Science.gov

Sample records for vertical hydraulic fracture

  1. Pressure Responses of a Vertically Hydraulic Fractured Well in a Reservoir with Fractal Structure

    E-print Network

    Razminia, Kambiz; Torres, Delfim F M

    2015-01-01

    We obtain an analytical solution for the pressure-transient behavior of a vertically hydraulic fractured well in a heterogeneous reservoir. The heterogeneity of the reservoir is modeled by using the concept of fractal geometry. Such reservoirs are called fractal reservoirs. According to the theory of fractional calculus, a temporal fractional derivative is applied to incorporate the memory properties of the fractal reservoir. The effect of different parameters on the computed wellbore pressure is fully investigated by various synthetic examples.

  2. Hydraulic fracture design optimization

    SciTech Connect

    Lee, Tae-Soo; Advani, S.H.

    1992-01-01

    This research and development investigation, sponsored by US DOE and the oil and gas industry, extends previously developed hydraulic fracture geometry models and applied energy related characteristic time concepts towards the optimal design and control of hydraulic fracture geometries. The primary objective of this program is to develop rational criteria, by examining the associated energy rate components during the hydraulic fracture evolution, for the formulation of stimulation treatment design along with real-time fracture configuration interpretation and control.

  3. Hydraulic fracture design optimization

    SciTech Connect

    Lee, Tae-Soo; Advani, S.H.

    1992-06-01

    This research and development investigation, sponsored by US DOE and the oil and gas industry, extends previously developed hydraulic fracture geometry models and applied energy related characteristic time concepts towards the optimal design and control of hydraulic fracture geometries. The primary objective of this program is to develop rational criteria, by examining the associated energy rate components during the hydraulic fracture evolution, for the formulation of stimulation treatment design along with real-time fracture configuration interpretation and control.

  4. Geomechanics of hydraulic fracturing microseismicity

    E-print Network

    Ze'ev, Reches

    Geomechanics of hydraulic fracturing microseismicity: Part 1. Shear, hybrid, and tensile events of hydraulic- fracturing-induced microseismicity. Microseismic events are commonly used to discern stimulation patterns and hydraulic fracture evolution; however, techniques beyond fracture mapping are required

  5. Hydraulic Fracturing Sand

    USGS Multimedia Gallery

    Fine-grained silica sand is mixed with chemicals and water before being pumped into rock formations to prevent the newly created artificial fractures from closing after hydraulic fracturing is completed....

  6. Geomechanics of hydraulic fracturing microseismicity

    E-print Network

    Ze'ev, Reches

    Geomechanics of hydraulic fracturing microseismicity: Part 2. Stress state determination Seth Busetti and Ze'ev Reches ABSTRACT We investigate the hydraulic fracturing process by analysis, stress shadowing adjacent to large parent hydraulic fractures, and crack tip stress perturbations. Data

  7. The Influence of Vertical Location on Hydraulic Fracture Conductivity in the Fayetteville Shale 

    E-print Network

    Briggs, Kathryn

    2014-05-05

    proppant experiments were run on samples from both zones. Parameters that were controllable, such as proppant size, concentration and type, were kept consistent between the two zones. In addition to comparing experimental fracture conductivity results...

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

    NASA Astrophysics Data System (ADS)

    Hubble, David Wallace

    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 vertical fracture from a slot cut through the injection-well casing at a selected depth and orientation. Granular iron is suspended in a viscous fluid using a biodegradable guar polymer and pumped through the slot to form a thin vertical sheet. Two PRBs were emplaced 6 m apart and perpendicular to the groundwater flow direction with mid-depths of about 30 m below the ground surface. Due to the depth, all of the emplacement and verification methods used down-hole tools. Resistivity imaging used salt added to the guar as an electrical tracer to map the spread of the VHFI fluid for propagation control and to estimate the extent of the completed PRB. Radar tomography before and after emplacement also provided images of the PRBs and hydraulic pulse testing and electromagnetic logging provided additional data. One PRB consisted of 40 tonnes of granular iron and was estimated to be an average of 80 mm thick. Based on geophysical imaging, the 100% iron PRB was 15 m long and extended from about 24.5 to 35.5 m depth. The second PRB consisted of a mixture of 5.6 tonnes of well sand and 4.4 tonnes of iron, but was only partially completed. Based on imaging, the sand/iron PRB comprised an area 9 m long extending from about 27 to 34.5 m below the ground surface. The proximity of screened wells, which deviated significantly from vertical toward the PRB alignment, resulted in loss of VHFI control. A sub-horizontal layer of iron formed between the 100% iron PRB and several of the wells. Similarly, piping failure zones formed between the sand/iron PRB and two geophysical wells. Selected groundwater constituents were monitored up- and down-gradient of the two PRBs for 11 months before the PRB emplacement and for 48 months afterwards. Temporary elevated levels of sodium, chloride, and conductance (from the salt tracer), total organic carbon (from the guar) and lowered DO were observed down-gradient of the PRBs. Although the various verification methods confirmed the presence of the 100% iron PRB and its overall continuity, the groundwater data showed no evidence of flow through the granular iron (PCE degradation, elevated pH, dissolved oxygen removal and reducing conditions). This suggests that the groundwater flows around the 100% iron PRB. It is possible that the guar used for the VHFI remained cross-linked, creating a low-permeability barrier. In contrast, the partially completed sand/iron wall did affect the groundwater chemistry in several down-gradient wells. Reducing conditions, zero DO, high pH, and high levels of dissolved iron were noted. A reduction in PCE concentrations and formation of degradation products were observed. (Abstract shortened by UMI.)

  9. Effect of Natural Fractures on Hydraulic Fracturing

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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.

  10. Simulation of Hydraulic Fractures and their Interactions with Natural Fractures 

    E-print Network

    Sesetty, Varahanaresh

    2012-10-19

    Modeling the stimulated reservoir volume during hydraulic fracturing is important to geothermal and petroleum reservoir stimulation. The interaction between a hydraulic fracture and pre-existing natural fractures exerts significant control...

  11. Selective perceptions of hydraulic fracturing.

    PubMed

    Sarge, Melanie A; VanDyke, Matthew S; King, Andy J; White, Shawna R

    2015-01-01

    Hydraulic fracturing (HF) is a focal topic in discussions about domestic energy production, yet the American public is largely unfamiliar and undecided about the practice. This study sheds light on how individuals may come to understand hydraulic fracturing as this unconventional production technology becomes more prominent in the United States. For the study, a thorough search of HF photographs was performed, and a systematic evaluation of 40 images using an online experimental design involving N = 250 participants was conducted. Key indicators of hydraulic fracturing support and beliefs were identified. Participants showed diversity in their support for the practice, with 47 percent expressing low support, 22 percent high support, and 31 percent undecided. Support for HF was positively associated with beliefs that hydraulic fracturing is primarily an economic issue and negatively associated with beliefs that it is an environmental issue. Level of support was also investigated as a perceptual filter that facilitates biased issue perceptions and affective evaluations of economic benefit and environmental cost frames presented in visual content of hydraulic fracturing. Results suggested an interactive relationship between visual framing and level of support, pointing to a substantial barrier to common understanding about the issue that strategic communicators should consider. PMID:26399946

  12. Method for directional hydraulic fracturing

    DOEpatents

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

    1994-01-01

    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.

  13. Gravity-Driven Hydraulic Fractures

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    This study is motived by a new method for disposing of nuclear waste by injecting it as a dense slurry into a hydraulic fracture that grows downward to great enough depth to permanently isolate the waste. Disposing of nuclear waste using gravity-driven hydraulic fractures is mechanically similar to the upward growth of dikes filled with low density magma. A fundamental question in both applications is how the injected fluid controls the propagation dynamics and fracture geometry (depth and breadth) in three dimensions. Analog experiments in gelatin [e.g., Heimpel and Olson, 1994; Taisne and Tait, 2009] show that fracture breadth (the short horizontal dimension) remains nearly stationary when the process in the fracture "head" (where breadth is controlled) is dominated by solid toughness, whereas viscous fluid dissipation is dominant in the fracture tail. We model propagation of the resulting gravity-driven (buoyant or sinking), finger-like fracture of stationary breadth with slowly varying opening along the crack length. The elastic response to fluid loading in a horizontal cross-section is local and can be treated similar to the classical Perkins-Kern-Nordgren (PKN) model of hydraulic fracturing. The propagation condition for a finger-like crack is based on balancing the global energy release rate due to a unit crack extension with the rock fracture toughness. It allows us to relate the net fluid pressure at the tip to the fracture breadth and rock toughness. Unlike the PKN fracture, where breadth is known a priori, the final breadth of a finger-like fracture is a result of processes in the fracture head. Because the head is much more open than the tail, viscous pressure drop in the head can be neglected leading to a 3D analog of Weertman's hydrostatic pulse. This requires relaxing the local elasticity assumption of the PKN model in the fracture head. As a result, we resolve the breadth, and then match the viscosity-dominated tail with the 3-D, toughness-dominated head to obtain a complete closed-form solution. We then analyze the gravity fracture propagation in conditions of either continuous injection or finite volume release for sets of parameters representative of dense waste injection technique and low viscosity magma diking.

  14. Observations of Fractures Induced by Hydraulic Fracturing in Anisotropic Granite

    NASA Astrophysics Data System (ADS)

    Chen, Youqing; Nagaya, Yuya; Ishida, Tsuyoshi

    2015-07-01

    To investigate how the viscosity of the fracturing fluid affects fracture propagation, hydraulic fracturing experiments using three fluids with different viscosities (supercritical CO2, water, and viscous oil) under the true tri-axial condition were conducted on anisotropic granite specimens, and then the induced fractures were microscopically observed via a fluorescent method. Fractures induced by hydraulic fracturing are considerably tortuous from a microscopic view. A higher viscosity creates a smoother fracture pattern. The tortuosity, which is defined as the total fracture length along a pathway divided by the direct length of the two ends of a fracture, ranges from 1.05 to 1.13, demonstrating that the viscosity of fracturing fluid influences the fracture propagation pattern due to the different pathways of fracture propagation. In addition, hydraulic fracturing can induce many derivative pathways around the main fracture. Hydraulic fracturing with a lower viscosity fluid forms a more complex fracture network in rocks; the fracture induced by supercritical CO2 has the most branches along the main fracture. From these observations, fracture propagation by hydraulic fracturing sometimes develops by the shear fracture mode. This shear fracturing is often observed for a low-viscosity supercritical CO2 injection, which agrees with our results from AE monitoring and waveform analysis.

  15. Identifying Best Practices in Hydraulic Fracturing Using

    E-print Network

    Mohaghegh, Shahab

    Identifying Best Practices in Hydraulic Fracturing Using Virtual Intelligence Techniques SPE 72385 Results & Discussion Conclusion #12;SPE 72385 OBJECTIVE To identify Best Practices in Hydraulic Fracturing, are fractured upon completion to provide economic amounts of gas. #12;SPE 72385 BACKGROUND A dataset

  16. Acoustic Character Of Hydraulic Fractures In Granite

    E-print Network

    Paillet, Frederick I.

    1983-01-01

    Hydraulic fractures in homogeneous granitic rocks were logged with conventional acoustic-transit-time, acoustic-waveform, and acoustic-televiewer logging systems. Fractured intervals ranged in depth from 45 to 570m. and ...

  17. Hydraulic fracture during epithelial stretching

    PubMed Central

    Casares, Laura; Vincent, Romaric; Zalvidea, Dobryna; Campillo, Noelia; Navajas, Daniel; Arroyo, Marino; Trepat, Xavier

    2015-01-01

    The origin of fracture in epithelial cell sheets subject to stretch is commonly attributed to excess tension in the cells’ cytoskeleton, in the plasma membrane, or in cell-cell contacts. Here we demonstrate that for a variety of synthetic and physiological hydrogel substrates the formation of epithelial cracks is caused by tissue stretching independently of epithelial tension. We show that the origin of the cracks is hydraulic; they result from a transient pressure build-up in the substrate during stretch and compression maneuvers. After pressure equilibration cracks heal readily through actomyosin-dependent mechanisms. The observed phenomenology is captured by the theory of poroelasticity, which predicts the size and healing dynamics of epithelial cracks as a function of the stiffness, geometry and composition of the hydrogel substrate. Our findings demonstrate that epithelial integrity is determined in a tension-independent manner by the coupling between tissue stretching and matrix hydraulics. PMID:25664452

  18. A Numerical Investigation of Fault Slip Triggered by Hydraulic Fracturing

    E-print Network

    Chapter 23 A Numerical Investigation of Fault Slip Triggered by Hydraulic Fracturing Neda Zangeneh during hydraulic fracturing operations, together with the induced seismicity, and corresponding to investigate the relationship between hydraulic fracturing (i.e. fluid injection) and the response

  19. Gas condensate damage in hydraulically fractured wells 

    E-print Network

    Reza, Rostami Ravari

    2004-11-15

    than the zero-fracture-face-skin optimum, in some cases considerably large, or to put it differently, for every flowing bottomhole pressure there exists an optimum fracture geometry that maximize the dimensionless productivity index. They also showed... above and below the dewpoint pressure by about three times as compared to the non-fractured wells. Hydraulic fractures are also found to extend cumulative production above the dew point pressure. As dimensionless fracture conductivity increases...

  20. Acoustic-emission monitoring during hydraulic fracturing

    SciTech Connect

    Stewart, L. ); Cassell, B.R. ); Bol, G.M. )

    1992-06-01

    This paper reports that microseismic events or acoustic emissions associated with hydraulic fracturing are recorded with a borehole seismic tool in a deviated well during multirate injection, shut-in, and flowback. The event locations indicate that fracture orientation, length, and height are compatible with regional stress directions and estimates of the fracture size that are based on pressure decline.

  1. 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...

  2. Hydraulic Fracturing and the Environment

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  3. Gas condensate damage in hydraulically fractured wells 

    E-print Network

    Adeyeye, Adedeji Ayoola

    2004-09-30

    Company. The well was producing a gas condensate reservoir and questions were raised about how much drop in flowing bottomhole pressure below dewpoint would be appropriate. Condensate damage in the hydraulic fracture was expected to be of significant...

  4. Geomechanical review of hydraulic fracturing technology

    E-print Network

    Arop, Julius Bankong

    2013-01-01

    Hydraulic fracturing as a method for recovering unconventional shale gas has been around for several decades. Significant research and improvement in field methods have been documented in literature on the subject. The ...

  5. Interaction between Injection Points during Hydraulic Fracturing

    E-print Network

    Hals, Kjetil M D

    2012-01-01

    We present a model of the hydraulic fracturing of heterogeneous poroelastic media. The formalism is an effective continuum model that captures the coupled dynamics of the fluid pressure and the fractured rock matrix and models both the tensile and shear failure of the rock. As an application of the formalism, we study the geomechanical stress interaction between two injection points during hydraulic fracturing (hydrofracking) and how this interaction influences the fracturing process. For injection points that are separated by less than a critical correlation length, we find that the fracturing process around each point is strongly correlated with the position of the neighboring point. The magnitude of the correlation length depends on the degree of heterogeneity of the rock and is on the order of 30-45 m for rocks with low permeabilities. In the strongly correlated regime, we predict a novel effective fracture-force that attracts the fractures toward the neighboring injection point.

  6. Self-potential observations during hydraulic fracturing

    SciTech Connect

    Moore, Jeffrey R.; Glaser, Steven D.

    2007-09-13

    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 MPa, the magnitude of the Cc increases by 80% in an exponential trend. 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. Resistivity measurements reveal a decrease of 2% prior to hydraulic fracturing and a decrease of {approx}35% after fracturing. An asymmetric spatial SP response created by injectate diffusion into dilatant zones is observed prior to hydraulic fracturing, and in most cases this SP variation revealed the impending crack geometry seconds before failure. At rupture, injectate rushes into the new fracture area where the zeta potential is different than in the rock porosity, and an anomalous SP spike is observed. After fracturing, the spatial SP distribution reveals the direction of fracture propagation. Finally, during tensile cracking in a point load device with no water flow, a SP spike is observed that is caused 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.

  7. Investigation of Possible Wellbore Cement Failures During Hydraulic Fracturing Operations

    SciTech Connect

    Kim, Jihoon; Moridis, George

    2014-11-01

    We model and assess the possibility of shear failure, using the Mohr-Coulomb model ? along the vertical well by employing a rigorous coupled flow-geomechanic analysis. To this end, we vary the values of cohesion between the well casing and the surrounding cement to representing different quality levels of the cementing operation (low cohesion corresponds to low-quality cement and/or incomplete cementing). The simulation results show that there is very little fracturing when the cement is of high quality.. Conversely, incomplete cementing and/or weak cement can causes significant shear failure and the evolution of long fractures/cracks along the vertical well. Specifically, low cohesion between the well and cemented areas can cause significant shear failure along the well, but the same cohesion as the cemented zone does not cause shear failure. When the hydraulic fracturing pressure is high, low cohesion of the cement can causes fast propagation of shear failure and of the resulting fracture/crack, but a high-quality cement with no weak zones exhibits limited shear failure that is concentrated near the bottom of the vertical part of the well. Thus, high-quality cement and complete cementing along the vertical well appears to be the strongest protection against shear failure of the wellbore cement and, consequently, against contamination hazards to drinking water aquifers during hydraulic fracturing operations.

  8. Hydraulic Fracturing Mineback Experiment in Complex Media

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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.

  9. Universal asymptotic umbrella for hydraulic fracture modeling

    E-print Network

    Linkov, Aleksandr M

    2014-01-01

    The paper presents universal asymptotic solution needed for efficient modeling of hydraulic fractures. We show that when neglecting the lag, there is universal asymptotic equation for the near-front opening. It appears that apart from the mechanical properties of fluid and rock, the asymptotic opening depends merely on the local speed of fracture propagation. This implies that, on one hand, the global problem is ill-posed, when trying to solve it as a boundary value problem under a fixed position of the front. On the other hand, when properly used, the universal asymptotics drastically facilitates solving hydraulic fracture problems (both analytically and numerically). We derive simple universal asymptotics and comment on their employment for efficient numerical simulation of hydraulic fractures, in particular, by well-established Level Set and Fast Marching Methods.

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

    SciTech Connect

    Laue, M.L.

    1999-11-01

    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.

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

    SciTech Connect

    Mike L. Laue

    1998-05-29

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

  12. Hydraulic fracturing water use variability in the United States and potential environmental implications

    NASA Astrophysics Data System (ADS)

    Gallegos, Tanya J.; Varela, Brian A.; Haines, Seth S.; Engle, Mark A.

    2015-07-01

    Until now, up-to-date, comprehensive, spatial, national-scale data on hydraulic fracturing water volumes have been lacking. Water volumes used (injected) to hydraulically fracture over 263,859 oil and gas wells drilled between 2000 and 2014 were compiled and used to create the first U.S. map of hydraulic fracturing water use. Although median annual volumes of 15,275 m3 and 19,425 m3 of water per well was used to hydraulically fracture individual horizontal oil and gas wells, respectively, in 2014, about 42% of wells were actually either vertical or directional, which required less than 2600 m3 water per well. The highest average hydraulic fracturing water usage (10,000-36,620 m3 per well) in watersheds across the United States generally correlated with shale-gas areas (versus coalbed methane, tight oil, or tight gas) where the greatest proportion of hydraulically fractured wells were horizontally drilled, reflecting that the natural reservoir properties influence water use. This analysis also demonstrates that many oil and gas resources within a given basin are developed using a mix of horizontal, vertical, and some directional wells, explaining why large volume hydraulic fracturing water usage is not widespread. This spatial variability in hydraulic fracturing water use relates to the potential for environmental impacts such as water availability, water quality, wastewater disposal, and possible wastewater injection-induced earthquakes.

  13. Effectiveness of microseismic monitoring for optimizing hydraulic fracturing in California

    E-print Network

    Alampi, Ann M

    2014-01-01

    Hydraulic fracturing has fundamentally changed the oil and gas industry in the past 10 years. Bakersfield, California provides a unique case study because steam injection, a type of hydraulic fracturing, has been used there ...

  14. Water Withdrawals for Hydraulic Fracturing (Updated May 7, 2014)

    E-print Network

    Walter, M.Todd

    Water Withdrawals for Hydraulic Fracturing (Updated May 7, 2014) Hydraulic require millions of gallons of water. In Pennsylvania, for example, hydraulic gallons of water over a 2 to 5 day period (SRBC). Natural gas industry

  15. Modeling Turbulent Hydraulic Fracture Near a Free Surface

    E-print Network

    Modeling Turbulent Hydraulic Fracture Near a Free Surface Victor C. Tsai Seismological Laboratory consider a hydraulic fracture problem in which the crack grows parallel to a free surface, subject to fully components. wall Wall shear stress. ^· Non-dimensionalized ·. 1 Introduction Hydraulic fracture has been

  16. HYDRAULIC STIMULATION OF NATURAL FRACTURES AS REVEALED BY INDUCED MICROEARTHQUAKES,

    E-print Network

    -1- HYDRAULIC STIMULATION OF NATURAL FRACTURES AS REVEALED BY INDUCED MICROEARTHQUAKES, CARTHAGE, December, 2001 Manuscript # 01066 LAUR# 01-1204 #12;Hydraulic Stimulation of Natural Fractures -2- ABSTRACT We have produced a high-resolution microseismic image of a hydraulic fracture stimulation

  17. Monitoring hydraulic fracturing with seismic emission volume

    NASA Astrophysics Data System (ADS)

    Niu, F.; Tang, Y.; Chen, H.; TAO, K.; Levander, A.

    2014-12-01

    Recent developments in horizontal drilling and hydraulic fracturing have made it possible to access the reservoirs that are not available for massive production in the past. Hydraulic fracturing is designed to enhance rock permeability and reservoir drainage through the creation of fracture networks. Microseismic monitoring has been proven to be an effective and valuable technology to image hydraulic fracture geometry. Based on data acquisition, seismic monitoring techniques have been divided into two categories: downhole and surface monitoring. Surface monitoring is challenging because of the extremely low signal-to-noise ratio of the raw data. We applied the techniques used in earthquake seismology and developed an integrated monitoring system for mapping hydraulic fractures. The system consists of 20 to 30 state-of-the-art broadband seismographs, which are generally about hundreds times more sensible than regular geophones. We have conducted two experiments in two basins with very different geology and formation mechanism in China. In each case, we observed clear microseismic events, which may correspond to the induced seismicity directly associated with fracturing and the triggered ones at pre-existing faults. However, the magnitude of these events is generally larger than magnitude -1, approximately one to two magnitudes larger than those detected by downhole instruments. Spectrum-frequency analysis of the continuous surface recordings indicated high seismic energy associated with injection stages. The seismic energy can be back-projected to a volume that surrounds each injection stage. Imaging seismic emission volume (SEV) appears to be an effective way to map the stimulated reservior volume, as well as natural fractures.

  18. Investigation of Created Fracture Geometry through Hydraulic Fracture Treatment Analysis 

    E-print Network

    Ahmed, Ibraheem 1987-

    2012-11-30

    -1 INVESTIGATION OF CREATED FRACTURE GEOMETRY THROUGH HYDRAULIC FRACTURE TREATMENT ANALYSIS A Thesis by IBRAHEEM ANWER AHMED Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE Approved by: Chair of Committee, Christine Ehlig-Economides Committee Members, Peter Valko Yuefeng Sun Head of Department, Alfred Daniel Hill December 2012 Major Subject: Petroleum Engineering Copyright 2012 Ibraheem...

  19. Linking earthquakes and hydraulic fracturing operations

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2013-01-01

    Hydraulic fracturing, also known as fracking, to extract oil and gas from rock, has been a controversial but increasingly common practice; some studies have linked it to groundwater contamination and induced earthquakes. Scientists discussed several studies on the connection between fracking and earthquakes at the AGU Fall Meeting in San Francisco in December.

  20. In situ stress estimates from hydraulic fracturing and direct observation of crack orientation

    NASA Astrophysics Data System (ADS)

    Warren, William E.; Smith, Carl W.

    1985-07-01

    Estimates of in situ stress in G Tunnel, Rainier Mesa, Nevada Test Site, have been obtained with hydraulic fracturing techniques. This work represents a nontraditional use of hydraulic fracturing in that it was performed primarily in horizontal boreholes drilled into the formation from access drifts tunneled into the mesa rather than the usual operation performed at depth in vertical boreholes drilled from the surface. Several operations were performed in essentially orthogonal triads of boreholes located at a point. A significant feature of this work is the mineback operation in which the borehole is mined out to reveal the actual fracture. During the hydraulic fracturing operation, colored dye was added to the fracturing fluid which left an easily detectable stain on the fracture surface. Direct observation of the fracture orientation away from the borehole establishes the direction of the minimum compressive in situ stress and the plane of the other two principal stresses. In one borehole, which was not aligned along a principal stress direction, a modified mineback operation revealed a fracture plane that twisted as it grew away from the borehole, aligning itself finally in a plane determined by the in situ stresses. This twisting is consistent with theoretical predictions of borehole stresses under these conditions. This same mineback also showed that fracture of the formation initiated at or under one of the packers, indicating that the packers may have an effet on in situ stress estimates. General observations of over 100 tests performed in G Tunnel show that under the sloping portion of the mesa, fracture planes are not vertical but dip in a direction tending to parallel the mesa slope. Deep into the tunnel and well under the flat part of the mesa, fractures are essentially vertical with strikes approximately N45°E, which substantiates the usual vertical fracture assumption in traditional fracture operations performed at depth in vertical boreholes. Advantages, limitations, and problem areas associated with extracting in situ stress fields from hydraulic fracture pressure records are discussed in detail.

  1. Surrogate-based optimization of hydraulic fracturing in pre-existing fracture networks

    E-print Network

    Lu, Zhiming

    Surrogate-based optimization of hydraulic fracturing in pre-existing fracture networks Mingjie Chen Keywords: Hydraulic fracturing Fractal dimension Surrogate model Optimization Global sensitivity a b s t r a c t Hydraulic fracturing has been used widely to stimulate production of oil, natural gas

  2. Hydraulic fracturing in granite under geothermal conditions

    USGS Publications Warehouse

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

    1980-01-01

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

  3. Micromechanical Aspects of Hydraulic Fracturing Processes

    NASA Astrophysics Data System (ADS)

    Galindo-torres, S. A.; Behraftar, S.; Scheuermann, A.; Li, L.; Williams, D.

    2014-12-01

    A micromechanical model is developed to simulate the hydraulic fracturing process. The model comprises two key components. Firstly, the solid matrix, assumed as a rock mass with pre-fabricated cracks, is represented by an array of bonded particles simulated by the Discrete Element Model (DEM)[1]. The interaction is ruled by the spheropolyhedra method, which was introduced by the authors previously and has been shown to realistically represent many of the features found in fracturing and communition processes. The second component is the fluid, which is modelled by the Lattice Boltzmann Method (LBM). It was recently coupled with the spheropolyhedra by the authors and validated. An advantage of this coupled LBM-DEM model is the control of many of the parameters of the fracturing fluid, such as its viscosity and the injection rate. To the best of the authors' knowledge this is the first application of such a coupled scheme for studying hydraulic fracturing[2]. In this first implementation, results are presented for a two-dimensional situation. Fig. 1 shows one snapshot of the LBM-DEM coupled simulation for the hydraulic fracturing where the elements with broken bonds can be identified and the fracture geometry quantified. The simulation involves a variation of the underground stress, particularly the difference between the two principal components of the stress tensor, to explore the effect on the fracture path. A second study focuses on the fluid viscosity to examine the effect of the time scales of different injection plans on the fracture geometry. The developed tool and the presented results have important implications for future studies of the hydraulic fracturing process and technology. references 1. Galindo-Torres, S.A., et al., Breaking processes in three-dimensional bonded granular materials with general shapes. Computer Physics Communications, 2012. 183(2): p. 266-277. 2. Galindo-Torres, S.A., A coupled Discrete Element Lattice Boltzmann Method for the simulation of fluid-solid interaction with particles of general shapes. Computer Methods in Applied Mechanics and Engineering, 2013. 265(0): p. 107-119.

  4. Seismic characteristics of tensile fracture growth induced by hydraulic fracturing

    NASA Astrophysics Data System (ADS)

    Eaton, D. W. S.; Van der Baan, M.; Boroumand, N.

    2014-12-01

    Hydraulic fracturing is a process of injecting high-pressure slurry into a rockmass to enhance its permeability. Variants of this process are used for unconventional oil and gas development, engineered geothermal systems and block-cave mining; similar processes occur within volcanic systems. Opening of hydraulic fractures is well documented by mineback trials and tiltmeter monitoring and is a physical requirement to accommodate the volume of injected fluid. Numerous microseismic monitoring investigations acquired in the audio-frequency band are interpreted to show a prevalence of shear-dominated failure mechanisms surrounding the tensile fracture. Moreover, the radiated seismic energy in the audio-frequency band appears to be a miniscule fraction (<< 1%) of the net injected energy, i.e., the integral of the product of fluid pressure and injection rate. We use a simple penny-shaped crack model as a predictive framework to describe seismic characteristics of tensile opening during hydraulic fracturing. This model provides a useful scaling relation that links seismic moment to effective fluid pressure within the crack. Based on downhole recordings corrected for attenuation, a significant fraction of observed microseismic events are characterized by S/P amplitude ratio < 5. Despite the relatively small aperture of the monitoring arrays, which precludes both full moment-tensor analysis and definitive identification of nodal planes or axes, this ratio provides a strong indication that observed microseismic source mechanisms have a component of tensile failure. In addition, we find some instances of periodic spectral notches that can be explained by an opening/closing failure mechanism, in which fracture propagation outpaces fluid velocity within the crack. Finally, aseismic growth of tensile fractures may be indicative of a scenario in which injected energy is consumed to create new fracture surfaces. Taken together, our observations and modeling provide evidence that failure mechanisms documented by passive monitoring of hydraulic fractures may contain a significant component of tensile failure, including fracture opening and closing, although creation of extensive new fracture surfaces may be a seismically inefficient process that radiates at sub-audio frequencies.

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

    SciTech Connect

    Mike L. Laue

    1997-05-30

    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.

  6. Influence of Rock Fabric on Hydraulic Fracture Propagation: Laboratory Study

    NASA Astrophysics Data System (ADS)

    Stanchits, S. A.; Desroches, J.; Burghardt, J.; Surdi, A.; Whitney, N.

    2014-12-01

    Massive hydraulic fracturing is required for commercial gas production from unconventional reservoirs. These reservoirs are often highly fractured and heterogeneous, which may cause significant fracture complexity and also arrest propagation of hydraulic fractures, leading to production decrease. One of the goals of our study was to investigate the influence of rock fabric features on near-wellbore fracture geometry and complexity. We performed a series of laboratory tests on Niobrara outcrop shale blocks with dimensions of 30 x 30 x 36 inches in a true-triaxial loading frame. Acoustic Emission (AE) technique was applied to monitor hydraulic fracture initiation and dynamics of fracture propagation. After the tests, the shape of the created hydraulic fracture was mapped by goniometry technique. To estimate fracture aperture, particles of different sizes were injected with fracturing fluid. In all tests, AE analysis indicated hydraulic fracture initiation prior to breakdown or the maximum of wellbore pressure. In most tests, AE analysis revealed asymmetrical hydraulic fracture shapes. Post-test analysis demonstrated good correspondence of AE results with the actual 3D shape of the fracture surface map. AE analysis confirmed that in some of these tests, the hydraulic fracture approached one face of the block before the maximum wellbore pressure had been reached. We have found that in such cases the propagation of hydraulic fracture in the opposite direction was arrested by the presence of mineralized interfaces. Mapping the distribution of injected particles confirmed the creation of a narrow-width aperture in the vicinity of pre-existing interfaces, restricting fracture conductivity. Based on the results of our study, we concluded that the presence of planes of weakness, such as mineralized natural fractures, can result in the arrest of hydraulic fracture propagation, or in poor fracture geometries with limited aperture, that in turn could lead to high net pressure and low fracture conductivity, restricted proppant delivery, and decreased production.

  7. Hydraulic Fracturing Return Waters and Legacy Landscapes

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    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.

  8. Investigation of the influence of stress shadows on horizontal hydraulic fractures from adjacent lateral wells

    E-print Network

    Investigation of the influence of stress shadows on horizontal hydraulic fractures from adjacent: Unconventional hydraulic fracturing Stress shadow Adjacent lateral wells Simulfrac and zipperfrac Numerical the simultaneous or near simultaneous hydraulic fracturing of adjacent lateral wells to maximize the fracture

  9. New groups focus on hydraulic fracturing

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2013-04-01

    The Scientific Advisory Board of the U.S. Environmental Protection Agency (EPA) has formed a 31-member expert panel to conduct a peer review of the agency's upcoming draft report on the potential effects of hydraulic fracturing on drinking water resources, EPA announced on 24 March. Panel members include experts in a number of areas, including petroleum/natural gas engineering, geology/geophysics, and waste water and drinking water treatment.

  10. Northwestern University Technological Institute Tight Shale Gas-Hydraulic Fracturing

    E-print Network

    Guo, Dongning

    Northwestern University Technological Institute Tight Shale Gas-Hydraulic Fracturing Seminar Series How can we Greatly Improve Hydraulic Fracturing Efficiency Sidney Green Schlumberger Senior Advisor microns 10 inches #12;"A Picture is worth 10,000 words", but the correct mental picture of hydraulic

  11. Reply to Davies: Hydraulic fracturing remains a possible mechanism for

    E-print Network

    Jackson, Robert B.

    LETTER Reply to Davies: Hydraulic fracturing remains a possible mechanism for observed methane in aquifers overlying the Marcellus formation but asserts that we prematurely ascribed its cause to hydraulic mechanisms were leaky gas well casings and the possibility that hydraulic fracturing might generate new

  12. Potential contaminant pathways from hydraulically fractured shale to aquifers.

    PubMed

    Myers, Tom

    2012-01-01

    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

  13. Hydraulic Fractures: multiscale phenomena, asymptotic and numerical solutions

    E-print Network

    Peirce, Anthony

    Hydraulic Fractures: multiscale phenomena, asymptotic and numerical solutions SANUM Conference (UMN) Eduard Siebrits (SLB) #12;2 Outline · Examples of hydraulic fractures · Governing equations well stimulation Fracturing Fluid Proppant #12;5 Quarries #12;6 Magma flow Tarkastad #12;7 Model EQ 1

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    SciTech Connect

    David S. Schechter

    2005-04-27

    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.

  16. Vertical root fractures and their management

    PubMed Central

    Khasnis, Sandhya Anand; Kidiyoor, Krishnamurthy Haridas; Patil, Anand Basavaraj; Kenganal, Smita Basavaraj

    2014-01-01

    Vertical root fractures associated with endodontically treated teeth and less commonly in vital teeth represent one of the most difficult clinical problems to diagnose and treat. In as much as there are no specific symptoms, diagnosis can be difficult. Clinical detection of this condition by endodontists is becoming more frequent, where as it is rather underestimated by the general practitioners. Since, vertical root fractures almost exclusively involve endodontically treated teeth; it often becomes difficult to differentiate a tooth with this condition from an endodontically failed one or one with concomitant periodontal involvement. Also, a tooth diagnosed for vertical root fracture is usually extracted, though attempts to reunite fractured root have been done in various studies with varying success rates. Early detection of a fractured root and extraction of the tooth maintain the integrity of alveolar bone for placement of an implant. Cone beam computed tomography has been shown to be very accurate in this regard. This article focuses on the diagnostic and treatment strategies, and discusses about predisposing factors which can be useful in the prevention of vertical root fractures. PMID:24778502

  17. Electric-hydraulic conductivity correlation in fractured crystalline bedrock: Central Landfill, Rhode Island, USA

    NASA Astrophysics Data System (ADS)

    Frohlich, Reinhard K.; Fisher, John J.; Summerly, E.

    1996-10-01

    Remote sensing and geoelectrical methods were used to find water-bearing fractures in the Scituate granite under the Central Landfill of Rhode Island. These studies were necessary to evaluate the integrity of the sanitary landfill and for planning safe landfill extensions. The most useful results were obtained with fracture trace analysis using Landsat and SLAR imagery in combination with ground-based resistivity measurements using Schlumberger vertical electrical soundings based on the assumption of horizontally layered strata. Test borings and packer tests confirmed, in the presence of a lineament and low bedrock resistivity, the probable existence of high bedrock fracture density and high average hydraulic conductivity. However, not every lineament was found to be associated with high fracture density and high hydraulic conductivity. Lineaments alone are not a reliable basis for characterising a landfill site as being affected by fractured bedrock. Horizontal fractures were found in borings located away from lineaments. High values of hydraulic conductivity were correlated with low bedrock resistivities. Bedrock resistivities between 60 and 700 ? m were associated with average hydraulic conductivities between 4 and 60 cm/day. In some cases very low resistivities were confined to the upper part of the bedrock where the hydraulic conductivity was very large. These types of fractures apparently become narrower in aperture with depth. Bedrock zones having resistivities greater than 1000 ? m showed, without exception, no flow to the test wells. Plots of bedrock resistivity versus the average hydraulic conductivity indicate that the resistivity decreases with increasing hydraulic conductivity. This relationship is inverse to that found in most unconsolidated sediments and is useful for estimating the hydraulic conductivity in groundwater surveys in fractured bedrock. In appropriate settings such as the Central Landfill site in New England, this electric-hydraulic correlation relationship, supplemented by lineament trace analysis, can be used effectively to estimate the hydraulic conductivity in bedrock from only a limited number of resistivity depth soundings and test wells.

  18. Hydraulic Fracture Monitoring: A Jonah Field Case Study

    E-print Network

    Seher, T.

    2011-01-01

    Hydraulic fracturing involves the injection of a fluid to fracture oil and gas reservoirs, and thus increase their permeability. The process creates numerous microseismic events, which can be used to monitor subsurface ...

  19. A Study of Hydraulic Fracturing Initiation in Transversely Isotropic Rocks 

    E-print Network

    Serajian, Vahid

    2011-10-21

    Hydraulic fracturing of transverse isotropic reservoirs is of major interest for reservoir stimulation and in-situ stress estimation. Rock fabric anisotropy not only causes in-situ stress anisotropy, but also affects fracture initiation from...

  20. 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...

  1. Experimental study of step-displacement hydraulic fracturing on naturally fractured shale outcrops

    NASA Astrophysics Data System (ADS)

    Cheng, Wan; Jin, Yan; Chen, Mian

    2015-08-01

    Low porosity and permeability make it extremely difficult to develop shale oil and gas reservoirs. The stimulated reservoir volume is believed to have potential to obtain industry production by multi-stage or simultaneous fracturing in horizontal wells. The formation mechanism of network hydraulic fractures in fractured shale reservoirs remains poorly understood. In this article, a true tri-axial hydraulic fracturing system associated acoustic emission monitor was deployed to simulate hydraulic fracturing on shale outcrops. Results showed that the properties of natural fractures (such as aperture, orientation), compared to the viscosity and displacement of the fracturing fluid, affect the propagation direction of hydraulic fractures more predominantly. Each natural fracture in a natural fracture network can independently affect the hydraulic fracture. Low displacement (below the diffusion ability of a reservoir) fracturing tends to connect pre-existing fractures, while high displacement (surpass the diffusion ability of a reservoir) tends to create new fractures. After the breakdown pressure, an increase in injection rate results in more acoustic emission energy and induces new fractures. These results suggest that step-displacement fracturing technology is a possible mechanism to obtain effective fracture networks. Such an understanding would help to avoid unproductive, or sometimes destructive, costly segments of the hydraulic fracturing treatment design.

  2. Calibration of hydraulic and tracer tests in fractured media

    E-print Network

    Politècnica de Catalunya, Universitat

    Calibration of hydraulic and tracer tests in fractured media represented by a DFN Model L. D. Donado, X. Sanchez-Vila, E. Ruiz* & F. J. Elorza** * Enviros Spain S.L. ** UPM #12;Fractured Media Water flows through fractures (matrix basically impervious ­ though relevant to transport) Fractures at all

  3. Analytical Modeling of Shale Hydraulic Fracturing and Gas Production

    NASA Astrophysics Data System (ADS)

    Xu, W.

    2012-12-01

    Shale gas is abundant all over the world. Due to its extremely low permeability, extensive stimulation of a shale reservoir is always required for its economic production. Hydraulic fracturing has been the primary method of shale reservoir stimulation. Consequently the design and optimization of a hydraulic fracturing treatment plays a vital role insuring job success and economic production. Due to the many variables involved and the lack of a simple yet robust tool based on fundamental physics, horizontal well placement and fracturing job designs have to certain degree been a guessing game built on previous trial and error experience. This paper presents a method for hydraulic fracturing design and optimization in these environments. The growth of a complex hydraulic fracture network (HFN) during a fracturing job is equivalently represented by a wiremesh fracturing model (WFM) constructed on the basis of fracture mechanics and mass balance. The model also simulates proppant transport and placement during HFN growth. Results of WFM simulations can then be used as the input into a wiremesh production model (WPM) constructed based on WFM. WPM represents gas flow through the wiremesh HFN by an elliptic flow and the flow of gas in shale matrix by a novel analytical solution accounting for contributions from both free and adsorbed gases stored in the pore space. WPM simulation is validated by testing against numerical simulations using a commercially available reservoir production simulator. Due to the analytical nature of WFM and WPM, both hydraulic fracturing and gas production simulations run very fast on a regular personal computer and are suitable for hydraulic fracturing job design and optimization. A case study is presented to demonstrate how a non-optimized hydraulic fracturing job might have been optimized using WFM and WPM simulations.Fig. 1. Ellipsoidal representation of (a) stimulated reservoir and (b) hydraulic fracture network created by hydraulic fracturing treatment. Fig. 2. Gas flow represented by (a) elliptical flow through fracture network and (b) linear flow within reservoir matrix.

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

    PubMed

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

    2013-01-01

    Hydraulic fracturing is used to extract natural gas from shale formations. The process involves injecting into the ground fracturing fluids that contain thousands of gallons of chemical additives. Companies are not mandated by federal regulations to disclose the identities or quantities of chemicals used during hydraulic fracturing operations on private or public lands. States have begun to regulate hydraulic fracturing fluids by mandating chemical disclosure. These laws have shortcomings including nondisclosure of proprietary or "trade secret" mixtures, insufficient penalties for reporting inaccurate or incomplete information, and timelines that allow for after-the-fact reporting. These limitations leave lawmakers, regulators, public safety officers, and the public uninformed and ill-prepared to anticipate and respond to possible environmental and human health hazards associated with hydraulic fracturing fluids. We explore hydraulic fracturing exemptions from federal regulations, as well as current and future efforts to mandate chemical disclosure at the federal and state level. PMID:23552653

  5. Analysis of the Influence of a Natural Fracture Network on Hydraulic Fracture Propagation in Carbonate Formations

    NASA Astrophysics Data System (ADS)

    Liu, Zhiyuan; Chen, Mian; Zhang, Guangqing

    2014-03-01

    A new experimental model has been designed to simulate the influence of a natural fracture network on the propagation geometry of hydraulic fractures in naturally fractured formations using a tri-axial fracturing system. In this model, a parallel and symmetrical pre-fracture network was created by placing cement plates in a cubic mold and filling the mold with additional cement to create the final testing block. The surface of the plates will thus be weakly cemented and form pre-fractures. The dimension and direction of the pre-fractures can be controlled using the plates. The experiments showed that the horizontal differential stress and the angle between the maximum horizontal principal in situ stress and the pre-fracture are the dominating factors for the initiation and propagation of hydraulic fractures. For and or and , the direction of the initiation and propagation of the hydraulic fractures are consistent with or deviate from the normal direction of the pre-fracture. When the hydraulic fractures approach the pre-fractures, the direction of the hydraulic fracture propagation will be consistent with the normal direction of the pre-fracture. Otherwise, the hydraulic fracture will deflect and perpendicularly cross the parallel and symmetric pre-fracture network. For and , and or and , before the hydraulic fracture and the pre-fractures intersect, the direction of the hydraulic fracture propagation remains unchanged, and the pre-fractures open or dilate when the hydraulic fracture propagates to the intersection point, forming a complicated hydraulic fracture network with the propagation region of the overall hydraulic fracture network taking the shape of an ellipse. In this condition, the complexity level of the hydraulic fracture is controlled by the net pressure, the compressive normal stress acting on the pre-fractures, the shearing strength and the cohesion strength of the planes of weakness. The conclusions of this research are inconsistent with the formulation of the approach angle that has been widely accepted by previous studies. The principle of hydraulic fracture propagation is that it follows the least resistance, the most preferential propagation, and the shortest propagation path.

  6. Veining Failure and Hydraulic Fracturing in Shales

    NASA Astrophysics Data System (ADS)

    Mighani, S.; Sondergeld, C. H.; Rai, C. S.

    2014-12-01

    During the hydraulic fracturing, the pressurized fluid creates new fractures and reactivates existing natural fractures forming a highly conductive Stimulated Reservoir Volume (SRV) around the borehole. We extend the previous work on Lyons sandstone and pyrophyllite to anisotropic shale from the Wolfcamp formation. We divide the rock anisotropy into two groups: a) conventional and b) unconventional (shaly) anisotropy. X-ray Computed Tomography (CT), compressional velocity anisotropy, and SEM analysis are used to identify three causes of anisotropy: bedding planes, clay lamination, and calcite veins. Calcite vein is a subsequently filled with calcite bonded weakly to the matrix. Velocity anisotropy and visual observations demonstrate the calcite filled veins to be mostly subparallel to the fabric direction. Brazilian tests are carried out to observe the fracture initiation and propagation under tension. High speed photography (frame rate 300,000 frame/sec) was used to capture the failure. Strain gauges and Acoustic Emission (AE) sensors recorded the deformation leading up to and during failure. SEM imaging and surface profilometry were employed to study the post-failure fracture system and failed surface topology. Fracture permeability was measured as a function of effective stress. Brazilian tests on small disks containing a centered single vein revealed the shear strength of the veins. We interpret the strain data and number, frequency, and amplitude of AE events which are correlated well with the observed fracture process zone, surface roughness, and permeability. The unpropped fracture has enhanced permeability by two orders of magnitude. The observed anisotropic tensile failure seems to have a universal trend with a minimum strength occurring at 15o orientation with respect to the loading axis. The veins at 15o orientation with respect to the loading axis were easily activated at 30% of the original failure load. The measured strength of the vein is as low as 6% of the matrix. Surface roughness measurements show the vein to be as rough as the main tensile fracture in the matrix. The observations suggest that fracking through a deviated well reduces the breakdown pressure significantly and can activate a large number of veins with enhanced conductivity without the need for excessive proppant injection.

  7. 78 FR 55253 - Notification of Public Teleconference of the Hydraulic Fracturing Research Advisory Panel

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-10

    ...Hydraulic Fracturing Research Advisory Panel AGENCY: Environmental Protection Agency...Hydraulic Fracturing Research Advisory Panel to receive written and oral comments from...Hydraulic Fracturing Research Advisory Panel will comply with the provisions of...

  8. 78 FR 25267 - Request for Information To Inform Hydraulic Fracturing Research Related to Drinking Water Resources

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-30

    ...FRL-9807-7] Request for Information To Inform Hydraulic Fracturing Research Related to Drinking...research on the potential impacts of hydraulic fracturing on drinking water resources...research to examine the relationship between hydraulic fracturing and drinking water...

  9. 77 FR 67361 - Request for Information To Inform Hydraulic Fracturing Research Related to Drinking Water Resources

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-09

    ...FRL-9750-8] Request for Information To Inform Hydraulic Fracturing Research Related to Drinking...research on the potential impacts of hydraulic fracturing on drinking water resources...research to examine the relationship between hydraulic fracturing and drinking water...

  10. 78 FR 20637 - Notification of Public Meeting and a Public Teleconference of the Hydraulic Fracturing Research...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-05

    ...Meeting and a Public Teleconference of the Hydraulic Fracturing Research Advisory Panel AGENCY...meeting and public teleconference of the Hydraulic Fracturing Research Advisory Panel to...EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water...

  11. 75 FR 35023 - Informational Public Meetings for Hydraulic Fracturing Research Study

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-21

    ...FRL-9164-8] Informational Public Meetings for Hydraulic Fracturing Research Study AGENCY: Environmental...plan to study the relationship between hydraulic fracturing and drinking water. The meetings...plans during the meetings. DATES: The Hydraulic Fracturing Study informational...

  12. 78 FR 55253 - Notification of Public Teleconference of the Hydraulic Fracturing Research Advisory Panel

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-10

    ... AGENCY Notification of Public Teleconference of the Hydraulic Fracturing Research Advisory Panel AGENCY...) Science Advisory Board (SAB) Staff Office announces a public teleconference of the Hydraulic Fracturing... information related to hydraulic fracturing and drinking water resources. DATES: The public...

  13. Hydraulic characterization of the fracture framework in carbonate rock underlying CWML Site, Smithville, Ontario

    SciTech Connect

    Lapcevic, P.; Novakowski, K.; Bickerton, G.; Voralek, J.

    1997-12-31

    The successful use of engineered systems to contain and/or remediate the contaminated groundwater in the bedrock underlying the CWML site at Smithville, ON is largely dependent on an understanding of the complex groundwater flow system. The Lockport Dolostone, which underlies most of the Niagara peninsula, is a shallow flat-lying porous carbonate rock having extensive horizontal bedding plane fractures. Vertical fractures which intersect the bedding planes form a three dimensional fracture framework. Detailed field investigations are currently underway to characterize groundwater flow within this fracture framework. To conduct the investigation fifteen boreholes were drilled through the entire thickness of the Lockport Formation. The distribution of both vertical and bedding plane fractures was delineated from core analysis. Constant-head hydraulic tests using 2 meter and 0.5 meter packer test intervals were used to determine both the bulk transmissivity of the unfractured rock mass and that for individual fractures. The results show that while most breaks noted in the core are bedding-plane fractures or broken-core zones, vertical fractures are also prevalent particularly in the Eramosa Formation. Fracture strikes show a dominant joint sets consistent with trends observed regionally. The vertical distribution of transmissivity in the Lockport Dolostone ranges over eight orders of magnitude at the site. Preliminary geostatistical analysis suggests that there may be at least three separate distributions of structure present in the transmissivity data: (1) distribution of the T of fractures, (2) distribution of the T of the matrix, and (3) position of the fractures.

