geometry. The methodology of analyzing actual measured fracture treatment data and matching the observed net fracturing pressure (in realtime as well as after the treatment) is demonstrated at two separate field sites. Results from an extensive Acoustic Emission (AE) fracture diagnostic survey are also presented for the first case study aS an independent measure of the actual created hydraulic fracture geometry.

Wright, C.A.; Tanigawa, J.J.; Hyodo, Masami; Takasugi, Shinji

1994-01-20

187

Hydraulic Fracturing and the National Environmental Policy Act (NEPA): Selected Issues. April 25, 2012.  

National Technical Information Service (NTIS)

Hydraulic fracturing is a technique used to recover oil and natural gas from underground low permeability rock formations. This process involves pumping fluids under high pressure into the formations to crack them, releasing oil and gas into the well. The...

B. J. Murrill

2012-01-01

188

Modeling of fault reactivation and induced seismicity during hydraulic fracturing of shale-gas reservoirs  

EPA Science Inventory

We have conducted numerical simulation studies to assess the potential for injection-induced fault reactivation and notable seismic events associated with shale-gas hydraulic fracturing operations. The modeling is generally tuned toward conditions usually encountered in the Marce...

189

77 FR 27691 - Oil and Gas; Well Stimulation, Including Hydraulic Fracturing, on Federal and Indian Lands  

Federal Register 2010, 2011, 2012, 2013

...from wells. Hydraulic fracturing techniques are particularly effective in enhancing oil and gas production from ``shale'' gas or oil formations. Until quite recently, shale formations rarely produced oil or gas in commercial quantities...

2012-05-11

190

Evaluation of Impacts to Underground Sources of Drinking Water by Hydraulic Fracturing of Coalbed Methane Reservoirs.  

National Technical Information Service (NTIS)

The U.S. Environmental Protection Agency (EPA, or the Agency) conducted a study that assesses the potential for contamination of underground sources of drinking water (USDWs) from the injection of hydraulic fracturing fluids into coalbed methane (CBM) wel...

2004-01-01

191

Plan to Study the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources.  

National Technical Information Service (NTIS)

Natural gas plays a key role in our nation's clean energy future. Recent advances in drilling technologies including horizontal drilling and hydraulic fracturing have made vast reserves of natural gas economically recoverable in the US. Responsible develo...

2011-01-01

192

Experimental and Theoretical Study of Hydraulic Fracturing in Impermeable and Permeable Materials. Final Report.  

National Technical Information Service (NTIS)

Experiments were conducted to study hydraulic fracture propagation in impermeable and permeable materials. The complicating effects of fluid leak-off and proppant transport were separated by conducting experiments on an impermeable material without proppa...

M. B. Rubin

1981-01-01

193

Exact quasi-steady solution of the problem of hydraulic fracturing of a permeable formation  

NASA Astrophysics Data System (ADS)

An exact solution of the problem of hydraulic fracturing in a permeable medium with continuous fluid injection in a partially penetrated formation is constructed using the Perkins-Kern fracture model. The amount of fluid leakage from the fracture is determined using the pressure field of the fluid filtrate defined by the Shchelkachev equation (of the piezoconductivity type). Universal profiles of the fluid pressure in the fracture and the rate of fluid flow from it are obtained. It is shown that at the Perkins-Kern fracture tip, there is a dramatic increase in the leakage from the fracture.

Gordeev, Yu. N.; Babaeva, D. O.; Sandakov, E. B.

2013-11-01

194

Detecting Low-Frequency Seismic Signals From Surface Microseismic Monitoring of Hydraulic Fracturing of a Tight-Sand Gas Reservoir  

NASA Astrophysics Data System (ADS)

For both surface and downhole microseismic monitoring, generally geophones with resonance frequency greater than 4.5 Hz are used. Therefore, useful information below 4.5 Hz may not be detected. In a recent experiment, we installed14 3-component broadband seismic sensors on the surface to monitor the process of hydraulic fracturing of tight sand gas reservoirs. The sensor has a broad frequency range of 30 s to 100 Hz with a very high sensitivity of 2400 m/v/s. The reservoirs are located around 1.5 km depth. There are two fracturing stages along a vertical well, lasting for about 2 hours. We recorded the data continuously during the fracturing process at a sampling rate of 50 Hz. From time-frequency analysis of continuous data, we found some high-energy signals at resonance frequencies between 10 and 20 Hz and a relatively weaker signal at a resonance frequency of ~27 Hz during the hydraulic fracturing. These signals with various resonance frequencies are likely caused by vibrations of high-pressure pipes. In addition to the resonance frequencies, the time-frequency analysis also showed consistent low frequency signals between 3 and 4 Hz at different time. The move-out analysis showed that these signals traveled at shear-wave speeds. We have detected 77 effective low frequency events during the 2-hour hydraulic fracturing process, among which 42 were located by a grid-search location method. The horizontal distribution of the events aligns with the maximum horizontal compressive stress direction. Because of the uncertainty in the velocity model, the low-frequency seismic events are not located in the fracturing depths. Recently, long-period, long-duration seismic events in the frequency band of 10 to 80 Hz were detected during hydraulic fracture stimulation of a shale gas reservoir, which may be caused by slow slip along faults/fractures (Das and Zoback, 2011). In the active volcanic areas, monochromatic events that are related to circulation of hydrothermal fluids are often detected. Our detected low frequency seismic signals have waveforms and frequency contents resembling the monochromatic events detected in volcanic areas, therefore we believe they are also likely caused by movement of fracturing fluids.

Yu, H.; Zhang, H.; Zeng, X.

2013-12-01

195

Texas review of hydraulic fracturing water use and consumption  

NASA Astrophysics Data System (ADS)

Hydraulic fracturing (HF) has a long history in the state of Texas where are located (1) several established plays, such as the Barnett Shale, (2) plays of recent interest, such as the Eagle Ford or the Wolfcamp, and (3) older plays being revisited such as the Wolfberry or the Granite Wash. We compiled current water use for year 2011 (about 82,000 acre-feet) and compared it to an older analysis done for year 2008 (about 36,000 acre-feet). A private database compiling state information and providing water use is complemented by a survey of the industry. Industry survey is the only way to access fresh water consumption estimated to be only a fraction of the total water use because of reuse of flowback water, use of recycled water from treatment plants and produced water, and use of brackish water. We analyzed these different components of the HF budget as well as their source, surface water vs. groundwater, with a focus on impacts on aquifers and groundwater resources.

Nicot, J.; Reedy, R. C.; Costley, R.

2012-12-01

196

Selective oxidation of bromide in wastewater brines from hydraulic fracturing.  

PubMed

Brines generated from oil and natural gas production, including flowback water and produced water from hydraulic fracturing of shale gas, may contain elevated concentrations of bromide (~1 g/L). Bromide is a broad concern due to the potential for forming brominated disinfection byproducts (DBPs) during drinking water treatment. Conventional treatment processes for bromide removal is costly and not specific. Selective bromide removal is technically challenging due to the presence of other ions in the brine, especially chloride as high as 30-200 g/L. This study evaluates the ability of solid graphite electrodes to selectively oxidize bromide to bromine in flowback water and produced water from a shale gas operation in Southwestern PA. The bromine can then be outgassed from the solution and recovered, as a process well understood in the bromine industry. This study revealed that bromide may be selectively and rapidly removed from oil and gas brines (~10 h(-1) m(-2) for produced water and ~60 h(-1) m(-2) for flowback water). The electrolysis occurs with a current efficiency between 60 and 90%, and the estimated energy cost is ~6 kJ/g Br. These data are similar to those for the chlor-alkali process that is commonly used for chlorine gas and sodium hydroxide production. The results demonstrate that bromide may be selectively removed from oil and gas brines to create an opportunity for environmental protection and resource recovery. PMID:23726709

Sun, Mei; Lowry, Gregory V; Gregory, Kelvin B

2013-07-01

197

Rock Springs Site 12 hydraulic/explosive true in situ oil shale fracturing experiment  

SciTech Connect

The experiment plan involved the creation and characterization of three horizontal hydraulic fractures, followed by the insertion and simultaneous detonation of slurry explosive in the two lower fractures. Core analyses, wellbore logging, and airflow and /sup 85/Kr tracer tests were used for site characterization and assessment of the hydraulic and explosive fracturing. Tiltmeters, wellhead pressure and flow gages, and in-formation pressure, flow and crack-opening sensors were used to monitor hydrofracture creation and explosive insertion. Explosive detonation diagnostic data were taken with stress and time-of-arrival gages and surface and in-formation accelerometers. The post-fracturing assessments indicated that: (1) hydrofracture creation and explosive insertion and detonation were accomplished essentially as planned; (2) induced fractures were randomly distributed through the shale with no extensively fractured regions or dislocation of shale; and (3) enhancement of permeability was limited to enlargement of the explosive-filled fractures.

Parrish, R.L.; Boade, R.R.; Stevens, A.L.; Long, A. Jr.; Turner, T.F.

1980-06-01

198

Physical Controls on Potential Upward Migration of Hydraulic Fracturing Fluid and Brine from Tight Oil and Gas Formations  

NASA Astrophysics Data System (ADS)

The widespread use of hydraulic fracturing (HF) has raised concerns about potential upward migration of HF fluid and brine through the rocks that overlay tight oil and gas formations (permeability ? 10-16 m2). The pathways along which potential fluid migration might occur include the primary porosity, induced and natural fractures, and preexisting faults. In this presentation, we evaluate the physical mechanisms that control whether HF fluid and brine can migrate upward along these pathways and, if so, the approximate magnitude of the fluxes and timescales over which such migration might occur. Our analysis focuses first on potential hydraulic communication between tight formations and shallow potable aquifers via induced fractures and preexisting faults. We developed a relationship that predicts maximum fracture height as a function of HF fluid volume and compared these predictions to the vertical extent of microseismicity from over 12,000 HF stimulations across North America. Virtually all microseisms were within the bounds of the theoretical relationship (a simple power law). The microseismic data were also used to estimate the size of shear displacement areas (including along preexisting faults), which were 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 and that direct hydraulic communication between tight formations and shallow potable groundwater via induced fractures and preexisting faults is not a realistic expectation. Apart from these pathways, the only other avenue for fluid migration is through the unmodified overlying rock. Due to the low permeability of targeted formations and surrounding strata, the pressure pulse applied during an HF stimulation is localized to the immediate vicinity of the fracture network and unable to drive large scale vertical flow. Thus, upward flow, if it occurs, would be controlled by the preexisting distribution of vertical permeabilities and head gradients. We show that in cases where there is an upward gradient, permeability is low, upward fluxes are low, and mean travel times are often greater than one million years. Consequently, it does not appear to be physically plausible for HF fluid and brine to migrate upward through overlying rock and affect shallow potable groundwater.

Flewelling, S. A.; Tymchak, M. P.; Sharma, M.

2013-12-01

199

HYDRAULIC LOGGING METHODS—A SUMMARY OF FIELD METHODS USED IN FRACTURED BEDROCK SYSTEMS, GEORGIA  

Microsoft Academic Search

Hydraulic logging methods provide impor- tant information for groundwater investigations being con- ducted in areas underlain by fractured bedrock systems. Geophysical surveying techniques are used to delineate and characterize hydraulically active zones, delineate the extent of contamination and contaminant sources, identify geo- logic features, optimize monitoring well placement, and guide remediation efforts. Borehole-geophysical methods provide information about physical, chemical, and

Carole D. Johnson; John H. Williams; Lester J. Williams

200

Hydraulic conductivity of partially saturated fractured porous media: flow in a cross-section  

Microsoft Academic Search

Standard models for hydraulic functions of partially saturated fractured porous media (FPM) often rely on macroscopic continuum representation and embrace constitutive relationships originally developed for homogeneous porous media to describe hydraulic behavior of dual (or multi) continua FPM. Such approaches lead to inconsistencies due to neglect of underlying physical processes governing liquid retention and flow in the vastly different pore

Dani; Markus Tuller

2003-01-01

201

Fracture detection using a grounded subsurface vertical electric dipole  

SciTech Connect

In this paper we study the scattered magnetic field above the surface of the earth due to a buried sheet-like conductor excited by a grounded and oscillating vertical electric dipole (G.V.E.D.) in the earth. The significance of this technique for the detection of water-filled fractures is that there is no magnetic field in the air, assuming that the displacement current is negligible, so long as the G.V.E.D. source is buried in a layered half-space. If any signal is detected it must be due to the presence of a 2-D or 3-D inhomogeneity, such as a sheet-like conductor. Using a numerical modeling approach, we calculated the strength and anomaly shape of the secondary magnetic field from the sheet to determine a G.V.E.D. is a suitable source detecting a major conductive fracture zone.

Zhou, Q.; Lee, K.H.; Goldstein, N.E.; Morrison, H.F.; Becker, A.

1986-08-01

202

Comparison of Measured and Modelled Hydraulic Conductivities of Fractured Sandstone Cores  

NASA Astrophysics Data System (ADS)

- A new method for characterising the detailed fracture geometry in sandstone cores is presented. This method is based on the impregnation of samples with coloured resin, without significant disturbance of the fractures. The fractures are made clearly visible by the resin, thus allowing the fracture geometry to be examined digitally. In order to model the bulk hydraulic conductivity, the samples are sectioned serially perpendicular to the flow direction. The hydraulic conductivity of individual sections is estimated by summing the contribution of the matrix and each fracture from the digital data. Finally, the hydraulic conductivity of the bulk sample is estimated by a harmonic average in series along the flow path. Results of this geometrical method are compared with actual physical conductivity values measured from fluid experiments carried out prior to sectioning. The predicted conductivity from the fracture geometry parameters (e.g., fracture aperture, fracture width, fracture length and fracture relative roughness all measured using an optical method) is in good agreement with the independent physical measurements, thereby validating the approach.

Baraka-Lokmane, S.; Liedl, R.; Teutsch, G.

203

A comparison between a semi-analytical and a numerical solution of a two-dimensional hydraulic fracture  

Microsoft Academic Search

This paper compares a semi-analytical self-similar solution of the problem of a hydraulically driven fracture with results obtained using the numerical model Loramec. The problem under consideration is a hydraulic fracture propagating in an infinite impermeable elastic medium under plane strain conditions. The fracture is driven by an incompressible Newtonian fluid injected, at a constant rate, from a source located

R. Carbonell; Jean Desroches; Emmanuel Detournay

1999-01-01

204

Water sources and disposal related to hydraulic fracturing in the Barnett Shale: a historical perspective  

NASA Astrophysics Data System (ADS)

During the past few years, hydraulic fracturing (HF) has become a hotly debated topic particularly related to volume of water used and potential for contamination of shallow aquifers. In this communication, we focused on water use in the oldest shale play in the world as an example for an analysis of historical patterns of water use, consumption, and disposal. The Barnett Shale play in Texas provides an ideal case to assess some of the issues related to shale gas production. It was the first shale play to submit to intense slick-water HF (first horizontal wells in 2003, ~15,000 horizontal wells completed to date). An estimated 200, 000 acre-feet (247 million m3) of water has been used so far in the play (included for vertical wells), mostly in the 4-5 counties making up the core area. More than 90% of the water used is consumed and relatively little recycling occurs in the play. Most of the flowback / produced water is disposed of through injection wells. The median Barnett horizontal well produces back ~100% of the amount of water injected for fracturing in the course of the few years following completion, an amount larger than other well-known shale gas plays. The communication will provide detailed material documenting these findings.

Nicot, J.; Scanlon, B. R.

2013-12-01

205

Hydraulic-Fracture Growth In Dipping Anisotropic Strata As Viewed Through The Surface Deformation Field  

Microsoft Academic Search

In 1983 and 1984 Oak Rdige National Laboratory conducted a series of precision ground deformation measurements before, during, and after the generation of several large hydraulic fractures in a dipping member of the Cambrian Conasauga Shale. Each fracture was produced by the injection of approximately 500,000 L of slurry on a single day. Injection depth was 300 m. Leveling surveys

GARY HOLZHAUSEN; C. S. Haase; S. H. Stow; GEORGE GAZONAS

1985-01-01

206

Stress wave propagationin the site 12 hydraulic\\/explosive fracturing experiment  

Microsoft Academic Search

The Site 12 experiment was a heavily instrumented field event performed to examine the hydraulic\\/explosive fracturing concept for preparing an underground oil shale bed for true in situ processing. One of the key phases of this fracturing concept is the blasting operation which involves the insertion and detonation of slurry explosive in a pre-formed system of hydrofractures. To obtain a

R. R. Boade; R. P. Reed

1980-01-01

207

Uplifts and tilts at earth's surface induced by pressure transients from hydraulic fractures  

Microsoft Academic Search

The pressure transient that spreads through the formation during and after a hydraulic fracture treatment pressurizes the formation and induces a certain swelling. This swelling and the accompanying uplift at the earth's surface can be estimated with poroelastic theory. The uplift may produce a significant signal in tiltmeter devices placed at the surface. This paper reports six fracturing treatments in

1990-01-01

208

A new method for determining fluid flow paths during hydraulic fracturing  

SciTech Connect

Although hydraulic fracturing is a popular method for increasing the productivity of oil and gas wells, there is no direct way other than drilling additional boreholes to determine where the injected fluid has gone and thus what direction a fracture has propagated. Information about fluid flow paths is important for designing subsequent fracturing operations for nearby wells. Determining the locations and orientations of permeable fractures is also important in studies of potential toxic waste repositories where it is critical to understand fluid flow paths. We have developed a method for determining the orientations and locations of fractures along which fluid flows during hydraulic fracturing. The method is based on accurate determination of the locations of microseismic events, or microearthquakes, that accompany the hydraulic injection. By applying a pattern recognition technique to the locations of events from one hydraulic fracturing operation we find planes in the data along which we presume that the fluid has traveled. The planes determined using our method intersect the injection borehole and a second, nearby borehole, in regions where other data indicate that fractures are present.

Fehler, M.

1987-01-01

209

On the form and stability of open hydraulic fractures in the earth's crust  

Microsoft Academic Search

Energy extraction from dry geothermal reservoirs can rely on large hydraulic fractures at depth at relatively impermeable rock connected by inflow and outflow wells to the earth's surface; energy would be recovered by circulating a fluid through the fracture and a heat exchanger at the surface. The paper assesses the effects of linear gradients, primarily due to fluid flow, which

David D. Pollard

1976-01-01

210

An experimental investigation of hydraulic behaviour of fractures and joints in granitic rock  

Microsoft Academic Search

A method of measuring mean mechanical aperture of fractures based on gas volume balance is introduced. The effects of shear displacement and normal stress on mechanical and hydraulic behaviour of fractures are also investigated. The results obtained from tests conducted on granite samples from Olympic Dam (Central Australia) are compared with those calculated from existing shear dilation theories. It is

Z. Chen; S. P. Narayan; Z. Yang; S. S. Rahman

2000-01-01

211

Diffraction of seismic waves by cracks with application to hydraulic fracturing  

Microsoft Academic Search

The authors describe a method of modeling seismic waves interacting with single liquid-filled large cracks based on the Kirchhoff approximation and then apply it to field data in an attempt to estimate the size of a hydraulic fracture. They first present the theory of diffraction of seismic waves by fractures using a Green`s function representation and then compute the scattered

Enru Liu; S. Crampin; J. A. Hudson

1997-01-01

212

In-Situ Stresses: The Predominant Influence on Hydraulic Fracture Containment  

Microsoft Academic Search

In-situ experiments, which are accessible by mineback, have been conducted to determine the parameters that control hydraulic fracture containment. These experiments demonstrate that a stress contrast between the pay zone and a bounding layer is the most important factor controlling fracture height. Material property interfaces are shown to have little effect. 19 refs.

Norman Warpinski; Richard Schmidt; David Northrop

1982-01-01

213

Flow Characteristics of Hydraulic Fracture Proppants Subjected to Repeated Production Cycles  

Microsoft Academic Search

When fracture proppants are subjected to cyclic loading, the conductivity of the fracture is reduced. This paper presents laboratory results to quantify the degradation of sand and intermediate-strength proppants (ISP's) as closure stress is loaded cyclically to the proppant. The results imply that, if a deep gas well is opened and then shut in repeatedly, permanent damage to the hydraulic

S. A. Holditch; D. M. Blakeley

1992-01-01

214

Determining the bulk saturated hydraulic conductivity of fractured low-permeable materials with a single well test  

Microsoft Academic Search

A thick sequence of matrix-dominated (composed of predominantly clay and silt-size particles) glacial diamicton covers extensive areas of the Midwest. Although generally characterized by a low hydraulic conductivity, the diamicton is often fractured. Hydraulic conductivity measurements on small samples, with a single piezometer or laboratory permeameter, underestimate the large scale or bulk hydraulic conductivity. Accurate measurements of hydraulic conductivity are

S. P. Esling; T. A. McDonald; N. Rorick

1992-01-01

215

Fluid flow, structural, and fracture mechanics modeling associated with hydraulic stimulation operations  

SciTech Connect

A summary review of hydraulic fracture modeling is given. The equations governing pertinent fluid flow, structural, and fracture mechanics responses are presented along with salient assumptions. The finite element modeling approach is used to discretize the field equations and compute the fracture dimensions, fluid pressure profile, leak-off, and stress intensity factors. In addition, the effects of frac fluid properties, layered strata, in situ stresses, and bi-material interface characteristics are discussed and numerical examples are presented. 50 refs.

Advani, S.H.; Lee, J.K.; Hamid, M.S.; Gurdogan, O.; Khattab, H.

1982-01-01

216

Flow characteristics of hydraulic fracture proppants subjected to repeated production cycles  

SciTech Connect

When fracture proppants are subjected to cyclic loading, the conductivity of the fracture is reduced. This paper presents laboratory results to quantify the degradation of sand and intermediate-strength proppants (ISP's) as closure stress is loaded cyclically to the proppant. The results imply that, if a deep gas well is opened and then shut in repeatedly, permanent damage to the hydraulic fracture will occur.

Holditch, S.A.; Blakeley, D.M. (Texas A and M Univ. (US))

1992-02-01

217

Crosswell seismic investigation of hydraulically conductive, fracture bedrock near Mirror Lake, New Hampshire  

USGS Publications Warehouse

Near Mirror Lake, New Hampshire (USA), hydraulically conductive, fractured bedrock was investigated with the crosswell seismic method to determine whether this method could provide any information about hydraulic conductivity between wells. To this end, crosswell seismic data, acoustic logs from boreholes, image logs from boreholes, and single borehole hydraulic tests were analyzed. The analysis showed that, first, the P-wave velocities from the acoustic logs tended to be higher in schist than they were in granite. (Schist and granite were the dominant rock types). Second, the P-wave velocities from the acoustic logs tended to be low near fractures. Third, the hydraulic conductivity was always low (always less than to 10-8 m/s) where no fractures intersected the borehole, but the hydraulic conductivity ranged from low to high (from less than to 10-10 m/s to 10-4 m/s) where one or more fractures intersected the borehole. Fourth, high hydraulic conductivities were slightly more frequent when the P-wave velocity was low (less than 5200 m/s) than when it was high (greater than or equal to 5200 m/s). The interpretation of this statistical relation was that the fractures tended to increase the hydraulic conductivity and to lower the P-wave velocity. This statistical relation was applied to a velocity tomogram to create a map showing the probability of high hydraulic conductivity; the map was consistent with results from independent hydraulic tests. ?? 2002 Elsevier Science B.V. All rights reserved.

Ellefsen, K. J.; Hsieh, P. A.; Shapiro, A. M.

2002-01-01

218

Numerical simulation of surface and downhole deformation induced by hydraulic fracturing  

NASA Astrophysics Data System (ADS)

Tiltmeter mapping technology infers hydraulic fracture geometry by measuring fracture-induced rock deformation, which recorded by highly sensitive tiltmeters placed at the surface and in nearby observation wells. By referencing Okada's linear elastic theory and Green's function method, we simulate and analyze the surface and downhole deformation caused by hydraulic fracturing using the homogeneous elastic half-space model and layered elastic model. Simulation results suggest that there is not much difference in the surface deformation patterns between the two models, but there is a significant difference in the downhole deformation patterns when hydraulic fracturing penetrates a stratum. In such cases, it is not suitable to assume uniform elastic half-space when calculating the downhole deformation. This work may improve the accuracy and reliability of the inversion results of tiltmeter monitoring data.

He, Yi-Yuan; Zhang, Bao-Ping; Duan, Yu-Ting; Xue, Cheng-Jin; Yan, Xin; He, Chuan; Hu, Tian-Yue

2014-03-01

219

The Origins of the Self-Potential Response During Hydraulic Fracturing  

NASA Astrophysics Data System (ADS)

The self-potential (SP) response during hydraulic fracturing of intact granite specimens was investigated in the laboratory. Excellent correlation of pressure drop and SP suggests that the SP response is created primarily by electrokinetic coupling. For low injection pressures, the variation of SP with pressure drop is linear, revealing a constant coupling coefficient (Cc) of -200 mV/MPa. However for radial pressure gradients > 80 MPa/m, the magnitude of the Cc increases in an exponential trend by up to 80% preceding hydraulic fracturing. This increasing Cc is related to increasing permeability at high pore pressures caused by dilatancy of micro-cracks, and is explained by a decrease in the hydraulic tortuosity. Other variables which may also effect the Cc include: a) decreasing specimen resistivity, b) increasing porosity at high pore pressure, c) increasing zeta potential of fresh microcrack surfaces, d) increased effective viscosity by electroviscous effects, and e) flow separation at high fluid velocity. Additional source mechanisms such as piezoelectricity and co-seismic electrokinetics are considered and are shown not to contribute significantly to the SP response during hydraulic fracturing. At the moment of fracture initiation, injectate rushes into the new fracture area where the zeta potential is likely greater than in the preexisting rock porosity, and an anomalous SP spike is observed that may represent the transient SP response to a changing Cc. Finally, during tensile cracking of wet granite specimens in a point load device with no water flow, a SP transient is created by contact electrification. However, the time constant of this event is much less than that for transients observed during hydraulic fracturing, suggesting that SP created solely from material fracture does not contribute to the SP response during hydraulic fracturing.

Moore, J. R.; Glaser, S. D.

2006-12-01

220

A model for turbulent hydraulic fracture and application to crack propagation at glacier beds  

NASA Astrophysics Data System (ADS)

Glaciological observations of under-flooding suggest that fluid-induced hydraulic fracture of an ice sheet from its bed sometimes occurs quickly, possibly driven by turbulently flowing water in a broad sheet flow. Taking the approximation of a fully turbulent flow into an elastic ice medium with small fracture toughness, we derive an approximate expression for the crack-tip speed, opening displacement and pressure profile. We accomplish this by first showing that a Manning-Strickler channel model for resistance to turbulent flow leads to a mathematical structure somewhat similar to that for resistance to laminar flow of a power law viscous fluid. We then adapt the plane-strain asymptotic crack solution of Desroches et al. (1994) and the power law self-similar solution of Adachi and Detournay (2002) for that case to calculate the desired quantities. The speed of crack growth is shown to scale as the overpressure (in excess of ice overburden) to the power 7/6, inversely as ice elastic modulus to the power 2/3, and as the ratio of crack length to wall roughness scale to the power 1/6. We tentatively apply our model by choosing parameter values thought appropriate for a basal crack driven by the rapid drainage of a surface meltwater lake near the margin of the Greenland Ice Sheet. Making various approximations perhaps relevant to this setting, we estimate fluid inflow rate to the basal fracture and vertical and horizontal surface displacements and find order-of-magnitude agreement with observations by Das et al. (2008) associated with lake drainage. Finally, we discuss how these preliminary estimates could be improved.

Tsai, Victor C.; Rice, James R.

