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Sample records for hydraulic fracturing experiment

  1. Monitoring hydraulic fracture growth: Laboratory experiments

    SciTech Connect

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

    2000-04-01

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

  2. 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

  3. 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.

  4. Hydraulic fracturing-1

    SciTech Connect

    Not Available

    1990-01-01

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

  5. Calculation Method and Distribution Characteristics of Fracture Hydraulic Aperture from Field Experiments in Fractured Granite Area

    NASA Astrophysics Data System (ADS)

    Cao, Yang-Bing; Feng, Xia-Ting; Yan, E.-Chuan; Chen, Gang; Lü, Fei-fei; Ji, Hui-bin; Song, Kuang-Yin

    2016-05-01

    Knowledge of the fracture hydraulic aperture and its relation to the mechanical aperture and normal stress is urgently needed in engineering construction and analytical research at the engineering field scale. A new method based on the in situ borehole camera measurement and borehole water-pressure test is proposed for the calculation of the fracture hydraulic aperture. This method comprises six steps. The first step is to obtain the equivalent hydraulic conductivity of the test section from borehole water-pressure tests. The second step is a tentative calculation to obtain the qualitative relation between the reduction coefficient and the mechanical aperture obtained from borehole camera measurements. The third step is to choose the preliminary reduction coefficient for obtaining the initial hydraulic aperture. The remaining three steps are to optimize, using the genetic algorithm, the hydraulic apertures of fractures with high uncertainty. The method is then applied to a fractured granite engineering area whose purpose is the construction of an underground water-sealed storage cavern for liquefied petroleum gas. The probability distribution characteristics of the hydraulic aperture, the relationship between the hydraulic aperture and the mechanical aperture, the hydraulic aperture and the normal stress, and the differences between altered fractures and fresh fractures are all analyzed. Based on the effects of the engineering applications, the method is proved to be feasible and reliable. More importantly, the results of the hydraulic aperture obtained in this paper are different from those results elicited from laboratory tests, and the reasons are discussed in the paper.

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

    NASA Astrophysics Data System (ADS)

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

    1993-04-01

    Field values of horizontal hydraulic conductivity measured in the upper 1.5-5.5 m of a weathered and fractured clay-rich till were strongly influenced by smearing around piezometer intakes, which occurs during augering, and by the physical scale of the measuring device. Values measured in conventional augered piezometers were typically 1-2 orders of magnitude lower than those measured in piezometers designed to reduce smearing. Measurements of hydraulic conductivity in small-scale seepage collectors or piezometers, which typically intersect fewer than 10 fractures, vary over a much greater range, 10-10 to 10-6 m/s, than large-scale values based on infiltration into 5.5-m-deep trenches which intersect thousands of fractures (range 10-7 to 3×10-7 m/s). Values of hydraulic fracture aperture, 1-43 μm, and fracture porosity, 3×10-5 to 2×10-3, were calculated using the cubic law with fracture orientation/distribution measurements and the small-scale hydraulic conductivity measurements. This paper provides the first reliable determination of the magnitude and spatial distribution of hydraulically derived fracture parameters in a clay deposit. The absence of such data has, until now, severely limited the application of quantitative groundwater flow and contaminant transport models in this type of deposit.

  7. Hydraulic Fracture Growth in a Layered Formation based on Fracturing Experiments and Discrete Element Modeling

    NASA Astrophysics Data System (ADS)

    Yushi, Zou; Xinfang, Ma; Tong, Zhou; Ning, Li; Ming, Chen; Sihai, Li; Yinuo, Zhang; Han, Li

    2017-09-01

    Hydraulic fracture (HF) height containment tends to occur in layered formations, and it significantly influences the entire HF geometry or the stimulated reservoir volume. This study aims to explore the influence of preexisting bedding planes (BPs) on the HF height growth in layered formations. Laboratory fracturing experiments were performed to confirm the occurrence of HF height containment in natural shale that contains multiple weak and high-permeability BPs under triaxial stresses. Numerical simulations were then conducted to further illustrate the manner in which vertical stress, BP permeability, BP density(or spacing), pump rate, and fluid viscosity control HF height growth using a 3D discrete element method-based fracturing model. In this model, the rock matrix was considered transversely isotropic and multiple BPs can be explicitly represented. Experimental and numerical results show that the vertically growing HF tends to be limited by multi-high-permeability BPs, even under higher vertical stress. When the vertically growing HF intersects with the multi-high-permeability BPs, the injection pressure will be sharply reduced. If a low pumping rate or a low-viscosity fluid is used, the excess fracturing fluid leak-off into the BPs obviously decreases the rate of pressure build up, which will then limit the growth of HF. Otherwise, a higher pumping rate and/or a higher viscosity will reduce the leak-off time and fluid volume, but increase the injection pressure to drive the HF to grow and to penetrate through the BPs.

  8. Passive seismic monitoring of hydraulic fracture experiments at the Multiwell Experiment site

    SciTech Connect

    Thorne, B.J.; Morris, H.E.

    1988-08-01

    Redesign of hardware, software, and data-reduction techniques associated with the Sandia National Laboratories' Borehole Seismic System (BSS) have made possible better estimates of hydraulic fracture geometry at the Multiwell Experiment (MWX) site. The redesigned system now incorporates four geophones per axis and provides up to 112 dB of downhole gain, for 100 times the sensitivity of the original system. Improved signal-to-noise ratios, extended frequency response and increased digitization rates have made possible the acquisition and processing of data which were previously inaccessible. A maximum likelihood event location scheme, which incorporates an algorithm based on the use of spherical statistics, is used to compute the location of microseismic events and error estimates for these locations. Accuracy estimates for the redesigned system, based on the ability to locate perforation shots, indicates a 25 ft (7.6 m) uncertainty in the location of individual microseismic events using data from two BSS receivers. This resulted in a high level of confidence in determination of the azimuth of the November 1, 1986, hydraulic fracture in the Fluvial B sandstone. A reasonable determination of the azimuth, propped wing length and height for the September 23, 1987, hydraulic fracture in the Fluvial E sandstone was possible using data from only one BSS receiver. 15 refs., 32 figs., 6 tabs.

  9. Hydraulic Fracturing Fluid Reaction with Shale in Experiments at Unconventional Gas Reservoir Conditions

    NASA Astrophysics Data System (ADS)

    Paukert, A. N.; Hakala, A.; Jarvis, K. B.

    2015-12-01

    Despite the marked increase in hydraulic fracturing for unconventional natural gas production over the past decade, reactions between hydraulic fracturing fluids (HFF) and shale reservoirs remain poorly reported in the scientific literature. Shale-HFF interaction could cause mineral dissolution, releasing matter from the shale, or mineral precipitation that degrades reservoir permeability. Furthermore, data are limited on whether scale inhibitors are effective at preventing mineral precipitation and whether these inhibitors adversely affect reservoir fluid chemistry and permeability. To investigate HFF-rock interaction within shale reservoirs, we conducted flow-through experiments exposing Marcellus Shale to synthetic HFF at reservoir conditions (66oC, 20MPa). Outcrop shale samples were cored, artificially fractured, and propped open with quartz sand. Synthetic HFFs were mixed with chemical additives similar to those used for Marcellus Shale gas wells in Ohio and Southwestern Pennsylvania (FracFocus.org). We evaluated differences between shale reactions with HFF made from natural freshwater and reactions with HFF made from synthetic produced water (designed to simulate produced water that is diluted and re-used for subsequent hydraulic fracturing). We also compared reactions with HFFs including hydrochloric acid (HCl) to represent the initial acid stage, and HFFs excluding HCl. Reactions were determined through changes in fluid chemistry and X-ray CT and SEM imaging of the shale before and after experiments. Results from experiments with HFF containing HCl showed dissolution of primary calcite, as expected. Experiments using HFF made from synthetic produced water had significant mineral precipitation, particularly of barium and calcium sulfates. X-ray CT images from these experiments indicate precipitation of minerals occurred either along the main fracture or within smaller splay fractures, depending on fluid composition. These experiments suggest that HFF

  10. Mechanics of Hydraulic Fractures

    NASA Astrophysics Data System (ADS)

    Detournay, Emmanuel

    2016-01-01

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

  11. Characterization of Rock Failure for Longmaxi Shale During the Hydraulic Fracturing Experiment

    NASA Astrophysics Data System (ADS)

    Zhai, H.; Xu, C.; Wang, Y.; Xue, Z.; Lei, X.; Zhang, Y.

    2016-12-01

    With the development of unconventional oil gas resources, hydraulic fracturing technology has been widely used in the procedure of shale gas exploration. But the inversion results cannot be verified precisely because we were not able to obtain the accurate images about the distribution of fractures after hydraulic fracturing. Therefore, this paper mainly focuses on the hydraulic fracturing experiment about the shale rock. Comparing the location of the acoustic emission with CT images of rock sample and analyzing the failure mechanism of different AE, we can understand the rupture procedure more specifically and deeply. According to the loading stress log, we can identify that hundreds of acoustic emission were recorded when the confining pressure and axial pressure is less than 7MPa and 35MPa separately. Then we utilized the double difference method to inverse the position of every event. After analyzing the location of all acoustic events, we found most of the events were concentrated in the center of the sample. As shown in the following figure, different colors represent the different threshold for each of the event. Moreover, the larger the threshold is, the more accurate the locating result will be. According to the comparison between distribution of acoustic emission and the generated fractures in the sample, we speculate that the events were probably induced by the reopening or sliding of the main fracture, which was through the whole sample along the diagonal direction. Meanwhile, he activities of some secondary fractures also generated a few of events with lower threshold value. Moreover, the inversion result of rupture mechanism indicates the fractures mainly had a slipping, reopening or reclosing movement. According to the distribution relationship between the acoustic emissions and fractures, we can conclude that the induced events were determined by the reactivation of the fractures, especially when the loading pressure rapidly decreases. However, we

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  13. 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.

  14. The Process of Hydraulic Fracturing

    EPA Pesticide Factsheets

    Hydraulic fracturing, know as fracking or hydrofracking, produces fractures in a rock formation by pumping fluids (water, proppant, and chemical additives) at high pressure down a wellbore. These fractures stimulate the flow of natural gas or oil.

  15. A Hydraulic Tomography Experiment in Fractured Sedimentary Rocks, Newark Basin, New Jersey, USA

    NASA Astrophysics Data System (ADS)

    Tiedeman, C. R.; Barrash, W.; Thrash, C. J.; Johnson, C. D.

    2015-12-01

    Hydraulic tomography was performed in July 2015 in contaminated fractured mudstone beds at the former Naval Air Warfare Center (NAWC) in the Newark Basin near Trenton, NJ using seven existing wells. The spatial arrangement of wells (in a circle of 9 m radius with one central well), the use of packers to divide the wells into multiple monitoring intervals, and the deployment of fiber optic pressure transducers enabled collection of a hydraulic tomography dataset comprising high-resolution drawdown observations at an unprecedented level of spatial detail for fractured rocks. The experiment involved 45-minute cross-hole aquifer tests, conducted by pumping from a given packer-isolated well interval and continuously monitoring drawdowns in all other well intervals. The collective set of drawdown data from all tests and intervals displays a wide range of behavior suggestive of highly heterogeneous hydraulic conductivity (K) within the tested volume, such as: drawdown curves for different well intervals crossing one another on drawdown-time plots; variable drawdown curve shapes, including linear segments on log-log plots; variable order and magnitude of time-lag and/or drawdown for intervals of a given well in response to pumping from similar fractures or stratigraphic units in different wells; and variable groupings of wells and intervals showing similar responses for different pumping tests. The observed behavior is consistent with previous testing at the NAWC indicating that K within and across individual mudstone beds can vary by orders of magnitude over scales of meters. Preliminary assessment of the drawdown data together with a rich set of geophysical logs suggests an initial conceptual model that includes densely distributed fractures of moderate K at the shallowest depths of the tested volume, connected high-K bedding-plane-parting fractures at intermediate depths, and sparse low-K fractures in the deeper rocks. Future work will involve tomographic inversion of

  16. 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

  17. 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.

  18. Discussion of comparison study of hydraulic fracturing models -- Test case: GRI Staged Field Experiment No. 3

    SciTech Connect

    Cleary, M.P.

    1994-02-01

    This paper provides comments to a companion journal paper on predictive modeling of hydraulic fracturing patterns (N.R. Warpinski et. al., 1994). The former paper was designed to compare various modeling methods to demonstrate the most accurate methods under various geologic constraints. The comments of this paper are centered around potential deficiencies in the former authors paper which include: limited actual comparisons offered between models, the issues of matching predictive data with that from related field operations was lacking or undocumented, and the relevance/impact of accurate modeling on the overall hydraulic fracturing cost and production.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

  1. 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.