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

    PubMed

    Ewers, U; Gordalla, B; Frimmel, F

    2013-11-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

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

    SciTech Connect

    Mike L. Laue

    1998-11-06

    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.

  17. 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...

  18. On equivalence of thinning fluids used for hydraulic fracturing

    E-print Network

    Linkov, Alexander

    2012-01-01

    The paper aims to answer the question: if and how non-Newtonian fluids may be compared in their mechanical action when used for hydraulic fracturing? By employing the modified formulation of the PKN problem we obtain its simple analytical solutions in the cases of perfectly plastic and Newtonian fluids. Since the results for shear thinning fluids are intermediate between those for these cases, the obtained equation for the fracture length suggests a criterion of the equivalence of various shear thinning fluids for the problem of hydraulic fractures. We assume fluids equivalent in their hydrofracturing action, when at a reference time they produce fractures of the same length. The equation for the fracture length translates the equivalence in terms of the hydraulic fracture length and treatment time into the equivalence in terms of the properties of a fracturing fluid (behavior and consistency indices). Analysis shows that the influence of the consistency and behavior indices on the fracture length, particle v...

  19. A magnetic method for determining the geometry of hydraulic fractures

    USGS Publications Warehouse

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

    1976-01-01

    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.

  20. Subcritical growth of natural hydraulic fractures

    NASA Astrophysics Data System (ADS)

    Garagash, D.

    2014-12-01

    Joints are the most common example of brittle tensile failure in the crust. Their genesis at depth is linked to the natural hydraulic fracturing, which requires pore fluid pressure in excess of the minimum in situ stress [Pollard and Aidyn, JSG1988]. Depending on the geological setting, high pore pressure can result form burial compaction of interbedded strata, diagenesis, or tectonics. Common to these loading scenarios is slow build-up of pore pressure over a geological timescale, until conditions for initiation of crack growth are met on favorably oriented/sized flaws. The flaws can vary in size from grain-size cracks in igneous rocks to a fossil-size flaws in clastic rock, and once activated, are inferred to propagate mostly subcritically [Segall JGR 1984; Olson JGR 1993]. Despite many observational studies of natural hydraulic fractures, the modeling attempts appear to be few [Renshaw and Harvey JGR 1994]. Here, we use boundary integral formulation for the pore fluid inflow from the permeable rock into a propagating joint [Berchenko et al. IJRMMS 1997] coupled with the criteria for subcritical propagation assisted by the environmental effects of pore fluid at the crack tip to solve for the evolution of a penny-shape joint, which, in interbedded rock, may eventually evolve to short-blade geometry (propagation confined to a bed). Initial growth is exceedingly slow, paced by the stress corrosion reaction kinetics at the crack tip. During this stage the crack is fully-drained (i.e. the fluid pressure in the crack is equilibrated with the ambient pore pressure). This "slow" stage is followed by a rapid acceleration, driven by the increase of the mechanical stress intensity factor with the crack length, towards the terminal joint velocity. We provide an analytical expression for the latter as a function of the rock diffusivity, net pressure loading at the initiation (or flaw lengthscale), and parameters describing resistance to fracture growth. Due to a much slower rate of the crack volume expansion of short-blade joints compared to that of penny-shape joints, the former would propagate much faster than the latter under otherwise identical conditions. Finally, we speculate about possible relation of the predicted patterns of joint development with morphology of joint fracture surfaces observed in sedimentary rock.

  1. Active and passive seismic imaging of a hydraulic fracture in diatomite

    SciTech Connect

    Vinegar, H.J.; Wills, P.B.; De Martini, D.C. )

    1992-01-01

    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 the well to be fracture treated. Data analysis indicates that the minifracture and main hydraulic fracture stimulations resulted in a nearly vertical fracture zone (striking N26{degrees}E) vertically segregated into two separate elements, the uppermost of which grew 60 ft above the perforated interval. The interwell seismic effects are consistent with a side process zone of reduced shear velocity, which remote-well microseismic data independently suggest may be as wide as 40 ft. The experiments indicate complicated processes occurring during hydraulic fracturing that have significant implications for stimulation, waterflooding, in fill drilling, and EOR. These processes are neither well understood nor included in current hydraulic fracture models.

  2. Advanced hydraulic fracturing methods to create in situ reactive barriers

    SciTech Connect

    Murdoch, L. |; Siegrist, B.; Meiggs, T.

    1997-12-31

    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.

  3. Public health and high volume hydraulic fracturing.

    PubMed

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

    2013-01-01

    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

  4. Review of hydraulic fracture mapping using advanced accelerometer-based receiver systems

    SciTech Connect

    Warpinski, N.R.; Uhl, J.E.; Engler, B.P.

    1997-03-01

    Hydraulic fracturing is an important tool for natural gas and oil exploitation, but its optimization has been impeded by an inability to observe how the fracture propagates and what its overall dimensions are. The few experiments in which fractures have been exposed through coring or mineback have shown that hydraulic fractures are complicated multi-stranded structures that may behave much differently than currently predicted by models. It is clear that model validation, fracture optimization, problem identification and solution, and field development have all been encumbered by the absence of any ground truth information on fracture behavior in field applications. The solution to this problem is to develop techniques to image the hydraulic fracture in situ from either the surface, the treatment well, or offset wells. Several diagnostic techniques have been available to assess individual elements of the fracture geometry, but most of these techniques have limitations on their usefulness. For example, tracers and temperature logs can only measure fracture height at the wellbore, well testing and production history matching provide a productive length which may or may not be different from the true fracture length, and tiltmeters can provide accurate information on azimuth and type of fracture (horizontal or vertical), but length and height can only be extracted from a non-unique inversion of the data. However, there is a method, the microseismic technique, which possesses the potential for imaging the entire hydraulic fracture and, more importantly, its growth history. This paper discusses application of advanced technology to the microseismic method in order to provide detailed accurate images of fractures and their growth processes.

  5. Estimating the fracture density of small-scale vertical fractures when large-scale vertical fractures are present

    NASA Astrophysics Data System (ADS)

    Liu, Yuwei; Dong, Ning; Fehler, Mike; Fang, Xinding; Liu, Xiwu

    2015-06-01

    Fractures in reservoirs significantly affect reservoir flow properties in subsequent years, which means that fracture characteristics such as preferred orientation, crack density or fracture compliance, what filling is in the fractures and so on are of great importance for reservoir development. When fractures are vertical, aligned and their dimensions are small relative to the seismic wavelength, the medium can be considered to be an equivalent horizontal transverse isotropic (HTI) medium. However, geophysical data acquired over naturally fractured reservoirs often reveal the presence of multiple fracture sets. We investigate a case where there are two vertical sets of fractures having differing length scales. One fracture set has length scale that is much smaller than the seismic wavelength but the other has length scale that is similar to the seismic wavelength. We use synthetic data to investigate the ability to infer the properties of the small-scale fractures in the presence of the large-scale fracture set. We invert for the Thomsen-type anisotropic coefficients of the small-scale fracture set by using the difference of the P wave amplitudes at two azimuths, which makes the inversion convex. Then we investigate the influence of the presence of the large-scale fractures on our ability to infer the properties of the small-scale fracture set. Surprisingly, we find that we can reliably infer the fracture density of the small-scale fractures even in the presence of large-scale fractures having significant compliance values. Although the inversion results for Thomsen-type anisotropic coefficients of small-scale fractures for one model are not good enough to figure out whether it is gas-filled or fluid-filled, we can find a big change of Thomsen-type anisotropic coefficient {{\\varepsilon}(V)} between the models in which small-scale fractures are filled with gas and fluid.

  6. Studies investigate effects of hydraulic fracturing

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2012-11-01

    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.

  7. Hydraulic fracture energy budget: Insights from the laboratory

    NASA Astrophysics Data System (ADS)

    Goodfellow, S. D.; Nasseri, M. H. B.; Maxwell, S. C.; Young, R. P.

    2015-05-01

    In this paper we present results from a series of laboratory hydraulic fracture experiments designed to investigate various components of the energy budget. The experiments involved a cylindrical sample of Westerly granite being deformed under various triaxial stress states and fractured with distilled water, which was injected at a range of constant rates. Acoustic emission sensors were absolutely calibrated, and the radiated seismic energy was estimated. The seismic energy was found to range from 7.02E-8% to 1.24E-4% of the injection energy which is consistent with a range of values for induced seismicity from field-scale hydraulic fracture operations. The deformation energy (crack opening) of the sample during hydraulic fracture propagation was measured using displacement sensors and ranged from 18% to 94% of the injection energy. Our results support the conclusion that aseismic deformation is a significant term in the hydraulic fracture energy budget.

  8. The Effects of Fracture Orientation and Anisotropy on Hydraulic Fracture Conductivity in the Marcellus Shale 

    E-print Network

    McGinley, Mark John

    2015-05-12

    of hydraulically-induced fractures. Ultimately, the experiments conducted as part of this work show that fracture conductivity trends are strongly tied to both proppant concentration and the rock’s mechanical properties....

  9. Hydraulic Fracturing: Paving the Way for a Sustainable Future?

    PubMed Central

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

    2014-01-01

    With the introduction of hydraulic fracturing technology, the United States has become the largest natural gas producer in the world with a substantial portion of the production coming from shale plays. In this review, we examined current hydraulic fracturing literature including associated wastewater management on quantity and quality of groundwater. We conclude that proper documentation/reporting systems for wastewater discharge and spills need to be enforced at the federal, state, and industrial level. Furthermore, Underground Injection Control (UIC) requirements under SDWA should be extended to hydraulic fracturing operations regardless if diesel fuel is used as a fracturing fluid or not. One of the biggest barriers that hinder the advancement of our knowledge on the hydraulic fracturing process is the lack of transparency of chemicals used in the practice. Federal laws mandating hydraulic companies to disclose fracturing fluid composition and concentration not only to federal and state regulatory agencies but also to health care professionals would encourage this practice. The full disclosure of fracturing chemicals will allow future research to fill knowledge gaps for a better understanding of the impacts of hydraulic fracturing on human health and the environment. PMID:24790614

  10. Hydraulic fracturing: paving the way for a sustainable future?

    PubMed

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

    2014-01-01

    With the introduction of hydraulic fracturing technology, the United States has become the largest natural gas producer in the world with a substantial portion of the production coming from shale plays. In this review, we examined current hydraulic fracturing literature including associated wastewater management on quantity and quality of groundwater. We conclude that proper documentation/reporting systems for wastewater discharge and spills need to be enforced at the federal, state, and industrial level. Furthermore, Underground Injection Control (UIC) requirements under SDWA should be extended to hydraulic fracturing operations regardless if diesel fuel is used as a fracturing fluid or not. One of the biggest barriers that hinder the advancement of our knowledge on the hydraulic fracturing process is the lack of transparency of chemicals used in the practice. Federal laws mandating hydraulic companies to disclose fracturing fluid composition and concentration not only to federal and state regulatory agencies but also to health care professionals would encourage this practice. The full disclosure of fracturing chemicals will allow future research to fill knowledge gaps for a better understanding of the impacts of hydraulic fracturing on human health and the environment. PMID:24790614

  11. Transport efficiency and dynamics of hydraulic fracture networks

    NASA Astrophysics Data System (ADS)

    Sachau, Till; Bons, Paul; Gomez-Rivas, Enrique

    2015-08-01

    Intermittent fluid pulses in the Earth's crust can explain a variety of geological phenomena, for instance the occurrence of hydraulic breccia. Fluid transport in the crust is usually modeled as continuous darcian flow, ignoring that sufficient fluid overpressure can cause hydraulic fractures as fluid pathways with very dynamic behavior. Resulting hydraulic fracture networks are largely self-organized: opening and healing of hydraulic fractures depends on local fluid pressure, which is, in turn, largely controlled by the fracture network. We develop a crustal-scale 2D computer model designed to simulate this process. To focus on the dynamics of the process we chose a setup as simple as possible. Control factors are constant overpressure at a basal fluid source and a constant 'viscous' parameter controlling fracture-healing. Our results indicate that at large healing rates hydraulic fractures are mobile, transporting fluid in intermittent pulses to the surface and displaying a 1/f? behavior. Low healing rates result in stable networks and constant flow. The efficiency of the fluid transport is independent from the closure dynamics of veins or fractures. More important than preexisting fracture networks is the distribution of fluid pressure. A key requirement for dynamic fracture networks is the presence of a fluid pressure gradient.

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

    SciTech Connect

    Mike L. Laue

    2001-09-28

    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.

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

    USGS Publications Warehouse

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

    2002-01-01

    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.

  14. Tilmeter hydraulic fracture imaging enhancement project: Progress repeort

    SciTech Connect

    Castillo, D.A.; Wright, C.A.; Conant, R.A.

    1995-12-31

    Over half of all oil & gas production wells drilled in the United States depend upon hydraulic fracturing to sustain or enhance production. However, there is no existing technology that allows detailed near-surface imaging of these hydraulically-driven fractures at depths greater than about 5000 feet. To image hydraulic fractures in the 8000`-10,000` depth range, we are currently redesigning tiltmeter tools in order to deploy the instruments deeper to escape the cultural/natural surface noise that often masks the hydrofrac signal. With nearly noise-free data, we should be in a better position to separate the earth-tide signal from the tiltmeter signal and investigate fine-scale hydraulic fracturing processes.

  15. Acoustic emissions in hydraulic fracturing of Barre granite

    E-print Network

    Li, Qiuyi Bing

    2015-01-01

    The purpose of this work is to observe acoustic emissions (AE) generated by laboratory scale hydraulic fracturing of Barre granite specimens with single or double flaw geometry. The scope of this work covers the experimental ...

  16. EPA releases progress report on hydraulic fracturing study

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2013-01-01

    The U.S. Environmental Protection Agency (EPA) provided a 21 December progress report on its ongoing national study about the potential impacts of hydraulic fracturing on drinking water resources. The agency said that a draft of the congressionally requested study will be released in 2014 for public and peer review and that its progress report does not draw conclusions about the potential impacts of hydraulic fracturing, often referred to as fracking.

  17. Fracture opening/propagation behavior and their significance on pressure-time records during hydraulic fracturing

    SciTech Connect

    Takashi Kojima; Yasuhiko Nakagawa; Koji Matsuki; Toshiyuki Hashida

    1992-01-01

    Hydraulic fracturing with constant fluid injection rate was numerically modeled for a pair of rectangular longitudinal fractures intersecting a wellbore in an impermeable rock mass, and numerical calculations have been performed to investigate the relations among the form of pressure-time curves, fracture opening/propagation behavior and permeability of the mechanically closed fractures. The results have shown that both permeability of the fractures and fluid injection rate significantly influence the form of the pressure-time relations on the early stage of fracture opening. Furthermore it has been shown that wellbore pressure during fracture propagation is affected by the pre-existing fracture length.

  18. Truth and Lies About Hydraulic Fracturing By Terry Engelder

    E-print Network

    Engelder, Terry

    of the global pushback against hydraulic fracturing, commonly known as "fracking." This came as no surprise attention. At that time the term "fracing" or "fracking," was not part of the English language; within two fracturing, and most people now know what "fracking" is. In Europe, I was frequently asked, "How can you

  19. Studying Hydraulic Fracturing through Time-variant Seismic Anisotropy 

    E-print Network

    Liu, Qifan

    2013-10-01

    Hydraulic fracturing is an important modern technique of exploiting natural gas and oil, in which a high-pressure liquid mixture is injected into a wellbore to create small fractures in order to release fluids such as natural gas and petroleum...

  20. Evaluation of a downhole tiltmeter array for monitoring hydraulic fractures

    SciTech Connect

    Warpinski, N.R.; Engler, B.P.; Branagan, P.T.; Wilmer, R.; Wolhart, S.L.

    1997-03-01

    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.

  1. A Thermoelastic Hydraulic Fracture Design Tool for Geothermal Reservoir Development

    SciTech Connect

    Ahmad Ghassemi

    2003-06-30

    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.

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

    SciTech Connect

    Mineyuki Hanano; Tayuki Kondo

    1992-01-01

    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.

  3. An implicit level set method for modeling hydraulically driven fractures Anthony Peirce a,*, Emmanuel Detournay b

    E-print Network

    Peirce, Anthony

    An implicit level set method for modeling hydraulically driven fractures Anthony Peirce a the relevant tip asymptotics in hydraulic fracture simulators is critical for the accuracy and stability for a propagating hydraulic fracture. A number of char- acteristics of the governing equations for hydraulic

  4. Enrichment strategies and convergence properties of the XFEM for hydraulic fracture problems

    E-print Network

    Peirce, Anthony

    Enrichment strategies and convergence properties of the XFEM for hydraulic fracture problems Finite Ele- ment Method (XFEM) for modeling hydraulic fractures (HF), two classes of boundary value energy, is not suitable for modeling hydraulic fractures in which the uid and the fracture fronts

  5. Using seismic tomography to characterize fracture systems induced by hydraulic fracturing

    SciTech Connect

    Fehler, M.; Rutledge, J.

    1995-01-01

    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.

  6. Investigation of the influence of natural fractures and in situ stress on hydraulic fracture propagation using a

    E-print Network

    ARTICLE Investigation of the influence of natural fractures and in situ stress on hydraulic: Hydraulic fracturing is the primary means for enhancing rock mass permeability and improving well productiv- ity in tight reservoir rocks. Significant advances have been made in hydraulic fracturing theory

  7. Interference Fracturing: Non-Uniform Distributions of Perforation Clusters that Promote Simultaneous Growth of Multiple Hydraulic Fractures

    E-print Network

    Peirce, Anthony

    Simultaneous Growth of Multiple Hydraulic Fractures A.P. Peirce, University of British Columbia and A.P. Bunger hurdles in horizontal well stimulation is the generation of hydraulic fractures (HFs) from all perforation shadowing" that refers to suppression of some hydraulic fractures by the compressive stresses exerted

  8. Dynamic Response in Transient Stress-Field Behavior Induced by Hydraulic Fracturing

    NASA Astrophysics Data System (ADS)

    Jenkins, Andrew

    Hydraulic fracturing is a technique which is used to exploit geologic features and subsurface properties in an effort to increase production in low-permeability formations. The process of hydraulic fracturing provides a greater surface contact area between the producing formation and the wellbore and thus increases the amount of recoverable hydrocarbons from within the reservoir. The use of this stimulation technique has brought on massive applause from the industry due to its widespread success and effectiveness, however the dynamic processes that take part in the development of hydraulic fractures is a relatively new area of research with respect to the massive scale operations that are seen today. The process of hydraulic fracturing relies upon understanding and exploiting the in-situ stress distribution throughout the area of study. These in-situ stress conditions are responsible for directing fracture orientation and propagation paths throughout the period of injection. The relative magnitude of these principle stresses is key in developing a successful stimulation plan. In horizontal well plan development the interpretation of stress within the reservoir is required for determining the azimuth of the horizontal well path. These horizontal laterals are typically oriented in a manner such that the well path lies parallel to the minimum horizontal stress. This allows for vertical fractures to develop transversely to the wellbore, or normal to the least principle stress without the theoretical possibility of fractures overlapping, creating the most efficient use of the fluid energy during injection. The orientation and magnitude of these in-situ stress fields however can be dynamic, controlled by the subsequent fracture propagation and redistribution of the surrounding stresses. That is, that as the fracture propagates throughout the reservoir, the relative stress fields surrounding the fractures may see a shift and deviate from their original direction or magnitude. These types of shifts are of great concern because they can impact subsequent fracture development causing non-uniform fracture propagation and the potential overlapping of fracture paths as they extend from the wellbore at the point of injection. The dynamics of stress variation that occur with respect to hydraulic fracturing is a somewhat new area of study. In order to accomplish the goals of this thesis and continue future research in this area a new transient model has been developed in order to asses these dynamic systems and determine their influence on fracture behavior. This applies the use of a fully coupled finite element method in 2-D using linear elastic fracture mechanics which is then expanded using displacement discontinuity to a cohesive zone model in 3-D. A static boundary element model was also used to determine stress fields surrounding static, predetermined fracture geometries. These models have been verified against analytical solutions for simple cases and are now being applied to more detailed case studies and analysis. These models have been briefly discussed throughout this thesis in order to give insight on their current capabilities and application as well as their future potential within this area of research. The majority of this work introduces transient stress field prediction to cases of single and multiple hydraulic fractures. The static assessment of these stresses is determined for verification of results to those found in publication which leads into these transient stress field variations. A new method has been developed and applied to the stress state prediction for the first time in a transient fracture model which is partly based upon a critical distance theory. These dynamic interactions can provide useful insight to pertinent issues within the petroleum and natural gas industry such as those to hydraulic fracturing fluid loss and induced seismic events, as well as to applications of efficiency and optimization of the stimulation treatment plan.

  9. Advanced Hydraulic Fracturing Technology for Unconventional Tight Gas Reservoirs

    SciTech Connect

    Stephen Holditch; A. Daniel Hill; D. Zhu

    2007-06-19

    The objectives of this project are to develop and test new techniques for creating extensive, conductive hydraulic fractures in unconventional tight gas reservoirs by statistically assessing the productivity achieved in hundreds of field treatments with a variety of current fracturing practices ranging from 'water fracs' to conventional gel fracture treatments; by laboratory measurements of the conductivity created with high rate proppant fracturing using an entirely new conductivity test - the 'dynamic fracture conductivity test'; and by developing design models to implement the optimal fracture treatments determined from the field assessment and the laboratory measurements. One of the tasks of this project is to create an 'advisor' or expert system for completion, production and stimulation of tight gas reservoirs. A central part of this study is an extensive survey of the productivity of hundreds of tight gas wells that have been hydraulically fractured. We have been doing an extensive literature search of the SPE eLibrary, DOE, Gas Technology Institute (GTI), Bureau of Economic Geology and IHS Energy, for publicly available technical reports about procedures of drilling, completion and production of the tight gas wells. We have downloaded numerous papers and read and summarized the information to build a database that will contain field treatment data, organized by geographic location, and hydraulic fracture treatment design data, organized by the treatment type. We have conducted experimental study on 'dynamic fracture conductivity' created when proppant slurries are pumped into hydraulic fractures in tight gas sands. Unlike conventional fracture conductivity tests in which proppant is loaded into the fracture artificially; we pump proppant/frac fluid slurries into a fracture cell, dynamically placing the proppant just as it occurs in the field. From such tests, we expect to gain new insights into some of the critical issues in tight gas fracturing, in particular the roles of gel damage, polymer loading (water-frac versus gel frac), and proppant concentration on the created fracture conductivity. To achieve this objective, we have designed the experimental apparatus to conduct the dynamic fracture conductivity tests. The experimental apparatus has been built and some preliminary tests have been conducted to test the apparatus.

  10. Determining the distribution of hydraulic conductivity in a fractured limestone aquifer by simultaneous injection and geophysical logging

    USGS Publications Warehouse

    Morin, R.H.; Hess, A.E.; Paillet, F.L.

    1988-01-01

    A field technique for assessing the vertical distribution of hydraulic conductivity in an aquifer was applied to a fractured carbonate formation in southeastern Nevada. The technique combines the simultaneous use of fluid injection and geophysical logging to measure in situ vertical distributions of fluid velocity and hydraulic head down the borehole; these data subsequently are analyzed to arrive at quantitative estimates of hydraulic conductivity across discrete intervals in the aquifer. The results of this analysis identified the contact margin between the Anchor and Dawn Members of the Monte Cristo Limestone as being the dominant transmissive unit. -from Authors

  11. 77 FR 40354 - Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel Fuels-Draft

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-09

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

  12. Occupational exposures to respirable crystalline silica during hydraulic fracturing.

    PubMed

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

    2013-01-01

    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

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

    SciTech Connect

    Berryman, James G.

    2007-06-27

    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.

  14. 75 FR 36387 - Informational Public Meetings for Hydraulic Fracturing Research Study; Correction

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-25

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

  15. Water management in hydraulic fracturing-a planning and decision optimization platform

    E-print Network

    Mehta, Neha, S.M. Massachusetts Institute of Technology

    2014-01-01

    Recent developments in hydraulic fracturing technology have enabled cost-effective production of unconventional resources, particularly shale gas in the U.S. The process of hydraulic fracturing is water intensive, requiring ...

  16. Microcomputer models for the design of hydraulic fractures

    SciTech Connect

    Cleary, M.P.; Keck, R.G.; Mear, M.E.

    1983-03-01

    This paper describes approximate models which yield credible descriptions of hydraulic fracturing processes and are amenable to microprocessing calculation. Two levels of analysis are presented, lumped models, in which spatial variation is represented by integral coefficients; and more complex pseudo-threedimensional models, the main feature of which is a refined mesh that moves with the fracture. These models can compute such significant design evaluation quantities as length, height, width, and pressure variation with specified injection rate.

  17. The use of broadband microseisms for hydraulic fracture mapping

    SciTech Connect

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

    1993-08-01

    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.

  18. Laboratory hydraulic fracturing experiments in intact and pre-fractured rock

    USGS Publications Warehouse

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

    1977-01-01

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

  19. Experimental Investigation on the Basic Law of Hydraulic Fracturing After Water Pressure Control Blasting

    NASA Astrophysics Data System (ADS)

    Huang, Bingxiang; Li, Pengfeng; Ma, Jian; Chen, Shuliang

    2014-07-01

    Because of the advantages of integrating water pressure blasting and hydraulic fracturing, the use of hydraulic fracturing after water pressure control blasting is a method that is used to fully transform the structure of a coal-rock mass by increasing the number and range of hydraulic cracks. An experiment to study hydraulic fracturing after water pressure blasting on cement mortar samples (300 × 300 × 300 mm3) was conducted using a large-sized true triaxial hydraulic fracturing experimental system. A traditional hydraulic fracturing experiment was also performed for comparison. The experimental results show that water pressure blasting produces many blasting cracks, and follow-up hydraulic fracturing forces blasting cracks to propagate further and to form numerous multidirectional hydraulic cracks. Four macroscopic main hydraulic cracks in total were noted along the borehole axial and radial directions on the sample surfaces. Axial and radial main failure planes induced by macroscopic main hydraulic cracks split the sample into three big parts. Meanwhile, numerous local hydraulic cracks were formed on the main failure planes, in different directions and of different types. Local hydraulic cracks are mainly of three types: local hydraulic crack bands, local branched hydraulic cracks, and axial layered cracks. Because local hydraulic cracks produce multiple local layered failure planes and lamellar ruptures inside the sample, the integrity of the sample decreases greatly. The formation and propagation process of many multidirectional hydraulic cracks is affected by a combination of water pressure blasting, water pressure of fracturing, and the stress field of the surrounding rock. To a certain degree, the stress field of surrounding rock guides the formation and propagation process of the blasting crack and the follow-up hydraulic crack. Following hydraulic fracturing that has been conducted after water pressure blasting, the integrity of the sample is found to be far lower than after traditional hydraulic fracturing; moreover, both the water injection volume and water injection pressure for hydraulic fracturing after water pressure blasting are much higher than they are for traditional hydraulic fracturing.

  20. 77 FR 38024 - Oil and Gas; Well Stimulation, Including Hydraulic Fracturing, on Federal and Indian Lands

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-26

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

  1. Review article Induced seismicity and hydraulic fracturing for the recovery of

    E-print Network

    Foulger, G. R.

    Review article Induced seismicity and hydraulic fracturing for the recovery of hydrocarbons Richard mining (M 1.0e5.2); (h) geothermal operations (M 1.0e4.6) and (i) hydraulic fracturing for recovery seismicity occurs due to a reduction in effective stress on fault planes. Hydraulic fracturing operations can

  2. Coupling schemes for modeling hydraulic fracture propagation using the XFEM Elizaveta Gordeliy, Anthony Peirce

    E-print Network

    Peirce, Anthony

    Coupling schemes for modeling hydraulic fracture propagation using the XFEM Elizaveta Gordeliy August 2012 Accepted 18 August 2012 Available online 15 September 2012 Keywords: XFEM Hydraulic fractures and the Dirichlet to Neumann (DN) map with OðhÞ accuracy. For hydraulic fracture problems with a lag separating

  3. A Hybrid, Neuro-Genetic Approach to Hydraulic Fracture Treatment Design and Optimization

    E-print Network

    Mohaghegh, Shahab

    SPE 36602 A Hybrid, Neuro-Genetic Approach to Hydraulic Fracture Treatment Design and Optimization and novel methodology for optimal design of hydraulic fracture treatments in a gas storage field. What makes very little (almost none) reservoir data availability. Lack of engineering data for hydraulic fracture

  4. 2014-2015 Conference listing. 1. HYDRAULIC FRACTURING: FROM MODELING AND SIMULATION TO RECONSTRUCTION AND

    E-print Network

    Hutcheon, James M.

    Archives 2014-2015 Conference listing. 1. HYDRAULIC FRACTURING: FROM MODELING AND SIMULATION witnessed an enormous expansion of hydraulic fracturing (HF) in the subsurface as a tool to stimulate as to whether hydraulic fractures could breach the impermeable barriers that isolate aquifers from hydrocarbon

  5. On the moving boundary conditions for a hydraulic fracture Emmanuel Detournay a,b,

    E-print Network

    Peirce, Anthony

    On the moving boundary conditions for a hydraulic fracture Emmanuel Detournay a,b, , Anthony Peirce 2014 Keywords: Hydraulic fractures Speed equation Ill-posedness a b s t r a c t This paper re-examines the boundary conditions at the moving front of a hydraulic fracture when the fluid front has coalesced

  6. 40 CFR 147.52 - State-administered program-Hydraulic Fracturing of Coal Beds.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...State-administered program-Hydraulic Fracturing of Coal Beds. 147.52 Section 147.52 Protection...State-administered program—Hydraulic Fracturing of Coal Beds. The UIC program for hydraulic fracturing of coal beds in the State of Alabama,...

  7. 40 CFR 147.52 - State-administered program-Hydraulic Fracturing of Coal Beds.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...State-administered program-Hydraulic Fracturing of Coal Beds. 147.52 Section 147.52 Protection...State-administered program—Hydraulic Fracturing of Coal Beds. The UIC program for hydraulic fracturing of coal beds in the State of Alabama,...

  8. Trends in Hydraulic Fracturing Distributions and Treatment Fluids, Additives, Proppants, and Water Volumes Applied to

    E-print Network

    Trends in Hydraulic Fracturing Distributions and Treatment Fluids, Additives, Proppants, and Water.S. Geological Survey #12;Cover photos. U.S. hydraulic fracturing operation (front and back covers). Photos courtesy of Mark Engle, U.S. Geological Survey. #12;Trends in Hydraulic Fracturing Distributions

  9. International Journal of Rock Mechanics & Mining Sciences 44 (2007) 739757 Computer simulation of hydraulic fractures

    E-print Network

    Peirce, Anthony

    2007-01-01

    of hydraulic fractures J. Adachia , E. Siebritsb , A. Peircec,Ã, J. Desrochesd a Schlumberger Data 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

  10. 77 FR 67361 - Request for Information To Inform Hydraulic Fracturing Research Related to Drinking Water Resources

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-09

    ... AGENCY Request for Information To Inform Hydraulic Fracturing Research Related to Drinking Water... impacts of hydraulic fracturing on drinking water resources. DATES: EPA will accept data and literature in... scientific research to examine the relationship between hydraulic fracturing and drinking water...

  11. 75 FR 35023 - Informational Public Meetings for Hydraulic Fracturing Research Study

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-21

    ... AGENCY Informational Public Meetings for Hydraulic Fracturing Research Study AGENCY: Environmental... between hydraulic fracturing and drinking water. The meetings are open to all interested parties and will... Hydraulic Fracturing Study informational meetings are as follows: July 8, 2010, from 6 p.m. to 10 p.m.,...

  12. 78 FR 20637 - Notification of Public Meeting and a Public Teleconference of the Hydraulic Fracturing Research...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-05

    ... hydraulic fracturing on drinking water resources (77 FR 50505--50506). On November 27, 2012, the SAB Staff... AGENCY Notification of Public Meeting and a Public Teleconference of the Hydraulic Fracturing Research... teleconference of the Hydraulic Fracturing Research Advisory Panel to provide an opportunity for...

  13. 78 FR 25267 - Request for Information To Inform Hydraulic Fracturing Research Related to Drinking Water Resources

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-30

    ... AGENCY Request for Information To Inform Hydraulic Fracturing Research Related to Drinking Water... research on the potential impacts of hydraulic fracturing on drinking water resources from April 30, 2013... research to examine the relationship between hydraulic fracturing and drinking water resources. The...

  14. Analytic crack solutions for tilt fields around hydraulic fractures

    SciTech Connect

    Warpinski, N.R.

    2000-01-05

    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.

  15. Reply: Davies et al. (2012), Hydraulic fractures: How far can they go? Richard J. Davies a,*, Gillian R. Foulger a

    E-print Network

    Foulger, G. R.

    2012-01-01

    contamination of drinking water in the USA and to provide an evidence base for the safe vertical separation propagating stimulated hydraulic fractures, gener- ated by fracking operations for gas and oil exploitation to be 588 m in height. This provided a rationale for an initial, safe separation distance of 600 m between

  16. Northwestern University Technological Institute Tight Shale Gas-Hydraulic Fracturing

    E-print Network

    Guo, Dongning

    Northwestern University Technological Institute Tight Shale Gas-Hydraulic Fracturing Seminar Series Where are we Today: Reservoir and Completion Quality Is Tight Shale Gas and Oil the Answer ? Sidney and with different economic and environmental impacts · Tight Shale Gas and Oil is at least part of the answer

  17. Water Use for Hydraulic Fracturing: A Texas Sized Problem? 

    E-print Network

    LeClere, David

    2014-01-01

    The state of Texas could face a 2.7 trillion gallon shortfall of water by 2060. Hydraulic fracturing (HF) requires large amounts of water for each well. Tax incentives should be offered to companies that substitute brackish groundwater for fresh...

  18. Identification of Successful Practices in Hydraulic Fracturing Using

    E-print Network

    Mohaghegh, Shahab

    1 Identification of Successful Practices in Hydraulic Fracturing Using Intelligent Data Mining a methodology to identify the successful practices in oil and gas related operations. Apply the methodology;SPE 77597, Mohaghegh, Popa, Gaskari, Ameri & Wolhart 6 METHODOLOGY The process of "Successful

  19. 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...

  20. Estimation of Hydraulic Fracturing in the Earth Fill Dam by 3-D Analysis

    NASA Astrophysics Data System (ADS)

    Nishimura, Shin-Ichi

    It is necessary to calculate strength and strain for estimation of hydraulic fracturing in the earth fill dam, and to which the FEM is effective. 2-D analysis can produce good results to some extent if an embankment is linear and the plain strain condition can be set to the cross section. However, there may be some conditions not possible to express in the 2-D plain because the actual embankment of agricultural reservoirs is formed by straight and curved lines. Moreover, it may not be possible to precisely calculate strain in the direction of dam axis because the 2-D analysis in the cross section cannot take the shape in the vertical section into consideration. Therefore, we performed 3-D built up analysis targeting the actually-leaked agricultural reservoir to examine hazards of hydraulic fracturing based on the shape of an embankment and by rapid impoundment of water. It resulted in the occurrence of hydraulic fracturing to develop by water pressure due to the vertical cracks caused by tensile strain in the valley and refractive section of the foundation.

  1. Numerical Modeling of Fluid Migration and Propagation of Multiple Hydraulic Fractures in Crystalline Geothermal Reservoir

    NASA Astrophysics Data System (ADS)

    Yoon, Jeoung Seok; Zang, Arno; Zimmermann, Günter; Stephansson, Ove; Min, Ki-Bok

    2015-04-01

    This paper presents discrete element based numerical model which is applied to simulation of multiple stage hydraulic fracturing in crystalline granitic geothermal reservoir. Target site modeled locates in south of state of Saxony Germany. Particle Flow Code 2D (Itasca) is used in which fluid flow algorithm and moment tensor based seismicity computation algorithm are implemented. Crystalline rock layer to be stimulated locates at 4-6 km depth with relative low density of pre-existing joints and faults. Hydraulic stimulation is modeled with five stages of fluid injection with distance of several hundreds of meters. Hydraulic fracturing is done on the stages from toe to heel direction along a series of sub-horizontally drilled wellbore with constant rate of fluid injection. Fracture propagation paths and induced seismic events are documented based on their time of occurrence and their magnitude. In addition to the evolution of the fracture propagation path and distribution of the induced events, migration of the injected fluid is investigated in space and time. This is to see how the results relate to the fluid migration front in low permeability crystalline reservoir subjected to multiple stage hydraulic fracturing. Moreover, this paper addresses advantages and disadvantages of the inclined drilling of the wellbore in low permeability reservoir and multi-stage fracturing setting. We try to seek an optimum inclination of the drilling in relation to the gradients and magnitudes of the in situ stresses, which are horizontal minimum and vertical stresses. Preliminary modeling results show that inclination angle of the drilling has a significant effect on lowering of the stress shadow effect and level of induced seismicity in terms of total number, magnitudes and the Gutenberg-Richter relation.

  2. Hydraulic Aperture Reduction of Shale Fractures Due to Mechanical Stressing, with Characterization of Physical Fracture Evolution Using Comuted Tomography

    NASA Astrophysics Data System (ADS)

    Crandall, D.; Gill, M.; Moore, J.

    2014-12-01

    Flow in fractured shale is a topic of interest for both production from non-traditional fractured shale reservoirs and for estimating the leakage potential of sealing formations above geologic carbon dioxide repositories. The hydraulic aperture of a fracture quantifies how much fluid can be transported through a fracture, similarly to how permeability describes fluid flow through porous media. The advantage of defining the fracture hydraulic aperture as opposed to permeability, is that this property can be easily scaled up to fracture reservoir simulators. Many parameters affect the hydraulic aperture, however, including the fracture roughness, the physical aperture distribution, and the tortuosity of flow paths within the fracture.The computed tomography (CT) and flow facility at NETL has conducted an analysis of the changes in both physical and hydraulic aperture as fractures were subjected to varying external confining stresses. Changes in fracture geometry were tracked through the use of non-destructive CT imaging, allowing the determination of the physical aperture distribution, while hydraulic fracture apertures were derived from experimental fracture flow measurements. In order to evaluate the effects of fracture roughness and geometry, two fractures with different degrees of roughness were used. Tests were conducted with locally sourced shale.Experimental results show that the volume change in the fracture is a non-linear function of the confining pressure, and both physical and hydraulic apertures decrease rapidly as the fracture is first compressed.

  3. Effects of non-Darcy flow on pressure buildup analysis of hydraulically fractured gas reservoirs 

    E-print Network

    Alvarez Vera, Cesar

    2001-01-01

    Conventional well-testing techniques are commonly used to evaluate pressure transient tests of hydraulically fractured wells to estimate values such as formation permeability, fracture length, and fracture conductivity. When non-Darcy flow occurs...

  4. Imaging Hydraulic Fractures: Source Location Uncertainty Analysis At The UPRC Carthage Test Site

    E-print Network

    Li, Yingping

    1996-01-01

    Hydraulic fracturing is a useful tool for enhancing gas and oil production. High-resolution seismic imaging of the fracture geometry and fracture growth process is the key in determining optimal spacing and location of ...

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

    NASA Astrophysics Data System (ADS)

    Lipovsky, Bradley P.; Dunham, Eric M.

    2015-02-01

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

  6. Hydraulic Fracture: multiscale processes and moving

    E-print Network

    Peirce, Anthony

    of Mathematics University of British Columbia WORKSHOP ON ROCK MECHANICS AND LOGISTICS IN MINING February 26 and physical processes Fracture Energy Breaking rock Leak-off Viscous energy loss #12;8 Scaling s olution time 2.58 hours BiCGS TAB-MG V(0,2) cycle : Total s olution time 0.27 hours BiCGS TAB-MG V(1

  7. Aerobic biodegradation of organic compounds in hydraulic fracturing fluids.

    PubMed

    Kekacs, Daniel; Drollette, Brian D; Brooker, Michael; Plata, Desiree L; Mouser, Paula J

    2015-07-01

    Little is known of the attenuation of chemical mixtures created for hydraulic fracturing within the natural environment. A synthetic hydraulic fracturing fluid was developed from disclosed industry formulas and produced for laboratory experiments using commercial additives in use by Marcellus shale field crews. The experiments employed an internationally accepted standard method (OECD 301A) to evaluate aerobic biodegradation potential of the fluid mixture by monitoring the removal of dissolved organic carbon (DOC) from an aqueous solution by activated sludge and lake water microbial consortia for two substrate concentrations and four salinities. Microbial degradation removed from 57 % to more than 90 % of added DOC within 6.5 days, with higher removal efficiency at more dilute concentrations and little difference in overall removal extent between sludge and lake microbe treatments. The alcohols isopropanol and octanol were degraded to levels below detection limits while the solvent acetone accumulated in biological treatments through time. Salinity concentrations of 40 g/L or more completely inhibited degradation during the first 6.5 days of incubation with the synthetic hydraulic fracturing fluid even though communities were pre-acclimated to salt. Initially diverse microbial communities became dominated by 16S rRNA sequences affiliated with Pseudomonas and other Pseudomonadaceae after incubation with the synthetic fracturing fluid, taxa which may be involved in acetone production. These data expand our understanding of constraints on the biodegradation potential of organic compounds in hydraulic fracturing fluids under aerobic conditions in the event that they are accidentally released to surface waters and shallow soils. PMID:26037076

  8. Hydraulic Fracture: multiscale processes and moving

    E-print Network

    Peirce, Anthony

    model and physical processes Fracture Energy Breaking rock Leak-off Viscous energy loss #12;9 Scaling) CumulativeSolutionTime(hours) BiCGS TAB : Total s olution time 2.58 hours BiCGS TAB-MG V(0,2) cycle : Total s olution time 0.27 hours BiCGS TAB-MG V(1,2) cycle : Total s olution time 0.31 hours 1 1.5 2 2.5 3 3.5 4 0

  9. On modeling hydraulic fracture in proper variables: stiffness, accuracy, sensitivity

    E-print Network

    Mishuris, Gennady; Linkov, Alexander

    2012-01-01

    The problem of hydraulic fracture propagation is considered by using its recently suggested modified formulation in terms of the particle velocity, the opening in the proper degree, appropriate spatial coordinates and $\\varepsilon$-regularization. We show that the formulation may serve for significant increasing the efficiency of numerical tracing the fracture propagation. Its advantages are illustrated by re-visiting the Nordgren problem. It is shown that the modified formulation facilitates (i) possibility to have various stiffness of differential equations resulting after spatial discretization, (ii) obtaining highly accurate and stable numerical results with moderate computational effort, and (iii) sensitivity analysis. The exposition is extensively illustrated by numerical examples.

  10. Numerical Simulation of Potential Groundwater Contaminant Pathways from Hydraulically Fractured Oil Shale in the Nevada Basin and Range Province

    NASA Astrophysics Data System (ADS)

    Rybarski, S.; Pohll, G.; Pohlmann, K.; Plume, R.

    2014-12-01

    In recent years, hydraulic fracturing (fracking) has become an increasingly popular method for extraction of oil and natural gas from tight formations. Concerns have been raised over a number of environmental risks associated with fracking, including contamination of groundwater by fracking fluids, upwelling of deep subsurface brines, and methane migration. Given the potentially long time scale for contaminant transport associated with hydraulic fracturing, numerical modeling remains the best practice for risk assessment. Oil shale in the Humboldt basin of northeastern Nevada has now become a target for hydraulic fracturing operations. Analysis of regional and shallow groundwater flow is used to assess several potential migration pathways specific to the geology and hydrogeology of this basin. The model domain in all simulations is defined by the geologic structure of the basin as determined by deep oil and gas well bores and formation outcrops. Vertical transport of gaseous methane along a density gradient is simulated in TOUGH2, while fluid transport along faults and/or hydraulic fractures and lateral flow through more permeable units adjacent to the targeted shale are modeled in FEFLOW. Sensitivity analysis considers basin, fault, and hydraulic fracturing parameters, and results highlight key processes that control fracking fluid and methane migration and time scales under which it might occur.

  11. Borehole deviation surveys are necessary for hydraulic fracture monitoring Leo Eisner, Schlumberger Cambridge Research, Petr Bulant, Charles University in Prague, Jol H. Le Calvez*,

    E-print Network

    Cerveny, Vlastislav

    Borehole deviation surveys are necessary for hydraulic fracture monitoring Leo Eisner, Schlumberger Not performing accurate borehole deviation surveys for hydraulic fracture monitoring (HFM) and neglecting fracture parameters. Introduction Recently a large number of hydraulic fracture treatments have been

  12. A PKN Hydraulic Fracture Model Study and Formation Permeability Determination 

    E-print Network

    Xiang, Jing

    2012-02-14

    &M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Approved by: Chair of Committee, Ahmad Ghassemi Committee Members, Stephen A. Holditch Vikram Kinra Head of Department, Stephen A. Holditch December... 2011 Major Subject: Petroleum Engineering iii ABSTRACT A PKN Hydraulic Fracture Model Study and Formation Permeability Determination. (December 2011) Jing Xiang, B.S., China University of Petroleum Chair of Advisory Committee: Dr. Ahmad...

  13. Mathematical modeling of hydraulic fracturing in coal seams

    SciTech Connect

    Olovyanny, A.G.

    2005-02-01

    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.

  14. Interpretation of resonance frequencies recorded during hydraulic fracturing treatments

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    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.

  15. Implicit level set schemes for modeling hydraulic fractures using the Elizaveta Gordeliy, Anthony Peirce

    E-print Network

    Peirce, Anthony

    Implicit level set schemes for modeling hydraulic fractures using the XFEM Elizaveta Gordeliy Copyright Ó 2013 Published by Elsevier B.V. All rights reserved. 1. Introduction Hydraulic fractures (HF form 13 July 2013 Accepted 27 July 2013 Available online 20 August 2013 Keywords: XFEM Hydraulic

  16. Interaction between Injection Points during Hydraulic Fracturing Kjetil M. D. Hals1,

    E-print Network

    Santos, Juan

    Interaction between Injection Points during Hydraulic Fracturing Kjetil M. D. Hals1, and Inga Berre between two injection points during hydraulic fracturing (hydrofracking) and how this interaction of Mathematics, University of Bergen, P.O. Box 7800, NO-5020 Bergen, Norway. We present a model of the hydraulic

  17. New Tracers Identify Hydraulic Fracturing Fluids and Accidental Releases from Oil and Gas Operations

    E-print Network

    Jackson, Robert B.

    New Tracers Identify Hydraulic Fracturing Fluids and Accidental Releases from Oil and Gas fingerprints of fluids that return to the surface after high volume hydraulic fracturing of unconventional oil elemental and isotopic signatures (B/Cl, Li/Cl, 11 B, and 7 Li) useful for characterizing hydraulic

  18. Hydraulic fracture characterization resulting from low-viscosity fluid injection: Implications for CO2 sequestration

    NASA Astrophysics Data System (ADS)

    Burbey, T. J.; Zhou, X.

    2013-12-01

    The initiation of hydraulic fractures during CO2 sequestration can be either engineered or induced unintentionally. Some fractures may be desirable such as horizontal fractures that can facilitate fluid injection and migration; whereas some fractures may be unfavorable if the fractures tend to extend vertically above a certain limit, thus creating a potential leaking condition. Historically, carbon dioxide as a liquefied gas has been used in oil and gas field stimulation since the early1960s because it eliminates formation damage and residual fluids. Carbon dioxide injection is considered to be one of the most effective technologies for improving oil recovery from hard-to-extract oil reserves because CO2 is effective in penetrating the formation due to its high diffusivity, while the rock associated with petroleum-containing formations is generally porous. However, low viscosity and high compressibility fluids such as CO2 exhibit different effects on the hydraulic fracture initiation/propagation behavior in comparison with high viscosity and low compressibility fluids. Laboratory tests show that viscous fluids tend to generate thick and planar cracks with few branches, while low viscosity fluids tend to generate narrow and wavelike cracks with many secondary branches. A numerical comparison between water and supercritical CO2-like fluid has been made to investigate the influence of fluids to fracture propagation behavior. Simulation results indicate that the pore pressure fields are very different for different pore fluids even when the initial field conditions and injection schemes (rate and time) are kept the same. Thin fluids with properties of supercritical CO2 will create relatively thin and much shorter fractures in comparison to fluids exhibiting properties of water under similar injection schemes. Two significant times are recognized during fracture propagation. One is the time at which a crack ceases opening, and he other is the time at which a crack ceases propagating, with the former always occurring before the latter. These times are very different for different fluids. Both fluid compressibility and viscosity are important in the behavior of fracture propagation with viscosity being the most important property. Viscosity can greatly affect the magnitude of hydraulic conductivity and the value of the leak-off coefficient. This study has important implications for CO2 sequestration.