2010-09-01

221

Acoustic emission in a fluid saturated heterogeneous porous layer with application to hydraulic fracture  

SciTech Connect

A theoretical model for acoustic emission in a vertically heterogeneous porous layer bounded by semi-infinite solid regions is developed using linearized equations of motion for a fluid/solid mixture and a reflectivity method. Green's functions are derived for both point loads and moments. Numerically integrated propagators represent solutions for intermediate heterogeneous layers in the porous region. These are substituted into a global matrix for solution by Gaussian elimination and back-substitution. Fluid partial stress and seismic responses to dislocations associated with fracturing of a layer of rock with a hydraulically conductive fracture network are computed with the model. A constitutive model is developed for representing the fractured rock layer as a porous material, using commonly accepted relationships for moduli. Derivations of density, tortuosity, and sinuosity are provided. The main results of the model application are the prediction of a substantial fluid partial stress response related to a second mode wave for the porous material. The response is observable for relatively large distances, on the order of several tens of meters. The visco-dynamic transition frequency associated with parabolic versus planar fluid velocity distributions across micro-crack apertures is in the low audio or seismic range, in contrast to materials with small pore size, such as porous rocks, for which the transition frequency is ultrasonic. Seismic responses are predicted for receiver locations both in the layer and in the outlying solid regions. In the porous region, the seismic response includes both shear and dilatational wave arrivals and a second-mode arrival. The second-mode arrival is not observable outside of the layer because of its low velocity relative to the dilatational and shear wave propagation velocities of the solid region.

Nelson, J.T. (California Univ., Berkeley, CA (USA). Dept. of Mechanical Engineering Lawrence Berkeley Lab., CA (USA))

1988-11-01

222

Simulation of the hydraulic fracture process in two dimensions using a discrete element method.  

PubMed

We introduce a discrete element simulation for the hydraulic fracture process in a petroleum well which takes into account the elastic behavior of the rock and the Mohr-Coulomb fracture criterium. The rock is modeled as an array of Voronoi polygons joined by elastic beams, which are submitted to tectonical stresses and the hydrostatic pressure of the fracturing fluid. The fluid pressure is treated like that of a hydraulic column. The simulation reproduces well the time and dimensions of real fracture processes. We also include an analysis of the fracturing fluid loss due to the permeability of the rock which is useful in an efficiency analysis of the treatment. The model is a first step for future applications in the petroleum industry. PMID:17677327

Torres, Sergio Andres Galindo; Castaño, Jose Daniel Muñoz

2007-06-01

223

Characterization of hydraulic fractures and reservoir properties of shale using natural tracers  

NASA Astrophysics Data System (ADS)

Hydraulic fracturing plays a major role in the economic production of hydrocarbon from shale. Current fracture characterization techniques are limited in diagnosing the transport properties of the fractures on the near wellbore scale to that of the entire stimulated reservoir volume. Microseismic reveals information on fracture geometries, but not transport properties. Production analysis (e.g., rate transient analysis using produced fluids) estimates fracture and reservoir flow characteristics, but often relies on simplified models in terms of fracture geometries and fluid storage and transport. We present the approach and potential benefits of incorporating natural tracers with production data analysis for fracture and reservoir characterization. Hydraulic fracturing releases omnipresent natural tracers that accumulate in low permeability rocks over geologic time (e.g., radiogenic 4He and 40Ar). Key reservoir characteristics govern the tracer release, which include: the number, connectivity, and geometry of fractures; the distribution of fracture-surface-area to matrix-block-volume; and the nature of hydrocarbon phases within the reservoir (e.g., methane dissolved in groundwater or present as a separate gas phase). We explore natural tracer systematics using numerical techniques under relevant shale-reservoir conditions. We evaluate the impact on natural tracer transport due to a variety of conceptual models of reservoir-transport properties and boundary conditions. Favorable attributes for analysis of natural tracers include the following: tracer concentrations start with a well-defined initial condition (i.e., equilibrium between matrix and any natural fractures); there is a large suite of tracers that cover a range of at least 7x in diffusion coefficients; and diffusive mass-transfer out of the matrix into hydraulic fractures will cause elemental and isotopic fractionation. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Heath, J. E.; Gardner, P.; Kuhlman, K. L.; Malama, B.

2013-12-01

224

Transient hydraulic tomography in a fractured dolostone: Laboratory rock block experiments  

NASA Astrophysics Data System (ADS)

The accurate characterization of fractured geologic medium, imaging of fracture patterns and their connectivity have been a challenge for decades. Recently, hydraulic tomography has been proposed as a new method for imaging the hydraulic conductivity (K) and specific storage (Ss) distributions of fractured geologic media. While encouraging results have been obtained in the field, the method has not been rigorously assessed in a controlled laboratory setting. In this study, we assess the performance of transient hydraulic tomography (THT) in a fractured dolomitic rock block. The block is characterized through flow-through tests and multiple pumping tests. The pumping test data were then analyzed with the THT code of Zhu and Yeh (2005) to image the fracture patterns and their connectivity through the delineation of K and Ss distributions (or tomograms). Results show that the THT analysis of pumping tests yields high-K and low-Ss zones that capture the fracture pattern and their connectivity quite well and those patterns become more vivid as additional pumping test data are added to the inverse model. The performance of the estimated K and Ss tomograms are then assessed by: (1) comparing the tomograms obtained from synthetic to real data; (2) comparing the tomograms from two different pumping configurations; (3) comparing the estimated geometric mean of the hydraulic conductivity (KG) from the K tomogram to the effective hydraulic conductivity (Keff) estimated from the flow-through tests; and (4) predicting five independent pumping tests not used in the construction of the K and Ss tomograms. The performance assessment of the K and Ss tomograms reveals that THT is able to image high-K and low-Ss zones that correspond to fracture locations in the fractured rock block and that the tomograms can be used to predict drawdowns from pumping tests not used in the construction of the tomograms with reasonable fidelity.

Sharmeen, Rubaiat; Illman, Walter A.; Berg, Steven J.; Yeh, Tian-Chyi J.; Park, Young-Jin; Sudicky, Edward A.; Ando, Ken

2012-10-01

225

Fracture prediction in hydraulic bulging of AISI 304 austenitic steel sheets based on a modified ductile fracture criterion  

NASA Astrophysics Data System (ADS)

The demand for weight reduction in modern vehicle construction has resulted in an increase in the application of hydroforming processes for the manufacture of automotive lightweight components. This trend led to the research of evaluation on formability of the sheet or tube hydroforming to be noted, particularly the prediction of fracture. In this study, a new proposed approach based on damage theory for fracture prediction considering the deformation history was introduced. And the modified ductile fracture criterion was applied to predict the failure for hydraulic bulging of AISI 304 austenitic steel sheets. The material parameters in terms of the function of strain rate in the failure criterion were determined from the equivalent fracture strains corresponding tensile tests under different stress conditions. Then, in the finite element simulation the effect of strain rates and their distribution as well during practical sheet metal forming process was considered. The hydraulic bulging tests were carried out to identify the fracture behavior predicted from FE analysis. A comparison between the prediction and experimental results showed that the proposed approach with a modified ductile fracture criteria can give better fracture predictions than traditional ways.

Xu, Y.; Song, H. W.; Zhang, S. H.; Cheng, M.

2011-08-01

226

Hydraulic anisotropy characterization of pneumatic-fractured sediments using azimuthal self potential gradient.  

PubMed

The pneumatic fracturing technique is used to enhance the permeability and porosity of tight unconsolidated soils (e.g. clays), thereby improving the effectiveness of remediation treatments. Azimuthal self potential gradient (ASPG) surveys were performed on a compacted, unconsolidated clay block in order to evaluate their potential to delineate contaminant migration pathways in a mechanically-induced fracture network. Azimuthal resistivity (ARS) measurements were also made for comparative purposes. Following similar procedures to those used in the field, compressed kaolinite sediments were pneumatically fractured and the resulting fracture geometry characterized from strike analysis of visible fractures combined with strike data from optical borehole televiewer (BHTV) imaging. We subsequently injected a simulated treatment (electrolyte/dye) into the fractures. Both ASPG and ARS data exhibit anisotropic geoelectric signatures resulting from the fracturing. Self potentials observed during injection of electrolyte are consistent with electrokinetic theory and previous laboratory results on a fracture block model. Visual (polar plot) analysis and linear regression of cross plots show ASPG lobes are correlated with azimuths of high fracture strike density, evidence that the ASPG anisotropy is a proxy measure of hydraulic anisotropy created by the pneumatic fracturing. However, ARS data are uncorrelated with fracture strike maxima and resistivity anisotropy is probably dominated by enhanced surface conduction along azimuths of weak 'starter paths' formed from pulverization of the clay and increases in interfacial surface area. We find the magnitude of electrokinetic SP scales with the applied N2 gas pressure gradient (DeltaPN2) for any particular hydraulically-active fracture set and that the positive lobe of the ASPG anomaly indicates the flow direction within the fracture network. These findings demonstrate the use of ASPG in characterizing the effectiveness of (1) pneumatic fracturing and (2) defining likely flow directions of remedial treatments in unconsolidated sediments and rock. PMID:19070400

Wishart, DeBonne N; Slater, Lee D; Schnell, Deborah L; Herman, Gregory C

2009-01-26

227

Hydraulic anisotropy characterization of pneumatic-fractured sediments using azimuthal self potential gradient  

USGS Publications Warehouse

The pneumatic fracturing technique is used to enhance the permeability and porosity of tight unconsolidated soils (e.g. clays), thereby improving the effectiveness of remediation treatments. Azimuthal self potential gradient (ASPG) surveys were performed on a compacted, unconsolidated clay block in order to evaluate their potential to delineate contaminant migration pathways in a mechanically-induced fracture network. Azimuthal resistivity (ARS) measurements were also made for comparative purposes. Following similar procedures to those used in the field, compressed kaolinite sediments were pneumatically fractured and the resulting fracture geometry characterized from strike analysis of visible fractures combined with strike data from optical borehole televiewer (BHTV) imaging. We subsequently injected a simulated treatment (electrolyte/dye) into the fractures. Both ASPG and ARS data exhibit anisotropic geoelectric signatures resulting from the fracturing. Self potentials observed during injection of electrolyte are consistent with electrokinetic theory and previous laboratory results on a fracture block model. Visual (polar plot) analysis and linear regression of cross plots show ASPG lobes are correlated with azimuths of high fracture strike density, evidence that the ASPG anisotropy is a proxy measure of hydraulic anisotropy created by the pneumatic fracturing. However, ARS data are uncorrelated with fracture strike maxima and resistivity anisotropy is probably dominated by enhanced surface conduction along azimuths of weak 'starter paths' formed from pulverization of the clay and increases in interfacial surface area. We find the magnitude of electrokinetic SP scales with the applied N2 gas pressure gradient (??PN2) for any particular hydraulically-active fracture set and that the positive lobe of the ASPG anomaly indicates the flow direction within the fracture network. These findings demonstrate the use of ASPG in characterizing the effectiveness of (1) pneumatic fracturing and (2) defining likely flow directions of remedial treatments in unconsolidated sediments and rock. ?? 2008 Elsevier B.V. All rights reserved.

Wishart, D. N.; Slater, L. D.; Schnell, D. L.; Herman, G. C.

2009-01-01

228

Coordinated studies in support of hydraulic fracturing of coalbed methane. Annual report, June 1990-October 1991  

SciTech Connect

The production of natural gas coal typically requires stimulation in the form of hydraulic fracturing. The results of hydraulic fracturing treatments have ranged from highly successful to less than satisfactory. The approach in the work has been to experimentally evaluate parameters that pertain to coal fluid interactions during hydraulic fracturing and post-frac production and then apply the findings to the selection of fracturing fluids and treatment design. Evaluated parameters include leakoff through cleats, pressure drops through cleated slots with slurries, proppant transport, conductivity, and coal matrix damage due to fracturing fluids. Some conclusions from the work include (1) 100 mesh sand alone can control leakoff through cleats; (2) coal faces alone do not increase pressure drop through fractures with slurries; (3) restrictions approaching 2 proppant diameters are required to see pressure increases; (4) borate fluid pH's of 9.5 are required for transport; (5) mixed proppant conductivities of 100 mesh and 16/30 can be 50% lower than the larger proppant; (6) guar based fracturing fluids can cause up to 90% permeability damage to the coal matrix; (7) HEC containing foams provide the best cleanup in the laboratory (only 10 to 30% damage and have shown excellent results in field trials); and (8) expanded use of COMPAS is recommended to document field results.

Penny, G.S.; Conway, M.W.

1992-04-01

229

Mapping acoustic emissions from hydraulic fracture treatments using coherent array processing: Concept  

SciTech Connect

Hydraulic fracturing is a widely-used well completion technique for enhancing the recovery of gas and oil in low-permeability formations. Hydraulic fracturing consists of pumping fluids into a well under high pressure (1000--5000 psi) to wedge-open and extend a fracture into the producing formation. The fracture acts as a conduit for gas and oil to flow back to the well, significantly increasing communication with larger volumes of the producing formation. A considerable amount of research has been conducted on the use of acoustic (microseismic) emission to delineate fracture growth. The use of transient signals to map the location of discrete sites of emission along fractures has been the focus of most research on methods for delineating fractures. These methods depend upon timing the arrival of compressional (P) or shear (S) waves from discrete fracturing events at one or more clamped geophones in the treatment well or in adjacent monitoring wells. Using a propagation model, the arrival times are used to estimate the distance from each sensor to the fracturing event. Coherent processing methods appear to have sufficient resolution in the 75 to 200 Hz band to delineate the extent of fractures induced by hydraulic fracturing. The medium velocity structure must be known with a 10% accuracy or better and no major discontinuities should be undetected. For best results, the receiving array must be positioned directly opposite the perforations (same depths) at a horizontal range of 200 to 400 feet from the region to be imaged. Sources of acoustic emission may be detectable down to a single-sensor SNR of 0.25 or somewhat less. These conclusions are limited by the assumptions of this study: good coupling to the formation, acoustic propagation, and accurate knowledge of the velocity structure.

Harris, D.B.; Sherwood, R.J.; Jarpe, S.P.; Harben, P.E.

1991-09-01

230

Using flowmeter pulse tests to define hydraulic connections in the subsurface: A fractured shale example  

USGS Publications Warehouse

Cross-borehole flowmeter pulse tests define subsurface connections between discrete fractures using short stress periods to monitor the propagation of the pulse through the flow system. This technique is an improvement over other cross-borehole techniques because measurements can be made in open boreholes without packers or previous identification of water-producing intervals. The method is based on the concept of monitoring the propagation of pulses rather than steady flow through the fracture network. In this method, a hydraulic stress is applied to a borehole connected to a single, permeable fracture, and the distribution of flow induced by that stress monitored in adjacent boreholes. The transient flow responses are compared to type curves computed for several different types of fracture connections. The shape of the transient flow response indicates the type of fracture connection, and the fit of the data to the type curve yields an estimate of its transmissivity and storage coefficient. The flowmeter pulse test technique was applied in fractured shale at a volatile-organic contaminant plume in Watervliet, New York. Flowmeter and other geophysical logs were used to identify permeable fractures in eight boreholes in and near the contaminant plume using single-borehole flow measurements. Flowmeter cross-hole pulse tests were used to identify connections between fractures detected in the boreholes. The results indicated a permeable fracture network connecting many of the individual boreholes, and demonstrated the presence of an ambient upward hydraulic-head gradient throughout the site.

Williams, J. H.; Paillet, F. L.

2002-01-01

231

Hydraulic fracturing in a sedimentary geothermal reservoir: Results and implications  

Microsoft Academic Search

Field experiments in a geothermal research well were conducted to enhance the inflow performance of a clastic sedimentary reservoir section. Due to depths exceeding 4050m, bottom hole temperatures exceeding 140°C, and open hole section (dual zone), technically demanding and somewhat unprecedented conditions had to be managed. The fracturing operations were successful. Fractures were created in two isolated borehole intervals and

B. Legarth; E. Huenges; G. Zimmermann

2005-01-01

232

The importance of in-situ-stress profiles in hydraulic-fracturing applications  

SciTech Connect

In-situ stresses define the local forces acting on lithologic layers in the subsurface. Knowledge of these stresses is important in drilling, wellbore-stability, and, especially, hydraulic-fracturing applications. The measurement of in-situ stress is not straightforward and, therefore, often goes unmeasured. As such, one often assumes values of in-situ stress or estimate in-situ stresses from logging parameters. This article illustrates the importance of in-situ-stress estimates as they relate to hydraulic fracturing and outlines several techniques for estimating in-situ-stress magnitudes.

Hopkins, C.W. [S.A. Holditch and Associates, Inc., Houston, TX (United States). Houston Div.

1997-09-01

233

Assessing and improving steam-assisted gravity drainage: Reservoir heterogeneities, hydraulic fractures, and mobility control foams  

NASA Astrophysics Data System (ADS)

Steam-assisted gravity drainage (SAGD) is a promising approach for recovering heavy and viscous oil resources. In SAGD, two closely-spaced horizontal wells, one above the other, form a steam-injector and producer pair. The reservoir oil is heated by the injected steam and drains to the producer under the effect of gravity. The success of steam-assisted gravity drainage has been demonstrated by both field and laboratory studies mostly based on homogeneous reservoirs and reservoir models. A comprehensive understanding of the effects of reservoir heterogeneities on SAGD performance, however, is required for wider and more successful implementation. This dissertation presents an investigation of the effects of reservoir heterogeneities on SAGD. In addition, two potential methods, hydraulic fracturing and mobility control using foamed steam, are proposed and reported here to enhance SAGD performance, especially for heterogeneous reservoirs. Reservoir simulations of SAGD are conducted with a number of realizations of Athabasca-type oilsand reservoirs that contain randomly-distributed shales geostatistically generated with a stochastic model. We interpret the complex effects of reservoir heterogeneities by identifying two flow regions, the near well region (NWR) and the above well region (AWR). Our simulations indicate that the drainage flow of hot fluids within the NWR, characterized by short flow length, is very sensitive to the presence of shale, whereas the expansion of the steam chamber in the AWR, characterized by long flow length, is affected adversely only when the AWR contains long, continuous shale or a high fraction of shale. Vertical hydraulic fractures are found to improve steam chamber development considerably for reservoirs with poor vertical communication. For the synthetic reservoir under study, an increase in the oil production rate by a factor of two and considerable improvement of energy efficiency with the cumulative oil-steam ratio lifted from 0.2 to 0.3 bbl oil/bbl CWE steam are achieved by adding a vertical fracture. The new concept of foam-assisted SAGD (FA-SAGD) is evaluated numerically with a foam simulator that incorporates the physical mechanisms of foam generation, destruction, and transport. To reduce computational costs, we develop a simplified foam model based on the assumption of local equilibrium of foam generation and coalescence at field scale. Foam displacements in a linear sandstone core are measured using pressure transducers, X-ray Computed Tomography (CT), and a visualization cell to quantify foam bubble texture. The local equilibrium approximation is validated, and good agreement between the experimental results and the predictions of the simplified model is found, with a minor mismatch in the entrance region. For the scenario under study, numerical simulation of the FA-SAGD process shows considerable improvement in the process efficiency over the conventional SAGD process. Live steam production is reduced by a factor of 5 for FA-SAGD compared to conventional SAGD. Consequently, cumulative oil production is increased by about 30% when production versus the volume of steam injected is compared for cases with and without foam.

Chen, Qing

234

Rock deformation models and fluid leak-off in hydraulic fracturing  

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

235

IDENTIFYING HYDRAULICALLY CONDUCTIVE FRACTURES WITH A SLOW-VELOCITY BOREHOLE FLOWMETER.  

USGS Publications Warehouse

The U. S. Geological Survey used a recently developed heat-pulse flowmeter to measure very slow borehole axial water velocities in granitic rock at a site near Lac du Bonnet, Manitoba, Canada. The flowmeter was used with other geophysical measurements to locate and identify hydraulically conducting fractures contributing to the very slow vertical water flow in the two boreholes selected for study. The heat-pulse flowmeter has a flow-measuring range in water of 0. 06-6m/min, and can resolve velocity differences as slow as 0. 01 m/min. This is an order of magnitude slower than the stall speed of spinner flowmeters. The flowmeter is 1. 16 m long and 44 mm in diameter. It was calibrated in columns of 76 and 152 mm diameter, to correspond to the boreholes studied. The heat-pulse flowmeter system is evaluated, and problems peculiar to the measurement of very slow axial water velocities in boreholes are discussed.

Hess, Alfred, E.

1986-01-01

236

Final Plan to Study the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources (02-24-2012)  

EPA Science Inventory

The overall purpose of this study is to elucidate the relationship, if any, between hydraulic fracturing and drinking water resources. More specifically, the study has been designed to assess the potential impacts of hydraulic fracturing on drinking water resources and to identif...

237

Hydraulic-fracture growth in dipping anisotropic strata as viewed through the surface deformation field  

SciTech Connect

In 1983 and 1984 Oak Rdige National Laboratory conducted a series of precision ground deformation measurements before, during, and after the generation of several large hydraulic fractures in a dipping member of the Cambrian Conasauga Shale. Each fracture was produced by the injection of approximately 500,000 L of slurry on a single day. Injection depth was 300 m. Leveling surveys were run several days before and several days after the injections. An array of eight high-precision borehole tiltmeters monitored ground deformations continuously for a period of several weeks. Analysis of the leveling and the tilt measurements revealed surface uplifts as great as 25 mm and tilts of tens of microradians during each injection. Furthermore, partial recovery (subsidence) of the ground took place during the days following an injection, accompanied by shifts in the position of maximum resultant uplift. Interpretation of the tilt measurements is consistent with stable widening and extension of hydraulic fractures with subhorizontal orientations. Comparison of the measured tilt patterns with fracture orientations established from logging of observation wells suggests that shearing parallel to the fracture planes accompanied fracture dilation. This interpretation is supported by measured tilts and ground uplifts that were as much as 100 percent greater than those expected from fracture dilation alone. Models of elastically anisotropic overburden rock do not explain the measured tilt patterns in the absence of shear stresses in the fracture planes. This work represents the first large-scale hydraulic-fracturing experiment in which the possible effects of material anisotropy and fracture-parallel shears have been measured and interpreted.

Holzhausen, G.R.; Haase, C.S.; Stow, S.H.; Gazonas, G.

1985-01-01

238

Hydraulic fracture stimulation treatment of Well Baca 23. Geothermal Reservoir Well-Stimulation Program  

SciTech Connect

Well Stimulation Experiment No. 5 of the Geothermal Reservoir Well Stimulation Program (GRWSP) was performed on March 22, 1981 in Baca 23, located in Union's Redondo Creek Project Area in Sandoval County, New Mexico. The treatment selected was a large hydraulic fracture job designed specifically for, and utilizing frac materials chosen for, the high temperature geothermal environment. The well selection, fracture treatment, experiment evaluation, and summary of the job costs are presented herein.

Not Available

1981-06-01

239

A model for turbulent hydraulic fracture and application to crack propagation at glacier beds  

Microsoft Academic Search

Glaciological observations of under-flooding suggest that fluid-induced hydraulic fracture of an ice sheet from its bed sometimes occurs quickly, possibly driven by turbulently flowing water in a broad sheet flow. Taking the approximation of a fully turbulent flow into an elastic ice medium with small fracture toughness, we derive an approximate expression for the crack-tip speed, opening displacement and pressure

Victor C. Tsai; James R. Rice

2010-01-01

240

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

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

241

The Geometry of a Large-Scale Nitrogen Gas Hydraulic Fracture Formed in Devonian Shale: An Example of Fracture Mapping With Tiltmeters  

Microsoft Academic Search

Production enhancement of gas from wells draining low-permeability formations such as the Devonian shale series of the eastern U.S. commonly is attempted by use of hydraulic fracturing. The problem of designing such fractures to optimize the resulting yield has underlined the need for a more thorough understanding of the fracture process. To this end, several wells penetrating Devonian shale have

Keith Evans; Gary Holzhausen; D. M. Wood

1982-01-01

242

Evaluation of Massive Hydraulic Fracturing Experiments in the Devonian Shale in Lincoln County, West Virginia.  

National Technical Information Service (NTIS)

The report summarizes the final results, conclusions, and recommendations from a review of the Columbia/DOE Massive Hydraulic Fracturing (MHF) Project. The major objective of the study was to apply GRI-developed technology and other modern technology to t...

J. Gatens K. E. Holgate W. J. Lee

1987-01-01

243

Risks to Water Resources from Shale Gas Development and Hydraulic Fracturing in the United States  

NASA Astrophysics Data System (ADS)

The rise of shale gas development through horizontal drilling and high volume hydraulic fracturing has expanded oil and gas exploration in the USA. The rapid rate of shale gas exploration has triggered an intense public debate regarding the potential environmental and human health effects. A review of the updated literature has identified four potential risks for impacts on water resources: (1) stray gas contamination of shallow aquifers near shale gas sites; (2) contamination of surface water and shallow groundwater from spills, leaks, and disposal of inadequately treated wastewater or hydraulic fracturing fluids; (3) accumulation of toxic and radioactive residues in soil or stream sediments near disposal or spill sites; and (4) over-extraction of water resources for drilling and hydraulic fracturing that could induce water shortages and conflicts with other water users, particularly in water-scarce areas. As part of a long-term research on the potential water contamination associated with shale gas development, new geochemical and isotopic techniques have been developed for delineating the origin of gases and contaminants in water resource. In particular, multiple geochemical and isotopic (carbon isotopes in hydrocarbons, noble gas, strontium, boron, radium isotopes) tracers have been utilized to distinguish between naturally occurring dissolved gas and salts in water and contamination directly induced from shale gas drilling and hydraulic fracturing operations.

Vengosh, Avner; Jackson, Robert B.; Warner, Nathaniel; Darrah, Thomas H.; Kondash, Andrew

2014-05-01

244

Regulating hydraulic fracturing in shale gas plays: The case of Texas  

Microsoft Academic Search

The ability to economically produce natural gas from unconventional shale gas reservoirs has been made possible recently through the application of horizontal drilling and hydraulic fracturing. This new technique has radically changed the energy future of the United States. The U.S. has shifted from a waning producer of natural gas to a growing producer. The Energy Information Administration forecasts that

Dianne Rahm

2011-01-01

245

Hydraulic Fracturing And Overcoring Stress Measurements In A Deep Borehole At The Stripa Test Mine, Sweden  

Microsoft Academic Search

Recently, a workable method was developed for performing overcoring measurements in holes hundreds of meters in length. With the need to obtain in situ stress values for nuclear waste disposal simulation experiments at the Stripa Mine in central Sweden, the task of running both the Power Board's Leeman triaxial cell and hydraulic fracturing in the same hole was undertaken. This

Thomas Doe; Kjell Ingevald; Lars Strindell; Bezalel Haimson; Hans Carlsson

1981-01-01

246

Preliminary stress measurements in central California using the hydraulic fracturing technique  

Microsoft Academic Search

Use of the hydraulic fracturing technique for determiningin situ stress is reviewed, and stress measurements in wells near the towns of Livermore, San Ardo, and Menlo Park, California are described in detail. In the Livermore well, four measurements at depths between 110 and 155 m indicate that the least principal compressive stress is horizontal and increases from 1.62 to 2.66

Mark D. Zoback; John H. Healy; John C. Roller

1977-01-01

247

Hydraulic fracturing stress measurements at Yucca Mountain, Nevada, and relationship to the regional stress field  

Microsoft Academic Search

Hydraulic fracturing stress measurements and acoustic borehole televiewer logs were run in holes USW G-1 and USW G-2 at Yucca Mountain as part of the Nevada Nuclear Waste Storage Investigations for the U. S. Department of Energy. Eight tests in the saturated zone, at depths from 646 to 1288 m, yielded values of the least horizontal stress S\\/sub h\\/ that

J. M. Stock; J. H. Healy; S. H. Hickman; M. D. Zoback

1985-01-01

248

Growth rate of a penny-shaped crack in hydraulic fracturing of rocks  

Microsoft Academic Search

The stable growth of a crack created by the hydraulic pressurizing of a penny-shaped crack in a dry rock mass is investigated. The rock mass is infinitely extended, homogeneous, and isotropic. It is verified on the basis of the equations of fluid dynamics that the fracturing fluid cannot penetrate the entire domain of a crack when the crack is moving.