  2. The Geothermic Fatigue Hydraulic Fracturing Experiment in Äspö Hard Rock Laboratory, Sweden: New Insights Into Fracture Process through In-situ AE Monitoring

    NASA Astrophysics Data System (ADS)

    Kwiatek, G.; Plenkers, K.; Zang, A.; Stephansson, O.; Stenberg, L.

    2016-12-01

    The geothermic Fatigue Hydraulic Fracturing (FHF) in situ experiment (Nova project 54-14-1) took place in the Äspö Hard Rock Laboratory/Sweden in a 1.8 Ma old granitic to dioritic rock mass. The experiment aims at optimizing geothermal heat exchange in crystalline rock mass by multistage hydraulic fracturing at 10 m scale. Six fractures are driven by three different water injection schemes (continuous, cyclic, pulse pressurization) inside a 28 m long, horizontal borehole at depth level 410 m. The rock volume subject to hydraulic fracturing and monitored by three different networks with acoustic emission (AE), micro-seismicity and electromagnetic sensors is about 30 m x 30 m x 30 m in size. The 16-channel In-situ AE monitoring network by GMuG monitored the rupture generation and propagation in the frequency range 1000 Hz to 100,000 Hz corresponding to rupture dimensions from cm- to dm-scale. The in-situ AE monitoring system detected and analyzed AE activity in-situ (P- and S-wave picking, localization). The results were used to review the ongoing microfracturing activity in near real-time. The in-situ AE monitoring network successfully recorded and localized 196 seismic events for most, but not all, hydraulic fractures. All AE events detected in-situ occurred during fracturing time periods. The source parameters (fracture sizes, moment magnitudes, static stress drop) of AE events framing injection periods were calculated using the combined spectral fitting/spectra ratio techniques. The AE activity is clustered in space and clearly outline the fractures location, its orientation, and expansion as well as their temporal evolution. The outward migration of AE events away from the borehole is observed. Fractures extend up to 7 m from the injection interval in the horizontal borehole. The fractures orientation and location correlate for most fractures roughly with the results gained by image packer. Clear differences in seismic response between hydraulic fractures in

  3. Complex Fluids and Hydraulic Fracturing.

    PubMed

    Barbati, Alexander C; Desroches, Jean; Robisson, Agathe; McKinley, Gareth H

    2016-06-07

    Nearly 70 years old, hydraulic fracturing is a core technique for stimulating hydrocarbon production in a majority of oil and gas reservoirs. Complex fluids are implemented in nearly every step of the fracturing process, most significantly to generate and sustain fractures and transport and distribute proppant particles during and following fluid injection. An extremely wide range of complex fluids are used: naturally occurring polysaccharide and synthetic polymer solutions, aqueous physical and chemical gels, organic gels, micellar surfactant solutions, emulsions, and foams. These fluids are loaded over a wide range of concentrations with particles of varying sizes and aspect ratios and are subjected to extreme mechanical and environmental conditions. We describe the settings of hydraulic fracturing (framed by geology), fracturing mechanics and physics, and the critical role that non-Newtonian fluid dynamics and complex fluids play in the hydraulic fracturing process.

  4. Diesel Fuels Hydraulic Fracturing (DFHF)

    EPA Pesticide Factsheets

    This webpage provides information on how hydraulic fracturing is regulated by the Underground Injection Control Program. It includes information about what owners and operators need to do to be in compliance and guidance for EPA Class II permit writers.

  5. Source Characterization of Micro-seismicity Induced by Hydraulic Fracturing Experiment in Taft, California

    NASA Astrophysics Data System (ADS)

    Smith, Trevor Lee

    Understanding the fracture networks created during hydraulic fracture (HF) stimulations in petroleum reservoirs is of high importance for the oil industry because it addresses both: optimization of production for maximum profit as well as safety concerns related to new regulations and the public interest. The fracture network is inferred from the locations of micro-seismic events induced by the hydraulic injections. It has been previously reported that the HF induced seismicity and natural earthquakes have different seismological characteristics. First, the magnitude and total number of natural earthquakes in a given region and time period often follow the Gutenberg-Richter (GR) law (log10N=a-bM, b 1, Gutenberg and Richter, 1956). Recent studies have reported that the HF induced seismicity deviates from the GR law with b values significantly different than one (0.3 < b < 2.5) (El-Isa and Eaton, 2014). However, it is not conclusive yet if these deviations from the GR law are caused by an incomplete catalog or if the HF induced seismicity follows a different power law, distinguishing it from normal seismicity. Second, it has been proposed that HF induced seismicity has much smaller stress drop in compared with natural earthquakes because the injected fluid acts as lubricant (Urbancic et al., 1993; Goertz-Allmann et al., 2011). In this study, we attempt to evaluate these two hypotheses by analyzing a high quality borehole dataset of seismicity induced by a HF experiment in Taft, California, 8 km away from San Andreas Fault. Using the industry catalog, the magnitude frequency distribution (MFD) of induced seismicity occurring in three HF stages indeed has an abnormally high b-value of 2.6. We have applied a newly developed method based on waveform (WF) correlation, Match & Locate (M&L, Zhang and Wen, 2015), to improve the ability to detect smaller events as well as resolve their locations in a noisy environment. We show that this M&L algorithm is able to reduce the

  6. Laboratory Hydraulic Fracture in Shale

    NASA Astrophysics Data System (ADS)

    Roshankhah, S.; Andrade, J.; Ando, E.; Viggiani, C.

    2016-12-01

    The propagation pattern of hydraulic fracture in physical models of rocks has been monitored in previous studies using various non-destructive testing methods such as X-ray radiography (or tomography). The X-ray imaging technique, however, is able to capture only the fracture geometry in the solid rock structure because it is not sensitive to low density materials like liquids. Therefore, liquid flow phenomena (diffusion, dissolution-precipitation, viscous fingering, etc.) through the porous matrix, the generated hydraulic fractures, and the pre-existing joints, and their effects on the evolution of rocks mechanical and hydraulic properties are not well understood yet. In this study, we use simultaneous N-ray and X-ray radiographies as two complementary high resolution process monitoring techniques to directly investigate the characteristics of fracture growth and involved fluid flow phenomena while water-saturated Marcellus shale specimens (K=4.5×10-20 m2, σt=17 MPa) are hydraulically fractured under various initial and boundary conditions (varying stress level, liquid viscosity, and borehole radius). We designed and built an experimental apparatus to investigate hydraulic fracturing in shale specimens subjected to vertical loads equivalent to the overburden stress of 3 km depth. Results show for the first time the intimate interaction between mechanical deformation (fracture) and non-Newtonian fluid flow at conditions representative to those in the field. The experimental device is capable of simulating hydraulic fracture processes in the laboratory and could shed new light into the physics of this important process.

  7. 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.

  8. Inhibition of Biodegradation of Hydraulic Fracturing Compounds by Glutaraldehyde: Groundwater Column and Microcosm Experiments.

    PubMed

    Rogers, Jessica D; Ferrer, Imma; Tummings, Shantal S; Bielefeldt, Angela R; Ryan, Joseph N

    2017-09-05

    The rapid expansion of unconventional oil and gas development has raised concerns about the potential contamination of aquifers; however, the groundwater fate and transport of hydraulic fracturing fluid compounds and mixtures remains a significant data gap. Degradation kinetics of five hydraulic fracturing compounds (2-propanol, ethylene glycol, propargyl alcohol, 2-butoxyethanol, and 2-ethylhexanol) in the absence and presence of the biocide glutaraldehyde were investigated under a range of redox conditions using sediment-groundwater microcosms and flow-through columns. Microcosms were used to elucidate biodegradation inhibition at varying glutaraldehyde concentrations. In the absence of glutaraldehyde, half-lives ranged from 13 d to >93 d. Accurate mass spectrometry indicated that a trimer was the dominant aqueous-phase glutaraldehyde species. Microbial inhibition was observed at glutaraldehyde trimer concentrations as low as 5 mg L(-1), which demonstrated that the trimer retained some biocidal activity. For most of the compounds, biodegradation rates slowed with increasing glutaraldehyde concentrations. For many of the compounds, degradation was faster in the columns than the microcosms. Four compounds (2-propanol, ethylene glycol, propargyl alcohol, and 2-butoxyethanol) were found to be both mobile and persistent in groundwater under a range of redox conditions. The glutaraldehyde trimer and 2-ethylhexanol were more rapidly degraded, particularly under oxic conditions.

  9. Method for directional hydraulic fracturing

    DOEpatents

    Swanson, David E.; Daly, Daniel W.

    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.

  10. Laboratory Visualization of Hydraulic Fracture Propagation and Interaction with a Network of Preexisting Fractures

    NASA Astrophysics Data System (ADS)

    Nakagawa, S.; Kneafsey, T. J.; Borglin, S. E.

    2015-12-01

    We present optical visualization experiments of hydraulic fracture propagation within transparent rock-analogue samples containing a network of preexisting fractures. Natural fractures and heterogeneities in rock have a great impact on hydraulic fracture propagation and resulting improvements in reservoir permeability. In recent years, many sophisticated numerical simulations on hydraulic fracturing have been conducted. Laboratory experiments on hydraulic fracturing are often performed with acoustic emission (Micro Earthquake) monitoring, which allows detection and location of fracturing and fracture propagation. However, the detected fractures are not necessarily hydraulically produced fractures which provide permeable pathways connected to the injection (and production) well. The primary objectives of our visualization experiments are (1) to obtain quantitative visual information of hydraulic fracture propagation affected by pre-existing fractures and (2) to distinguish fractures activated by the perturbed stress field away from the injected fluid and hydraulically produced fractures. The obtained data are also used to develop and validate a new numerical modeling technique (TOUGH-RBSN [Rigid-Body-Spring-Network] model) for hydraulic fracturing simulations, which is presented in a companion paper. The experiments are conducted using transparent soda-lime glass cubes (10 cm × 10 cm × 10 cm) containing either (1) 3D laser-engraved artificial fractures and fracture networks or (2) a random network of fractures produced by rapid thermal quenching. The strength (and also the permeability for the latter) of the fractures can be altered to examine their impact on hydraulic fracturing. The cubes are subjected to true-triaxial stress within a polyaxial loading frame, and hydraulic fractures are produced by injecting fluids with a range of viscosity into an analogue borehole drilled in the sample. The visual images of developing fractures are obtained both through a port

  11. 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.

  12. Hydraulic fracturing system and method

    DOEpatents

    Ciezobka, Jordan; Salehi, Iraj

    2017-02-28

    A hydraulic fracturing system and method for enhancing effective permeability of earth formations to increase hydrocarbon production, enhance operation efficiency by reducing fluid entry friction due to tortuosity and perforation, and to open perforations that are either unopened or not effective using traditional techniques, by varying a pump rate and/or a flow rate to a wellbore.

  13. Hydraulic Properties of Fractured Rock Samples at In-Situ Conditions - Insights from Lab Experiments Using X-Ray Tomography

    NASA Astrophysics Data System (ADS)

    Nehler, Mathias; Stöckhert, Ferdinand; Duda, Mandy; Renner, Jörg; Bracke, Rolf

    2017-04-01

    The hydraulic properties of low-porosity rock formations are controlled by the geometry of open fractures, joints and faults. Aperture, surface roughness, accessible length, and thus, the volume available for fluids associated of such interfaces are strongly affected by their state of stress. Moreover, these properties may evolve with time in particular due to processes involving chemically active fluids. Understanding the physico-chemical interactions of rocks with fluids at reservoir conditions will help to predict the long-term reservoir development and to increase the efficiency of geothermal power plants. We designed an x-ray transparent flow-through cell. Confining pressure can be up to 50 MPa and pore fluid can currently be circulated through the sample with pressures of up to 25 MPa. All wetted parts are made of PEEK to avoid corrosion when using highly saline fluids. Laboratory experiments were performed to investigate hydraulic properties of fractured low-porosity samples under reservoir conditions while x-rays transmit the sample. The cell is placed inside a µCT scanner with a 225 kV multifocal x-ray tube for high resolution x-ray tomography. Samples measure 10 mm in diameter and 25 mm in length resulting in a voxel resolution of approximately 10 µm. Samples with single natural as well as artificial fractures were subjected to various confining pressures ranging from 2.5 MPa to 25 MPa. At each pressure level, effective permeability was determined from steady-state flow relying on Darcy's law. In addition, a full 3D image was recorded by the µCT scanner to gain information on the fracture aperture and geometry. Subvolumes (400x400x400 voxels) of the images were analyzed to reduce computational cost. The subvolumes were filtered in 3D with an edge preserving non-local means filter. Further quantification algorithms were implemented in Matlab. Segmentation into pore space and minerals was done automatically for all datasets by a peak finder algorithm

  14. Hydraulic conductivity of rock fractures

    SciTech Connect

    Zimmerman, R.W.; Bodvarsson, G.S.