  19. Are sills really elastic hydraulic fractures?

    NASA Astrophysics Data System (ADS)

    Spacapan, Juán B.; Galland, Olivier; Leanza, Héctor A.; Planke, Sverre

    2015-04-01

    Seismic reflection data and field observations have over the past few decades revealed the presence of voluminous igneous sill complexes in sedimentary basins worldwide. The implications of sill emplacement in sedimentary basins are numerous: they trigger maturation of organic-rich formations, they produce large quantities of greenhouse gases that trigger dramatic climate change and mass extinctions, and they produce small- and large-scale structures that affect fluid flow. Therefore, a proper understanding of their emplacement mechanism is essential. Most models of sill and laccolith emplacement account for purely elastic host rock, and their propagation mechanism is dominantly assumed to be according to the Linear Elastic Fracture Mechanics (LEFM) theory. Recent field and seismic observations, however, demonstrated that part, if not all, sill- and laccolith-induced deformation is accommodated by inelastic deformation, strongly questioning the relevance of the LEFM theory applied for igneous intrusions. In this contribution, we present detailed structural observations from spectacularly well-exposed sills in the northern Neuquén Basin, Argentina. We studied a 50-m outcrop that exhibits very clearly three sills of different sizes, the shapes of their tips, and the associated structures in their sedimentary host rock, i.e. the calcareous pelites of the organic-rich Vaca Muerta Fm. This formation is adequate to map the structures at the outcrop scale, as it consists in fine layers of mudstone inter-bedded with weak shale, such that it is possible to map each layer along the entire outcrop. Detailed structural mapping evidence that the sedimentary layers have not been opened, i.e. pushed away by the emplacement of the sills, as expected from the LEFM theory. Indeed, some of the sedimentary layers are not present at the location of the sills, but they appear duplicated several times ahead of the tips of the three observed sills; the relative movements between the duplicated segments are clearly associated with shortening. Therefore, our field observations show that the host rock is pushed and shortened ahead of the sill tips, in total contradiction with the extensional features predicted by the LEFM theory. The structures described above strongly suggest instead that these sills were emplaced according to the viscous indenter model, in good agreement with recent laboratory models (Abdelmalak et al., 2012). These detailed observations strongly question the geological relevance of the LEFM theory applied to igneous sheet intrusions, and call for more field observations to better constrain the dynamics of sill and dyke emplacement mechanisms. Abdelmalak, M.M., Mourgues, R., Galland, O., Bureau, D., 2012. Fracture mode analysis and related surface deformation during dyke intrusion: Results from 2D experimental modelling. Earth Planet. Sci. Lett. 359-360, 93-105.

  20. Investigation of the effect of gel residue on hydraulic fracture conductivity using dynamic fracture conductivity test 

    E-print Network

    Marpaung, Fivman

    2009-05-15

    The key to producing gas from tight gas reservoirs is to create a long, highly conductive flow path, via the placement of a hydraulic fracture, to stimulate flow from the reservoir to the wellbore. Viscous fluid is used to transport proppant...

  1. Anaerobic Biodegradation of Ethylene Glycol within Hydraulic Fracturing Fluid

    NASA Astrophysics Data System (ADS)

    Heyob, K. M.; Mouser, P. J.

    2014-12-01

    Ethylene glycol (EG) is a commonly used organic additive in hydraulic fracturing fluids used for shale gas recovery. Under aerobic conditions, this compound readily biodegrades to acetate and CO2 or is oxidized through the glycerate pathway. In the absence of oxygen, organisms within genera Desulfovibrio, Acetobacterium, and others can transform EG to acetaldehyde, a flammable and suspected carcinogenic compound. Acetaldehyde can then be enzymatically degraded to ethanol or acetate and CO2. However, little is known on how EG degrades in the presence of other organic additives, particularly under anaerobic conditions representative of deep groundwater aquifers. To better understand the fate and attenuation of glycols within hydraulic fracturing fluids we are assessing their biodegradation potential and pathways in batch anaerobic microcosm treatments. Crushed Berea sandstone was inoculated with groundwater and incubated with either EG or a synthetic fracturing fluid (SFF) containing EG formulations. We tracked changes in dissolved organic carbon (DOC), EG, and its transformation products over several months. Approximately 41% of bulk DOC in SFF is degraded within 21 days, with 58% DOC still remaining after 63 days. By comparison, this same SFF degrades by 70% within 25 days when inoculated with sediment-groundwater microbial communities, suggesting that bulk DOC degradation occurs at a slower rate and to a lesser extent with bedrock. Aerobic biodegradation of EG occurs rapidly (3-7 days); however anaerobic degradation of EG is much slower, requiring several weeks for substantial DOC loss to be observed. Ongoing experiments are tracking the degradation pathways of EG alone and in the presence of SFF, with preliminary data showing incomplete glycol transformation within the complex hydraulic fracturing fluid mixture. This research will help to elucidate rates, processes, and pathways for EG biodegradation and identify key microbial taxa involved in its degradation.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  3. Hydraulic fracturing is an effective technique used in well stimulation to increase petroleum well production. A combination of multi-stage hydraulic fracturing and horizontal drilling has led to the

    E-print Network

    Hydraulic fracturing is an effective technique used in well stimulation to increase petroleum well production. A combination of multi-stage hydraulic fracturing and horizontal drilling has led to the recent of a fracture. In this thesis, we study the stress distribution around a hydraulic fracture caused by fluid

  4. Constraints on upward migration of hydraulic fracturing fluid and brine.

    PubMed

    Flewelling, Samuel A; Sharma, Manu

    2014-01-01

    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

  5. Constraints on Upward Migration of Hydraulic Fracturing Fluid and Brine

    PubMed Central

    Flewelling, Samuel A; Sharma, Manu

    2014-01-01

    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 >106?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

  6. A decision-analytic approach to predict state regulation of hydraulic fracturing

    E-print Network

    Linkov, Igor

    Background: The development of horizontal drilling and hydraulic fracturing methods has dramatically increased the potential for the extraction of previously unrecoverable natural gas. Nonetheless, the potential risks and ...

  7. Predicting hydraulic tensile fracture spacing in strata-bound systems$ C.I. McDermott n

    E-print Network

    Haszeldine, Stuart

    Predicting hydraulic tensile fracture spacing in strata-bound systems$ C.I. McDermott n , K June 2013 Available online 15 July 2013 Keywords: Hydraulic fracturing Fracture spacing CO2 analogue that hydraulic fracturing can be expected in the lower layers of a caprock after a relatively short period

  8. Hydraulic fracturing in faulted sedimentary basins: Numerical simulation of potential contamination of shallow aquifers over long

    E-print Network

    fracturing (hydrofracturing or ``fracking'') is generally used [BAPE, 2011; EPA, 2012]. Hydraulic fracturing, which returns to the surface [Gregory et al., 2001]. The fracking fluid is commonly composed of $99

  9. A New Analytical Method to Quantify Residual Fluid Cleanup in Hydraulic Fractures 

    E-print Network

    Zarrin, Tahira

    2014-04-17

    A number of factors contribute to reduce the production benefits from hydraulic fracturing, including inefficient fluid design, poor proppant selection and or, the inability of fracture fluid to degrade and flow back after treatment. Undegraded...

  10. Development, setup and testing of a dynamic hydraulic fracture conductivity apparatus 

    E-print Network

    Pongthunya, Potcharaporn

    2009-06-02

    One of the most critical parameters in the success of a hydraulic fracturing treatment is to have sufficiently high fracture conductivity. Unbroken polymers can cause permeability impairment in the proppant pack and/or in the matrix along...

  11. The Effect of Proppant Size and Concentration on Hydraulic Fracture Conductivity in Shale Reservoirs 

    E-print Network

    Kamenov, Anton

    2013-04-11

    the surface area of the formation that is connected to the wellbore. These highly conductive fractures significantly increase the production rates of petroleum fluids. During the process of hydraulic fracturing proppant is pumped and distributed...

  12. 3D geostatistical modeling of fracture system in a granitic massif to characterize hydraulic properties and fracture distribution

    NASA Astrophysics Data System (ADS)

    Koike, Katsuaki; Kubo, Taiki; Liu, Chunxue; Masoud, Alaa; Amano, Kenji; Kurihara, Arata; Matsuoka, Toshiyuki; Lanyon, Bill

    2015-10-01

    This study integrates 3D models of rock fractures from different sources and hydraulic properties aimed at identifying relationships between fractures and permeability. The Tono area in central Japan, chiefly overlain by Cretaceous granite, was examined because of the availability of a unique dataset from deep borehole data at 26 sites. A geostatistical method (GEOFRAC) that can incorporate orientations of sampled data was applied to 50,900 borehole fractures for spatial modeling of fractures over a 12 km by 8 km area, to a depth of 1.5 km. GEOFRAC produced a plausible 3D fracture model, in that the orientations of simulated fractures correspond to those of the sample data and the continuous fractures appeared near a known fault. Small-scale fracture distributions with dominant orientations were also characterized around the two shafts using fracture data from the shaft walls. By integrating the 3D model of hydraulic conductivity using sequential Gaussian simulation with the GEOFRAC fractures from the borehole data, the fracture sizes and directions that strongly affect permeable features were identified. Four fracture-related elements: lineaments from a shaded 10-m DEM, GEOFRAC fractures using the borehole and shaft data, and microcracks from SEM images, were used for correlating fracture attributes at different scales. The consistency of the semivariogram models of distribution densities was identified. Using an experimental relationship between hydraulic conductivity and fracture length, the fractures that typically affect the hydraulic properties at the drift scale were surmised to be in the range 100-200 m. These results are useful for a comprehensive understanding of rock fracture systems and their hydraulic characteristics at multiple scales in a target area.

  13. Hydraulic Fracturing, Wastewater Injection and Unintended Earthquakes (Invited)

    NASA Astrophysics Data System (ADS)

    Ellsworth, W. L.

    2013-12-01

    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.

  14. Hydraulic Fracturing Treatment Controls on Induced Microseismicity Attributes

    NASA Astrophysics Data System (ADS)

    Reyes-Montes, J. M.; Kelly, C.; Huang, J.; Zhao, X.; Young, R. P.

    2014-12-01

    Hydraulic fracturing imposes stress changes in the treated rock through the injection of a mix of fluid and proppant at variable rates and can result in stimulated microseismicity (induced or triggered) with a wide range of magnitudes associated to the opening of new cracks or the mobilisation of pre-existing fractures. Optimizing the treatment is vital for the economic and sustainable development of hydrocarbon reservoir and for the minimization of potential environmental impacts. The analysis of the induced seismicity and of event parameters provide an estimate of the effect of the treatment and the extent of the changes in the rock reservoir properties affecting fluid conductivity. This gives critical feedback for the optimization of the treatment, especially during real-time monitoring. In this study, we correlate microseismic attributes such as the fracture dimensions, event distribution and b-values with the fluid treatment parameters such as the pumping pressure and the slurry rate across different reservoir treatments. Although the microseismic attributes are influenced by many different factors such as the reservoir elastic properties, the stress regime and in-situ fracturing, we consistently observed positive correlations between the slurry rate, plateau treatment pressure and the fracture dimensions. In addition, the variation and systematic deviation of b-value from the natural average of 1.0 gives an insight into the geomechanical behavior of the reservoir. Similar to b-value, another fractal dimension, D-value, indicates the fracture spatial propagation from linear advancement (D=1.0) to planar distribution (D=2.0) to full space occurrence (D=3.0). By merging microseismic events from multiple treatment stages, we statistically analyzed magnitude distribution and spatial and temporal structure of the microseismic cloud induced during the stimulation of a range of different reservoirs with a total population of ~20,000 MS events. Analysis on multiple treatment projects can provide a first order guidance on selecting optimal treatment parameters.

  15. 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...

  16. Fate of hydraulic fracturing chemicals under down-hole conditions

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  17. Economic reocvery of oil trapped at fan margins using high angle wells and multiple hydraulic fractures. Quarterly report, July 1 - September 30, 1996

    SciTech Connect

    Niemeyer, B.L.

    1996-10-01

    This project attempts to demonstrate the effectiveness of exploiting thin-layered, low-energy deposits at the distal margin of a prograding turbitide complex through the use of hydraulically- fractured, horizontal, or high-angle wells. The combination of 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. The fine-grid reservoir simulation of the northeast fan-margin region of the Yowlumne field was completed during third quarter 1996. A variety of development alternatives were investigated aimed at optimizing project economics. Model forecasts, compared slant well performance to more conventional development options and quantified rate impacts due to changes in well location, orientation, and completion technique. Project economics were then updated with the production forecasts from the simulation model.

  18. 78 FR 34611 - Oil and Gas; Hydraulic Fracturing on Federal and Indian Lands

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-10

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

  19. 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...

  20. Microseismic mapping of a Cotton Valley hydraulic fracture using decimated downhole arrays J.T. Rutledge

    E-print Network

    Microseismic mapping of a Cotton Valley hydraulic fracture using decimated downhole arrays J three hydraulic fracture operations in the Cotton Valley gas field of East Texas. Two 48-level, 3 in the Cotton Valley gas field of East Texas (Walker, 1997). The Cotton Valley Project was an important test

  1. Hydraulics of horizontal wells in fractured shallow aquifer systems Eungyu Parka,*, Hongbin Zhanb

    E-print Network

    Zhan, Hongbin

    Hydraulics of horizontal wells in fractured shallow aquifer systems Eungyu Parka,*, Hongbin Zhanb Accepted 1 May 2003 Abstract An analysis of groundwater hydraulic head in the vicinity of a horizontal well in fractured or porous aquifers considering confined, leaky confined, and water-table aquifer boundary

  2. 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...

  3. 78 FR 31635 - Oil and Gas; Hydraulic Fracturing on Federal and Indian Lands

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-24

    ...; Well Stimulation, Including Hydraulic Fracturing, on Federal and Indian Lands'' (77 FR 27691). The... 60 days (77 FR 38024). The extended comment period closed on September 10, 2012. The BLM received...; Hydraulic Fracturing on Federal and Indian Lands; Proposed Rule #0;#0;Federal Register / Vol. 78 , No....

  4. Compilation of Physicochemical and Toxicological Information About Hydraulic Fracturing-Related Chemicals (Draft Database)

    EPA Science Inventory

    The purpose of this product is to make accessible the information about the 1,173 hydraulic fracturing-related chemicals that were listed in the external review draft of the Hydraulic Fracturing Drinking Water Assessment that was released recently. The product consists of a serie...

  5. 75 FR 36387 - Informational Public Meetings for Hydraulic Fracturing Research Study; Correction

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-25

    ..., 2010, in FR doc. 2010-14897, on page 35023, in the third Column, correct the Web site addresses shown... AGENCY Informational Public Meetings for Hydraulic Fracturing Research Study; Correction AGENCY... Hydraulic Fracturing Research Study. The document contained an incorrect EPA Web site address in two...

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

    USGS Publications Warehouse

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

    2000-01-01

    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.

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

    PubMed

    Ren, Lan; Zhao, Jinzhou; Hu, Yongquan

    2014-01-01

    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

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

    PubMed Central

    Ren, Lan; Zhao, Jinzhou; Hu, Yongquan

    2014-01-01

    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

  9. Solution of hydraulic fracture problem accounting for lag

    E-print Network

    Linkov, Alexander M

    2014-01-01

    The paper presents a method for solving hydraulic fracture problems accounting for the lag. The method consists in matching the outer (basic) solution neglecting the lag, with the inner (auxiliary) solution of the derived 1D integral equation with conditions, accounting for the lag and asymptotic behavior of the opening and the net-pressure. The method refers to practically important cases, when the influence of the local perturbation, caused by the lag, becomes insignificant at a distance, where the leading plane-state asymptotics near the fracture front is still applicable. The universal asymptotics are used for finding the matching constants of the basic (outer) solution and for formulation of matching condition for the solution of inner (auxiliary) problem. The method is illustrated by the solution of the Spence and Sharp plane-strain problem for a fracture propagating symmetrically from the inlet, where a Newtonian fluid is pumped at a constant rate. It is stated that the method developed for deep fractu...

  10. In-situ stress from hydraulic fracture measurements in G Tunnel, Nevada Test Site

    SciTech Connect

    Smith, C.; Vollendorf, W. C.; Warren, W. E.

    1981-04-01

    Hydraulic fracture work in G Tunnel, Nevada Test Site, performed to obtain the in-situ stress state is discussed. Field equipment and procedures are described; analysis is developed to relate the hydraulic fracture pressures to the in-situ stress state. Pressure data are analyzed to provide estimates of the stress state at a number of locations in the tunnel complex. A unique feature of the work is the mineback - a mining process in which the rock is cut away to reveal the actual plane of the fracture. Advantages, limitations, and problem areas associated with extracting in-situ stress fields from hydraulic fracture pressure records are discussed in detail.

  11. Direct Imaging of Natural Fractures and Stress Compartments Stimulated by Hydraulic Fracturing

    NASA Astrophysics Data System (ADS)

    Lacazette, A.; Vermilye, J. M.

    2014-12-01

    This contribution will present results from passive seismic studies of hydraulic fracture treatments in North American and Asian basins. One of the key data types is a comparatively new surface-based seismic imaging product - "Tomographic Fracture Images®" (TFI®). The procedure is an extension of Seismic Emission Tomography (SET), which is well-established and widely used. Conventional microseismic results - microearthquake hypocenter locations, magnitudes, and focal mechanism solutions - are also obtained from the data via a branch of the processing workflow. TFI is accomplished by summing the individual time steps in a multidimensional SET hypervolume over extended periods of time, such as an entire frac stage. The dimensions of a SET hypervolume are the X, Y, and Z coordinates of the voxels, the time step (typically on the order of 100 milliseconds), and the seismic activity value. The resulting summed volume is skeletonized to produce images of the main fracture surfaces, which are known to occupy the maximum activity surfaces of the high activity clouds from theory, field studies, and experiments. The orientation vs. area of the resulting TFIs can be analyzed in detail and compared with independent data sets such as volumetric structural attributes from reflection seismic data and borehole fracture data. We find that the primary effect of hydraulic fracturing is to stimulate preexisting natural fracture networks and faults. The combination of TFIs with hypocenter distributions and microearthquake focal mechanisms provides detailed information on subsurface stress compartmentalization. Faults are directly imaged which allows discrimination of fault planes from auxiliary planes of focal mechanism solutions. Examples that will be shown include simultaneous movement on a thrust fault and tear fault and examples of radically different stress compartments (e.g. extensional vs. wrench faulting) stimulated during a single hydraulic fracture treatment. The figure shows a TFI of a single frac stage in the Eagle Ford FmFm that is unusually symmetrical and smooth near the perforations. Color shows intensity of cumulative seismic activity (red = high, violet = low). Note that the energy decreases and the complexity increases as the frac quenches in the natural fracture system.

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

    NASA Astrophysics Data System (ADS)

    Cai, Zuansi; Ofterdinger, Ulrich

    2014-07-01

    Natural gas extracted from hydraulically fractured shale formations potentially has a big impact on the global energy landscape. However, there are concerns of potential environmental impacts of hydraulic fracturing of the shale formations, particularly those related to water quality. To evaluate the potential impact of hydraulically fractured shale on overlying aquifers, we conduct realizations of numerical modeling simulations to assess fluid flow and chloride transport from a synthetic Bowland Shale over a period of 11,000 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. Chloride mass exchange between fractures and the rock matrix was fully accounted for in the model. The assessment was carried out to investigate fluid and chloride mass fluxes before, during, and after hydraulic fracturing of the Bowland Shale. Impacts of the upward fracture height and aperture, as well as hydraulic conductivity of the multilayered bedrock system, are also included this assessment. This modeling revealed that the hydraulically fractured Bowland Shale is unlikely to pose a risk to its overlying groundwater quality when the induced fracture aperture is ?200 µm. With the fracture aperture ?1000 µm, the upward chloride flux becomes very sensitive to the upward fracture height growth and hydraulic conductivity of the multilayered bedrock system. In the extremely unlikely event of the upward fracture growth directly connecting the shale formation to the overlying Sherwood Sandstone aquifer with the fracture aperture ?1000 µm, the upward chloride mass flux could potentially pose risks to the overlying aquifer in 100 years. The model study also revealed 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, reducing further upward flux toward the overlying aquifers.

  13. Application of characteristic time concepts for hydraulic fracture configuration design, control, and optimization. Final report

    SciTech Connect

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

    1992-10-01

    The analysis of pertinent energy components or affiliated characteristic times for hydraulic stimulation processes serves as an effective tool for fracture configuration designs optimization, and control. This evaluation, in conjunction with parametric sensitivity studies, provides a rational base for quantifying dominant process mechanisms and the roles of specified reservoir properties relative to controllable hydraulic fracture variables for a wide spectrum of treatment scenarios. Results are detailed for the following multi-task effort: (a) Application of characteristic time concept and parametric sensitivity studies for specialized fracture geometries (rectangular, penny-shaped, elliptical) and three-layered elliptic crack models (in situ stress, elastic moduli, and fracture toughness contrasts). (b) Incorporation of leak-off effects for models investigated in (a). (c) Simulation of generalized hydraulic fracture models and investigation of the role of controllable vaxiables and uncontrollable system properties. (d) Development of guidelines for hydraulic fracture design and optimization.

  14. Application of characteristic time concepts for hydraulic fracture configuration design, control, and optimization

    SciTech Connect

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

    1992-10-01

    The analysis of pertinent energy components or affiliated characteristic times for hydraulic stimulation processes serves as an effective tool for fracture configuration designs optimization, and control. This evaluation, in conjunction with parametric sensitivity studies, provides a rational base for quantifying dominant process mechanisms and the roles of specified reservoir properties relative to controllable hydraulic fracture variables for a wide spectrum of treatment scenarios. Results are detailed for the following multi-task effort: (a) Application of characteristic time concept and parametric sensitivity studies for specialized fracture geometries (rectangular, penny-shaped, elliptical) and three-layered elliptic crack models (in situ stress, elastic moduli, and fracture toughness contrasts). (b) Incorporation of leak-off effects for models investigated in (a). (c) Simulation of generalized hydraulic fracture models and investigation of the role of controllable vaxiables and uncontrollable system properties. (d) Development of guidelines for hydraulic fracture design and optimization.

  15. 77 FR 36273 - Public Meeting on Draft Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-18

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

  16. An enhanced pseudo-3D model for hydraulic fracturing accounting for viscous height growth, non-local elasticity, and

    E-print Network

    Peirce, Anthony

    An enhanced pseudo-3D model for hydraulic fracturing accounting for viscous height growth, non to the predictions calculated using a recently developed fully planar hydraulic fracturing simulator. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Hydraulic fracturing (HF) is a process in which

  17. Accepted Manuscript Data-driven Proxy at Hydraulic Fracture Cluster Level: A Technique for Efficient CO2-

    E-print Network

    Mohaghegh, Shahab

    Accepted Manuscript Data-driven Proxy at Hydraulic Fracture Cluster Level: A Technique., Mohaghegh, S., Esmaili, S., Data-driven Proxy at Hydraulic Fracture Cluster Level: A Technique for Efficient ACCEPTED ACCEPTED MANUSCRIPT 1 Data-driven Proxy at Hydraulic Fracture Cluster Level: A Technique

  18. Identification of Parameters Influencing the Response of Gas Storage Wells to Hydraulic Fracturing with the Aid of a Neural Network

    E-print Network

    Mohaghegh, Shahab

    75083-3836, U.S.A. Telex, 163245 SPEUT. Abstract Performing hydraulic fractures on gas storage wells necessary for most reservoir studies and hydraulic fracture design and evaluation are scarce for these old storage wells to hydraulic fracturing may be identified in the absence of sufficient reservoir data

  19. Analysis of the classical pseudo-3D model for hydraulic fracture with equilibrium height growth across stress barriers

    E-print Network

    Peirce, Anthony

    Analysis of the classical pseudo-3D model for hydraulic fracture with equilibrium height growth t This paper deals with the so-called ``pseudo three-dimensional'' (P3D) model for a hydraulic fracture of the length, height, and aperture of the hydraulic fracture, in contrast to the numerical formulations adopted

  20. Analysis of Best Hydraulic Fracturing Practices in the Golden Trend Fields of Oklahoma Shahab D. Mohaghegh, West Virginia University

    E-print Network

    Mohaghegh, Shahab

    Analysis of Best Hydraulic Fracturing Practices in the Golden Trend Fields of Oklahoma Shahab D of optimized hydraulic fracturing procedure. Detail stimulation data from more than 230 wells in the Golden of hydraulic fractures. Therefore, it is highly recommended that the clastic and carbonate formations

  1. 77 FR 36273 - Public Meeting on Draft Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-18

    ... AGENCY Public Meeting on Draft Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using... agency has developed on the use of diesel fuels in oil and gas hydraulic fracturing and to solicit input... discuss ``Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel...

  2. 77 FR 40354 - Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel Fuels-Draft

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-09

    ... AGENCY Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel Fuels--Draft... published on May 10, 2012, Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel....gov @epa.gov. Mail: Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using...

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

    SciTech Connect

    Nolte, K.G. )

    1993-08-01

    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.

  4. Elastic Rock Heterogeneity Controls Brittle Rock Failure during Hydraulic Fracturing

    NASA Astrophysics Data System (ADS)

    Langenbruch, C.; Shapiro, S. A.

    2014-12-01

    For interpretation and inversion of microseismic data it is important to understand, which properties of the reservoir rock control the occurrence probability of brittle rock failure and associated seismicity during hydraulic stimulation. This is especially important, when inverting for key properties like permeability and fracture conductivity. Although it became accepted that seismic events are triggered by fluid flow and the resulting perturbation of the stress field in the reservoir rock, the magnitude of stress perturbations, capable of triggering failure in rocks, can be highly variable. The controlling physical mechanism of this variability is still under discussion. We compare the occurrence of microseismic events at the Cotton Valley gas field to elastic rock heterogeneity, obtained from measurements along the treatment wells. The heterogeneity is characterized by scale invariant fluctuations of elastic properties. We observe that the elastic heterogeneity of the rock formation controls the occurrence of brittle failure. In particular, we find that the density of events is increasing with the Brittleness Index (BI) of the rock, which is defined as a combination of Young's modulus and Poisson's ratio. We evaluate the physical meaning of the BI. By applying geomechanical investigations we characterize the influence of fluctuating elastic properties in rocks on the probability of brittle rock failure. Our analysis is based on the computation of stress fluctuations caused by elastic heterogeneity of rocks. We find that elastic rock heterogeneity causes stress fluctuations of significant magnitude. Moreover, the stress changes necessary to open and reactivate fractures in rocks are strongly related to fluctuations of elastic moduli. Our analysis gives a physical explanation to the observed relation between elastic heterogeneity of the rock formation and the occurrence of brittle failure during hydraulic reservoir stimulations. A crucial factor for understanding seismicity in unconventional reservoirs is the role of anisotropy of rocks. We evaluate an elastic VTI rock model corresponding to a shale gas reservoir in the Horn River Basin to understand the relation between stress, event occurrence and elastic heterogeneity in anisotropic rocks.

  5. Vertical arrays for fracture mapping in geothermal systems

    SciTech Connect

    Albright, J.N.; Rutledge, J.T.; Fairbanks, T.D.; Thomson, J.C.; Stevenson, M.A.

    1998-12-01

    In collaboration with UNOCAL Geothermal Operations, Los Alamos National Laboratory assessed the feasibility of using vertical arrays of borehole seismic sensors for mapping of microseismicity in The Geysers geothermal field. Seismicity which arises from minute displacements along fracture or fault surfaces has been shown in studies of seismically active oil reservoirs to be useful in identifying fractures affected by and possibly contributing to production. Use of retrievable borehole seismic packages at The Geysers was found to reduce the threshold for detection of microearthquakes by an estimated 2--3 orders of magnitude in comparison to surface-based sensors. These studies led to the design, materials selection, fabrication, and installation of a permanent array of geophones intended for long term seismic monitoring and mapping of fractures in the vicinity of the array at The Geysers.

  6. Laboratory imaging of stimulation fluid displacement from hydraulic fractures

    SciTech Connect

    Tidwell, V.; Parker, M.

    1996-11-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Burden, Susan

    2013-03-01

    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.

  8. Shallow hydraulic fracturing measurements in Korea support tectonic and seismic indicators of regional stress.

    SciTech Connect

    Haimson, Bezalel Cecil; Lee, Moo Yul; Song, I.

    2003-07-01

    We have conducted five hydraulic fracturing stress measurement campaigns in Korea, involving 13 test holes ranging in depth from 30 to 250 m, at locations from North Seoul to the southern coast of the peninsula. The measurements reveal consistent crustal stress magnitudes and directions that suggest persistence throughout western and southern Korea. The maximum horizontal stress {sigma}{sub H} is oriented between ENE-WSW and E-W, in accord with plate movement and deformation, and with directions indicated by both focal mechanism solutions from earthquakes inland and offshore as well as borehole breakouts in mainland China close to its eastern coast. With respect to magnitudes, the vertical stress is the overall minimum stress at all tested locations, suggesting a thrust faulting regime within the relatively shallow depths reached by our tests. Typically, such a stress regime becomes one favoring strike-slip at greater depths, as is also indicated by the focal mechanism solutions around Korea.

  9. Preliminary stress measurements in central California using the hydraulic fracturing technique

    USGS Publications Warehouse

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

    1977-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    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.

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

    PubMed

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

    2011-09-25

    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. PMID:21885152

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

    SciTech Connect

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

    1994-01-20

    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.

  13. 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...

  14. Automated Optimization Strategies for Horizontal Wellbore and Hydraulic Fracture Stages Placement in Unconventional Gas Reseroirs 

    E-print Network

    Plaksina, Tatyana

    2015-05-05

    In the last decades rapid advances in horizontal drilling and hydraulic fracturing technologies ensure production of commercial quantities of natural gas from many unconventional reservoirs. Reservoir management and development strategies for shale...

  15. Integrated Hydraulic Fracture Placement and Design Optimization in Unconventional Gas Reservoirs 

    E-print Network

    Ma, Xiaodan

    2013-12-10

    Unconventional reservoir such as tight and shale gas reservoirs has the potential of becoming the main source of cleaner energy in the 21th century. Production from these reservoirs is mainly accomplished through engineered hydraulic fracturing...

  16. Risk assessment of groundwater contamination from hydraulic fracturing fluid spills in Pennsylvania

    E-print Network

    Fletcher, Sarah Marie

    2012-01-01

    Fast-paced growth in natural gas production in the Marcellus Shale has fueled intense debate over the risk of groundwater contamination from hydraulic fracturing and the shale gas extraction process at large. While several ...

  17. Characterisation of hydraulic fractures in limestones using X-ray microtomography

    E-print Network

    Renard, Francois; Desrues, Jacques; Plougonven, Erwan; Ougier-Simonin, Audrey

    2006-01-01

    Hydraulic tension fractures were produced in porous limestones using a specially designed hydraulic cell. The 3D geometry of the samples was imaged using X-ray computed microtomography before and after fracturation. Using these data, it was possible to estimate the permeability tensor of the core samples, extract the path of the rupture and compare it to the heterogeneities initially present in the rock.

  18. Computer simulation of effective viscosity of fluid-proppant mixture used in hydraulic fracturing

    E-print Network

    Kuzkin, Vitaly A; Linkov, Aleksandr M

    2013-01-01

    The paper presents results of numerical experiments performed to evaluate the effective viscosity of a fluid-proppant mixture, used in hydraulic fracturing. The results, obtained by two complimenting methods (the particle dynamics and the smoothed particle hydrodynamics), coincide to the accuracy of standard deviation. They provide an analytical equation for the dependence of effective viscosity on the proppant concentration, needed for numerical simulation of the hydraulic fracture propagation.

  19. Quantification of rock stress heterogeneity: Application to hydraulic fracturing of hydrocarbon reservoirs

    NASA Astrophysics Data System (ADS)

    Langenbruch, Cornelius; Shapiro, Serge A.

    2015-04-01

    Fluid injection-induced earthquakes occur due to opening of new and re-activation of pre-existing fractures contained in the rock volume stress-perturbed by the fluid injection. We compare elastic rock heterogeneity measured by borehole logging to the occurrence of seismic events caused by hydraulic fracturing of the corresponding rock sections. Our observations made from two hydraulic fracturing case studies suggest that elastic rock heterogeneity controls the occurrence of fluid injection-induced earthquakes. The seismic events occur preferentially in rock sections characterized by low Poisson's ratio and high Young's modulus. Fracture opening and re-activation probability and the occurrence of associated seismic events should be strongly related to the initial state of stress in the unperturbed reservoir rock. We describe the sedimentary reservoir rock by a perfectly layered linear elastic medium in equilibrium to an externally applied homogeneous far field stress and quantify the relation between stress changes leading to fracture opening and re-activation and elastic rock heterogeneity. We extend existing analytic solutions of stress fluctuations in heterogeneous linear elastic media consisting of elastically isotropic layers to the case of vertical transverse isotropic layers. This allows application to unconventional shale gas reservoirs, which are usually characterized by a high intrinsic anisotropy. We find that magnitudes of rock stress fluctuations originating from elastic rock heterogeneity are significant. Moreover, we show that stress changes leading to fracture opening and re-activation in rocks undergo scale invariance spatial fluctuations. The scale invariant nature of rock stress fluctuations is caused by scale invariant fluctuations of elastic rock properties measured along the borehole. This gives a physical explanation for scale invariance of seismogenic processes. Based on our model, we analyze the physical meaning of a heterogeneity index of rocks, which indicates rocks sections of high Young's modulus and low Poisson's ratio. This index is an indicator of occurrence probability of brittle rock failure during hydraulic reservoir stimulations in the analyzed cases. However, our quantitative study demonstrates that rock failure indicator, which are based solely on elastic properties of rocks cannot have a universal physical meaning. In addition, our results suggest that even though the intermediate principal stress magnitude is not directly involved in the Mohr Coulomb failure criterion, it has a significant influence on the stress changes leading to re-activation and opening of fractures. This finding coincides with observations made during fracturing tests of rock samples in laboratory. In summary, our study demonstrates that stress fluctuations resulting from elastic rock heterogeneity are of significant importance for the seismogenesis of fluid injection-induced earthquakes. The physics of seismogenic processes can be understood by analyzing the physical origin of rock stress fluctuations and their relation to brittle rock failure processes.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  1. Hydraulic fracture reorientation in primary and secondary recovery from low-permeability reservoirs

    SciTech Connect

    Wright, C.A.; Conant, R.A.

    1995-12-31

    Hydraulic fracture orientation is critical to both primary and secondary oil recovery in low-permeability reservoirs. Incomplete and often overlapping drainage patterns under primary recovery, as well as inefficient sweep and premature water (or steam) breakthrough under secondary recovery are some of the common production problems that often result from hydraulic fracture reorientation. Often, hydraulic fracture orientation is measured on a few wells, and then generalized across the entire field under development. This characterization of regional fracture (stress) orientation is then assumed constant over the development life of the field. A wealth of recent observations have definitively shown that fracture (stress) orientation in low-permeability reservoirs can be profoundly affected by production activities. Hydraulic fracture reorientation has been observed on dozens of staged fracture treatments (in several fields) under both primary and secondary recovery. A summary of collected field data from three extensive field studies is presented. The production impact of fracture reorientation on both primary and secondary recovery schemes is addressed; and strategies are presented which utilize the recent findings for both enhancing primary recovery and mitigating some common problems with secondary recovery. The discussion of reorientation mechanisms is greatly enlightened by recent data which reveals a startling correlation between observed fracture reorientation and indirect measurements of reservoir compaction.

  2. Creation and Impairment of Hydraulic Fracture Conductivity in Shale Formations 

    E-print Network

    Zhang, Junjing

    2014-07-10

    are complicated. Standard fracture conductivity measurement procedures were developed for high concentration propped fractures and need to be modified to measure the conductivity of unpropped fractures and the low concentration proppant packs. Water-based...

  3. Interpretation of hydraulic conductivity in a fractured-rock aquifer over increasingly larger length dimensions

    NASA Astrophysics Data System (ADS)

    Shapiro, Allen M.; Ladderud, Jeffery A.; Yager, Richard M.

    2015-11-01

    A comparison of the hydraulic conductivity over increasingly larger volumes of crystalline rock was conducted in the Piedmont physiographic region near Bethesda, Maryland, USA. Fluid-injection tests were conducted on intervals of boreholes isolating closely spaced fractures. Single-hole tests were conducted by pumping in open boreholes for approximately 30 min, and an interference test was conducted by pumping a single borehole over 3 days while monitoring nearby boreholes. An estimate of the hydraulic conductivity of the rock over hundreds of meters was inferred from simulating groundwater inflow into a kilometer-long section of a Washington Metropolitan Area Transit Authority tunnel in the study area, and a groundwater modeling investigation over the Rock Creek watershed provided an estimate of the hydraulic conductivity over kilometers. The majority of groundwater flow is confined to relatively few fractures at a given location. Boreholes installed to depths of approximately 50 m have one or two highly transmissive fractures; the transmissivity of the remaining fractures ranges over five orders of magnitude. Estimates of hydraulic conductivity over increasingly larger rock volumes varied by less than half an order of magnitude. While many investigations point to increasing hydraulic conductivity as a function of the measurement scale, a comparison with selected investigations shows that the effective hydraulic conductivity estimated over larger volumes of rock can either increase, decrease, or remain stable as a function of the measurement scale. Caution needs to be exhibited in characterizing effective hydraulic properties in fractured rock for the purposes of groundwater management.

  4. Imbibition of hydraulic fracturing fluids into partially saturated shale

    NASA Astrophysics Data System (ADS)

    Birdsell, Daniel T.; Rajaram, Harihar; Lackey, Greg

    2015-08-01

    Recent studies suggest that imbibition of hydraulic fracturing fluids into partially saturated shale is an important mechanism that restricts their migration, thus reducing the risk of groundwater contamination. We present computations of imbibition based on an exact semianalytical solution for spontaneous imbibition. These computations lead to quantitative estimates of an imbibition rate parameter (A) with units of LT-1/2 for shale, which is related to porous medium and fluid properties, and the initial water saturation. Our calculations suggest that significant fractions of injected fluid volumes (15-95%) can be imbibed in shale gas systems, whereas imbibition volumes in shale oil systems is much lower (3-27%). We present a nondimensionalization of A, which provides insights into the critical factors controlling imbibition, and facilitates the estimation of A based on readily measured porous medium and fluid properties. For a given set of medium and fluid properties, A varies by less than factors of ˜1.8 (gas nonwetting phase) and ˜3.4 (oil nonwetting phase) over the range of initial water saturations reported for the Marcellus shale (0.05-0.6). However, for higher initial water saturations, A decreases significantly. The intrinsic permeability of the shale and the viscosity of the fluids are the most important properties controlling the imbibition rate.

  5. Selective oxidation of bromide in wastewater brines from hydraulic fracturing.

    PubMed

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

    2013-07-01

    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

  6. Development of an Advanced Hydraulic Fracture Mapping System

    SciTech Connect

    Norm Warpinski; Steve Wolhart; Larry Griffin; Eric Davis

    2007-01-31

    The project to develop an advanced hydraulic fracture mapping system consisted of both hardware and analysis components in an effort to build, field, and analyze combined data from tiltmeter and microseismic arrays. The hardware sections of the project included: (1) the building of new tiltmeter housings with feedthroughs for use in conjunction with a microseismic array, (2) the development of a means to use separate telemetry systems for the tilt and microseismic arrays, and (3) the selection and fabrication of an accelerometer sensor system to improve signal-to-noise ratios. The analysis sections of the project included a joint inversion for analysis and interpretation of combined tiltmeter and microseismic data and improved methods for extracting slippage planes and other reservoir information from the microseisms. In addition, testing was performed at various steps in the process to assess the data quality and problems/issues that arose during various parts of the project. A prototype array was successfully tested and a full array is now being fabricated for industrial use.

  7. Proppant transport in hydraulic fracturing: Crack tip screen-out in KGD and P3D models

    E-print Network

    Peirce, Anthony

    Proppant transport in hydraulic fracturing: Crack tip screen-out in KGD and P3D models E.V. Dontsov February 2015 Available online 14 March 2015 Keywords: Hydraulic fracturing Proppant transport Numerical modeling a b s t r a c t The aim of this study is to develop a model for proppant transport in hydraulic

  8. The Depths of Hydraulic Fracturing and Accompanying Water Use Across the United States.

    PubMed

    Jackson, Robert B; Lowry, Ella R; Pickle, Amy; Kang, Mary; DiGiulio, Dominic; Zhao, Kaiguang

    2015-08-01

    Reports highlight the safety of hydraulic fracturing for drinking water if it occurs "many hundreds of meters to kilometers underground". To our knowledge, however, no comprehensive analysis of hydraulic fracturing depths exists. Based on fracturing depths and water use for ?44,000 wells reported between 2010 and 2013, the average fracturing depth across the United States was 8300 ft (?2500 m). Many wells (6900; 16%) were fractured less than a mile from the surface, and 2600 wells (6%) were fractured above 3000 ft (900 m), particularly in Texas (850 wells), California (720), Arkansas (310), and Wyoming (300). Average water use per well nationally was 2,400,000 gallons (9,200,000 L), led by Arkansas (5,200,000 gallons), Louisiana (5,100,000 gallons), West Virginia (5,000,000 gallons), and Pennsylvania (4,500,000 gallons). Two thousand wells (?5%) shallower than one mile and 350 wells (?1%) shallower than 3000 ft were hydraulically fractured with >1 million gallons of water, particularly in Arkansas, New Mexico, Texas, Pennsylvania, and California. Because hydraulic fractures can propagate 2000 ft upward, shallow wells may warrant special safeguards, including a mandatory registry of locations, full chemical disclosure, and, where horizontal drilling is used, predrilling water testing to a radius 1000 ft beyond the greatest lateral extent. PMID:26196164

  9. Finite Element Code For 3D-Hydraulic Fracture Propagation Equations (3-layer).

    Energy Science and Technology Software Center (ESTSC)

    1992-03-24

    HYFRACP3D is a finite element program for simulation of a pseudo three-dimensional fracture geometries with a two-dimensional planar solution. The model predicts the height, width and winglength over time for a hydraulic fracture propagating in a three-layered system of rocks with variable rock mechanics properties.

  10. Development of connected permeability in massive crystalline rocks through hydraulic fracture propagation and

    E-print Network

    Development of connected permeability in massive crystalline rocks through hydraulic fracture, South Orange, NSW, Australia ABSTRACT The ability to generate deep flow in massive crystalline rocks to a decrease in rock mass permeability. The frequency of natural fractures also decreases with depth, resulting

  11. Combined use of straddle packer testing and FLUTe profiling for hydraulic testing in fractured rock boreholes

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    A combination of high resolution hydraulic tests using straddle packers and transmissivity (T) profiling using the FLUTe flexible liner method (liner profiling) in densely fractured rock boreholes is shown to be efficient for the determination of the vertical distribution of T along the entire hole. The liner T profiling method takes a few hours or less to scan the entire borehole length resulting in a T profile. Under favorable conditions this method has good reliability for identifying the highest T zones identified by distinct decreases in liner velocity when these zones are covered by the descending liner. In contrast, for one short test interval (e.g., 1-2 m) the multiple-test, straddle-packer method takes a few hours to measure T with good precision and accuracy using a combination of steady-state and transient tests (e.g., constant head step tests, slug tests, and constant rate pumping tests). Because of the time consuming aspect of this multiple-test method, it is most efficient in each borehole to conduct straddle packer testing only in priority zones selected after assessment of other borehole data collected prior to packer testing. The T profile from the liner method is instrumental in selecting high permeable zones for application of the multiple-test method using straddle packers, which in turn, refines the T estimation from the liner profile. Results from three boreholes in densely fractured sandstone demonstrate this approach showing the synergistic use of the methods with emphasis on information important for determining hydraulic apertures.

  12. Vertical cross contamination of trichloroethylene in a borehole in fractured sandstone

    USGS Publications Warehouse

    Sterling, S.N.; Parker, B.L.; Cherry, J.A.; Williams, J.H.; Lane, J.W., Jr.; Haeni, F.P.

    2005-01-01

    Boreholes drilled through contaminated zones in fractured rock create the potential for vertical movement of contaminated ground water between fractures. The usual assumption is that purging eliminates cross contamination; however, the results of a field study conducted in a trichloroethylene (TCE) plume in fractured sandstone with a mean matrix porosity of 13% demonstrates that matrix-diffusion effects can be strong and persistent. A deep borehole was drilled to 110 m below ground surface (mbgs) near a shallow bedrock well containing high TCE concentrations. The borehole was cored continuously to collect closely spaced samples of rock for analysis of TCE concentrations. Geophysical logging and flowmetering were conducted in the open borehole, and a removable multilevel monitoring system was installed to provide hydraulic-head and ground water samples from discrete fracture zones. The borehole was later reamed to complete a well screened from 89 to 100 mbgs; persistent TCE concentrations at this depth ranged from 2100 to 33,000 ??g/L. Rock-core analyses, combined with the other types of borehole information, show that nearly all of this deep contamination was due to the lingering effects of the downward flow of dissolved TCE from shallower depths during the few days of open-hole conditions that existed prior to installation of the multilevel system. This study demonstrates that transfer of contaminant mass to the matrix by diffusion can cause severe cross contamination effects in sedimentary rocks, but these effects generally are not identified from information normally obtained in fractured-rock investigations, resulting in potential misinterpretation of site conditions. Copyright ?? 2005 National Ground Water Association.

  13. Simultaneous initiation and growth of multiple radial hydraulic fractures from a horizontal wellbore

    NASA Astrophysics Data System (ADS)

    Lecampion, Brice; Desroches, Jean

    2015-09-01

    Multi-stage fracturing is the current preferred method of completion of horizontal wells in unconventional hydrocarbon reservoirs. Its core component consists in simultaneously initiating and propagating an array of hydraulic fractures. We develop a numerical model for the initiation and growth of an array of parallel radial hydraulic fractures. The solution accounts for fracture growth, coupling between elastic deformation and fluid flow in the fractures, elastic stress interactions between fractures and fluid flow in the wellbore. We also take into account the presence of a local pressure drop (function of the entering flow rate) at the connection between the well and the fracture, i.e., a choke-like effect due to current well completion practices, also referred to as entry friction. The partitioning of the fluid into the different fractures at any given time is part of the solution and is a critical indicator of simultaneous (balanced fluid partitioning) versus preferential growth. We validate our numerical model against reference solutions and a laboratory experiment for the initiation and growth of a single radial hydraulic fracture. We then investigate the impact of stress interaction on preferential growth of a subset of fractures in the array. Our results show that a sufficiently large local entry friction provides a strong feedback in the system and thus can counteract elastic stress interaction between fractures, thereby ensuring simultaneous growth. We propose a dimensionless number capturing the competition between stress interaction and local entry friction. This dimensionless number is a function of rock properties, fracture spacing and injection parameters. We verify that it captures the transition from the case of simultaneous growth (entry friction larger than interaction stress) to the case of preferential growth of some fractures (interaction stress larger than entry friction). We also discuss the implication of these results for multi-stage fracturing engineering practices.

  14. Implementation of Linear Pipe Channel Network to Estimate Hydraulic Parameters of Fractured Rock Masses

    NASA Astrophysics Data System (ADS)

    Han, J.; Um, J. G.; Wang, S.

    2014-12-01

    Modeling of fluid flow is important in geological, petroleum, environmental, civil and mining engineering. Fluid flow through fractured hard rock is very much dependent on the fracture network pattern in the rock mass and on the flow behavior through these fractures. This research deals with fluid flow behavior through fractures at an abandoned copper mine in southeast Korea. An injection well and three observation wells were installed at the mine site to monitor the hydraulic heads induced by injection of fresh water. A series of packer tests were performed to estimate the rock mass permeability and corresponding effective hydraulic aperture of the fractures. The three dimensional stochastic fracture network model was built and validated for the mine site. The two dimensional linear pipe network systems were constructed in directions of the observation wells using the fracture network model. A procedure of the fluid flow analysis on two dimensional discrete domain was applied to estimate the conductance, flow quantity and nodal head in the 2-D linear pipe channel network. The present results indicate that fracture geometry parameters (orientation, density and size) play an important role in the hydraulic characteristics of fractured rock masses.

  15. Fully Coupled Geomechanics and Discrete Flow Network Modeling of Hydraulic Fracturing for Geothermal Applications

    SciTech Connect

    Fu, P; Johnson, S M; Hao, Y; Carrigan, C R

    2011-01-18

    The primary objective of our current research is to develop a computational test bed for evaluating borehole techniques to enhance fluid flow and heat transfer in enhanced geothermal systems (EGS). Simulating processes resulting in hydraulic fracturing and/or the remobilization of existing fractures, especially the interaction between propagating fractures and existing fractures, represents a critical goal of our project. To this end, we are continuing to develop a hydraulic fracturing simulation capability within the Livermore Distinct Element Code (LDEC), a combined FEM/DEM analysis code with explicit solid-fluid mechanics coupling. LDEC simulations start from an initial fracture distribution which can be stochastically generated or upscaled from the statistics of an actual fracture distribution. During the hydraulic stimulation process, LDEC tracks the propagation of fractures and other modifications to the fracture system. The output is transferred to the Non-isothermal Unsaturated Flow and Transport (NUFT) code to capture heat transfer and flow at the reservoir scale. This approach is intended to offer flexibility in the types of analyses we can perform, including evaluating the effects of different system heterogeneities on the heat extraction rate as well as seismicity associated with geothermal operations. This paper details the basic methodology of our approach. Two numerical examples showing the capability and effectiveness of our simulator are also presented.

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

    USGS Publications Warehouse

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

    2002-01-01

    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.

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

    SciTech Connect

    Nelson, J.T. . Dept. of Mechanical Engineering Lawrence Berkeley Lab., CA )

    1988-11-01

    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.

  18. Seismic imaging of hydraullically-stimulated fractures: A numerical study of the effect of the source mechanism

    E-print Network

    Shabelansky, Andrey Hanan

    2012-01-01

    We present a numerical study of seismic imaging of hydraulically stimulated fractures using a single source from an adjacent fracturing-process. The source is either a point force generated from the perforation of the ...

  19. Hydraulic fracture orientation and production/injection induced reservoir stress changes in diatomite waterfloods

    SciTech Connect

    Wright, C.A.; Conant, R.A.; Golich, G.M.; Bondor, P.L.; Murer, A.S.; Dobie, C.A.

    1995-12-31

    This paper summarizes the (preliminary) findings from extensive field studies of hydraulic fracture orientation in diatomite waterfloods and related efforts to monitor the induced surface subsidence. Included are case studies from the Belridge and Lost Hills diatomite reservoirs. The primary purpose of the paper is to document a large volume of tiltmeter hydraulic fracture orientation data that demonstrates waterflood-induced fracture reorientation--a phenomenon not previously considered in waterflood development planning. Also included is a brief overview of three possible mechanisms for the observed waterflood fracture reorientation. A discussion section details efforts to isolate the operative mechanism(s) from the most extensive case study, as well as suggesting a possible strategy for detecting and possibly mitigating some of the adverse effects of production/injection induced reservoir stress changes--reservoir compaction and surface subsidence as well as fracture reorientation.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-08-01

    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.