H. Abé; F. T. Mura; L. M. Keer

1976-01-01

249

Active and Passive Seismic Imaging of a Hydraulic Fracture in Diatomite  

Microsoft Academic Search

This paper reports on a comprehensive set of experiments including remote- and treatment-well microseismic monitoring, interwell shear-wave shadowing, and surface tiltmeter arrays, that was used to monitor the growth of a hydraulic fracture in the Belridge diatomite. To obtain accurate measurements, and extensive subsurface network of geophones was cemented spanning the diatomite formation in three closely spaced observation wells around

H. J. Vinegar; P. B. Wills; D. C. DeMartini; J. Shlyapobersky; W. F. J. Deeg; R. G. Adair; J. C. Woerpel; J. E. Fix; G. G. Sorrells

1992-01-01

250

The crack tip solution for hydraulic fracturing in a permeable solid  

Microsoft Academic Search

This paper extends previous work on self-similar analytical solutions for a hydraulically driven fracture propagating in a solid which is in a state of plane strain. In particular, we examine the effect of fluid loss to the formation modelled by the Carter leak-off mechanism. Our main new results are asymptotic solutions for arbitrary rock permeability; it is shown how these

B. Lenoach

1995-01-01

251

Hydraulic fracturing stress measurements near the Hohenzollern-Graben-structure, SW Germany  

Microsoft Academic Search

Summary Hydraulic fracturing stress measurements have been performed in a limestone quarry near the Hohenzollern-Graben, a fault structure in SW Germany. The values of the two horizontal principal stresses were 24 and 15 bars at a depth of 25 m. The magnitude and the direction of the stresses agree with the results obtained by door-stopper measurements at the same location

F. Rummel; R. Jung

1975-01-01

252

State of in Situ Stresses Determined by Hydraulic Fracturing at the Hanford Site.  

National Technical Information Service (NTIS)

This report summarizes the hydraulic fracturing stress determinations conducted during the period 1981 through 1983 by the Basalt Waste Isolation Project. These tests were conducted in boreholes DC-12, RRL-2, RRL-6, and DC-4 to estimate the state of stres...

K. Kim S. A. Dischler J. R. Aggson M. P. Hardy

1986-01-01

253

Identification, characterization, and analysis of hydraulically conductive fractures in granitic basement rocks, Millville, Massachusetts  

USGS Publications Warehouse

A suite of geophysical logs designed to identify and characterize fractures and water production in fractures was run in six bedrock boreholes at a ground-water contamination site near the towns of Millville and Uxbridge in south-central Massachusetts. The geophysical logs used in this study included conventional gamma, single-point resistance, borehole fluid resistivity, caliper, spontaneous potential, and temperature; and the borehole televiewer and heat-pulse flowmeter, which are not usually used to log bedrock water-supply wells. Downward flow under ambient hydraulic-head conditions was measured in three of the boreholes at the site, and the profile of fluid column resistivity inferred from the logs indicated downward flow in all six boreholes. Steady injection tests at about 1.0 gallon per minute were used to identify fractures capable of conducting flow under test conditions. Sixteen of 157 fracturesidentified on the televiewer logs and interpreted as permeable fractures in the data analysis were determined to conduct flow under ambient hydraulic-head conditions or during injection. Hydraulic-head monitoring in the bedrock boreholes indicated a consistent head difference between the upper and lower parts of the boreholes. This naturally occurring hydraulic-head condition may account, in part, for the transport of contaminants from the overlying soil into the bedrock aquifer. The downward flow may also account for the decrease in contaminant concentrations found in some boreholes after routine use of the boreholes as water-supply wells was discontinued.

Paillet, F. L.; Ollila, P. W.

1994-01-01

254

Correlating laboratory observations of fracture mechanical properties to hydraulically-induced microseismicity in geothermal reservoirs.  

SciTech Connect

To date, microseismicity has provided an invaluable tool for delineating the fracture network produced by hydraulic stimulation of geothermal reservoirs. While the locations of microseismic events are of fundamental importance, there is a wealth of information that can be gleaned from the induced seismicity (e.g. fault plane solutions, seismic moment tensors, source characteristics). Closer scrutiny of the spatial and temporal evolution of seismic moment tensors can shed light on systematic characteristics of fractures in the geothermal reservoir. When related to observations from laboratory experiments, these systematic trends can be interpreted in terms of mechanical processes that most likely operate in the fracture network. This paper reports on mechanical properties that can be inferred from observations of microseismicity in geothermal systems. These properties lead to interpretations about fracture initiation, seismicity induced after hydraulic shut-in, spatial evolution of linked fractures, and temporal evolution of fracture strength. The correlations highlight the fact that a combination of temperature, stressing rate, time, and fluid-rock interactions can alter the mechanical and fluid transport properties of fractures in geothermal systems.

Stephen L. Karner, Ph.D

2006-02-01

255

Experimental and theoretical study of hydraulic fracturing in impermeable and permeable materials  

NASA Astrophysics Data System (ADS)

Hydraulic fracture propagation in impermeable and permeable materials was studied. The complicating effects of fluid leak-off and proppant transport were separated by conducting experiments on an impermeable material without proppants, on a permeable material without proppants, and, finally, on the same permeable material with proppants. Borehole pressure, pressure in the fracture, fracture width, and fracture length were measured in both impermeable and permeable experiments. In addition, the extent of fluid penetration into the permeable material was measured in the permeable experiments. It was observed that both the borehole pressure and the pressure gradient in the fracture were considerably larger in the experiments with proppants than in the experiments without proppants. The results of the impermeable and permeable experiments were compared with the corresponding predictions of a solution developed here as well as those of other simple formulas for hydraulic fracture propagation. Although the predictions of the present solution are an improvement over those of the other simple solutions, future research is needed to reduce the discrepancy between theory and experiment. This discrepancy is attributed to the effect of fluid penetration on the fracture mechanics of the permeable medium.

Rubin, M. B.

1981-10-01

256

Experimental and theoretical study of hydraulic fracturing in impermeable and permeable materials. Final report. [Hydrostone  

SciTech Connect

Experiments were conducted to study hydraulic fracture propagation in impermeable and permeable materials. The complicating effects of fluid leak-off and proppant transport were separated by conducting experiments on an impermeable material without proppants, on a permeable material without proppants, and, finally, on the same permeable material with proppants. Borehole pressure, pressure in the fracture, fracture width, and fracture length were measured in both impermeable and permeable experiments. In addition, the extent of fluid penetration into the permeable material was measured in the permeable experiments. It was observed that both the borehole pressure and the pressure gradient in the fracture were considerably larger in the experiments with proppants than in the experiments without proppants. The results of the impermeable and permeable experiments were compared with the corresponding predictions of a solution developed here as well as those of other simple formulas for hydraulic fracture propagation. Although the predictions of the present solution are an improvement over those of the other simple solutions, future research is needed to reduce the discrepancy between theory and experiment. This discrepancy is attributed to the effect of fluid penetration on the fracture mechanics of the permeable medium.

Rubin, M.B.

1981-10-01

257

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

SciTech Connect

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 rock 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.

Moon, H.Y. (Ohio State Univ., Columbus, OH (United States)) [Ohio State Univ., Columbus, OH (United States); Advani, S.H.; Lee, T.S. (Lehigh Univ., Bethlehem, PA (United States)) [Lehigh Univ., Bethlehem, PA (United States)

1992-11-01

258

Scale Dependence of Hydraulic and Structural Parameters In Fractured Rock From Borehole Data (ktb and Hsdp)  

NASA Astrophysics Data System (ADS)

Fundamental understanding of the origin, geometry, extension and scale dependence of fluid pathways in fractured rock is still incomplete. We analysed fracture networks on different scales based on data from fluorescent thinsections and BHTV images from the same depth range to obtain geometrical network parameters and to estimate frac- ture permeability in the vicinity of a mantle plume (Hawaii Scientific Drilling Project, HSDP). A first modelling of a microscopic network from the fluorescent thinsection of a highly olivine phyric basalt gives a clear indication, that the preferential hydraulic pathways on the microscopic scale are in this particular case the micro fractures in the olivine crystal. This is the only plausible explanation of high porosity (16.6 %) due to the observed vesicles and a corresponding low permeability of 10 µD measured on core samples. Modelling hydraulic flow and calculation of permeability leads to simi- lar values of permeability of 12.3 µD assuming a mean fracture aperture of 1 µm and an exponential distribution function of the fractures. Detected structures from BHTV measurements were used to construct a macroscopic stochastic network to simulate the hydraulic flow on a macroscopic scale. We found 337 fractures in the depth section from 783.5 m to 1147.5 m, which result in a linear frequency of 0.927 1/m. Assum- ing horizontal layers and constant fracture apertures of 100 µm for all structures lead to a first estimate of permeability of 77 mD in this depth section. In a recent work, we showed for data from the Continental Deep Drilling Project (KTB) that the frac- ture density versus fracture length follows a power law. The results from the Hawaiian data suggest a similar relationship, despite all differences in the lithological conditions between both sites.

Zimmermann, G.; Burkhardt, H.; Engelhard, L.

259

Characteristics of shut-in curves in hydraulic fracturing stress measurements and determination of in situ minimum compressive stress  

Microsoft Academic Search

Characteristics of pressure decay curves obtained after shut-in hydraulic fracturing stress measurements are studied in detail in an effort to enhance the reliability of the minimum compressive in situ stress determination. The analysis utilizes linear theory of elasticity, fracture mechanics, and global mass balance of fracturing fluid after shut-in. A small amount of crack growth takes place almost instantaneously just

Kazuo Hayashi; Bezalel C. Haimson

1991-01-01

260

Hydraulic characterization for steam enhanced remediation conducted in fractured rock  

Microsoft Academic Search

To explore the viability of Steam Enhanced Remediation (SER) in fractured rock a small-scale steam injection and water\\/vapour extraction pilot study was conducted at the former Loring Air Force Base in northern Maine, USA. A detailed well testing program was undertaken to assist in the design of the injection and extraction well array, and to assess the possibility of off-site

Kyle M. Stephenson; Kent Novakowski; Eva Davis; Gorm Heron

2006-01-01

261

The impact of fractured endodontic file removal on vertical root fracture resistance: three-dimensional finite element analysis.  

PubMed

This study investigated by means of finite element analysis the influence of fractured file removal on root fracture resistance in an endodontically-treated canine. A 4mm fragment of an endodontic file was deliberately fractured in the apical third of an upper canine root and removed by ultrasonic tips. Micro-computed tomography scans were carried out before and after fractured file removal on the same tooth. Two 3D-FE models (before and after file removal) were subjected to 100N loading. Results indicate that the fractured file removal increased von Mises stresses by 55%. Peak stresses were located around the root filling/dentine interface prior to file removal. Following file removal, peak stresses were concentrated at the buccal root surface/bone interface that might initiate vertical root fracture buccolingually. PMID:22852526

Romeed, S A; Dunne, S M

2012-06-01

262

The use of upward hydraulic gradients to arrest downward DNAPL migration in rock fractures  

SciTech Connect

Upward water flow can arrest the downward migration of dense, nonaqueous phase liquids (DNAPLs) through rough-walled fractures provided that a sufficient hydraulic gradient exists. An exact analytical solution to predict the arresting gradient demonstrates that there is little difference between the gradient required to arrest DNAPL migration near the top of the fracture, and the gradient required to arrest migration once DNAPL has extended to the bottom of the fracture. Laboratory experiments involving the migration of tetrachloroethylene (PCE) through two samples of fractured limestone demonstrate the ability of upward water flow to arrest downward DNAPL migration under both wetting and drainage conditions. It is suggested that upward gradients can be generated beneath contaminated regions of the subsurface to provide a hydraulic bottom. A hydraulic bottom at a site would protect against potential downward mobilization of DNAPL in response to the application of aggressive remediation technologies such as surfactant flooding, alcohol flooding, and steam flooding. Upward gradients applied during drilling may also protect against downward mobilization of DNAPL in the formation while drilling through source zones.

Chown, J.C.; Kueper, B.H. [Queen`s Univ., Kingston, Ontario (Canada). Dept. of Civil Engineering; McWhorter, D.B. [Colorado State Univ., Fort Collins, CO (United States). Dept. of Agricultural and Chemical Engineering

1997-05-01

263

Evaluating the performance of hydraulically-fractured shale gas resources in the Appalachian Basin (Invited)  

NASA Astrophysics Data System (ADS)

Evaluating the performance of engineered-natural systems, such as hydraulically-fractured shales associated with natural gas recovery, depends on an understanding of fracture growth within and outside of the target shale formation, as well as the potential for gas and fluids to migrate to other subsurface resources or underground sources of drinking water. The NETL-Regional University Alliance (NETL-RUA) has a broad research portfolio connected with development of hydraulically-fractured shale resources in the Appalachian Basin. Through a combined field, experimental, modeling, and existing data evaluation effort, the following questions are being addressed: 1) Which subsurface features control the extent to which fractures migrate out of the target fracture zone? 2) Can we improve methods for analyzing natural geochemical tracers? What combination of natural and synthetic tracers can best be used to evaluate subsurface fluid and gas migration? 3) How is wellbore integrity affected by existing shallow gas? Can we predict how shallow groundwater hydrology changes due to drilling? 4) Where are existing wellbores and natural fractures located? What field methods can be used to identify the location of existing wells? To date the NETL-RUA team has focused on four key areas: fracture growth, natural isotopic tracers, impacts of well drilling on shallow hydrology, and statistics on wellbores (locations and conditions). We have found that fracture growth is sensitive to overburden geomechanical features, and that the maximum fracture height outside of the Marcellus Shale aligns with prior assessments (e.g., Fisher et al., 2012). The team has also developed methodologies for the rapid preparation of produced-water samples by MC-ICP-MS and ICP-MS; we are using these methodologies to investigate the potential of key geochemical indicators and species of interest (Sr, Ra) as indicators of fluid and gas migration in the Appalachian Basin. Experimental work on subsurface geochemical reactions in the presence of hydraulic fracturing fluid is underway to evaluate potential impacts on produced water chemistry and fracture stability within the shale formation. Additional laboratory experiments, coupled with modeling efforts, are evaluating the effects of well drilling on shallow groundwater hydrology, and the potential for shallow gas to affect cement hydration. At the field scale, the density and distribution of existing wellbores are being assessed through detection with remote magnetometer surveys, and compilation and analysis of existing wellbore databases. Results from these varied research efforts will be used in future predictive assessments of the behavior of engineered shale gas systems.

Huisman, J. A.; Mboh, C.; Rings, J.; Vrugt, J. A.; Vereecken, H.

2011-12-01

264

Evaluating the performance of hydraulically-fractured shale gas resources in the Appalachian Basin (Invited)  

NASA Astrophysics Data System (ADS)

Evaluating the performance of engineered-natural systems, such as hydraulically-fractured shales associated with natural gas recovery, depends on an understanding of fracture growth within and outside of the target shale formation, as well as the potential for gas and fluids to migrate to other subsurface resources or underground sources of drinking water. The NETL-Regional University Alliance (NETL-RUA) has a broad research portfolio connected with development of hydraulically-fractured shale resources in the Appalachian Basin. Through a combined field, experimental, modeling, and existing data evaluation effort, the following questions are being addressed: 1) Which subsurface features control the extent to which fractures migrate out of the target fracture zone? 2) Can we improve methods for analyzing natural geochemical tracers? What combination of natural and synthetic tracers can best be used to evaluate subsurface fluid and gas migration? 3) How is wellbore integrity affected by existing shallow gas? Can we predict how shallow groundwater hydrology changes due to drilling? 4) Where are existing wellbores and natural fractures located? What field methods can be used to identify the location of existing wells? To date the NETL-RUA team has focused on four key areas: fracture growth, natural isotopic tracers, impacts of well drilling on shallow hydrology, and statistics on wellbores (locations and conditions). We have found that fracture growth is sensitive to overburden geomechanical features, and that the maximum fracture height outside of the Marcellus Shale aligns with prior assessments (e.g., Fisher et al., 2012). The team has also developed methodologies for the rapid preparation of produced-water samples by MC-ICP-MS and ICP-MS; we are using these methodologies to investigate the potential of key geochemical indicators and species of interest (Sr, Ra) as indicators of fluid and gas migration in the Appalachian Basin. Experimental work on subsurface geochemical reactions in the presence of hydraulic fracturing fluid is underway to evaluate potential impacts on produced water chemistry and fracture stability within the shale formation. Additional laboratory experiments, coupled with modeling efforts, are evaluating the effects of well drilling on shallow groundwater hydrology, and the potential for shallow gas to affect cement hydration. At the field scale, the density and distribution of existing wellbores are being assessed through detection with remote magnetometer surveys, and compilation and analysis of existing wellbore databases. Results from these varied research efforts will be used in future predictive assessments of the behavior of engineered shale gas systems.

Hakala, A.; Wall, A. J.; Guthrie, G.

2013-12-01

265

Normal-stress dependence of fracture hydraulic properties including two-phase flow properties  

NASA Astrophysics Data System (ADS)

A systematic approach has been developed for determining relationships between normal stress and fracture hydraulic properties, including two-phase flow properties. The development of a relationship between stress and fracture permeability (or fracture aperture and fracture closure) is based on a two-part Hooke's model (TPHM) that captures heterogeneous elastic-deformation processes at a macroscopic scale by conceptualizing the rock mass (or a fracture) into two parts with different mechanical properties. The developed relationship was verified using a number of datasets in the literature for fracture closure versus stress, and satisfactory agreements were obtained. TPHM was previously shown to be able to accurately represent testing data for porous media as well. Based on the consideration that fracture-aperture distributions under different normal stresses can be represented by truncated-Gaussian distributions, closed-form constitutive relationships were developed between capillary pressure, relative permeability and saturation, for deformable horizontal fractures. The usefulness of these relationships was demonstrated by their consistency with a laboratory dataset.

Liu, Hui-Hai; Wei, Ming-Yao; Rutqvist, Jonny

2013-03-01

266

Discrete element modeling of rock deformation, fracture network development and permeability evolution under hydraulic stimulation  

SciTech Connect

Key challenges associated with the EGS reservoir development include the ability to reliably predict hydraulic fracturing and the deformation of natural fractures as well as estimating permeability evolution of the fracture network with time. We have developed a physics-based rock deformation and fracture propagation simulator by coupling a discrete element model (DEM) for fracturing with a network flow model. In DEM model, solid rock is represented by a network of discrete elements (often referred as particles) connected by various types of mechanical bonds such as springs, elastic beams or bonds that have more complex properties (such as stress-dependent elastic constants). Fracturing is represented explicitly as broken bonds (microcracks), which form and coalesce into macroscopic fractures when external and internal load is applied. The natural fractures are represented by a series of connected line segments. Mechanical bonds that intersect with such line segments are removed from the DEM model. A network flow model using conjugate lattice to the DEM network is developed and coupled with the DEM. The fluid pressure gradient exerts forces on individual elements of the DEM network, which therefore deforms the mechanical bonds and breaks them if the deformation reaches a prescribed threshold value. Such deformation/fracturing in turn changes the permeability of the flow network, which again changes the evolution of fluid pressure, intimately coupling the two processes. The intimate coupling between fracturing/deformation of fracture networks and fluid flow makes the meso-scale DEM- network flow simulations necessary in order to accurately evaluate the permeability evolution, as these methods have substantial advantages over conventional continuum mechanical models of elastic rock deformation. The challenges that must be overcome to simulate EGS reservoir stimulation, preliminary results, progress to date and near future research directions and opportunities will be discussed. Methodology for coupling the DEM model with continuum flow and heat transport models will also be discussed.

Shouchun Deng; Robert Podgorney; Hai Huang

2011-02-01

267

Implementation of a Flaw Model to the Fracturing Around a Vertical Shaft  

Microsoft Academic Search

Summary   This paper investigates whether a micromechanical model developed to investigate the relation between the basic failure processes\\u000a at grain-scale and the macroscopic failure pattern can be applied to model the fracturing around large-scale excavations.\\u000a The simulated fracture pattern around a vertical shaft is compared to the fracturing around a shaft at a depth of 3400 m.\\u000a The simulations suggest

B. Van de Steen; A. Vervoort; J. A. L. Napier; R. J. Durrheim

2003-01-01

268

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

SciTech Connect

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.

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

2013-11-19

269

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

PubMed

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. PMID:24088205

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

2013-11-19

270

Numerical assessment of potential impacts of hydraulically fractured Bowland Shale on overlying aquifers  

NASA Astrophysics Data System (ADS)

The success of unconventional gas extracted from shale formations (shale gas) over the last decade has changed the energy landscape in the United States. Shale gas rose from 2% of US gas production in 2000 to 30% in 2011, and is projected to rise to more than 50% by 2030. On the global scale, shale gas could increase total natural gas resources by approximately 32%, with an estimate of the total 7,299 trillion cubic feet (~200 trillion cubic meter) technically recoverable gas worldwide. In the UK, onshore shale gas reserve potential was first estimated to be 150 billion cubic meter by the British Geological Survey (BGS) in 2010. A recent study by BGS revised the previous estimates, with best estimate (50% probability) of total in-place gas resource of 37.6 trillion cubic meters in the Bowland Shale across central Britain. However, there are concerns of potential environmental impacts of hydraulic fracturing of the shale formations, particularly those related to water quality, such as gas migration, contaminant transport through induced and natural fractures. To evaluate the potential impact of hydraulically fractured shale on overlying aquifers, we conduct numerical modelling simulations to assess flow and solute transport from a synthetic Bowland Shale over a period of 1000 years. The synthetic fractured shale was represented by a three-dimensional discrete fracture model that was developed by using the data from a Bowland Shale gas exploration in Lancashire, UK. The assessment was carried out to investigate chloride mass fluxes from the fractured Bowland Shale for a range of upward fracture height growths from 200 to 1850 meters, with three sets of hydraulic conductivities over three orders of magnitude for a multi-layered geological system. Of eighteen scenario analyses, the maximum upward mass flux towards the overlying Sherwood Sandstone aquifer is < 0.02 ton Cl-/ yr when a constant chloride concentration of 100 g Cl-/L is applied for the brine in the fractured shale. With this mass flux rate into the fracture area of ~0.75 km2, it is unlikely to create average chloride concentration over the UK maximum concentration level of 188 mg Cl-/L in groundwater, although upward mass flux via fractures could create pollution 'hot spot' areas exceeding this concentration level. The model study also reveals that the upward mass flux is significantly intercepted by the horizontal mass flux within a high permeable layer between the Bowland Shale and its overlying aquifers, preventing further upward flux towards the overlying aquifers.

Cai, Zuansi; Ofterdinger, Ulrich

2014-05-01

271

Suiatsu hasai ni yoru ganbannai kiretsu no kyodo ni kansuru kenkyu. (Study on fracture behavior within rock made by hydraulic fracturing).  

National Technical Information Service (NTIS)

The paper studies the thickness of crack made in deep underground and the distribution of hydraulic pressure of the fluid flowing in the crack. The study described hydraulic fracturing, water flow in the crack, and dynamic behavior of cracks. The result s...

1997-01-01

272

Fracture tip and critical stress intensity factor of a hydraulically induced fracture  

SciTech Connect

By modeling the rock as an elastoplastic solid obeying the Drucker-Prager failure criterion, the authors have demonstrated that, if the dilatation produced in the plastic zone in front of the fracture tip is inhibited by its surrounding elastic material, the critical stress intensity factor, K[sub Ic], of the material can be higher than those obtained from standard laboratory tests. Using Geertsma's fracture model and including the dry zone in analysis, they also have demonstrated that, unless the fracture is very large, the fracture opening width is affected by the K[sub Ic] of the material.

Tew, C.H.; Liu, G.F. (Univ. of Texas, Austin, TX (United States))

1993-08-01

273

Economic Recovery of Oil Trapped at Fan Margins Using High Angle Wells and Multiple Hydraulic fractures.  

SciTech Connect

The long radius, near-horizontal well has been drilled and completion operations are in progress. Upon initial review of log data, two hydraulic fracture treatments were planned. However, the probability of the lower frac growing into thick sands previously swept by waterflood has called for additional information to be obtained prior to proceeding with hydraulic fracture treatments. Should permeabilities prove to be as favorable as some data indicate, produced water volumes could be excessively high. Prior to pumping the first frac, the well will be perforated and produced from lower pay intervals. These perfs will not impact future frac work. Rate data and pressure transient analysis will dictate the need for the lower frac.

Laue, M.L.

1997-08-31

274

Hydraulics.  

ERIC Educational Resources Information Center

This curriculum guide contains a course in hydraulics to train entry-level workers for automotive mechanics and other fields that utilize hydraulics. The module contains 14 instructional units that cover the following topics: (1) introduction to hydraulics; (2) fundamentals of hydraulics; (3) reservoirs; (4) lines, fittings, and couplers; (5)…

Decker, Robert L.; Kirby, Klane

275

Three-dimensional seismic characterization of a venting site reveals compelling indications of natural hydraulic fracturing  

Microsoft Academic Search

Based on a three-dimensional high-resolution seismic survey off Vancouver Island, Canada, we show that natural hydraulic fracturing is an efficient process to create permeable pathways for focused fluid upflow at submarine venting sites. The pockmark structure examined in this study is located on top of an accreted ridge, where the low-permeability base of the gas hydrate stability field is also

L. Zühlsdorff; V. Spieß

2004-01-01

276

Paving the road for hydraulic fracturing in Paleozoic tight gas reservoirs in Abu Dhabi  

NASA Astrophysics Data System (ADS)

This study contributes to the ongoing efforts of Abu Dhabi National Oil Company (ADNOC) to improve gas production and supply in view of increasing demand and diminishing conventional gas reservoirs in the region. The conditions of most gas reservoirs with potentially economical volumes of gas in Abu Dhabi are tight abrasive deep sand reservoirs at high temperature and pressures. Thus it inevitably tests the limit of both conventional thinking and technology. Accurate prediction of well performance is a major challenge that arises during planning phase. The primary aim is to determine technical feasibility for the implementation of the hydraulic fracture technology in a new area. The ultimate goal is to make economical production curves possible and pave the road to tap new resource of clean hydrocarbon energy source. The formation targeted in this study is characterized by quartzitic sandstone layers and variably colored shale and siltstones with thin layers of anhydrites. It dates back from late Permian to Carboniferous age. It forms rocks at the lower reservoir permeability ranging from 0.2 to less than 1 millidarcy (mD). When fractured, the expected well flow in Abu Dhabi offshore deep gas wells will be close to similar tight gas reservoir in the region. In other words, gas production can be described as transient initially with high rates and rapidly declining towards a pseudo-steady sustainable flow. The study results estimated fracturing gradient range from 0.85 psi/ft to 0.91 psi/ft. In other words, the technology can be implemented successfully to the expected rating without highly weighted brine. Hence, it would be a remarkable step to conduct the first hydraulic fracturing successfully in Abu Dhabi which can pave the road to tapping on a clean energy resource. The models predicted a remarkable conductivity enhancement and an increase of production between 3 to 4 times after fracturing. Moreover, a sustainable rate above 25 MMSCFD between 6 to 10 years is predicted based on a single well model. The forecasts also show that most of the contribution will come from one zone and therefore optimized operational cost can be achieved in future. Once pressures during a diagnostic injection test are known prior to the main hydraulic fracturing treatment, precise calibration will enable accurate design of fracture geometry and containment for full field development. The feasibility of hydraulic fracture is based on available offset well data. The biggest two challenges in Abu-Dhabi at this stage are high depths and high temperatures as well as offshore conditions. For this reason, a higher well pressure envelop and fracturing string installation is envisaged as a necessity in a future well where unknown tectonic stress could result in higher fracturing load. Finally the study recommends drilling a candidate well designed for the implementation of hydraulic fracturing. This well should consider required pressure rating for the fracturing string. Thermal design considerations will also play a role during production due to high temperature. A dipole or multi pole sonic log from the same well is essential to confirm in situ stresses. The planned well will be in the crest at close proximity to studied offset wells to minimize uncertainty where tested wells produced dry gas and to avoid drilling to watered zones down the flank of the reservoir.

Alzarouni, Asim

277

'Fracking' Controversy and Communication: Using National Survey Data to Understand Public Perceptions of Hydraulic Fracturing (Invited)  

NASA Astrophysics Data System (ADS)

The recent push to develop unconventional sources of oil and gas both in the U.S. and abroad via hydraulic fracturing ('fracking') has generated a great deal of controversy. Effectively engaging stakeholders and setting appropriate policies requires insights into current public perceptions of this issue. Using a nationally representative U.S. sample (N=1,061), we examine public perceptions of hydraulic fracturing including: 'top of mind' associations; familiarity with the issue; levels of support/opposition; and predictors of such judgments. Similar to findings on other emerging technologies, our results suggest limited familiarity with the process and its potential impacts and considerable uncertainty about whether to support it. Multiple regression analysis (r2 = 0.49) finds that women, those holding egalitarian worldviews, those who read newspapers more than once a week, those more familiar with hydraulic fracturing, and those who associate the process with environmental impacts are more likely to oppose fracking. In contrast, people more likely to support fracking tend to be older, hold a bachelor's degree or higher, politically conservative, watch TV news more than once a week, and associate the process with positive economic or energy supply outcomes. Based on these findings, we discuss recommendations for future research, risk communication, and energy policy.