    1994-10-01

    Yucca Mountain, Nevada contains numerous geological units that are highly fractured. A clear understanding of the hydraulic conductivity of fractures has been identified as an important scientific problem that must be addressed during the site characterization process. The problem of the flow of a single-phase fluid through a rough-walled rock fracture is discussed within the context of rigorous fluid mechanics. The derivation of the cubic law is given as the solution to the Navier-Stokes equations for flow between smooth, parallel plates, the only fracture geometry that is amenable to exact treatment. The various geometric and kinetic conditions that are necessary in order for the Navier-Stokes equations to be replaced by the more tractable lubrication or Hele-Shaw equations are studied and quantified. Various analytical and numerical results are reviewed pertaining to the problem of relating the effective hydraulic aperture to the statistics of the aperture distribution. These studies all lead to the conclusion that the effective hydraulic aperture is always less than the mean aperture, by a factor that depends on the ratio of the mean value of the aperture to its standard deviation. The tortuosity effect caused by regions where the rock walls are in contact with each other is studied using the Hele-Shaw equations, leading to a simple correction factor that depends on the area fraction occupied by the contact regions. Finally, the predicted hydraulic apertures are compared to measured values for eight data sets from the literature for which aperture and conductivity data were available on the same fracture. It is found that reasonably accurate predictions of hydraulic conductivity can be made based solely on the first two moments of the aperture distribution function, and the proportion of contact area. 68 refs.

  15. Hydraulic Fracturing of Soils; A Literature Review.

    DTIC Science & Technology

    1977-03-01

    best case, or worst case. The study reported herein is an overview of one such test or technique, hydraulic fracturing , which is defined as the...formation of cracks, in soil by the application of hydraulic pressure greater than the minor principal stress at that point. Hydraulic fracturing , as a... hydraulic fracturing as a means for determination of lateral stresses, the technique can still be used for determining in situ total stress and permeability at a point in a cohesive soil.

  16. 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.

  17. Comparison of Hydraulic Methods and Tracer Experiments as Applied to the Development of Conceptual Models for Discrete Fracture Networks

    NASA Astrophysics Data System (ADS)

    Novakowski, K. S.

    2015-12-01

    The development of conceptual models for solute migration in discrete fracture networks has typically been based on a combination of core logs, borehole geophysics, and some form of single-well hydraulic test using discrete zones. More rarely, interwell hydraulic tests and interwell tracer experiments are utilised to directly explore potential transport pathways. The latter methods are less widely employed simply due to potentially significant increases in the cost and effort in site characterization. To date however there is a paucity of literature comparing the efficacy of the standard procedure with what should be more definitive identification of transport pathways using interwell methods. In the present study, a detailed comparison is conducted by developing conceptual models from three separate data sets, the first based on core logs, geology and single-well hydraulic tests, the second based on a large suite of pulse interference tests, and the third based on a series of radially-divergent and injection-withdrawal tracer experiments. The study was conducted in an array of five HQ-sized wells, 28-32 m in depth and arranged in a five star pattern, 10 m on a side. The wells penetrate the contact between a Cambrian-aged limestone, and underlying Precambrian gneiss. The core was logged for potentially open fractures using a ranking system, and 87 contiguous hydraulic tests were conducted using a 0.85-m packer spacing. A total of 57 pulse interference tests were conducted using two wells as injection points, and 11 tracer experiments were conducted using either sample collection or in-situ detection via a submersible fluorometer. The results showed very distinct conceptual models depending on the data set, with the model based on the single-well testing significantly over-predicting the number and connection of solute transport pathways. The results of the pulse interference tests also over predict the transport pathways, but to a lesser degree. Quantification of

  18. 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.

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

    NASA Astrophysics Data System (ADS)

    Pearson, C.

    1982-04-01

    Using source parameters estimated from seismic spectra and magnitudes estimated from coda lengths, we demonstrate that the log-linear relationship between moment and magnitude holds for events with magnitudes as low as -6. Using, as a data set, events induced by hydraulic fracturing experiments at the Fenton Hill, New Mexico, Hot Dry Rock (HDR) geothermal site, we find that the relationship between magnitude M and seismic moment (Mo) is FD1 log(Mo)=17.27+0.77M. Moreover, the linear relationship between seismic moment and source radius (r) holds for the Fenton Hill microearthquakes. Analyses of the Fenton Hill data yield the following relationship. FD2 log(r)=2.28+0.19log(Mo).

  20. Experimental study on hydraulic fracture propagation in Lacustrine Shale

    NASA Astrophysics Data System (ADS)

    Wang, R.; Jiang, G.; Xie, J.; Cheng, W.; Tian, H.

    2016-12-01

    Hydraulic fracturing has become one of the essential techniques for the stimulation of shale gas at present. Lacustrine shale in north of China, has higher clay content compared to marine shale in south of China. Thus, many problems such as high fracturing pressure have sprung up. Consequently, according to the characteristics of shale gas reservoir in Ordos Basin, it is very necessary to develop fracturing technology system for northern lacustrine shale. In order to explore the formation mechanism of the fracture network, a hydraulic fracturing experiment was conducted on the hydraulic fracturing system, which consists of large-scale triaxial module, high pressure injection pump module and AE (acoustic emission) modules. After compared the fracturing results of 13 shale specimens, how hydraulic parameters such as perforation, fracturing fluid leakoff and in-situ stresses affect the geometry of the fracture was analyzed. The results show that: The geometry of the hydraulic fracture is impacted by parameters in different extent, while the perforation is the determining factor. Fractures in the process of propagation will eventually turn to the direction of maximum stress. Low pumping output is propitious to fracturing fluid seepage in the shale specimen, which will benefit forming fracture network.

  1. An Experimental Investigation into the Effects of the Anisotropy of Shale on Hydraulic Fracture Propagation

    NASA Astrophysics Data System (ADS)

    Lin, Chong; He, Jianming; Li, Xiao; Wan, Xiaole; Zheng, Bo

    2017-03-01

    Hydraulic fracturing is a key technology in the exploitation of shale gas. Shale formations are a type of typical transverse isotropic material. The mechanisms that generate complex fracture networks during the fracturing process are of vital importance to hydraulic fracturing design. In this article, in order to analyze the effects of the anisotropic characteristics on the propagation of hydraulic fractures in shale formations, a series of hydraulic fracturing experiments were carried out with different stress conditions and injection rates. The effects of the anisotropic structure on the propagation of hydraulic fractures were revealed. The results show that the breakdown pressure increases with an increase in the injection rate of the fracturing fluid. It is suggested that the bedding plane angle of the shale formation has a great influence on the fracturing results. Additionally, as the deviator stress increases, the breakdown pressure decreases. From macroscopic observation of the fractures, different hydraulic fracture morphologies and hydraulic fracture propagation patterns were observed.

  2. 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

  3. Hydraulic fracture during epithelial stretching

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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 manoeuvres. 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.

  4. Hydraulic fracture during epithelial stretching.

    PubMed

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

    2015-03-01

    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 manoeuvres. 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.

  5. Mixed-mode Mechanism of Hydraulic Fracture Segmentation

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

    Mixed-mode I+III loading is one of the primary causes of fracture front segmentation. Although such segmented fractures have been observed both in nature and laboratory, we are not aware of direct laboratory experiments on the mode III mechanism of segmentation of hydraulically induced fractures. In this work, we developed a laboratory technique and a theoretical model for studying not only the effect of mode III loading on the onset of hydraulic fracture segmentation, but also the effect of segmentation on the subsequent growth of hydraulic fractures. In quasi-brittle materials, even a small mode III component may cause fracture segmentation due to a tensile stress field induced near the fracture front [Rice, 1968]. Previously, this has been confirmed in experiments with non-hydraulic fractures [Knauss, 1970; Cooke and Pollard, 1996]. In one occasion, quasi-hydraulic fractures propagated in fast, uncontrollable manner [Sommer, 1969]. This is why, we focused on controlled hydraulic fractures with a rather small KIII/KI ratio (1-10 %). For mixed mode I+III experiments, we used transparent, cylindrical PMMA samples with circular internal fractures perpendicular to the sample axis. Fracture orientation was controlled by thermoelastic stresses induced in each sample by preheating it before creating a fracture. In order to apply mode III loading to the initial fracture, a constant torque was applied to the specimen while fluid was injected into the fracture at a constant rate to pressurize it and to induce mode I loading. The velocity of fracture propagation was constrained by controlling the rate of fluid injection. In spite of a small magnitude of the mode III component, we observed segmented fracture fronts in all tested samples. The segments had similar dimensions and shape elongated around the perimeter of the initial fracture. When the fractures were further pressurized by injecting additional fluid into the sample, second-order segments developed along the fronts

  6. Discrete modeling of hydraulic fracturing processes in a complex pre-existing fracture network

    NASA Astrophysics Data System (ADS)

    Kim, K.; Rutqvist, J.; Nakagawa, S.; Houseworth, J. E.; Birkholzer, J. T.

    2015-12-01

    Hydraulic fracturing and stimulation of fracture networks are widely used by the energy industry (e.g., shale gas extraction, enhanced geothermal systems) to increase permeability of geological formations. Numerous analytical and numerical models have been developed to help understand and predict the behavior of hydraulically induced fractures. However, many existing models assume simple fracturing scenarios with highly idealized fracture geometries (e.g., propagation of a single fracture with assumed shapes in a homogeneous medium). Modeling hydraulic fracture propagation in the presence of natural fractures and homogeneities can be very challenging because of the complex interactions between fluid, rock matrix, and rock interfaces, as well as the interactions between propagating fractures and pre-existing natural fractures. In this study, the TOUGH-RBSN code for coupled hydro-mechanical modeling is utilized to simulate hydraulic fracture propagation and its interaction with pre-existing fracture networks. The simulation tool combines TOUGH2, a simulator of subsurface multiphase flow and mass transport based on the finite volume approach, with the implementation of a lattice modeling approach for geomechanical and fracture-damage behavior, named Rigid-Body-Spring Network (RBSN). The discrete fracture network (DFN) approach is facilitated in the Voronoi discretization via a fully automated modeling procedure. The numerical program is verified through a simple simulation for single fracture propagation, in which the resulting fracture geometry is compared to an analytical solution for given fracture length and aperture. Subsequently, predictive simulations are conducted for planned laboratory experiments using rock-analogue (soda-lime glass) samples containing a designed, pre-existing fracture network. The results of a preliminary simulation demonstrate selective fracturing and fluid infiltration along the pre-existing fractures, with additional fracturing in part

  7. Relation between mass balance aperture and hydraulic properties from field experiments in fractured rock in Sweden

    NASA Astrophysics Data System (ADS)

    Hjerne, Calle; Nordqvist, Rune

    2014-09-01

    Results from tracer tests are often used to infer connectivity and transport properties in bedrock. However, the amount of site-specific data from tracer tests is often very limited, while data from hydraulic tests are more abundant. It is therefore of great interest for predictive transport modeling to use hydraulic data to infer transport properties. In this study, data from cross-hole tracer tests carried out in crystalline bedrock in Sweden were compiled and analysed. The tests were performed within investigations made by the Swedish Nuclear Fuel and Waste Management Company (SKB) between 1978 and 2009 at five different locations. An empirical relationship between mass balance aperture and transmissivity was found and quantified by using 74 observations. The empirical relationship deviates considerably from the cubic law aperture, as mass balance aperture is found to be at least one order of magnitude larger than cubic law aperture. Hence, usage of cubic law aperture, derived from hydraulic testing, for transport predictions is unsuitable, as the advective transport time will be considerably underestimated. Another result, from the data set studied, is that mass balance aperture appears to correlate better to apparent storativity than to transmissivity.

  8. Impact of Partially Cemented and Non-persistent Natural Fractures on Hydraulic Fracture Propagation

    NASA Astrophysics Data System (ADS)

    Fu, Wei; Ames, Brandon C.; Bunger, Andrew P.; Savitski, Alexei A.