  2. Pore-fluid effects on seismic waves in vertically fractured earth with orthotropic symmetry

    SciTech Connect

    Berryman, J.G.

    2010-05-15

    For elastically noninteracting vertical-fracture sets at arbitrary orientation angles to each other, a detailed model is presented in which the resulting anisotropic fractured medium generally has orthorhombic symmetry overall. Some of the analysis methods and ideas of Schoenberg are emphasized, together with their connections to other similarly motivated and conceptually related methods by Sayers and Kachanov, among others. Examples show how parallel vertical-fracture sets having HTI (horizontal transversely isotropic) symmetry transform into orthotropic fractured media if some subsets of the vertical fractures are misaligned with the others, and then the fractured system can have VTI (vertical transversely isotropic) symmetry if all of the fractures are aligned randomly or half parallel and half perpendicular to a given vertical plane. An orthotropic example having vertical fractures in an otherwise VTI earth system (studied previously by Schoenberg and Helbig) is compared with the other examples treated and it is finally shown how fluids in the fractures affect the orthotropic poroelastic system response to seismic waves. The key result is that fracture-influence parameters are multiplied by a factor of (1-B), where 0 {le} B < 1 is Skempton's second coefficient for poroelastic media. Skempton's B coefficient is itself a measurable characteristic of fluid-saturated porous rocks, depending on porosity, solid moduli, and the pore-fluid bulk modulus. For heterogeneous porous media, connections between the present work and earlier related results of Brown and Korringa are also established.

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

    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.

  4. Assessing Microbial Activity in Marcellus Shale Hydraulic Fracturing Fluids

    NASA Astrophysics Data System (ADS)

    Wishart, J. R.; Morono, Y.; Itoh, M.; Ijiri, A.; Hoshino, T.; Inagaki, F.; Verba, C.; Torres, M. E.; Colwell, F. S.

    2014-12-01

    Hydraulic fracturing (HF) produces millions of gallons of waste fluid which contains a microbial community adapted to harsh conditions such as high temperatures, high salinities and the presence of heavy metals and radionuclides. Here we present evidence for microbial activity in HF production fluids. Fluids collected from a Marcellus shale HF well were supplemented with 13C-labeled carbon sources and 15N-labeled ammonium at 25°C under aerobic or anaerobic conditions. Samples were analyzed for 13C and 15N incorporation at sub-micrometer scale by ion imaging with the JAMSTEC NanoSIMS to determine percent carbon and nitrogen assimilation in individual cells. Headspace CO2 and CH4 were analyzed for 13C enrichment using irm-GC/MS. At 32 days incubation carbon assimilation was observed in samples containing 1 mM 13C-labeled glucose under aerobic and anaerobic conditions with a maximum of 10.4 and 6.5% total carbon, respectively. Nitrogen assimilation of 15N ammonium observed in these samples were 0.3 and 0.8% of total nitrogen, respectively. Head space gas analysis showed 13C enrichment in CH4 in anaerobic samples incubated with 1mM 13C-labeled bicarbonate (2227 ‰) or methanol (98943 ‰). Lesser 13C enrichment of CO2 was observed in anaerobic samples containing 1 mM 13C-labeled acetate (13.7 ‰), methanol (29.9 ‰) or glucose (85.4 ‰). These results indicate metabolic activity and diversity in microbial communities present in HF flowback fluids. The assimilation of 13C-labeled glucose demonstrates the production of biomass, a critical part of cell replication. The production of 13CO2 and 13CH4 demonstrate microbial metabolism in the forms of respiration and methanogenesis, respectively. Methanogenesis additionally indicates the presence of an active archaeal community. This research shows that HF production fluid chemistry does not entirely inhibit microbial activity or growth and encourages further research regarding biogeochemical processes occurring in Marcellus shale HF wells. Biogeochemical activity may impact the efficacy of HF and natural gas production as well as the chemistry of produced fluids which have become an environmental and public health concern.

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

    SciTech Connect

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

    1991-09-01

    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.

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

    USGS Publications Warehouse

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

    2002-01-01

    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.

  7. An Innovative Approach for Management of Vertical Coronal Fracture in Molar: Case Report

    PubMed Central

    Kathuria, Ambica; Kavitha, M.; Ravishankar, P.

    2012-01-01

    Unlike anterior teeth, acute exogenous trauma is an infrequent cause of posterior coronal vertical tooth fractures. Endodontic and restorative management of such fractures is a great challenge for the clinician. Newer advancements in adhesive techniques can provide successful intracoronal splinting of such teeth to reinforce the remaining tooth structure. This paper describes the diagnosis and management of a case of complicated vertical coronal fracture in mandibular first molar induced by a traffic accident. PMID:22567453

  8. Synthetic Seismic Study for Hydraulic Fracture in Shale-Gas Reservoirs

    NASA Astrophysics Data System (ADS)

    Xia, Y.; Li, Y.

    2014-12-01

    Many studies have been done regarding performance of hydraulically fractured horizontal wells in the Bakken Shale Play (Wiley et. al., 2004; Mille et. al., 2008; Tabatabaei et. al., 2009). It's of great interest that whether the invaded brine causes the gas shale layer to behave differently in seismic profile due to potentially important application on reservoir monitoring and management for gas shale reservoirs. Because gas shale formations are generally much thinner than their adjacent layers (usually less than 100 meters), it's usually difficult to pick the reflection wave response of gas shale layer from in-situ seismic profile. Therefore, we have designed a workflow to investigate the effects of hydraulic fracture in gas shale reservoir by using synthetic seismic survey on simplified subsurface model. The simplified model mainly consists of several horizontally homogeneous layers of sand and shale, whereas the hydraulic fracture occurs in the middle thin gas shale formation and causes brine invasion in part of it. The goal of the synthetic seismic investigation is to see how the response of the reflection wave from this layer behaves differently due to the hydraulic fracture. Due to the thickness and complex nature of shale reservoir, the greatest challenge would be to pick the seismic response of this formation from the background noise and to study the range of thickness and the depth of burial for this layer to be seismically detectable for the purpose of hydraulic fracture study. Seismic investigation is rarely used in the reservoir monitoring of gas shale reservoir due to seismic resolution limit. Thus, this study will help to explore potential seismic applications for gas shale reservoirs and improve understanding of seismic response of hydraulic fracture on unconventional reservoirs.

  9. Optimizing Hydraulic Fracture Spacing and Frac Timing in Unconventionals - Taking Advantage of Time-Dependent Pressure Diffusion

    NASA Astrophysics Data System (ADS)

    Sheibani, F.

    2014-12-01

    Due to low natural gas prices, low production rates, and increased development costs, many operators have shifted operations from shale gas to liquid-rich shale plays. One means to make shale gas plays more attractive is to enhance well production through stimulation optimization. In numerous previous works, the authors have highlighted the geomechanical causes and important parameters for hydraulic fracture optimization in naturally fractured shale plays. The authors have, for example, emphasized the impact that stress shadows, from multiple hydraulic fractures, has on increasing the resistance of natural fractures and weakness planes to shear stimulation. The authors have also shown the critical role that in-situ pressure and pressure changes have on natural fracture shear stimulation.In this paper, we present the results of a discrete element model numerical study of both hydraulic fracture spacing and hydraulic fracture timing in a fully hydro-mechanical coupled fashion. The pressure changes in the natural fracture system of an unconventional play, due to hydraulic fracturing, often follow a diffusion-type process, which means the pressure changes are time dependent. As shown in previous works of the authors and others, the time-dependent changes in the in-situ pressure can have a marked impact on shear stimulation. The study performed quantitatively looked at the impact of hydraulic fracture spacing as a function of in-situ pressure change and time for key parameters such as the in-situ stress ratio, natural fracture characteristics, and natural fracture mechanical properties. The results of the study help improve the understanding of in-situ pressure and hydraulic fracture timing on stimulation optimization and enhanced hydrocarbon production. The study also provides a means to optimize hydraulic fracture spacing and increase shear stimulation for unconventional wells.

  10. Stochastic Programming Approach to Hydraulic Fracture Design for the Lower Tertiary Gulf of Mexico 

    E-print Network

    Podhoretz, Seth

    2013-07-27

    ....................................... 47 Finite Conductivity Fracture Approximation ..................................... 52 Proppant Allocation in Multilayer Reservoirs .................................... 53 vi IV STOCHASTIC OPTIMIZATION.... ................................................................... 51 3.4 Vertical fracture, dimensionless productivity. .......................................... 53 3.5 Productivity index vs. ratio of proppant numbers. ..................................... 56 4.1 DVS schematic...

  11. Finite element modeling of hydraulic fracturing in 3D

    E-print Network

    2013-03-22

    Mar 22, 2013 ... wanted effects. like for instance. leakage of natural gas into the ... common in that they assume that fracturing takes place .... caused by well operations over a short time span. from .... The material strength in ..... stepping through long periods with no fracture events. ..... dry rock geothermal energy site.

  12. HYDRAULIC CHARACTERIZATION FOR STEAM ENHANCED REMEDIATION CONDUCTED IN FRACTURED ROCK

    EPA Science Inventory

    Remediation of fractured rock sites contaminated by non-aqueous phase liquids has long been recognized as the most difficult undertaking of any site clean-up. This is primarily the result of the complexity of the fracture framework, which governs the groundwater flow pathways and...

  13. 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...

  14. 77 FR 27451 - Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel Fuels-Draft...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-10

    ... AGENCY Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel Fuels--Draft... oil- and gas-related hydraulic fracturing (HF) using diesel fuels where the U.S. Environmental... Safe Drinking Water Act (SDWA) and regulations regarding UIC permitting of oil and gas...

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

    SciTech Connect

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

    1985-01-01

    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.

  16. The impact of gravity segregation on multiphase non-Darcy flow in hydraulically fractured gas wells 

    E-print Network

    Dickins, Mark Ian

    2008-10-10

    Committee: Dr. Duane McVay Multiphase and non-Darcy flow effects in hydraulically fractured gas wells reduce effective fracture conductivity. Typical proppant pack laboratory experiments are oriented in such a way such that phase segregation... is not possible, which results in mixed flow. Tidwell and Parker (1996), however, showed that in proppant packs, gravity segregation occurs for simultaneous gas and liquid injection at laboratory scale (1500 cm2). Although the impact of gravity on flow...

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

    SciTech Connect

    Not Available

    1981-06-01

    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.

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

    USGS Publications Warehouse

    Hess, Alfred E.

    1986-01-01

    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.

  19. A method to evaluate hydraulic fracture using proppant detection.

    PubMed

    Liu, Juntao; Zhang, Feng; Gardner, Robin P; Hou, Guojing; Zhang, Quanying; Li, Hu

    2015-11-01

    Accurate determination of the proppant placement and propped fracture height are important for evaluating and optimizing stimulation strategies. A technology using non-radioactive proppant and a pulsed neutron gamma energy spectra logging tool to determine the placement and height of propped fractures is proposed. Gd2O3 was incorporated into ceramic proppant and a Monte Carlo method was utilized to build the logging tools and formation models. Characteristic responses of the recorded information of different logging tools to fracture widths, proppant concentrations and influencing factors were studied. The results show that Gd capture gamma rays can be used to evaluate propped fractures and it has higher sensitivity to the change of fracture width and traceable proppant content compared with the exiting non-radioactive proppant evaluation techniques and only an after-fracture measurement is needed for the new method; The changes in gas saturation and borehole size have a great impact on determining propped fractures when compensated neutron and pulsed neutron capture tool are used. A field example is presented to validate the application of the new technique. PMID:26296059

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  1. Simulation of quasi-static hydraulic fracture propagation in porous media with XFEM

    NASA Astrophysics Data System (ADS)

    Juan-Lien Ramirez, Alina; Neuweiler, Insa; Löhnert, Stefan

    2015-04-01

    Hydraulic fracturing is the injection of a fracking fluid at high pressures into the underground. Its goal is to create and expand fracture networks to increase the rock permeability. It is a technique used, for example, for oil and gas recovery and for geothermal energy extraction, since higher rock permeability improves production. Many physical processes take place when it comes to fracking; rock deformation, fluid flow within the fractures, as well as into and through the porous rock. All these processes are strongly coupled, what makes its numerical simulation rather challenging. We present a 2D numerical model that simulates the hydraulic propagation of an embedded fracture quasi-statically in a poroelastic, fully saturated material. Fluid flow within the porous rock is described by Darcy's law and the flow within the fracture is approximated by a parallel plate model. Additionally, the effect of leak-off is taken into consideration. The solid component of the porous medium is assumed to be linear elastic and the propagation criteria are given by the energy release rate and the stress intensity factors [1]. The used numerical method for the spatial discretization is the eXtended Finite Element Method (XFEM) [2]. It is based on the standard Finite Element Method, but introduces additional degrees of freedom and enrichment functions to describe discontinuities locally in a system. Through them the geometry of the discontinuity (e.g. a fracture) becomes independent of the mesh allowing it to move freely through the domain without a mesh-adapting step. With this numerical model we are able to simulate hydraulic fracture propagation with different initial fracture geometries and material parameters. Results from these simulations will also be presented. References [1] D. Gross and T. Seelig. Fracture Mechanics with an Introduction to Micromechanics. Springer, 2nd edition, (2011) [2] T. Belytschko and T. Black. Elastic crack growth in finite elements with minimal remeshing. Int. J. Numer. Meth. Engng. 45, 601-620, (1999)

  2. The evolution of hydraulic fracturing in the Almond formation

    SciTech Connect

    Cramer, D.D.

    1995-12-31

    This study draws from a database of over 600 wells to evaluate reservoir, production and treatment characteristics in the low-permeability, naturally-fractured Almond formation. Treatment-induced damage can be significant; damage mechanisms are discussed and ways are shown to mitigate these problems. An effective fracture stimulation design combines proppant scheduling of the late 1970`s with fluid and gel-breaker systems of today.

  3. A Hermite cubic collocation scheme for plane strain hydraulic fractures Department of Mathematics, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z2

    E-print Network

    Peirce, Anthony

    A Hermite cubic collocation scheme for plane strain hydraulic fractures A. Peirce Department Accepted 13 February 2010 Available online 4 March 2010 Keywords: Hydraulic fractures Integro the propagation of a hydraulic fracture in a state of plane strain. Special blended cubic Hermite-power­law basis

  4. Identification of Successful Practices in Hydraulic Fracturing Using Intelligent Data Mining Tools; Application to the Codell Formation in the DJ Basin

    E-print Network

    Mohaghegh, Shahab

    SPE 77597 Identification of Successful Practices in Hydraulic Fracturing Using Intelligent Data to identify successful practices in hydraulic fracturing. The Codell formation is a low permeability sandstone candidate selection and identify successful practices. Hydraulic fracturing is an economic way of increasing

  5. What does hydraulic tomography tell us about fractured geological media? A field study and synthetic experiments

    NASA Astrophysics Data System (ADS)

    Zha, Yuanyuan; Yeh, Tian-Chyi J.; Illman, Walter A.; Tanaka, Tatsuya; Bruines, Patrick; Onoe, Hironori; Saegusa, Hiromitsu

    2015-12-01

    Between 2005 and 2010, Japan Atomic Energy Agency conducted four long-term, independent pumping tests in a fractured granite formation at the Mizunami Underground Research Laboratory (MIU) site in Mizunami city, central Japan. During these tests, drawdowns were monitored at different depths along several deep boreholes. These tests become one of the few, if not the only, hydraulic tomographic survey conducted in the world over thousands of meters in a fractured geologic medium with several fault zones. We analyzed the drawdown-time data set associated with each pumping test independently, and then the data sets from all pumping tests jointly to derive the spatial distributions of hydraulic conductivity (K) and specific storage (Ss) of the medium. These estimated distributions revealed some large-scale high K and low K zones. While the low K zones corroborated well with known low permeable layers and fault based on geological investigations, there were no clear geological features that can be related to the large-scale high K zones. In order to understand and substantiate these high and low K zones, we simulated a hydraulic tomographic survey in a synthetic fractured aquifer, which bears similar geologic features (i.e., formations, fractures, and faults) at the MIU site, with exception that the hydraulic properties, fracture and fault distributions were known exactly. Results of the simulation show that not only are the identified high K zones related to fracture networks connected with pumping and observation locations of each pumping test but also their values reflect the degree of connectivity of the network. Afterward, we investigated the extent of the improvement of characterization of the fault and fractures through the use of deploying dense monitoring intervals and late-time flux measurements.

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

    SciTech Connect

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

    1992-11-01

    Hydraulic fracturing plays a pivotal role in the enhancement of oil and gas production recovery from low permeability reservoirs. The process of hydraulic fracturing entails the generation of a fracture by pumping fluids blended with special chemicals and proppants into the payzone at high injection rates and pressures to extend and wedge fractures. The mathematical modeling of hydraulically induced fractures generally incorporates coupling between the formation elasticity, fracture fluid flow, and fracture mechanics equations governing the formation structural responses, fluid pressure profile, and fracture growth. Two allied unsymmetric elliptic fracture models are developed for fracture configuration evolutions in three-layered 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.

  7. 40 CFR 147.52 - State-administered program-Hydraulic Fracturing of Coal Beds.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    The UIC program for hydraulic fracturing of coal beds in the State of Alabama, except those on Indian lands, is the program administered by the State Oil and Gas Board of Alabama, approved by EPA pursuant to Section 1425 of the SDWA on December 22, 1999 and effective on January 19,...

  8. Imaging hydraulic fractures in a geothermal reservoir Bruce R. Julian,1,2

    E-print Network

    Foulger, G. R.

    Click Here for Full Article Imaging hydraulic fractures in a geothermal reservoir Bruce R. Julian,1 geothermal field in eastern California in March 2005 caused a swarm of micro- earthquakes that was recorded] The Coso geothermal area lies in the southwestern corner of the Basin and Range province in eastern

  9. ANALYSIS OF GAS PRODUCTION FROM HYDRAULICALLY FRACTURED WELLS IN THE HAYNESVILLE SHALE USING SCALING METHODS

    E-print Network

    Patzek, Tadeusz W.

    ANALYSIS OF GAS PRODUCTION FROM HYDRAULICALLY FRACTURED WELLS IN THE HAYNESVILLE SHALE USING. The reservoir temperature is also high, up to 3000 F. These pressures are uniquely high among shale gas gas from the Haynesville Shale without horizontal wells and massive hydrofractures. In addition

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  11. 40 CFR 147.52 - State-administered program-Hydraulic Fracturing of Coal Beds.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) The Program Description for the Regulation of Hydraulic Fracturing of Coal Beds As required by 40 CFR... Register on January 19, 2000 in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained... 40 Protection of Environment 23 2014-07-01 2014-07-01 false State-administered...

  12. 40 CFR 147.52 - State-administered program-Hydraulic Fracturing of Coal Beds.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) The Program Description for the Regulation of Hydraulic Fracturing of Coal Beds As required by 40 CFR... Register on January 19, 2000 in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained... 40 Protection of Environment 24 2012-07-01 2012-07-01 false State-administered...

  13. 40 CFR 147.52 - State-administered program-Hydraulic Fracturing of Coal Beds.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) The Program Description for the Regulation of Hydraulic Fracturing of Coal Beds As required by 40 CFR... Register on January 19, 2000 in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained... 40 Protection of Environment 23 2011-07-01 2011-07-01 false State-administered...

  14. 40 CFR 147.52 - State-administered program-Hydraulic Fracturing of Coal Beds.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) The Program Description for the Regulation of Hydraulic Fracturing of Coal Beds As required by 40 CFR... Register on January 19, 2000 in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained... 40 Protection of Environment 24 2013-07-01 2013-07-01 false State-administered...

  15. Non-double-couple microearthquakes at Long Valley caldera, California, provide evidence for hydraulic fracturing

    E-print Network

    Foulger, G. R.

    for hydraulic fracturing G.R. Foulger a;Ã , B.R. Julian a , D.P. Hill a , A.M. Pitt a , P.E. Malin b , E. Shalev, such as rapid flow of water, steam, or CO2 into opening tensile cracks. Source orientations of earthquakes

  16. 77 FR 27691 - Oil and Gas; Well Stimulation, Including Hydraulic Fracturing, on Federal and Indian Lands

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-11

    ... Water, (58 FR 47354). This information is requested so that the BLM has all necessary information... Order Number 2, Drilling, (53 FR 46790) Section III.B.h., to confirm the mechanical integrity of the... Hydraulic Fracturing, on Federal and Indian Lands AGENCY: Bureau of Land Management, Interior....

  17. 40 CFR 147.52 - State-administered program-Hydraulic Fracturing of Coal Beds.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) The Program Description for the Regulation of Hydraulic Fracturing of Coal Beds As required by 40 CFR... Register on January 19, 2000 in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained... 40 Protection of Environment 22 2010-07-01 2010-07-01 false State-administered...

  18. 78 FR 34611 - Oil and Gas; Hydraulic Fracturing on Federal and Indian Lands

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-10

    ... initial comment period. DATES: The comment period for the proposed rule published May 24, 2013 (78 FR... The revised proposed rule was published on May 24, 2013 (78 FR 31636), with a 30-day comment period... Bureau of Land Management 43 CFR Part 3160 RIN 1004-AE26 Oil and Gas; Hydraulic Fracturing on Federal...

  19. 77 FR 38024 - Oil and Gas; Well Stimulation, Including Hydraulic Fracturing, on Federal and Indian Lands

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-26

    ... May 11, 2012, at 77 FR 27691, is extended. Send your comments on this proposed rule to the BLM on or... will be able to do so. Background The proposed rule was published on May 11, 2012 (77 FR 27691), with a... Hydraulic Fracturing, on Federal and Indian Lands AGENCY: Bureau of Land Management, Interior....

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

    SciTech Connect

    Stephen L. Karner, Ph.D

    2006-02-01

    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.

  1. Microseismic monitoring of the B-sand hydraulic fracture experiment at the DOE/GRI multi-site project

    SciTech Connect

    Warpinski, N.R. |; Wright, T.B.; Peterson, R.E.; Branagan, P.T.

    1996-11-01

    Six hydraulic-fracture injections into a fluvial sandstone at a depth of 4500 ft were monitored with multi-level triaxial seismic receivers in two wells, resulting in maps of the growth and final geometry of each fracture based upon microseismic activity. These diagnostic images show that the hydraulic fractures are highly contained for smaller-volume KCl-water injections, but height growth is significant for the larger-volume, higher-rate, higher-viscosity treatments. Fracture lengths for most injections are similar. Final results are also compared with fracture models.

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

    SciTech Connect

    David S. Schechter

    2004-04-26

    This report describes the work performed during the second 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 artificial fractured cores (AFCs) and X-ray CT to examine the physical mechanisms of bypassing in HFR and NFR that eventually result in less efficient CO{sub 2} flooding in heterogeneous or fracture-dominated reservoirs. To achieve this objective, in this period we concentrated our effort on investigating the effect of CO{sub 2} injection rates in homogeneous and fractured cores on oil recovery and a strategy to mitigate CO{sub 2} bypassing in a fractured core.

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

    SciTech Connect

    David S. Schechter

    2003-10-01

    This report describes the work performed during the second 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 artificial fractured cores (AFCs) and X-ray CT to examine the physical mechanisms of bypassing in HFR and NFR that eventually result in less efficient CO{sub 2} flooding in heterogeneous or fracture-dominated reservoirs. To achieve this objective, in this period we concentrated our effort on modeling the fluid flow in fracture surface, examining the fluid transfer mechanisms and describing the fracture aperture distribution under different overburden pressure using X-ray CT scanner.

  4. A WHOLISTIC REVIEW OF HIGH VOLUME HYDRAULIC FRACTURING

    E-print Network

    Ma, Lena

    of several environmental, economic and social consequences. "Fracking", as the high volume hydraulic fracking will have on other resources held in the public common. The rate at which fracking is growing global demand for increased energy production. While the economic importance of fracking should

  5. Effect of boundary conditions, impact loading and hydraulic stiffening on femoral fracture strength.

    PubMed

    Haider, Ifaz T; Speirs, Andrew D; Frei, Hanspeter

    2013-09-01

    Patient specific quantitative CT (QCT) imaging data together with the finite element (FE) method may provide an accurate prediction of a patient's femoral strength and fracture risk. Although numerous FE models investigating femoral fracture strength have been published, there is little consent on the effect of boundary conditions, dynamic loading and hydraulic strengthening due to intra-medullary pressure on the predicted fracture strength. We developed a QCT-derived FE model of a proximal femur that included node-specific modulus assigned based on the local bone density. The effect of three commonly used boundary conditions published in literature were investigated by comparing the resulting strain field due to an applied fracture load. The models were also augmented with viscoelastic material properties and subject to a realistic impact load profile to determine the effect of dynamic loads on the strain field. Finally, the effect of hydraulic strengthening was investigated by including node specific permeability and performing a coupled pore diffusion and stress analysis of the FE model. Results showed that all boundary conditions yield the same strain field patterns, but peak strains were 22% lower and fracture load was 18% higher when loaded at the greater trochanter than when loaded at the femoral head. Comparison of the dynamic models showed that material viscoelasticity was important, but inertial effects (vibration and shock) were not. Finally, pore pressure changes did not cause significant hydraulic strengthening of bone under fall impact loading. PMID:23906770

  6. Investigation of Hydraulic Fracture Propagation Using a Post-Peak Control System Coupled with Acoustic Emission

    NASA Astrophysics Data System (ADS)

    Chen, Li-Hsien; Chen, Wei-Chih; Chen, Yao-Chung; Benyamin, Leo; Li, An-Jui

    2015-05-01

    This study investigates the fracture mechanism of fluid coupled with a solid resulting from hydraulic fracture. A new loading machine was designed to improve upon conventional laboratory hydraulic fracture testing and to provide a means of better understanding fracture behavior of solid media. Test specimens were made of cement mortar. An extensometer and acoustic emission (AE) monitoring system recorded the circumferential deformation and crack growth location/number during the test. To control the crack growth at the post-peak stage the input fluid rate can be adjusted automatically according to feedback from the extensometer. The complete stress-deformation curve, including pre- and post-peak stages, was therefore obtained. The crack extension/growth developed intensively after the applied stress reached the breakdown pressure. The number of cracks recorded by the AE monitoring system was in good agreement with the amount of deformation (expansion) recorded by the extensometer. The results obtained in this paper provide a better understanding of the hydraulic fracture mechanism which is useful for underground injection projects.

  7. Hydraulic fracturing tests in anhydrite interbeds in the WIPP, Marker Beds 139 and 140

    SciTech Connect

    Howard, C L [RE Wawersik, W. R.; Carlson, L. V.; Henfling, J. A.; Borns, D. J.; Beauheim, R. L.; Roberts, R. M.

    1997-05-01

    Hydraulic fracturing tests were integrated with hydrologic tests to estimate the conditions under which gas pressure in the disposal rooms in the Waste Isolation Pilot Plant, Carlsbad, NM (WIPP) will initiate and advance fracturing in nearby anhydrite interbeds. The measurements were made in two marker beds in the Salado formation, MB139 and MB140, to explore the consequences of existing excavations for the extrapolation of results to undisturbed ground. The interpretation of these measurements is based on the pressure-time records in two injection boreholes and several nearby hydrologic observation holes. Data interpretations were aided by post-test borehole video surveys of fracture traces that were made visible by ultraviolet illumination of fluorescent dye in the hydraulic fracturing fluid. The conclusions of this report relate to the upper- and lower-bound gas pressures in the WIPP, the paths of hydraulically and gas-driven fractures in MB139 and MB140, the stress states in MB139 and MB140, and the probable in situ stress states in these interbeds in undisturbed ground far away from the WIPP.

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

    NASA Astrophysics Data System (ADS)

    Mouser, P. J.; Kekacs, D.

    2014-12-01

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

  9. Mechanisms and impact of damage resulting from hydraulic fracturing. Topical report, May 1995-July 1996

    SciTech Connect

    Penny, G.S.; Conway, M.W.; Almond, S.W.; Himes, R.; Nick, K.E.

    1996-08-01

    This topical report documents the mechanisms of formation damage following hydraulic fracturing and their impact upon gas well productivity. The categories of damage reviewed include absolute or matrix permeability damage, relative permeability alterations, the damage of natural fracture permeability mechanisms and proppant conductivity impairment. Case studies are reviewed in which attempts are made to mitigate each of the damage types. Industry surveys have been conducted to determine the perceptions of the industry on the topic of formation damage following hydraulic fracturing and to identify key formations in which formation damage is a problem. From this information, technical hurdles and new technology needs are identified and estimates are made of the benefits of developing and applying minimum formation damage technology.

  10. Computational and physical consequences of interaction of closely located simultaneous hydraulic fractures

    E-print Network

    Rejwer, Ewa

    2015-01-01

    Strong interaction of closely located, nearly parallel hydraulic fractures and its influence on their propagation are studied. Both computational and physical aspects of the problem are considered. It is shown that from the computational point of view, when a distance between cracks is small as compared with their sizes, the system becomes ill-conditioned and numerical results deteriorate. The physical consequence of the interaction consists in decreasing of the crack opening and even greater decrease of conductivity. Then the resistance to fluid flow grows what results in the propagation of only those fractures, the distance between which is large enough. The research aims to suggests a means to overcome the computational difficulty and to improve numerical simulation of hydraulic fractures in shales. Numerical experiments are carried out for a 2D problem by using the complex variable hypersingular boundary element method of higher order accuracy. The condition number of the main matrix of a system, the open...

  11. Hydraulic fracturing and the Crooked Lake Sequences: Insights gleaned from regional seismic networks

    NASA Astrophysics Data System (ADS)

    Schultz, Ryan; Stern, Virginia; Novakovic, Mark; Atkinson, Gail; Gu, Yu Jeffrey

    2015-04-01

    Within central Alberta, Canada, a new sequence of earthquakes has been recognized as of 1 December 2013 in a region of previous seismic quiescence near Crooked Lake, ~30 km west of the town of Fox Creek. We utilize a cross-correlation detection algorithm to detect more than 160 events to the end of 2014, which is temporally distinguished into five subsequences. This observation is corroborated by the uniqueness of waveforms clustered by subsequence. The Crooked Lake Sequences have come under scrutiny due to its strong temporal correlation (>99.99%) to the timing of hydraulic fracturing operations in the Duvernay Formation. We assert that individual subsequences are related to fracturing stimulation and, despite adverse initial station geometry, double-difference techniques allow us to spatially relate each cluster back to a unique horizontal well. Overall, we find that seismicity in the Crooked Lake Sequences is consistent with first-order observations of hydraulic fracturing induced seismicity.

  12. FINAL REPORT. CONTROL OF BIOLOGICALLY ACTIVE DEGRADATION ZONES BY VERTICAL HETEROGENEITY: APPLICATIONS IN FRACTURED MEDIA

    EPA Science Inventory

    The key objective of this research was to determine the distribution of biologically active contaminant degradation zones in a fractured, subsurface medium with respect to vertical heterogeneities. Our expectation was that
    hydrogeological properties would determine the size, d...

  13. Fracture studies from amplitude versus offset and azimuth and vertical seismic profile data 

    E-print Network

    Varela Gutierrez, Isabel

    2009-01-01

    In this thesis I address the problem of determining fracture properties of subsurface rocks from geophysical surface seismic and vertical seismic profile (VSP) data. In the first part of this thesis I perform multi-attribute ...

  14. METHOD DEVELOPMENT FOR DETERMINING THE HYDRAULIC CONDUCTIVITY OF FRACTURED POROUS MEDIA

    SciTech Connect

    Dixon, K.

    2013-09-30

    Plausible, but unvalidated, theoretical model constructs for unsaturated hydraulic conductivity of fractured porous media are currently used in Performance Assessment (PA) modeling for cracked saltstone and concrete (Flach 2011). The Nuclear Regulatory Commission (NRC) has expressed concern about the lack of model support for these assumed Moisture Characteristic Curves (MCC) data, as noted in Requests for Additional Information (RAIs) PA-8 and SP-4 (Savannah River Remediation, LLC, 2011). The objective of this task was to advance PA model support by developing an experimental method for determining the hydraulic conductivity of fractured cementitious materials under unsaturated conditions, and to demonstrate the technique on fractured saltstone samples. The task was requested through Task Technical Request (TTR) HLW-SSF-TTR-2012-0016 and conducted in accordance with Task Technical & Quality Assurance Plan (TTQAP) SRNL-TR-2012-00090. Preliminary method development previously conducted by Kohn et al. (2012) identified transient outflow extraction as the most promising method for characterizing the unsaturated properties of fractured porous media. While the research conducted by Kohn et al. (2012) focused on fractured media analogs such as stacked glass slides, the current task focused directly on fractured saltstone. For this task, four sample types with differing fracture geometries were considered: 1) intact saltstone, 2) intact saltstone with a single saw cut, smooth surface fracture, 3) micro-fractured saltstone (induced by oven drying), and 4) micro-fractured saltstone with a single, fully-penetrating, rough-surface fracture. Each sample type was tested initially for saturated hydraulic conductivity following method ASTM D 5084 using a flexible wall permeameter. Samples were subsequently tested using the transient outflow extraction method to determine cumulative outflow as a function of time and applied pressure. Of the four sample types tested, two yielded datasets suitable for analysis (sample types 3 and 4). The intact saltstone sample (sample type 1) did not yield any measureable outflow over the pressure range of the outflow test (0-1000 cm H{sub 2}O). This was expected because the estimated air entry pressure for intact saltstone is on the order of 100,000 cm H{sub 2}O (Dixon et al., 2009). The intact saltstone sample with a single saw cut smooth surface fracture (sample type 2) did not produce useable data because the fracture completely drained at less than 10 cm H{sub 2}O applied pressure. The cumulative outflow data from sample types 3 and 4 were analyzed using an inverse solution of the Richard’s equation for water flow in variably saturated porous media. This technique was implemented using the computer code Hydrus-1D (Šim?nek et al., 2008) and the resulting output included the van Genuchten-Mualem water retention and relative permeability parameters and predicted saturated hydraulic conductivity (Van Genuchten, 1980; Van Genuchten et al., 1991). Estimations of relative permeability and saturated conductivity are possible because the transient response of the sample to pressure changes is recorded during the multi-step outflow extraction test. Characteristic curves were developed for sample types 3 and 4 based on the results of the transient outflow method and compared to that of intact saltstone previously reported by Dixon et al. (2009). The overall results of this study indicate that the outflow extraction method is suitable for measuring the hydraulic properties of micro-fractured porous media. The resulting cumulative outflow data can be analyzed using the computer code Hydrus-1D to generate the van Genuchten curve fitting parameters that adequately describe fracture drainage. The resulting characteristic curves are consistent with blended characteristic curves that combine the behaviors of low pressure drainage associated with fracture flow with high pressure drainage from the bulk saltstone matrix.

  15. Effect of Different Instrumentation Techniques on Vertical Root Fracture Resistance of Endodontically Treated Teeth

    PubMed Central

    Tavanafar, Saeid; Karimpour, Azadeh; Karimpour, Hamideh; Mohammed Saleh, Abdulrahman; Hamed Saeed, Musab

    2015-01-01

    Statement of the Problem Vertical root fractures are catastrophic events that often result in tooth extraction. Many contributing factor are associated with increasing incidence of vertical root fracture. Root canal preparation is one of the predisposing factors which can increase the root susceptibility to vertical fracture. Purpose The aim of this study was to compare the effects of three different instrumentation techniques on vertical root fracture resistance of endodontically treated teeth. Materials and Methods In this study, 120 freshly extracted mandibular premolar teeth of similar dimensions were decoronated and randomly divided into control (n=30), nickel-titanium hand K-file (HF, n=30), BioRaCe rotary file (BR, n=30), and WaveOne reciprocating single-file (WO, n=30) groups. After cleaning and shaping the root canals, AH26 was used as canal sealer, and obturation was completed using the continuous wave technique. The root canals were embedded vertically in standardised autopolymerising acrylic resin blocks, and subjected to a vertical load to cause vertical root fracture. The forces required to induce fractures were measured using a universal testing machine. ANOVA and Tukey’s post-hoc test were used to analyse the data. Results All experimental groups showed statistically significant reductions in fracture resistance as compared with the control group. There was a statistically significant difference between the HF and BR groups. The WO group did not differ significantly from the HF group or the BR group. Conclusion All three instrumentation techniques caused weakening of the structure of the roots, and rendered them susceptible to fracture under lesser load than unprepared roots. The fracture resistance of roots prepared with the single-file reciprocating technique was similar to that of those prepared with NiTi hand and rotary instrumentation techniques. PMID:26106635

  16. Hydrophobic Organic Compounds in Hydraulic Fracturing Flowback Waters: Identification and Source Apportionment

    NASA Astrophysics Data System (ADS)

    Plata, D.; Shregglman, K.; Elsner, M.; Getzinger, G.; Ferguson, L.; Drollette, B.; Karatum, O.; Nelson, R. K.; Reddy, C. M.

    2014-12-01

    Current hydraulic fracturing technologies rely on organic chemicals to serve multiple critical functions, including corrosion inhibition, in situ gel formation, and friction reduction. While industrial users have disclosed several hundreds of compound and mixture identities, it is unclear which of these are used and where, in what proportion, and with what frequency. Furthermore, while flowback and production waters contain both fracturing additive and geogenic compounds, they may contain potential reaction byproducts as well. Here, we identified several hundred organic compounds present in six hydraulic fracturing flowback waters over the Fayetteville shale. Identifications were made via non-target analysis using two-dimensional gas chromatography with time of flight mass spectrometry for hydrophobic organic compounds and liquid chromatography- orbitrap mass spectrometry. Compound identities were confirmed using purchased standards when available. Using the SkyTruth database and the Waxman list of disclosed compounds, we assigned compounds as either fracturing-fluid-derived or geogenic (or both), or a putative transformation products thereof. Several unreported halogenated compounds were detected, including chlorinated, brominated, and iodated species that have no known natural sources. Control studies indicated that these could not be formed under typical laboratory or field storage conditions, suggesting that halogenation reactions may give rise to novel compounds in the subsurface, presumably via reaction between fracturing fluid additives and shale-derived brines. Further, the six samples were strikingly heterogeneous, reflecting the diversity in fracturing fluid composition and flowback handling procedures at the time of the study.

  17. Crack Extension in Hydraulic Fracturing of Shale Cores Using Viscous Oil, Water, and Liquid Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Bennour, Ziad; Ishida, Tsuyoshi; Nagaya, Yuya; Chen, Youqing; Nara, Yoshitaka; Chen, Qu; Sekine, Kotaro; Nagano, Yu

    2015-07-01

    We performed hydraulic fracturing experiments on cylindrical cores of anisotropic shale obtained by drilling normal to the sedimentary plane. Experiments were conducted under ambient condition and uniaxial stresses, using three types of fracturing fluid: viscous oil, water, and liquid carbon dioxide (L-CO2). In the experiments using water and oil, cracks extended along the loading direction normal to the sedimentary plane under the uniaxial loading and extended along the sedimentary plane without loading. These results suggest that the direction of crack extension is strongly affected by in situ stress conditions. Fluorescent microscopy revealed that hydraulic fracturing with viscous oil produced linear cracks with few branches, whereas that with water produced cracks with many branches inclining from the loading axis. Statistical analysis of P wave polarity of acoustic emission waveforms showed that viscous oil tended to induce Mode I fracture, whereas both water and L-CO2 tended to induce Mode II fracture. Crack extension upon injection of L-CO2 was independent of loading condition unlike extension for the other two fluids. This result seemed attributable to the low viscosity of L-CO2 and was consistent with previous observations for granite specimens that low-viscosity fluids like CO2 tend to induce widely extending cracks with many branches, with Mode II fractures being dominant. These features are more advantageous for shale gas production than those induced by injection of conventional slick water.

  18. Characterization of fracture permeability with high-resolution vertical flow measurements during borehole pumping.

    USGS Publications Warehouse

    Paillet, F.L.; Hess, A.E.; Cheng, C.H.; Hardin, E.

    1987-01-01

    The distribution of fracture permeability in granitic rocks was investigated by measuring the distribution of vertical flow in boreholes during periods of steady pumping. Pumping tests were conducted at two sites chosen to provide examples of moderately fractured rocks near Mirror Lake, New Hampshire and intensely fractured rocks near Oracle, Arizona. A sensitive heat-pulse flowmeter was used for accurate measurements of vertical flow as low as 0.2 liter per minute. Results indicate zones of fracture permeability in crystalline rocks are composed of irregular conduits that cannot be approximated by planar fractures of uniform aperture, and that the orientation of permeability zones may be unrelated to the orientation of individual fractures within those zones.-Authors

  19. Numerical evaluation of effective unsaturated hydraulic properties for fractured rocks

    SciTech Connect

    Lu, Zhiming; Kwicklis, Edward M

    2009-01-01

    To represent a heterogeneous unsaturated fractured rock by its homogeneous equivalent, Monte Carlo simulations are used to obtain upscaled (effective) flow properties. In this study, we present a numerical procedure for upscaling the van Genuchten parameters of unsaturated fractured rocks by conducting Monte Carlo simulations of the unsaturated flow in a domain under gravity-dominated regime. The simulation domain can be chosen as the scale of block size in the field-scale modeling. The effective conductivity is computed from the steady-state flux at the lower boundary and plotted as a function of the averaging pressure head or saturation over the domain. The scatter plot is then fitted using van Genuchten model and three parameters, i.e., the saturated conductivity K{sub s}, the air-entry parameter {alpha}, the pore-size distribution parameter n, corresponding to this model are considered as the effective K{sub s}, effective {alpha}, and effective n, respectively.

  20. Correlations to predict frictional pressure loss of hydraulic-fracturing slurry in coiled tubing

    SciTech Connect

    Shah, S.; Zhoi, Y.X.; Bailey, M.; Hernandez, J.

    2009-08-15

    Compared with conventional-tubing fracturing, coiled-tubing (CT) fracturing has several advantages. CT fracturing has become an effective stimulation technique for multizone oil and gas wells. It is also an attractive production-enhancement method for multiseam coalbed-methane wells, and wells with bypassed zones. The excessive frictional pressure loss through CT has been a concern in fracturing. The small diameter of the string limits the cross-sectional area open to flow. Furthermore, the tubing curvature causes secondary flow and results in extra flow resistance. This increased frictional pressure loss results in high surface pumping pressure. The maximum possible pump rate and sand concentration, therefore, have to be reduced. To design a CT fracturing job properly, it is essential to predict the frictional pressure loss through the tubing accurately. This paper presents correlations for the prediction of frictional pressure loss of fracturing slurries in straight tubing and CT. They are developed on the basis of full-scale slurry-flow tests with 11/2-in. CT and slurries prepared with 35 lbm/1,000 gal of guar gel. The extensive experiments were conducted at the full-scale CT-flow test facility. The proposed correlations have been verified with the experimental data and actual field CT-fracturing data. Case studies of wells recently fractured are provided to demonstrate the application of the correlations. The correlations will be useful to the CT engineers in their hydraulics design calculations.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  2. Geo-mechanical modeling and selection of suitable layer for hydraulic fracturing operation in an oil reservoir (south west of Iran)

    NASA Astrophysics Data System (ADS)

    Darvish, Hoda; Nouri-Taleghani, Morteza; Shokrollahi, Amin; Tatar, Afshin

    2015-11-01

    According to the growth of demands to oil resources, increasing the rate of oil production seems necessary. However, oil production declines with time as a result of pressure drop in reservoir as well as sealing of microscopic cracks and pores in the reservoir rock. Hydraulic fracturing is one of the common methods with high performance, which is widely applied to oil and gas reservoirs. In this study, wells in three sections of east, center, and west sides of a field are compared regarding the suitable layer for hydraulic fracturing operation. Firstly, elastic modulus were obtained in both dynamic and static conditions, then uniaxial compressive strength (UCS), type of shear and tensile failures, the most accurate model of failure in wells, safe and stable mud window, the best zone and layers, and finally reference pressures are determined as nominates for hydraulic fracturing. Types of shear failure in minimum, and maximum range of model and in tensile model were determined to be "Shear failure wide breakout (SWBO)", "Shear narrow breakout (SNBO)", and "Tensile vertical failure (TVER)", respectively. The range of safe mud window (SMW) in the studied wells was almost in the same range as it was in every three spots of the field. This range was determined between 5200-8800psi and 5800-10100psi for Ilam and Sarvak zones, respectively. Initial fracture pressure ranges for selected layers were determined 11,759-14,722, 11,910-14,164, and 11,848-14,953psi for the eastern, central, and western wells. Thus, western wells have the best situation for Hydraulic fracturing operation. Finally, it was concluded that the operation is more economic in Sarvak zone and western wells.

  3. Characterization of Hydraulic Active Fractures in a Dolostone Aquifer Using Heat and Contaminants As Tracers

    NASA Astrophysics Data System (ADS)

    Maldaner, C. H.; Coleman, T. I.; Parker, B. L.; Cherry, J. A.

    2014-12-01

    The number of hydraulically active fractures serving as advective contaminant migration pathways facilitating plume migration in fractured rock aquifers cannot be determined with confidence from indirect means such as visual inspection of core, borehole geophysics, and is only inferred from hydraulic tests. However, the position of depth-discrete hydraulic activity may be determined using contaminants or heat as tracers yet spatially detailed profile measurement techniques are required without imparting measurement bias of an open borehole. Contaminant concentration profiles from numerous samples along continuous core from a site contaminated since the early 1980's and heat injection in the sealed boreholes with high resolution profile monitoring are used to characterize the fracture network . Heat pulse tests using active distributed temperature sensing (DTS) were conducted in coreholes sealed with an impermeable flexible liner manufactured by FLUTe (Santa Fe, NM) to detect hydraulically active fracture zones. Using a Silixa ULTIMA-HSTM DTS, temperature data was acquired every 12.6 cm along an optic fiber cable with a spatial resolution of 29 cm. Temperature precision is on the order of 0.02°C for averaged measurements collected over 5 minute intervals. The test consisted of heating the measurement cable for 4 hours and monitoring the cooling process for over 8 hours. The resulting dataset consists of high-resolution temperature profiles at five-minute time steps during the test period. Dolostone rock composes most of the lithology units of the corehole, therefore it is unlikely that there are significant variations in rock thermal diffusivity. Multiple, successive temperature profiles were used to identify depth-discrete, hydraulically active flow zones with varying transmissivity based on different rates of heat dissipation. These variations were then compared with independent datasets including detected concentrations of contaminants in numerous rock core samples with depth, visual indication of staining on fracture surfaces in rock core logs, fracture size and intensity identified in the ATV log, and variability in borehole high hydraulic conductivity by continuous packer testing and T-profiling methods.

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

    SciTech Connect

    Shouchun Deng; Robert Podgorney; Hai Huang

    2011-02-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Cai, Zuansi; Ofterdinger, Ulrich

    2014-05-01

    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.

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

    PubMed

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

    2013-11-19

    Microbial communities associated with produced water from hydraulic fracturing are not well understood, and their deleterious activity can lead to significant increases in production costs and adverse environmental impacts. In this study, we compared the microbial ecology in prefracturing fluids (fracturing source water and fracturing fluid) and produced water at multiple time points from a natural gas well in southwestern Pennsylvania using 16S rRNA gene-based clone libraries, pyrosequencing, and quantitative PCR. The majority of the bacterial community in prefracturing fluids constituted aerobic species affiliated with the class Alphaproteobacteria. However, their relative abundance decreased in produced water with an increase in halotolerant, anaerobic/facultative anaerobic species affiliated with the classes Clostridia, Bacilli, Gammaproteobacteria, Epsilonproteobacteria, Bacteroidia, and Fusobacteria. Produced water collected at the last time point (day 187) consisted almost entirely of sequences similar to Clostridia and showed a decrease in bacterial abundance by 3 orders of magnitude compared to the prefracturing fluids and produced water samplesfrom earlier time points. Geochemical analysis showed that produced water contained higher concentrations of salts and total radioactivity compared to prefracturing fluids. This study provides evidence of long-term subsurface selection of the microbial community introduced through hydraulic fracturing, which may include significant implications for disinfection as well as reuse of produced water in future fracturing operations. PMID:24088205

  7. Application of particle and lattice codes to simulation of hydraulic fracturing

    NASA Astrophysics Data System (ADS)

    Damjanac, Branko; Detournay, Christine; Cundall, Peter A.

    2015-11-01

    With the development of unconventional oil and gas reservoirs over the last 15 years, the understanding and capability to model the propagation of hydraulic fractures in inhomogeneous and naturally fractured reservoirs has become very important for the petroleum industry (but also for some other industries like mining and geothermal). Particle-based models provide advantages over other models and solutions for the simulation of fracturing of rock masses that cannot be assumed to be continuous and homogeneous. It has been demonstrated (Potyondy and Cundall Int J Rock Mech Min Sci Geomech Abstr 41:1329-1364, 2004) that particle models based on a simple force criterion for fracture propagation match theoretical solutions and scale effects derived using the principles of linear elastic fracture mechanics (LEFM). The challenge is how to apply these models effectively (i.e., with acceptable models sizes and computer run times) to the coupled hydro-mechanical problems of relevant time and length scales for practical field applications (i.e., reservoir scale and hours of injection time). A formulation of a fully coupled hydro-mechanical particle-based model and its application to the simulation of hydraulic treatment of unconventional reservoirs are presented. Model validation by comparing with available analytical asymptotic solutions (penny-shape crack) and some examples of field application (e.g., interaction with DFN) are also included.

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

    SciTech Connect

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

    2013-11-19

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

  9. Enhanced detection of hydraulically active fractures by temperature profiling in lined heated bedrock boreholes

    NASA Astrophysics Data System (ADS)

    Pehme, P. E.; Parker, B. L.; Cherry, J. A.; Molson, J. W.; Greenhouse, J. P.