Boudet, H. S.

2013-12-01

278

Hydraulic characterization and optimization of total nitrogen removal in an aerated vertical subsurface flow treatment wetland.  

PubMed

In this study, a side-by-side comparison of two pilot-scale vertical subsurface flow constructed wetlands (6.2m(2)×0.85m, qi=95L/m(2)d, ?n=3.5d) handling primary treated domestic sewage was conducted. One system (VA-i) was set to intermittent aeration while the other was aerated continuously (VAp-c). Intermittent aeration was provided to VA-i in an 8h on/4h off pattern. The intermittently aerated wetland, VA-i, was observed to have 70% less nitrate nitrogen mass outflow than the continuously aerated wetland, VAp-c. Intermittent aeration was shown to increase treatment performance for TN while saving 33% of running energy cost for aeration. Parallel tracer experiments in the two wetlands showed hydraulic characteristics similar to one Continuously Stirred Tank Reactor (CSTR). Intermittent aeration did not significantly affect the hydraulic functioning of the system. Hydraulic efficiencies were 78% for VAp-c and 76% for VA-i. PMID:24747396

Boog, Johannes; Nivala, Jaime; Aubron, Thomas; Wallace, Scott; van Afferden, Manfred; Müller, Roland Arno

2014-06-01

279

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

NASA Astrophysics Data System (ADS)

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.

Sarvaramini, E.; Garagash, D.

2011-12-01

280

Identification of parameters influencing the response of gas storage wells to hydraulic fracturing with the aid of a neural network  

SciTech Connect

Performing hydraulic fractures on gas storage wells to improve their deliverability is a common practice in the eastern part of the US. Most fields used for storage in this region are old, and the reservoir characteristic data necessary for most reservoir studies and hydraulic fracture design and evaluation are scarce. This paper introduces a new method by which parameters that influence the response of gas storage wells to hydraulic fracturing may be identified in the absence of sufficient reservoir data. Control and manipulation of these parameters, once identified correctly, could enhance the outcome of frac jobs in gas storage fields. The authors conducted the study on a gas storage field in the Clinton formation of northeastern Ohio. They found that well-performance indicators before a hydraulic fracture play an important role in how good the well will respond to a new frac job. They also identified several other important factors. The identification of controlling parameters serves as a foundation for improved frac job design in the fields where adequate engineering data are not available. Another application of this type of study could be the enhancement of selection criteria among the candidate wells for hydraulic fracturing. To achieve the objective of this study, the authors designed, trained, and applied an artificial neural network. The paper will discuss the results of the incorporation of this new technology in hydraulic fracture design and evaluation.

McVey, D.S. [East Ohio Gas Co., North Canton, OH (United States); Mohaghegh, S.; Aminian, K.; Ameri, S. [West Virginia Univ., Morgantown, WV (United States)

1996-04-01

281

Vertical series hydraulic conductance classes to characterize the unsaturated zone in North Carolina  

USGS Publications Warehouse

This web site contains the Federal Geographic Data Committee-compliant metadata (documentation) for digital data produced for the North Carolina, Department of Environment and Natural Resources, Public Water Supply Section, Source Water Assessment Program. The metadata are for 11 individual Geographic Information System data sets. An overlay and indexing method was used with the data to derive a rating for unsaturated zone and watershed characteristics for use by the State of North Carolina in assessing more than 11,000 public water-supply wells and approximately 245 public surface-water intakes for susceptibility to contamination. For ground-water supplies, the digital data sets used in the assessment included unsaturated zone rating, vertical series hydraulic conductance, land-surface slope, and land cover. For assessment of public surface-water intakes, the data sets included watershed characteristics rating, average annual precipitation, land-surface slope, land cover, and ground-water contribution. Documentation for the land-use data set applies to both the unsaturated zone and watershed characteristics ratings. Documentation for the estimated depth-to-water map used in the calculation of the vertical series hydraulic conductance also is included.

Eimers, Jo Leslie; Terziotti, Silvia; Ferrell, Gloria M.

2001-01-01

282

The Determination of Tectonic Stresses through Analysis of Hydraulic Well Fracturing  

Microsoft Academic Search

The well-fracturing operation is modeled by a band of uniform pressure and two bands of uniform shear stress acting in a cylindrical cavity in an infinite body. Two interesting regions of induced stress are: either end of the pressurized interval where the tan- gential stress is zero (the vertical stress is approximately 95 per cent of the pressure) and the

Ralph O. Kehle

1964-01-01

283

Treatment of a vertical root fracture using dual-curing resin cement: a case report.  

PubMed

Introduction. Vertical root fracture (VRF) is one of the most frustrating complications of root canal treatment. The prognosis of the root with VRF is poor therefore tooth extraction and root amputation are usually the only treatment options. However, bonding of the fracture line with adhesive resin cement during the intentional replantation procedure was recently suggested as an alternative to tooth extraction. Methods. A vertically fractured left maxillary incisor was carefully extracted, fracture line was treated with adhesive resin cement, a retrograde cavity was produced and filled with calcium-enriched mixture (CEM) cement, and tooth was replanted. Results. After 12 months the tooth was asymptomatic. The size of periapical radiolucency was noticeably reduced and there was no clinical sign of ankylosis. Conclusion. Using adhesive resin cement to bond the fracture lines extraorally in roots with VRF and intentional replantation of the reconstructed teeth could be considered as an alternative to tooth extraction, especially for anterior teeth. PMID:23316397

Moradi Majd, Nima; Akhtari, Farshid; Araghi, Solmaz; Homayouni, Hamed

2012-01-01

284

Treatment of a Vertical Root Fracture Using Dual-Curing Resin Cement: A Case Report  

PubMed Central

Introduction. Vertical root fracture (VRF) is one of the most frustrating complications of root canal treatment. The prognosis of the root with VRF is poor therefore tooth extraction and root amputation are usually the only treatment options. However, bonding of the fracture line with adhesive resin cement during the intentional replantation procedure was recently suggested as an alternative to tooth extraction. Methods. A vertically fractured left maxillary incisor was carefully extracted, fracture line was treated with adhesive resin cement, a retrograde cavity was produced and filled with calcium-enriched mixture (CEM) cement, and tooth was replanted. Results. After 12 months the tooth was asymptomatic. The size of periapical radiolucency was noticeably reduced and there was no clinical sign of ankylosis. Conclusion. Using adhesive resin cement to bond the fracture lines extraorally in roots with VRF and intentional replantation of the reconstructed teeth could be considered as an alternative to tooth extraction, especially for anterior teeth.

Moradi Majd, Nima; Akhtari, Farshid; Araghi, Solmaz; Homayouni, Hamed

2012-01-01

285

Investigation of blast-induced fracture in rock mass using reversed vertical seismic profiling  

NASA Astrophysics Data System (ADS)

The rock mass on quarry and pit wall surfaces is usually fractured during production blasting. Quantitative investigations of the fractured zones are needed for stabilization of the rock walls. In this study, the principle of reversed vertical seismic profiling (RVSP) was applied. A set of seismic geophones were arranged on the horizontal bench surface and seismic signals were generated along the vertical rock wall using a free-swinging hammer. The travel times of seismic rays were recorded and the P-wave velocities of the rock mass were analyzed using the Simultaneous Iterative Reconstruction Technique (SIRT). A series of site tests have been carried out on the rock walls at a granite quarry that are characterized by fractures. The fracture depth at various locations on the wall surface is thereby determined. The results indicate that RVSP provides an easy and reliable method to quantitatively evaluate the blasting-induced fractures in the rock mass.

Zou, D. H.; Wu, Y. K.

2001-10-01

286

Impact of microbial activity on the hydraulic properties of fractured chalk.  

PubMed

The impact of microbial activity on fractured chalk transmissivity was investigated on a laboratory scale. Long-term experiments were conducted on six fractured chalk cores (20 cm diameter, 23-44 cm long) containing a single natural fracture embedded in a porous matrix. Biodegradation experiments were conducted under various conditions, including several substrate and oxygen concentrations and flow rates. 2,4,6-Tribromophenol (TBP) was used as a model contaminant (substrate). TBP biodegradation efficiency depended mainly on the amount of oxygen. However, under constant oxygen concentration at the core inlet, elevating the flow rates increased the removal rate of TBP. Transmissivity reduction was clearly related to TBP removal rate, following an initial slow decline and a further sharp decrease with time. The fracture's transmissivity was reduced by as much as 97% relative to the initial value, with no leveling off of the clogging process. For the most extreme cases, reductions of 262 and 157 microm in the equivalent hydraulic apertures were recorded for fractures with initial apertures of 495 and 207 microm, respectively. The reductions in fracture transmissivity occurred primarily because of clogging by bacterial cells and extracellular polymeric substances (EPS) produced by the bacteria. Most of the biodegradation activity was concentrated near the fracture inlet, where the most suitable biodegradation conditions (nutrients and oxygen) prevailed, suggesting that the clogging had occurred in that vicinity. The clogging must have changed the structure of the fracture void, thereby reducing the active volume participating in flow and transport processes. This phenomenon caused accelerated transport of non-reactive tracers and doubled the fracture's dispersivity under constant flow rates. PMID:15683886

Arnon, Shai; Adar, Eilon; Ronen, Zeev; Yakirevich, Alexander; Nativ, Ronit

2005-02-01

287

Using Changes in Fracture Aperture During the Interpretation of Hydraulic Well Tests  

NASA Astrophysics Data System (ADS)

Fractures either dilate or contract in response to head changes during hydraulic well tests. We are measuring those changes in aperture in an effort to increase the information obtained from well tests. The measurements are made with a borehole extensometer temporarily anchored to the walls of an open borehole at two locations. An LVDT measures axial displacement between the anchors and those measurements are recorded along with pressure and temperature during a well test. Current investigations have focused on isolated flat-lying fractures, so axial displacements are assumed to equal changes in aperture. The current design of the extensometer can resolve displacements on the order of several tenths of a micron. Limiting sensitivity of the device to changes in temperature has been an important aspect of ensuring accuracy. Field tests are conducted on fractures identified using caliper and camera logs, and intact borehole intervals are tested for control. Preliminary tests have made use of a borehole cutting flat-lying fractures in biotite gneiss, where the fracture spacing and degree of weathering decreases with depth. Results show that the characteristics of the fractures change with depth: average normal compliance decreases from 0.5 micron/kPa to less than 0.05 micron/kPa, and the effective transmissivity decreases as depth increases from 23 m to 29 m. Normal compliance can be used to determine specific storage, suggesting that the displacement measurements can be used to determine aquifer storativity using a test conducted at a single well. Moreover, fracture compliance of the observed magnitudes implies that the fracture aperture, and thus the transmissivity, may change markedly during well tests where changes in head are significant. More detailed interpretations of the results are being made using a model that considers fluid flow along a deformable fracture embedded in porous material. Inverting the model using transient displacement data provides an approach for deriving information about the in situ dimensions and deformation characteristics of fractures that go beyond what can be determined from hydraulic measurements alone.

Murdoch, L.; Schweisinger, T.; Svenson, E.; Germanovich, L.

2003-12-01

288

Seismic detection of a hydraulic fracture from shear-wave VSP data at Lost Hills Field, California  

Microsoft Academic Search

The authors describe the results of a geophysical experiment in which shear waves (S-waves) were used to detect the presence of a hydraulic fracture in a diatomite reservoir at the Lost Hills Field. They show evidence that transient S-waves recorded in a monitor well represent diffracted energy that disappears as the fracture closes. They also show how, using simple models,

Mark A. Meadows; D. F. Winterstein

1994-01-01

289

Interpretation of seismic data from hydraulic fracturing experiments at the Fenton Hill, New Mexico, hot dry rock geothermal site  

Microsoft Academic Search

An attempt was made to synthesize the results of active seismic experiments carried out by the Los Alamos National Laboratory's Hot Dry Rock Project staff for determining the geometrical and physical properties of the fracture system produced by hydraulic fracturing in a hot, low-permeability rock. Interpretation of data from several reflection, transmission, and attenuation experiments using seismic probes in the

Keiiti Aki; Michael Fehler; R. L. Aamodt; J. N. Albright; R. M. Potter; C. M. Pearson; J. W. Tester

1982-01-01

290

Deciphering transmissivity and hydraulic conductivity of the aquifer by vertical electrical sounding (VES) experiments in Northwest Bangladesh  

NASA Astrophysics Data System (ADS)

The vertical electrical soundings (VESs) are carried out in 24 selective locations of Chapai-Nawabganj area of northwest Bangladesh to determine the transmissivity and hydraulic conductivity of the aquifer. Initially, the transmissivity and hydraulic conductivity are determined from the pumping data of nearby available production wells. Afterwards, the T and K are correlated with geoelectrical resistance and the total resistivity of the aquifer. The present study deciphers the functional analogous relations of the geoelectrical resistance with the transmissivity and the total resistivity with the hydraulic conductivity of the aquifer in northwest Bangladesh. It has been shown that the given equations provide reasonable values of transmissivity and hydraulic conductivity where pumping test information is unavailable. It can be expected that the aquifer properties viz. transmissivity and hydraulic conductivity of geologically similar area can be determined with the help of the obtained equations by conducting VES experiments.

Sattar, Golam Shabbir; Keramat, Mumnunul; Shahid, Shamsuddin

2014-06-01

291

Hydraulics.  

ERIC Educational Resources Information Center

These instructional materials provide an orientation to hydraulics for use at the postsecondary level. The first of 12 sections presents an introduction to hydraulics, including discussion of principles of liquids, definitions, liquid flow, the two types of hydraulic fluids, pressure gauges, and strainers and filters. The second section identifies…

Engelbrecht, Nancy; And Others

292

Using borehole geophysics and cross-borehole flow testing to define hydraulic connections between fracture zones in bedrock aquifers  

USGS Publications Warehouse

Nearly a decade of intensive geophysical logging at fractured rock hydrology research sites indicates that geophysical logs can be used to identify and characterize fractures intersecting boreholes. However, borehole-to-borehole flow tests indicate that only a few of the apparently open fractures found to intersect boreholes conduct flow under test conditions. This paper presents a systematic approach to fracture characterization designed to define the distribution of fractures along boreholes, relate the measured fracture distribution to structure and lithology of the rock mass, and define the nature of fracture flow paths across borehole arrays. Conventional electrical resistivity, gamma, and caliper logs are used to define lithology and large-scale structure. Borehole wall image logs obtained with the borehole televiewer are used to give the depth, orientation, and relative size of fractures in situ. High-resolution flowmeter measurements are used to identify fractures conducting flow in the rock mass adjacent to the boreholes. Changes in the flow field over time are used to characterize the hydraulic properties of fracture intersections between boreholes. Application of this approach to an array of 13 boreholes at the Mirror Lake, New Hamsphire site demonstrates that the transient flow analysis can be used to distinguish between fractures communicating with each other between observation boreholes, and those that are hydraulically isolated from each other in the surrounding rock mass. The Mirror Lake results also demonstrate that the method is sensitive to the effects of boreholes on the hydraulic properties of the fractured-rock aquifer. Experiments conducted before and after the drilling of additional boreholes in the array and before and after installation of packers in existing boreholes demonstrate that the presence of new boreholes or the inflation of packers in existing boreholes has a large effect on the measured hydraulic properties of the rock mass surrounding the borehole array. ?? 1993.

Paillet, F. L.

1993-01-01

293

Measurement and analysis of fractures in vertical, slant, and horizontal core, with examples from the Mesaverde formation  

SciTech Connect

Optimum analysis of natural fracture characteristics and distributions in reservoirs requires conscientious supervision of coring operations, on-site core processing, careful layout and marketing of the core, and detailed measurement of fracture characteristics. Natural fractures provide information on the in situ permeability system, and coring-induced fractures provide data on the in situ stresses. Fracture data derived from vertical core should include fracture height, type and location of fracture terminations with respect to lithologic heterogeneity, fracture planatary and roughness, and distribution with depth. Fractures in core from either a vertical or a deviated well will yield information on dip, dip azimuth, strike, mineralization, and the orientation of fractures relative to the in situ stresses. Only measurements of fractures in core from a deviated/horizontal well will provide estimates of fracture spacing and porosity. These data can be graphed and cross-plotted to yield semi-quantitative fracture characteristics for reservoir models. Data on the orientations of fractures relative to each other in unoriented core can be nearly as useful as the absolute orientations of fractures. A deviated pilot hole is recommended for fracture assessment prior to a drilling horizontal production well because it significantly enhances the chances of fracture intersection, and therefore of fracture characterization. 35 refs., 20 figs., 2 tabs.

Lorenz, J.C. (Sandia National Labs., Albuquerque, NM (United States)); Hill, R.E. (CER Corp., Las Vegas, NV (United States))

1991-01-01

294

The role of toxicological science in meeting the challenges and opportunities of hydraulic fracturing.  

PubMed

We briefly describe how toxicology can inform the discussion and debate of the merits of hydraulic fracturing by providing information on the potential toxicity of the chemical and physical agents associated with this process, individually and in combination. We consider upstream activities related to bringing chemical and physical agents to the site, on-site activities including drilling of wells and containment of agents injected into or produced from the well, and downstream activities including the flow/removal of hydrocarbon products and of produced water from the site. A broad variety of chemical and physical agents are involved. As the industry expands this has raised concern about the potential for toxicological effects on ecosystems, workers, and the general public. Response to these concerns requires a concerted and collaborative toxicological assessment. This assessment should take into account the different geology in areas newly subjected to hydraulic fracturing as well as evolving industrial practices that can alter the chemical and physical agents of toxicological interest. The potential for ecosystem or human exposure to mixtures of these agents presents a particular toxicological and public health challenge. These data are essential for developing a reliable assessment of the potential risks to the environment and to human health of the rapidly increasing use of hydraulic fracturing and deep underground horizontal drilling techniques for tightly bound shale gas and other fossil fuels. Input from toxicologists will be most effective when employed early in the process, before there are unwanted consequences to the environment and human health, or economic losses due to the need to abandon or rework costly initiatives. PMID:24706166

Goldstein, Bernard D; Brooks, Bryan W; Cohen, Steven D; Gates, Alexander E; Honeycutt, Michael E; Morris, John B; Orme-Zavaleta, Jennifer; Penning, Trevor M; Snawder, John

2014-06-01

295

Estimating Hydraulic Conductivities in a Fractured Shale Formation from Pressure Pulse Testing and 3d Modeling  

NASA Astrophysics Data System (ADS)

In the framework of its research on the deep disposal of radioactive waste in shale formations, the French Institute for Radiological Protection and Nuclear Safety (IRSN) has developed a large array of in situ programs concerning the confining properties of shales in their underground research laboratory at Tournemire (SW France). One of its aims is to evaluate the occurrence and processes controlling radionuclide migration through the host rock, from the disposal system to the biosphere. Past research programs carried out at Tournemire covered mechanical, hydro-mechanical and physico-chemical properties of the Tournemire shale as well as water chemistry and long-term behaviour of the host rock. Studies show that fluid circulations in the undisturbed matrix are very slow (hydraulic conductivity of 10-14 to 10-15 m.s-1). However, recent work related to the occurrence of small scale fractures and clay-rich fault gouges indicate that fluid circulations may have been significantly modified in the vicinity of such features. To assess the transport properties associated with such faults, IRSN designed a series of in situ and laboratory experiments to evaluate the contribution of both diffusive and advective process on water and solute flux through a clay-rich fault zone (fault core and damaged zone) and in an undisturbed shale formation. As part of these studies, Modular Mini-Packer System (MMPS) hydraulic testing was conducted in multiple boreholes to characterize hydraulic conductivities within the formation. Pressure data collected during the hydraulic tests were analyzed using the nSIGHTS (n-dimensional Statistical Inverse Graphical Hydraulic Test Simulator) code to estimate hydraulic conductivity and formation pressures of the tested intervals. Preliminary results indicate hydraulic conductivities of 5.10-12 m.s-1 in the fault core and damaged zone and 10-14 m.s-1 in the adjacent undisturbed shale. Furthermore, when compared with neutron porosity data from borehole logging, porosity varies by a factor of 2.5 whilst hydraulic conductivity varies by 2 to 3 orders of magnitude. In addition, a 3D numerical reconstruction of the internal structure of the fault zone inferred from borehole imagery has been built to estimate the permeability tensor variations. First results indicate that hydraulic conductivity values calculated for this structure are 2 to 3 orders of magnitude above those measured in situ. Such high values are due to the imaging method that only takes in to account open fractures of simple geometry (sine waves). Even though improvements are needed to handle more complex geometry, outcomes are promising as the fault damaged zone clearly appears as the highest permeability zone, where stress analysis show that the actual stress state may favor tensile reopening of fractures. Using shale samples cored from the different internal structures of the fault zone, we aim now to characterize the advection and diffusion using laboratory petrophysical tests combined with radial and through-diffusion experiments.

Courbet, C.; DICK, P.; Lefevre, M.; Wittebroodt, C.; Matray, J.; Barnichon, J.

2013-12-01

296

Numerical Simulation of 3D Hydraulic Fracturing Based on an Improved Flow-Stress-Damage Model and a Parallel FEM Technique  

NASA Astrophysics Data System (ADS)

The failure mechanism of hydraulic fractures in heterogeneous geological materials is an important topic in mining and petroleum engineering. A three-dimensional (3D) finite element model that considers the coupled effects of seepage, damage, and the stress field is introduced. This model is based on a previously developed two-dimensional (2D) version of the model (RFPA2D-Rock Failure Process Analysis). The RFPA3D-Parallel model is developed using a parallel finite element method with a message-passing interface library. The constitutive law of this model considers strength and stiffness degradation, stress-dependent permeability for the pre-peak stage, and deformation-dependent permeability for the post-peak stage. Using this model, 3D modelling of progressive failure and associated fluid flow in rock are conducted and used to investigate the hydro-mechanical response of rock samples at laboratory scale. The responses investigated are the axial stress-axial strain together with permeability evolution and fracture patterns at various stages of loading. Then, the hydraulic fracturing process inside a rock specimen is numerically simulated. Three coupled processes are considered: (1) mechanical deformation of the solid medium induced by the fluid pressure acting on the fracture surfaces and the rock skeleton, (2) fluid flow within the fracture, and (3) propagation of the fracture. The numerically simulated results show that the fractures from a vertical wellbore propagate in the maximum principal stress direction without branching, turning, and twisting in the case of a large difference in the magnitude of the far-field stresses. Otherwise, the fracture initiates in a non-preferred direction and plane then turns and twists during propagation to become aligned with the preferred direction and plane. This pattern of fracturing is common when the rock formation contains multiple layers with different material properties. In addition, local heterogeneity of the rock matrix and macro-scale stress fluctuations due to the variability of material properties can cause the branching, turning, and twisting of fractures.

Li, L. C.; Tang, C. A.; Li, G.; Wang, S. Y.; Liang, Z. Z.; Zhang, Y. B.

2012-09-01

297

Measurement of field-saturated hydraulic conductivity on fractured rock outcrops near Altamura (Southern Italy) with an adjustable large ring infiltrometer  

USGS Publications Warehouse

Up to now, field studies set up to measure field-saturated hydraulic conductivity to evaluate contamination risks, have employed small cylinders that may not be representative of the scale of measurements in heterogeneous media. In this study, a large adjustable ring infiltrometer was designed to be installed on-site directly on rock to measure its field-saturated hydraulic conductivity. The proposed device is inexpensive and simple to implement, yet also very versatile, due to its large adjustable diameter that can be fixed on-site. It thus allows an improved representation of the natural system's heterogeneity, while also taking into consideration irregularities in the soil/rock surface. The new apparatus was tested on an outcrop of karstic fractured limestone overlying the deep Murge aquifer in the South of Italy, which has recently been affected by untreated sludge disposal, derived from municipal and industrial wastewater treatment plants. The quasi-steady vertical flow into the unsaturated fractures was investigated by measuring water levels during infiltrometer tests. Simultaneously, subsurface electrical resistivity measurements were used to visualize the infiltration of water in the subsoil, due to unsaturated water flow in the fractures. The proposed experimental apparatus works well on rock outcrops, and allows the repetition of infiltration tests at many locations in order to reduce model uncertainties in heterogeneous media. ?? 2009 Springer-Verlag.

Caputo, M. C.; de Carlo, L.; Masciopinto, C.; Nimmo, J. R.

2010-01-01

298

In-situ stress profiling and prediction of hydraulic fracture azimuth for the west Texas Canyon Sands formation  

SciTech Connect

This paper presents results of hydraulic fracture azimuth and in-situ stress measurements for two wells in the west Texas Canyon Sands formation. The paper gives information for designing infill drilling patterns and improving fracture treatment designs. Eight techniques were applied to measure fracture azimuth; the results from each are discussed. In-situ stress was measured in 12 intervals, and the results were used to calibrate long-spaced digital sonic logs. This paper also discusses the application of calibrated stress to fracture treatment design.

Miller, W.K. II (NSI Technologies Inc., Tulsa, OK (United States)); Peterson, R.E. (CER Corp., Las Vegas, NV (United States)); Harrison, C.W. (AGIP Petroleum Co., Houston, TX (United States)); Stevens, J.E.; Lackey, C.B.

1994-08-01

299

Hydraulics.  

ERIC Educational Resources Information Center

Designed for use in courses where students are expected to become proficient in the area of hydraulics, including diesel engine mechanic programs, this curriculum guide is comprised of fourteen units of instruction. Unit titles include (1) Introduction, (2) Fundamentals of Hydraulics, (3) Reservoirs, (4) Lines, Fittings, and Couplers, (5) Seals,…

Decker, Robert L.

300

Effect of New Obturating Materials on Vertical Root Fracture Resistance of Endodontically Treated Teeth  

Microsoft Academic Search

The aim of this study was to compare vertical forces at fracture of teeth obturated with different materials. Single-rooted teeth were divided into five groups. The first group served as a negative control. The remaining four groups were shaped using ProTaper rotary files (Dentsply Maillefer, Ballaigues, Switzerland). The second group was obturated with gutta percha and a zinc oxide sealer.

Mohammad Hammad; Alison Qualtrough; Nick Silikas

2007-01-01

301

Joint location and source mechanism inversion of microseismic events: benchmarking on seismicity induced by hydraulic fracturing  

NASA Astrophysics Data System (ADS)

Seismic monitoring can greatly benefit from imaging events with a low signal-to-noise ratio (SNR) as the number of the events with a low signal grows exponentially. One way to detect weaker events is improvement of a SNR by migration-type stacking of waveforms from multiple stations. We have developed a new method of location of seismic events that involves stacking of seismic phases and amplitudes along diffraction traveltime curves to suppress noise and detect seismic events with a SNR lower than that on individual receivers. The stacking includes polarity correction based on a simultaneous seismic moment tensor inversion and detection algorithm on the stack function. We applied this method to locate microseismicity induced by hydraulic fracturing. First we calibrated the velocity model by locating perforation shots at known locations. Then we processed 3 d of data from microseismic monitoring of shale stimulation and benchmarked migration-type locations of the largest events that were manually located. The detected and located events induced by hydraulic fracturing in this case study are mostly shear events forming narrow bands along the maximum horizontal stress direction approximately 100 m above the injection intervals. The proposed technique is fully automated and feasible for real-time seismic monitoring.

Anikiev, D.; Valenta, J.; Stan?k, F.; Eisner, L.

2014-07-01

302

Microbial communities in flowback water impoundments from hydraulic fracturing for recovery of shale gas.  