    2016-11-01

    This paper presents laboratory experiments exploring the interaction between hydraulic fractures and preexisting natural fractures that are strongly cemented relative to the host material strength but over only a portion of the natural fracture. Two sets of experiments were conducted, including the central region cemented case and the top-bottom region cemented case. Three main patterns are observed for the interaction between hydraulic fractures and partially cemented natural fractures: (1) complete crossing, (2) crossing with mismatched crack path and (3) no crossing. The results show that a hydraulic fracture penetrates directly through a fully and strongly cemented preexisting natural fracture. When the proportion of the strongly cemented region decreases or the height of the weak natural fracture increases, the hydraulic fracture is observed to persist through the entire height of the specimen both before and after the interface. However, the fracture path proceeds directly through strongly cemented portions while causing mismatched crack path at uncemented portions. No crossing results are obtained when the strongly cemented region is sufficiently small, around 30 % of the natural fracture's height. Results of this seldom considered but almost certainly realistic configuration of partial cementing suggest that the hydraulic fracture path is strongly influenced by the size of the cemented region of the natural fracture.

  9. 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...

  10. 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...

  11. 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

  12. Laboratory Scale Hydraulic Fracture and Proppant Injection

    NASA Astrophysics Data System (ADS)

    Ingraham, M. D.; Rao, R. R.; Bolintineanu, D.; Lechman, J. B.; Bauer, S. J.; Quintana, E.

    2015-12-01

    A series of fracture and proppant injection tests have been conducted on Marcellus shale from an outcrop in Pennsylvania at the laboratory scale. The shale outcrop was recently exposed by new construction and shows little sign of weathering. Specimens 3 inches in diameter and nominally 6 inches long were cored (parallel to bedding) from blocks taken from the outcrop. A 3 inch hole was then cored down the center of the specimen and "cased" with 0.25 inch high pressure tubing, leaving 0.75 inches of space at the bottom of the borehole uncased. Specimens were then loaded under in an axisymmetric extension stress state and hydraulically fractured in order to generate the appropriate fracture orientation to represent the opening of a fracture in a typical long horizontal well, where fractures are "disks on a string." After fracture with water, while still under stress, a guar/proppant mixture was injected into the specimen to investigate the distribution of proppant in the fracture. Silicon carbide particles were used as proppant to assist in proppant visualization in microCT scans performed after the test was completed. Corresponding numerical analyses (using the finite element method) of the flow path and particle transport are underway, coupled with idealized flow experiments to validate the codes being used to model the particle transport. Some of the meshes being used were developed directly from CT scans. 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. SAND2015-6111 A.

  13. Data Analytics of Hydraulic Fracturing Data

    SciTech Connect

    Zhang, Jovan Yang; Viswanathan, Hari; Hyman, Jeffery; Middleton, Richard

    2016-08-11

    These are a set of slides on the data analytics of hydraulic fracturing data. The conclusions from this research are the following: they proposed a permeability evolution as a new mechanism to explain hydraulic fracturing trends; they created a model to include this mechanism and it showed promising results; the paper from this research is ready for submission; they devised a way to identify and sort refractures in order to study their effects, and this paper is currently being written.

  14. 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.

  15. Hydraulic fracturing in tight, fissured media

    SciTech Connect

    Warpinski, N.R. )

    1991-02-01

    Large volumes of natural gas are found in tight, fissured reservoirs. Hydraulic fracturing can enhance recovery, but many complications, such as pressure-sensitive or accelerated leakoff, damage, and complex fracturing, arise during treatment of such reservoirs. This paper reports that special procedures generally should be considered during breakdown and fracturing of these reservoirs. In addition, the use of alternative stimulation strategies may be beneficial.

  16. Where Does Water Go During Hydraulic Fracturing?

    PubMed

    O'Malley, D; Karra, S; Currier, R P; Makedonska, N; Hyman, J D; Viswanathan, H S

    2016-07-01

    During hydraulic fracturing millions of gallons of water are typically injected at high pressure into deep shale formations. This water can be housed in fractures, within the shale matrix, and can potentially migrate beyond the shale formation via fractures and/or faults raising environmental concerns. We describe a generic framework for producing estimates of the volume available in fractures and undamaged shale matrix where water injected into a representative shale site could reside during hydraulic fracturing, and apply it to a representative site that incorporates available field data. The amount of water that can be stored in the fractures is estimated by calculating the volume of all the fractures associated with a discrete fracture network (DFN) based on real data and using probability theory to estimate the volume of smaller fractures that are below the lower cutoff for the fracture radius in the DFN. The amount of water stored in the matrix is estimated utilizing two distinct methods-one using a two-phase model at the pore-scale and the other using a single-phase model at the continuum scale. Based on these calculations, it appears that most of the water resides in the matrix with a lesser amount in the fractures.

  17. Hydraulic-fracture propagation in layered rock: experimental studies of fracture containment

    SciTech Connect

    Teufel, L. W.; Clark, J. A.

    1981-01-01

    Fracture geometry is an important concern in the design of a massive hydraulic fracture treatment for improved natural gas recovery from tight gas sands. Possible prediction of vertical fracture growth and containment in layered rock requires an improved understanding of the parameters which may control fracture growth across layer interfaces. We have conducted laboratory hydraulic fracture experiments and elastic finite element studies which show that at least two distinct geologic conditions may inhibit or contain the vertical growth of hydraulic fractures in layered rock; (1) a weak interfacial shear strength of the layers and (2) a compressional increase in the minimum horizontal stress in the bounding layer. The second condition is more important and more likely to occur at depth. Variations in the horizontal stress can result from differences in elastic properties of individual layers in a layered rock sequence. A compressional increase in the minimum horizontal stress can occur in going from high shear modulus into low shear modulus layers.

  18. Hydraulic fracture propagation modeling and data-based fracture identification

    NASA Astrophysics Data System (ADS)

    Zhou, Jing

    Successful shale gas and tight oil production is enabled by the engineering innovation of horizontal drilling and hydraulic fracturing. Hydraulically induced fractures will most likely deviate from the bi-wing planar pattern and generate complex fracture networks due to mechanical interactions and reservoir heterogeneity, both of which render the conventional fracture simulators insufficient to characterize the fractured reservoir. Moreover, in reservoirs with ultra-low permeability, the natural fractures are widely distributed, which will result in hydraulic fractures branching and merging at the interface and consequently lead to the creation of more complex fracture networks. Thus, developing a reliable hydraulic fracturing simulator, including both mechanical interaction and fluid flow, is critical in maximizing hydrocarbon recovery and optimizing fracture/well design and completion strategy in multistage horizontal wells. A novel fully coupled reservoir flow and geomechanics model based on the dual-lattice system is developed to simulate multiple nonplanar fractures' propagation in both homogeneous and heterogeneous reservoirs with or without pre-existing natural fractures. Initiation, growth, and coalescence of the microcracks will lead to the generation of macroscopic fractures, which is explicitly mimicked by failure and removal of bonds between particles from the discrete element network. This physics-based modeling approach leads to realistic fracture patterns without using the empirical rock failure and fracture propagation criteria required in conventional continuum methods. Based on this model, a sensitivity study is performed to investigate the effects of perforation spacing, in-situ stress anisotropy, rock properties (Young's modulus, Poisson's ratio, and compressive strength), fluid properties, and natural fracture properties on hydraulic fracture propagation. In addition, since reservoirs are buried thousands of feet below the surface, the

  19. Fracturing Experiment 2016

    SciTech Connect

    Brown, Donald W.; Keppler, H.; Kuriyagawa, Michio; Murphy, Hugh D.; Walter, Fritz

    1982-09-27

    Experiment 2016 was conducted on June 20 and 21, 1982. This experiment represented our third attempt at a fracture connection between the bottom of hole EE-2, and the openhole section of EE-3. The primary objective of Experiment 2016 was to hydraulically connect holes EE-2 and EE-3, utilizing a greater amount of injected fluid--1.3 million gallons were pumped into EE-2--and somewhat higher injection rates up to 35 BPM (as compared to 30 BPM during Expt. 2012).

  20. New proppant for deep hydraulic fracturing

    SciTech Connect

    Underdown, D.R.; Das, K.

    1982-01-01

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

  1. Discrete Fracture Network Characterization of Fractured Shale Reservoirs with Implications to Hydraulic Fracturing Optimization

    NASA Astrophysics Data System (ADS)

    Jin, G.

    2016-12-01

    Shales are important petroleum source rocks and reservoir seals. Recent developments in hydraulic fracturing technology have facilitated high gas production rates from shale and have had a strong impact on the U.S. gas supply and markets. Modeling of effective permeability for fractured shale reservoirs has been challenging because the presence of a fracture network significantly alters the reservoir hydrologic properties. Due to the frequent occurrence of fracture networks, it is of vital importance to characterize fracture networks and to investigate how these networks can be used to optimize the hydraulic fracturing. We have conducted basic research on 3-D fracture permeability characterization and compartmentization analyses for fractured shale formations, which takes the advantages of the discrete fracture networks (DFN). The DFN modeling is a stochastic modeling approach using the probabilistic density functions of fractures. Three common scenarios of DFN models have been studied for fracture permeability mapping using our previously proposed techniques. In DFN models with moderately to highly concentrated fractures, there exists a representative element volume (REV) for fracture permeability characterization, which indicates that the fractured reservoirs can be treated as anisotropic homogeneous media. Hydraulic fracturing will be most effective if the orientation of the hydraulic fracture is perpendicular to the mean direction of the fractures. A DFN model with randomized fracture orientations, on the other hand, lacks an REV for fracture characterization. Therefore, a fracture permeability tensor has to be computed from each element. Modeling of fracture interconnectivity indicates that there exists no preferred direction for hydraulic fracturing to be most effective oweing to the interconnected pathways of the fracture network. 3-D fracture permeability mapping has been applied to the Devonian Chattanooga Shale in Alabama and the results suggest that an

  2. Characterizing hydraulically fractured reservoirs using induced microearthquakes

    SciTech Connect

    Fehler, M.

    1991-01-01

    Hydraulic fracturing is a common method employed to increase the production of oil and gas fields. Recently, there has been increased interest in monitoring the microearthquakes induced by hydraulic fracturing as a means of obtaining data to characterize reservoir changeS induced by the injection. Two types of microearthquakes have been observed during hydraulic fracturing. Tensile events have been observed and modeled as the parting of the surfaces of a fracture. A majority of the events observed have been shear-slip events, where two sides of a fault plane slip parallel to each other but in opposite directions. The locations of the microearthquakes can be analyzed to determine regions where significant seismic energy was released, which presumably are regions where injected fluid penetrated into the rock along pre-existing fractures or zones of weakness. The spatial patterns in the locations can be analyzed to fine regions where events cluster along planes, which are interpreted to be the dominant fluid flow paths. Imaging methods can also be applied to the travel time and waveform data to obtain direct evidence for the locations of the fractures or fracture zones. 27 refs., 2 figs.

  3. The Pennsylvania Experience with Hydraulic Fracturing for Shale Gas Development: Relatively Infrequent Water Quality Incidents with Lots of Public Attention

    NASA Astrophysics Data System (ADS)

    Brantley, S. L.; Li, Z.; Yoxtheimer, D.; Vidic, R.

    2015-12-01

    New techniques of hydraulic fracturing - "fracking" - have changed the United States over the last 10 years into a leading producer of natural gas extraction from shale. The first such gas well in Pennsylvania was drilled and completed using high-volume hydraulic fracturing in 2004. By late 2014, more than 8500 of these gas wells had been drilled in the Marcellus Shale gas field in Pennsylvania alone. Almost 1000 public complaints about groundwater quality were logged by the PA Department of Environmental Protection (PA DEP) between 2008 and 2012. Only a fraction of these were attributed to unconventional gas development. The most common problem was gas migration into drinking water, but contamination incidents also included spills, seepage, or leaks of fracking fluids, brine salts, or very occasionally, radioactive species. Many problems of gas migration were from a few counties in the northeastern part of the state. However, sometimes one gas well contaminated multiple water wells. For example, one gas well was reported by the state regulator to have contaminated 18 water wells with methane near Dimock PA. It can be argued that such problems at a relatively small fraction of gas wells initiated pockets of pushback against fracking worldwide. This resistance to fracking has grown even though fracking has been in use in the U.S.A. since the 1940s. We have worked as part of an NSF-funded project (the Shale Network) to share water quality data and publish it online using the CUAHSI Hydrologic Information System. Sharing data has led to collaborative investigation of specific contamination incidents to understand how problems can occur, and to efforts to quantify the frequency of impacts. The Shale Network efforts have also highlighted the need for more transparency with water quality data in the arena related to the energy-water nexus. As more data are released, new techniques of data analysis will allow better understanding of how to tune best practices to be

  4. 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)

  5. Impact of ductility on hydraulic fracturing in shales

    NASA Astrophysics Data System (ADS)

    MacMinn, Chris; Auton, Lucy

    2016-04-01

    Hydraulic fracturing is a method for extracting natural gas and oil from low-permeability rocks such as shale via the high-pressure injection of fluid into the bulk of the rock. The goal is to initiate and propagate fractures that will provide hydraulic access deeper into the reservoir, enabling gas or oil to be collected from a larger region of the rock. Fracture is the tensile failure of a brittle material upon reaching a threshold tensile stress, but some shales have a high clay content and may yield plastically before fracturing. Plastic deformation is the shear failure of a ductile material, during which stress relaxes through irreversible rearrangements of the particles of the material. Here, we investigate the impact of the ductility of shales on hydraulic fracturing. We first consider a simple, axisymmetric model for radially outward fluid injection from a wellbore into a ductile porous rock. We use this model to show that plastic deformation greatly reduces the maximum tensile stress, and that this maximum stress does not always occur at the wellbore. We then complement these results with laboratory experiments in an analogue system, and with numerical simulations based on the discrete element method (DEM), both of which suggest that ductile failure can indeed dramatically change the resulting deformation pattern. These results imply that hydraulic fracturing may fail in ductile rocks, or that the required injection rate for fracking may be much larger than the rate predicted from models that assume purely elastic mechanical behavior.