    2013-03-01

    SummaryThe effectiveness of borehole profiling using a temperature probe for identifying hydraulically active fractures in rock has improved due to the combination of two advances: improved temperature sensors, with resolution on the order of 0.001 °C, and temperature profiling within water inflated flexible impermeable liners used to temporarily seal boreholes from hydraulic cross-connection. The open-hole cross-connection effects dissipate after inflation, so that both the groundwater flow regime and the temperature distribution return to the ambient (background) condition. This paper introduces a third advancement: the use of an electrical heating cable that quickly increases the temperature of the entire static water column within the lined hole and thus places the entire borehole and its immediate vicinity into thermal disequilibrium with the broader rock mass. After heating for 4-6 h, profiling is conducted several times over a 24 h period as the temperature returns to background conditions. This procedure, referred to as the Active Line Source (ALS) method, offers two key improvements over prior methods. First, there is no depth limit for detection of fractures with flow. Second, both identification and qualitative comparison of evidence for ambient groundwater flow in fractures is improved throughout the entire test interval. The benefits of the ALS method are demonstrated by comparing results from two boreholes tested to depths of 90 and 120 m in a dolostone aquifer used for municipal water supply and in which most groundwater flow occurs in fractures. Temperature logging in the lined holes shows many fractures in the heterothermic zone both with and without heating, but only the ALS method shows many hydraulically active fractures in the deeper homothermic portion of the hole. The identification of discrete groundwater flow at many depths is supported by additional evidence concerning fracture occurrence, including continuous core visual inspection, acoustic televiewer logs, and tests for hydraulic conductivity using straddle packers as well as rock core VOC data, where available, that show deep penetration and many migration pathways. Confidence in the use of temperature profiles and the conceptual model is provided by numerical simulation and the demonstrated reproducibility of the evolution of the temperature signal measured in the lined holes with and without heating. This approach for using temperature profiling in lined holes with heating is a practical advance in fractured rock hydrogeology because the liners are readily available, the equipment needed for heating is low cost and rugged, and the time needed to obtain the profiles is not excessive for most projects.

  10. Hydraulic Fracture and Toughening of a Brittle Layer Bonded to a Hydrogel

    NASA Astrophysics Data System (ADS)

    Lucantonio, Alessandro; Noselli, Giovanni; Trepat, Xavier; DeSimone, Antonio; Arroyo, Marino

    2015-10-01

    Brittle materials propagate opening cracks under tension. When stress increases beyond a critical magnitude, then quasistatic crack propagation becomes unstable. In the presence of several precracks, a brittle material always propagates only the weakest crack, leading to catastrophic failure. Here, we show that all these features of brittle fracture are fundamentally modified when the material susceptible to cracking is bonded to a hydrogel, a common situation in biological tissues. In the presence of the hydrogel, the brittle material can fracture in compression and can hydraulically resist cracking in tension. Furthermore, the poroelastic coupling regularizes the crack dynamics and enhances material toughness by promoting multiple cracking.

  11. Downhole microseismic monitoring of hydraulic fracturing: a full-waveform approach for complete moment tensor inversion and stress estimation

    E-print Network

    Song, Fuxian

    2010-01-01

    Downhole microseismics has gained in popularity in recent years as a way to characterize hydraulic fracturing sources and to estimate in-situ stress state. Conventional approaches only utilize part of the information ...

  12. A nonlocal model for fluid-structure interaction with applications in hydraulic fracturing

    E-print Network

    Turner, Daniel Z

    2012-01-01

    Modeling important engineering problems related to flow-induced damage (in the context of hydraulic fracturing among others) depends critically on characterizing the interaction of porous media and interstitial fluid flow. This work presents a new formulation for incorporating the effects of pore pressure in a nonlocal representation of solid mechanics. The result is a framework for modeling fluid-structure interaction problems with the discontinuity capturing advantages of an integral based formulation. A number of numerical examples are used to show that the proposed formulation can be applied to measure the effect of leak-off during hydraulic fracturing as well as modeling consolidation of fluid saturated rock and surface subsidence caused by fluid extraction from a geologic reservoir. The formulation incorporates the effect of pore pressure in the constitutive description of the porous material in a way that is appropriate for nonlinear materials, easily implemented in existing codes, straightforward in i...

  13. Investigation of post hydraulic fracturing well cleanup physics in the Cana Woodford Shale

    NASA Astrophysics Data System (ADS)

    Lu, Rong

    Hydraulic fracturing was first carried out in the 1940s and has gained popularity in current development of unconventional resources. Flowing back the fracturing fluids is critical to a frac job, and determining well cleanup characteristics using the flowback data can help improve frac design. It has become increasingly important as a result of the unique flowback profiles observed in some shale gas plays due to the unconventional formation characteristics. Computer simulation is an efficient and effective way to tackle the problem. History matching can help reveal some mechanisms existent in the cleanup process. The Fracturing, Acidizing, Stimulation Technology (FAST) Consortium at Colorado School of Mines previously developed a numerical model for investigating the hydraulic fracturing process, cleanup, and relevant physics. It is a three-dimensional, gas-water, coupled fracture propagation-fluid flow simulator, which has the capability to handle commonly present damage mechanisms. The overall goal of this research effort is to validate the model on real data and to investigate the dominant physics in well cleanup for the Cana Field, which produces from the Woodford Shale in Oklahoma. To achieve this goal, first the early time delayed gas production was explained and modeled, and a simulation framework was established that included all three relevant damage mechanisms for a slickwater fractured well. Next, a series of sensitivity analysis of well cleanup to major reservoir, fracture, and operational variables was conducted; five of the Cana wells' initial flowback data were history matched, specifically the first thirty days' gas and water producing rates. Reservoir matrix permeability, net pressure, Young's modulus, and formation pressure gradient were found to have an impact on the gas producing curve's shape, in different ways. Some moderately good matches were achieved, with the outcome of some unknown reservoir information being proposed using the corresponding inputs from the history matching study. It was also concluded that extended shut-in durations after fracturing all the stages do not delay production in the overall situation. The success of history matching will further knowledge of well cleanup characteristics in the Cana Field, enable the future usage of this tool in other hydraulically fractured gas wells, and help operators optimize the flowback operations. Future improvements can be achieved by further developing the current simulator so that it has the capability of optimizing its grids setting every time the user changes the inputs, which will result in better stability when the relative permeability setting is modified.

  14. New tracers identify hydraulic fracturing fluids and accidental releases from oil and gas operations.

    PubMed

    Warner, N R; Darrah, T H; Jackson, R B; Millot, R; Kloppmann, W; Vengosh, A

    2014-11-01

    Identifying the geochemical fingerprints of fluids that return to the surface after high volume hydraulic fracturing of unconventional oil and gas reservoirs has important applications for assessing hydrocarbon resource recovery, environmental impacts, and wastewater treatment and disposal. Here, we report for the first time, novel diagnostic elemental and isotopic signatures (B/Cl, Li/Cl, ?11B, and ?7Li) useful for characterizing hydraulic fracturing flowback fluids (HFFF) and distinguishing sources of HFFF in the environment. Data from 39 HFFFs and produced water samples show that B/Cl (>0.001), Li/Cl (>0.002), ?11B (25-31‰) and ?7Li (6-10‰) compositions of HFFF from the Marcellus and Fayetteville black shale formations were distinct in most cases from produced waters sampled from conventional oil and gas wells. We posit that boron isotope geochemistry can be used to quantify small fractions (?0.1%) of HFFF in contaminated fresh water and likely be applied universally to trace HFFF in other basins. The novel environmental application of this diagnostic isotopic tool is validated by examining the composition of effluent discharge from an oil and gas brine treatment facility in Pennsylvania and an accidental spill site in West Virginia. We hypothesize that the boron and lithium are mobilized from exchangeable sites on clay minerals in the shale formations during the hydraulic fracturing process, resulting in the relative enrichment of boron and lithium in HFFF. PMID:25327769

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

    NASA Astrophysics Data System (ADS)

    Boudet, H. S.

    2013-12-01

    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.

  16. Biocides in hydraulic fracturing fluids: a critical review of their usage, mobility, degradation, and toxicity.

    PubMed

    Kahrilas, Genevieve A; Blotevogel, Jens; Stewart, Philip S; Borch, Thomas

    2015-01-01

    Biocides are critical components of hydraulic fracturing ("fracking") fluids used for unconventional shale gas development. Bacteria may cause bioclogging and inhibit gas extraction, produce toxic hydrogen sulfide, and induce corrosion leading to downhole equipment failure. The use of biocides such as glutaraldehyde and quaternary ammonium compounds has spurred a public concern and debate among regulators regarding the impact of inadvertent releases into the environment on ecosystem and human health. This work provides a critical review of the potential fate and toxicity of biocides used in hydraulic fracturing operations. We identified the following physicochemical and toxicological aspects as well as knowledge gaps that should be considered when selecting biocides: (1) uncharged species will dominate in the aqueous phase and be subject to degradation and transport whereas charged species will sorb to soils and be less bioavailable; (2) many biocides are short-lived or degradable through abiotic and biotic processes, but some may transform into more toxic or persistent compounds; (3) understanding of biocides' fate under downhole conditions (high pressure, temperature, and salt and organic matter concentrations) is limited; (4) several biocidal alternatives exist, but high cost, high energy demands, and/or formation of disinfection byproducts limits their use. This review may serve as a guide for environmental risk assessment and identification of microbial control strategies to help develop a sustainable path for managing hydraulic fracturing fluids. PMID:25427278

  17. Iodide, bromide, and ammonium in hydraulic fracturing and oil and gas wastewaters: environmental implications.

    PubMed

    Harkness, Jennifer S; Dwyer, Gary S; Warner, Nathaniel R; Parker, Kimberly M; Mitch, William A; Vengosh, Avner

    2015-02-01

    The expansion of unconventional shale gas and hydraulic fracturing has increased the volume of the oil and gas wastewater (OGW) generated in the U.S. Here we demonstrate that OGW from Marcellus and Fayetteville hydraulic fracturing flowback fluids and Appalachian conventional produced waters is characterized by high chloride, bromide, iodide (up to 56 mg/L), and ammonium (up to 420 mg/L). Br/Cl ratios were consistent for all Appalachian brines, which reflect an origin from a common parent brine, while the I/Cl and NH4/Cl ratios varied among brines from different geological formations, reflecting geogenic processes. There were no differences in halides and ammonium concentrations between OGW originating from hydraulic fracturing and conventional oil and gas operations. Analysis of discharged effluents from three brine treatment sites in Pennsylvania and a spill site in West Virginia show elevated levels of halides (iodide up to 28 mg/L) and ammonium (12 to 106 mg/L) that mimic the composition of OGW and mix conservatively in downstream surface waters. Bromide, iodide, and ammonium in surface waters can impact stream ecosystems and promote the formation of toxic brominated-, iodinated-, and nitrogen disinfection byproducts during chlorination at downstream drinking water treatment plants. Our findings indicate that discharge and accidental spills of OGW to waterways pose risks to both human health and the environment. PMID:25587644

  18. Recharge and pumping hydraulics in a till drumlin above fractured bedrock (Massachusetts, USA)

    NASA Astrophysics Data System (ADS)

    Ostendorf, David W.; Lukas, William G.; Rotaru, Camelia

    2015-02-01

    Recharge and pumping hydraulics of a till-mantled bedrock are analyzed with existing closed-form theory and 12 years of monthly water levels in cluster wells from Scituate Hill, a glacial till drumlin in eastern Massachusetts (USA). The weathered brown till atop Scituate Hill is an unconfined aquifer, delivering steady recharge and a seasonally varying recharge-head fluctuation to the unweathered gray till aquitard beneath it. The water-table fluctuations generate no seasonally varying flow field in the gray till, due to the relatively low hydraulic diffusivity of the brown till. Nearby irrigation pumps drilled into the underlying Dedham Granite in 2011 have introduced seasonal drawdown, and the gray till leaks into the fractured bedrock aquifer. The leakage reflects the moderate diffusivity of the gray till and the relatively high hydraulic diffusivity of the fractured bedrock. Both seasonal disturbances are mildly attenuated across the gray till, so that the Dedham Granite senses recharge, while the water table in Scituate Hill is drawn down by irrigation pumping. Steady and seasonal gray till data are accordingly used to calibrate the transmissivity and storativity of the fractured bedrock and specific yield of the brown till, with physically plausible values.

  19. Stimuli Responsive/Rheoreversible Hydraulic Fracturing Fluids for Enhanced Geothermal Energy Production(Part II)

    NASA Astrophysics Data System (ADS)

    Bonneville, A.; Jung, H. B.; Shao, H.; Kabilan, S.; Um, W.; Carroll, K. C.; Varga, T.; Suresh, N.; Stephens, S.; Fernandez, C. A.

    2014-12-01

    We have used an environmentally friendly and recyclable hydraulic fracturing fluid - diluted aqueous solutions of polyallylamine or PAA - for reservoir stimulation in Enhanced Geothermal System (EGS). This fluid undergoes a controlled and large volume expansion with a simultaneous increase in viscosity triggered by CO2 at EGS temperatures. We are presenting here the results of laboratory-scale hydraulic fracturing experiment using the fluid on small cylindrical rock cores (1.59 cm in diameter and 5.08 cm in length) from the Coso geothermal field in California. Rock samples consisted of Mesozoic diorite metamorphosed to greenschist facies. The experiments were conducted on 5 samples for realistic ranges of pressures (up to 275 bar) and temperatures (upt to 210 °C) for both the rock samples and the injected fluid. After fracturation, cores were subjected to a CO2 leakage test, injection of KI solution, and X-ray microtomography (XMT) scanning to examine the formation and distribution of fractures. The design and conduct of these experiments will be presented and discussed in details. Based on the obtained XMT images, Computational Fluid Dynamics (CFD) simulations were then performed to visualize hydraulic fractures and compute the bulk permeability. OpenFOAM (OpenCFD Ltd., Reading, UK), was used to solve the steady state simulation. The flow predictions, based upon the laminar, 3-D, incompressible Navier-Stokes equations for fluid mass and momentum, show the remarkable stimulation of the permeability in the core samples and demonstrate the efficiency of such a CO2 triggered fluid in EGS.

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

    SciTech Connect

    Shao, Hongbo; Kabilan, Senthil; Stephens, Sean A.; Suresh, Niraj; Beck, Anthon NR; Varga, Tamas; Martin, Paul F.; Kuprat, Andrew P.; Jung, Hun Bok; Um, Wooyong; Bonneville, Alain; Heldebrant, David J.; Carroll, KC; Moore, Joseph; Fernandez, Carlos A.

    2015-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  2. Stress trajectory and advanced hydraulic-fracture simulations for the Eastern Gas Shales Project. Final report, April 30, 1981-July 30, 1983

    SciTech Connect

    Advani, S.H.; Lee, J.K.

    1983-01-01

    A summary review of hydraulic fracture modeling is given. Advanced hydraulic fracture model formulations and simulation, using the finite element method, are presented. The numerical examples include the determination of fracture width, height, length, and stress intensity factors with the effects of frac fluid properties, layered strata, in situ stresses, and joints. Future model extensions are also recommended. 66 references, 23 figures.

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

    SciTech Connect

    David S. Schechter

    2004-10-10

    This report describes the work performed during the third 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 artificial fractured cores (AFCs) and X-ray CT to examine the physical mechanisms of bypassing in HFR and NFR that eventually result in more efficient CO{sub 2} flooding in heterogeneous or fracture-dominated reservoirs. To achieve this objective, in this period we concentrated our effort on modeling fluid flow through rough fractures and investigating the grid orientation effect in rectangular grid blocks particularly at high mobility ratio as our precursor to use a compositional simulator. We are developing a robust simulator using Voronoi grids to accurately represent natural and induced fractures. We are also verifying the accuracy of the simulation using scaled laboratory experiments to provide a benchmark for our simulation technique. No such simulator currently exists so this capability will represent a major breakthrough in simulation of gas injection in fractured systems. The following sections outline the results that appear in this report.

  4. Edit paper Methods for Large Scale Hydraulic Fracture Monitoring

    E-print Network

    Ely, Gregory

    2013-01-01

    In this paper we propose computationally efficient and robust methods for estimating the moment tensor and location of micro-seismic event(s) for large search volumes. Our contribution is two-fold. First, we propose a novel joint-complexity measure, namely the sum of nuclear norms which while imposing sparsity on the number of fractures (locations) over a large spatial volume, also captures the rank-1 nature of the induced wavefield pattern. This wavefield pattern is modeled as the outer-product of the source signature with the amplitude pattern across the receivers from a seismic source. A rank-1 factorization of the estimated wavefield pattern at each location can therefore be used to estimate the seismic moment tensor using the knowledge of the array geometry. In contrast to existing work this approach allows us to drop any other assumption on the source signature. Second, we exploit the recently proposed first-order incremental projection algorithms for a fast and efficient implementation of the resulting...

  5. The effect of different posts on fracture strength of roots with vertical fracture and re-attached fragments.

    PubMed

    Ozcopur, B; Akman, S; Eskitascioglu, G; Belli, S

    2010-08-01

    The aim of this in vitro study was to test the effect of different post systems on fracture strength of roots with re-attached fragments. Root canals of eighty extracted single-rooted human teeth were instrumented (ProFile) and randomly divided into two groups. The roots in the first group were vertically cracked, and the fragments were re-attached using Super Bond C&B (Sun Medical, Tokya, Japan). The roots in the second group were kept sound. Obturation of the roots was performed with MetaSEAL (Sun Medical) and gutta-percha. Post spaces were prepared, and the roots were restored with one of the followings: UniCore (Ultradent), Everstick (Stick Tech), Ribbond (Ribbond), ParaPost (Coltene/Whaledent) (n = 10). Four mm high build-ups were created (Clearfil DC Bond Core; Kuraray, Tokyo, Japan). Compressive loading of the samples was performed after 24 h (1 mm min(-1)). Mean load necessary to fracture each sample was recorded (Newton) and statistically analysed (One-way anova, t-tests). ParaPost showed the highest fracture strength among the roots with re-attached fragments (P < 0.05). UniCore and ParaPost systems showed similar fracture strength in the sound roots (P > 0.05). Re-attached fragments significantly reduced the fracture strength of roots in UniCore group (P = 0.000). Ribbond post showed mostly repairable fractures. Metal post (ParaPost) showed the highest fracture strength in the roots with re-attached fragments; however, fracture pattern was 41% non-repairable. Re-attached fragments significantly reduced the fracture strength of the roots in UniCore group. Prefabricated posts showed similar fracture strength in the sound roots. Customized post systems EverStick and Ribbond showed mostly repairable failure after loading in sound roots or roots with re-attached fragments. PMID:20406354

  6. Stimuli Responsive/Rheoreversible Hydraulic Fracturing Fluids for Enhanced Geothermal Energy Production (Part I)

    NASA Astrophysics Data System (ADS)

    Fernandez, C. A.; Jung, H. B.; Shao, H.; Bonneville, A.; Heldebrant, D.; Hoyt, D.; Zhong, L.; Holladay, J.

    2014-12-01

    Cost-effective yet safe creation of high-permeability reservoirs inside deep crystalline bedrock is the primary challenge for the viability of enhanced geothermal systems and unconventional oil/gas recovery. Current reservoir stimulation processes utilize brute force (hydraulic pressures in the order of hundreds of bar) to create/propagate fractures in the bedrock. Such stimulation processes entail substantial economic costs ($3.3 million per reservoir as of 2011). Furthermore, the environmental impacts of reservoir stimulation are only recently being determined. Widespread concerns about the environmental contamination have resulted in a number of regulations for fracturing fluids advocating for greener fracturing processes. To reduce the costs and environmental impact of reservoir stimulation, we developed an environmentally friendly and recyclable hydraulic fracturing fluid that undergoes a controlled and large volume expansion with a simultaneous increase in viscosity triggered by CO2 at temperatures relevant for reservoir stimulation in Enhanced Geothermal System (EGS). The volume expansion, which will specifically occurs at EGS depths of interest, generates an exceptionally large mechanical stress in fracture networks of highly impermeable rock propagating fractures at effective stress an order of magnitude lower than current technology. This paper will concentrate on the presentation of this CO2-triggered expanding hydrogel formed from diluted aqueous solutions of polyallylamine (PAA). Aqueous PAA-CO2 mixtures also show significantly higher viscosities than conventional rheology modifiers at similar pressures and temperatures due to the cross-linking reaction of PAA with CO2, which was demonstrated by chemical speciation studies using in situ HP-HT 13C MAS-NMR. In addtion, PAA shows shear-thinning behavior, a critical advantage for the use of this fluid system in EGS reservoir stimulation. The high pressure/temperature experiments and their results as well as the CFD modeling are presented in a companion paper.

  7. A policy and impact analysis of hydraulic fracturing in the Marcellus Shale region: A wildlife perspective

    NASA Astrophysics Data System (ADS)

    Caldwell, Jennifer A.

    Hydraulic fracturing for natural gas in the Marcellus Shale (underlying about 24 mil ha in New York, Pennsylvania, Maryland, West Virginia, Ohio, and Virginia) has become a politically charged issue, primarily because of concerns about drinking water safety and human health. This thesis examines hydraulic fracturing in the Marcellus Shale region using an E3 analysis; looking at the energy potential of the natural gas in the basin, the economics of shale gas extraction, and the environmental impact from a wildlife perspective. The thesis also examines the federal, regional, and state policies and regulations that apply to the industry. The Marcellus Shale has the most technically recoverable gas of any basin in the United States at 141 trillion cubic feet. Based on current U.S. consumption, the Marcellus could provide all the natural gas used in the country for 5.5 years. Income from natural gas development comes primarily from jobs (direct such as gas workers, indirect such as equipment suppliers, and induced jobs which are created when direct workers spend their earnings in a community) and taxes and fees. From a wildlife perspective, environmental effects are primarily on habitat. Terrestrial habitat effects are primarily due to landscape fragmentation from clearing of land for well pad development, which removes mature forest and creates edge habitat. An increase in forest edges is associated with an increase in nest predation and brood parasitism, which could put edge-nesting songbird species at risk. Aquatic habitat effects are less well understood. Hydraulic fracturing requires up to 19 mil l of water per well fracture and in the Marcellus Shale region, most of that comes from surface water sources. Removal of water from surface water sources can increase sedimentation, alter the temperature, and change the chemistry of the water, resulting in changes in the biodiversity of the water source. Federal oversight of natural gas production is managed through a variety of regulations, primarily the National Environmental Protection Act, the Clean Water Act (although hydraulic fracturing was exempted from the erosion control provisions via the Energy Policy Act of 2005), the Clean Air Act, the Endangered Species Act, the Mineral Leasing Act, the Natural Gas Act, and several others. The Susquehanna River Basin Commission and the Delaware River Basin Commission (DRBC) regulate water usage in their respective watersheds, although the DRBC has yet to finalize the regulations for water usage for hydraulic fracturing in the Delaware River Basin. Each of the states in the region regulate the industry in different ways. Given that hydraulic fracturing will continue, further research is needed on habitat impacts, especially on aquatic habitats. Best Management Practices need to be agreed upon by stakeholders (industry, regulators, non-governmental organizations). Federal regulation is required to force operators to consistently disclose the chemicals used in the fracturing fluid and to mandate erosion/sediment control. An Ohio River Basin Commission needs to be chartered to manage water use in the Ohio River Basin, as it is in the Susquehanna and Delaware River basins. States need to actively manage reclamation activities to ensure native plantings.

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

    USGS Publications Warehouse

    Paillet, F.L.

    1993-01-01

    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.

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

    SciTech Connect

    Lorenz, J.C. ); Hill, R.E. )

    1991-01-01

    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.

  10. Simulating the hydraulic stimulation of multiple fractures in an anisotropic stress field applying the discrete element method

    NASA Astrophysics Data System (ADS)

    Zeeb, Conny; Frühwirt, Thomas; Konietzky, Heinz

    2015-04-01

    Key to a successful exploitation of deep geothermal reservoirs in a petrothermal environment is the hydraulic stimulation of the host rock to increase permeability. The presented research investigates the fracture propagation and interaction during hydraulic stimulation of multiple fractures in a highly anisotropic stress field. The presented work was conducted within the framework of the OPTIRISS project, which is a cooperation of industry partners and universities in Thuringia and Saxony (Federal States of Germany) and was funded by the European Fond for Regional Development. One objective was the design optimization of the subsurface geothermal heat exchanger (SGHE) by means of numerical simulations. The presented simulations were conducted applying 3DEC (Itasca™), a software tool based on the discrete element method. The simulation results indicate that the main direction of fracture propagation is towards lower stresses and thus towards the biosphere. Therefore, barriers might be necessary to limit fracture propagation to the designated geological formation. Moreover, the hydraulic stimulation significantly alters the stresses in the vicinity of newly created fractures. Especially the change of the minimum stress component affects the hydraulic stimulation of subsequent fractures, which are deflected away from the previously stimulated fractures. This fracture deflection can render it impossible to connect all fractures with a second borehole for the later production. The results of continuative simulations indicate that a fracture deflection cannot be avoided completely. Therefore, the stage alignment was modified to minimize fracture deflection by varying (1) the pauses between stages, (2) the spacing's between adjacent stages, and (3) the angle between stimulation borehole and minimum stress component. An optimum SGHE design, which implies that all stimulated fractures are connected to the production borehole, can be achieved by aligning the stimulation borehole at an angle of 45° to the minimum stress component. Furthermore, longer pauses between injection stages and higher spacing between stages promote more consistent fracture geometries. The simulation results indicate that fractures tend to propagate in random directions away from the stress shadows of existing fractures, even for a stage spacing of 200 m. This fracture deflection may result in undesirable fracture propagation directions or produce shortcuts between fracture stages. A careful planning of the stage alignment seems the most promising procedure to counteract/control fracture deflection.

  11. Implementation of the Ensemble Kalman Filter in the Characterization of Hydraulic Fractures in Shale Gas Reservoirs by Integrating Downhole Temperature Sensing Technology 

    E-print Network

    Moreno, Jose A

    2014-08-12

    Multi-stage hydraulic fracturing in horizontal wells has demonstrated successful results for developing unconventional low-permeability oil and gas reservoirs. Despite being vastly implemented by different operators across North America, hydraulic...

  12. Open Axial and True Vertical Ankle Dislocation Without Malleolar Fractures: A Case Report.

    PubMed

    Bakshi, Kapil

    2016-01-01

    Tibiotalar dislocation is rare and usually associated with a high-velocity, high-energy impact or extreme sporting injuries. I describe complete tibiotalar dislocation from an unusual mechanism. A 22-year-old mechanic was sitting under a hydraulic lift when it began to leak, lowering the engine on which he was working onto his right lower thigh. This heavy load, without rotational force or high-velocity impact, was transmitted down his foreleg. Because his foot was fixed to the ground, the talus was proximally and vertically displaced, and the distal tibia was forced to the ground, beside his foot, and was contaminated with sand and grease. The circumferential ligament complexes and capsule were completely transected, but, despite a severely disrupted dorsal and capsular blood supply, talar vasculature remained adequate. In the emergency department, gentle traction restored impaired circulation. No malleolar fractures were seen. The wound was meticulously irrigated with saline and povidone-iodine and debrided. Cefepime, 2 g, was given twice daily. In surgery, the unstable joint was transfixed with two thick Kirschner wires, passed retrograde. Interrupted sutures were placed in the anterior capsule and anterior third of the lateral ligament without additional incisions. The wound healed aseptically. The Kirschner wires were removed at 6 weeks. The joint space was only minimally reduced. He returned to work after 4 months. His ankle-hindfoot score was 90/100 at 18 months, he could jog at 24 months, and he was still asymptomatic at 36 months. The case illustrates the importance of preserving talar circulation and treatment within the "golden hour." PMID:25524434

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

    PubMed

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

    2014-06-01

    In this study, a side-by-side comparison of two pilot-scale vertical subsurface flow constructed wetlands (6.2 m(2)×0.85 m, q(i)=95 L/m(2) d, ?(n)=3.5 d) 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 8 h on/4 h 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

  14. Analysis of hydraulic fracturing additives by LC/Q-TOF-MS.

    PubMed

    Ferrer, Imma; Thurman, E Michael

    2015-08-01

    The chemical additives used in fracturing fluids can be used as tracers of water contamination caused by hydraulic fracturing operations. For this purpose, a complete chemical characterization is necessary using advanced analytical techniques. Liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (LC/Q-TOF-MS) was used to identify chemical additives present in flowback and produced waters. Accurate mass measurements of main ions and fragments were used to characterize the major components of fracking fluids. Sodium adducts turned out to be the main molecular adduct ions detected for some additives due to oxygen-rich structures. Among the classes of chemical components analyzed by mass spectrometry include gels (guar gum), biocides (glutaraldehyde and alkyl dimethyl benzyl ammonium chloride), and surfactants (cocamidopropyl dimethylamines, cocamidopropyl hydroxysultaines, and cocamidopropyl derivatives). The capabilities of accurate mass and MS-MS fragmentation are explored for the unequivocal identification of these compounds. A special emphasis is given to the mass spectrometry elucidation approaches used to identify a major class of hydraulic fracturing compounds, surfactants. PMID:26044738

  15. Performance of hydraulic fracturing and matrix acidizing in horizontal wellbores -- Offshore Qatar

    SciTech Connect

    Edwards, M.G.R.; Pongratz, R.

    1995-11-01

    Considerable debate in the Middle East has centered upon what was previously felt to be two separate methods of enhancing revenues and daily production; hydraulic fracturing and horizontal drilling. In an effort to maximize return on investment, these two issues have been successfully combined in other areas of the world. In order to establish the suitability of this technology in this area, two horizontal wells with over 3,050m (10,000ft) of lateral section were drilled into the Cretaceous Kharaib formation, overlying the North Field, Offshore Qatar. A massive stimulation program was performed in order to evaluate the most feasible stimulation method from both a technical and economical perspective for further field development considerations.Three propped hydraulic fracturing treatments were performed using 183, 500kg (403, 700lb) of 20/40 mesh sand, and seventeen acid matrix treatments placing over 3,217,250l (850,000gals) of HCL into the lateral sections of both wells. This paper describes the performance, operation and logistical support required to complete this offshore operation with join a minimal time frame. The use of a mobile offshore jack-up platform, whereby a land based fracturing spread was placed onto the deck of a converted drilling rig is described.

  16. Hydraulics.

    ERIC Educational Resources Information Center

    Decker, Robert L.; Kirby, Klane

    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)…

  17. A Semi-Analytic Solution for Flow in Finite-Conductivity Vertical Fractures Using Fractal Theory 

    E-print Network

    Cossio Santizo, Manuel

    2012-10-19

    for the construction of fractal networks of a variety of geometrical and connectivity properties. 12 Figure 2.6 — Schematic of a fractal fracture network embedded in a Euclidean matrix (Chang and Yortsos 1990) Flamenco-López and Camacho-Velázquez... the fractal model of Chang and Yortsos (1990) to consider a hydraulically fractured well. He also observed a power-law behavior during the linear and radial flow periods. Camacho-Velázquez et al (2008) applied the fractal model to generate a series...

  18. Use of a speed equation for numerical simulation of hydraulic fractures

    E-print Network

    Linkov, Alexander M

    2011-01-01

    The paper treats the propagation of a hydraulically driven crack. We explicitly write the local speed equation, which facilitates using the theory of propagating interfaces. It is shown that when neglecting the lag between the liquid front and the crack tip, the lubrication PDE yields that a solution satisfies the speed equation identically. This implies that for zero or small lag, the boundary value problem appears ill-posed when solved numerically. We suggest e - regularization, which consists in employing the speed equation together with a prescribed BC on the front to obtain a new BC formulated at a small distance behind the front rather than on the front itself. It is shown that - regularization provides accurate and stable results with reasonable time expense. It is also shown that the speed equation gives a key to proper choice of unknown functions when solving a hydraulic fracture problem numerically.

  19. Assessment of the Acute and Chronic Health Hazards of Hydraulic Fracturing Fluids.

    PubMed

    Wattenberg, Elizabeth V; Bielicki, Jeffrey M; Suchomel, Ashley E; Sweet, Jessica T; Vold, Elizabeth M; Ramachandran, Gurumurthy

    2015-01-01

    There is growing concern about how hydraulic fracturing affects public health because this activity involves handling large volumes of fluids that contain toxic and carcinogenic constituents, which are injected under high pressure through wells into the subsurface to release oil and gas from tight shale formations. The constituents of hydraulic fracturing fluids (HFFs) present occupational health risks because workers may be directly exposed to them, and general public health risks because of potential air and water contamination. Hazard identification, which focuses on the types of toxicity that substances may cause, is an important step in the complex health risk assessment of hydraulic fracturing. This article presents a practical and adaptable tool for the hazard identification of HFF constituents, and its use in the analysis of HFF constituents reported to be used in 2,850 wells in North Dakota between December 2009 and November 2013. Of the 569 reported constituents, 347 could be identified by a Chemical Abstract Service Registration Number (CASRN) and matching constituent name. The remainder could not be identified either because of trade secret labeling (210) or because of an invalid CASRN (12). Eleven public databases were searched for health hazard information on thirteen health hazard endpoints for 168 identifiable constituents that had at least 25 reports of use. Health hazard counts were generated for chronic and acute endpoints, including those associated with oral, inhalation, ocular, and dermal exposure. Eleven of the constituents listed in the top 30 by total health hazard count were also listed in the top 30 by reports of use. This includes naphthalene, which along with benzyl chloride, has the highest health hazard count. The top 25 constituents reportedly used in North Dakota largely overlap with those reported for Texas and Pennsylvania, despite different geologic formations, target resources (oil vs. gas), and disclosure requirements. Altogether, this database provides a public health tool to help inform stakeholders about potential health hazards, and to aid in the reformulation of less hazardous HFFs. PMID:25894916

  20. The Role of Toxicological Science in Meeting the Challenges and Opportunities of Hydraulic Fracturing

    PubMed Central

    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

    2014-01-01

    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

  1. Pumping-Test Evaluation of Fault-Zone Hydraulic Properties in a Fractured Sandstone

    NASA Astrophysics Data System (ADS)

    Johnson, N. M.

    2014-12-01

    Subzones of both reduced and enhanced permeability are often ascribed to fault zones, consistent with a fault-core/damage-zone conceptualization, with associated implications for assessing potential contaminant transport. Within this context, a 31-day pumping test was conducted in relation to a relatively minor, 2000 m long fault zone cutting fractured Cretaceous sandstone interbedded with siltstone and shale at a groundwater remediation site in the Simi Hills of southern California during March-April 2013. Our objective was to evaluate the potential hydrogeologic influence of the fault zone on groundwater movement across and along it by observing the spatial patterns of drawdown and estimated hydraulic properties. A 122 m deep open borehole was pumped at a constant rate of approximately 112 L/min while monitoring hydraulic heads in 14 observation wells, two completed with multi-level systems, within 750 m of the pumping well. Hydraulic heads were monitored for more than 9 months before, during, and after the test. Prior to the test, we used the site's three-dimensional, equivalent-porous-media groundwater flow model to anticipate the potential response of alternative fault-zone permeability structures. The results suggest that the fault zone may be slightly more permeable (by a factor of about 2 or less) and less confined than the fractured sandstone away from the fault, and is not a significant barrier to groundwater flow across it. Within the areal extent of observed drawdown, the site's hydrostratigraphic structures exhibited a relatively greater hydraulic influence. The pattern and magnitude of observed drawdown lie within the range of pre-test model simulations, and the test results are now being used to revise and recalibrate the model.

  2. Fractured: Experts examine the contentious issue of hydraulic fracturing water use 

    E-print Network

    Wythe, Kathy

    2013-01-01

    . According to a study conducted by Drs. Jean-Philippe Nicot and Bridget Scanlon of ?e University of Texas at Austin?s Bureau of Economic Geology and published in Environmental Science & Technology, the cumulative water use for shale gas production... technologies to reduce the amount of water used in fracturing jobs. Blackmon spoke in October ???? at the Growing Texas conference, organized by the Texas A&M Energy Institute. One new development, Blackmon said, is a gel that keeps brine water from...

  3. Bench-mark solution for a penny-shaped hydraulic fracture driven by a thinning fluid

    E-print Network

    Linkov, Aleksandr

    2015-01-01

    The paper presents a solution for axisymmetric propagation of a penny-shaped crack driven by a thinning fluid. The solution to the accuracy of four significant digits, at least, is obtained on the basis of the modified formulation of hydraulic fracture problem by employing the particle velocity, rather than conventionally used flux. This serves to properly organize iterations in the opening after reducing the problem to the self-similar form. Numerical results obtained show relatively small dependence of self-similar quantities (fracture radius, propagation speed, opening, particle velocity, pressure, flux) on the behavior index of a thinning fluid. The results provide bench marks for the accuracy control of truly 3D simulators and they serve for assigning an apparent viscosity when simulating the action of a thinning fluid by replacing it with an equivalent Newtonian fluid.

  4. Stress wave propagationin the site 12 hydraulic/explosive fracturing experiment

    SciTech Connect

    Boade, R. R.; Reed, R. P.

    1980-05-01

    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 sound understanding of the nature of the blasting operations, a rather extensive array of stress gages, accelerometers, and time-of-arrival gages was installed in the rock mass in the vacinity of the explosive to monitor the dynamic events initiated by the detonation. These gages provided considerable amounts of information which were useful in evaluating overall results of the experiment. Details of the gage array, of the data, of analysis methods, and of the results and conclusions are considered in the report.

  5. In-situ heat transfer in man-made hydraulically fractured geothermal energy reservoirs

    SciTech Connect

    Murphy, H.D.; Tester, J.W.; Grigsby, C.; Potter, R.M.

    1980-01-01

    Heat extraction results and reservoir assessments are discussed for 2 geothermal reservoirs created by hydraulic fracturing of hot granitic formations on the west flank of the Valles Caldera, a dormant volcano, in the Jemez Mt. of New Mexico. The second reservoir was created in a deeper rock formation using the same pair of operation wells, and appears to be approximately 8 times larger in heat transfer area than the first reservoir. Despite the larger size, the flow impedance of the second reservoir is the same as that of the first, and the down-hole water losses to the surrounding rock were requirements as a building block for commercial sized, multiply fractured reservoirs - 6 or 7 reservoirs similar to the latest one would produce 20 to 50 MW (T) for 20 years.

  6. On a 2D hydro-mechanical lattice approach for modelling hydraulic fracture

    E-print Network

    Grassl, Peter; Gallipoli, Domenico; Wheeler, Simon J

    2014-01-01

    A 2D lattice approach to describe hydraulic fracturing is presented. The interaction of fluid pressure and mechanical response is described by Biot's theory. The lattice model is applied to the analysis of a thick-walled cylinder, for which an analytical solution for the elastic response is derived. The numerical results obtained with the lattice model agree well with the analytical solution. Furthermore, the coupled lattice approach is applied to the fracture analysis of the thick-walled cylinder. It is shown that the proposed lattice approach provides results that are independent of the mesh size. Moreover, a strong geometrical size effect on nominal strength is observed which lies between analytically derived lower and upper bounds. This size effect decreases with increasing Biot's coefficient.

  7. Robust Hydraulic Fracture Monitoring (HFM) of Multiple Time Overlapping Events Using a Generalized Discrete Radon Transform

    E-print Network

    Ely, Gregory

    2013-01-01

    In this work we propose a novel algorithm for multiple-event localization for Hydraulic Fracture Monitoring (HFM) through the exploitation of the sparsity of the observed seismic signal when represented in a basis consisting of space time propagators. We provide explicit construction of these propagators using a forward model for wave propagation which depends non-linearly on the problem parameters - the unknown source location and mechanism of fracture, time and extent of event, and the locations of the receivers. Under fairly general assumptions and an appropriate discretization of these parameters we first build an over-complete dictionary of generalized Radon propagators and assume that the data is well represented as a linear superposition of these propagators. Exploiting this structure we propose sparsity penalized algorithms and workflow for super-resolution extraction of time overlapping multiple seismic events from single well data.

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

    USGS Publications Warehouse

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

    2010-01-01

    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.

  9. Complementary hydro-mechanical coupled finite/discrete element and microseismic modelling to predict hydraulic fracture propagation in tight shale reservoirs

    NASA Astrophysics Data System (ADS)

    Profit, Matthew; Dutko, Martin; Yu, Jianguo; Cole, Sarah; Angus, Doug; Baird, Alan

    2015-11-01

    This paper presents a novel approach to predict the propagation of hydraulic fractures in tight shale reservoirs. Many hydraulic fracture modelling schemes assume that the fracture direction is pre-seeded in the problem domain discretisation. This is a severe limitation as the reservoir often contains large numbers of pre-existing fractures that strongly influence the direction of the propagating fracture. To circumvent these shortcomings, a new fracture modelling treatment is proposed where the introduction of discrete fracture surfaces is based on new and dynamically updated geometrical entities rather than the topology of the underlying spatial discretisation. Hydraulic fracturing is an inherently coupled engineering problem with interactions between fluid flow and fracturing when the stress state of the reservoir rock attains a failure criterion. This work follows a staggered hydro-mechanical coupled finite/discrete element approach to capture the key interplay between fluid pressure and fracture growth. In field practice, the fracture growth is hidden from the design engineer and microseismicity is often used to infer hydraulic fracture lengths and directions. Microseismic output can also be computed from changes of the effective stress in the geomechanical model and compared against field microseismicity. A number of hydraulic fracture numerical examples are presented to illustrate the new technology.

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

    SciTech Connect

    Kim, Jihoon; Um, Evan; Moridis, George

    2014-12-01

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

  11. Estimating hydraulic conductivity of fractured rocks from high-pressure packer tests with an Izbash's law-based empirical model

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Feng; Hu, Shao-Hua; Hu, Ran; Zhou, Chuang-Bing

    2015-04-01

    High-pressure packer test (HPPT) is an enhanced constant head packer test for characterizing the permeability of fractured rocks under high-pressure groundwater flow conditions. The interpretation of the HPPT data, however, remains difficult due to the transition of flow conditions in the conducting structures and the hydraulic fracturing-induced permeability enhancement in the tested rocks. In this study, a number of HPPTs were performed in the sedimentary and intrusive rocks located at 450 m depth in central Hainan Island. The obtained Q-P curves were divided into a laminar flow phase (I), a non-Darcy flow phase (II), and a hydraulic fracturing phase (III). The critical Reynolds number for the deviation of flow from linearity into phase II was 25-66. The flow of phase III occurred in sparsely to moderately fractured rocks, and was absent at the test intervals of perfect or poor intactness. The threshold fluid pressure between phases II and III was correlated with RQD and the confining stress. An Izbash's law-based analytical model was employed to calculate the hydraulic conductivity of the tested rocks in different flow conditions. It was demonstrated that the estimated hydraulic conductivity values in phases I and II are basically the same, and are weakly dependent on the injection fluid pressure, but it becomes strongly pressure dependent as a result of hydraulic fracturing in phase III. The hydraulic conductivity at different test intervals of a borehole is remarkably enhanced at highly fractured zone or contact zone, but within a rock unit of weak heterogeneity, it decreases with the increase of depth.

  12. Hydraulics.

    ERIC Educational Resources Information Center

    Engelbrecht, Nancy; And Others

    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…

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

    PubMed

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

    2013-12-01

    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

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

    NASA Astrophysics Data System (ADS)

    Hitchens, A.; Knee, K.

    2013-12-01

    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.

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

    SciTech Connect

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

    2013-12-01

    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.

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

    PubMed

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

    2014-01-21

    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

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

    SciTech Connect

    Polsky, Yarom; Anovitz, Lawrence {Larry} M; An, Ke; Carmichael, Justin R; Bingham, Philip R; Dessieux Jr, Luc Lucius

    2013-01-01

    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 questions regarding the translation of practice from O&G to both conventional geothermal and EGS applications. Lithological differences(sedimentary versus crystalline rocks, significantly greater formation temperatures and different desired fracture characteristics are among a number of factors that are likely to result in a gap of understanding of how to manage hydraulic fracturing practice for geothermal. Whereas the O&G community has had both the capital and the opportunity to develop its understanding of hydraulic fracturing operations empirically in the field as well through extensive R&D efforts, field testing opportunities for EGS are likely to be minimal due to the high expense of hydraulic fracturing field trials. A significant portion of the knowledge needed to guide the management of geothermal/EGS hydraulic fracturing operations will therefore likely have to come from experimental efforts and simulation. This paper describes ongoing efforts at Oak Ridge National Laboratory (ORNL) to develop an experimental capability to map the internal stresses/strains in core samples subjected to triaxial stress states and temperatures representative of EGS-like conditions using neutron diffraction based strain mapping techniques. This capability is being developed at ORNL\\'s Spallation Neutron Source, the world\\'s most powerful pulsed neutron source and is still in a proof of concept phase. A specialized pressure cell has been developed that permits independent radial and axial fluid pressurization of core samples, with axial flow through capability and a temperature rating up to 300 degrees C. This cell will ultimately be used to hydraulically pressurize EGS-representative core samples to conditions of imminent fracture and map the associated internal strain states of the sample. This will hopefully enable a more precise mapping of the rock material failure envelope, facilitate a more refined understanding of the mechanism of hydraulically induced rock fracture, particularly in crystalline rocks, and serve as a platform for validating and improving fracture simulation codes. The elements of the research program and preliminary strain mapping results of a Sierra White granite sample subjected only to compressive loading will be discussed in this paper.

  18. Sustainable Management of Flowback Water during Hydraulic Fracturing of Marcellus Shale for Natural Gas Production

    SciTech Connect

    Vidic, Radisav

    2015-01-24

    This study evaluated the feasibility of using abandoned mine drainage (AMD) as make- up water for the reuse of produced water for hydraulic fracturing. There is an abundance of AMD sources near permitted gas wells as documented in this study that can not only serve as makeup water and reduce the demand on high quality water resources but can also as a source of chemicals to treat produced water prior to reuse. The assessment of AMD availability for this purpose based on proximity and relevant regulations was accompanied by bench- and pilot-scale studies to determine optimal treatment to achieve desired water quality for use in hydraulic fracturing. Sulfate ions that are often present in AMD at elevated levels will react with Ba²? and Sr²? in produced water to form insoluble sulfate compounds. Both membrane microfiltration and gravity separation were evaluated for the removal of solids formed as a result of mixing these two impaired waters. Laboratory studies revealed that neither AMD nor barite formed in solution had significant impact on membrane filtration but that some produced waters contained submicron particles that can cause severe fouling of microfiltration membrane. Coagulation/flocculation was found to be an effective process for the removal of suspended solids and both bench- and pilot-scale studies revealed that optimal process conditions can consistently achieve the turbidity of the finished water below 5 NTU. Adjusting the blending ratio of AMD and produced water can achieve the desired effluent sulfate concentration that can be accurately predicted by chemical thermodynamics. Co-treatment of produced water and AMD will result in elevated levels of naturally occurring radioactive materials (NORM) in the solid waste generated in this process due to radium co-precipitation with barium sulfate. Laboratory studies revealed that the mobility of barite that may form in the subsurface due to the presence of sulfate in the fracturing fluid can be controlled by the addition of appropriate antiscalants.

  19. Simulation assessment of the direct-push permeameter for characterizing vertical variations in hydraulic conductivity

    USGS Publications Warehouse

    Liu, Gaisheng; Bohling, G.C.; Butler, J.J., Jr.

    2008-01-01

    [1] The direct-push permeameter (DPP) is a tool for the in situ characterization of hydraulic conductivity (K) in shallow, unconsolidated formations. This device, which consists of a short screened section with a pair of pressure transducers near the screen, is advanced into the subsurface with direct-push technology. K is determined through a series of injection tests conducted between advancements. Recent field work by Butler et al. (2007) has shown that the DPP holds great potential for describing vertical variations in K at an unprecedented level of detail, accuracy and speed. In this paper, the fundamental efficacy of the DPP is evaluated through a series of numerical simulations. These simulations demonstrate that the DPP can provide accurate K information under conditions commonly faced in the field. A single DPP test provides an effective K for the domain immediately surrounding the interval between the injection screen and the most distant pressure transducer. Features that are thinner than that interval can be quantified by reducing the vertical distance between successive tests and analyzing the data from all tests simultaneously. A particular advantage of the DPP is that, unlike most other single borehole techniques, a low-K skin or a clogged screen has a minimal impact on the K estimate. In addition, the requirement that only steady-shape conditions be attained allows for a dramatic reduction in the time required for each injection test. Copyright 2008 by the American Geophysical Union.

  20. Thermal and Hydraulic Analysis of the ITER Upper Vertical Stabilization Coil

    NASA Astrophysics Data System (ADS)

    Yang, Hong; Song, Yuntao; Wang, Zhongwei

    2014-07-01

    The ITER upper vertical stabilization (VS) coil is a part of the ITER in-vessel coil (IVC) system, which has the abilities of restraining edge localized modes (ELMs) and maintaining plasma vertical stability. Preliminary structural analysis of the coil has revealed serious thermal stress problems. Due to the very restricted geometry space, it is necessary to perform detailed analysis on thermal and hydraulic characteristics to help optimal design of the coil. It will focus on the temperature distribution and energy balance, as well as some key factors, such as the coolant flow state and surface emissivity, which have influences on the coil performance. The APDL code and some hand calculations are employed in the analysis. The results show that the coolant convection can effectively take away the heat deposited in the coil. But improving the coolant flow state can hardly mitigate the peak temperature occurring at the edges of coil attachments, which are located far away from the coolant. Thermal radiation was expected to be a good method of cooling down these parts. But the reality is not so optimistic since it usually contributes little in the whole energy balance. However, the effect of thermal radiation will become remarkable when bad scenarios or accidents take place. Poor radiation performance of the coil will result in a potential safety hazard.