PubMed

Hydraulic fracturing for natural gas extraction from shale produces waste brine known as flowback that is impounded at the surface prior to reuse and/or disposal. During impoundment, microbial activity can alter the fate of metals including radionuclides, give rise to odorous compounds, and result in biocorrosion that complicates water and waste management and increases production costs. Here, we describe the microbial ecology at multiple depths of three flowback impoundments from the Marcellus shale that were managed differently. 16S rRNA gene clone libraries revealed that bacterial communities in the untreated and biocide-amended impoundments were depth dependent, diverse, and most similar to species within the taxa ?-proteobacteria, ?-proteobacteria, ?-proteobacteria, Clostridia, Synergistetes, Thermotogae, Spirochetes, and Bacteroidetes. The bacterial community in the pretreated and aerated impoundment was uniform with depth, less diverse, and most similar to known iodide-oxidizing bacteria in the ?-proteobacteria. Archaea were identified only in the untreated and biocide-amended impoundments and were affiliated to the Methanomicrobia class. This is the first study of microbial communities in flowback water impoundments from hydraulic fracturing. The findings expand our knowledge of microbial diversity of an emergent and unexplored environment and may guide the management of flowback impoundments. PMID:23875618

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

2013-12-01

303

Radium and barium removal through blending hydraulic fracturing fluids with acid mine drainage.  

PubMed

Wastewaters generated during hydraulic fracturing of the Marcellus Shale typically contain high concentrations of salts, naturally occurring radioactive material (NORM), and metals, such as barium, that pose environmental and public health risks upon inadequate treatment and disposal. In addition, fresh water scarcity in dry regions or during periods of drought could limit shale gas development. This paper explores the possibility of using alternative water sources and their impact on NORM levels through blending acid mine drainage (AMD) effluent with recycled hydraulic fracturing flowback fluids (HFFFs). We conducted a series of laboratory experiments in which the chemistry and NORM of different mix proportions of AMD and HFFF were examined after reacting for 48 h. The experimental data combined with geochemical modeling and X-ray diffraction analysis suggest that several ions, including sulfate, iron, barium, strontium, and a large portion of radium (60-100%), precipitated into newly formed solids composed mainly of Sr barite within the first ? 10 h of mixing. The results imply that blending AMD and HFFF could be an effective management practice for both remediation of the high NORM in the Marcellus HFFF wastewater and beneficial utilization of AMD that is currently contaminating waterways in northeastern U.S.A. PMID:24367969

Kondash, Andrew J; Warner, Nathaniel R; Lahav, Ori; Vengosh, Avner

2014-01-21

304

Microbial communities in flowback water impoundments from hydraulic fracturing for recovery of shale gas  

SciTech Connect

Hydraulic fracturing for natural gas extraction from shale produces waste brine known as flowback that is impounded at the surface prior to reuse and/or disposal. During impoundment, microbial activity can alter the fate of metals including radionuclides, give rise to odorous compounds, and result in biocorrosion that complicates water and waste management and increases production costs. Here, we describe the microbial ecology at multiple depths of three flowback impoundments from the Marcellus shale that were managed differently. 16S rRNA gene clone libraries revealed that bacterial communities in the untreated and biocide-amended impoundments were depth dependent, diverse, and most similar to species within the taxa [gamma]-proteobacteria, [alpha]-proteobacteria, ?-proteobacteria, Clostridia, Synergistetes, Thermotogae, Spirochetes, and Bacteroidetes. The bacterial community in the pretreated and aerated impoundment was uniform with depth, less diverse, and most similar to known iodide-oxidizing bacteria in the [alpha]-proteobacteria. Archaea were identified only in the untreated and biocide-amended impoundments and were affiliated to the Methanomicrobia class. This is the first study of microbial communities in flowback water impoundments from hydraulic fracturing. The findings expand our knowledge of microbial diversity of an emergent and unexplored environment and may guide the management of flowback impoundments.

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

2013-12-01

305

Joint location and source mechanism inversion of microseismic events: benchmarking on seismicity induced by hydraulic fracturing  

NASA Astrophysics Data System (ADS)

Seismic monitoring can greatly benefit from imaging events with a low signal-to-noise ratio (SNR) as the number of the events with a low signal grows exponentially. One way to detect weaker events is improvement of a SNR by migration-type stacking of waveforms from multiple stations. We have developed a new method of location of seismic events that involves stacking of seismic phases and amplitudes along diffraction traveltime curves to suppress noise and detect seismic events with a SNR lower than that on individual receivers. The stacking includes polarity correction based on a simultaneous seismic moment tensor inversion and detection algorithm on the stack function. We applied this method to locate microseismicity induced by hydraulic fracturing. First we calibrated the velocity model by locating perforation shots at known locations. Then we processed 3 d of data from microseismic monitoring of shale stimulation and benchmarked migration-type locations of the largest events that were manually located. The detected and located events induced by hydraulic fracturing in this case study are mostly shear events forming narrow bands along the maximum horizontal stress direction approximately 100 m above the injection intervals. The proposed technique is fully automated and feasible for real-time seismic monitoring.

Anikiev, D.; Valenta, J.; Stan?k, F.; Eisner, L.

2014-05-01

306

Investigating the potential use of radium isotopes to trace hydraulic fracturing pollution in streams  

NASA Astrophysics Data System (ADS)

In recent years, hydraulic fracturing or 'fracking' to extract petroleum and natural gas from shale deposits has become much more prevalent. There are currently over 25,000 natural gas wells in the U.S., not all presently active, and permits to date allow projections of more drilling until 2020. Many fracking wells are located in close proximity to streams, and anecdotal evidence suggests that fracking and related activities may lead to surface water pollution. However, little data about the environmental impacts of hydraulic fracturing on streams has been collected. This project investigates the novel use of radium and radon, which are widely used to trace groundwater discharge into coastal waters, as indicators of fracking waste. We measured radium, radon, pH, conductivity, Secchi depth, and dissolved metal concentrations in 20 stream sites near fracking wells in western Pennsylvania and 10 comparable sites where fracking does not take place in western Maryland. We assessed broad differences in water quality between Pennsylvania (fracking) and Maryland (control) sites and investigated correlations between these water quality parameters and intensity of fracking. If radium or radon shows promise as a tracer of fracking pollution, we can also use it to better understand how widespread environmental pollution from fracking is and how this pollution is transported in order to detect spills or inadequate treatment at wastewater facilities.

Hitchens, A.; Knee, K.

2013-12-01

307

Rock specific hydraulic fracturing and matrix acidizing to enhance a geothermal system — Concepts and field results  

NASA Astrophysics Data System (ADS)

Enhanced geothermal systems (EGS) are engineered reservoirs developed to extract economic amounts of heat from low permeability and/or porosity geothermal resources. To enhance the productivity of reservoirs, a site specific concept is necessary to actively make reservoir conditions profitable using specially adjusted stimulation treatments, such as multi fracture concepts and site specific well path design. The results of previously performed stimulation treatments in the geothermal research well GtGrSk4/05 at Groß Schönebeck, Germany are presented. The reservoir is located at a 4100-4300 m depth within the Lower Permian of the NE German Basin with a bottom-hole temperature of 150 °C. The reservoir rock is classified by two lithological units from bottom to top: volcanic rocks (andesitic rocks) and siliciclastics ranging from conglomerates to fine-grained sandstones (fluvial sediments). The stimulation treatments included multiple hydraulic stimulations and an acid treatment. In order to initiate a cross-flow from the sandstone layer, the hydraulic stimulations were performed in different depth sections (two in the sandstone section and one in the underlying volcanic section). In low permeability volcanic rocks, a cyclic hydraulic fracturing treatment was performed over 6 days in conjunction with adding quartz in low concentrations to maintain a sustainable fracture performance. Flow rates of up to 150 l/s were realized, and a total of 13,170 m 3 of water was injected. A hydraulic connection to the sandstone layer was successfully achieved in this way. However, monitoring of the water level in the offsetting well EGrSk3/90, which is 475 m apart at the final depth, showed a very rapid water level increase due to the stimulation treatment. This can be explained by a connected fault zone within the volcanic rocks. Two gel-proppant treatments were performed in the slightly higher permeability sandstones to obtain long-term access to the reservoir rocks. During each treatment, a total of 100 ton of high strength proppants was injected with 500 m 3 of cross-linked gel. The subsequent production test in conjunction with flowmeter logging showed an improvement of productivity by a factor of more than 4. Due to assumed residual drilling mud (constituents: calcite, dolomite, and aragonite) in the near-wellbore vicinity, an acid matrix stimulation was performed thereafter using a coil tubing unit. The following nitrogen lift test demonstrated another increase of productivity by 30-50% to an overall increase by a factor of 5.5-6.2.

Zimmermann, Günter; Blöcher, Guido; Reinicke, Andreas; Brandt, Wulf

2011-04-01

308

Statistical Distribution of Streambed Vertical Hydraulic Conductivity along the Platte River, Nebraska  

NASA Astrophysics Data System (ADS)

Streambed vertical hydraulic conductivity (Kv) plays an important role in understanding the stream-aquifer interactions. While several researchers have discussed the spatial variability of streambed horizontal hydraulic conductivity (Kh) or Kv at one or several close-located sites in a river, they did not develop any statistical distribution analysis of streambed Kv at distant sites along a large river. In this study, the statistical distribution and spatial variation of streambed Kv at 18 test sites in a 300-km reach of the Platte River in Nebraska were presented. In-situ permeameter tests using the falling-head method were carried out to calculate the streambed Kv values. Streambed Kv values in the studied river reach can be placed into three groups decreasing downstream. The streambed Kv values between Schuyler and Woods Landing in the Platte River were lower than those values between Kearney and Central City, a result of contribution of fine-grained sediments from the Loup River downstream to the Platte River. The streambed Kv value at the Ashland site was even smaller, which can be attributed to the additional effects of lower-K sediments from the Elkhorn River deposited in the downstream Platte River. The streambed Kv values were normally distributed nearly at each test site. When the correlated Kv values were taken out from the grid sampling plots, the remaining sub-datasets of streambed Kv values were still in normal distribution at each test site. Furthermore, the combined streambed Kv values of nine test sites in the Platte River from Kearney to Central City was normally distributed, which may be due to the lack of tributaries in-between and thus streambed sediments were well distributed. In contrast, the combined streambed Kv values of seven sites between Schuyler and Woods Landing did not show normal distribution, instead, display somewhat bimodal distribution.

Cheng, C.; Song, J.; Chen, X.; Wang, D.

2009-12-01

309

Energy from True in Situ Processing of Antrim Shale: Preparation of an in Situ Retort Bed by Hydraulic Fracturing.  

National Technical Information Service (NTIS)

Under these specific field conditions, utilization of the natural tendency of the formation to fracture vertically provided the basis for this revised experiment. Observations made during hydrofracturing and permeability testing indicate that a complicate...

C. A. Peil

1980-01-01

310

Assessment of vertical root fracture using cone-beam computed tomography  

PubMed Central

Purpose The aim of this study was to investigate the accuracy of cone-beam computed tomography (CBCT) in the diagnosis of vertical root fractures in a tooth with gutta-percha and prefabricated posts. Materials and Methods This study selected 96 extracted molar and premolar teeth of the mandible. These teeth were divided into six groups as follows: Groups A, B, and C consisted of teeth with vertical root fractures, and groups D, E, and F had teeth without vertical root fractures; groups A and D had teeth with gutta-percha and prefabricated posts; groups B and E had teeth with gutta-percha but without prefabricated posts, and groups C and F had teeth without gutta-percha or prefabricated posts. Then, the CBCT scans were obtained and examined by three oral and maxillofacial radiologists in order to determine the presence of vertical root fractures. The data were analyzed using IBM SPSS 20.0 (IBM Corp., Armonk, NY, USA). Results The kappa coefficient was 0.875±0.049. Groups A and D showed a sensitivity of 81% and a specificity of 100%; groups E and B, a sensitivity of 94% and a specificity of 100%; and groups C and F, a sensitivity of 88% and a specificity of 100%. Conclusion The CBCT scans revealed a high accuracy in the diagnosis of vertical root fractures; the accuracy did not decrease in the presence of gutta-percha. The presence of prefabricated posts also had little effect on the accuracy of the system, which was, of course, not statistically significant.

Moudi, Ehsan; Haghanifar, Sina; Madani, Zahrasadat; Alhavaz, Abdolhamid; Bijani, Ali

2014-01-01

311

Finite Element Modeling of the Hydraulic Stimulation Process for Hot Fractured Geothermal Reservoir Construction  

NASA Astrophysics Data System (ADS)

Since the 1970's, a number of research programmes have worked towards developing Hot Dry Rock technology (HDR) for geothermal energy which has been renamed as Hot Fractured Rock (HFR) in Australia. This problem involves the thermal, fluid and mechanical behaviour of geo-materials and induced seismic events, and potential geological perturbations to the geological heat exchanger facility (i.e. the geothermal reservoir) during the construction, production and shutdown phases. The understanding, simulation and prediction of such a multi-scale highly coupled thermo-hydro-mechanical geo-mechanical system are very important in both theory and practical applications. This paper will focus on our current research activity in finite element modeling of the hydraulic stimulation process which is widely applied to construct the HDR/HFR geothermal reservoir system. A 3-dimensional finite element computational model and code for modeling nonlinear frictional contact behaviours between multiple deformable bodies with the arbitrarily-shaped contact element strategy has been developed, which provides a means to simulate interacting fault systems including crustal boundary conditions and various nonlinearities. It has been successfully applied in a wide range of fields and is extended here to simulate the hydraulic stimulation process. The preliminary simulation results on the hydraulic stimulation process demonstrate the stability and usefulness of the algorithm for analyzing hot fractured geothermal reservoir construction. References Xing, H.L., Mora, P. & Makinouchi, A. (2004) Finite element analysis of fault bend influence on stick-slip instability along an intra-plate fault, Pure Appl. Geophys., 161, 2091-2102. Xing, H.L., & Makinouchi, A. (2002) Three dimensional finite element modelling of thermomechanical frictional contact between finite deformation bodies using R-minimum strategy, Computer Methods in Applied Mechanics and Engineering, 191,4193-4214.

Wyborn, D.; Xing, H.; Mora, P.

2005-12-01

312

Prediction of hydraulic parameters from block joint inversion of magnetic resonance and vertical electric soundings  

NASA Astrophysics Data System (ADS)

For assessing the impact of climate changes on salinity of coastal aquifers, numerical modelling needs to be done. As input, the spatial distribution of the parameters porosity, hydraulic conductivity and salt concentrations is needed. Airborne resistivity data are available that gives hints to fluid conductivity. Magnetic resonance soundings (MRS) can provide free water content directly yielding porosity, which in turn is needed for fluid conductivities and thus TDS concentrations. Furthermore, hydraulic conductivities can be retrieved by empirical relations using porosity and decay times. For having a unique model with all three primary parameters, vertical electrical and magnetic resonance soundings are inverted jointly using a block discretization. The MRS data were preprocessed using noise cancellation, despiking and a new gate integration scheme. Data errors were derived from fitting and include the effect of gating. Since the resistivity model affects the MRS inversion but demands an extensive kernel calculation, resistivity is updated only once. After inversion, a systematic model variation is done in order to retrieve confidence intervals of the primary and secondary parameters. We apply the methodology to several soundings at the North Sea Island Borkum, where the dynamics of the fresh/salt water interface is currently investigated. All soundings exhibit a very good data quality. One sounding close to a research borehole verifies the approach qualitatively. Another sounding was done to calibrate the petrophysical parameters using a pumping test. Finally, it is applied to a sounding in the flooding area. Whereas single MRS and VES data can be explained by a 3-layer and 4-layer model, respectively, a 5-layer model is needed to find a comprehensive model. Even though porosities are fairly constant, we can distinguish lithology and salinity due to the combination of resistivity and decay time. This case shows two fresh/salt water interfaces separated by a silt layer. The computed uncertainties of all three parameters are significantly larger for the silt and the lowest salt-water layer. Finally, we can further derive uncertainties for all derived hydraulic parameters using error propagation.

Günther, T.; Müller-Petke, M.

2012-04-01

313

Evaluating vertical variability analysis (VVA) for estimating the hydraulic conductivity, specific yield, and transmissivity of four simulated geologic configurations  

SciTech Connect

Aquifer systems derived from fluvial, eolian, glacial, or mass movement processes may have considerable vertical and areal variability in saturated thickness, hydraulic conductivity, specific yield, and bed thickness. Frequently, hydraulic data from aquifer tests are not readily available, whereas lithologic and grain-size information from drillers' logs is generally abundant. Therefore, the vertical variability method was devised to evaluate the aquifer properties for individual lithologic units based on drillers' information. These estimates provide vital information about aquifer characterization and are useful for hydraulic analysis and computer modeling. The purpose of this study was to evaluate the VVA for estimating the hydraulic conductivity, specific yield, and transmissivity of four simulated geological configurations. The objectives were to: (1) test the validity of VVA using the method of moments and the 0.5 criterion for relative center of gravity (RCOG); and (2) conduct a sensitivity analysis of material parameters relative to the RCOG. Results show that the 0.5 criterion for RCOG is valid only on a case-by-case basis depending primarily on the geometry of the geologic deposits, and secondarily on the thickness of individual geologic units. Sensitivity analyses reveal that the parameters of hydraulic conductivity and transmissivity are insensitive to changes in RCOG to plus or minus two to three orders of magnitude. Additional results indicate that the variance of RCOG for eolian, glacial, and incomplete two-cycle fluvial deposits is minimal as compared to the those for single and multiple fluvial cycles.

Witt, G.D. (Wright Water Engineers, Inc., Denver, CO (United States)); Kolm, K.E. (Colorado School of Mines, Golden, CO (United States))

1992-01-01

314

Proppant backproduction during hydraulic fracturing -- A new failure mechanism for resin-coated proppants  

SciTech Connect

Backproduction of proppant from hydraulically fractured wells, particularly those completed in the northern European Rotliegend formation, is a major operational problem, necessitating costly and manpower-intensive surface-handling procedures. Further, the development of unmanned platform operations offshore, required in today's economic climate, is impossible as long as this problem remains unsolved. The most cost-effective potential solution to this problem is provided by curable resin-coated proppant (RCP), which consolidates in the fracture. Early field trials with RCP's, however, were not completely effective in stopping the backproduction of proppant. Typically, some 10% of the total volume of RCP placed in the fracture was backproduced. The authors performed a laboratory study to help clarify the effect of curing temperature, water production rate, proppant size, and stress cycling on the integrity of RCP packs. The experiments confirmed the field experience that stress cycling has a dramatic effect on proppant backproduction of commercial RCP packs. The number of applied stress cycles (i.e., the number of times the well is shut in) and the initial RCP pack strength appear to be the dominant factors that govern proppant backproduction. Dedicated experiments are therefore required to evaluate the use of RCP's to eliminate proppant backproduction for a particular field application.

Vreeburg, R.J.; Roodhart, L.P.; Davies, D.R.; Penny, G.S. (STIM-LAB Inc., Duncan, OK (United States))

1994-10-01

315

State of the art hydraulic fracture stimulation treatment for a western tight sand reservoir. [Wyoming  

SciTech Connect

The Pinedale gas field is a tight sand reservoir in Sublette County, Wyoming. A number of wells have been drilled in this field since the 1930's. However, there has been no commercial production because of low initial flow rates and rapid production declines usually associated with low permeability. This field would become attractive if the technological problems impairing development could be overcome. This paper describes a resource evaluation and stimulation research program centered around the drilling of two new wells in the Pinedale Field. The resource evaluation involved a critical review of prior data, geological and geophysical work, laboratory testing of core samples from the new wells, and pre-stimulation and post-stimulation flow testing of the new wells. The stimulation research involved special core testing with candidate stimulation fluids and proppants, field in-situ stress testing for fracture geometry estimates, transient pressure testing for well and fracture evaluation, hydraulic fracture design and implementation, and well deliverability projection. Utilizing the state-of-the-art technology, a total recoverable reserve of 2.8 tcf is now possible from the 90,000 acres of Pinedale Field.

Ahmed, U.; Greenfield, H.; Holland, M.T.; Jones, A.H.; Schatz, J.F.

1982-09-01

316

A Review of Hydraulic Fracture Models and Development of an Improved Pseudo3D Model for Stimulating Tight Oil\\/Gas Sand  

Microsoft Academic Search

Many injection\\/production wells have been hydraulically fractured to enhance injectivity\\/productivity. Various engineering models for fracture geometry have been developed, which define the propagation of a fracture with time and wellbore treatment pressure. These models combine with elasticity, fluid flow, material balance, and propagation criterion\\/in-situ stresses. When this combination describes the fracture dimensions, the fracture-geometry can be of two-dimensional (2D) and

M. M. Rahman; M. K. Rahman

2010-01-01

317

Field determination of the three-dimensional hydraulic conductivity tensor of anisotropic media 2. Methodology and application to fractured rocks.  

USGS Publications Warehouse

The analytical solutions developed in the first paper can be used to interpret the results of cross-hole tests conducted in anisotropic porous or fractured media. Test results from a granitic rock near Oracle in southern Arizona are presented to illustrate how the method works for fractured rocks. At the site, the Oracle granite is shown to respond as a near-uniform, anisotropic medium, the hydraulic conductivity of which is strongly controlled by the orientations of major fracture sets. The cross-hole test results are shown to be consistent with the results of more than 100 single- hole packer tests conducted at the site. -from Authors

Hsieh, P. A.; Neuman, S. P.; Stiles, G. K.; Simpson, E. S.

1985-01-01

318

Balancing the Need for Energy and Clean Water: The Case for Applying Strict Liability in Hydraulic Fracturing Suits  

Microsoft Academic Search

Hydraulic fracturing is a process used to extract natural gas from shale formations. This process has been used commercially since the 1940s, but has recently become prevalent as more shale formations have been discovered, specifically the Marcellus Shale formation in Pennsylvania. Although natural gas is a relatively clean source of domestic energy, there have been numerous allegations of water contamination

Hannah Coman

2012-01-01

319

A method to allow temporal variation of velocity in travel-time tomography using microearthquakes induced during hydraulic fracturing  

Microsoft Academic Search

Hydraulic injections produce fluid-filled fractures that reduce the seismic velocity of the rock compared to intact rock. The travel times of microearthquakes induced by the injections may be used to discern changes in the rock velocities, as well as locating the microearthquakes. Determining the volumes of rock where the velocities have changed provides indirect evidence for the location of the

Michael Fehler; Leigh House; W. Scott Phillips; Robert Potter

1998-01-01

320

Acoustic Emissions as a Tool for Hydraulic Fracture Location: Experience at the Fenton Hill Hot Dry Rock Site  

Microsoft Academic Search

Microearthquakes with magnitudes between -6 and -2 have been observed in three successive massive injections of water at the hot dry rock geothermal energy development project's demonstration site at Fenton Hill, NM. The injections were part of a program to increase the heat transfer area of hydraulic fractures and to decrease the flow-through impedance between wells in the energy extraction

James Albright; Christopher Pearson

1982-01-01

321

Seismic wave motion for a new model of hydraulic fracture with an induced low-velocity zone  

Microsoft Academic Search

Hydraulic fracture treatments induce microsensitivity (i.e., discrete events plus noise) which can be recorded only by seismometers located in or near the treatment well bore. Seismograms recorded in the treatment well bore are composed of interacting phases which to data defay discrete identification and preclude standard inversion techniques to determine source characteristics, propagation path characteristics, or both. To understand the

Kenneth D. Mahrer; Frederick J. Mauk

1987-01-01

322

Parameters and a magnitude moment relationship from small earthquakes observed during hydraulic fracturing experiments in crystalline rocks  

Microsoft Academic Search

Using source parameters estimated from seismic spectra and magnitudes estimated from coda lengths, we demonstrate that the log-linear relationship between moment and magnitude holds for events with magnitudes as low as -6. Using, as a data set, events induced by hydraulic fracturing experiments at the Fenton Hill, New Mexico, Hot Dry Rock (HDR) geothermal site, we find that the relationship

C. Pearson

1982-01-01

323

Development of a Neutron Diffraction Based Experiemental Capability for Investigating Hydraulic Fracturing for EGS-Like Conditions.  

National Technical Information Service (NTIS)

Hydraulic fracturing to enhance formation permeability is an established practice in the Oil & Gas (O&G) industry and is expected to be an enabler for EGS. However, it is rarely employed in conventional geothermal systems and there are significant questio...

J. Carmichael L. Anovitz L. Dessieux P. R. Bingham Y. Polskv

2013-01-01

324

EXPERIMENTAL ANALYSIS OF THE ENVIRONMENTAL BEHAVIOR OF HYDRAULIC FRACTURING FLUID COMPOUNDS PRIORITIZED BY POTENTIAL OF ENVIRONMENTAL OR HEALTH RISK  

EPA Science Inventory

Given the large number of chemical additives used in hydraulic fracturing fluids, it is not practical to conduct a comprehensive analysis in cases where contamination is suspected. The fate and transport model can identify compounds with high likelihood for transport and pe...

325

Community-based risk assessment of water contamination from high-volume horizontal hydraulic fracturing.  

PubMed

The risk of contaminating surface and groundwater as a result of shale gas extraction using high-volume horizontal hydraulic fracturing (fracking) has not been assessed using conventional risk assessment methodologies. Baseline (pre-fracking) data on relevant water quality indicators, needed for meaningful risk assessment, are largely lacking. To fill this gap, the nonprofit Community Science Institute (CSI) partners with community volunteers who perform regular sampling of more than 50 streams in the Marcellus and Utica Shale regions of upstate New York; samples are analyzed for parameters associated with HVHHF. Similar baseline data on regional groundwater comes from CSI's testing of private drinking water wells. Analytic results for groundwater (with permission) and surface water are made publicly available in an interactive, searchable database. Baseline concentrations of potential contaminants from shale gas operations are found to be low, suggesting that early community-based monitoring is an effective foundation for assessing later contamination due to fracking. PMID:23552652

Penningroth, Stephen M; Yarrow, Matthew M; Figueroa, Abner X; Bowen, Rebecca J; Delgado, Soraya

2013-01-01

326

Risks to biodiversity from hydraulic fracturing for natural gas in the Marcellus and Utica shales.  

PubMed

High-volume horizontal hydraulic fracturing (HVHHF) for mining natural gas from the Marcellus and Utica shales is widespread in Pennsylvania and potentially throughout approximately 280,000 km(2) of the Appalachian Basin. Physical and chemical impacts of HVHHF include pollution by toxic synthetic chemicals, salt, and radionuclides, landscape fragmentation by wellpads, pipelines, and roads, alteration of stream and wetland hydrology, and increased truck traffic. Despite concerns about human health, there has been little study of the impacts on habitats and biota. Taxa and guilds potentially sensitive to HVHHF impacts include freshwater organisms (e.g., brook trout, freshwater mussels), fragmentation-sensitive biota (e.g., forest-interior breeding birds, forest orchids), and species with restricted geographic ranges (e.g., Wehrle's salamander, tongue-tied minnow). Impacts are potentially serious due to the rapid development of HVHHF over a large region. PMID:23701448

Kiviat, Erik

2013-05-01

327

Hydraulic fracturing of the Devonian Shale with a non-damaging fluid  

SciTech Connect

The objectives of this project are: (1) To demonstrate within the Appalachian Basin the use of liquid carbon dioxide (CO{sub 2}) as a medium for hydraulically fracturing the Devonian Shale, while transporting sand as a proppant. The project scope includes considering candidate wells in up to five (5) states, Kentucky, Ohio, Tennessee, Virginia, and West Virginia. (2) To compare and rank the gas production responses from wells treated with liquid CO{sub 2} with other types of treatments (shooting, water based, nitrogen, etc. ). These demonstrations will involve two phases: Phase I -- up to fifteen (15) wells in up to five (5) target areas. (Aug. 93); Phase II -- up to nine (9) wells in up to three (3) target areas [seventeen (17) months].

Mazza, R.L.; Gehr, J.B.

1992-07-01

328

Hydraulic fracturing of the Devonian Shale with a non-damaging fluid  

SciTech Connect

The objectives of this project are: (1) To demonstrate within the Appalachian Basin the use of liquid carbon dioxide (CO{sub 2}) as a medium for hydraulically fracturing the Devonian Shale, while transporting sand as a proppant. The project scope includes considering candidate wells in up to five (5) states, Kentucky, Ohio, Tennessee, Virginia, and West Virginia. (2) To compare and rank the gas production responses from wells treated with liquid CO{sub 2} with other types of treatments (shooting, water based, nitrogen, etc. ). These demonstrations will involve two phases: Phase I -- up to fifteen (15) wells in up to five (5) target areas. (Aug. 93); Phase II -- up to nine (9) wells in up to three (3) target areas (seventeen (17) months).

Mazza, R.L.; Gehr, J.B.