  6. Interaction between injection points during hydraulic fracturing

    NASA Astrophysics Data System (ADS)

    Hals, Kjetil M. D.; Berre, Inga

    2012-11-01

    We study the geomechanical stress interaction between two injection points during hydraulic fracturing (hydrofracking) and how this interaction in combination with disorder influences the fracturing process. To this end, we develop an effective continuum model of the hydrofracking of heterogeneous poroelastic media 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. For injection points that are separated by less than a critical correlation length, our numerical simulations show 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.

  7. Laboratory imaging of hydraulic fractures using microseismicity

    NASA Astrophysics Data System (ADS)

    Zeng, Zhengwen

    2002-09-01

    This dissertation starts with an investigation of the industry's needs for future research and development of hydraulic fracturing (HF) technology. Based on the investigation results of a questionnaire answered by some industrial experts, it was found that reliable hydraulic fracturing diagnostic techniques are in need. Further critical review showed that the microseismic method was one of the most promising techniques that needed further development. Developing robust algorithms and software for locating the coordinates of hydraulic fracturing-induced microseismic events, and for simulating the first motion of the induced waveforms were central tasks for this research. In addition, initiation and propagation characteristics of asymmetrical hydraulic fractures were investigated; a recent discovered tight gas sandstone was systematically characterized; a method for measuring Mode-I fracture toughness was upgraded; and the packer influence on the initiation of asymmetrical fractures was numerically simulated. By completing this research, the following contributions have been made: (1) Development of a simplex-based microseismic LOCATION program. This program overcame the shortcoming of ill-conditioning-prone conditions encountered in conventional location programs. (2) Development of a variance-based computer program, ArrTime, to automatically search the first arrival times from the full waveform data points. (3) Development of the first motion simulator of the induced microseismic waveforms. Using this program, the first motion waveform amplitude in any direction at any location induced from seismic sources at an arbitrary location in a known fracturing mode can be calculated. (4) Complete characterization of a newly discovered tight gas formation, the Jackfork sandstone. (5) Upgrade of a core sample-based method for the measurement of fracture toughness. Mode-I fracture toughness of common core samples in any direction can be measured using this method. (6) Discern

  8. Mapping of hydraulic fractures from tiltmeter measurements

    NASA Astrophysics Data System (ADS)

    Lecampion, B.; Jeffrey, R.

    2003-12-01

    In considering the problem of inverse modeling of tiltmeter data for hydraulic fracture mapping, we address the issues of selecting the elastic model to represent the hydraulic fracture and limitations imposed by distance and fracture size on the information that can be recovered about the fracture. A tiltmeter measures, at its location, the changes in the surface inclination in two orthogonal directions. These inclinations are a direct measure of the horizontal gradient of the vertical component of the displacement field. Since advances in instrumentation in the last two decades, this type of apparatus have become extremely precise and can detect inclination changes down to a nanoradian. The simplicity of tiltmeter measurements has attracted interest not only in geophysics, but also in the petroleum industry. The idea of using tiltmeters to monitor hydraulic fractures can be traced back to the paper of Sun te{S} and is now a commercial service offered to the petroleum industry te{W}. However, the modeling and associated inverse problems required to analyze tiltmeter data raise difficult questions. The object(s) (fault, dyke, fracture) responsible for the recorded tilt are often modeled by finite Displacement Discontinuities, also called dislocation models. The validity of this type of model has been extensively discussed te{O,E} and many solutions for different configurations can be found in the literature. We show that it is possible to construct the solution for any type of dislocation model from the fundamental solution for an infinitesimal Displacement Discontinuity tensor. The eigenstrain theory te{M} is used to obtain this fundamental solution from the Green's function for the desired elastic domain (e.g. full or half space). Comparisons with known solutions demonstrate the flexibility of such method. We then focus on the problem of obtaining information about the orientation and size of an opening mode hydraulic fracture from the measured tilt field. One

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    Urbancic, T.; Baig, A. M.

    2013-12-01

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

  11. Review of Well Operator Files for Hydraulically Fractured Oil and Gas Production Wells: Hydraulic Fracturing Operations

    EPA Pesticide Factsheets

    EPA conducted a survey of oil and gas production wells hydraulically fractured by nine oil and gas service companies in the United States during 2009 and 2010. This is the second well file review report.

  12. Percolation Theory and Modern Hydraulic Fracturing

    NASA Astrophysics Data System (ADS)

    Norris, J. Q.; Turcotte, D. L.; Rundle, J. B.

    2015-12-01

    During the past few years, we have been developing a percolation model for fracking. This model provides a powerful tool for understanding the growth and properties of the complex fracture networks generated during a modern high volume hydraulic fracture stimulations of tight shale reservoirs. The model can also be used to understand the interaction between the growing fracture network and natural reservoir features such as joint sets and faults. Additionally, the model produces a power-law distribution of bursts which can easily be compared to observed microseismicity.

  13. Triaxial coreflood study of the hydraulic fracturing of Utica Shale

    NASA Astrophysics Data System (ADS)

    Carey, J. W.; Frash, L.; Viswanathan, H. S.

    2015-12-01

    One of the central questions in unconventional oil and gas production research is the cause of limited recovery of hydrocarbon. There are many hypotheses including: 1) inadequate penetration of fractures within the stimulated volume; 2) limited proppant delivery; 3) multiphase flow phenomena that blocks hydrocarbon migration; etc. Underlying any solution to this problem must be an understanding of the hydrologic properties of hydraulically fractured shale. In this study, we conduct triaxial coreflood experiments using a gasket sealing mechanism to characterize hydraulic fracture development and permeability of Utica Shale samples. Our approach also includes fracture propagation with proppants. The triaxial coreflood experiments were conducted with an integrated x-ray tomography system that allows direct observation of fracture development using x-ray video radiography and x-ray computed tomography at elevated pressure. A semi-circular, fracture initiation notch was cut into an end-face of the cylindrical samples (1"-diameter with lengths from 0.375 to 1"). The notch was aligned parallel with the x-ray beam to allow video radiography of fracture growth as a function of injection pressure. The proppants included tungsten powder that provided good x-ray contrast for tracing proppant delivery and distribution within the fracture system. Fractures were propagated at injection pressures in excess of the confining pressure and permeability measurements were made in samples where the fractures propagated through the length of the sample, ideally without penetrating the sample sides. Following fracture development, permeability was characterized as a function of hydrostatic pressure and injection pressure. X-ray video radioadiography was used to study changes in fracture aperture in relation to permeability and proppant embedment. X-ray tomography was collected at steady-state conditions to fully characterize fracture geometry and proppant distribution.

  14. Hydraulic fracture model comparison study: Complete results

    SciTech Connect

    Warpinski, N.R.; Abou-Sayed, I.S.; Moschovidis, Z.; Parker, C.

    1993-02-01

    Large quantities of natural gas exist in low permeability reservoirs throughout the US. Characteristics of these reservoirs, however, make production difficult and often economic and stimulation is required. Because of the diversity of application, hydraulic fracture design models must be able to account for widely varying rock properties, reservoir properties, in situ stresses, fracturing fluids, and proppant loads. As a result, fracture simulation has emerged as a highly complex endeavor that must be able to describe many different physical processes. The objective of this study was to develop a comparative study of hydraulic-fracture simulators in order to provide stimulation engineers with the necessary information to make rational decisions on the type of models most suited for their needs. This report compares the fracture modeling results of twelve different simulators, some of them run in different modes for eight separate design cases. Comparisons of length, width, height, net pressure, maximum width at the wellbore, average width at the wellbore, and average width in the fracture have been made, both for the final geometry and as a function of time. For the models in this study, differences in fracture length, height and width are often greater than a factor of two. In addition, several comparisons of the same model with different options show a large variability in model output depending upon the options chosen. Two comparisons were made of the same model run by different companies; in both cases the agreement was good. 41 refs., 54 figs., 83 tabs.

  15. Interaction of hydraulic and buckling mechanisms in blowout fractures.

    PubMed

    Nagasao, Tomohisa; Miyamoto, Junpei; Jiang, Hua; Tamaki, Tamotsu; Kaneko, Tsuyoshi

    2010-04-01

    The etiology of blowout fractures is generally attributed to 2 mechanisms--increase in the pressure of the orbital contents (the hydraulic mechanism) and direct transmission of impacts on the orbital walls (the buckling mechanism). The present study aims to elucidate whether or not an interaction exists between these 2 mechanisms. We performed a simulation experiment using 10 Computer-Aided-Design skull models. We applied destructive energy to the orbits of the 10 models in 3 different ways. First, to simulate pure hydraulic mechanism, energy was applied solely on the internal walls of the orbit. Second, to simulate pure buckling mechanism, energy was applied solely on the inferior rim of the orbit. Third, to simulate the combined effect of the hydraulic and buckling mechanisms, energy was applied both on the internal wall of the orbit and inferior rim of the orbit. After applying the energy, we calculated the areas of the regions where fracture occurred in the models. Thereafter, we compared the areas among the 3 energy application patterns. When the hydraulic and buckling mechanisms work simultaneously, fracture occurs on wider areas of the orbital walls than when each of these mechanisms works separately. The hydraulic and buckling mechanisms interact, enhancing each other's effect. This information should be taken into consideration when we examine patients in whom blowout fracture is suspected.

  16. Hydrodynamics of a vertical hydraulic fracture

    SciTech Connect

    Narasimhan, T.N.

    1987-03-24

    We have developed a numerical algorithm, HUBBERT, to simulate the hydrodynamics of a propagating vertical, rectangular fracture in an elastic porous medium. Based on the IFD method, this algorithm assumes fracture geometry to be prescribed. The breakdown and the creation of the incipient fracture is carried out according to the Hubbert-Willis theory. The propagation of the fracture is based on the criterion provided by Griffith, based on energy considerations. The deformation properties of the open fracture are based on simple elasticity solutions. The fracture is assumed to have an elliptical shape to a distance equal to the fracture height, beyond which the shape is assumed to be parallel plate. A consequence of Griffith's criterion is that the fracture must propagate in discrete steps. The parametric studies carried out suggest that for a clear understanding of the hydrodynamics of the hydraulic fracture many hitherto unrecognized parameters must be better understood. Among these parameters one might mention, efficiency, aperture of the newly formed fracture, stiffness of the newly formed fracture, relation between fracture aperture and permeability, and well bore compliance. The results of the studies indicate that the patterns of pressure transients and the magnitudes of fracture length appear to conform to field observations. In particular, the discrete nature of fracture propagation as well as the relevant time scales of interest inferred from the present work seem to be corroborated by seismic monitoring in the field. The results suggest that the estimation of least principal stress can be reliably made either with shut in data or with reinjection data provided that injection rates are very small.