  1. Adhesive Approach Using Internal Coping for Vertical Root Fractured Teeth with Flared Root Canals.

    PubMed

    Takeuchi, Shuhei; Sekita, Toshiaki; Kobayashi, Ken'ichi

    2015-01-01

    Vertical root fractures are often observed in teeth with endodontic treatment and post space preparation. Frequently, because such teeth have flared root canals with thin dentin walls, conventional treatments are disadvantageous in terms of adhesiveness, sealability and risk of refracture. Here we devised an intentional replantation method that uses internal resin coping, with a reinforcing effect on thin root canal dentin. In two patients treated with this method, satisfactory conditions have been maintained. This report suggests that an intentional replantation method in which an internal resin coping is employed may be a useful therapy for fractured teeth with flared root canals. PMID:26373031

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

    SciTech Connect

    Vreeburg, R.J.; Roodhart, L.P.; Davies, D.R.; Penny, G.S. )

    1994-10-01

    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.

  3. Characterization of hydraulic fracturing flowback water in Colorado: implications for water treatment.

    PubMed

    Lester, Yaal; Ferrer, Imma; Thurman, E Michael; Sitterley, Kurban A; Korak, Julie A; Aiken, George; Linden, Karl G

    2015-04-15

    A suite of analytical tools was applied to thoroughly analyze the chemical composition of an oil/gas well flowback water from the Denver-Julesburg (DJ) basin in Colorado, and the water quality data was translated to propose effective treatment solutions tailored to specific reuse goals. Analysis included bulk quality parameters, trace organic and inorganic constituents, and organic matter characterization. The flowback sample contained salts (TDS=22,500 mg/L), metals (e.g., iron at 81.4 mg/L) and high concentration of dissolved organic matter (DOC=590 mgC/L). The organic matter comprised fracturing fluid additives such as surfactants (e.g., linear alkyl ethoxylates) and high levels of acetic acid (an additives' degradation product), indicating the anthropogenic impact on this wastewater. Based on the water quality results and preliminary treatability tests, the removal of suspended solids and iron by aeration/precipitation (and/or filtration) followed by disinfection was identified as appropriate for flowback recycling in future fracturing operations. In addition to these treatments, a biological treatment (to remove dissolved organic matter) followed by reverse osmosis desalination was determined to be necessary to attain water quality standards appropriate for other water reuse options (e.g., crop irrigation). The study provides a framework for evaluating site-specific hydraulic fracturing wastewaters, proposing a suite of analytical methods for characterization, and a process for guiding the choice of a tailored treatment approach. PMID:25658325

  4. 4/6/2014 EU Drafts Hydraulic Fracturing Guidelines to Mitigate Conflicting Laws | The DailyEnergyReport http://www.dailyenergyreport.com/eu-drafts-hydraulic-fracturing-guidelines-to-mitigate-conflicting-laws-2/ 1/7

    E-print Network

    Chiao, Jung-Chih

    /eu-drafts-hydraulic-fracturing-guidelines-to-mitigate-conflicting-laws-2/ 2/7 Boeing Looking to Add Diesel From Vegetable Oils to Flights Boeing Co., the largest from vegetable oils to reduce fossil fuel consumption and curb carbon emissions. The "green" diesel the Chicago-based airplane maker. Libya's Oil Expansion Aids Refiners The first expansion in Libya's oil

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

    USGS Publications Warehouse

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

    1985-01-01

    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

  6. Estimation of deformation and stiffness of fractures close to tunnels using data from single-hole hydraulic testing and grouting

    SciTech Connect

    Fransson, A.; Tsang, C.-F.; Rutqvist, J.; Gustafson, G.

    2010-05-01

    Sealing of tunnels in fractured rocks is commonly performed by pre- or post-excavation grouting. The grouting boreholes are frequently drilled close to the tunnel wall, an area where rock stresses can be low and fractures can more easily open up during grout pressurization. In this paper we suggest that data from hydraulic testing and grouting can be used to identify grout-induced fracture opening, to estimate fracture stiffness of such fractures, and to evaluate its impact on the grout performance. A conceptual model and a method are presented for estimating fracture stiffness. The method is demonstrated using grouting data from four pre-excavation grouting boreholes at a shallow tunnel (50 m) in Nygard, Sweden, and two post-excavation grouting boreholes at a deep tunnel (450 m) in Aespoe HRL, Sweden. The estimated stiffness of intersecting fractures for the boreholes at the shallow Nygard tunnel are low (2-5 GPa/m) and in agreement with literature data from field experiments at other fractured rock sites. Higher stiffness was obtained for the deeper tunnel boreholes at Aespoe which is reasonable considering that generally higher rock stresses are expected at greater depths. Our method of identifying and evaluating the properties and impact of deforming fractures might be most applicable when grouting takes place in boreholes adjacent to the tunnel wall, where local stresses might be low and where deforming (opening) fractures may take most of the grout.

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

    EPA Science Inventory

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

  8. A Critical Review of the Risks to Water Resources from Unconventional Shale Gas Development and Hydraulic Fracturing in

    E-print Network

    Jackson, Robert B.

    A Critical Review of the Risks to Water Resources from Unconventional Shale Gas Development: The rapid rise of shale gas development through horizontal drilling and high volume hydraulic fracturing has expanded the extraction of hydrocarbon resources in the U.S. The rise of shale gas development has

  9. Regional air quality impacts of hydraulic fracturing and shale natural gas activity: Evidence from ambient VOC observations

    E-print Network

    Dickerson, Russell R.

    Regional air quality impacts of hydraulic fracturing and shale natural gas activity: Evidence from/Washington area. Shale natural gas operation emissions appear to be transported downwind. a r t i c l e i n f o to free and extract natural gas trapped within shale layers (USGS, 2014). According to the U.S. Energy

  10. Assessment of the Potential Impacts of Hydraulic Fracturing for Oil and Gas on Drinking Water Resources (External Review Draft)

    EPA Science Inventory

    Cover of the external review draft of the <span class=hydraulic fracturing drinking water research report"> This assessment provides a review and synthesi...

  11. 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...

  12. New treatment option for an incomplete vertical root fracture–a preliminary case report

    PubMed Central

    2014-01-01

    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. PMID:24670232

  13. Aligned vertical fractures, HTI reservoir symmetry, and Thomsenseismic anisotropy parameters for polar media

    SciTech Connect

    Berryman, James G.

    2007-12-12

    Sayers and Kachanov (1991) defined crack-influence parameters that are shown to be directly related to Thomsen (1986) weak-anisotropy seismic parameters for fractured reservoirs when the crack/fracture density is small enough. These results are then applied to the problem of seismic wave propagation in polar (i.e., non-isotropic) reservoirs having HTI seismic wave symmetry due to the presence of aligned vertical fractures and resulting in azimuthal seismic wave symmetry at the earth's surface. The approach presented suggests one method of inverting for fracture density from wave-speed data. It is also observed that the angular location {theta}{sub ex} of the extreme value (peak or trough) of the quasi-SV-wave speed for VTI occurs at an angle determined approximately by the formula tan{sup 2} {theta}{sub ex} {approx_equal} tan {theta}{sub m} = [(c{sub 33} - c{sub 44})/(c{sub 11}-c{sub 44})]{sup 1/2}, where {theta}{sub m} is an angle determined directly (as shown) from the c{sub ij} elastic stiffnesses, whenever these are known from either quasi-static or seismic wave measurements. Alternatively, {theta}{sub ex} is given in terms of the Thomsen seismic anisotropy parameters by tan {theta}{sub ex} {approx_equal} ([v{sub p}{sup 2}(0)-v{sub s}{sup 2}(0)]/[(1 + 2{epsilon})v{sub p}{sup 2}(0)-v{sub s}{sup 2}(0)]){sup 1/4}, where {epsilon} = (c{sub 11}-c{sub 33})/2c{sub 33}, v{sub p}{sup 2}(0) = c{sub 33}/{rho}, and v{sub s}{sup 2}(0) = c{sub 44}/{rho}, with {rho} being the background inertial mass density. The axis of symmetry is always treated here as the x{sub 3}-axis for either VTI symmetry (due, for example, to horizontal cracks), or HTI symmetry (due to aligned vertical cracks). Then the meaning of the stiffnesses is derived from the fracture analysis in the same way for VTI and HTI media, but for HTI the wave speeds relative to the earth's surface are shifted by 90{sup o} in the plane perpendicular to the aligned vertical fractures. Skempton's (1954) coefficient is used as a general means of quantifying the effects of fluids inside the fractures. Explicit formulas for Thomsen's parameters are also obtained for either drained or undrained fractures resulting in either VTI or HTI symmetry of the reservoir.

  14. Hydraulics.

    ERIC Educational Resources Information Center

    Decker, Robert L.

    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,…

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

    PubMed

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

    2013-01-01

    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

  16. Detection of water contamination from hydraulic fracturing wastewater: a ?PAD for bromide analysis in natural waters.

    PubMed

    Loh, Leslie J; Bandara, Gayan C; Weber, Genevieve L; Remcho, Vincent T

    2015-08-21

    Due to the rapid expansion in hydraulic fracturing (fracking), there is a need for robust, portable and specific water analysis techniques. Early detection of contamination is crucial for the prevention of lasting environmental damage. Bromide can potentially function as an early indicator of water contamination by fracking waste, because there is a high concentration of bromide ions in fracking wastewaters. To facilitate this, a microfluidic paper-based analytical device (?PAD) has been developed and optimized for the quantitative colorimetric detection of bromide in water using a smartphone. A paper microfluidic platform offers the advantages of inexpensive fabrication, elimination of unstable wet reagents, portability and high adaptability for widespread distribution. These features make this assay an attractive option for a new field test for on-site determination of bromide. PMID:26161586

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

    SciTech Connect

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

    1992-07-01

    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].

  18. Self-Similar Solutions for a Fractional Thin Film Equation Governing Hydraulic Fractures

    NASA Astrophysics Data System (ADS)

    Imbert, C.; Mellet, A.

    2015-12-01

    In this paper, self-similar solutions for a fractional thin film equation governing hydraulic fractures are constructed. One of the boundary conditions, which accounts for the energy required to break the rock, involves the toughness coefficient K ? 0. Mathematically, this condition plays the same role as the contact angle condition in the thin film equation. We consider two situations: The zero toughness ( K = 0) and the finite toughness K ? (0, ?) cases. In the first case, we prove the existence of self-similar solutions with constant mass. In the second case, we prove that for all K > 0 there exists an injection rate for the fluid such that self-similar solutions exist.

  19. Dynamics of Model Hydraulic Fracturing Liquid Studied by Two-Dimensional Infrared Spectroscopy

    NASA Astrophysics Data System (ADS)

    Daley, Kim; Kubarych, Kevin J.

    2014-06-01

    The technique of two-dimensional infrared (2DIR) spectroscopy is used to expose the chemical dynamics of various concentrations of polymers and their monomers in heterogeneous mixtures. An environmentally relevant heterogeneous mixture, which inspires this study, is hydraulic fracturing liquid (HFL). Hydraulic fracking is a technique used to extract natural gas from shale deposits. HFL consists of mostly water, proppant (sand), an emulsifier (guar), and other chemicals specific to the drilling site. Utilizing a metal carbonyl as a probe, we observe the spectral dynamics of the polymer, guar, and its monomer, mannose, and compare the results to see how hydration dynamics change with varying concentration. Another polymer, Ficoll, and its monomer, sucrose, are also compared to see how polymer size affects hydration dynamics. The two results are as follows: (1) Guar experiences collective hydration at high concentrations, where as mannose experiences independent hydration; (2) no collective hydration is observed for Ficoll in the same concentration range as guar, possibly due to polymer shape and size. HFL experiences extremely high pressure during natural gas removal, so future studies will focus on how increased pressure affects the hydration dynamics of polymers and monomers.

  20. Trace Hydrophobic Organic Chemicals Present in Pennsylvania Groundwater are Correlated with Geogenic Brines rather than Hydraulic Fracturing Active Zones

    NASA Astrophysics Data System (ADS)

    Drollette, B.; Shregglman, K.; D'Ambro, E.; Elsner, M.; Warner, N. R.; O'Connor, M.; Karatum, O.; Vengosh, A.; Jackson, R. B.; Darrah, T.; Plata, D.

    2014-12-01

    Recent studies demonstrated that deep Marcellus shale brines migrate into shallow groundwater aquifers, presumably via fractures in the subsurface that exist independent of any gas extraction activities. However, whereas many inorganic species are conservative tracers, hydrophobic organic compounds are both sorptive and reactive, and geogenic organic chemicals may not survive transport from deep shales to the subsurface. Here, 40 shallow groundwater samples from private wells in Northeastern Pennsylvania were analyzed for volatile organic compounds (VOCs) and gasoline range organic compounds (GRO), and 17 were analyzed for VOCs, GRO, and diesel range organic compounds (DRO). BTEX compounds (i.e., benzene, toluene, ethylbenzene, and xylenes) were detected in 6 of 40 samples at concentrations orders of magnitude below EPA maximum contaminant levels (e.g., << 5 ppb) and did not spatially correlate with distance to the nearest active hydraulic fracturing well. GRO was detected in 10 of 40 samples at concentrations as high as 8.8 ± 0.4 ppb and did not correlate with distance to the nearest hydraulic fracturing well (p = 0.24) nor in active fracturing zones, which we defined as sample locations less than 1 km from a well (p = 0.60). However, GRO was strongly correlated (p = 0.004) with shallow groundwater with Marcellus Shale inorganic chemical character, as delineated by inorganic chemical analysis. DRO was detected in all 17 samples up to 158 ± 4 ppb and did not spatially correlate with distance to the nearest hydraulic fracturing well (p = 0.74), nor active zones (p = 0.61). Similar to GRO, DRO did correlate with shallow groundwater containing Marcellus Shale character with moderate significance (p = 0.08). These results indicate that: (a) hydrophobic organic chemicals can survive transport from the deep subsurface to shallow groundwaters, and (b) transport of these compounds is not detectably enhanced by hydraulic fracturing activities in Northeastern PA as of the 2012-2014 summers.

  1. Biomechanical Study Using the Finite Element Method of Internal Fixation in Pauwels Type III Vertical Femoral Neck Fractures

    PubMed Central

    Noda, Mitsuaki; Saegusa, Yasuhiro; Takahashi, Masayasu; Tezuka, Daichi; Adachi, Kazuhiko; Naoi, Kazuya

    2015-01-01

    Background: Several factors are known to influence osseous union of femoral neck fractures. Numerous clinical studies have reported different results, hence with different recommendations regarding treatment of Pauwels III fractures: femoral neck fractures with a more vertically oriented fracture line. The current study aimed to analyze biomechanically whether this fracture poses a higher risk of nonunion. Objectives: To analyze the influence of one designated factor, authors believe that a computerized fracture model, using a finite element Finite Element Method (FEM), may be essential to negate the influence of other factors. The current study aimed to investigate a single factor, i.e. orientation of the fracture line toward a horizontal line, represented by Pauwels classification. It was hypothesized that a model with a vertically oriented fracture line maintaining parity of all other related factors has a higher stress at the fracture site, which would delay fracture healing. This result can be applicable to other types of pinning. Patients and Methods: The finite element models were constructed from computed tomography data of the femur. Three fracture models, treated with pinning, were constructed based on Pauwels classification: Type I, 30° between the fracture line and a horizontal line; Type II, 50°; and Type III, 70°. All other factors were matched between the models. The Von Mises stress and principal stress distribution were examined along with the fracture line in each model. Results: The peak Von Mises stresses at the medial femoral neck of the fracture site were 35, 50 and 130 MPa in Pauwels type I, II, and III fractures, respectively. Additionally, the peak Von Mises stresses along with the fracture site at the lateral femoral neck were 140, 16, and 8 MPa in Pauwels type I, II, and III fractures, respectively. The principal stress on the medial femoral neck in Pauwels type III fracture was identified as a traction stress, whereas the principal stress on the lateral femoral neck in Pauwels type I fracture was a compression stress. Conclusions: The most relevant finding was that hook pinning in Pauwels type III fracture may result in delayed union or nonunion due to significantly increased stress of a traction force at the fracture site that works to displace the fracture. However, in a Pauwels type I fracture, increased compression stress contributes to stabilize it. Surgeons are recommended not to treat Pauwels type III femoral neck fractures by pinning. PMID:26566507

  2. Effects of plant roots on the hydraulic performance during the clogging process in mesocosm vertical flow constructed wetlands.

    PubMed

    Hua, G F; Zhao, Z W; Kong, J; Guo, R; Zeng, Y T; Zhao, L F; Zhu, Q D

    2014-11-01

    The aim of this study was to evaluate the effects of plant roots (Typha angustifolia roots) on the hydraulic performance during the clogging process from the perspective of time and space distributions in mesocosm vertical flow-constructed wetlands with coarse sand matrix. For this purpose, a pair of lab-scale experiments was conducted to compare planted and unplanted systems by measuring the effective porosity and hydraulic conductivity of the substrate within different operation periods. Furthermore, the flow pattern of the clogging process in the planted and unplanted wetland systems were evaluated by their hydraulic performance (e.g., mean residence time, short circuiting, volumetric efficiency, number of continuously stirred tank reactors, and hydraulic efficiency factor) in salt tracer experiments. The results showed that the flow conditions would change in different clogging stages, which indicated that plants played different roles related to time and space. In the early clogging stages, plant roots restricted the flow of water, while in the middle and later clogging stages, especially the later stage, growing roots opened new pore spaces in the substrate. The roots played an important role in affecting the hydraulic performance in the upper layer (0-30 cm) where the sand matrix had a larger root volume fraction. Finally, the causes of the controversy over plant roots' effects on clogging were discussed. The results helped further understand the effects of plant roots on hydraulic performance during the clogging process. PMID:24994107

  3. Simulation-optimization model for water management in hydraulic fracturing operations

    NASA Astrophysics Data System (ADS)

    Hernandez, E. A.; Uddameri, V.

    2015-09-01

    A combined simulation-optimization model was developed to minimize the freshwater footprint at multi-well hydraulic fracturing sites. The model seeks to reduce freshwater use by blending it with brackish groundwater and recovered water. Time-varying water quality and quantity mass balance expressions and drawdown calculations using the Theis solution along with the superposition principle were embedded into the optimization model and solved using genetic algorithms. The model was parameterized for representative conditions in the Permian Basin oil and gas play region with the Dockum Formation serving as the brackish water source (Texas, USA). The results indicate that freshwater use can be reduced by 25-30 % by blending. Recovered water accounted for 2-3 % of the total blend or 10-15 % of total water recovered on-site. The concentration requirements of sulfate and magnesium limited blending. The evaporation in the frac pit constrained the amount blended during summer, while well yield of the brackish (Dockum) aquifer constrained the blending during winter. The Edwards-Trinity aquifer provided the best quality water compared to the Ogallala and Pecos Valley aquifers. However, the aquifer has low diffusivity causing the drawdown impacts to be felt over large areas. Speciation calculations carried out using PHREEQC indicated that precipitation of barium and strontium minerals is unlikely in the blended water. Conversely, the potential for precipitation of iron minerals is high. The developed simulation-optimization modeling framework is flexible and easily adapted for water management at other fracturing sites.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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.

  5. Expansion of decline curve parameters for tight gas sands with massive hydraulic fractures

    SciTech Connect

    Schaefer, T.

    1995-12-31

    With the advances in modern hydrocarbon technology and expansion of geologic settings for development, it is necessary to make changes to the conventional wisdoms that accompany production technology. This paper discusses some possible changes that necessitate implementation as observed both empirically and analytically. Specifically it discusses the time at which a decline curve can be implemented for production forecasting, the need for a dual decline model, and the severity of the decline variable that may be used for this model. It is the point of this paper to prove that for fight gas sands with massive hydraulic fractures that it is not only feasible to use decline variables that are greater than the traditional limit of harmonic or 1.0, but that the decline curve may also be implemented in the transient flow period of the well and decline both hyperbolically and exponentially. These ideas were not only proven through field study, but were additionally modeled with a fracture flow simulator. In order to prove these points this paper first introduces the Red Fork Formation and the development of an initial field model curve for this formation. After the initial model was developed, questions arose as to its feasibility. These questions were first addressed with a literature survey and further comparisons were made to test the models accuracy using pressure decline analysis and a fracture flow simulator. All of these methods were used to justify the implementation of a decline exponent as high as 2.1 for a hyperbolic curve during the early transient flow period, and regressing this hyperbolic into an exponential decline in the pseudo-steady state period.

  6. An application of Bayesian inverse methods to vertical deconvolution of hydraulic conductivity in a heterogeneous aquifer at Oak Ridge National Laboratory

    SciTech Connect

    Fienen, Michael; Kitanidis, Peter K.; Watson, David B; Jardine, Philip M

    2004-01-01

    A Bayesian inverse method is applied to two electromagnetic flowmeter tests conducted in fractured weathered shale at Oak Ridge National Laboratory. Traditional deconvolution of flowmeter tests is also performed using a deterministic first-difference approach; furthermore, ordinary kriging was applied on the first-difference results to provide an additional method yielding the best estimate and confidence intervals. Depth-averaged bulk hydraulic conductivity information was available from previous testing. The three methods deconvolute the vertical profile of lateral hydraulic conductivity. A linear generalized covariance function combined with a zoning approach was used to describe structure. Nonnegativity was enforced by using a power transformation. Data screening prior to calculations was critical to obtaining reasonable results, and the quantified uncertainty estimates obtained by the inverse method led to the discovery of questionable data at the end of the process. The best estimates obtained using the inverse method and kriging compared favorably with first-difference confirmatory calculations, and all three methods were consistent with the geology at the site.

  7. Potential Environmental Impact of Hydraulic Fracturing on Groundwater: Investigations of Coupled Flow, Geomechanics and Contaminant Transport (Invited)

    NASA Astrophysics Data System (ADS)

    Moridis, G. J.; Rutqvist, J.; Kim, J.; Reagan, M. T.; Freeman, C. M.

    2013-12-01

    Hydrocarbon production from tight reservoirs has recently experienced explosive growth. Gas production from shale and tight-sand deposits has proven remarkably successful in increasing substantially both gas production and reserves estimates in the U.S. The universal feature of all tight reservoirs is the need for stimulation: the matrix permeability is extremely low (often at the nano-Darcy level) and, even with the presence of natural fractures, it cannot support flow at commercially viable rates without permeability enhancement. Conventional stimulation techniques are usually variants of hydraulic fracturing, in which the near-incompressibility of injected liquids is exploited to deliver a shock that induces rock fracturing. The increased gas production resulting from hydraulic fracturing has been accompanied by controversy and environmental concerns. These stem from the possibility of creating fast permeability pathways between the shale and shallower formations, through which escaping hydrocarbons and other reservoir fluids could ascend and contaminate potable groundwater resources. Here we focus on two possible failure scenarios that can create pathways for upward migration of hydrocarbons and other contaminants: (a) the activation of sealed/dormant fractures and faults by the hydraulic fracturing operations, and (b) inadequate stimulation design, leading to fractures extending from the shale through the overburden to shallower groundwater resources. The study involves two components. In the first component, we use the coupled TOUGH+RealGasH2O and ROCMECH or FLAC3D codes to investigate the possibility of geomechanical failure, and the conditions under which this can occur. In the second component, we use the TOUGH+RealGasH2O code to investigate the flow and transport of gas from the shale to the aquifer through a plausible pathway regardless of the possibility, probability of likelihood of the corresponding geomechanical failure scenario. In Case (a), we show that, even after covering the spectrum of possible geomechanical parameter values, the possibility of fault activation is remote. In Case (b), we investigate various configurations of the system, and we conduct an extensive sensitivity analysis to determine its sensitivity to important geomechanical and hydraulic parameters and conditions, which determine its response to the hydraulic fracturing operations and the expected gas transport behavior through the fast pathways. These parameters and conditions include the physical separation of the shale from the aquifer, the porosity, permeability and wettability regimes of the matrix and of the matrix, the initial phase distributions, the relative pressure regime between the wells in the shale and the aquifer, the geomechanical strength of all the formations between the two end formations, the initial stress distributions and orientation, etc.

  8. Geological and petrological considerations relevant to the disposal of radioactive wastes by hydraulic fracturing: an example at the US Department of Energy's Oak Ridge National Laboratory

    SciTech Connect

    Haase, C.S.

    1983-01-01

    At Oak Ridge National Laboratory the Pumpkin Valley Shale is used as a host formation for hydraulic fracturing waste disposal. Determination of the relationships between the distribution of different lithologies and porosity-permeability trends within this host formation allows these properties, important to hydraulic fracturing operations, to be related to measurable and mappable geological and petrological parameters. It also permits extrapolation of such patterns to little-studied portions of the Pumpkin Valley Shale. Such knowledge better allows for the satisfactory operation and assessment of the hydraulic fracturing at Oak Ridge National Laboratory.

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

    USGS Publications Warehouse

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

    2006-01-01

    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.

  10. Hydraulic Inflation and Buoyancy Pumping: A Model for Large, Fracture-Mediated Felsic Intrusions

    NASA Astrophysics Data System (ADS)

    Clemens, J. D.; Ablay, G. J.; Grocott, J.; Petford, N.

    2005-05-01

    Large, intraplate, felsic intrusions with crustal anatectic sources, pipe-like conduits and tabular plutons are analysed, emphasising the magma-intrinsic factors that control their development. Conductively heated magma sources are broad and domical. Volume changes during melting generate buoyancy and hydraulic magmatic loads. The deformation state of the lithosphere determines its response. Rock strength depends on loading rate and limits differential stress. Tensile failure requires magma pore pressure, to reduce confining stress, while magma wedging in cracks modifies the stress field for vertical cracking. Non-magmatic loads include gravity and, critically, horizontal tensile stress from uplift, which favours vertical cracks. Tectonic forces are secondary. Intrusion begins with instability, due to the presence of magma and feedback between magmatic and ambient source loading. Hydrostatic magma pressure PM is augmented by buoyancy and melting dilativity overpressures (?PB and ?PV). ?PBmax increases with source height h while non-relaxed dilation creates ?PV (proportional to h3), which arises, instantaneously, to the wall-rock strength. ?PV confers high mechanical efficiency and increases faster than ?PB to a max. that is orders of magnitude greater. Inelastic uplift results but, since full inelastic relaxation of ?PV is impossible, elastic source compression results, providing hydraulic impetus for brittle source rupture and magma flow. For extensive melting, a molten cavity may develop. At lower melt fractions, melt veins form, connect and propagate as dykes. Magma pore overpressure and wedging fulfil the stress criteria for tensile rupture, whose geometry depends on the initial stress field (?H- or ?V-dominant). In domed crust, radial ruptures focus to form a wide, central, pipe-like conduit. Requirements for a viable conduit are; (i) ?V1; (ii) a positive gradient in PM, and; (iii) an aperture adequate to prevent magma freezing. If PM in dykes increases ?H to ?H1, then dykes re-orientate to sills, terminating ascent and initiating emplacement. Once stagnated, static ?PB is typically sufficient to force sill injection at depths less than a critical value D, where ?PB = ?V. Sills growth is dominated by floor depression. Underburden subsidence suppresses roof uplift, influences the sill's plan geometry, expels source magma, processes crust through the melting zone, decreases ?H in down-warped crust to favour conduit widening and magma ascent, and drains the source. Hydraulic inflation may end by melting cessation or exhaustion of excess magma volume EMV. Inelastic source swelling (?) or crack growth (?) relax EMV. Exhaustion of non-relaxed EMV (EMV*) divides intrusion into two regimes; hydraulic inflation and buoyancy pumping. Loss of hydraulic drive (EMV* = 0) occurs either during dyke or sill growth, depending on the initial EMV (source volume and melting dilativity). Once rupture occurs, disequilibrium cracking initiates, and ? increases abruptly as stored EMV* converts to crack volume. Equilibrium cracking begins once reduced EMV* balances new crack growth. If a sill is available to decouple shallow and deep crust, buoyancy pumping initiates, where underburden subsidence empties the magma source.

  11. Variations of streambed vertical hydraulic conductivity before and after a flood season

    NASA Astrophysics Data System (ADS)

    Wu, Guangdong; Shu, Longcang; Lu, Chengpeng; Chen, Xunhong; Zhang, Xiao; Appiah-Adjei, Emmanuel K.; Zhu, Jingsi

    2015-11-01

    The change of vertical hydraulic conductivity ( K v) before and after a flood season is crucial in understanding the long-term temporal variation of streambed permeability. Therefore, in this study, a detailed K v field investigation was conducted at an in-channel site within the Dawen River, China, before and after a flood season. In-situ falling-head permeameter tests were performed for the determination of K v. The tests were conducted using a 10 × 10 grid, at five different depths. In total, 871 valid K v values from layers 1-5 were obtained. The Kruskal-Wallis test on these K v values before and after the flood season shows they belonged to different populations. The sediments before the flood season primarily consisted of sand and gravel, whereas after the flood season, patchy distribution of silt/clay occurred in the sandy streambed and silt/clay content increased with the increasing depth; under the losing condition during flooding, downward movement of water brought fine particles into the coarse sediments, partially silting the pores. Accordingly, the K v values after the flood season had a smaller mean and median, and a higher level of heterogeneity, compared to those before the flood season. Additionally, the distribution pattern in K v across the stream differed before and after flood season; after the flood season, there was an increasing trend in K v from the south bank to the north bank. Overall, the contrasts of K v before and after the flood season were predominantly subject to the infiltration of fine particles.

  12. Accumulation of radium in sediments from continued disposal of produced water and hydraulic fracturing flowback water

    NASA Astrophysics Data System (ADS)

    Warner, N. R.; Menio, E. C.; Landis, J. D.; Vengosh, A.; Lauer, N.; Harkness, J.; Kondash, A.

    2014-12-01

    Recent public interest in high volume slickwater hydraulic fracturing (HVHF) has drawn increased interest in wastewater management practices by the public, researchers, industry, and regulators. The management of wastes, including both fluids and solids, poses many engineering challenges, including elevated total dissolved solids and elevated activities of naturally occurring radioactive materials (NORM). One management option for wastewater in particular, which is used in western Pennsylvania, USA, is treatment at centralized waste treatment facilities [1]. Previous studies conducted from 2010-2012 indicated that one centralized facility, the Josephine Brine Treatment facility, removed the majority of radium from produced water and hydraulic fracturing flowback fluid (HFFF) during treatment, but low activities of radium remained in treated effluent and were discharged to surface water [2]. Despite the treatment process and radium reduction, high activities (200 times higher than upstream/background) accumulated in stream sediments at the point of effluent discharge. Here we present new results from sampling conducted at two additional centralized waste treatment facilities (Franklin Brine Treatment and Hart Brine Treatment facilities) and Josephine Brine Treatment facility conducted in June 2014. Preliminary results indicate radium is released to surface water at very low (<50 pCi/L) to non-detectable activities, however; radium continues to accumulate in sediments surrounding the area of effluent release. Combined, the data indicate that 1) radium continues to be released to surface water streams in western Pennsylvania despite oil and gas operators voluntary ban on treatment and disposal of HFFF in centralized waste treatment facilities, 2) radium accumulation in sediments occurred at multiple brine treatment facilities and is not isolated to a single accidental release of contaminants or a single facility. [1] Wilson, J. M. and J. M. VanBriesen (2012). "Oil and Gas Produced Water Management and Surface Drinking Water Sources in Pennsylvania." Environmental Practice 14(04): 288-300. [2] Warner, N. R., C. A. Christie, R. B. Jackson and A. Vengosh (2013). "Impacts of Shale Gas Wastewater Disposal on Water Quality in Western Pennsylvania." ES&T 47(20): 11849-11857.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  14. Polyelectrolyte Complex Nanoparticles for Protection and Delayed Release of Enzymes in Alkaline pH and at Elevated Temperature during Hydraulic Fracturing of Oil Wells

    E-print Network

    Barati Ghahfarokhi, Reza; Johnson, Stephen J.; McCool, Stan; Green, Don W.; Willhite, G. Paul; Liang, Jenn-Tai

    2012-01-01

    Polyethylenimine-dextran sulfate polyelectrolyte complexes (PEC) were used to entrap two enzymes used to degrade polymer gels following hydraulic fracturing of oil wells in order to obtain delayed release and to protect ...

  15. Development 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...

  16. Strontium isotopes test long-term zonal isolation of injected and Marcellus formation water after hydraulic fracturing.

    PubMed

    Kohl, Courtney A Kolesar; Capo, Rosemary C; Stewart, Brian W; Wall, Andrew J; Schroeder, Karl T; Hammack, Richard W; Guthrie, George D

    2014-08-19

    One concern regarding unconventional hydrocarbon production from organic-rich shale is that hydraulic fracture stimulation could create pathways that allow injected fluids and deep brines from the target formation or adjacent units to migrate upward into shallow drinking water aquifers. This study presents Sr isotope and geochemical data from a well-constrained site in Greene County, Pennsylvania, in which samples were collected before and after hydraulic fracturing of the Middle Devonian Marcellus Shale. Results spanning a 15-month period indicated no significant migration of Marcellus-derived fluids into Upper Devonian/Lower Mississippian units located 900-1200 m above the lateral Marcellus boreholes or into groundwater sampled at a spring near the site. Monitoring the Sr isotope ratio of water from legacy oil and gas wells or drinking water wells can provide a sensitive early warning of upward brine migration for many years after well stimulation. PMID:25024106

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

    PubMed Central

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

    2011-01-01

    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. PMID:21555547

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

    USGS Publications Warehouse

    Vecchioli, John

    1965-01-01

    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.

  19. Fluid-rock interactions in unconventional reservoirs during hydraulic fracturing: a geochemical investigation from the Powder River Basin, WY

    NASA Astrophysics Data System (ADS)

    Herz-Thyhsen, R.; Kaszuba, J. P.

    2014-12-01

    Widespread use of hydraulic fracturing to stimulate resource production from unconventional reservoirs necessitates the development of a fundamental understanding for this process. Our research focuses on a synthesis of three sets of data to better understand geochemical and mineralogic aspects of the process of hydraulic fracturing, including laboratory experiments, field data, and geochemical modeling. Experiments examine fluid-rock interaction using rock samples from the Niobrara and Frontier Formations, two unconventional reservoirs within the Powder River Basin of NE Wyoming. Experiments react reservoir rocks with a representative hydraulic fracturing fluid for 28 days at 115°C and 350 bars. Fresh water and common chemicals, including HCl and petroleum distillates, used in hydraulic fracturing comprise the experimental fluid. Mineral reaction to the acidic fluid (pH ~2.35) causes immediate buffering, bringing fluid pH to near-neutral conditions after ~6 hours. Al initially spikes in the first 6 hours by ~10X, but returns to lower concentrations within 12 hours. Fe, Ba, Co, Mn, Sb, and Cr follow similar trends. Contemporaneously, Sr, Mo, Li, W, V, and Rb increase dramatically and remain at elevated levels. Changes in trace element concentrations correlate with clay alteration, calcite dissolution, and feldspar dissolution observed within reacted rock samples. Fluid samples are compared to produced-water chemistry from active wells in the field, enhancing our understanding of geochemical reactions occurring at depth. Lastly, produced fluid chemistry from both field samples and experiments are tethered together using preliminary geochemical models. These models predict calcite and feldspar reaction as well as new clay formation. This research ties together a limited population of produced water data with reservoir mineralogy to enhance fundamental understanding of fluid-rock interactions in unconventional reservoirs.

  20. The influence of metallic posts in the detection of vertical root fractures using different imaging examinations

    PubMed Central

    Jakobson, S J M; Westphalen, V P D; Silva Neto, U X; Fariniuk, L F; Schroeder, A G D

    2014-01-01

    Objectives: To assess the influence of metallic posts in the detection of simulated vertical root fractures (VRFs) using the following imaging examinations: 2 cone beam CT (CBCT) systems [CBCT1: NewTom® 3G (QR Srl, Verona, Italy) and CBCT2: i-CAT Next Generation® (Imaging Sciences International, Hatfield, PA)] and film and digital radiographs. Additionally, the influence of the orientation of the fracture line in the detection of VRFs was evaluated. Methods: 100, human, single-rooted endodontically treated premolars were divided into 5 groups (Group 1: with posts and buccolingual VRFs, Group 2: with posts and mesiodistal VRFs, Group 3: without posts and with buccolingual VRFs, Group 4: without posts and with mesiodistal VRFs, and Group 5: with posts and without VRFs). The premolars were placed in human mandibles and imaged using the four examination modalities. The sensitivity and the specificity of each examination in the experimental groups were calculated. The data were analysed using Student's t-test. Results: The presence of metallic posts reduced the sensitivity of the CBCT1 system (p = 0.0244). Digital radiographs and the CBCT1 and CBCT2 systems had a higher sensitivity in detecting buccolingual fractures in teeth with posts, whereas film and digital radiographs had a higher sensitivity in detecting buccolingual fractures in teeth without posts (p < 0.05). The CBCT1 examination demonstrated the lowest specificity (p < 0.05). Conclusions: The presence of metallic posts did not influence the sensitivity of most of the examinations, excluding the CBCT1 system. The fracture line orientation may influence VRF detection. PMID:24191261

  1. The Impacts of Rock Composition and Properties on the Ability to Stimulate Production of Ultra-Low Permeability Oil and Gas Reservoirs Through Hydraulic Fracturing

    NASA Astrophysics Data System (ADS)

    Zoback, M. D.; Sone, H.; Kohli, A. H.; Heller, R. J.

    2014-12-01

    In this talk, we present the results of several research projects investigating how rock properties, natural fractures and the state of stress affect the success of hydraulic fracturing operations during stimulation of shale gas and tight oil reservoirs. First, through laboratory measurements on samples of the Barnett, Eagle Ford, Haynesville and Horn River shales, we discuss pore structure, adsorption and permeability as well as the importance of clay content on the viscoplastic behavior of shale formations. Second, we present several lines of evidence that indicates that the principal way in which hydraulic fracturing stimulates production from shale gas reservoirs is by inducing slow slip on pre-existing fractures and faults, which are not detected by conventional microseismic monitoring, Finally, we discuss how hydraulic fracturing can be optimized in response to variations of rock properties.

  2. A reactive transport modelling approach to assess the leaching potential of hydraulic fracturing fluids associated with coal seam gas extraction

    NASA Astrophysics Data System (ADS)

    Mallants, Dirk; Simunek, Jirka; Gerke, Kirill

    2015-04-01

    Coal Seam Gas production generates large volumes of "produced" water that may contain compounds originating from the use of hydraulic fracturing fluids. Such produced water also contains elevated concentrations of naturally occurring inorganic and organic compounds, and usually has a high salinity. Leaching of produced water from storage ponds may occur as a result of flooding or containment failure. Some produced water is used for irrigation of specific crops tolerant to elevated salt levels. These chemicals may potentially contaminate soil, shallow groundwater, and groundwater, as well as receiving surface waters. This paper presents an application of scenario modelling using the reactive transport model for variably-saturated media HP1 (coupled HYDRUS-1D and PHREEQC). We evaluate the fate of hydraulic fracturing chemicals and naturally occurring chemicals in soil as a result of unintentional release from storage ponds or when produced water from Coal Seam Gas operations is used in irrigation practices. We present a review of exposure pathways and relevant hydro-bio-geo-chemical processes, a collation of physico-chemical properties of organic/inorganic contaminants as input to a set of generic simulations of transport and attenuation in variably saturated soil profiles. We demonstrate the ability to model the coupled processes of flow and transport in soil of contaminants associated with hydraulic fracturing fluids and naturally occurring contaminants.

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

    PubMed

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

    2014-06-01

    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

  4. Using discriminant analysis to determine sources of salinity in shallow groundwater prior to hydraulic fracturing.

    PubMed

    Lautz, Laura K; Hoke, Gregory D; Lu, Zunli; Siegel, Donald I; Christian, Kayla; Kessler, John Daniel; Teale, Natalie G

    2014-08-19

    High-volume hydraulic fracturing (HVHF) gas-drilling operations in the Marcellus Play have raised environmental concerns, including the risk of groundwater contamination. Fingerprinting water impacted by gas-drilling operations is not trivial given other potential sources of contamination. We present a multivariate statistical modeling framework for developing a quantitative, geochemical fingerprinting tool to distinguish sources of high salinity in shallow groundwater. The model was developed using new geochemical data for 204 wells in New York State (NYS), which has a HVHF moratorium and published data for additional wells in NYS and several salinity sources (Appalachian Basin brines, road salt, septic effluent, and animal waste). The model incorporates a stochastic simulation to predict the geochemistry of high salinity (>20 mg/L Cl) groundwater impacted by different salinity sources and then employs linear discriminant analysis to classify samples from different populations. Model results indicate Appalachian Basin brines are the primary source of salinity in 35% of sampled NYS groundwater wells with >20 mg/L Cl. The model provides an effective means for differentiating groundwater impacted by basin brines versus other contaminants. Using this framework, similar discriminatory tools can be derived for other regions from background water quality data. PMID:25062431

  5. Ground gas monitoring: implications for hydraulic fracturing and CO2 storage.

    PubMed

    Teasdale, Christopher J; Hall, Jean A; Martin, John P; Manning, David A C

    2014-12-01

    Understanding the exchange of carbon dioxide (CO2) and methane (CH4) between the geosphere and atmosphere is essential for the management of anthropogenic emissions. Human activities such as carbon capture and storage and hydraulic fracturing ("fracking") affect the natural system and pose risks to future global warming and to human health and safety if not engineered to a high standard. In this paper an innovative approach of expressing ground gas compositions is presented, using data derived from regulatory monitoring of boreholes in the unsaturated zone at infrequent intervals (typically 3 months) with data from a high frequency monitoring instrument deployed over periods of weeks. Similar highly variable trends are observed for time scales ranging from decades to hourly for boreholes located close to sanitary landfill sites. Additionally, high frequency monitoring data confirm the effect of meteorological controls on ground gas emissions; the maximum observed CH4 and CO2 concentrations in a borehole monitored over two weeks were 40.1% v/v and 8.5% v/v respectively, but for 70% of the monitoring period only air was present. There is a clear weakness in current point monitoring strategies that may miss emission events and this needs to be considered along with obtaining baseline data prior to starting any engineering activity. PMID:25363162

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

    NASA Astrophysics Data System (ADS)

    Stute, M.; Garten, L.

    2013-12-01

    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.

  7. Temporal Trends in Freshwater Withdrawals for Hydraulic Fracturing in the Marcellus Shale

    NASA Astrophysics Data System (ADS)

    Barth-Naftilan, E.; Saiers, J. E.

    2014-12-01

    Development of the Marcellus Shale, the nation's largest shale gas producing formation, is estimated to use two to seven million gallons of water per well. Because Marcellus Shale wells are located in relatively water-rich areas, there has been less pressure in the region to recycle and reuse freshwater sourced from surface water streams for stimulating new wells. We review trends in actual freshwater withdrawals from surface water streams over time, and examine which regulations are most protective of flows intra- and inter-annually. Pass-by flow protective requirements appear to be most effective when set based on monthly flows, rather than annual flows, though not all regulatory agencies are using this protective mechanism. Total water use by industry in a shale play doesn't appear to follow trends of seasonal availability until three to five years after development begins in that play, and intensity of water use from surface water withdrawal sites appears to decrease over time. Trends in water use can be tied to a number of factors including changing gas prices and demand (number of wells hydraulically fractured), increasing length of laterals, increasing recycling rates, increasing industrial efficiency, and others.

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

    PubMed

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

    2014-02-18

    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

  9. Regional Air Quality Impacts of Hydraulic Fracturing and Natural Gas Activity: Evidence from Ambient VOC Observations

    NASA Astrophysics Data System (ADS)

    Vinciguerra, T.; Ehrman, S.; Yao, S.; Dadzie, J.; Chittams, A.; Dickerson, R. R.

    2014-12-01

    Over the past decade, many anthropogenic pollutants have been successfully reduced, providing improved air quality. However, a new influx of emissions associated with hydraulic fracturing and natural gas operations could be counteracting some of these benefits. Using hourly measurements from Photochemical Assessment Monitoring Stations (PAMS) in the Baltimore, MD and Washington, D.C. areas, we observed that following a period of decline, daytime ethane concentrations have increased significantly since 2010. This trend appears to be linked with the rapid natural gas production in upwind, neighboring states, especially Pennsylvania and West Virginia. Furthermore, ethane concentrations failed to display this trend at a PAMS site outside of Atlanta, GA, a region without widespread natural gas operations. Year-to-year changes in VOCs were further evaluated by using Positive Matrix Factorization (PMF) to perform source apportionment on hourly observations in Essex, MD from 2005-2013. This process takes ambient measurements and attributes them to sources such as biogenic, natural gas, industrial, gasoline, and vehicle exhaust by using tracer species as identifiers. Preliminary PMF results also indicate an increasing influence of natural gas sources for this area.

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

    PubMed

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

    2014-06-30

    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

  11. Dispersion analysis of passive surface-wave noise generated during hydraulic-fracturing operations

    NASA Astrophysics Data System (ADS)

    Forghani-Arani, Farnoush; Willis, Mark; Snieder, Roel; Haines, Seth S.; Behura, Jyoti; Batzle, Mike; Davidson, Michael

    2014-12-01

    Surface-wave dispersion analysis is useful for estimating near-surface shear-wave velocity models, designing receiver arrays, and suppressing surface waves. Here, we analyze whether passive seismic noise generated during hydraulic-fracturing operations can be used to extract surface-wave dispersion characteristics. Applying seismic interferometry to noise measurements, we extract surface waves by cross-correlating several minutes of passive records; this approach is distinct from previous studies that used hours or days of passive records for cross-correlation. For comparison, we also perform dispersion analysis for an active-source array that has some receivers in common with the passive array. The active and passive data show good agreement in the dispersive character of the fundamental-mode surface-waves. For the higher mode surface waves, however, active and passive data resolve the dispersive properties at different frequency ranges. To demonstrate an application of dispersion analysis, we invert the observed surface-wave dispersion characteristics to determine the near-surface, one-dimensional shear-wave velocity.

  12. Foulger, G.R., B.R. Julian and F.C. Monastero, Microearthquake characterisation of an artificially stimulated hydraulic fracture at the Coso geothermal area, California, EOS Trans. AGU, Fall Meet. Suppl., Abstract, 2006.

    E-print Network

    Foulger, G. R.

    stimulated hydraulic fracture at the Coso geothermal area, California, EOS Trans. AGU, Fall Meet. Suppl., Abstract, 2006. Microearthquake characterisation of an artificially stimulated hydraulic fracture it by injecting fluids under pressure. Instead, natural fractures were encountered at about 2,660 m depth

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

    NASA Astrophysics Data System (ADS)

    Ortega Mercado, Camilo Ernesto

    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.

  14. A follow-up study on extracorporeal fixation of condylar fractures using vertical ramus osteotomy

    PubMed Central

    Park, Sung Yong; Im, Jae Hyoung; Yoon, Seong Hoe

    2014-01-01

    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. PMID:24868504

  15. Simulation assessment of the direct-push permeameter for characterizing vertical variations in hydraulic conductivity

    E-print Network

    Liu, Gaisheng; Bohling, Geoffrey C.; Butler, James J. Jr.

    2008-02-22

    [1] The direct-push permeameter (DPP) is a tool for the in situ characterization of hydraulic conductivity (K) in shallow, unconsolidated formations. This device, which consists of a short screened section with a pair of pressure transducers near...

  16. Analysis of the results of hydraulic-fracture stimulation of two crystalline bedrock boreholes, Grand Portage, Minnesota

    USGS Publications Warehouse

    Paillet, Fredrick L.; Olson, James D.

    1994-01-01

    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.

  17. EM Earthquake Precursor Detection Associated with Fluid Injection for Hydraulic Fracturing and Tectonic Sources

    NASA Astrophysics Data System (ADS)

    Jones, Kenneth B., II

    2015-04-01

    Many attempts have been made to determine an earthquake forecasting method and warn the public in turn. Presently, the animal kingdom leads the precursor list alluding to a transmission related source. By applying the animal-based model to an electromagnetic wave model, various hypotheses were formed, but only two seemed to take shape with the most interesting one requiring a magnetometer of a unique design. To date, numerous, high-end magnetometers have been in use in close proximity to fault zones for potential earthquake forecasting; however, results have had wide variability and problems still reside with what exactly is forecastable and the investigative direction of a true precursor. After a number of custom rock experiments, the two hypotheses were thoroughly tested to correlate the EM wave model. The first hypothesis involved sufficient and continuous electron movement either by surface or penetrative flow, and the second regarded a novel approach to radio wave generation. The second hypothesis resulted best with highly reproducible data, radio wave generation and detection, and worked numerous times with each laboratory test administered. In addition, internally introduced force on a small scale stressed a number of select rock types to emit radio waves well before catastrophic failure, and failure always went to completion. Comparatively, at a larger scale, highly detailed studies were procured to establish legitimate wave guides from potential hypocenters to epicenters and map the results, accordingly. Field testing in Southern California from 2006 to 2011 and outside the NE Texas town of Timpson in February, 2013 was conducted for detecting similar, laboratory generated, radio wave sources. At the Southern California field sites, signals were detected in numerous directions with varying amplitudes; therefore, a reactive approach was investigated in hopes of detecting possible aftershocks from large, tectonically related M5.0+ earthquakes. At the Timpson, Texas field sites, a proactive detection approach was taken, due to the heavy presence of hydraulic fracturing activity for regional hydrocarbon extraction, which appeared to be causing several rare M4.0+ earthquakes. As a result, detailed Southern California and Timpson, Texas field studies led to the improved design of two newer, prototype antennae and the first ever earthquake epicenter map. With more antennae and continuous monitoring, more fracture cycles can be established well ahead of the next earthquake. In addition, field data could be ascertained longer by the proper authorities and lead to significantly improved earthquake forecasting. The EM precursor determined by this method appears to surpass all prior precursor claims, and the general public may finally receive long overdue forecasting.

  18. The Functional Potential of Microbial Communities in Hydraulic Fracturing Source Water and Produced Water from Natural Gas Extraction Characterized by Metagenomic Sequencing

    PubMed Central

    Mohan, Arvind Murali; Bibby, Kyle J.; Lipus, Daniel; Hammack, Richard W.; Gregory, Kelvin B.