1992-01-01

329

Vertically unstable sacral fractures with neurological insult: outcomes of surgical decompression and reconstruction plate internal fixation  

PubMed Central

During a 4-year period, 32 patients with type C unstable sacral fractures were treated in our university hospital. All patients had neurological deficits as a result of their sacral fracture. The average age was 31.2 (range 22–54) years and the average Hannover Polytrauma Score (PTS) was 24 (range 19–40) points. Twelve patients had zone I fracture, ten had zone II fracture and ten patients had comminuted fractures involving both zones. All patients underwent surgical decompression and reconstruction plate internal fixation. The average follow up period was 24.4 (range 19–47) months. Twenty-one patients (65.6%) had complete neurological recovery, eight patients (25%) had partial recovery and three patients (9.4%) had no recovery. The relationship between radiological and functional scores was evident but insignificant (P?=?0.434). Significantly, the neurological recovery was less favourable in older age groups, pedestrian trauma, vertical shear injuries, comminuted fractures, fifth lumbar root involvement, very low motor power grades and in patients presenting late. Concerning complications, four patients (12.5%) had early infection and five patients (15.6%) had late urological problems and heterotopic ossification. Consequently, we conclude that patients undergoing very early surgical decompression and only reconstruction plate internal fixation can achieve safe early ambulation and better neurological, functional and radiological results.

2007-01-01

330

Spalling and the development of a hydraulic fracturing strategy for coal. Final report, January 1987-February 1991  

SciTech Connect

For commercial development of a large fraction of the United States' coal gas reservoirs, it is important to induce long, highly conductive hydraulic fractures, which intersect the coal seams. To date, high treatment pressures are often observed, resulting in screenout, inadequate length and sometimes out-of-zone growth. Many mechanisms have been proposed to rationalize high treatment pressures. These include poroelasticity, complex fracture geometries and systems, coal spalling, tip plugging, and wellbore failure. Two different approaches were used for identification of high treatment pressure mechanisms in coal. These were laboratory hydraulic fracturing experimentation and post-shut-in pressure decline analysis of field data. The first approach involved hydraulic fracturing of 11 in. {times} 11 in. {times} 15 in. coal blocks under various saturation conditions and far-field stresses. The second approach involved analysis of post-shut-in pressure decline curves for several stimulation records in COMPAS-II database. The conclusions arrived at from two approaches suggest that restricted entry at or near the wellbore is a major cause of high treatment pressures in coal. The laboratory tests further identified two major mechanisms as the causes of the near-wellbore constriction. These are: (1) plugging of the fracture at or near the wellbore, and (2) pore (cleat) pressure buildup around the wellbore.

Khodaverdian, M.; McLennan, J.D.; Jones, A.H.

1991-04-01

331

Pressure solution for sequential hydraulic tests in low-transmissivity fractured and nonfractured media  

NASA Astrophysics Data System (ADS)

In the last decade, considerable effort has been applied to the characterization of low-permeability, heterogeneous formations. A primary reason for the increased activity is the importance of estimating formation properties for use in safety assessments at proposed nuclear waste disposal sites, such as those in Switzerland, Germany, Sweden, and the United States. Methods for determining formation properties (e.g., transmissivity, static head, storativity, and flow boundaries) are varied, but hydraulic testing is commonly used. Hydraulic tests in low-permeability media typically consist of a sequence of multiple test events such as slug, constant pressure, and pulse tests. Each single test event can significantly affect the measured pressure response of subsequent test events. The pressure response can also be affected by borehole mud pressures that occur prior to testing (i.e., pretest pressures) and other factors such as well bore storage, well bore skin, and well bore temperature. We present a new analytical solution that accounts for all of the aforementioned complexities. The solution technique treats a sequence of pretest pressures and multiple test events (slugs, pulses, and shut-ins) as one test sequence, thereby accounting for the influence of one test event upon another. The solution is derived so that only a kernel function, the constant-rate pumping test solution, is required for new flow models. Furthermore, the solution is presented for any flow dimension allowing for interpretation in fractured formations where linear, radial, and fractional flow may exist. We demonstrate the use of the solution by inverse modeling to estimate the flow model and parameters for an example hydraulic test conducted in Switzerland.

Johns, R. T.

1998-04-01

332

Digital Radiography with Computerized Conventional Monitors Compared to Medical Monitors in Vertical Root Fracture Diagnosis  

PubMed Central

Introduction Vertical root fracture (VRF) is a complication which is chiefly diagnosed radiographically. Recently, film-based radiography has been substituted with digital radiography. At the moment, there is a wide range of monitors available in the market for viewing digital images. The present study aims to compare the diagnostic accuracy, sensitivity and specificity of medical and conventional monitors in detection of vertical root fractures. Material and Methods In this in vitro study 228 extracted single-rooted human teeth were endodontically treated. Vertical root fractures were induced in 114 samples. The teeth were imaged by a digital charge-coupled device radiography using parallel technique. The images were evaluated by a radiologist and an endodontist on two medical and conventional liquid-crystal display (LCD) monitors twice. Z-test was used to analyze the sensitivity, accuracy and specificity of each monitor. Significance level was set at 0.05. Inter and intra observer agreements were calculated by Cohen’s kappa. Results Accuracy, specificity and sensitivity for conventional monitor were calculated as 67.5%, 72%, 62.5% respectively; and data for medical grade monitor were 67.5%, 66.5% and 68% respectively. Statistical analysis showed no significant differences in detecting VRF between the two techniques. Inter-observer agreement for conventional and medical monitor was 0.47 and 0.55 respectively (moderate). Intra-observer agreement was 0.78 for medical monitor and 0.87 for conventional one (substantial). Conclusion The type of monitor does not influence diagnosis of vertical root fractures.

Tofangchiha, Maryam; Adel, Mamak; Bakhshi, Mahin; Esfehani, Mahsa; Nazeman, Pantea; Ghorbani Elizeyi, Mojgan; Javadi, Amir

2013-01-01

333

Restoration of a vertical tooth fracture and a badly mutilated tooth using canal projection.  

PubMed

Management of vertically fractured tooth or a perforation frequently poses problem during endodontic management. Such teeth often need a pre-endodontic restoration prior to initiation of root canal therapy to aid in the placement of rubber dam clamp. This paper describes a simple method of placement of a pre-endodontic restoration using the canal projection technique using hollow metallic needles as sleeves. PMID:17502715

Velmurugan, N; Bhargavi, N; Lakshmi, Neelima; Kandaswamy, D

2007-01-01

334

Hydraulics  

NSDL National Science Digital Library

These interactive learning objects, created by instructors from Fox Valley Technical College and other colleges in the Wisconsin Technical College program, focus on concepts that cover a broad-based electromechanical program. Here visitors will find learning objects in Hydraulics with over 25 lessons in Actuators, Relief Valves, Basic Concepts, and Directional Control Valves.

2011-01-03

335

New treatment option for an incomplete vertical root fracture-a preliminary case report  

PubMed Central

Instead of extraction this case report presents an alternative treatment option for a maxillary incisor with a vertical root fracture (VRF) causing pain in a 78-year-old patient. After retreatment of the existing root canal filling the tooth was stabilized with a dentine adhesive and a composite restoration. Then the tooth was extracted, the VRF gap enlarged with a small diamond bur and the existing retrograde root canal filling removed. The enlarged fracture line and the retrograde preparation were filled with a calcium-silicate-cement (Biodentine). Afterwards the tooth was replanted and a titanium trauma splint was applied for 12d. A 24 months clinical and radiological follow-up showed an asymptomatic tooth, reduction of the periodontal probing depths from 7 mm prior to treatment to 3 mm and gingival reattachment in the area of the fracture with no sign of ankylosis. Hence, the treatment of VRF with Biodentine seems to be a possible and promising option.

2014-01-01

336

Vertical Root Fracture: Preservation of the Alveolar Ridge Using Immediate Implants  

PubMed Central

Teeth with vertical root fracture (VRF) have complete or incomplete fractures that begin in the root and extend toward the occlusal surface. The most frequent causes of VRF originate from physical trauma, occlusal prematurity, inadequate endodontic treatment, and iatrogenic causes. Diagnose is difficult and delay can cause stomatognathic system problem. The purpose of this case report was to evaluate immediate implant placement after extraction of teeth with vertical root fracture. For the 1st case, the VRF in 1st left lower molar was confirmed during surgical flap and at the same time, the tooth was removed and immediate implant was placed. For the 2nd case, the VRF 1st left lower molar was confirmed during endodontic access and at the same appointment, the tooth was removed and the immediate implant is placed. Several studies have shown that immediate implants have similar success rates when compared with late implants. Consider that this approach is a safe procedure with favorable prognosis. In cases of VRF, the main factor to be considered is the presence of adequate bone support and immediate implants can preserve the vertical bone height, adding the fact that good patient compliance reduces the number of surgical interventions and promotes the functionality of stomatognathic system.

Oya, Edmar de Oliveira; Pallos, Debora; Schwartz-Filho, Humberto Osvaldo; Brandt, William Cunha; Sendyk, Wilson Roberto; Roman-Torres, Caio Vinicius Goncalves

2014-01-01

337

Numerical and experimental investigation of buoyancy-driven dissolution in vertical fracture  

NASA Astrophysics Data System (ADS)

Alteration and dissolution resulting from reactive fluid flows in vertical fracture are investigated from numerical and laboratory experiments. Due to fluid density contrast, buoyancy effects are observed leading to significant changes in fracture geometry. Buoyant and forced convection forces act here in the same direction. The experiments were carried out at two different flow rates. When buoyancy forces are preponderant (low injection flow rate), the dissolution rate increases with the vertical distance. By contrast, for convection-dominated transport (high injection flow rate), a uniform dissolution is observed. Using numerical simulations, four dissolution regimes were identified. The fracture patterns observed strongly depend on the characteristic dimensionless numbers of the process, respectively, the Richardson, Damköhler, and Péclet numbers. The good agreement between numerical simulations and experimental results in terms of fracture patterns highlights the capability of the numerical model to describe the complex coupling between flow dynamics, buoyancy, and chemical reaction. Finally, a 3-D behavior diagram is constructed to illustrate these interactions and as a means of relating the appropriate dimensionless parameters to the morphological changes observed.

OltéAn, Constantin; Golfier, Fabrice; BuèS, Michel Antoine

2013-05-01

338

Hydraulic fracturing in unconventional reservoirs - Identification of hazards and strategies for a quantitative risk assessment  

NASA Astrophysics Data System (ADS)

The production of unconventional gas resources, which require a fracking process to be released, such as shale gas, tight gas and coal bed methane, has become an economically attractive technology for a continued supply of fossil-fuel energy sources in many countries. Just recently, a major focus of interest has been directed to hydraulic fracking in Germany. The technology is controversial since it involves severe risks. The main difference in risk with respect to other technologies in the subsurface such as carbon sequestration is that fracking is remunerative, and it is important to distinguish between economical and environmental issues. The hydrofracking process may pose a threat to groundwater resources if fracking fluid or brine can migrate through fault zones into shallow aquifers. Diffuse methane emissions from the gas reservoir may not only contaminate shallow groundwater aquifers but also escape into the atmosphere where methane acts as a greenhouse gas. The working group "Risks in the Geological System" as part of ExxonMobil's hydrofracking dialogue and information dissemination processes was tasked with the assessment of possible hazards posed by migrating fluids as a result of hydrofracking activities. In this work several flow paths for fracking fluid, brine and methane are identified and scenarios are set up to qualitatively estimate under what circumstances these fluids would leak into shallower layers. The parametrization for potential fracking sites in North Rhine-Westphalia and Lower Saxony (both in Germany) is derived from literature using upper and lower bounds of hydraulic parameters. The results show that a significant fluid migration is only possible if a combination of several conservative assumptions are met by a scenario. Another outcome of this work is the demand for further research, as many of the involved processes in the hydrofracking process have yet not been fully understood (e.g. quantification of source terms for methane in the fractured reservoir, fracture propagation, fault zones and their role in regard to fluid migration into shallow aquifers). A quantitative risk assessment which should be the main aim of future work in this field has much higher demands, especially on site specific data, as the estimation of statistical parameter uncertainty requires site specific parameter distributions. There is already ongoing research on risk assessment in related fields like CO2 sequestration. We therefore propose these methodologies to be transferred to risk estimation relating to the use of the hydraulic fracking method, be it for unconventional gas or enhanced geothermal energy production. The overall aim should be to set common and transparent standards for different uses of the subsurface and their involved risks and communicate those to policy makers and stake holders.

Helmig, R.; Kissinger, A.; Class, H.; Ebigbo, A.

2012-12-01

339

A laboratory and field evaluation of a technique for hydraulic fracturing stimulation of deep wells  

SciTech Connect

In 1981, over 1,000 new wells were drilled below 15,000 feet. Although bottom hole temperatures in these wells vary widely, all have a number of similar characteristics which make hydraulic fracturing treatments very difficult. The high treating pressures encountered necessitate the use of fluids with minimal pumping friction pressures. The high closure pressures often require the use of high strength proppants which are more difficult to transport than sand. Low formation permeabilities dictate the need for long propped fractures to achieve the desired production increase and thus long term fluid stability is required. To minimize contraction in long tubing strings, treating fluids often must be preheated (100-140/sup 0/F). The high initial fluid temperatures can alter fluid properties downhole. The expected effective viscosity of treating fluids as a function of time and temperature is of key importance to the design of stimulation treatments for these wells. In most cases, crosslinked gels are the fluid of choice for stimulation treatments, and most crosslinked fluids are shear history dependent, therefore possessing no unique rheological characteristics. A laboratory method has been developed to more concisely evaluate the role of the above parameters and data is presented demonstrating the magnitude of the effects on the time-temperature stability of the crosslinked fluid. Results from both a laboratory and field evaluation of various techniques are discussed.

Conway, M.W.; Harris, L.E.

1982-09-01

340

Acoustic emission monitoring of hydraulic fracturing laboratory experiment with supercritical and liquid CO2  

NASA Astrophysics Data System (ADS)

Carbon dioxide (CO2) is often used for enhanced oil recovery in depleted petroleum reservoirs, and its behavior in rock is also of interest in CO2 capture and storage projects. CO2 usually becomes supercritical (SC-CO2) at depths greater than 1,000 m, while it is liquid (L-CO2) at low temperatures. The viscosity of L-CO2 is one order lower than that of normal liquid water, and that of SC-CO2 is much lower still. To clarify fracture behavior induced with injection of the low viscosity fluids, we conducted hydraulic fracturing experiments using 17 cm cubic granite blocks. The AE sources with the SC- and L-CO2 injections tend to distribute in a larger area than those with water injection, and furthermore, SC-CO2 tended to generate cracks extending more three dimensionally rather than along a flat plane than L-CO2. It was also found that the breakdown pressures for SC- and L-CO2 injections are expected to be considerably lower than for water.

Ishida, Tsuyoshi; Aoyagi, Kazuhei; Niwa, Tomoya; Chen, Youqing; Murata, Sumihiko; Chen, Qu; Nakayama, Yoshiki

2012-08-01

341

Separate Vertical Wiring for the Fixation of Comminuted Fractures of the Inferior Pole of the Patella  

PubMed Central

Purpose Among patients over 50 years of age, separate vertical wiring alone may be insufficient for fixation of fractures of the inferior pole of the patella. Therefore, mechanical and clinical studies were performed in patients over the age of 50 to test the strength of augmentation of separate vertical wiring with cerclage wire (i.e., combined technique). Materials and Methods Multiple osteotomies were performed to create four-part fractures in the inferior poles of eight pairs of cadaveric patellae. One patella from each pair was fixed with the separate wiring technique, while the other patella was fixed with a combined technique. The ultimate load to failure and stiffness of the fixation were subsequently measured. In a clinical study of 21 patients (average age of 64 years), comminuted fractures of the inferior pole of the patellae were treated using the combined technique. Operative parameters were recorded from which post-operative outcomes were evaluated. Results For cadaveric patellae, whose mean age was 69 years, the mean ultimate loads to failure for the separate vertical wiring technique and the combined technique were 216.4±72.4 N and 324.9±50.6 N, respectively (p=0.012). The mean stiffness for the separate vertical wiring technique and the combined technique was 241.1±68.5 N/mm and 340.8±45.3 N/mm, respectively (p=0.012). In the clinical study, the mean clinical score at final follow-up was 28.1 points. Conclusion Augmentation of separate vertical wiring with cerclage wire provides enough strength for protected early exercise of the knee joint and uneventful healing.

Song, Hyung Keun; Yoo, Je Hyun; Byun, Young Soo

2014-01-01

342

Multicomponent seismic monitoring of the effective stimulated volume associated with hydraulic fracture stimulations in a shale reservoir, Pouce Coupe field, Alberta, Canada  

NASA Astrophysics Data System (ADS)

The Reservoir Characterization Project in conjunction with Talisman Energy Inc., have been investigating a time-lapse data set acquired during hydraulic fracture stimulations of two horizontal wells in the Montney Shale at Pouce Coupe Field, Alberta, Canada. Multicomponent seismic surveys and microseismic data were acquired in December 2008 and integrated in this study with multiscale, multidisciplinary reservoir characterization techniques, including geomechanics and production data, to monitor changes within the reservoir associated with the hydraulic fracture stimulations. The goal of this investigation was to study the feasibility of microseismic and time-lapse multicomponent seismic data for correlating hydraulic stimulation success to the enhanced permeability pathways created during the stimulation process. Three independently acquired microseismic monitoring surveys and the detected microseismic events were analyzed to infer the fracture length, height, azimuth, and asymmetry created by the hydraulic stimulation. Integrating the interpretation objectives with the multicomponent surface seismic processing sequence elevated the level of reservoir characterization that can be performed using the Pouce Coupe converted-wave seismic data. Shear-wave splitting as observed by the newly processed converted-wave data were sensitive to fracture induced anisotropy and therefore, provided a measurement of the dominant fracture orientation and fracture density difference within the Montney reservoir interval. Before hydraulic stimulations, the natural fracture conditions resulted in a measured shear-wave splitting magnitude of 2-3%, with Baseline anomalies matching the independently interpreted minimal offset faults only visible on the converted-wave seismic data. Multistage hydraulic fracture stimulations increased the magnitude of shear-wave splitting up to 8%, well above the background noise level of 1%. The natural fractures and faults acted as conduits or barriers to the hydraulic stimulation energy causing a complicated stimulation response in the shear-wave splitting anomalies, due to the interaction between natural and hydraulic fractures. Characterizing the natural fractures and their failure tendencies can help drive the development of such a reservoir because fracture characteristics appeared to govern hydraulic stimulation success. Conventional microseismic interpretation was deemed an unsatisfactory monitoring method of hydraulic fracture stimulations due to the limitation of only detecting the shear-failure events, representing a small amount of the total energy released during fracturing. The affected reservoir monitored by microseismic was concluded to not be characteristic of the volume contributing to production; therefore, the opening and propping of natural fractures were interpreted using shear-wave splitting monitoring and gave rise to a better representation of the effective stimulated volume. Finally, correlation of the overall shear-wave splitting anomalies to the stage-by-stage spinner production data concludes that shear-wave splitting monitoring better distinguishes the effective stimulated volume contributing to production.

Steinhoff, Christopher

343

Combining steam injection with hydraulic fracturing for the in situ remediation of the unsaturated zone of a fractured soil polluted by jet fuel.  

PubMed

A steam injection pilot-scale experiment was performed on the unsaturated zone of a strongly heterogeneous fractured soil contaminated by jet fuel. Before the treatment, the soil was stimulated by creating sub-horizontal sand-filled hydraulic fractures at three depths. The steam was injected through one hydraulic fracture and gas/water/non-aqueous phase liquid (NAPL) was extracted from the remaining fractures by applying a vacuum to extraction wells. The injection strategy was designed to maximize the heat delivery over the entire cell (10 m × 10 m × 5 m). The soil temperature profile, the recovered NAPL, the extracted water, and the concentrations of volatile organic compounds (VOCs) in the gas phase were monitored during the field test. GC-MS chemical analyses of pre- and post-treatment soil samples allowed for the quantitative assessment of the remediation efficiency. The growth of the heat front followed the configuration of hydraulic fractures. The average concentration of total hydrocarbons (g/kg of soil) was reduced by ? 43% in the upper target zone (depth = 1.5-3.9 m) and by ? 72% over the entire zone (depth = 1.5-5.5 m). The total NAPL mass removal based on gas and liquid stream measurements and the free-NAPL product were almost 30% and 2%, respectively, of those estimated from chemical analyses of pre- and post-treatment soil samples. The dominant mechanisms of soil remediation was the vaporization of jet fuel compounds at temperatures lower than their normal boiling points (steam distillation) enhanced by the ventilation of porous matrix due to the forced convective flow of air. In addition, the significant reduction of the NAPL mass in the less-heated deeper zone may be attributed to the counter-current imbibition of condensed water from natural fractures into the porous matrix and the gravity drainage associated with seasonal fluctuations of the water table. PMID:21030134

Nilsson, Bertel; Tzovolou, Dimitra; Jeczalik, Maciej; Kasela, Tomasz; Slack, William; Klint, Knud E; Haeseler, Frank; Tsakiroglou, Christos D

2011-03-01

344

Combined interpretation of radar, hydraulic, and tracer data from a fractured-rock aquifer near Mirror Lake, New Hampshire, USA  

USGS Publications Warehouse

An integrated interpretation of field experimental cross-hole radar, tracer, and hydraulic data demonstrates the value of combining time-lapse geophysical monitoring with conventional hydrologic measurements for improved characterization of a fractured-rock aquifer. Time-lapse difference-attenuation radar tomography was conducted during saline tracer experiments at the US Geological Survey Fractured Rock Hydrology Research Site near Mirror Lake, Grafton County, New Hampshire, USA. The presence of electrically conductive saline tracer effectively illuminates permeable fractures or pathways for geophysical imaging. The geophysical results guide the construction of three-dimensional numerical models of ground-water flow and solute transport. In an effort to explore alternative explanations for the tracer and tomographic data, a suite of conceptual models involving heterogeneous hydraulic conductivity fields and rate-limited mass transfer are considered. Calibration data include tracer concentrations, the arrival time of peak concentration at the outlet, and steady-state hydraulic head. Results from the coupled inversion procedure suggest that much of the tracer mass migrated outside the three tomographic image planes, and that solute is likely transported by two pathways through the system. This work provides basic and site-specific insights into the control of permeability heterogeneity on ground-water flow and solute transport in fractured rock. ?? Springer-Verlag 2004.

Day-Lewis, F. D.; Lane, Jr. , J. W.; Gorelick, S. M.

2006-01-01

345

Correlations Developed for Estimation of Hydraulic Parameters of Rough Fractures Through the Simulation of JRC Flow Channels  

NASA Astrophysics Data System (ADS)

The hydro-mechanical response of fractured rock masses is complex, due partly to the presence of fractures at different scales. Surface morphology has a significant influence on fluid flow behaviour of a fracture. Different empirical correlations and statistical models have been proposed to estimate the equivalent hydraulic aperture and determine the pressure drop along a fracture. However, the existing models suffer from not being adequately generalised to be applicable to a wide range of real fracture surfaces. To incorporate the effect of profile roughness in the hydro-mechanical behaviour of fractured rock masses, the joint roughness coefficient (JRC) is the most widely used empirical approach. However, the average JRC of two fracture walls in fluid flow analysis, as is a common practice, appears to be inappropriate. It will be shown how different combinations of pairs of JRCs could lead to a similar JRC value. Also, changing the position of the top and bottom walls of a fracture can significantly change the hydraulic response of the fracture while the average JRC is identical in both cases. In this paper, correlations are developed which are based on the simulation of JRCs using estimated fluid flow parameters of 2D fractures can be estimated. In order to widen the application range of the correlations, JRC flow channels were generated: these are 2D channels with their top and bottom walls being made from two of the JRC profiles. To estimate the JRC of linear profiles, a correlation developed between JRC and a newly developed Riemannian roughness parameter, D R1, is proposed. Considering ten JRC profiles, a total of 100 JRC flow channels were generated. In order to only investigate the effect of surface roughness on fluid flow, the minimum closure between the top and bottom walls of JRC flow channels were considered to be constant. Three cases with minimum closures of 0.01, 0.05 and 0.10 cm were considered in this study. All JRC flow channels were subjected to fluid analysis using FLUENT software. Based on these results, correlations were developed between the geometrical and hydraulic properties of flow channels. Analysis of several real fractures demonstrated the applicability of these correlations.

Rasouli, V.; Hosseinian, A.

2011-07-01

346

Long-Period Oscillations of Hydraulic Fractures: Attenuation, Scaling Relationships, and Flow Stability  

NASA Astrophysics Data System (ADS)

Long-period seismicity due to the excitation of hydraulic fracture normal modes is thought to occur in many geological systems, including volcanoes, glaciers and ice sheets, and hydrocarbon reservoirs. To better quantify the physical dimensions of fluid-filled cracks and properties of the fluid within them, we study wave motion along a thin hydraulic fracture waveguide. We present a linearized analysis that accounts for quasi-dynamic elasticity of the fracture wall, as well as fluid drag, inertia, and compressibility. We consider symmetric perturbations and neglect the effects of stratification and gravity. In the long-wavelength or thin-fracture limit, dispersive guided waves known as crack waves propagate with phase velocity cw=?(G*|k|w/?), where G* = G/(1-?) for shear modulus G and Poisson ratio ?, w is the crack half-width, k is the wavenumber, and ? is the fluid density. Restoring forces from elastic wall deformation drive wave motions. In the opposite, short-wavelength limit, guided waves are simply sound waves within the fluid and little seismic excitation occurs due to minimal fluid-solid coupling. We focus on long-wavelength crack waves, which, in the form of standing wave modes in finite-length cracks, are thought to be a common mechanism for long-period seismicity. The dispersive nature of crack waves implies several basic scaling relations that might be useful when interpreting statistics of long-period events. Seismic observations may constrain a characteristic frequency f0 and seismic moment M0~G?wR2, where ?w is the change in crack width and R is the crack dimension. Resonant modes of a fluid-filled crack have associated frequencies f~cw/R. Linear elasticity provides a link between pressure changes ?p in the crack and the induced opening ?w: ?p~G ?w/R. Combining these, and assuming that pressure changes have no variation with crack dimension, leads to the scaling law relating seismic moment and oscillation frequency, M0~(Gw?p/?)f0-2. This contrasts with the well-known self-similar earthquake scaling M0?f0-3. Attenuation of long-period crack waves is due to both drag within the fluid and radiative energy losses from excitation of seismic waves. Fluid drag may be characterized by either a turbulent or laminar viscous law. We present a thorough characterization of viscous damping that is valid at both low frequencies, where the flow is always fully developed, and at high frequencies, where fluid inertia becomes important. We have derived simple formulas for the quality factor due to viscous attenuation. Waves may become unstable for sufficiently fast background fluid velocity u0. This instability, first proposed by Julian (1994), was further investigated by Dunham and Ogden (2012), who determined the instability condition, u0>cw/2. We establish a more general result: that the stability condition is not only independent of viscosity, but also uninfluenced by fluid inertia, although both do alter growth rates. We also show that radiation damping (excitation of plane P waves normal to the crack walls) has only a stabilizing effect. This work suggests that under geologically relevant conditions, crack wave propagation is most likely stable, and the occurrence of long-period oscillations thus requires some additional excitation process.

Lipovsky, B.; Dunham, E. M.

2013-12-01

347

Methane contamination of drinking water accompanying gas-well drilling and hydraulic fracturing.  