  17. Electrokinetic coupling in hydraulic fracture propagation

    NASA Astrophysics Data System (ADS)

    Cuevas, Nestor Herman

    2009-12-01

    Electrokinetic coupling is the most popular mechanism proposed to explain observed electromagnetic signals associated with the hydraulic fracturing of rocks. Measurements in both controlled laboratory and in situ conditions show clear evidence of the phenomenon. However there have been no reports on the description of the source mechanism, its relationship to a propagating crack, nor the electromagnetic field distribution due to such a source advancing through an electrically conductive medium. In this work it is shown that a surface electric current density arising on the walls of a fluid driven propagating crack can explain the measurements of electric streaming potential recorded during hydraulic fracturing experiments. The properties of the streaming current source are studied at the microscopic scale in light of the electrokinetic coupling expected at the outermost grains of the crack's surface. Expressions are derived for the average macroscopic transport equations describing the coupled fluid, and electrical current flow, at the interface between a fluid continuum and a homogeneous porous medium, where a Darcy flow regime (porous medium) competes with a rather Poiseuille type (fracture channels). The properties of the electrokinetic boundary sources are analyzed in light of the average electrical current density arising on the interface, as the fluid electrolyte flows in both the porous media and the adjacent fluid continuum. It is found that two coupling coefficients are required to describe the streaming current density. Indeed the flow is driven by both, a tangential pressure gradient, as well as by forward momentum transfer across the permeable boundary. The coupling coefficients are obtained from the spatial average of the tangential stress exerted on the pore surfaces, and they are found to be position dependent, as the tangential stress transitions from that on the porous conduits, to that on the surface of the outer most grains. Furthermore each

  18. Review of Hydraulic Fracturing for Preconditioning in Cave Mining

    NASA Astrophysics Data System (ADS)

    He, Q.; Suorineni, F. T.; Oh, J.

    2016-12-01

    Hydraulic fracturing has been used in cave mining for preconditioning the orebody following its successful application in the oil and gas industries. In this paper, the state of the art of hydraulic fracturing as a preconditioning method in cave mining is presented. Procedures are provided on how to implement prescribed hydraulic fracturing by which effective preconditioning can be realized in any in situ stress condition. Preconditioning is effective in cave mining when an additional fracture set is introduced into the rock mass. Previous studies on cave mining hydraulic fracturing focused on field applications, hydraulic fracture growth measurement and the interaction between hydraulic fractures and natural fractures. The review in this paper reveals that the orientation of the current cave mining hydraulic fractures is dictated by and is perpendicular to the minimum in situ stress orientation. In some geotechnical conditions, these orientation-uncontrollable hydraulic fractures have limited preconditioning efficiency because they do not necessarily result in reduced fragmentation sizes and a blocky orebody through the introduction of an additional fracture set. This implies that if the minimum in situ stress orientation is vertical and favors the creation of horizontal hydraulic fractures, in a rock mass that is already dominated by horizontal joints, no additional fracture set is added to that rock mass to increase its blockiness to enable it cave. Therefore, two approaches that have the potential to create orientation-controllable hydraulic fractures in cave mining with the potential to introduce additional fracture set as desired are proposed to fill this gap. These approaches take advantage of directional hydraulic fracturing and the stress shadow effect, which can re-orientate the hydraulic fracture propagation trajectory against its theoretical predicted direction. Proppants are suggested to be introduced into the cave mining industry to enhance the

  19. 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

  20. Uncertainty Analysis of Simulated Hydraulic Fracturing

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  1. Understanding hydraulic fracturing: a multi-scale problem.

    PubMed

    Hyman, J D; Jiménez-Martínez, J; Viswanathan, H S; Carey, J W; Porter, M L; Rougier, E; Karra, S; Kang, Q; Frash, L; Chen, L; Lei, Z; O'Malley, D; Makedonska, N

    2016-10-13

    Despite the impact that hydraulic fracturing has had on the energy sector, the physical mechanisms that control its efficiency and environmental impacts remain poorly understood in part because the length scales involved range from nanometres to kilometres. We characterize flow and transport in shale formations across and between these scales using integrated computational, theoretical and experimental efforts/methods. At the field scale, we use discrete fracture network modelling to simulate production of a hydraulically fractured well from a fracture network that is based on the site characterization of a shale gas reservoir. At the core scale, we use triaxial fracture experiments and a finite-discrete element model to study dynamic fracture/crack propagation in low permeability shale. We use lattice Boltzmann pore-scale simulations and microfluidic experiments in both synthetic and shale rock micromodels to study pore-scale flow and transport phenomena, including multi-phase flow and fluids mixing. A mechanistic description and integration of these multiple scales is required for accurate predictions of production and the eventual optimization of hydrocarbon extraction from unconventional reservoirs. Finally, we discuss the potential of CO2 as an alternative working fluid, both in fracturing and re-stimulating activities, beyond its environmental advantages.This article is part of the themed issue 'Energy and the subsurface'.

  2. Understanding hydraulic fracturing: a multi-scale problem

    PubMed Central

    Hyman, J. D.; Jiménez-Martínez, J.; Viswanathan, H. S.; Carey, J. W.; Porter, M. L.; Rougier, E.; Karra, S.; Kang, Q.; Frash, L.; Chen, L.; Lei, Z.; O’Malley, D.; Makedonska, N.

    2016-01-01

    Despite the impact that hydraulic fracturing has had on the energy sector, the physical mechanisms that control its efficiency and environmental impacts remain poorly understood in part because the length scales involved range from nanometres to kilometres. We characterize flow and transport in shale formations across and between these scales using integrated computational, theoretical and experimental efforts/methods. At the field scale, we use discrete fracture network modelling to simulate production of a hydraulically fractured well from a fracture network that is based on the site characterization of a shale gas reservoir. At the core scale, we use triaxial fracture experiments and a finite-discrete element model to study dynamic fracture/crack propagation in low permeability shale. We use lattice Boltzmann pore-scale simulations and microfluidic experiments in both synthetic and shale rock micromodels to study pore-scale flow and transport phenomena, including multi-phase flow and fluids mixing. A mechanistic description and integration of these multiple scales is required for accurate predictions of production and the eventual optimization of hydrocarbon extraction from unconventional reservoirs. Finally, we discuss the potential of CO2 as an alternative working fluid, both in fracturing and re-stimulating activities, beyond its environmental advantages. This article is part of the themed issue ‘Energy and the subsurface’. PMID:27597789

  3. Reactivation of a Propped Hydraulic Fracture

    NASA Astrophysics Data System (ADS)

    Sarvaramini, E.; Garagash, D.

    2014-12-01

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

  4. 3D Numerical Modeling of the Propagation of Hydraulic Fracture at Its Intersection with Natural (Pre-existing) Fracture

    NASA Astrophysics Data System (ADS)

    Dehghan, Ali Naghi; Goshtasbi, Kamran; Ahangari, Kaveh; Jin, Yan; Bahmani, Aram

    2017-02-01

    A variety of 3D numerical models were developed based on hydraulic fracture experiments to simulate the propagation of hydraulic fracture at its intersection with natural (pre-existing) fracture. Since the interaction between hydraulic and pre-existing fractures is a key condition that causes complex fracture patterns, the extended finite element method was employed in ABAQUS software to simulate the problem. The propagation of hydraulic fracture in a fractured medium was modeled in two horizontal differential stresses (Δ σ) of 5e6 and 10e6 Pa considering different strike and dip angles of pre-existing fracture. The rate of energy release was calculated in the directions of hydraulic and pre-existing fractures (G_{{frac}} /G_{{rock}}) at their intersection point to determine the fracture behavior. Opening and crossing were two dominant fracture behaviors during the hydraulic and pre-existing fracture interaction at low and high differential stress conditions, respectively. The results of numerical studies were compared with those of experimental models, showing a good agreement between the two to validate the accuracy of the models. Besides the horizontal differential stress, strike and dip angles of the natural (pre-existing) fracture, the key finding of this research was the significant effect of the energy release rate on the propagation behavior of the hydraulic fracture. This effect was more prominent under the influence of strike and dip angles, as well as differential stress. The obtained results can be used to predict and interpret the generation of complex hydraulic fracture patterns in field conditions.

  5. Fluid Compressibility Effects during Hydraulic Fracture: an Opportunity for Gas Fracture Revival

    NASA Astrophysics Data System (ADS)

    Mighani, S.; Boulenouar, A.; Moradian, Z.; Evans, J. B.; Bernabe, Y.

    2015-12-01

    Hydraulic fracturing results when internal pore pressure is increased above a critical value. As the fracture extends, the fluid flows to the crack tip. The fracturing process depends strongly on the physical properties of both the porous solid and the fluid (e.g. porosity and elastic moduli for the solid, viscosity and compressibility for the fluid). It is also affected by the in-situ stress and pore pressure conditions. Here, we focus on the effect of fluid properties on hydraulic fracturing under conventional triaxial loading. Cylinders of Solnhofen limestone (a fine-grained, low permeability rock) were prepared with a central borehole through which different pressurized fluids such as oil, water or argon, were introduced. Preliminary experiments were performed using a confining pressure of 5 MPa and axial stress of 7 MPa. Our goal was to monitor fracture extension using strain gauges, acoustic emissions (AE) recording and ultrasonic velocity measurements. We also tried to compare the data with analytical models of fracture propagation. Initial tests showed that simple bi-wing fractures form when the fracturing fluid is relatively incompressible. With argon as pore fluid, a complex fracture network was formed. We also observed that the breakdown pressure was higher with argon than with less compressible fluids. After fracturing occurred, we cycled fluid pressure for several times. During the first cycles, re-opening of the fracture was associated with additional propagation. In general, it took 4 cycles to inhibit further propagation. Analytical models suggest that initial fractures occurring with compressible fluids tend to stabilize. Hence, formation and extension of additional fractures may occur, leading to a more complex morphology. Conversely, fractures formed by incompressible fluids remain critically stressed as they extend, thus producing a simple bi-wing fracture. Using compressible fracturing fluids could be a suitable candidate for an efficient

  6. 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.

  7. 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

  8. Rheological characterization of hydraulic fracturing slurries

    SciTech Connect

    Shah, S.N. . Research and Engineering Dept.)

    1993-05-01

    Few studies have dealt with the flow behavior of concentrated suspensions or slurries prepared with non-Newtonian carrier fluids. Therefore, the purpose of this investigation is to present experimental results obtained by pumping various hydraulic fracturing slurries into a fracture model and gathering data on differential pressure vs. flow rate. Several concentrations of hydroxypropyl guard (HPG), a wide range of proppant concentrations, and three test temperatures were studies. The effects of such variables as polymer gelling-agent concentration, proppant concentration, test temperature, and fracture-flow shear rate on the rheological properties of slurries were investigated. The correlations for predicting the relative slurry viscosity for these HPG fluids are presented. Substantial increases in viscosity of fracturing gels were observed, and results are discussed in light of several affecting variables. Results also are compared with those available for Newtonian and non-Newtonian concentrated suspensions. Applications of these correlations to estimate the hindered particle-settling velocity in the fracture caused by the presence of surrounding particles also is discussed. The correlations presented can easily be included in any currently available 2D or 3D fracture-design simulators; thus, the information can be applied directly to predict fracture geometry and extension.

  9. Smart magnetic markers use in hydraulic fracturing.

    PubMed

    Zawadzki, Jarosław; Bogacki, Jan

    2016-11-01

    One of the main challenges and unknowns during shale gas exploration is to assess the range and efficiency of hydraulic fracturing. It is also essential to assess the distribution of proppant, which keeps the fracture pathways open. Solving these problems may considerably increase the efficiency of the shale gas extraction. Because of that, the idea of smart magnetic marker, which can be detected when added to fracturing fluid, has been considered for a long time. This study provides overview of the possibilities of magnetic marker application for shale gas extraction. The imaging methods using electromagnetic markers, are considered or developed in two directions. The first possibility is the markers' electromagnetic activity throughout the whole volume of the fracturing fluid. Thus, it can be assumed that the whole fracturing fluid is the marker. Among these type of hydraulic fracturing solutions, ferrofluid could be considered. The second possibility is marker, which is just one of many components of the fracturing fluid. In this case feedstock magnetic materials, ferrites and nanomaterials could be considered. Magnetic properties of magnetite could be too low and ferrofluids' or nanomaterials' price is unacceptably high. Because of that, ferrites, especially ZnMn ferrites seems to be the best material for magnetic marker. Because of the numerous applications in electronics, it is cheap and easily available, although the price is higher, then that of magnetite. The disadvantage of using ferrite, could be too small mechanical strength. It creates an essential need for combining magnetic marker with proppant into magnetic-ceramic composite. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Monitoring hydraulic fractures: state estimation using an extended Kalman filter

    NASA Astrophysics Data System (ADS)

    Alves Rochinha, Fernando; Peirce, Anthony

    2010-02-01

    There is considerable interest in using remote elastostatic deformations to identify the evolving geometry of underground fractures that are forced to propagate by the injection of high pressure viscous fluids. These so-called hydraulic fractures are used to increase the permeability in oil and gas reservoirs as well as to pre-fracture ore-bodies for enhanced mineral extraction. The undesirable intrusion of these hydraulic fractures into environmentally sensitive areas or into regions in mines which might pose safety hazards has stimulated the search for techniques to enable the evolving hydraulic fracture geometries to be monitored. Previous approaches to this problem have involved the inversion of the elastostatic data at isolated time steps in the time series provided by tiltmeter measurements of the displacement gradient field at selected points in the elastic medium. At each time step, parameters in simple static models of the fracture (e.g. a single displacement discontinuity) are identified. The approach adopted in this paper is not to regard the sequence of sampled elastostatic data as independent, but rather to treat the data as linked by the coupled elastic-lubrication equations that govern the propagation of the evolving hydraulic fracture. We combine the Extended Kalman Filter (EKF) with features of a recently developed implicit numerical scheme to solve the coupled free boundary problem in order to form a novel algorithm to identify the evolving fracture geometry. Numerical experiments demonstrate that, despite excluding significant physical processes in the forward numerical model, the EKF-numerical algorithm is able to compensate for the un-modeled dynamics by using the information fed back from tiltmeter data. Indeed the proposed algorithm is able to provide reasonably faithful estimates of the fracture geometry, which are shown to converge to the actual hydraulic fracture geometry as the number of tiltmeters is increased. Since the location of

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

    EPA Pesticide Factsheets

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

  12. 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.