    2014-01-01

    Microbial activity in produced water from hydraulic fracturing operations can lead to undesired environmental impacts and increase gas production costs. However, the metabolic profile of these microbial communities is not well understood. Here, for the first time, we present results from a shotgun metagenome of microbial communities in both hydraulic fracturing source water and wastewater produced by hydraulic fracturing. Taxonomic analyses showed an increase in anaerobic/facultative anaerobic classes related to Clostridia, Gammaproteobacteria, Bacteroidia and Epsilonproteobacteria in produced water as compared to predominantly aerobic Alphaproteobacteria in the fracturing source water. The metabolic profile revealed a relative increase in genes responsible for carbohydrate metabolism, respiration, sporulation and dormancy, iron acquisition and metabolism, stress response and sulfur metabolism in the produced water samples. These results suggest that microbial communities in produced water have an increased genetic ability to handle stress, which has significant implications for produced water management, such as disinfection. PMID:25338024

  19. The functional potential of microbial communities in hydraulic fracturing source water and produced water from natural gas extraction characterized by metagenomic sequencing

    DOE PAGESBeta

    Mohan, Arvind Murali; Bibby, Kyle J.; Lipus, Daniel; Hammack, Richard W.; Gregory, Kelvin B.; Forster, Robert J.

    2014-10-22

    Microbial activity in produced water from hydraulic fracturing operations can lead to undesired environmental impacts and increase gas production costs. However, the metabolic profile of these microbial communities is not well understood. Here, for the first time, we present results from a shotgun metagenome of microbial communities in both hydraulic fracturing source water and wastewater produced by hydraulic fracturing. Taxonomic analyses showed an increase in anaerobic/facultative anaerobic classes related to Clostridia, Gammaproteobacteria, Bacteroidia and Epsilonproteobacteria in produced water as compared to predominantly aerobic Alphaproteobacteria in the fracturing source water. Thus, the metabolic profile revealed a relative increase in genes responsiblemore »for carbohydrate metabolism, respiration, sporulation and dormancy, iron acquisition and metabolism, stress response and sulfur metabolism in the produced water samples. These results suggest that microbial communities in produced water have an increased genetic ability to handle stress, which has significant implications for produced water management, such as disinfection.« less

  20. Comparison of water use for hydraulic fracturing for unconventional oil and gas versus conventional oil.

    PubMed

    Scanlon, B R; Reedy, R C; Nicot, J-P

    2014-10-21

    We compared water use for hydraulic fracturing (HF) for oil versus gas production within the Eagle Ford shale. We then compared HF water use for Eagle Ford oil with Bakken oil, both plays accounting for two-thirds of U.S. unconventional oil production in 2013. In the Eagle Ford, we found similar average water use in oil and gas zones per well (4.7-4.9 × 10(6) gallons [gal]/well). However, about twice as much water is used per unit of energy (water-to-oil ratio, WOR, vol water/vol oil) in the oil zone (WOR: 1.4) as in the gas zone (water-to-oil-equivalent-ratio, WOER: 0.6). We also found large differences in water use for oil between the two plays, with mean Bakken water use/well (2.0 × 10(6) gal/well) about half that in the Eagle Ford, and a third per energy unit. We attribute these variations mostly to geological differences. Water-to-oil ratios for these plays (0.6-1.4) will further decrease (0.2-0.4) based on estimated ultimate oil recovery of wells. These unconventional water-to-oil ratios (0.2-1.4) are within the lower range of those for U.S. conventional oil production (WOR: 0.1-5). Therefore, the U.S. is using more water because HF has expanded oil production, not because HF is using more water per unit of oil production. PMID:25233450

  1. Modeling Atmospheric Emissions and Calculating Mortality Rates Associated with High Volume Hydraulic Fracturing Transportation

    NASA Astrophysics Data System (ADS)

    Mathews, Alyssa

    Emissions from the combustion of fossil fuels are a growing pollution concern throughout the global community, as they have been linked to numerous health issues. The freight transportation sector is a large source of these emissions and is expected to continue growing as globalization persists. Within the US, the expanding development of the natural gas industry is helping to support many industries and leading to increased transportation. The process of High Volume Hydraulic Fracturing (HVHF) is one of the newer advanced extraction techniques that is increasing natural gas and oil reserves dramatically within the US, however the technique is very resource intensive. HVHF requires large volumes of water and sand per well, which is primarily transported by trucks in rural areas. Trucks are also used to transport waste away from HVHF well sites. This study focused on the emissions generated from the transportation of HVHF materials to remote well sites, dispersion, and subsequent health impacts. The Geospatial Intermodal Freight Transport (GIFT) model was used in this analysis within ArcGIS to identify roadways with high volume traffic and emissions. High traffic road segments were used as emissions sources to determine the atmospheric dispersion of particulate matter using AERMOD, an EPA model that calculates geographic dispersion and concentrations of pollutants. Output from AERMOD was overlaid with census data to determine which communities may be impacted by increased emissions from HVHF transport. The anticipated number of mortalities within the impacted communities was calculated, and mortality rates from these additional emissions were computed to be 1 in 10 million people for a simulated truck fleet meeting stricter 2007 emission standards, representing a best case scenario. Mortality rates due to increased truck emissions from average, in-use vehicles, which represent a mixed age truck fleet, are expected to be higher (1 death per 341,000 people annually).

  2. Will water scarcity in semiarid regions limit hydraulic fracturing of shale plays?

    NASA Astrophysics Data System (ADS)

    Scanlon, Bridget R.; Reedy, Robert C.; Nicot, Jean Philippe

    2014-12-01

    There is increasing concern about water constraints limiting oil and gas production using hydraulic fracturing (HF) in shale plays, particularly in semiarid regions and during droughts. Here we evaluate HF vulnerability by comparing HF water demand with supply in the semiarid Texas Eagle Ford play, the largest shale oil producer globally. Current HF water demand (18 billion gallons, bgal; 68 billion liters, bL in 2013) equates to ˜16% of total water consumption in the play area. Projected HF water demand of ˜330 bgal with ˜62 000 additional wells over the next 20 years equates to ˜10% of historic groundwater depletion from regional irrigation. Estimated potential freshwater supplies include ˜1000 bgal over 20 yr from recharge and ˜10 000 bgal from aquifer storage, with land-owner lease agreements often stipulating purchase of freshwater. However, pumpage has resulted in excessive drawdown locally with estimated declines of ˜100-200 ft in ˜6% of the western play area since HF began in 2009-2013. Non-freshwater sources include initial flowback water, which is ?5% of HF water demand, limiting reuse/recycling. Operators report shifting to brackish groundwater with estimated groundwater storage of 80 000 bgal. Comparison with other semiarid plays indicates increasing brackish groundwater and produced water use in the Permian Basin and large surface water inputs from the Missouri River in the Bakken play. The variety of water sources in semiarid regions, with projected HF water demand representing ˜3% of fresh and ˜1% of brackish water storage in the Eagle Ford footprint indicates that, with appropriate management, water availability should not physically limit future shale energy production.

  3. Enhancing Seismic Monitoring Capability for Hydraulic Fracturing Induced Seismicity in Canada

    NASA Astrophysics Data System (ADS)

    Kao, H.; Cassidy, J. F.; Farahbod, A.; Lamontagne, M.

    2012-12-01

    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.

  4. Active monitoring of hydraulic and mechanical properties variations during the hydraulic stimulation of a fractured porous reservoir: Some preliminary results from the HPPP Project

    NASA Astrophysics Data System (ADS)

    Cappa, F.; Guglielmi, Y.

    2010-12-01

    A new protocol of active geophysical monitoring is used to investigate the downhole changes in the hydromechanical response of a naturally porous reservoir layer with 80° dipping fractures where permeability was artificially enhanced by a hydraulic jacking test conducted by a step-wise increase of the fluid pressure. The protocol, called the High-Pulse Poroelasticity Protocol (HPPP) (http://hppp.unice.fr/), is focusing on controlled-impulsive source repeated observations and interpretation of rock properties changes over the seismic band of frequencies. The excitation source corresponds to a fast hydraulic pulse imposed in a small section of a borehole. The source is monitored with a special borehole probe based on fiber-optic sensors which allow dynamic fluid pressure/3D-mechanical deformation measurements, with reflection of light at specific wavelength from Fabry-Pérot or fiber Bragg gratings mounted between inflatable packers. Within the injection zone, fluid pressure and deformation waves of 1 to 500 Hz and static hydraulic diffusion are simultaneously measured to quantify the hydromechanical couplings Two identical pressure pulses were performed to test the rock three-dimensionnal mechanical response before and after the jacking test. It clearly appears that (1) the magnitude of the rock deformation is a factor of 3 higher, and (2) the principal deformation component pitch is rotated of about 20° with more radial deformation of the layer after the jacking test. Those preliminary tests show that the HPPP protocol can actively improve downhole monitoring of both hydraulic and mechanical bulk properties changes of rocks under strong dynamic stress-flow couplings.

  5. Physics-based Modeling of Rock Deformation and Fracturing Induced by Hydraulic Stimulation of Enhanced Geothermal System Reservoirs (Invited)

    NASA Astrophysics Data System (ADS)

    Huang, H.; Podgorney, R. K.; Deng, S.

    2010-12-01

    A key assumption associated with enhanced geothermal system reservoir creation/stimulation is that sufficient rock volumes can be hydraulically fractured via both tensile and shear failure, and more importantly by reactivation of naturally existing fractures (by shearing) to create the reservoir. The advancement of enhanced geothermal system greatly depends on our understanding of the dynamics of the intimately coupled rock-fracture-fluid system and our ability to reliably predict how reservoirs behave under stimulation and production. In order to increase our understanding of how reservoirs behave under these conditions, we have developed a physics-based rock deformation and fracture propagation simulator by coupling a discrete element model (DEM) for fracturing with a continuum multiphase flow and heat transport model. In DEM simulations, 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/or internal load is applied. DEM models have been applied to a very wide range of fracturing processes from the molecular scale (where thermal fluctuations play an important role) to scales on the order of kilometers or greater. In this approach, the continuum flow and heat transport equations are solved on an underlying fixed finite element grid with evolving porosity and permeability for each grid cell that depends on the local structure of the discrete element network (such as DEM particle density). The fluid pressure gradient exerts forces on individual elements of the DEM network, which therefore deforms and fractures. Such deformation/fracturing in turn changes the permeability, which again changes the evolution of fluid pressure, coupling the two phenomena. The intimate coupling between fracturing and fluid flow makes the meso-scale DEM simulations necessary, as these methods have substantial advantages over conventional continuum mechanical models of elastic rock deformation. The challenges that must be overcome to simulate reservoir stimulation, preliminary results, progress to date and near future research directions and opportunities will be discussed.

  6. The Effect of Rock Properties on Hydraulic Fracture Conductivity in the Eagle Ford and Fayetteville Shales 

    E-print Network

    Jansen, Timothy A

    2014-09-05

    . Optimizing fracture designs to improve well performance requires knowledge of how fracture conductivity is affected by rock and proppant characteristics. This study investigates the relationship between rock characteristics and laboratory measurements...

  7. Sensitivity of time lapse seismic data to the compliance of hydraulic fractures

    E-print Network

    Fang, Xinding

    2013-01-01

    We study the sensitivity of seismic waves to changes in the fracture normal and tangential compliances by analyzing the fracture sensitivity wave equation, which is derived by differentiating the elastic wave equation with ...

  8. A critical review of the risks to water resources from unconventional shale gas development and hydraulic fracturing in the United States.

    PubMed

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

    2014-01-01

    The rapid rise of shale gas development through horizontal drilling and high volume hydraulic fracturing has expanded the extraction of hydrocarbon resources in the U.S. The rise of shale gas development has triggered an intense public debate regarding the potential environmental and human health effects from hydraulic fracturing. This paper provides a critical review of the potential risks that shale gas operations pose to water resources, with an emphasis on case studies mostly from the U.S. Four potential risks for water resources are identified: (1) the contamination of shallow aquifers with fugitive hydrocarbon gases (i.e., stray gas contamination), which can also potentially lead to the salinization of shallow groundwater through leaking natural gas wells and subsurface flow; (2) the contamination of surface water and shallow groundwater from spills, leaks, and/or the disposal of inadequately treated shale gas wastewater; (3) the accumulation of toxic and radioactive elements in soil or stream sediments near disposal or spill sites; and (4) the overextraction of water resources for high-volume hydraulic fracturing that could induce water shortages or conflicts with other water users, particularly in water-scarce areas. Analysis of published data (through January 2014) reveals evidence for stray gas contamination, surface water impacts in areas of intensive shale gas development, and the accumulation of radium isotopes in some disposal and spill sites. The direct contamination of shallow groundwater from hydraulic fracturing fluids and deep formation waters by hydraulic fracturing itself, however, remains controversial. PMID:24606408

  9. Inferring Hydraulic and Fracture Properties of a Fracked Coal Seam Aquifer by Using GLUE Uncertainty Analysis using TOUGH2 reservoir simulator

    NASA Astrophysics Data System (ADS)

    Willgoose, G. R.; Askarimarnani, S. S.

    2014-12-01

    Coal seam gas (also called coal bed methane) is a form of natural gas that occurs in some coal seams. In the coal seam gas industry, hydraulic fracturing is performed to enhance the extraction of the gas from the coal seam. This paper presents flow simulation results for a fractured coal seam and its associate production well, and an investigation of the well piezometric head drawdown curves resulting from hydraulic pumping tests. The aim is to infer the hydraulic and fracture properties of the coal and associated well, such as length, width, conductivity of fractures, and the proportion of the water and gas contained in the coal seam. For this purpose the TOUGH2/EOS7C numerical simulator is applied. It is capable of modelling multiphase flow in fractured and porous system. The EOS7C is an "equation of state" module for TOUGH2 that is used to model the methane dissolved and free gas multiphase component. The Wingridder grid generator has been used to generate the 2D, 3D and MINCE (multiple interacting continua) grids for TOUGH2. The simulation results provide some constraints on hydraulic and fracture properties. However, there is still have significant uncertainty. In order to assess the uncertainty and increase our knowledge of the hydraulic properties, uncertainty analysis using the Generalized Likelihood Uncertainty Estimation (GLUE), which is a Monte-Carlo methodology, is applied. We will discuss how the Monte-Carlo uncertainty analyses is used to infer the properties of a hydraulically fractured well from pump test data. One major outcome of this work will be the development of a fast and routine method for assessing the post-development performance and safety of a production gas well, and to provide reassurance that the fracking that has actually occurred in the field is within design parameters.

  10. Determining sources of elevated salinity in pre-hydraulic fracturing water quality data using a multivariate discriminant analysis model

    NASA Astrophysics Data System (ADS)

    Lautz, L. K.; Hoke, G. D.; Lu, Z.; Siegel, D. I.

    2013-12-01

    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.

  11. Numerical Simulation of Subsurface Transport and Groundwater Impacts from Hydraulic Fracturing of Tight/Shale Gas Reservoirs

    NASA Astrophysics Data System (ADS)

    Reagan, M. T.; Moridis, G. J.; Keen, N. D.

    2014-12-01

    The use of reservoir stimulation techniques, such as hydraulic fracturing, has grown tremendously over the last decade, and concerns have arisen that reservoir stimulation creates environmental threats through the creation of permeable pathways that could connect the stimulated reservoir to shallower groundwater aquifers. This study investigates, by numerical simulation, gas and water transport between a deeper tight-gas reservoir and a shallower overlying groundwater aquifer following hydraulic fracturing operations, assuming that the formation of a connecting pathway has already occurred. We focus on two general transport scenarios: 1) communication between the reservoir and aquifer via a connecting fracture or fault and 2) communication via a deteriorated, preexisting nearby well. The simulations explore a range of permeabilities and geometries over time scales, and evaluate the mechanisms and factors that could lead to the escape of gas or reservoir fluid and the contamination of groundwater resources. We also examine the effects of overpressured reservoirs, and explore long-term transport processes as part of a continuing study. We conclude that the key factors driving short-term transport of gas include high permeability for the connecting pathway and the overall volume of the connecting feature. Gas production from the reservoir via a horizontal well is likely to mitigate release through the reduction of available free gas and the lowering of reservoir pressure. We also find that fractured tight-gas reservoirs are unlikely to act as a continuing source of large volumes of migrating gas, and incidents of gas escape are likely to be limited in duration and scope. Reliable field and laboratory data must be acquired to constrain the factors and determine the likelihood of these outcomes.

  12. Seismic monitoring of hydraulic fracturing: techniques for determining fluid flow paths and state of stress away from a wellbore

    SciTech Connect

    Fehler, M.; House, L.; Kaieda, H.

    1986-01-01

    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.

  13. Evaluating the Influence of Chemical Reactions on Wellbore Cement Integrity and Geochemical Tracer Behavior in Hydraulically-Fractured Shale Formations

    NASA Astrophysics Data System (ADS)

    Verba, C.; Lieuallen, A.; Yang, J.; Torres, M. E.; Hakala, A.

    2014-12-01

    Ensuring wellbore integrity for hydraulically-fractured shale reservoirs is important for maintaining zonal isolation of gases and fluids within the reservoir. Chemical reactions between wellbore cements, the shale formation, formation fluids, and fracturing fluids could affect the ability for cement to form an adequate seal. This study focuses on experimental investigations to evaluate how cement, rock, brines, and fracturing fluids react under conditions similar to the perforated zone associated with the Marcellus shale (Greene County, Pennsylvania). Two pressure/temperature regimes were investigated- moderate (25 MPa, 50oC) and high (27.5 MPa, 90oC). Shale collected from the Lower Marcellus section was encased in Class A cement, cured for 24 hours, and then exposed to simulated conditions in experimental autoclave reactors. The simulated formation fluid was a synthetic brine, modeled after a flowback fluid contained 187,000 mg/l total dissolved solids and had a pH of 7.6. The effect of pH was probed to evaluate the potential for cement reactivity under different pH conditions, and the potential for contaminant or geochemical tracer release from the shale (e.g. arsenic and rare earth elements). In addition to dissolution reactions, sorption and precipitation reactions between solutes and the cement are being evaluated, as the cement could bond with solute-phase species during continued hydration. The cements are expected to show different reactivity under the two temperature conditions because the primary cement hydration product, calcium silicate hydrate (C-S-H) is heavily influenced by temperature. Results from these experimental studies will be used both to inform the potential changes in cement chemistry that may occur along a wellbore in the hydraulically-fractured portion of a reservoir, and the types of geochemical tracers that may be useful in tracking these reactions.

  14. Can Horizontal Hydraulic Fracturing Lead to Less Expensive Achievement of More Natural River Flows?

    NASA Astrophysics Data System (ADS)

    Kern, J.; Characklis, G. W.

    2014-12-01

    High ramp rates and low costs make hydropower an extremely valuable resource for meeting "peak" hourly electricity demands, but dams that employ variable, stop-start reservoir releases can have adverse impacts on downstream riverine ecosystems. In recent years, efforts to mitigate the environmental impacts of hydropower peaking have relied predominantly on the use of ramp rate restrictions, or limits on the magnitude of hour-to-hour changes in reservoir discharge. These restrictions shift some hydropower production away from peak hours towards less valuable off-peak hours and impose a financial penalty on dam owners that is a function of: 1) the "spread" (difference) between peak and off-peak electricity prices; and 2) the total amount of generation shifted from peak to off-peak hours. In this study, we show how variability in both the price spread and reservoir inflows can cause large swings in the financial cost of ramp rate restrictions on a seasonal and annual basis. Of particular interest is determining whether current low natural gas prices (largely attributable to improvements in hydraulic fracturing) have reduced the cost of implementing ramp rate restrictions at dams by narrowing the spread between peak and off-peak electricity prices. We also examine the role that large year-to-year fluctuations in the cost of ramp rate restrictions may play in precluding downstream stakeholders (e.g., conservation trusts) from "purchasing" more natural streamflow patterns from dam owners. In recent years, similar arrangements between conservation trusts and consumptive water users have been put into practice in the U.S. for the purposes of supplementing baseflows in rivers. However, significant year-to-year uncertainty in the size of payments necessary to compensate hydropower producers for lost peaking production (i.e., uncertainty in the cost of ramp rate restrictions) makes transactions that aim to mitigate the environmental impacts of hydropower peaking untenable. In order to reduce this financial uncertainty, we propose the use of "collar" agreements between a downstream stakeholder and a third party insurer that would provide a stable price for parties "buying" more natural flows.

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

    PubMed

    Struchtemeyer, Christopher G; Elshahed, Mostafa S

    2012-07-01

    Hydraulic fracturing is used to increase the permeability of shale gas formations and involves pumping large volumes of fluids into these formations. A portion of the frac fluid remains in the formation after the fracturing process is complete, which could potentially contribute to deleterious microbially induced processes in natural gas wells. Here, we report on the geochemical and microbiological properties of frac and flowback waters from two newly drilled natural gas wells in the Barnett Shale in North Central Texas. Most probable number studies showed that biocide treatments did not kill all the bacteria in the fracturing fluids. Pyrosequencing-based 16S rRNA diversity analyses indicated that the microbial communities in the flowback waters were less diverse and completely distinct from the communities in frac waters. These differences in frac and flowback water communities appeared to reflect changes in the geochemistry of fracturing fluids that occurred during the frac process. The flowback communities also appeared well adapted to survive biocide treatments and the anoxic conditions and high temperatures encountered in the Barnett Shale. PMID:22066833

  16. Vertical migration of gas through fractures due to salinity-buffered hydrate formation within the hydrate stability zone

    NASA Astrophysics Data System (ADS)

    Meyer, D.; Flemings, P. B.

    2014-12-01

    Seafloor gas vents within the hydrate stability zone along continental margins are frequently associated with high saturations of gas hydrate that increase upwards towards the seafloor (e.g. NGHP 01 Site 10A, UBGH2 Site 3, ODP Site 1249A). One model for how gas migrates through the hydrate stability zone proposes that salt exclusion during hydrate formation elevates the in-situ salinity, which allows for the coexistence of gas, hydrate, and water. In some portions of these sites, however, the hydrate saturations derived from pressure cores are insufficient to elevate the bulk salinity enough to induce three-phase conditions. Commonly, hydrate in these zones exists in individual, high-angle fractures within mudstone. An alternative gas migration model, applicable to fractured regions, proposes that the fractures act as highly permeable gas conduits for upward fluid flow. We present a model to describe gas flow and hydrate formation in these fractures. Hydrate begins forming at the fracture wall, where the components (water and gas) are available. Water is continuously drawn from the mudstone to the fracture by capillary forces. Due to hydrate formation, salinity is elevated to three-phase conditions at the fracture wall. Simultaneously, salt diffuses away from the fracture into the bounding mudstone. At this point, hydrate formation is controlled by the chemical diffusion of salt away from and the advection of less-saline water towards the fracture wall. Hydrate formation is ultimately limited by either insufficient water flow to the hydrate front or elevation of the bulk salinity to three-phase conditions. We explore the timescale, nature, and limitation of hydrate formation in vertical fractures.

  17. Fracture hydraulic conductivity in the Mexico City clayey aquitard: Field piezometer rising-head tests

    NASA Astrophysics Data System (ADS)

    Vargas, Carlos; Ortega-Guerrero, Adrián

    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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  19. Contrasting groundwater quality in areas with and without gas production by hydraulic fracturing near the PA/NY border

    NASA Astrophysics Data System (ADS)

    Stute, M.; Yan, B.; Ross, J. M.; Chillrud, S. N.; Saberi, P.; Panettieri, R. A.

    2013-12-01

    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.

  20. The biomechanical role of periodontal ligament in bonded and replanted vertically fractured teeth under cyclic biting forces.

    PubMed

    Zhu, Ya-Nan; Yang, Wei-Dong; Abbott, Paul V; Martin, Nicolas; Wei, Wen-Jia; Li, Jing-Jing; Chen, Zhi; Wang, Wen-Mei

    2015-06-01

    After teeth are replanted, there are two possible healing responses: periodontal ligament healing or ankylosis with subsequent replacement resorption. The purpose of this study was to compare the fatigue resistance of vertically fractured teeth after bonding the fragments under conditions simulating both healing modes. Thirty-two human premolars were vertically fractured and the fragments were bonded together with Super-Bond C&B. They were then randomly distributed into four groups (BP, CP, CA, BA). The BP and CP groups were used to investigate the periodontal ligament healing mode whilst the BA and CA groups simulated ankylosis. All teeth had root canal treatment performed. Metal crowns were constructed for the CP and CA groups. The BP and BA groups only had composite resin restorations in the access cavities. All specimens were subjected to a 260 N load at 4 Hz until failure of the bond or until 2 × 10? cycles had been reached if no fracture occurred. Cracks were detected by stereomicroscope imaging and also assessed via dye penetration tests. Finally, interfaces of the resin luting agent were examined by scanning electron microscope. The results confirmed that the fatigue resistance was higher in the groups with simulated periodontal ligament healing. Periodontal reattachment showed important biomechanical role in bonded and replanted vertically fractured teeth. PMID:25214360

  1. Comparing the Effect of Different Voxel Resolutions for Assessment of Vertical Root Fracture of Permanent Teeth

    PubMed Central

    Uzun, Ismail; Gunduz, Kaan; Celenk, Peruze; Avsever, Hakan; Orhan, Kaan; Canitezer, Gozde; Ozmen, Bilal; Cicek, Ersan; Egrioglu, Erol

    2015-01-01

    Background: The teeth with undiagnosed vertical root fractures (VRFs) are likely to receive endodontic treatment or retreatment, leading to frustration and inappropriate endodontic therapies. Moreover, many cases of VRFs cannot be diagnosed definitively until the extraction of tooth. Objectives: This study aimed to assess the use of different voxel resolutions of two different cone beam computerized tomography (CBCT) units in the detection VRFs in vitro. Materials and Methods: The study material comprised 74 extracted human mandibular single rooted premolar teeth without root fractures that had not undergone any root-canal treatment. Images were obtained by two different CBCT units. Four image sets were obtained as follows: 1) 3D Accuitomo 170, 4 × 4 cm field of view (FOV) (0.080 mm3); 2) 3D Accuitomo 170. 6 × 6 cm FOV (0.125 mm3); 3) NewTom 3G, 6? (0.16 mm3) and 4) NewTom 3G, 9? FOV (0.25 mm3). Kappa coefficients were calculated to assess both intra- and inter-observer agreements for each image set. Results: No significant differences were found among observers or voxel sizes, with high average Z (Az) results being reported for all groups. Both intra- and inter-observer agreement values were relatively better for 3D Accuitomo 170 images than the images from NewTom 3G. The highest Az and kappa values were obtained with 3D Accuitomo 170, 4 × 4 cm FOV (0.080 mm3) images. Conclusion: No significant differences were found among observers or voxel sizes, with high Az results reported for all groups. PMID:26557279

  2. Hydraulic Fracture Optimization with a Pseudo-3D Model in Multi-layered Lithology 

    E-print Network

    Yang, Mei

    2011-10-21

    based on the so-called two-dimensional models (2D) focus on the optimization of fracture length and width, assuming one can estimate a value for fracture height, while so-called pseudo three dimensional (p-3D) models suitable for multi-layered reservoirs...

  3. This is the pre-peer reviewed version of the following article: "Can hydraulic fracturing make Poland self-sufficient in natural gas?", which will be published in final form in a

    E-print Network

    Patzek, Tadeusz W.

    The International Energy Agency (IEA) has highlighted hydraulic fracturing (fracking) as the key to a "Golden Age in the future. In order to improve energy security in the EU, hydraulic fracturing or "fracking," as it commonly is called, is now stated as a possibility. Fracking is discussed in a "Special Report on Unconventional Gas

  4. Vertical distribution of soil saturated hydraulic conductivity and its influencing factors in a small karst catchment in Southwest China.

    PubMed

    Fu, Tonggang; Chen, Hongsong; Zhang, Wei; Nie, Yunpeng; Wang, Kelin

    2015-03-01

    Saturated hydraulic conductivity (Ks) is one of the most important soil hydraulic parameters influencing hydrological processes. This paper aims to investigate the vertical distribution of Ks and to analyze its influencing factors in a small karst catchment in Southwest China. Ks was measured in 23 soil profiles for six soil horizons using a constant head method. These profiles were chosen in different topographical locations (upslope, downslope, and depression) and different land-use types (forestland, shrubland, shrub-grassland, and farmland). The influencing factors of Ks, including rock fragment content (RC), bulk density (BD), capillary porosity (CP), non-capillary porosity (NCP), and soil organic carbon (SOC), were analyzed by partial correlation analysis. The mean Ks value was higher in the entire profile in the upslope and downslope, but lower value, acting as a water-resisting layer, was found in the 10-20 cm soil depth in the depression. Higher mean Ks values were found in the soil profiles in the forestland, shrubland, and shrub-grassland, but lower in the farmland. These results indicated that saturation-excess runoff could occur primarily in the hillslopes but infiltration-excess runoff in the depression. Compared with other land-use types, surface runoff is more likely to occur in the farmlands. RC had higher correlation coefficients with Ks in all categories concerned except in the forestland and farmland with little or no rock fragments, indicating that RC was the dominant influencing factor of Ks. These results suggested that the vertical distributions of Ks and RC should be considered for hydrological modeling in karst areas. PMID:25663401

  5. Fault zone hydraulic properties provide an independent estimate of coseismic fracturing at 8 km depth (Gole Larghe Fault Zone, Italian Southern Alps)

    NASA Astrophysics Data System (ADS)

    Bistacchi, Andrea; Di Toro, Giulio; Smith, Steven; Mittempergher, Silvia; Garofalo, Paolo; Vho, Alice

    2015-04-01

    The Gole Larghe Fault Zone (GLFZ, Italian S Alps) was exhumed from c. 8 km, where it was characterized by seismic activity (pseudotachylytes) but also by hydrous fluid flow (alteration halos and precipitation of hydrothermal minerals in veins and cataclasites). The fault zone has previously been quantitatively characterized (Bistacchi 2011, PAGEOPH; Smith 2013, JSG) providing a rich dataset to generate 3D Discrete Fracture Network (DFN) models and simulate fault hydraulic properties. A fundamental parameter that cannot be directly evaluated in the field is the fraction of fractures-faults that were open over a certain time period in the evolution of the fault zone. Based on field and microstructural evidence, we infer that the opening and closing of fractures resulted in a toggle-switch mechanism for fluid flow during the seismic cycle: higher permeability was obtained in the syn- to post-seismic period, when the largest number of fractures was (re)opened by off-fault deformation, then permeability dropped due to fracture cementation. Postseismic permeability has been evaluated in a few cases in the world thanks to seismological evidence of fluid migration along active fault systems. Therefore, we were able to develop a parametric hydraulic model of the GLFZ and calibrate it to obtain the fraction of faults-fractures that were open in the postseismic period to obtain realistic fluid flow and permeability values. This fraction is very close to the percolation threshold of the DFN, and it can be converted to fracture intensity (fracture surface per unit volume in the fault zone), which could be integrated to obtain the fracture energy due to off-fault fracturing. Since the fracture energy due to on-fault processes has already been estimated for the GLFZ (Pittarello, 2008, EPSL), this also allows us to estimate the total fracture energy.

  6. Water quality impacts of hydraulic-fracturing chemicals observed in a permeable, quartz-sand aquifer

    NASA Astrophysics Data System (ADS)

    Kent, D. B.; LeBlanc, D. R.; Smith, R. L.

    2012-12-01

    A pilot scale experiment was conducted on western Cape Cod, Massachusetts to test the use of hydraulic fracturing (HF) for emplacing permeable reactive barriers (PRB) where the water table is too far below land surface to use standard excavation methods. Two PRB were emplaced 24 to 36 meters below land surface in a plume with low concentrations of perchloroethylene in oxic, mildly acidic groundwater with low concentrations of dissolved salts. The granular aquifer sediments consist of permeable sands and gravels. Quartz comprises greater than 90% by weight of the aquifer sediments but chemical reactivity of the sediments is controlled by micrometer-scale chlorite and illite and nanometer-scale aluminum-substituted goethite. HF fluids contained guar gum (gelling agent), cellulose enzyme and acetic acid (breakers), sodium borate (cross-linker), potassium (K) carbonate (pH adjustor), and sodium (Na) chloride (tracer). Water-quality impacts within about 20 meters of the PRB were monitored over a 1.7-year period following HF. Arrival of HF-chemicals was marked by an increase in boron (B) from ambient concentrations of 6 uM to >800 uM. B concentrations rose for approximately 50 days, much longer than the 22-day period over which HF was conducted. B concentrations subsequently decreased but remained 2-3 times above background concentrations for almost one year. Elevated Na and K concentrations in the HF fluids drove sorption (including ion exchange) reactions resulting in transient increases in naturally occurring major, minor, and trace cations up to 20 to 50 times background concentrations. Increases in dissolved organic carbon (DOC) and decreases in dissolved oxygen (DO) concentrations were observed as B concentrations increased. DOC concentration subsequently decreased but remained significantly above background. DO concentrations remained below detection. Dissolved iron (Fe) and manganese (Mn) concentrations increased as DO concentrations decreased below detection and remained elevated 1.7 years after HF. Reactions with Fe in the PRB may have contributed to the observed Fe concentrations but Mn was likely released from the aquifer sediments. Fe and Mn concentrations remained elevated throughout the sampling period. Dissolved arsenic concentrations increased after anaerobic conditions were established from below detection to 0.3-0.5 uM. HF fluids contained only a subset of the chemicals used in typical HF stimulations and aquifer sediments were likely less reactive than aquifer solids at other sites. Despite these differences, several findings have applicability to other sites. B is a potentially useful tracer of intrusion of HF fluids into aquifers, but elevated concentrations may be short-lived. Sorption reactions driven by differences in dissolved salt concentrations between HF fluids and ambient groundwater result in changes in cation concentrations, including barium and strontium. Organic compounds in HF fluids may drive aerobic aquifers anaerobic. Anaerobic conditions may lead to mobilization of naturally occurring contaminants like arsenic, whose reduced forms are more mobile than oxidized forms.

  7. Estimation of fracture flow parameters through numerical analysis of hydromechanical pressure pulses

    SciTech Connect

    Cappa, F.; Guglielmi, Y.; Rutqvist, J.; Tsang, C.-F.; Thoraval, A.

    2008-03-16

    The flow parameters of a natural fracture were estimated by modeling in situ pressure pulses. The pulses were generated in two horizontal boreholes spaced 1 m apart vertically and intersecting a near-vertical highly permeable fracture located within a shallow fractured carbonate reservoir. Fracture hydromechanical response was monitored using specialized fiber-optic borehole equipment that could simultaneously measure fluid pressure and fracture displacements. Measurements indicated a significant time lag between the pressure peak at the injection point and the one at the second measuring point, located 1 m away. The pressure pulse dilated and contracted the fracture. Field data were analyzed through hydraulic and coupled hydromechanical simulations using different governing flow laws. In matching the time lag between the pressure peaks at the two measuring points, our hydraulic models indicated that (1) flow was channeled in the fracture, (2) the hydraulic conductivity tensor was highly anisotropic, and (3) the radius of pulse influence was asymmetric, in that the pulse travelled faster vertically than horizontally. Moreover, our parametric study demonstrated that the fluid pressure diffusion through the fracture was quite sensitive to the spacing and orientation of channels, hydraulic aperture, storativity and hydraulic conductivity. Comparison between hydraulic and hydromechanical models showed that the deformation significantly affected fracture permeability and storativity, and consequently, the fluid pressure propagation, suggesting that the simultaneous measurements of pressure and mechanical displacement signals could substantially improve the interpretation of pulse tests during reservoir characterization.

  8. In-situ remediation of naturally occurring radioactive materials with high-permeability hydraulic fracturing 

    E-print Network

    Demarchos, Andronikos Stavros

    1998-01-01

    , and thus, eliminate the disposal problem. A high-permeability fracture design is presented which modifies existing petroleum practices by introducing within the proppant pack highly selective radionuclide sorbents. These sorbents, at calculated...

  9. Reuse of Flowback Fluids as Hydraulic Fracturing Fluids in Tight Gas Sand Reservoirs 

    E-print Network

    Haghshenas, Ashkan

    2015-05-22

    on the proppant transport and rheological properties of fracturing fluids was examined in detail. A high-pH guar/borate fluid was selected as the base fluid and loaded with different concentrations of sodium, potassium, calcium, magnesium...

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

    SciTech Connect

    David S. Schechter

    2002-10-30

    The objective of this project is to perform unique laboratory experiments with artificial fractured cores (AFCs) and X-ray CT to examine the physical mechanisms of bypassing in HFR and NFR that eventually result in less efficient CO{sub 2} flooding in heterogeneous or fracture-dominated reservoirs. This report provides results of the second semi-annual technical progress report that consists of three different topics. In the first topic, laboratory experiments were performed on a Berea core to investigate the changes in rock properties and fluid flow under different stress-state conditions. A comparative study of different stress conditions was also conducted to analyze the effect of the various loading systems. The experimental results show that fracture permeability reduces significantly as the stress increases compared to matrix permeability. The hydrostatic and triaxial stresses have greater impacts on permeability reduction compared to applying stress in the uniaxial stress condition. Fracture flow dominates when the applied stress is less, however, the matrix flow rate increases as applied stress increases and dominates at high stress even if the fracture does not heal completely. In the second topic, the preliminary results of static imbibition experiments are presented as a precursor to image the saturation profiles using X-Ray CT scanner. The static and dynamic imbibition experiments have been done previously (Schechter et al, 2002). The imaging of imbibition experiment is underway to track the saturation profiles using X-ray CT scanner. Hence, no more conclusions are drawn from this study at this time. In the last topic, the modeling of fluid flow through a single fracture incorporating the effect of surface roughness is conducted. Fracture permeability is usually estimated by a cubic law that is based on the theory of hydrodynamics for the laminar flow between flat plates. However, the cubic law is too simple to estimate the fracture permeability correctly, because the surface of real fracture is much more complicated and rougher than the surface of flat plate. Several researchers have shown that the flow characteristics of an actual fracture surface would be quite different due to the effect of tortuosity, impact of surface roughness and contact areas. Nonetheless, to date, these efforts have not converged to form a unified definition on the fracture aperture needed in the cubic law. In this study, therefore, we show that the cubic law could still be used to model small-scale and field-scale data as long as it is modeled effectively, accounting for the effect of surface roughness associated with the fracture surface. The goal of this research is to examine the effect of surface roughness for flow through fractures and to effectively incorporate them into simulations with the aid of geostatistics. Since the research has been supported with experimental results, the consistency of the results enabled us to define a methodology for single fracture simulation. This methodology successfully modeled the slow rate and pressure drop from fractured core experiments, which were earlier not possible through parallel plate approach. Observations suggest that the fracture aperture needs to be distributed to accurately model the experimental results. The effect of friction and tortuosity due to surface roughness needs to be taken into account while modeling.

  11. Evidence of Reopened Microfractures in Production Data of Hydraulically Fractured Shale Gas Wells 

    E-print Network

    Apiwathanasorn, Sippakorn

    2012-10-19

    Frequently a discrepancy is found between the stimulated shale volume (SSV) estimated from production data and the SSV expected from injected water and proppant volume. One possible explanation is the presence of a fracture network, often termed...

  12. Hydraulic and mechanical properties of natural fractures in low-permeability rock

    SciTech Connect

    Pyrack-Nolte, L.J.; Myer, L.R.; Cook, N.G.W.; Witherspoon, P.A.

    1987-01-01

    The results of a comprehensive laboratory study of the mechanical displacement, permeability, and void geometry of single rock fractures in a quartz monzonite are summarized and analyzed. A metal-injection technique was developed that provided quantitative data on the precise geometry of the void spaces between the fracture surfaces and the areas of contact at different stresses. At effective stresses of less than 20 MPa fluid flow was proportional to the mean fracture aperture raised to a power greater than 3. As stress was increased, contact area was increased and void spaces become interconnected by small tortuous channels that constitute the principal impediment to fluid flow. At effective stresses higher than 20 MPa, the mean fracture aperture continued to diminish with increasing stress, but this had little effect on flow because the small tortuous flow channels deformed little with increasing stress.

  13. Diagnostic Value of Cone-Beam Computed Tomography and Periapical Radiography In Detection of Vertical Root Fracture

    PubMed Central

    Ezzodini Ardakani, Fatemeh; Razavi, Seyed Hossein; Tabrizizadeh, Mehdi

    2015-01-01

    Introduction: Vertical root fracture (VRF) is the longitudinal fracture of the root in endodontically treated teeth. Considering the limitations of two-dimensional radiographic images in detection of VRF and introduction of cone-beam computed tomography (CBCT), this study was designed to find the sensitivity, specificity and accuracy of CBCT and periapical (PA) radiography in detection of VRFs. Methods and Materials: This was a cross-sectional in vitro study on 80 extracted human single canal teeth including 40 maxillary and 40 mandibular teeth. After standardized endodontic treatment of the roots, VRF was induced in half of the teeth in each group, and other half were left without fracture. Teeth were inserted in dry maxillary and mandibular alveoli. PA radiographs and CBCT images were taken from the specimens. Data were analyzed with SPSS software. The McNemar test was used to evaluate the sensitivity, specificity and accuracy of images, and kappa coefficient was used to assess the degree of agreement between the observers. The level of significance was set at 0.05. Results: Sensitivity and specificity values of CBCT were 97.5% and 95%, respectively. However, for PA radiography the sensitivity and specificity were 67.5% and 92.5%, in order of appearance. Accuracy of CBCT (96.25%) and PA radiography (80%) in both jaws were significantly different (P=0.022). Two methods were not significantly different when testing specificity (P=0.298). Conclusion: This study showed that the sensitivity and accuracy of CBCT in detection of vertical root fracture are higher than periapical radiography. CBCT can be recommended to be used in detection of vertical root fractures. PMID:25834597

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  15. Investigation of Efficiency Improvements During CO2 Injection in Hydraulically and Naturally Fractured Reservoirs

    SciTech Connect

    Schechter, David S.; Vance, Harold

    2003-03-10

    The objective of this project was to perform unique laboratory experiments with artificial fractured cores (AFCs) and X-ray CT to examine the physical mechanisms of bypassing in HFR and NFR that eventually result in less efficient CO2 flooding in heterogeneous or fracture-dominated reservoirs. This report provided results of the second semi-annual technical progress report that consists of three different topics.

  16. Diagnosis of Vertical Root Fracture with Cone-Beam Computerized Tomography in Endodontically Treated Teeth: Three Case Reports

    PubMed Central

    Miyagaki, Daniela Cristina; Marion, Jefferson; Randi Ferraz, Caio Cézar

    2013-01-01

    A definitive diagnosis of vertical root fracture (VRF) is often a challenging task for clinicians. This is because two dimensional periapical radiographs are usually unable to detect the fracture line due to the direction of the X-ray beam. This report presents a set of 3 cases of endodontically treated teeth that were diagnosed with VRFs based on findings from clinical, radiographic, and cone-beam computerized tomographic (CBCT) examinations. After extraction, VRFs were confirmed in all cases. The presence of periodontal pockets or other signs which would compromise the correct diagnosis could not be detected in all three cases. Fracture lines were only visible with the aid of CBCT which provided useful information for the diagnosis and management of VRF. However, the clinical and radiographic data should not be discarded, but used in conjunction with CBCT. PMID:23717335

  17. Fault zone hydraulic properties provide an independent estimate of fracture energy at 8 km depth (Gole Larghe Fault Zone, Italian Southern Alps)

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Partitioning of the earthquake energy budget into heat, radiated seismic energy, and fracture energy, is still a fundamental issue in seismology. Different estimates are provided by seismological studies, but only a few attempts have been made at using structural studies of palaeoseismic faults, exhumed and exposed at the surface, to evaluate this partitioning. Here we present an independent estimate of fracture energy based on the evolution of hydraulic properties during the seismic cycle along an exhumed fault. The Gole Larghe Fault Zone (GLFZ, Italian S Alps) was exhumed from c. 8 km, where it was characterized by seismic activity (pseudotachylytes) but also by hydrous fluid flow (alteration halos and precipitation of hydrothermal minerals in veins and cataclasites). The fault zone has previously been quantitatively characterized (Bistacchi 2011; Smith 2013) providing a rich dataset to generate 3D Discrete Fracture Network (DFN) models and simulate fault hydraulic properties. A fundamental parameter that cannot be directly evaluated in the field is the fraction of fractures-faults that were open over a certain time period in the evolution of the fault zone. Based on field and microstructural evidence, we infer that the opening and closing of fractures resulted in a toggle-switch mechanism for fluid flow during the seismic cycle: higher permeability was obtained in the syn- to post-seismic period, when the largest number of fractures was (re)opened by off-fault deformation, then permeability dropped due to fracture cementation. Postseismic permeability has been evaluated in a few cases in the world thanks to seismological evidence of fluid migration along active fault systems. Therefore, we were able to develop a parametric hydraulic model of the GLFZ and calibrate it to obtain the fraction of faults-fractures that were open in the postseismic period to obtain realistic fluid flow and permeability values. This fraction is very close to the percolation threshold of the DFN, and it can be converted to fracture intensity (fracture surface per unit volume in the fault zone), which could be integrated to obtain the fracture energy due to off-fault fracturing. Since the fracture energy due to on-fault processes has already been estimated for the GLFZ (Pittarello 2008), this allows us to estimate the total fracture energy.

  18. A Resolution of the First Unitarian Universalist Society of Albany to Oppose the Current Practice of Hydraulic Fracturing and Support the

    E-print Network

    Bystroff, Chris

    -volume hydraulic fracturing ("fracking") is a recently- developed technology for extracting methane gas from shale, environmental, economic, and policy aspects of fracking in light of Unitarian Universalist principles; III that fracking endangers human health because it uses, without proper safeguards, toxic chemicals that are known

  19. A comparison of microseismicity induced by gel-proppant-and water-injected hydraulic fractures, Carthage Cotton Valley gas field, East Texas

    E-print Network

    , Carthage Cotton Valley gas field, East Texas J.T. Rutledge* and W.S. Phillips, Los Alamos National induced during a series of hydraulic fracture completions within the Cotton Valley formation of East Texas- proppant treatments in Cotton Valley reservoirs, but at greatly reduced cost (Mayerhofer and Meehan, 1998

  20. School and Community Impacts of Hydraulic Fracturing within Pennsylvania's Marcellus Shale Region, and the Dilemmas of Educational Leadership in Gasfield Boomtowns

    ERIC Educational Resources Information Center

    Schafft, Kai A.; Biddle, Catharine

    2014-01-01

    Innovations associated with gas and oil drilling technology, including new hydraulic fracturing and horizontal drilling techniques, have recently led to dramatic boomtown development in many rural areas that have endured extended periods of economic decline. The Marcellus Shale play, one of the world's largest gas-bearing shale formations,…

  1. Overview of EPA's Approach to Developing Prospective Case Studies Technical Workshop: Case Studies to Assess Potential Impacts of Hydraulic Fracturing on Drinking Water Resources

    EPA Science Inventory

    One component of the United States Environmental Protection Agency's (EPA) study of the potential impacts of hydraulic fracturing on drinking water resources is prospective case studies, which are being conducted to more fully understand and assess if and how site specific hydrau...

  2. Data regarding hydraulic fracturing distributions and treatment fluids, additives, proppants, and water volumes applied to wells drilled in the United States from 1947 through 2010

    USGS Publications Warehouse

    Gallegos, Tanya J.; Varela, Brian A.

    2015-01-01

    Comprehensive, published, and publicly available data regarding the extent, location, and character of hydraulic fracturing in the United States are scarce. The objective of this data series is to publish data related to hydraulic fracturing in the public domain. The spreadsheets released with this data series contain derivative datasets aggregated temporally and spatially from the commercial and proprietary IHS database of U.S. oil and gas production and well data (IHS Energy, 2011). These datasets, served in 21 spreadsheets in Microsoft Excel (.xlsx) format, outline the geographical distributions of hydraulic fracturing treatments and associated wells (including well drill-hole directions) as well as water volumes, proppants, treatment fluids, and additives used in hydraulic fracturing treatments in the United States from 1947 through 2010. This report also describes the data—extraction/aggregation processing steps, field names and descriptions, field types and sources. An associated scientific investigation report (Gallegos and Varela, 2014) provides a detailed analysis of the data presented in this data series and comparisons of the data and trends to the literature.

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

    SciTech Connect

    David S. Schechter

    2005-09-28

    The objective of this project is to perform unique laboratory experiments with artificial fractured cores (AFCs) and X-ray CT to examine the physical mechanisms of bypassing in HFR and NFR that eventually result in more efficient CO{sub 2} flooding in heterogeneous or fracture-dominated reservoirs. To achieve this objective, we divided the report into two chapters. The first chapter was to image and perform experimental investigation of transfer mechanisms during CO{sub 2} flooding in NFR and HFR using X-ray CT scanner. In this chapter, we emphasized our work on understanding the connection between fracture properties and fundamentals of transfer mechanism from matrix to fractures and fluid flow through fracture systems. We started our work by investigating the effect of different overburden pressures and stress-state conditions on rock properties and fluid flow. Since the fracture aperture is one of important parameter that governs the fluid flow through the fracture systems, the average fracture aperture from the fluid flow experiments and fracture aperture distribution derived from X-ray CT scan were estimated for our modeling purposes. The fracture properties and fluid flow have significant changes in response to different overburden pressures and stress-state conditions. The fracture aperture distribution follows lognormal distribution even at elevated stress conditions. Later, we also investigated the fluid transfers between matrix and fracture that control imbibition process. We evaluated dimensionless time for validating the scheme of upscaling laboratory experiments to field dimensions. In CO{sub 2} injection experiments, the use of X-ray CT has allowed us to understand the mechanisms of CO{sub 2} flooding process in fractured system and to take important steps in reducing oil bypassed. When CO{sub 2} flooding experiments were performed on a short core with a fracture at the center of the core, the gravity plays an important role in the recovery of oil even in a short matrix block. This results are contrary with the previous believes that gravity drainage has always been associated with tall matrix blocks. In order to reduce oil bypassed, we injected water that has been viscosified with a polymer into the fracture to divert CO{sub 2} flow into matrix and delay CO{sub 2} breakthrough. Although the breakthrough time reduced considerably, water ''leak off'' into the matrix was very high. A cross-linked gel was used in the fracture to avoid this problem. The gel was found to overcome ''leak off'' problems and effectively divert CO{sub 2} flow into the matrix. As part of our technology transfer activity, we investigated the natural fracture aperture distribution of Tensleep formation cores. We found that the measured apertures distributions follow log normal distribution as expected. The second chapter deals with analysis and modeling the laboratory experiments and fluid flow through fractured networks. We derived a new equation to determine the average fracture aperture and the amount of each flow through fracture and matrix system. The results of this study were used as the observed data and for validating the simulation model. The idea behind this study is to validate the use of a set of smooth parallel plates that is common in modeling fracture system. The results suggest that fracture apertures need to be distributed to accurately model the experimental results. In order to study the imbibition process in details, we developed imbibition simulator. We validated our model with X-ray CT experimental data from different imbibition experiments. We found that the proper simulation model requires matching both weight gain and CT water saturation simultaneously as oppose to common practices in matching imbibition process with weight gain only because of lack information from CT scan. The work was continued by developing dual porosity simulation using empirical transfer function (ETF) derived from imbibition experiments. This allows reduction of uncertainty parameter in modeling transfer of fluids from matrix to the fra

  4. Regional air quality impacts of hydraulic fracturing and shale natural gas activity: Evidence from ambient VOC observations

    NASA Astrophysics Data System (ADS)

    Vinciguerra, Timothy; Yao, Simon; Dadzie, Joseph; Chittams, Alexa; Deskins, Thomas; Ehrman, Sheryl; Dickerson, Russell R.