PubMed

Directional drilling and hydraulic-fracturing technologies are dramatically increasing natural-gas extraction. In aquifers overlying the Marcellus and Utica shale formations of northeastern Pennsylvania and upstate New York, we document systematic evidence for methane contamination of drinking water associated with shale-gas extraction. In active gas-extraction areas (one or more gas wells within 1 km), average and maximum methane concentrations in drinking-water wells increased with proximity to the nearest gas well and were 19.2 and 64 mg CH(4) L(-1) (n = 26), a potential explosion hazard; in contrast, dissolved methane samples in neighboring nonextraction sites (no gas wells within 1 km) within similar geologic formations and hydrogeologic regimes averaged only 1.1 mg L(-1) (P < 0.05; n = 34). Average ?(13)C-CH(4) values of dissolved methane in shallow groundwater were significantly less negative for active than for nonactive sites (-37 ± 7‰ and -54 ± 11‰, respectively; P < 0.0001). These ?(13)C-CH(4) data, coupled with the ratios of methane-to-higher-chain hydrocarbons, and ?(2)H-CH(4) values, are consistent with deeper thermogenic methane sources such as the Marcellus and Utica shales at the active sites and matched gas geochemistry from gas wells nearby. In contrast, lower-concentration samples from shallow groundwater at nonactive sites had isotopic signatures reflecting a more biogenic or mixed biogenic/thermogenic methane source. We found no evidence for contamination of drinking-water samples with deep saline brines or fracturing fluids. We conclude that greater stewardship, data, and-possibly-regulation are needed to ensure the sustainable future of shale-gas extraction and to improve public confidence in its use. PMID:21555547

Osborn, Stephen G; Vengosh, Avner; Warner, Nathaniel R; Jackson, Robert B

2011-05-17

348

Methane contamination of drinking water accompanying gas-well drilling and hydraulic fracturing  

PubMed Central

Directional drilling and hydraulic-fracturing technologies are dramatically increasing natural-gas extraction. In aquifers overlying the Marcellus and Utica shale formations of northeastern Pennsylvania and upstate New York, we document systematic evidence for methane contamination of drinking water associated with shale-gas extraction. In active gas-extraction areas (one or more gas wells within 1 km), average and maximum methane concentrations in drinking-water wells increased with proximity to the nearest gas well and were 19.2 and 64 mg CH4 L-1 (n = 26), a potential explosion hazard; in contrast, dissolved methane samples in neighboring nonextraction sites (no gas wells within 1 km) within similar geologic formations and hydrogeologic regimes averaged only 1.1 mg L-1 (P < 0.05; n = 34). Average ?13C-CH4 values of dissolved methane in shallow groundwater were significantly less negative for active than for nonactive sites (-37 ± 7‰ and -54 ± 11‰, respectively; P < 0.0001). These ?13C-CH4 data, coupled with the ratios of methane-to-higher-chain hydrocarbons, and ?2H-CH4 values, are consistent with deeper thermogenic methane sources such as the Marcellus and Utica shales at the active sites and matched gas geochemistry from gas wells nearby. In contrast, lower-concentration samples from shallow groundwater at nonactive sites had isotopic signatures reflecting a more biogenic or mixed biogenic/thermogenic methane source. We found no evidence for contamination of drinking-water samples with deep saline brines or fracturing fluids. We conclude that greater stewardship, data, and—possibly—regulation are needed to ensure the sustainable future of shale-gas extraction and to improve public confidence in its use.

Osborn, Stephen G.; Vengosh, Avner; Warner, Nathaniel R.; Jackson, Robert B.

2011-01-01

349

Directional hydraulic behavior of a fractured-shale aquifer in New Jersey  

USGS Publications Warehouse

The principal source of ground water throughout a large part of central and northeastern New Jersey is the aquifer in the Brunswick Shale -- the youngest unity of the Newark Group of Triassic Age. Large-diameter public-supply and industrial wells tapping the Brunswick Shale commonly yield several hundred gallons per minute each. Virtually all ground water in this aquifer occurs in interconnecting fractures; the formation has practically no effective primary porosity. Numerous pumping tests have shown that the aquifer exhibits directional, rather than isotropic, hydraulic behavior. Water levels in wells alined along the strike of the formation show greater magnitude of interference than those in wells alined in transverse directions. Drawdown data evaluated by standard time-drawdown methods indicate computed coefficient of transmissibility in all cases is least in the direction of strike. Because of the distribution of observation wells available for the tests, distance-drawdown methods of evaluation could be used in only one instance -- for just one direction; the computed coefficient compared favorably with that calculated from the time-drawdown method. Computed values of transmissibility may be unreliable owing to the departure of the aquifer from the ideal model. It is even possible that the direction of minimum computed transmissiblity is actually indicative of the alinement of fractures with the greatest permeability. However, the relation of the directional behavior to the structure of the formation has practical significance when locating the new wells near existing wells. Well interference can be greatly minimized, generally, by alining wells perpendicular to the strike.

Vecchioli, John

1965-01-01

350

Assessing the risk of groundwater contamination posed by hydraulic fracturing through the use of a fault tree assisted numerical model  

NASA Astrophysics Data System (ADS)

Shale gas exploitation in the United States is an increasingly important resource, since 2007 the production of shale gas has increased at an average annual rate of 44%. The increasing importance of shale gas to U.S. energy production and energy security necessitates an appropriate risk assessment of all processes of hydraulic fracturing to ensure its continued safety. This paper seeks to address the methodology needed to develop a quantitative risk assessment of hydraulic fracturing on subsurface aquifers using a fault tree in conjunction with a numerical model. The model incorporates geologic uncertainty through the use of a Monte Carlo simulation. The workflow of the model is presented through the use of a case study site within the Marcellus Shale.

Montague, J.; Pinder, G. F.

2013-12-01

351

Validation of Rapid Radiochemical Method for Gross Alpha and Gross Beta Activity Concentration in Flowback and Produced Waters from Hydraulic Fracturing Operations  

EPA Science Inventory

This report summarizes the development and validation of an improved method for the Determination of Gross Alpha and Gross Beta Activity in Flowback and Produced Waters from Hydraulic Fracturing Operations (FPWHFO). Flowback and produced waters are characterized by high concentra...

352

Coronally oriented vertical fracture of the axis body: surgical treatment of a rare condition.  

PubMed

The neurosurgical management in a rare case of vertical axis fracture is presented along with discussion of the supposed pathogenetic mechanisms and the biomechanics underlying this type of cervical spine injury. Comprehensive neuroradiological investigation prior to surgery clearly demonstrated the dislocation of the anterior part of the axis body with concomitant C 2/C 3-disk injury. Therefore, the unstable fracture had to be managed by a one-time combined ventrodorsal approach using anterior C 2-C 3 locking plate fusion and C 2 bilateral dorsal transpedicular screw fixation. No operative morbidity resulted from this procedure, and stable bony fusion was achieved with minimal restriction of head mobility and with minor residual complaints. This case illustrates the variable biomechanical response of the upper cervical spine to trauma and the advantages of a non-standard surgical approach for internal fixation of the injured cervical spine. PMID:9651918

Rainov, N G; Heidecke, V; Burkert, W

1998-06-01

353

Transient gas or liquid flow along a preexisting or hydraulically-induced fracture in a permeable medium  

SciTech Connect

Similarity solutions are derived for the trasient two-dimensional flow of a gas or liquid along an isolated fracture in a permeable medium. The driving pressure at the fracture inlet is constant, and the confining stress is uniform. Two different cases are considered, pre-existing fractures with uniform aperture as well as hydraulic fractures with a variable aperture proportional to the local overpressure (fluid pressure less confining stress). The evolution of the pressure distribution is described by a set of four asymptotic solutions, each having a self-similar form. At early times the flow in the fracture is turbulent, and Darcian seepage losses into the porous surroundings are negligible. At late times the flow in the fracture is laminar, and seepage losses become a dominant consideration. At intermediate times there are two alternative asymptotes, depending upon physical parameters. The mathematical model also describe the flow along a fracture which is fulled with high-permeability porous material as well as the flow in an assemblage of porous blocks. 19 refs., 10 figs.

Nilson, R.H.; Morrison, F.A. Jr.

1985-05-01

354

Hydraulic stimulation of natural fractures as revealed by induced microearthquakes, Carthage Cotton Valley gas field, east Texas  

Microsoft Academic Search

ABSTRACT Wehave,produced a high-resolution microseismic image of a hydraulic fracture stimulation in the Carthage Cotton Valley gas field of east Texas. Gas is produced from multiple, low-permeability sands within an interbedded sand-shale sequence. We improved the precision of microseismic event locations 4-fold over initial locations by manually repicking the waveforms,in a spatial sequence, allowing us to visually correlate waveforms of

James T. Rutledge; W. Scott Phillips

2003-01-01

355

Characterizing fractured rock aquifers using heated Distributed Fiber-Optic Temperature Sensing to determine borehole vertical flow  

NASA Astrophysics Data System (ADS)

In highly heterogeneous media, fracture network connectivity and hydraulic properties can be estimated using methods such as packer- or cross-borehole pumping-tests. Typically, measurements of hydraulic head or vertical flow in such tests are made either at a single location over time, or at a series of depths by installing a number of packers or raising or lowering a probe. We show how this often encountered monitoring problem, with current solutions sacrificing either one of temporal or spatial information, can be addressed using Distributed Temperature Sensing (DTS). Here, we electrically heat the conductive cladding materials of cables deployed in boreholes to determine the vertical flow profile. We present results from heated fiber optic cables deployed in three boreholes in a fractured rock aquifer at the much studied experimental site near Ploemeur, France, allowing detailed comparisons with alternative methods (e.g. Le Borgne et al., 2007). When submerged in water and electrically heated, the cable very rapidly reaches a steady state temperature (less than 60 seconds). The steady state temperature of the heated cable, measured using the DTS method, is then a function of the velocity of the fluid in the borehole. We find that such cables are sensitive to a wide range of fluid velocities, and thus suitable for measuring both ambient and pumped flow profiles at the Ploemeur site. The cables are then used to monitor the flow profiles during all possible configurations of: ambient flow, cross-borehole- (pumping one borehole, and observing in another), and dipole-tests (pumping one borehole, re-injection in another). Such flow data acquired using DTS may then be used for tomographic flow inversions, for instance using the approach developed by Klepikova et al., (submitted). Using the heated fiber optic method, we are able to observe the flow response during such tests in high spatial detail, and are also able to capture temporal flow dynamics occurring at the start of both the pumping and recovery phase of cross-borehole- and dipole- tests. In addition, the clear advantage of this is that by deploying a single fiber optic cable in multiple boreholes at a site, the flow profiles in all boreholes can be simultaneously measured, allowing many different pumping experiments to be conducted and monitored in a time efficient manner. Klepikova M. V., Le Borgne T., Bour O., and J-R.de Dreuzy, Inverse modelling of flow tomography experiments in fractured media, submitted to Water Resources Research. Le Borgne T., Bour O., Riley M. S., Gouze P., Pezard P.A., Belghoul A., Lods G., Le Provost R., Greswell R. B., Ellis P.A., Isakov E., and B. J. Last, Comparison of alternative methodologies for identifying and characterizing preferential flow paths in heterogeneous aquifers. Journal of Hydrology 2007, 345, 134-148.

Read, T. O.; Bour, O.; Selker, J. S.; Le Borgne, T.; Bense, V.; Hochreutener, R.; Lavenant, N.

2013-12-01

356

Educating students and stakeholders about shale gas production using a physical model of hydraulic fracturing  

NASA Astrophysics Data System (ADS)

Natural gas from shale gas deposits in the United States can potentially help reduce the dependency on foreign energy sources, reduce greenhouse gas emissions, and improve economic development in currently depressed regions of the country. However, the hydraulic fracturing process (';fracking') employed to release natural gas from formation such as the Marcellus Shale in New York State and Pennsylvania carries significant environmental risks, in particular for local and regional water resources. The current polarized discussion of the topic needs to be informed by sound data and a better understanding of the technical, scientific, social, and economic aspects of hydrofracking. We developed, built and tested an interactive portable physical model of the gas production by hydrofracking that can be used in class rooms and at public events to visualize the procedures and associated risks including the dynamics of water, gas and fracking fluids. Dyes are used to identify shale, fracking fluids and backflow and can be traced in the adjacent groundwater system. Gas production is visualized by a CO2 producing acid/bicarbonate solution reaction. The tank was shown to considerably improve knowledge of environmental issues related to unconventional gas production by hydrofracking in an advanced undergraduate course.

Stute, M.; Garten, L.

2013-12-01

357

Physical, chemical, and biological characteristics of compounds used in hydraulic fracturing.  

PubMed

Hydraulic fracturing (HF), a method to enhance oil and gas production, has become increasingly common throughout the U.S. As such, it is important to characterize the chemicals found in HF fluids to evaluate potential environmental fate, including fate in treatment systems, and human health impacts. Eighty-one common HF chemical additives were identified and categorized according to their functions. Physical and chemical characteristics of these additives were determined using publicly available chemical information databases. Fifty-five of the compounds are organic and twenty-seven of these are considered readily or inherently biodegradable. Seventeen chemicals have high theoretical chemical oxygen demand and are used in concentrations that present potential treatment challenges. Most of the HF chemicals evaluated are non-toxic or of low toxicity and only three are classified as Category 2 oral toxins according to standards in the Globally Harmonized System of Classification and Labeling of Chemicals; however, toxicity information was not located for thirty of the HF chemicals evaluated. Volatilization is not expected to be a significant exposure pathway for most HF chemicals. Gaps in toxicity and other chemical properties suggest deficiencies in the current state of knowledge, highlighting the need for further assessment to understand potential issues associated with HF chemicals in the environment. PMID:24853136

Stringfellow, William T; Domen, Jeremy K; Camarillo, Mary Kay; Sandelin, Whitney L; Borglin, Sharon

2014-06-30

358

Source and fate of hydraulic fracturing water in the Barnett Shale: a historical perspective.  

PubMed

Considerable controversy continues about water availability for and potential impacts of hydraulic fracturing (HF) of hydrocarbon assets on water resources. Our objective was to quantify HF water volume in terms of source, reuse, and disposal, using the Barnett Shale in Texas as a case study. Data were obtained from commercial and state databases, river authorities, groundwater conservation districts, and operators. Cumulative water use from ? 18,000 (mostly horizontal) wells since 1981 through 2012 totaled ? 170,000 AF (210 Mm(3)); ? 26 000 AF (32 Mm(3)) in 2011, representing 32% of Texas HF water use and ? 0.2% of 2011 state water consumption. Increase in water use per well by 60% (from 3 to 5 Mgal/well; 0.011-0.019 Mm(3)) since the mid-2000s reflects the near-doubling of horizontal-well lengths (2000-3800 ft), offset by a reduction in water-use intensity by 40% (2000-1200 gal/ft; 2.5-1.5 m(3)/m). Water sources include fresh surface water and groundwater in approximately equal amounts. Produced water amount is inversely related to gas production, exceeds HF water volume, and is mostly disposed in injection wells. Understanding the historical evolution of water use in the longest-producing shale play is invaluable for assessing its water footprint for energy production. PMID:24467212

Nicot, Jean-Philippe; Scanlon, Bridget R; Reedy, Robert C; Costley, Ruth A

2014-02-18

359

Temporal changes in microbial ecology and geochemistry in produced water from hydraulically fractured Marcellus shale gas wells.  

PubMed

Microorganisms play several important roles in unconventional gas recovery, from biodegradation of hydrocarbons to souring of wells and corrosion of equipment. During and after the hydraulic fracturing process, microorganisms are subjected to harsh physicochemical conditions within the kilometer-deep hydrocarbon-bearing shale, including high pressures, elevated temperatures, exposure to chemical additives and biocides, and brine-level salinities. A portion of the injected fluid returns to the surface and may be reused in other fracturing operations, a process that can enrich for certain taxa. This study tracked microbial community dynamics using pyrotag sequencing of 16S rRNA genes in water samples from three hydraulically fractured Marcellus shale wells in Pennsylvania, USA over a 328-day period. There was a reduction in microbial richness and diversity after fracturing, with the lowest diversity at 49 days. Thirty-one taxa dominated injected, flowback, and produced water communities, which took on distinct signatures as injected carbon and electron acceptors were attenuated within the shale. The majority (>90%) of the community in flowback and produced fluids was related to halotolerant bacteria associated with fermentation, hydrocarbon oxidation, and sulfur-cycling metabolisms, including heterotrophic genera Halolactibacillus, Vibrio, Marinobacter, Halanaerobium, and Halomonas, and autotrophs belonging to Arcobacter. Sequences related to halotolerant methanogenic genera Methanohalophilus and Methanolobus were detected at low abundance (<2%) in produced waters several months after hydraulic fracturing. Five taxa were strong indicators of later produced fluids. These results provide insight into the temporal trajectory of subsurface microbial communities after "fracking" and have important implications for the enrichment of microbes potentially detrimental to well infrastructure and natural gas fouling during this process. PMID:24803059

Cluff, Maryam A; Hartsock, Angela; MacRae, Jean D; Carter, Kimberly; Mouser, Paula J

2014-06-01

360

Spatial and temporal correlation of water quality parameters of produced waters from devonian-age shale following hydraulic fracturing.  

PubMed

The exponential increase in fossil energy production from Devonian-age shale in the Northeastern United States has highlighted the management challenges for produced waters from hydraulically fractured wells. Confounding these challenges is a scant availability of critical water quality parameters for this wastewater. Chemical analyses of 160 flowback and produced water samples collected from hydraulically fractured Marcellus Shale gas wells in Pennsylvania were correlated with spatial and temporal information to reveal underlying trends. Chloride was used as a reference for the comparison as its concentration varies with time of contact with the shale. Most major cations (i.e., Ca, Mg, Sr) were well-correlated with chloride concentration while barium exhibited strong influence of geographic location (i.e., higher levels in the northeast than in southwest). Comparisons against brines from adjacent formations provide insight into the origin of salinity in produced waters from Marcellus Shale. Major cations exhibited variations that cannot be explained by simple dilution of existing formation brine with the fracturing fluid, especially during the early flowback water production when the composition of the fracturing fluid and solid-liquid interactions influence the quality of the produced water. Water quality analysis in this study may help guide water management strategies for development of unconventional gas resources. PMID:23425120

Barbot, Elise; Vidic, Natasa S; Gregory, Kelvin B; Vidic, Radisav D

2013-03-19

361

Infiltration and hydraulic connections from the Niagara River to a fractured-dolomite aquifer in Niagara Falls, New York  

USGS Publications Warehouse

The spatial distribution of hydrogen and oxygen stable-isotope values in groundwater can be used to distinguish different sources of recharge and to trace groundwater flow directions from recharge boundaries. This method can be particularly useful in fractured-rock settings where multiple lines of evidence are required to delineate preferential flow paths that result from heterogeneity within fracture zones. Flow paths delineated with stable isotopes can be combined with hydraulic data to form a more complete picture of the groundwater flow system. In this study values of ??D and ??18O were used to delineate paths of river-water infiltration into the Lockport Group, a fractured dolomite aquifer, and to compute the percentage of fiver water in groundwater samples from shallow bedrock wells. Flow paths were correlated with areas of high hydraulic diffusivity in the shallow bedrock that were delineated from water-level fluctuations induced by diurnal stage fluctuations in man-made hydraulic structures. Flow paths delineated with the stable-isotope and hydraulic data suggest that fiver infiltration reaches an unlined storm sewer in the bedrock through a drainage system that surrounds aqueducts carrying river water to hydroelectric power plants. This finding is significant because the storm sewer is the discharge point for contaminated groundwater from several chemical waste-disposal sites and the cost of treating the storm sewer's discharge could be reduced if the volume of infiltration from the river were decreased.The spatial distribution of hydrogen and oxygen stable-isotope values in groundwater can be used to distinguish different sources of recharge and to trace groundwater flow directions from recharge boundaries. This method can be particularly useful in fractured-rock settings where multiple lines of evidence are required to delineate preferential flow paths that result from heterogeneity within fracture zones. Flow paths delineated with stable isotopes can be combined with hydraulic data to form a more complete picture of the groundwater flow system. In this study values of ??D and ??18O were used to delineate paths of river-water infiltration into the Lockport Group, a fractured dolomite aquifer, and to compute the percentage of river water in groundwater samples from shallow bedrock wells. Flow paths were correlated with areas of high hydraulic diffusivity in the shallow bedrock that were delineated from water-level fluctuations induced by diurnal stage fluctuations in man-made hydraulic structures. Flow paths delineated with the stable-isotope and hydraulic data suggest that river infiltration reaches an unlined storm sewer in the bedrock through a drainage system that surrounds aqueducts carrying river water to hydroelectric power plants. This finding is significant because the storm sewer is the discharge point for contaminated groundwater from several chemical waste-disposal sites and the cost of treating the storm sewer's discharge could be reduced if the volume of infiltration from the river were decreased.

Yager, R. M.; Kappel, W. M.

1998-01-01

362

Drill Cuttings-based Methodology to Optimize Multi-stage Hydraulic Fracturing in Horizontal Wells and Unconventional Gas Reservoirs  

NASA Astrophysics Data System (ADS)

Horizontal drilling and hydraulic fracturing techniques have become almost mandatory technologies for economic exploitation of unconventional gas reservoirs. Key to commercial success is minimizing the risk while drilling and hydraulic fracturing these wells. Data collection is expensive and as a result this is one of the first casualties during budget cuts. As a result complete data sets in horizontal wells are nearly always scarce. In order to minimize the data scarcity problem, the research addressed throughout this thesis concentrates on using drill cuttings, an inexpensive direct source of information, for developing: 1) A new methodology for multi-stage hydraulic fracturing optimization of horizontal wells without any significant increases in operational costs. 2) A new method for petrophysical evaluation in those wells with limited amount of log information. The methods are explained using drill cuttings from the Nikanassin Group collected in the Deep Basin of the Western Canada Sedimentary Basin (WCSB). Drill cuttings are the main source of information for the proposed methodology in Item 1, which involves the creation of three 'log tracks' containing the following parameters for improving design of hydraulic fracturing jobs: (a) Brittleness Index, (b) Measured Permeability and (c) An Indicator of Natural Fractures. The brittleness index is primarily a function of Poisson's ratio and Young Modulus, parameters that are obtained from drill cuttings and sonic logs formulations. Permeability is measured on drill cuttings in the laboratory. The indication of natural fractures is obtained from direct observations on drill cuttings under the microscope. Drill cuttings are also the main source of information for the new petrophysical evaluation method mentioned above in Item 2 when well logs are not available. This is important particularly in horizontal wells where the amount of log data is almost non-existent in the vast majority of the wells. By combining data from drill cuttings and previously available empirical relationships developed from cores it is possible to estimate water saturations, pore throat apertures, capillary pressures, flow units, porosity (or cementation) exponent m, true formation resistivity Rt, distance to a water table (if present), and to distinguish the contributions of viscous and diffusion-like flow in the tight gas formation. The method further allows the construction of Pickett plots using porosity and permeability obtained from drill cuttings, without previous availability of well logs. The method assumes the existence of intervals at irreducible water saturation, which is the case of the Nikanassin Group throughout the gas column. The new methods mentioned above are not meant to replace the use of detailed and sophisticated evaluation techniques. But the proposed methods provide a valuable and practical aid in those cases where geomechanical and petrophysical information are scarce.

Ortega Mercado, Camilo Ernesto

363

Propagation of a plane-strain hydraulic fracture with a fluid lag: Early-time solution  

Microsoft Academic Search

This paper studies the propagation of a plane-strain fluid-driven fracture with a fluid lag in an elastic solid. The fracture is driven by a constant rate of injection of an incompressible viscous fluid at the fracture inlet. The leak-off of the fracturing fluid into the host solid is considered negligible. The viscous fluid flow is lagging behind an advancing fracture

Dmitry I. Garagash

2006-01-01

364

The geometry of a large-scale nitrogen gas hydraulic fracture formed in Devonian shale: an example of fracture mapping with tiltmeters  

SciTech Connect

Production enhancement of gas from wells draining low-permeability formations such as the Devonian shale series of the eastern U.S. commonly is attempted by use of hydraulic fracturing. The problem of designing such fractures to optimize the resulting yield has underlined the need for a more thorough understanding of the fracture process. To this end, several wells penetrating Devonian shale have been selected for intensive study during the fracturing treatments. The studies involve application of a wide variety of diagnostic technologies capable of supplying information pertinent to establishing the behavior of the fracture during the treatment and the principal factors that influence this behavior. This paper presents the results of applying the tiltmeter technique of fracture mapping to determine geometrical characteristics of the fracture resulting from injection of nitrogen gas into the 335 m (1,100 ft) deep Black No. 1 well, which penetrates the Devonian shale in Knox County, OH. During treatment, which lasted from 16:47 to 17:15 hours (local time) on Oct. 22, 1979, a total of 2.59 X 10/sup 4/ std m (9.68 X 10/sup 3/ scf) of nitrogen gas at a wellhead temperature of 46/sup 0/C (115/sup 0/F) and pressure of 9.0 MPa (1,300 psi) was administered to the well. No proppant was used. The well was offered to the research program by its owners after production had declined from an initial 8.6 X 10/sup 2/ std m/sup 3//d (3.2 X 10/sup 4/ scf ft/D) after drilling in 1975 to essentially zero by the end of 1977. During this period of production, the well was openhole for the entire Devonian shale section and had suffered neither explosive nor hydraulic stimulation treatments. It is not known whether the bulk of production came from the shale matrix or from sets of high-angle natural fractures that intersected the well.

Evans, K.; Kolrhausen, G.

1982-10-01

365

Thermal and Hydraulic Coupled Modeling of Hot Fractured Rock Geothermal Reservoir  

NASA Astrophysics Data System (ADS)

Geothermal energy manifests itself in spectacular fashion in many places on the earth's surface and has been widely recognized as a renewable green energy in the world. Several countries have started the related projects for developing the Hot Dry Rock (HDR) geothermal system which has been renamed as Hot Fractured Rock (HFR) in Australia. Geodynamics Limited is developing a world-class, high-grade geothermal energy resource beneath the Cooper Basin in NE South Australia, where the measured surface heat flow is over 100mW/m2. It is thought to originate from the Big Lake Suite granites that are enriched in the heat-producing elements. The presence of highly radiogenic intrusive within 3-4 km of the surface generates extraordinarily high geothermal gradient regimes (>60ºC km-1, and the region is recognized as one of the hottest spots in the world outside volcanic centres. To help bringing the vision of HFR geothermal energy to reality, a 3D finite element based computational model and software for simulating such a multi-scale highly coupled thermo- hydro-mechanical geo-mechanical system on the parallel supercomputer are being developed based on our long tern and on-going related outcomes. This presentation will focus on the related outcomes on the thermo- hydro coupling module aiming to investigate thermal and fluid flow coupled process and their impact on the Cooper Basin HFR geothermal reservoir. The microseismicity monitoring data measured during the hydraulic stimulation process was used to estimate the related key input parameters for the further numerical investigation of the coupled thermal and fluid flow behaviours of Cooper Basin HFR geothermal reservoir. The above preliminary simulation results demonstrate the stability and usefulness of the algorithm and software.

Xu, H.; Xing, H.; Wyborn, D.; Yin, C.; Mora, P.

2006-12-01

366

Enhancing Seismic Monitoring Capability for Hydraulic Fracturing Induced Seismicity in Canada  

NASA Astrophysics Data System (ADS)

The amount of natural gas produced from unconventional sources, such as the shale gas, has increased dramatically since the last decade. One of the key factors in the success of shale gas production is the application of hydraulic fracturing (also known as "fracking") to facilitate the efficient recovery of natural gas from shale matrices. As the fracking operation becomes routine in all major shale gas fields, its potential to induce local earthquakes at some locations has become a public concern. To address this concern, Natural Resources Canada has initiated a research effort to investigate the potential links between fracking operations and induced seismicity in some major shale gas basins of Canada. This federal-provincial collaborative research aims to assess if shale gas fracking can alter regional pattern of background seismicity and if so, what the relationship between how fracking is conducted and the maximum magnitude of induced seismicity would be. Other objectives include the investigation of the time scale of the interaction between fracking events and induced seismicity and the evaluation of induced seismicity potential for shale gas basins under different tectonic/geological conditions. The first phase of this research is to enhance the detection and monitoring capability for seismicity possibly related to shale gas recovery in Canada. Densification of the Canadian National Seismograph Network (CNSN) is currently underway in northeast British Columbia where fracking operations are taking place. Additional seismic stations are planned for major shale gas basins in other regions where fracking might be likely in the future. All newly established CNSN stations are equipped with broadband seismographs with real-time continuous data transmission. The design goal of the enhanced seismic network is to significantly lower the detection threshold such that the anticipated low-magnitude earthquakes that might be related to fracking operations can be identified and located shortly after their occurrence.

Kao, H.; Cassidy, J. F.; Farahbod, A.; Lamontagne, M.