  13. Injection-Sensitive Mechanics of Hydraulic Fracture Interaction with Discontinuities

    NASA Astrophysics Data System (ADS)

    Chuprakov, D.; Melchaeva, O.; Prioul, R.

    2014-09-01

    We develop a new analytical model, called OpenT, that solves the elasticity problem of a hydraulic fracture (HF) contact with a pre-existing discontinuity natural fracture (NF) and the condition for HF re-initiation at the NF. The model also accounts for fluid penetration into the permeable NFs. For any angle of fracture intersection, the elastic problem of a blunted dislocation discontinuity is solved for the opening and sliding generated at the discontinuity. The sites and orientations of a new tensile crack nucleation are determined based on a mixed stress- and energy-criterion. In the case of tilted fracture intersection, the finite offset of the new crack initiation point along the discontinuity is computed. We show that aside from known controlling parameters such stress contrast, cohesional and frictional properties of the NFs and angle of intersection, the fluid injection parameters such as the injection rate and the fluid viscosity are of first-order in the crossing behavior. The model is compared to three independent laboratory experiments, analytical criteria of Blanton, extended Renshaw-Pollard, as well as fully coupled numerical simulations. The relative computational efficiency of OpenT model (compared to the numerical models) makes the model attractive for implementation in modern engineering tools simulating hydraulic fracture propagation in naturally fractured environments.

  14. Strategies for Creating Prescribed Hydraulic Fractures in Cave Mining

    NASA Astrophysics Data System (ADS)

    He, Q.; Suorineni, F. T.; Oh, J.

    2017-04-01

    The cave mining method was traditionally applied to massive low-grade, weak orebodies at shallow depths (less than 500 m) that favour cave propagation under gravity. Currently, this method is being applied to stronger orebodies and is taking place at depths of up to 2000 m below the surface. To ensure continuous cave propagation, preconditioning of the orebody is essential in this latter caving environment to improve rock mass caveability and to decrease fragmentation sizes. Hydraulic fracturing was initiated in the oil industry and is now being used in the cave mining industry as a preconditioning method and for stalled caves reactivation. A limitation of conventional hydraulic fracturing in the cave mining industry is that the hydraulic fracture orientation is uncontrollable and is dictated by the minimum in situ stress orientation. The preconditioning effectiveness of orientation-uncontrollable hydraulic fractures is limited in some geotechnical conditions, and the concept of creating orientation-controllable hydraulic fractures, here termed prescribed hydraulic fractures, is proposed to fill this gap. In this paper, the feasibility of the proposed approaches to creating prescribed hydraulic fractures is presented based on previous studies and numerical modelling. The numerical modelling code reliability in simulating the hydraulic fracture propagation and reorientation process was validated by comparing with laboratory results in the reported literature. In addition, the sensitivity of the prescribed hydraulic fracturing to the in situ stress condition and rock mass properties is examined.

  15. Fracture size scaling of hydraulic fracture stimulations in shale reservoirs

    NASA Astrophysics Data System (ADS)

    Urbancic, T.; Baig, A. M.

    2014-12-01

    It is becoming widely evident that hydraulic fracture stimulations in shale reservoirs can result in the generation of events with magnitudes M>0. These events are of concern both to the public as potential geo-hazards possibly affecting groundwater conditions and surface infra-structure, and to engineers for optimizing productivity and engineering design. Typically, in these environments, recording bandwidth limitations has resulted in a bias towards the consideration of events with M<0. This in turn has limited the observable fracture sizes to those constrained within lithological units. By extending the recording bandwidth to lower frequencies, the dimensions of the observable fractures are also extended to include larger fractures/faults activated during the stimulation. Our observations suggest that these larger-scale events can contribute upwards of 80% of the overall seismic budget or energy release associated with the stimulation process. Effective analysis of scaling relations independent of recording further suggests that breakdowns in scaling can be related to the presence of barriers to growth such as contrasts in rock properties associated with different lithological units. Generally, detected larger-magnitude events are associated with smaller-magnitude events, M<0, suggesting that these latter events can be used to characterize aspects of the rupture process whereas their associated signals observed with the low-frequency network can be used to characterize the overall fracture/fault behavior. By accounting for the presence of larger events, additional activated fracture surface area within the reservoir results in a significant increase in surface area. In an example provided, these events account for a further ~10 km2 of additional activated fracture surface area than estimated based on only utilizing high-frequency band-limited recordings. Overall, the identification of the actual discrete fracture network over many size scales allows for a better

  16. An analytical model for hydraulic fracturing in shallow bedrock formations.

    PubMed

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

    2011-01-01

    A theoretical method is proposed to estimate post-fracturing fracture size and transmissivity, and as a test of the methodology, data collected from two wells were used for verification. This method can be employed before hydrofracturing in order to obtain estimates of the potential hydraulic benefits of hydraulic fracturing. Five different pumping test analysis methods were used to evaluate the well hydraulic data. The most effective methods were the Papadopulos-Cooper model (1967), which includes wellbore storage effects, and the Gringarten-Ramey model (1974), known as the single horizontal fracture model. The hydraulic parameters resulting from fitting these models to the field data revealed that as a result of hydraulic fracturing, the transmissivity increased more than 46 times in one well and increased 285 times in the other well. The model developed by dos Santos (2008), which considers horizontal radial fracture propagation from the hydraulically fractured well, was used to estimate potential fracture geometry after hydrofracturing. For the two studied wells, their fractures could have propagated to distances of almost 175 m or more and developed maximum apertures of about 2.20 mm and hydraulic apertures close to 0.30 mm. Fracturing at this site appears to have expanded and propagated existing fractures and not created new fractures. Hydraulic apertures calculated from pumping test analyses closely matched the results obtained from the hydraulic fracturing model. As a result of this model, post-fracturing geometry and resulting post-fracturing well yield can be estimated before the actual hydrofracturing. Copyright © 2010 The Author(s). Journal compilation © 2010 National Ground Water Association.

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

    SciTech Connect

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

    1985-03-01

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

  18. Investigation of possible wellbore cement failures during hydraulic fracturing operations

    EPA Pesticide Factsheets

    Researchers used the peer-reviewed TOUGH+ geomechanics computational software and simulation system to investigate the possibility of fractures and shear failure along vertical wells during hydraulic fracturing operations.

  19. 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...

  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. 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

  2. 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.

  3. Hydraulic Fracture Stimulation Treatments at East Mesa, Well 58-30; Geothermal Reservoir Well Stimulation Program; Experiment 3 and 4

    SciTech Connect

    1982-02-01

    The tests reported were part of the DOE Geothermal Reservoir Well Stimulation Program. This East Mesa (Imperial Valley, CA) well was successfully stimulated with two fracture treatments, a dendritic fracture and a planar fracture. The natural flow production of the well increased 114 percent, to 197,900 lb/hr. These tests were among the few successful attempts of this program to increase flow from geothermal production wells. The general belief is that these tests worked OK primarily because the formation was sedimentary rock (similar to rock in most oil and gas wells that have been stimulated successfully. Similar tests in geothermal hard rock reservoirs did not work very well. (DJE 2005)

  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.

  5. Treatment of hydraulic fracturing wastewater by wet air oxidation.

    PubMed

    Wang, Wei; Yan, Xiuyi; Zhou, Jinghui; Ma, Jiuli

    2016-01-01

    Wastewater produced by hydraulic fracturing for oil and gas production is characterized by high salinity and high chemical oxygen demand (COD). We applied a combination of flocculation and wet air oxidation technology to optimize the reduction of COD in the treatment of hydraulic fracturing wastewater. The experiments used different values of flocculant, coagulant, and oxidizing agent added to the wastewater, as well as different reaction times and treatment temperatures. The use of flocculants for the pretreatment of fracturing wastewater was shown to improve treatment efficiency. The addition of 500 mg/L of polyaluminum chloride (PAC) and 20 mg/L of anionic polyacrylamide (APAM) during pretreatment resulted in a COD removal ratio of 8.2% and reduced the suspended solid concentration of fracturing wastewater to 150 mg/L. For a solution of pretreated fracturing wastewater with 12 mL of added H2O2, the COD was reduced to 104 mg/L when reacted at 300 °C for 75 min, and reduced to 127 mg/L when reacted at the same temperature for 45 min while using a 1 L autoclave. An optimal combination of these parameters produced treated wastewater that met the GB 8978-1996 'Integrated Wastewater Discharge Standard' level I emission standard.

  6. Kerogen-Hydraulic Fracture Fluid Interactions: Reactivity and Contaminant Release

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    The use of hydraulic fracturing of tight shales to produce oil and natural gas has grown significantly in recent years, yet it remains relatively inefficient, recovering only an estimated 5% and 25% of the oil and gas present, respectively. The need to improve efficiency and diminish environmental impact has prompted research into fundamental geochemical reactions occurring in shales. In particular, reactions between kerogen and fracture fluid components are poorly understood. Kerogen is the precursor of these hydrocarbons and contains metals in addition to organic material; it is also electron rich and therefore susceptible to oxidation and release of a variety of elements. Although some mineral phases in the shales are expected to undergo dissolution-precipitation reactions, kerogen is generally considered to be relatively unreactive [1]. Here we have investigated reactions between isolated kerogen and a hydraulic fracturing fluid typical of that used in the Marcellus shale. These experiments show that kerogen, as well as redox-sensitive minerals within shales, react with fracture fluid. In particular, kerogen exhibited more extensive release of certain metals (e.g. Al, Ba, Cu, among others) than was observed for bulk shale under the same experimental conditions. This evidence suggests that kerogen may be far more reactive to fracture fluids than previously thought. In particular, these results suggest that kerogen may significantly impact the compositions of produced waters, which have previously been attributed solely to mineral reactions. They also emphasize the need for further characterization of kerogen and its reactions with complex hydraulic fracturing fluids. [1] Vandenbroucke and Largeau (2007) Org. Geochem.

  7. 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

  8. [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. © Georg Thieme Verlag KG Stuttgart · New York.

  9. Characterization of the hydraulic properties of fractures in chalk.

    PubMed

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

    2003-01-01

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

  10. 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...

  11. 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...