    2015-06-01

    Over the past decade, concentrations of many anthropogenic pollutants have been successfully reduced, improving air quality. However, a new influx of emissions associated with hydraulic fracturing and shale natural gas operations could be counteracting some of these benefits. Using hourly measurements from Photochemical Assessment Monitoring Stations (PAMS) in the Baltimore, MD and Washington, DC areas, we observed that following a period of decline, daytime ethane concentrations have increased significantly since 2010, growing from ?7% of total measured nonmethane organic carbon to ?15% in 2013. This trend appears to be linked with the rapidly increasing natural gas production in upwind, neighboring states, especially Pennsylvania and West Virginia. Ethane concentrations failed to display this trend at a PAMS site outside of Atlanta, GA, a region without new widespread natural gas operations.

  5. Hydraulic-fracturing measurmements in two boreholes near the Spent Fuel Test-Climax, Climax Stock, Nevada Test Site

    USGS Publications Warehouse

    Ellis, William L.

    1983-01-01

    Hydraulic-fracturing measurements are used to infer the magnitude of the least principal stress in the vicinity of the Spent Fuel Test-Climax, located in the Climax stock at the Nevada Test Site. The measurements, made at various depths in two exploratory boreholes, suggest that the local stress field is not uniform. Estimates of the least principal stress magnitude vary over distances of a few tens of meters, with the smaller values averaging 2.9 MPa and the larger values averaging 5.5 MPa. The smaller values are in agreement with the minimum-stress magnitude of 2.8 MPa determined in a nearby drift in 1979, using an overcoring technique. Jointing in the granitic rock mass and (or) the influence of nearby faults may account for the apparent variation in minimum-stress magnitude indicated by the hydrofracture data.

  6. Simulate speleogenesis processes with an approach based on fracturing and hydrogeological processes: effect of various hydraulic boundary conditions

    NASA Astrophysics Data System (ADS)

    Lafare, A.; Jourde, H.; Leonardi, V.; Pistre, S.; Dörfliger, N.

    2012-04-01

    Several numerical modeling approaches attempted to simulate the processes of karst conduit genesis. These existing methods are mainly based on the physical and chemical laws driving the carbonate dissolution processes (taking account of calcite saturation of the water and the partial pressure of carbon dioxide). As a consequence, these works bring a well-documented knowledge on the kinetics of the carbonate dissolution processes in karst systems. Nevertheless, these models are mainly applied on simplified initial void networks, which do not match the fracturing and geological reality. Considering that the initial geometry of the void network (fractures, bedding planes) would have an influence on the final pattern of the speleological network, taking account of it could improve the understanding of speleogenesis. In the aim to take into account the geometry of the initial void network (fracture networks of several orders), a numerical model is developed, which involves a pseudo-statistic fracturing generator (REZO3D, Jourde 1999, Josnin et al. 2002, Jourde et al. 2002) coupled to a finite element groundwater simulator (GROUNDWATER, F. Cornaton, CHYN, University of Neuchâtel). The principle of the modeling of the genesis of the karst drainage system is based on an analogical empirical polynomial equation considering the pore velocity and the mean age of the water as main parameters. The computation is carried out on the basis of a time step, whose duration depends on the simulated scenario (from 100 to 5000 years). The mean age of the water is used in order to simulate the decrease of the chemical dissolving potential of the water within the aquifer, in contact with the carbonate rock. The first simulator -REZO3D- allows producing three-dimensional discrete fracture networks constituted by plane fractures, whose spatial distribution respects mechanical and statistical laws. These networks are then processed in order to write finite element meshes which constitute the bases of groundwater flow and transport simulations. The polynomial parameters of the equation are calibrated with former speleogenesis studies (Dreybrodt 1996, Dreybrodt et al. 2005, Palmer 1991). The presented study involves two orthogonal families of fractures embedded in a carbonate matrix, in a mono-stratum setting. For each simulation, several settings of boundary conditions are tested, in terms of recharge (diffuse or concentrated, hydraulic head or flux limited) and discharge (spatial position, punctual or diffuse). The results are interpreted in terms of head fields, mean groundwater age distributions and total flow rates as a function of time. The aim is to assess the influence of the hydraulic boundary conditions on the finally obtained morphologies of the karstic networks, and on the velocity of the evolution of the drainage system. Results are discussed and perspectives are given on the application of such model to real case studies.

  7. A Site Characterization Protocol for Evaluating the Potential for Triggered or Induced Seismicity Resulting from Wastewater Injection and Hydraulic Fracturing

    NASA Astrophysics Data System (ADS)

    Walters, R. J.; Zoback, M. D.; Gupta, A.; Baker, J.; Beroza, G. C.

    2014-12-01

    Regulatory and governmental agencies, individual companies and industry groups and others have recently proposed, or are developing, guidelines aimed at reducing the risk associated with earthquakes triggered by waste water injection or hydraulic fracturing. While there are a number of elements common to the guidelines proposed, not surprisingly, there are also some significant differences among them and, in a number of cases, important considerations that are not addressed. The goal of this work is to develop a comprehensive protocol for site characterization based on a rigorous scientific understanding of the responsible processes. Topics addressed will include the geologic setting (emphasizing faults that might be affected), historical seismicity, hydraulic characterization of injection and adjacent intervals, geomechanical characterization to identify potentially active faults, plans for seismic monitoring and reporting, plans for monitoring and reporting injection (pressure, volumes, and rates), other factors contributing to risk (potentially affected population centers, structures, and facilities), and implementing a modified Probabilistic Seismic Hazard Analysis (PSHA). The guidelines will be risk based and adaptable, rather than prescriptive, for a proposed activity and region of interest. They will be goal oriented and will rely, to the degree possible, on established best practice procedures, referring to existing procedures and recommendations. By developing a risk-based site characterization protocol, we hope to contribute to the development of rational and effective measures for reducing the risk posed by activities that potentially trigger earthquakes.

  8. Hydraulic transmissivity and heat exchange efficiency of open fractures: a model based on lowpass filtered apertures

    E-print Network

    Neuville, Amélie; Schmittbuhl, Jean; 10.1111/j.1365-246X.2011.05126.x

    2011-01-01

    Natural open joints in rocks commonly present multi-scale self-affine apertures. This geometrical complexity affects fluid transport and heat exchange between the flow- ing fluid and the surrounding rock. In particular, long range correlations of self-affine apertures induce strong channeling of the flow which influences both mass and heat advection. A key question is to find a geometrical model of the complex aperture that describes at best the macroscopic properties (hydraulic conductivity, heat exchange) with the smallest number of parameters. Solving numerically the Stokes and heat equa- tions with a lubrication approximation, we show that a low pass filtering of the aperture geometry provides efficient estimates of the effective hydraulic and thermal properties (apertures). A detailed study of the influence of the bandwidth of the lowpass filtering on these transport properties is also performed. For instance, keeping the information of amplitude only of the largest Fourier length scales allows us to rea...

  9. Fracture orientation determination in Sandhills (McKnight) field, Crane County, Texas

    SciTech Connect

    Olive, C.

    1988-01-01

    A fracture identification log (FILMAP, Schlumberger) provided an orientation of vertical fracturing in the Sandhills (McKnight) field, Crane County, Texas. During workover operations to deepen an existing well bore to test a lower porosity interval, a 200-ft core was obtained that intersected a fracture plane in several sections of the core. Verification of this fracture having been hydraulically induced (or enhanced through hydraulic stimulation) was established with the discovery of frac-sand grains along the face of the fracture. The 300-ft open-hole section of the original well bore had been fracture stimulated with 30,000 gal of refined oil and 45,000 lb of sand. The fracture identification log was included as a part of the formation evaluation program to ascertain the orientation of the fracture(s). This tool measures the differences in resistivities along a horizontal plane of the bore hole by detecting fractures that bisect the hold and determines their orientation.

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

    SciTech Connect

    David S. Schechter

    2002-04-01

    For many years many efforts have been performed in the laboratory experiments to duplicate the reservoir conditions. In this study, we will investigate the permeability change at different overburden conditions. The reduction in permeability with overburden pressure has been well known. Fatt and Davis (1952) presented the changes in permeability with pressure at range 0 to 15,000 psig and found that overburden pressure caused a reduction in permeability of the consolidated oil-bearing sandstone samples by as much as 50% at 10,000 psig. Wyble (1958) performed similar experiments on three different sandstone samples to determine the changes in conductivity, porosity and permeability at pressure range 0 to 5,000 psig. His results were consistent with the observation by Fatt and Davis (1952). During the experiments, different overburden pressures (radial force) were applied only to the cylinder core while the axial direction was kept at constant atmospheric pressure. Gray et al. (1963) enhanced the previous experiments by applying axial force and combining with overburden pressure (radial force) to measure the anisotropy permeability changes at more representative reservoir stress-state condition. They showed that permeability reduction subjected to overburden pressure as a function of the ratio of radial to axial stress and the permeability reduction under non-uniform stress (radial pressure {ne} axial pressure) is less than that under uniform stress. Although extensive work has been established on the effect of overburden pressure and stress-state on matrix permeability but there are some very interesting details of fractured rock behavior under stress that have not been investigated. In this study we will show the effect of fracture aperture and fracture permeability on the fluid flow under different overburden pressure. This study is a precursor to investigating fracture apertures under different stress-state conditions (confining stress, hydrostatic stress and triaxial stress) and imaging fracture aperture distributions using X-ray CT.

  11. Viral Predation and Host Immunity Structure Microbial Communities in a Terrestrial Deep Subsurface, Hydraulically Fractured Shale System

    NASA Astrophysics Data System (ADS)

    Daly, R. A.; Mouser, P. J.; Trexler, R.; Wrighton, K. C.

    2014-12-01

    Despite a growing appreciation for the ecological role of viruses in marine and gut systems, little is known about their role in the terrestrial deep (> 2000 m) subsurface. We used assembly-based metagenomics to examine the viral component in fluids from hydraulically fractured Marcellus shale gas wells. Here we reconstructed microbial and viral genomes from samples collected 7, 82, and 328 days post fracturing. Viruses accounted for 4.14%, 0.92% and 0.59% of the sample reads that mapped to the assembly. We identified 6 complete, circularized viral genomes and an additional 92 viral contigs > 5 kb with a maximum contig size of 73.6 kb. A BLAST comparison to NCBI viral genomes revealed that 85% of viral contigs had significant hits to the viral order Caudovirales, with 43% of sequences belonging to the family Siphoviridae, 38% to Myoviridae, and 12% to Podoviridae. Enrichment of Caudovirales viruses was supported by a large number of predicted proteins characteristic of tailed viruses including terminases (TerL), tape measure, tail formation, and baseplate related proteins. The viral contigs included evidence of lytic and temperate lifestyles, with the 7 day sample having the greatest number of detected lytic viruses. Notably in this sample, the most abundant virus was lytic and its inferred host, a member of the Vibrionaceae, was not detected at later time points. Analyses of CRISPR sequences (a viral and foreign DNA immune system in bacteria and archaea), linked 18 viral contigs to hosts. CRISPR linkages increased through time and all bacterial and archaeal genomes recovered in the final time point had genes for CRISPR-mediated viral defense. The majority of CRISPR sequences linked phage genomes to several Halanaerobium strains, which are the dominant and persisting members of the community inferred to be responsible for carbon and sulfur cycling in these shales. Network analysis revealed that several viruses were present in the 82 and 328 day samples; this viral persistence is consistent with concomitant temporal stability in geochemistry and microbial community composition. Our findings suggest that after a disturbance (hydraulic fracturing) viral predation and host immunity is an important controller of microbial community structure, metabolism, and thus biogeochemical cycling in the deep subsurface.

  12. Geological and petrological considerations relevant to the disposal of radioactive wastes by hydraulic fracturing: an example at the US Department of Energy's Oak Ridge National Laboratory. [Pumpkin Valley shales

    SciTech Connect

    Haase, C.S.

    1982-01-01

    At Oak Ridge National Laboratory the Pumpkin Valley Shale is used as a host formation for hydraulic-fracturing waste disposal. Determination of the relationships between the distribution of different lithologies and porosity-permeability trends within this host formation allows these properties, important to hydraulic-fracturing operations, to be related to measurable and mappable geological and petrological parameters. It also permits extrapolation of such patterns to little-studied portions of the Pumpkin Valley Shale. Such knowledge better allows for the satisfactory operation and assessment of the hydraulic fracturing at Oak Ridge National Laboratory.

  13. A physical model study of converted wave amplitude variation in a reservoir of systematically aligned vertical fractures

    NASA Astrophysics Data System (ADS)

    Chang, C.; Sun, L.; Lin, C.; Chang, Y.; Tseng, P.

    2013-12-01

    The existence of fractures not only provides spaces for the residence of oils and gases reside, but it also creates pathways for migration. Characterizing a fractured reservoir thus becomes an important subject and has been widely studied by exploration geophysicists and drilling engineers. In seismic anisotropy, a reservoir of systematically aligned vertical fractures (SAVF) is often treated as a transversely isotropic medium (TIM) with a horizontal axis of symmetry (HTI). Subjecting to HTI, physical properties vary in azimuth. P-wave reflection amplitude, which is susceptible to vary in azimuth, is one of the most popular seismic attributes which is widely used to delineate the fracture strike of an SAVF reservoir. Instead of going further on analyzing P-wave signatures, in this study, we focused on evaluating the feasibility of orienting the fracture strike of an SAVF reservoir using converted (C-) wave amplitude. For a C-wave is initiated by a downward traveling P-wave that is converted on reflection to an upcoming S-wave; the behaviors of both P- and S-waves should be theoretically woven in a C-wave. In our laboratory work, finite offset reflection experiments were carried out on the azimuthal plane of a HTI model at two different offset intervals. To demonstrate the azimuthal variation of C-wave amplitude in a HTI model, reflections were acquired along the principal symmetry directions and the diagonal direction of the HTI model. Inheriting from phenomenon of S-wave splitting in a transversely isotropic medium (TIM), P-waves get converted into both the fast (S1) and slow (S2) shear modes at all azimuths outside the vertical symmetry planes, thus producing split PS-waves (PS1 and PS2). In our laboratory data, the converted PS1- (C1-) wave were observed and identified. As the azimuth varies from the strike direction to the strike normal, C1-wave amplitude exhibits itself in a way of weakening and can be view from the common-reflection-point (CRP) gathers. Therefore, in conjunction with the azimuthal velocity and the amplitude variations in the P-wave and the azimuthal polarization of the S-wave, the azimuthal variation of C-wave amplitude which is experimentally demonstrated could be considered as a valuable seismic attribute in orienting the fracture strike of a SAVF reservoir. (Key words: converted wave, transversely isotropic medium, physical modeling, amplitude, fracture)

  14. The functional potential of microbial communities in hydraulic fracturing source water and produced water from natural gas extraction characterized by metagenomic sequencing

    SciTech Connect

    Mohan, Arvind Murali; Bibby, Kyle J.; Lipus, Daniel; Hammack, Richard W.; Gregory, Kelvin B.; Forster, Robert J.

    2014-10-22

    Microbial activity in produced water from hydraulic fracturing operations can lead to undesired environmental impacts and increase gas production costs. However, the metabolic profile of these microbial communities is not well understood. Here, for the first time, we present results from a shotgun metagenome of microbial communities in both hydraulic fracturing source water and wastewater produced by hydraulic fracturing. Taxonomic analyses showed an increase in anaerobic/facultative anaerobic classes related to Clostridia, Gammaproteobacteria, Bacteroidia and Epsilonproteobacteria in produced water as compared to predominantly aerobic Alphaproteobacteria in the fracturing source water. Thus, the metabolic profile revealed a relative increase in genes responsible for carbohydrate metabolism, respiration, sporulation and dormancy, iron acquisition and metabolism, stress response and sulfur metabolism in the produced water samples. These results suggest that microbial communities in produced water have an increased genetic ability to handle stress, which has significant implications for produced water management, such as disinfection.

  15. A comparison of microseismicity induced by gel-proppant-and water-injected hydraulic fractures, Carthage Cotton Valley gas field, East Texas

    SciTech Connect

    Rutledge, J. T.; Phillips, W. S.

    2002-01-01

    In May and July, 1997, a consortia of operators and service companies conducted a series of hydraulic fracture imaging tests in the Carthage Cotton Valley gas field of East Texas (Walker, 1997). Microseismic data were collected and processed for six hydraulic fracture treatments in two wells (3 completion intervals per well) (Mayerhofer et al., 2000). One well was completed with gel-proppant treatments in which a viscous crosslink gel was injected to entrain high concentrations of sand proppant into formation. The second well was completed using treated water and very low proppant concentrations (waterfracs). Waterfracs have been shown to be just as effective as the conventional gel-proppant treatments in Cotton Valley reservoirs, but at greatly reduced cost. Mayerhofer and Meehan (1998) suggest two possible reasons why waterfracs are successful: (1) Induced shear displacement along natural and hydraulic fractures results in self-propping (shear dilation enhanced by fracture branching, proppant and spalled rock fragments), and (2) Fracture extension and cleanup is easier to achieve with low-viscosity fluids. With improved source location precision and focal mechanism determination (fracture plane orientation and sense of slip), we have reexamined the Cotton Valley data, comparing the seismicity induced by water and gel-proppant treatments at common depth intervals. We have improved the location precision and computed focal mechanism of microearthquakes induced during a series of hydraulic fracture completions within the Cotton Valley formation of East Texas. Conventional gel-proppant treatments and treatments using treated water and very low proppant concentrations (waterfracs) were monitored. Waterfracs have been shown to be just as effective as the conventional gel-proppant treatments in Cotton Valley reservoirs, but at greatly reduced cost (Mayerhofer and Meehan, 1998). Comparison of the seismicity induced by the two treatment types show similar distributions of event locations and focal mechanisms for common depth intervals. We interpret the induced seismicity to be primarily controlled by the natural fracture geometry and independent of treatment design. By implication, we expect the effectiveness of shear-induced fracture propping to be independent of the treatment fluid in Cotton Valley reservoirs.

  16. Reconstruction and Intentional Replantation of a Maxillary Central Incisor with a Complete Vertical Root Fracture: A Rare Case Report with Three Years Follow up

    PubMed Central

    Dua, Deepti

    2015-01-01

    Vertical root fractures in teeth present with challenges not only with diagnosis but also with management. The prognosis in such teeth is generally questionable with extraction of the tooth being the most common treatment option. However, conservative treatment options such as reconstruction of the fractured fragments with adhesive resin followed by intentional replantation have been recently suggested. There are only a few case reports that describe management of complete vertical root fracture by reconstruction of fragments. The present case report describes successful management of an unusual complete vertical root fracture of a maxillary right central incisor in a 23-year-old male by reconstructing the fragments with a dual cure resin followed by intentional replantation. At the three year follow up, the tooth was asymptomatic, radiographically sound with probing depth and mobility within normal physiological limits. PMID:26501026

  17. Intermediate-depth icequakes and harmonic tremor in an Alpine glacier (Glacier d'Argentière, France): Evidence for hydraulic fracturing?

    NASA Astrophysics Data System (ADS)

    Helmstetter, Agnès.; Moreau, Luc; Nicolas, Barbara; Comon, Pierre; Gay, Michel

    2015-03-01

    We detected several thousand deep englacial icequakes on Glacier d'Argentière (Mont-Blanc massif) between 30 March and 3 May 2012. These events have been classified in eight clusters. Inside each cluster, the waveforms are similar for P waves and S waves, although the time delay between the P waves and the S waves vary by up to 0.03 s, indicating an extended source area. Although these events were recorded by a single accelerometer, they were roughly located using a polarization analysis. The deepest events were located at a depth of 130 m, 60 m above the ice/bed interface. The clusters are separated in space. The largest cluster extends over about 100 m. For this cluster, the strike of the rupture plane is nearly parallel to the direction of the open crevasses, and the dip angle is 56°. Deep icequakes occur in bursts of activity that last for a few hours and are separated by quiet periods. Many events occurred on 28 and 29 April 2012, during the warmest days, when snowmelting was likely important. The distributions of interevent times and peak amplitudes obey power laws as also observed for earthquakes, but with larger exponents. The polarity of the P waves for all of the events is consistent with tensile faulting. Finally, between 25 April and 3 May, we observed a gliding harmonic tremor with a fundamental resonance frequency that varied between 30 Hz and 38 Hz, with additional higher-frequency harmonics. During this time we also observed shallow hybrid events with high-frequency onsets and a monochromatic coda. These events might be produced by the propagation of fractures and the subsequent flow of water into the fracture. The strongest resonance was observed just after a strong burst of deep icequakes and during an unusually warm period when the snow height decreased by 60 cm in 1 week. The resonance frequency shows a succession of several sharp decreases and phases of progressive increases. One of the strongest negative steps of the resonance frequency on 28 April coincides with a burst of deep icequakes. These events appear to be associated with the propagation of fractures, which can explain the decrease in the resonance frequency. Finally, we observed an acceleration of glacier flow on 29 April, suggesting that meltwater had reached the ice/bed interface. These observations suggest that deep icequakes are due to hydraulic fracturing and that they can be used to track fluid flow inside glaciers.

  18. Parallel analysis of finite element model controlled trial and retrospective case control study on percutaneous internal fixation for vertical sacral fractures

    PubMed Central

    2013-01-01

    Background Although percutaneous posterior-ring tension-band metallic plate and percutaneous iliosacral screws are used to fix unstable posterior pelvic ring fractures, the biomechanical stability and compatibility of both internal fixation techniques for the treatment of Denis I, II and III type vertical sacral fractures remain unclear. Methods Using CT and MR images of the second generation of Chinese Digitized Human “male No. 23”, two groups of finite element models were developed for Denis I, II and III type vertical sacral fractures with ipsilateral superior and inferior pubic ramus fractures treated with either a percutaneous metallic plate or a percutaneous screw. Accordingly, two groups of clinical cases that were fixed using the above-mentioned two internal fixation techniques were retrospectively evaluated to compare postoperative effect and function. Parallel analysis was performed with a finite element model controlled trial and a case control study. Results The difference of the postoperative Majeed standards and outcome rates between two case groups was no statistically significant (P?>?0.05). Accordingly, the high values of the maximum displacements/stresses of the plate-fixation model group approximated those of the screw-fixation model group. However, further simulation of Denis I, II and III type fractures in each group of models found that the biomechanics of the plate-fixation models became increasingly stable and compatible, whereas the biomechanics of the screw-fixation models maintained tiny fluctuations. When treating Denis III fractures, the biomechanical effects of the pelvic ring of the plate-fixation model were better than the screw-fixation model. Conclusions Percutaneous plate and screw fixations are both appropriate for the treatment of Denis I and II type vertical sacral fractures; whereas percutaneous plate fixation appears be superior to percutaneous screw fixation for Denis III type vertical sacral fracture. Biomechanical evidence of finite element evaluations combined with clinical evidence will contribute to our ability to distinguish between indications that require plate or screw fixation for vertical sacral fractures. PMID:23879618

  19. Geophysical data from boreholes DM1, DM2, DM3, and DM3a, New Hydraulic Fracturing Facility, Oak Ridge National Laboratory, Oak Ridge, Tennessee

    SciTech Connect

    Haase, C S

    1987-03-01

    A comprehensive suite of geophysical logs was obtained from four deep monitoring boreholes at the New Hydrofracture Facility. The logging was an attempt to obtain stratigraphic, structural, and hydrologic information on the subsurface environment surrounding the hydrofracture facility. Logs obtained include caliper, gamma, neutron, density, single-point resistance, long- and short-normal resistivity, spontaneous potential, temperature, acoustic velocity, variable density, and borehole televiewer. Analysis and interpretation of the geophysical logs allowed the stratigraphic section at the facility to be determined and, by comparison with calibrated geophysical logs from borehole ORNL-Joy No. 2, allowed detailed inferences to be drawn about rock types and properties at the hydrofracture facility. Porosity values measured from the logs for Conasauga Group strata, as well as permeability values inferred from the logs, are low. Several intervals of apparently greater permeability, associated primarily with limestone-rich portions of the Maryville Limestone and sandstone-rich portions of the Rome Formation, were noted. Numerous fractures were identified by using several logs in combination. No one geophysical log was reliable for fracture identification although the acoustic-televiewer log appeared to have the greatest success. In addition to their characterization of subsurface conditions in the vicinity of the hydrofracture facility, the geophysical logs provided data on the extent of hydraulic fractures. Anomalies on single-point resistance logs that corresponded to prominent fractures identified on televiewer logs indicate intervals affected by hydraulic fractures associated with waste injection at the New Hydrofracture Facility. 14 refs.

  20. Investigating multi-polarization GPR wave transmission through thin layers: Implications for vertical fracture characterization

    E-print Network

    Tsoflias, Georgios P.; Hoch, Anthony

    2006-10-18

    We investigate the controls governing the response of ground-penetrating radar (GPR) wave transmission through thin layers in order to explore the use of variable polarization GPR signals for remote characterization of fracture aperture and fluid...

  1. Measuring the vertical permeability of horizontally- stratified sedimentary rocks

    SciTech Connect

    Novakowski, K.S.; Lapcevic, P.A. ); Reichart, T.M. )

    1993-03-01

    The vertical permeability of horizontally stratified rocks is usually assumed to be significantly less than the permeability of horizontal structural features such as bedding plane partings and sheeting structure. Consequently it is also assumed that this type of media provides suitable vertical barriers to the migration of both aqueous and non-aqueous phase groundwater contaminants. To investigate this assumption, a site adjacent to an inactive dolostone quarry was instrumented using nine boreholes drilled to a depth of approximately 25 m in a 30 x 30 m area. The area is immediately underlain by flat-lying thick-bedded dolostones of Middle-Silurian age. Six of the boreholes were drilled at angle of 45[degree] to intersect two vertical fracture sets oriented at 020[degree] and 110[degree] which were identified by mapping the fractures in the quarry. Detailed hydraulic tests (constant-head method) were conducted in each of the boreholes using a packer spacing of 0.5 m to determine the hydraulic properties of the individual horizontal and vertical fractures and fracture zones. In addition, four pumping tests were conducted in which a fracture zone in one of the vertical boreholes was shut-in and pumped and the hydraulic response was monitored in the observation boreholes using pressure transducer installed in 15 intervals isolated with multiple-packer strings. The results of the constant-head tests show that although the groundwater flow system in the dolostone is dominated by 3--4 horizontal fracture zones, the average permeability of the vertical fractures is only one order of magnitude less than the average permeability of the horizontal fractures. However, this aspect of the flow system is not detected using pumping tests, the results of which suggest that the average permeability is 3--4 orders of magnitude less in the vertical direction.

  2. Particle velocity based universal algorithm for numerical simulation of hydraulic fractures

    E-print Network

    Wrobel, Michal

    2014-01-01

    In the paper, we propose a new effective mathematical formulation and resulting universal numerical algorithm capable of tackling various HF models in the framework of a unified approach. The presented numerical scheme is not limited to any particular elasticity model or crack propagation regime. Its basic assumptions are: i) proper choice of independent and dependent variables (with the direct utilization of a new one - the reduced particle velocity), ii) tracing the fracture front by use of the speed equation which can be integrated in a closed form and sets an explicit relation between the crack propagation speed and the coefficients in the asymptotic expansion of the crack opening, iii) proper regularization techniques, iv) improved temporal approximation, v) modular algorithm architecture. The application of the new dependent variable, the reduced particle velocity, instead of the usual fluid flow rate, facilitates the computation of the crack propagation speed from the local relation based on the speed ...

  3. Microbial mats as a biological treatment approach for saline wastewaters: the case of produced water from hydraulic fracturing.

    PubMed

    Akyon, Benay; Stachler, Elyse; Wei, Na; Bibby, Kyle

    2015-05-19

    Treatment of produced water, i.e. wastewater from hydraulic fracturing, for reuse or final disposal is challenged by both high salinity and the presence of organic compounds. Organic compounds in produced water may foul physical-chemical treatment processes or support microbial corrosion, fouling, and sulfide release. Biological approaches have potential applications in produced water treatment, including reducing fouling of physical-chemical treatment processes and decreasing biological activity during produced water holding; however, conventional activated sludge treatments are intolerant of high salinity. In this study, a biofilm treatment approach using constructed microbial mats was evaluated for biodegradation performance, microbial community structure, and metabolic potential in both simulated and real produced water. Results demonstrated that engineered microbial mats are active at total dissolved solids (TDS) concentrations up to at least 100,000 mg/L, and experiments in real produced water showed a biodegradation capacity of 1.45 mg COD/gramwet-day at a TDS concentration of 91,351 mg/L. Additionally, microbial community and metagenomic analyses revealed an adaptive microbial community that shifted based upon the sample being treated and has the metabolic potential to degrade a wide array of contaminants, suggesting the potential of this approach to treat produced waters with varying composition. PMID:25867284

  4. Integrating Source Apportionment Tracers into a Bottom-up Inventory of Methane Emissions in the Barnett Shale Hydraulic Fracturing Region.

    PubMed

    Townsend-Small, Amy; Marrero, Josette E; Lyon, David R; Simpson, Isobel J; Meinardi, Simone; Blake, Donald R

    2015-07-01

    A growing dependence on natural gas for energy may exacerbate emissions of the greenhouse gas methane (CH4). Identifying fingerprints of these emissions is critical to our understanding of potential impacts. Here, we compare stable isotopic and alkane ratio tracers of natural gas, agricultural, and urban CH4 sources in the Barnett Shale hydraulic fracturing region near Fort Worth, Texas. Thermogenic and biogenic sources were compositionally distinct, and emissions from oil wells were enriched in alkanes and isotopically depleted relative to natural gas wells. Emissions from natural gas production varied in ?(13)C and alkane ratio composition, with ?D-CH4 representing the most consistent tracer of natural gas sources. We integrated our data into a bottom-up inventory of CH4 for the region, resulting in an inventory of ethane (C2H6) sources for comparison to top-down estimates of CH4 and C2H6 emissions. Methane emissions in the Barnett are a complex mixture of urban, agricultural, and fossil fuel sources, which makes source apportionment challenging. For example, spatial heterogeneity in gas composition and high C2H6/CH4 ratios in emissions from conventional oil production add uncertainty to top-down models of source apportionment. Future top-down studies may benefit from the addition of ?D-CH4 to distinguish thermogenic and biogenic sources. PMID:26148556

  5. Estrogen and androgen receptor activities of hydraulic fracturing chemicals and surface and ground water in a drilling-dense region

    USGS Publications Warehouse

    Kassotis, Christopher D.; Tillitt, Donald E.; Davis, J. Wade; Hormann, Anette M.; Nagel, Susan C.

    2014-01-01

    The rapid rise in natural gas extraction using hydraulic fracturing increases the potential for contamination of surface and ground water from chemicals used throughout the process. Hundreds of products containing more than 750 chemicals and components are potentially used throughout the extraction process, including more than 100 known or suspected endocrine-disrupting chemicals. We hypothesized thataselected subset of chemicalsusedin natural gas drilling operationsandalso surface and ground water samples collected in a drilling-dense region of Garfield County, Colorado, would exhibit estrogen and androgen receptor activities. Water samples were collected, solid-phase extracted, and measured for estrogen and androgen receptor activities using reporter gene assays in human cell lines. Of the 39 unique water samples, 89%, 41%, 12%, and 46% exhibited estrogenic, antiestrogenic, androgenic, and antiandrogenic activities, respectively. Testing of a subset of natural gas drilling chemicals revealed novel antiestrogenic, novel antiandrogenic, and limited estrogenic activities. The Colorado River, the drainage basin for this region, exhibited moderate levels of estrogenic, antiestrogenic, and antiandrogenic activities, suggesting that higher localized activity at sites with known natural gas–related spills surrounding the river might be contributing to the multiple receptor activities observed in this water source. The majority of water samples collected from sites in a drilling-dense region of Colorado exhibited more estrogenic, antiestrogenic, or antiandrogenic activities than reference sites with limited nearby drilling operations. Our data suggest that natural gas drilling operationsmayresult in elevated endocrine-disrupting chemical activity in surface and ground water.

  6. Hydraulic fracture model and diagnostics verification at GRI/DOE multi-site projects and tight gas sand program support. Final report, July 28, 1993--February 28, 1997

    SciTech Connect

    Schroeder, J.E.

    1997-12-31

    The Mesaverde Group of the Piceance Basin in western Colorado has been a pilot study area for government-sponsored tight gas sand research for over twenty years. Early production experiments included nuclear stimulations and massive hydraulic fracture treatments. This work culminated in the US Department of Energy (DOE)`s Multiwell Experiment (MWX), a field laboratory designed to study the reservoir and production characteristics of low permeability sands. A key feature of MWX was an infrastructure which included several closely spaced wells that allowed detailed characterization of the reservoir through log and core analysis, and well testing. Interference and tracer tests, as well as the use of fracture diagnostics gave further information on stimulation and production characteristics. Thus, the Multiwell Experiment provided a unique opportunity for identifying the factors affecting production from tight gas sand reservoirs. The purpose of this operation was to support the gathering of field data that may be used to resolve the number of unknowns associated with measuring and modeling the dimensions of hydraulic fractures. Using the close-well infrastructure at the Multiwell Site near Rifle, Colorado, this operation focused primarily on the field design and execution of experiments. The data derived from the experiments were gathered and analyzed by DOE team contractors.

  7. Estimates of hydraulic properties from a one-dimensional numerical model of vertical aquifer-system deformation, Lorenzi site, Las Vegas, Nevada

    USGS Publications Warehouse

    Pavelko, Michael T.

    2004-01-01

    Land subsidence related to aquifer-system compaction and ground-water withdrawals has been occurring in Las Vegas Valley, Nevada, since the 1930's, and by the late 1980's some areas in the valley had subsided more than 5 feet. Since the late 1980's, seasonal artificial-recharge programs have lessened the effects of summertime pumping on aquifer-system compaction, but the long-term trend of compaction continues in places. Since 1994, the U.S. Geological Survey has continuously monitored water-level changes in three piezometers and vertical aquifer-system deformation with a borehole extensometer at the Lorenzi site in Las Vegas, Nevada. A one-dimensional, numerical, ground-water flow model of the aquifer system below the Lorenzi site was developed for the period 1901-2000, to estimate aquitard vertical hydraulic conductivity, aquitard inelastic skeletal specific storage, and aquitard and aquifer elastic skeletal specific storage. Aquifer water-level data were used in the model as the aquifer-system stresses that controlled simulated vertical aquifer-system deformation. Nonlinear-regression methods were used to calibrate the model, utilizing estimated and measured aquifer-system deformation data to minimize a weighted least-squares objective function, and estimate optimal property values. Model results indicate that at the Lorenzi site, aquitard vertical hydraulic conductivity is 3 x 10-6 feet per day, aquitard inelastic skeletal specific storage is 4 x 10-5 per foot, aquitard elastic skeletal specific storage is 5 x 10-6 per foot, and aquifer elastic skeletal specific storage is 3 x 10-7 per foot. Regression statistics indicate that the model and data provided sufficient information to estimate the target properties, the model adequately simulated observed data, and the estimated property values are accurate and unique.

  8. Comparison of alternative representations of hydraulic-conductivity anisotropy in folded fractured-sedimentary rock: modeling groundwater flow in the Shenandoah Valley (USA)

    NASA Astrophysics Data System (ADS)

    Yager, Richard M.; Voss, Clifford I.; Southworth, Scott

    2009-07-01

    A numerical representation that explicitly represents the generalized three-dimensional anisotropy of folded fractured-sedimentary rocks in a groundwater model best reproduces the salient features of the flow system in the Shenandoah Valley, USA. This conclusion results from a comparison of four alternative representations of anisotropy in which the hydraulic-conductivity tensor represents the bedrock structure as (model A) anisotropic with variable strikes and dips, (model B) horizontally anisotropic with a uniform strike, (model C) horizontally anisotropic with variable strikes, and (model D) isotropic. Simulations using the US Geological Survey groundwater flow and transport model SUTRA are based on a representation of hydraulic conductivity that conforms to bedding planes in a three-dimensional structural model of the valley that duplicates the pattern of folded sedimentary rocks. In the most general representation, (model A), the directions of maximum and medium hydraulic conductivity conform to the strike and dip of bedding, respectively, while the minimum hydraulic-conductivity direction is perpendicular to bedding. Model A produced a physically realistic flow system that reflects the underlying bedrock structure, with a flow field that is significantly different from those produced by the other three models.

  9. Comparison of alternative representations of hydraulic-conductivity anisotropy in folded fractured-sedimentary rock: Modeling groundwater flow in the Shenandoah Valley (USA)

    USGS Publications Warehouse

    Yager, R.M.; Voss, C.I.; Southworth, S.

    2009-01-01

    A numerical representation that explicitly represents the generalized three-dimensional anisotropy of folded fractured-sedimentary rocks in a groundwater model best reproduces the salient features of the flow system in the Shenandoah Valley, USA. This conclusion results from a comparison of four alternative representations of anisotropy in which the hydraulic-conductivity tensor represents the bedrock structure as (model A) anisotropic with variable strikes and dips, (model B) horizontally anisotropic with a uniform strike, (model C) horizontally anisotropic with variable strikes, and (model D) isotropic. Simulations using the US Geological Survey groundwater flow and transport model SUTRA are based on a representation of hydraulic conductivity that conforms to bedding planes in a three-dimensional structural model of the valley that duplicates the pattern of folded sedimentary rocks. In the most general representation, (model A), the directions of maximum and medium hydraulic conductivity conform to the strike and dip of bedding, respectively, while the minimum hydraulic-conductivity direction is perpendicular to bedding. Model A produced a physically realistic flow system that reflects the underlying bedrock structure, with a flow field that is significantly different from those produced by the other three models. ?? Springer-Verlag 2009.

  10. Seismological investigation of crack formation in hydraulic rock fracturing experiments and in natural geothermal environments. Progress report, September 1, 1980-August 31, 1981

    SciTech Connect

    Aki, K.

    1981-09-01

    Progress is reported on the following: interpretation of seismic data from hydraulic fracturing experiments at the Fenton Hill Hot Dry Rock Geothermal Site, interpretation of 3-D velocity anomalies in the western US with special attention to geothermal areas, theoretical and observational studies of scattering and attenuation of high-frequency seismic waves, theoretical and observational studies of volcanic tremors in relation to magma transport mechanisms, and deployment and maintenance of 9 event-recorders around Mt. St. Helens. Abstracts of papers submitted for publication are included. (MHR)

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

    SciTech Connect

    Jung, Hun Bok; Carroll, KC; Kabilan, Senthil; Heldebrant, David J.; Hoyt, David W.; Zhong, Lirong; Varga, Tamas; Stephens, Sean A.; Adams, Lexor; Bonneville, Alain; Kuprat, Andrew P.; Fernandez, Carlos A.

    2015-01-01

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

  12. Using Chemicals to Optimize Conformance Control in Fractured Reservoirs

    SciTech Connect

    Seright, Randall; Liang, Jenn-Tai; Schrader, Richard; Hagstrom II, John; Wang, Ying; Kumar, Anand; Wavrik, Kathryn

    2001-09-07

    The objectives of this project are: (1) to develop a capability to predict and optimize the ability of gels to reduce permeability to water more than that to oil or gas, (2) to develop procedures for optimizing blocking agent placement in wells where hydraulic fractures cause channeling problems, and (3) to develop procedures to optimize blocking agent placement in naturally fractured reservoirs. Work was directed at both injection wells and production wells and at vertical, horizontal, and highly deviated wells.

  13. Use of silica-encapsulated Pseudomonas sp. strain NCIB 9816-4 in biodegradation of novel hydrocarbon ring structures found in hydraulic fracturing waters.

    PubMed

    Aukema, Kelly G; Kasinkas, Lisa; Aksan, Alptekin; Wackett, Lawrence P

    2014-08-01

    The most problematic hydrocarbons in hydraulic fracturing (fracking) wastewaters consist of fused, isolated, bridged, and spiro ring systems, and ring systems have been poorly studied with respect to biodegradation, prompting the testing here of six major ring structural subclasses using a well-characterized bacterium and a silica encapsulation system previously shown to enhance biodegradation. The direct biological oxygenation of spiro ring compounds was demonstrated here. These and other hydrocarbon ring compounds have previously been shown to be present in flow-back waters and waters produced from hydraulic fracturing operations. Pseudomonas sp. strain NCIB 9816-4, containing naphthalene dioxygenase, was selected for its broad substrate specificity, and it was demonstrated here to oxidize fundamental ring structures that are common in shale-derived waters but not previously investigated with this or related enzymes. Pseudomonas sp. NCIB 9816-4 was tested here in the presence of a silica encasement, a protocol that has previously been shown to protect bacteria against the extremes of salinity present in fracking wastewaters. These studies demonstrate the degradation of highly hydrophobic compounds by a silica-encapsulated model bacterium, demonstrate what it may not degrade, and contribute to knowledge of the full range of hydrocarbon ring compounds that can be oxidized using Pseudomonas sp. NCIB 9816-4. PMID:24907321

  14. Use of Silica-Encapsulated Pseudomonas sp. Strain NCIB 9816-4 in Biodegradation of Novel Hydrocarbon Ring Structures Found in Hydraulic Fracturing Waters

    PubMed Central

    Aukema, Kelly G.; Kasinkas, Lisa; Aksan, Alptekin

    2014-01-01

    The most problematic hydrocarbons in hydraulic fracturing (fracking) wastewaters consist of fused, isolated, bridged, and spiro ring systems, and ring systems have been poorly studied with respect to biodegradation, prompting the testing here of six major ring structural subclasses using a well-characterized bacterium and a silica encapsulation system previously shown to enhance biodegradation. The direct biological oxygenation of spiro ring compounds was demonstrated here. These and other hydrocarbon ring compounds have previously been shown to be present in flow-back waters and waters produced from hydraulic fracturing operations. Pseudomonas sp. strain NCIB 9816-4, containing naphthalene dioxygenase, was selected for its broad substrate specificity, and it was demonstrated here to oxidize fundamental ring structures that are common in shale-derived waters but not previously investigated with this or related enzymes. Pseudomonas sp. NCIB 9816-4 was tested here in the presence of a silica encasement, a protocol that has previously been shown to protect bacteria against the extremes of salinity present in fracking wastewaters. These studies demonstrate the degradation of highly hydrophobic compounds by a silica-encapsulated model bacterium, demonstrate what it may not degrade, and contribute to knowledge of the full range of hydrocarbon ring compounds that can be oxidized using Pseudomonas sp. NCIB 9816-4. PMID:24907321

  15. Development of the T+M coupled flow-geomechanical simulator to describe fracture propagation and coupled flow-thermal-geomechanical processes in tight/shale gas systems

    SciTech Connect

    Kim, Jihoon; Moridis, George

    2013-05-22

    We developed a hydraulic fracturing simulator by coupling a flow simulator to a geomechanics code, namely T+M simulator. Modeling of the vertical fracture development involves continuous updating of the boundary conditions and of the data connectivity, based on the finite element method for geomechanics. The T+M simulator can model the initial fracture development during the hydraulic fracturing operations, after which the domain description changes from single continuum to double or multiple continua in order to rigorously model both flow and geomechanics for fracture-rock matrix systems. The T+H simulator provides two-way coupling between fluid-heat flow and geomechanics, accounting for thermoporomechanics, treats nonlinear permeability and geomechanical moduli explicitly, and dynamically tracks changes in the fracture(s) and in the pore volume. We also fully accounts for leak-off in all directions during hydraulic fracturing. We first validate the T+M simulator, matching numerical solutions with the analytical solutions for poromechanical effects, static fractures, and fracture propagations. Then, from numerical simulation of various cases of the planar fracture propagation, shear failure can limit the vertical fracture propagation of tensile failure, because of leak-off into the reservoirs. Slow injection causes more leak-off, compared with fast injection, when the same amount of fluid is injected. Changes in initial total stress and contributions of shear effective stress to tensile failure can also affect formation of the fractured areas, and the geomechanical responses are still well-posed.

  16. Fluid leakage through fractures in an impervious caprock embedded between two geologic aquifers

    NASA Astrophysics Data System (ADS)

    Selvadurai, A. P. S.

    2012-06-01

    The paper develops an analytical result for the flow through a single fracture under a hydraulic gradient between the two aquifer regions and takes into account permeability characteristics of all components of the system. Non-dimensional results are presented to illustrate the influence of the permeability mis-match between the two geologic formations and the permeability and geometry of the fracture on the flow rate through the fracture. The analytical result is then used to develop additional results for leakage through a swarm of vertically aligned hydraulically non-interacting fractures and a damaged region containing a densely spaced array of vertically aligned fractures and worm hole type features in the caprock. The work presents a convenient result for the estimation of leakage from storage formations in geoenvironmental applications.

  17. 77 FR 50505 - Science Advisory Board Staff Office Request for Nominations of Experts for the SAB Hydraulic...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-21

    ...for Nominations of Experts for the SAB Hydraulic Fracturing Advisory Panel AGENCY: Environmental...chartered SAB on EPA's research related to hydraulic fracturing. DATES: Nominations should...protection issues that may be associated with hydraulic fracturing should be directed to...

  18. 75 FR 42087 - Science Advisory Board Staff Office; Request for Nominations of Experts for the SAB Hydraulic...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-20

    ...for Nominations of Experts for the SAB Hydraulic Fracturing Review Panel AGENCY: Environmental...Ad Hoc Panel to review EPA's draft Hydraulic Fracturing Study Plan to investigate...research issues that may be associated with hydraulic fracturing. DATES: Nominations...

  19. How Deep is the Critical Zone: A Scientific Question with Potential Impact For Decision-makers in Areas of Shale-Gas Development and Hydraulic Fracturing

    NASA Astrophysics Data System (ADS)

    Brantley, S. L.

    2014-12-01

    Citizens living in areas of shale-gas development such as the Marcellus gas play in Pennsylvania and surrounding states are cognizant of the possibility that drilling and production of natural gas -- including hydraulic fracturing -- may have environmental impacts on their water. The Critical Zone is defined as the zone from vegetation canopy to the lower limits of groundwater. This definition is nebulous in terms of the lower limit, and yet, defining the bottom of the Critical Zone is important if citizens are to embrace shale-gas development. This is because, although no peer-reviewed study has been presented that documents a case where hydraulic fracturing or formation fluids have migrated upwards from fracturing depths to drinking water resources, a few cases of such leakage have been alleged. On the other hand, many cases of methane migration into aquifers have been documented to occur and some have been attributed to shale-gas development. The Critical Zone science community has a role to play in understanding such contamination problems, how they unfold, and how they should be ameliorated. For example, one big effort of the Critical Zone science community is to promote sharing of data describing the environment. This data effort has been extended to provide data for citizens to understand water quality by a team known as the Shale Network. As scientists learn to publish data online, these efforts must also be made accessible to non-scientists. As citizens access the data, the demand for data will grow and all branches of government will eventually respond by providing more accessible data that will help the public and policy-makers make decisions.

  20. Spatial variability of streambed vertical hydraulic conductivity and its relation to distinctive stream morphologies in the Beiluo River, Shaanxi Province, China

    NASA Astrophysics Data System (ADS)

    Jiang, Weiwei; Song, Jinxi; Zhang, Junlong; Wang, Yuanyuan; Zhang, Nan; Zhang, Xinhua; Long, Yongqing; Li, Jiaxuan; Yang, Xiaogang

    2015-11-01

    Streambed vertical hydraulic conductivity ( K v) is a key parameter in the analysis of interactions between streams and aquifers, and of stream ecosystems. However, knowledge of the streambed hydraulic conductivity associated with different stream morphologies is relatively scarce. An in-situ standpipe permeameter test method was used to determine the spatial variability in streambed K v measured along 18.5 km of stream reach in the Beiluo River, Shaanxi Province, China. The 59 total measurements were conducted at four test sites in three different stream morphologies: straight channel, anabranching channels and a nearby meander bend. There was great spatial variability in K v among the four test sites and three K v distribution patterns can be determined: (1) higher K v values appear on the erosional bank in contrast to lower K v values on the depositional bank at the two sites near meander bends; (2) the K v distribution in straight channels shows that the higher K v values occur in the center of the channel; (3) the K v values are generally highest on the branch with more alluvial forms in the anabranching channels. Moreover, grain-size analysis results illustrate that the average grain-size distributions of streambed sediments are significantly different on each side of the channel. The erosional and depositional forms are one of the driving dynamics for the distribution of streambed grain size that trigger the differences in the distribution of the K v.