2012-12-01

367

Analysis of the results of hydraulic-fracture stimulation of two crystalline bedrock boreholes, Grand Portage, Minnesota  

USGS Publications Warehouse

Hydraulic fracture-stimulation procedures typical of those provided by contractors in the water-well industry were applied to two boreholes in basaltic and gabbroic rocks near Grand Portage, Minnesota.These boreholes were considered incapable of supplying adequate ground water for even a single household although geophysical logs showed both boreholes were intersected by many apparently permeable fractures. Tests made before and after stimulation indicated that the two boreholes would produce about 0.05 and 0.25 gallon per minute before stimulation, and about 1.5 and 1.2 gallons per minute after stimulation. These increases would be enough to obtain adequate domestic water supplies from the two boreholes but would not furnish enough water for more than a single household from either borehole. Profiles of high-resolution flow made during pumping after stimulation indicated that the stimulation enhanced previously small inflows or stimulated new inflow from seven fractures or fracture zones in one borehole and from six fractures or fracture zones in the other.Geophysical logs obtained after stimulation showed no specific changes in these 13 fractures that could be related to stimulation other than the increases in flow indicated by the flowmeter logs. The results indicate that the stimulation has increased inflow to the two boreholes by improving the connectivity of favorably orientated fractures with larger scale flow zones in the surrounding rocks. Three of four possible diagnostics related to measured pressure and flow during the stimulation treatments were weakly correlated with the increases in production associated with each treatment interval. These correlations are not statistically significant on the basis of the limited sample of 16 treatment intervals in two boreholes, but the results indicate that significant correlations might be established from a much larger data set.

Paillet, Fredrick L.; Olson, James D.

1994-01-01

368

A follow-up study on extracorporeal fixation of condylar fractures using vertical ramus osteotomy  

PubMed Central

Objectives The aim of this study is to report the results of extracorporeal fixation in patients with mandibular condylar fractures and compare them with the clinical results of conservative treatment. Materials and Methods The medical records of 92 patients (73 male [M] : 19 female [F], age 13-69 years, mean 33.1 years) treated for condylar fractures at the Department of Oral and Maxillofacial Surgery in Sun Dental Hospital (Daejeon, Korea) from 2007 to 2012 were reviewed. Patients were divided into three groups: group A (23 patients; M : F=18 : 5, age 21-69 years, mean 32.6 years), treated with extracorporeal fixation; group B (30 patients; M : F=24 : 6, age 16-57 years, mean 21.1 years), treated by conventional open reduction; and group C (39 patients; M : F=31 : 8, age 16-63 years, mean 34.4 years), treated with the conservative method ('closed' reduction). Clinical and radiographic findings were evaluated and analyzed statistically. Results Occurrence of postoperative condylar resorption correlated with certain locations and types of fracture. In this study, patients in group A (treated with extracorporeal fixation) did not demonstrate significant postoperative complications such as malocclusion, mandibular hypomobility, temporomandibular disorder, or complete resorption of condyle fragments. Conclusion In superiorly located mandibular condyle fractures, exact reconstruction of condylar structure with the conventional open reduction technique can be difficult due to the limited surgical and visual fields. In such cases, extracorporeal fixation of the condyle using vertical ramus osteotomy may be a better choice of treatment because it results in anatomically accurate reconstruction and low risk of complications.

Park, Sung Yong; Im, Jae Hyoung; Yoon, Seong Hoe

2014-01-01

369

Scaling relations and spectral characteristics of tensile microseisms: evidence for opening/closing cracks during hydraulic fracturing  

NASA Astrophysics Data System (ADS)

Using formulae for both tensile and shear sources, we investigate spectral characteristics of microearthquakes induced by hydraulic fracturing, with application to passive-seismic data recorded during a multistage treatment programme in western Canada. For small moment magnitudes (Mw < 0), reliable determination of corner frequency requires accurate knowledge of QP and QS, although spectral estimates of magnitude are relatively unaffected by uncertainty in seismic attenuation. Here, we estimate QP and QS using spectral ratios derived from perforation shots. Of the microseismic events analysed during the hydraulic-fracture treatment, 17 of 20 exhibit an S/P spectral ratio <5, which is consistent with tensile failure. In addition, four microseismic events are characterized by a modulating source spectrum containing quasi-periodic notches. We interpret this spectral character to reflect a complex rupture pattern that involves rapid (5-8 ms) opening and closing of tensile cracks. In general, for tensile rupture on a penny-shaped crack, our model predicts that source radius (a) is related to moment magnitude (Mw) and internal fluid pressure within the fracture (Pi) by a simple empirical scaling relation: log10(a) = [9 - log102]/3 + 0.5Mw - log10(Pi)/3.

Eaton, David W.; van der Baan, Mirko; Birkelo, Brad; Tary, Jean-Baptiste

2014-03-01

370

A numerical study on the correlation between fracture transmissivity, hydraulic aperture and transport aperture  

Microsoft Academic Search

Quantitative evaluation of the groundwater velocity in the fractures is a key part of contaminants transport assessment especially in the radioactive waste disposal programs. In a hydrogeological model such as the discrete fracture network model, the transport aperture of water conducting fracture is one of the important parameters for evaluating groundwater velocity. Tracer tests that measure velocity (or transport aperture)

A. Sawada; A. Takebe; K. Sakamoto

2006-01-01

371

Modeling infiltration into a tuff matrix from a saturated vertical fracture  

SciTech Connect

Saturation profiles resulting from TOUGH2 numerical simulations of water infiltration into a tuff matrix from a saturated vertical fracture have been compared to experimental results. The purpose was to determine the sensitivity of the infiltration on local heterogeneities and different representations of two-phase characteristic curves used by the model. Findings indicate that the use of simplified (linearized) capillary pressure curves with rigorous (van Genuchten) relative permeability curves resulted in a more computationally efficient solution without a loss in accuracy. However, linearized forms of the relative permeability functions produced poor results, regardless of the form of the capillary pressure function. In addition, numerical simulations revealed that the presence of local heterogeneities in the tuff caused non-uniform saturation distributions and wetting fronts in the in matrix.

Ho, C.K.

1993-12-31

372

Vertical variations of soil hydraulic properties within two soil profiles and its relevance for soil water simulations  

NASA Astrophysics Data System (ADS)

Numerical simulations of soil water dynamics can be valuable tools for the assessment of different soil and land management practices. For accurate simulations, the soil hydraulic properties (SHP), i.e. the hydraulic conductivity and water retention function have to be properly known. They can be either estimated from physical soil properties by pedotransfer functions (PTF) or measured. In most studies, soil profiles are analyzed and sampled with respect to their pedogenic horizons. While considerable effort has been put on horizontal spatial SHP variations, vertical changes within soil profiles have not been analyzed in detail. Therefore, the objectives of this study were (i) the SHP measurement along vertical transects within two soil profiles, (ii) to evaluate their spatial variation and correlation with physical soil properties, and (iii) to assess the impact of the SHP determination method and its spatial discretization on simulated soil water balance components. Two soils, an agriculturally used silty-loam Chernozem and a forested sandy Cambisol were sampled in 0.05 m increments along vertical transects. The parameters of a dual porosity model were derived using the evaporation method and scaling was applied to derive representative mean SHP parameters and scaling factors as a measure of spatial variability. State-space models described spatial variations of the scaling factors by physical soil properties. Simulations with HYDRUS 1D delivered the soil water balance for different climatic conditions with the SHP being estimated from horizon-wise PTFs, or discretized either sample-wise, according to the pedogenic horizons, or as hydrologically relevant units (hydropedological approach). Considerable SHP variations were found for both soil profiles. In the Chernozem, variations of the hydraulic conductivity were largest within the ploughed Ap-horizon and could be attributed to variations in soil structure (macropores). In the subsoil, soil water retention showed a gradual decrease within each horizon. The observed water retention variations could be described by state-space models that comprised the contents of clay and total carbon, whereas variations of the hydraulic conductivity were described by clay content and total porosity. The hydraulic conductivity in the Cambisol was slightly undulating throughout the profile. Here, water retention was largest in the upper part of the profile and considerably decreased within the lower part of the Bhs-horizon. Simulated soil water balance components differed distinctly between the SHP discretizations. Compared to observed soil water contents, the simulations where the SHP were given by small-scale layers or hydropedological units performed best for both experimental sites. The different SHP discretizations mainly affected the estimated drainage losses and the simulated crop transpiration under medium to dry climatic conditions. The study confirmed the importance of an adequate spatial SHP discretization. The results indicate that SHP estimations by PTFs or the standard horizon-mean sampling strategy might fail to parameterize soil water simulations, especially in structured soils. The presented hydropedological approach showed a way to receive good simulation results by reducing the SHP observation density.

Schwen, Andreas; Zimmermann, Michael; Bodner, Gernot

2014-08-01

373

Accuracy of the Raypex-4 and Propex apex locators in detecting horizontal and vertical root fractures: an in vitro study.  

PubMed

Unforeseen root fractures during endodontic therapy are often difficult to diagnose and treat. Apex locators have been shown to be accurate in measuring the working lengths of root canals, and it was postulated whether they could also be used to determine the position of root fractures. This study was undertaken to assess the accuracy of two different apex locators in determining the position of fractures. One hundred single rooted teeth were randomly divided into two groups. One group had simulated horizontal fractures cut into them and the other group had vertical fractures. All fractures were detected in both groups using both a Propex (third generation) and a Raypex-4 (fourth generation) apex locator. The actual lengths of the fractures were then measured under 2.5 times magnification, and the results subjected to statistical analysis. Both locators produced similar results and were found to be very accurate, with measurements that correlated closely to the actual lengths. Clinically, treatment options for root fractures vary depending on their location. Thus apex locators may be a valuable aid in not only determining the presence of a root fracture, but also its exact location, which will help the clinician decide on the most appropriate management. PMID:16977952

al Kadi, H; Sykes, L M; Vally, Z

2006-07-01

374

Fracture hydraulic conductivity in the Mexico City clayey aquitard: Field piezometer rising-head tests  

Microsoft Academic Search

A regional lacustrine aquitard covers the main aquifer of the metropolitan area of Mexico City. The aquitard’s hydraulic conductivity (K') is fundamental for evaluating the natural protection of the aquifer against a variety of contaminants present on the surface and its hydraulic response. This study analyzes the distribution and variation of K' in the plains of Chalco, Texcoco and Mexico

Carlos Vargas; Adrián Ortega-Guerrero

2004-01-01

375

Determining sources of elevated salinity in pre-hydraulic fracturing water quality data using a multivariate discriminant analysis model  

NASA Astrophysics Data System (ADS)

Hydraulic fracturing has the potential to introduce saline water into the environment due to migration of deep formation water to shallow aquifers and/or discharge of flowback water to the environment during transport and disposal. It is challenging to definitively identify whether elevated salinity is associated with hydraulic fracturing, in part, due to the real possibility of other anthropogenic sources of salinity in the human-impacted watersheds in which drilling is taking place and some formation water present naturally in shallow groundwater aquifers. We combined new and published chemistry data for private drinking water wells sampled across five southern New York (NY) counties overlying the Marcellus Shale (Broome, Chemung, Chenango, Steuben, and Tioga). Measurements include Cl, Na, Br, I, Ca, Mg, Ba, SO4, and Sr. We compared this baseline groundwater quality data in NY, now under a moratorium on hydraulic fracturing, with published chemistry data for 6 different potential sources of elevated salinity in shallow groundwater, including Appalachian Basin formation water, road salt runoff, septic effluent, landfill leachate, animal waste, and water softeners. A multivariate random number generator was used to create a synthetic, low salinity (< 20 mg/L Cl) groundwater data set (n=1000) based on the statistical properties of the observed low salinity groundwater. The synthetic, low salinity groundwater was then artificially mixed with variable proportions of different potential sources of salinity to explore chemical differences between groundwater impacted by formation water, road salt runoff, septic effluent, landfill leachate, animal waste, and water softeners. We then trained a multivariate, discriminant analysis model on the resulting data set to classify observed high salinity groundwater (> 20 mg/L Cl) as being affected by formation water, road salt, septic effluent, landfill leachate, animal waste, or water softeners. Single elements or pairs of elements (e.g. Cl and Br) were not effective at discriminating between sources of salinity, indicating multivariate methods are needed. The discriminant analysis model classified most accurately samples affected by formation water and landfill leachate, whereas those contaminated by road salt, animal waste, and water softeners were more likely to be discriminated as contaminated by a different source. Using this approach, no shallow groundwater samples from NY appear to be affected by formation water, suggesting the source of salinity pre-hydraulic fracturing is primarily a combination of road salt, septic effluent, landfill leachate, and animal waste.

Lautz, L. K.; Hoke, G. D.; Lu, Z.; Siegel, D. I.

2013-12-01

376

Use of arsenic and REE in black shales as potential environmental tracers in hydraulic fracturing operations  

NASA Astrophysics Data System (ADS)

Black shales commonly targeted for shale gas development were deposited under low oxygen concentrations, and typically contain high As levels. The depositional environment governs its solid-phase association in the sediment, which in turn will influence degree of remobilization during hydraulic fracturing. Organic carbon (OC), trace element (TE) and REE distributions have been used as tracers for assessing deep water redox conditions at the time of deposition in the Midcontinent Sea of North America (Algeo and Heckel, 2008), during large-scale oceanic anoxic events (e.g., Bunte, 2009) and in modern OC-rich sediments underlying coastal upwelling areas (e.g., Brumsack, 2006). We will present REE and As data from a collection of six different locations in the continental US (Kansas, Iowa, Oklahoma, Kentucky, North Dakota and Pennsylvania), ranging in age from Devonian to Upper Pennsylvanian, and from a Cretaceous black shale drilled on the Demerara Rise during ODP Leg 207. We interpret our data in light of the depositional framework previously developed for these locations based on OC and TE patterns, to document the mechanisms leading to REE and As accumulation, and explore their potential use as environmental proxies and their diagenetic remobilization during burial, as part of our future goal to develop a predictive evaluation of arsenic release from shales and transport with flowback waters. Total REE abundance (?REE) ranged from 35 to 420 ppm in an organic rich sample from Stark shale, KS. PAAS-normalized REE concentrations ranged from 0.5 to 7, with the highest enrichments observed in the MREE (Sm to Ho). Neither the ?REE nor the MREE enrichments correlated with OC concentrations or postulated depositional redox conditions, suggesting a principal association with aluminosilicates and selective REE fractionation during diagenesis. In the anoxic reducing environments in which black shales were deposited, sulfide minerals such as FeS2 trap aqueous arsenic in the crystal lattice, but As is also known to bind to the charged surfaces of clay minerals. Our arsenic concentration data show that the highest abundances (up to 70 ppm) are found in sediments with the highest total sulfur concentration (to 2.6 ppm), but there was no clear correlation with organic carbon or aluminosilicate content. We compare our results with preliminary data from a series of flowback waters sampled from ten producing wells in Pennsylvania and from high-pressure high-temperature experimental leaching of Marcellus shale samples.

Yang, J.; Torres, M. E.; Haley, B. A.; McKay, J. L.; Algeo, T. J.; Hakala, A.; Joseph, C.; Edenborn, H. M.

2013-12-01

377

Induced Seismicity in Northeast BC, Canada: Correlation With Operation Parameters of Shale Gas Hydraulic Fracturing  

NASA Astrophysics Data System (ADS)

The Horn River Basin and Montney Basin in northeast BC, Canada, are major shale-gas production areas in North America. The earthquake catalog compiled by the Geological Survey of Canada (GSC) using the Canadian National Seismograph Network (CNSN) data indicates that more than 40 earthquakes, with ML ranging between 2.2 and 3.6, occurred in the Horn River Basin since 2009 when the operation of hydraulic fracturing (HF) for shale gas development expanded significantly. In contrast, the GSC catalog shows no event for years before 2009, even though small-scale HF operations were performed as early as in 2007. In this study, we apply the single-station location and waveform correlation methods on continuous 3-component waveforms recorded at the only seismograph station in the region (Fort Nelson) to establish a comprehensive understanding of the spatiotemporal variation of the regional seismicity since 2002. We were able to locate 24 events during the one-year period between July 2002 and July 2003, with the largest ML being 2.9. This observation demonstrates that background seismicity in the Horn River Basin existed long before HF began. Since 2007, the occurrence of local earthquakes has become more frequent with gradually larger magnitude as the scale of HF in the region expands. An analysis of monthly HF operation parameters and local seismicity reveals a positive correlation between the total volume of injection and the maximum magnitude of local events. While the injection pressure during HF operations has been kept at a relatively constant level, the significant increase of injection volume in 2010 and 2011 coincides with a series of ML>3 events, with the largest being 3.6. The newly established state-of-the-art broadband seismograph stations in the region and the recent decline of HF operations in the Horn River Basin provide a rare opportunity to examine how the regional seismic pattern responds to different HF operation parameters, which in turn may give better insight into the physical mechanisms of induced seismicity.

Kao, H.; Farahbod, A.; Cassidy, J. F.; Walker, D. M.

2013-12-01

378

Seismic monitoring of hydraulic fracturing: techniques for determining fluid flow paths and state of stress away from a wellbore  

SciTech Connect

Hydraulic fracturing has gained in popularity in recent years as a way to determine the orientations and magnitudes of tectonic stresses. By augmenting conventional hydraulic fracturing measurements with detection and mapping of the microearthquakes induced by fracturing, we can supplement and idependently confirm information obtained from conventional analysis. Important information obtained from seismic monitoring includes: the state of stress of the rock, orientation and spacing of the major joint sets, and measurements of rock elastic parameters at locations distant from the wellbore. While conventional well logging operations can provide information about several of these parameters, the zone of interrogation is usually limited to the immediate proximity of the borehole. The seismic waveforms of the microearthquakes contain a wealth of information about the rock in regions that are otherwise inaccessible for study. By reliably locating the hypocenters of many microearthquakes, we have inferred the joint patterns in the rock. We observed that microearthquake locations do not define a simple, thin, planar distribution, that the fault plane solutions are consistent with shear slippage, and that spectral analysis indicates that the source dimensions and slip along the faults are small. Hence we believe that the microearthquakes result from slip along preexisting joints, and not from tensile extension at the tip of the fracture. Orientations of the principal stresses can be estimated by using fault plane solutions of the larger microearthquakes. By using a joint earthquake location scheme, and/or calibrations with downhole detonators, rock velocities and heterogeneities thereof can be investigated in rock volumes that are far enough from the borehole to be representative of intrincis rock properties.

Fehler, M.; House, L.; Kaieda, H.

1986-01-01

379

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

PubMed

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. PMID:22066833

Struchtemeyer, Christopher G; Elshahed, Mostafa S

2012-07-01

380

Fracture hydraulic conductivity in the Mexico City clayey aquitard: Field piezometer rising-head tests  

NASA Astrophysics Data System (ADS)

A regional lacustrine aquitard covers the main aquifer of the metropolitan area of Mexico City. The aquitard's hydraulic conductivity (K') is fundamental for evaluating the natural protection of the aquifer against a variety of contaminants present on the surface and its hydraulic response. This study analyzes the distribution and variation of K' in the plains of Chalco, Texcoco and Mexico City (three of the six former lakes that existed in the Basin of Mexico), on the basis of 225 field-permeability tests, in nests of existing piezometers located at depths of 2-85 m. Tests were interpreted using the Hvorslev method and some by the Bouwer-Rice method. Results indicate that the distribution of K' fits log-Gaussian regression models. Dominant frequencies for K' in the Chalco and Texcoco plains range between 1E-09 and 1E-08 m/s, with similar population means of 1.19E-09 and 1.7E-09 m/s, respectively, which are one to two orders of magnitude higher than the matrix conductivity. In the Mexico City Plain the population mean is near by one order of magnitude lower; K'=2.6E-10 m/s. The contrast between the measured K' and that of the matrix is attributed to the presence of fractures in the upper 25-40 m, which is consistent with the findings of previous studies on solute migration in the aquitard. Un imperméable régional d'origine lacustre recouvre le principal aquifère de la zone urbaine de la ville de Mexico. La conductivité hydraulique K' de cet imperméable est fondamentale pour évaluer la protection naturelle de l'aquifère, contre les différents contaminants présents en surface, et sa réponse hydraulique. Cette étude analyse et les variations de K' dans les plaines de Chalco, Texcoco et Mexico (trois des six anciens lacs qui existaient dans le Bassin de Mexico), sur la base de 225 essais de perméabilité sur le terrain, réalisés en grappes dans des piézomètres existants entre 2 et 85 m de profondeur. Les essais ont été interprétés avec la méthode de Hvorslev et certains avec la méthode de Bouwer-Rice. Les résultats indiquent que la distribution de K' s'ajuste à des modèles de régression log-gaussiens. Les valeurs de K' les plus fréquentes dans les plaines de Chalco et de Texcoco sont entre 1E-09 et 1E-08 m/s, avec des moyennes similaires de 1.19E-09 et 1.7E-09 m/s respectivement, qui sont d'un ou deux ordres de grandeurs supérieures à la conductivité de la matrice. Dans la plaine de Mexico, la moyenne est proche d'un ordre de grandeur en moins, avec 2.6E-10 m/s. Ce contraste entre le K' mesuré et celui de la matrice est attribué à la présence de fractures dans les 25-40 m supérieurs, ce qui est en accord avec les études précédentes sur la migration de solutés au travers de l'imperméable. El acuífero principal del Área Metropolitana de la Ciudad de México está recubierto por un acuitardo regional lacustre, cuya conductividad hidráulica es fundamental para evaluar la protección natural de las aguas subterráneas contra los contaminantes presentes en superficie y su respuesta hidráulica. Este estudio analiza la distribución y variación de dicha conductividad en las llanuras de Chalco, Texcoco y Ciudad de México (tres de los seis lagos que existían al principio en la Cuenca de México) a partir de 225 ensayos de campo en piezómetros múltiples existentes, ubicados entre 2 y 85 m de profundidad. La interpretación de los ensayos se ha realizado mediante el método de Hvorslev y-algunos-el de Bouwer-Rice. Los resultados indican que la distribución de la conductividad se ajusta a modelos de regresión lognormales. Las frecuencias dominantes en las Llanuras de Chalco y Texoco están comprendidas entre 1-9 y 10-8 m/s, con medias de población similares de 1.19×10-9 y 1.70×10-9 m/s, respectivamente, que son dos órdenes de magnitud mayores que el valor de la matriz. En el Llano de México, la media es casi un orden de magnitud inferior (2.60×10-10 m/s). Se atribuye este contraste entre la conductividad hidráulica medida y la de la matriz a la presencia de fracturas en el tramo s

Vargas, Carlos; Ortega-Guerrero, Adrián

381

Extended analysis of constant-height hydraulic fractures for the estimation of in-situ crack-opening modulus from bottomhole pressure records  

SciTech Connect

Hydraulic fractures created in oil and gas bearing rock formations can be made to propagate for a limited time at approximately constant height if favorable stress, deformation modulus or fracture toughness barriers to height growth exist and if the fracture design is suitably optimized to exploit these favorable conditions and reduce height growth. In this report, a unified theoretical formulation for the Perkins-Kern-Nordgren (PKN) and Christianovitch-Geertsma-De Klerk-Daneshy (CGDD) constant height fracture models is first presented. For a fracture fluid injection rate that varies as an arbitrary power of time, growth laws for fracturing fluid pressure, fracture width, and flow rate are rigorously derived for PKN and CGDD types of fractures. These similarity solutions account for non-Newtonian power-law fluid flow, transient fluid storage and generalized power-law fluid leak-off to the rock formation. They include and extend the results currently available in the literature for PKN and CGDD fractures. The results for PKN and CGDD fractures are then generalized to obtain an approximate hybrid CGDD-PKN fracture model that can be applied to constant height fractures of arbitrary length/height aspect ratio and arbitrary cross-sectional shape. Characteristic times for fracture extension are identified and estimates are given for the transition times when the fracture evolves from a CGDD-type fracture at small aspect ratio to a PKN-type fracture at large aspect ratio. These results are useful for interpreting fracturing data and for designing fractures for crack-opening modulus measurements.

Wijesinghe, A.M.

1987-03-01

382

40 CFR 147.52 - State-administered program-Hydraulic Fracturing of Coal Beds.  

Code of Federal Regulations, 2010 CFR

...Water/Drinking Water Branch, Ground Water & UIC Section, Sam Nunn Atlanta Federal Center, 61 Forsyth Street, S.W., Room15-T53...Alabama Class II Underground injection Control Program. (d) The Program Description for the Regulation of Hydraulic...

2010-07-01

383

Contrasting groundwater quality in areas with and without gas production by hydraulic fracturing near the PA/NY border  

NASA Astrophysics Data System (ADS)

Shale gas development, including drilling and hydraulic fracturing, is rapidly increasing throughout the United States and, indeed, the rest of the world. Systematic surveys of water quality both pre- and post drilling/production are sparse. To examine the impacts of shale gas production on water quality, pilot studies are being conducted in adjacent counties of western NY (Chemung, Tioga, Broome, and Delaware) and northern PA (Bradford, Susquehanna, and Tioga). These 7 counties along the border of NY and PA share similar geology and demographic compositions and have been identified as a key area to develop shale gas with the key difference that active fracking is occurring in PA but there is no fracking yet in NY due to the current moratorium in that state. Measurements include a suite of volatile organic compounds (VOCs), major and trace elements, methane and its stable isotopes, noble gases and tritium for dating purposes, and the primary radioactive elements of potential concern, radon and radium. We found elevated methane levels on both sides of the border, and some wells show elemental fingerprints characteristic for shale fluids. Field observations at several wells near drill sites in PA suggested elevated levels of organics, possibly from hydraulic fracturing activities. The full suite of lab analyses is currently ongoing and can be used to further characterize sources of these organics.

Stute, M.; Yan, B.; Ross, J. M.; Chillrud, S. N.; Saberi, P.; Panettieri, R. A.

2013-12-01

384

Fracture prediction in hydraulic bulging of AISI 304 austenitic steel sheets based on a modified ductile fracture criterion  

Microsoft Academic Search

The demand for weight reduction in modern vehicle construction has resulted in an increase in the application of hydroforming processes for the manufacture of automotive lightweight components. This trend led to the research of evaluation on formability of the sheet or tube hydroforming to be noted, particularly the prediction of fracture. In this study, a new proposed approach based on

Y. Xu; H. W. Song; S. H. Zhang; M. Cheng

2011-01-01

385

Impact of coating development on the hydraulic and transport properties in argillaceous limestone fracture  

NASA Astrophysics Data System (ADS)

Results are reported for an acidic water flow-through experiment conducted in a fractured argillaceous limestone sample (73% carbonates). The change in fracture geometry and related parameters is reported for six data sets obtained from synchrotron X-ray microtomography experiments. High-resolution three-dimensional images of the sample allowed quantification of the changes in fracture morphology at a spatial resolution of 6 ?m. Mineral mass loss and permeability changes in the sample were also determined. Several physico-chemical phenomena were identified during the experiment. Initial smooth fracture surfaces evolved rapidly toward rough surfaces with uneven clay coverage due to the preferential dissolution of carbonate minerals compared to clay minerals whose dissolution rate is about 106 slower. A microporous clay coating progressively developed at the fluid-rock interface during heterogeneous dissolution of the fracture, while the global dissolution rate of the fracture walls exponentially decreased. The increase in surface roughness and the presumed reorganization of clays caused a progressive reduction in permeability. During the last flow-through stage, a large decrease in sample permeability was attributed to the large removal of clay particles; this process was responsible for a dramatic collapse of the fracture walls near the sample inlet and led to the development of preferential flow pathways. The development of the clay coating also acted as a barrier to flow and mass transfer between calcite grains and bulk solution and affected transport processes within the fracture.

Noiriel, Catherine; Madé, Benoã®T.; Gouze, Philippe

2007-09-01

386

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)

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.

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

2013-12-01

387

The relationship of root canal enlargement to finger-spreader induced vertical root fracture.  

PubMed

The purpose of this study was to assess the effect of lateral condensation forces on the development of vertical root fracture (VRF) in teeth that have undergone controlled, measured internal root reduction (i.e. canal preparation). Thirty-four straight-rooted maxillary anterior teeth were used. For each tooth a simulated PDL was fabricated from a uniform 0.15 mm layer of silicone impression material. The teeth were mounted in resin to facilitate removal for observation. They were radiographed and measured at 2, 4, 6, and 8 mm from the apex. They were prepared with the step-back method so that the canal width was 20% of the total root width at 2, 4, 6, and 8 mm from the apex. They were obturated using a fine finger spreader attached to a jig that produced a static force o