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    The finding of considerable volumes of hydrocarbon resources within tight sedimentary rock formations in the UK led to focused attention on the fundamental fracture properties of low permeability rock types and hydraulic fracturing. Despite much research in these fields, there remains a scarcity of available experimental data concerning the fracture mechanics of fluid driven fracturing and the fracture properties of anisotropic, low permeability rock types. In this study, hydraulic fracturing is simulated in a controlled laboratory environment to track fracture nucleation (location) and propagation (velocity) in space and time and assess how environmental factors and rock properties influence the fracture process and the developing fracture network. Here we report data on employing fluid overpressure to generate a permeable network of micro tensile fractures in a highly anisotropic shale ( 50% P-wave velocity anisotropy). Experiments are carried out in a triaxial deformation apparatus using cylindrical samples. The bedding planes are orientated either parallel or normal to the major principal stress direction (σ1). A newly developed technique, using a steel guide arrangement to direct pressurised fluid into a sealed section of an axially drilled conduit, allows the pore fluid to contact the rock directly and to initiate tensile fractures from the pre-defined zone inside the sample. Acoustic Emission location is used to record and map the nucleation and development of the micro-fracture network. Indirect tensile strength measurements at atmospheric pressure show a high tensile strength anisotropy ( 60%) of the shale. Depending on the relative bedding orientation within the stress field, we find that fluid induced fractures in the sample propagate in two of the three principal fracture orientations: Divider and Short-Transverse. The fracture progresses parallel to the bedding plane (Short-Transverse orientation) if the bedding plane is aligned (parallel) with the

  13. Study of pore pressure reaction on hydraulic fracturing

    NASA Astrophysics Data System (ADS)

    Trimonova, Mariia; Baryshnikov, Nikolay; Turuntaev, Sergey; Zenchenko, Evgeniy; Zenchenko, Petr

    2017-04-01

    We represent the results of the experimental study of the hydraulic fracture propagation influence on the fluid pore pressure. Initial pore pressure was induced by injection and production wells. The experiments were carried out according to scaling analysis based on the radial model of the fracture. All required geomechanical and hydrodynamical properties of a sample were derived from the scaling laws. So, gypsum was chosen as a sample material and vacuum oil as a fracturing fluid. The laboratory setup allows us to investigate the samples of cylindrical shape. It can be considered as an advantage in comparison with standard cubic samples, because we shouldn't consider the stress field inhomogeneity induced by the corners. Moreover, we can set 3D-loading by this setting. Also the sample diameter is big enough (43cm) for placing several wells: the fracturing well in the center and injection and production wells on two opposite sides of the central well. The experiment consisted of several stages: a) applying the horizontal pressure; b) applying the vertical pressure; c) water solution injection in the injection well with a constant pressure; d) the steady state obtaining; e) the oil injection in the central well with a constant rate. The pore pressure was recorded in the 15 points along bottom side of the sample during the whole experiment. We observe the pore pressure change during all the time of the experiment. First, the pore pressure changed due to water injection. Then we began to inject oil in the central well. We compared the obtained experimental data on the pore pressure changes with the solution of the 2D single-phase equation of pore-elasticity, and we found significant difference. The variation of the equation parameters couldn't help to resolve the discrepancy. After the experiment, we found that oil penetrated into the sample before and after the fracture initiation. This fact encouraged us to consider another physical process - the oil

  14. High Speed Strain Measurements Surrounding Hydraulic Fracture in Brittle Hydrogel

    NASA Astrophysics Data System (ADS)

    Steinhardt, Will; Rubinstein, Shmuel

    2015-11-01

    Hydraulic fractures of oil and gas shales occur miles underground, below complex, layered rocks, making measurements of their dynamics, extent, or structure difficult to impossible. Rocks are heterogeneous at a wide range of length scales, and investigating how these non-uniformities affect the propagation and extent of fractures is vital to improving both the safety and efficiency of hydraulic fracturing operations. To study these effects we have developed a model system using brittle, heavily cross-linked hydrogels that we can fracture with fluids and observe with a fast camera. By embedding tracer particles within the gel and using laser sheet microscopy, we obtain three dimensional stress and strain maps of the zone surrounding a hydraulic fracture tip. Gels can also be set in layers or interfaces with tunable strengths or with designed heterogeneities, allowing us to understand the fundamental science of hydraulic fractures and investigate the dynamics of controllably complex materials.

  15. Laboratory investigation of fracture propagation for cement samples by hydraulic fracturing under the tri-axial stress condition.

    NASA Astrophysics Data System (ADS)

    Jang, Bo-An; Riu, Hee-Sung

    2017-04-01

    Hydraulic fracturing for samples were carried out to investigate characteristics of fracture propagation depending on viscosities of injection fluid and in-situ stress states. Ten cubic samples with 20cm each side were produced using cement and cured in the water for more than one month. Samples were place in the true tri-axial compressive machine with three different principal stresses. Injection hole was drilled and sample was hydraulically fractured with the constant injection rate. Injection pressures with time and acoustic emission (AE) signals were measured during experiments. Patterns of fractures produced by hydraulic fracturing were investigated. Breakdown pressures increased exponentially as viscosities of injection fluid increased. Pattern of fracture development varied depending on differential stresses which are the difference between the major and minor principal stresses. At low differential stress, multiple fractures which were sub-parallel to the major principal stress direction were propagated from the injection hole. In some samples, the fracture directions changed during propagation. However, a single fracture were propagated parallel to the major principal stress direction at high differential stress. Results of AE showed similar patterns. Contour map of AE source locations at low differential stress showed bigger width than those at high low differential stress, indicating that hydraulic fracturing for shale gas should be performed along the direction of the minimum differential stress.

  16. Monitoring the interaction of hydraulic fracturing fluid with Marcellus Shale using Sr isotopes: a comparison of laboratory experiments with field scale observations (Invited)

    NASA Astrophysics Data System (ADS)

    Wall, A. J.; Hakala, A.; Marcon, V.; Joseph, C.

    2013-12-01

    Strontium isotopes have the potential to be an effective tool for differentiating Marcellus Shale derived-fluids from other sources in surface and ground waters (Chapman et al. 2012, doi: 10.1021/es204005g). Water that is co-produced during gas extraction is likely influenced by fluid/rock interactions during hydraulic fracturing (HF) and monitoring changes in Sr isotope ratios can provide insight into reactions occurring within the shale formation. However, questions persist as to what controls the Sr isotopic composition of Marcellus Shale fluids, especially during HF. Here we compare laboratory experiments, simulating the dissolution of the Marcellus Shale during HF, with a time-series of water samples taken from a Marcellus Shale gas wells after HF has occurred. For the laboratory experiments, a core sample of Marcellus Shale from Greene County, PA was crushed and placed into a high P and T reaction vessel. Solutions were added in two different experiments: one with synthetic brine, and another using brine+HF fluid. The HF fluid was made up of components listed on fracfocus.org. Experiments were run for ~16 days at 27.5 MPa and 130oC. Aqueous samples were periodically removed for analysis and Sr isotope ratios were measured by MC-ICP-MS. Using just brine, the pH of the solution decreased from 7.6 to 5.3 after 24 hrs, then reached a steady state at ~6.1. Sr/Ca molar ratios in the fluid started at 2.3 after 24 hours and decreased to 1.8 over ~16 days. During this time only 6% of the total inorganic carbon (TIC) dissolved from the shale. The ɛSr values started at +43.2 and decreased to +42.4. In the experiment using brine+HF fluid, the pH started at 1.8 and rose slowly to a steady value of 5.6 by day 6. The Sr and Ca concentrations were higher than the brine experiment, but the Sr/Ca ratios remained lower at ~0.3 through the experiment. The increased Ca release, as well as the dissolution of over 60% of the TIC, suggests the dissolution of a carbonate mineral

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

    EPA Pesticide Factsheets

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

  18. 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

  19. 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.

  20. 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.

  1. Understanding Hydraulic Fracturing: A Multi-Scale Problem

    SciTech Connect

    Hyman, Jeffrey De'Haven; Gimenez Martinez, Joaquin; Viswanathan, Hari S.; Carey, James William; Porter, Mark L.; Rougier, Esteban; Karra, Satish; Kang, Qinjun; Frash, Luke; Chen, Li; Lei, Zhou; O'Malley, Daniel; Makedonska, Nataliia

    2016-09-05

    Despite the impact that hydraulic fracturing has had on the energy sector, the physical mechanisms that control its efficiency and environmental impacts remain poorly understood in part because the length scales involved range from nano-meters to kilo-meters. We characterize flow and transport in shale formations across and between these scales using integrated computational, theoretical, and experimental efforts. At the field scale, we use discrete fracture network modeling to simulate production at a well site whose fracture network is based on a site characterization of a shale formation. At the core scale, we use triaxial fracture experiments and a finite-element discrete-element fracture propagation model with a coupled fluid solver to study dynamic crack propagation in low permeability shale. We use lattice Boltzmann pore-scale simulations and microfluidic experiments in both synthetic and real micromodels to study pore-scale flow phenomenon such as multiphase flow and mixing. A mechanistic description and integration of these multiple scales is required for accurate predictions of production and the eventual optimization of hydrocarbon extraction from unconventional reservoirs.

  2. Understanding Hydraulic Fracturing: A Multi-Scale Problem

    DOE PAGES

    Hyman, Jeffrey De'Haven; Gimenez Martinez, Joaquin; Viswanathan, Hari S.; ...

    2016-09-05

    Despite the impact that hydraulic fracturing has had on the energy sector, the physical mechanisms that control its efficiency and environmental impacts remain poorly understood in part because the length scales involved range from nano-meters to kilo-meters. We characterize flow and transport in shale formations across and between these scales using integrated computational, theoretical, and experimental efforts. At the field scale, we use discrete fracture network modeling to simulate production at a well site whose fracture network is based on a site characterization of a shale formation. At the core scale, we use triaxial fracture experiments and a finite-element discrete-elementmore » fracture propagation model with a coupled fluid solver to study dynamic crack propagation in low permeability shale. We use lattice Boltzmann pore-scale simulations and microfluidic experiments in both synthetic and real micromodels to study pore-scale flow phenomenon such as multiphase flow and mixing. A mechanistic description and integration of these multiple scales is required for accurate predictions of production and the eventual optimization of hydrocarbon extraction from unconventional reservoirs.« less

  3. Hydraulic Fracturing Fluid Analysis for Regulatory Parameters - A Progress Report

    EPA Pesticide Factsheets

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

  4. Hydraulic fracturing - an attempt of DEM simulation

    NASA Astrophysics Data System (ADS)

    Kosmala, Alicja; Foltyn, Natalia; Klejment, Piotr; Dębski, Wojciech

    2017-04-01

    Hydraulic fracturing is a technique widely used in oil, gas and unconventional reservoirs exploitation in order to enable the oil/gas to flow more easily and enhance the production. It relays on pumping into a rock a special fluid under a high pressure which creates a set of microcracks which enhance porosity of the reservoir rock. In this research, attempt of simulation of such hydrofracturing process using the Discrete Element Method approach is presented. The basic assumption of this approach is that the rock can be represented as an assembly of discrete particles cemented into a rigid sample (Potyondy 2004). An existence of voids among particles simulates then a pore system which can be filled out by fracturing fluid, numerically represented by much smaller particles. Following this microscopic point of view and its numerical representation by DEM method we present primary results of numerical analysis of hydrofracturing phenomena, using the ESyS-Particle Software. In particular, we consider what is happening in distinct vicinity of the border between rock sample and fracking particles, how cracks are creating and evolving by breaking bonds between particles, how acoustic/seismic energy is releasing and so on. D.O. Potyondy, P.A. Cundall. A bonded-particle model for rock. International Journal of Rock Mechanics and Mining Sciences, 41 (2004), pp. 1329-1364.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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/fα 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.

  10. Electrical and Magnetic Imaging of Proppants in Shallow Hydraulic Fractures

    NASA Astrophysics Data System (ADS)

    Denison, J. L. S.; Murdoch, L. C.; LaBrecque, D. J.; Slack, W. W.

    2015-12-01

    Hydraulic fracturing is an important tool to increase the productivity of wells used for oil and gas production, water resources, and environmental remediation. Currently there are relatively few tools available to monitor the distribution of proppants within a hydraulic fracture, or the propagation of the fracture itself. We have been developing techniques for monitoring hydraulic fractures by injecting electrically conductive, dielectric, or magnetically permeable proppants. We then use the resulting contrast with the enveloping rock to image the proppants using geophysical methods. Based on coupled laboratory and numerical modeling studies, three types of proppants were selected for field evaluation. Eight hydraulic fractures were created near Clemson, SC in May of 2015 by injecting specialized proppants at a depth of 1.5 m. The injections created shallow sub-horizontal fractures extending several meters from the injection point.Each cell had a dense array of electrodes and magnetic sensors on the surface and four shallow vertical electrode arrays that were used to obtain data before and after hydraulic fracturing. Net vertical displacement and transient tilts were also measured. Cores from 130 boreholes were used to characterize the general geometries, and trenching was used to characterize the forms of two of the fractures in detail. Hydraulic fracture geometries were estimated by inverting pre- and post-injection geophysical data. Data from cores and trenching show that the hydraulic fractures were saucer-shaped with a preferred propagation direction. The geophysical inversions generated images that were remarkably similar in form, size, and location to the ground truth from direct observation. Displacement and tilt data appear promising as a constraint on fracture geometry.

  11. Numerical analysis of fracture propagation during hydraulic fracturing operations in shale gas systems

    EPA Pesticide Factsheets

    Researchers used the TOUGH+ geomechanics computational software and simulation system to examine the likelihood of hydraulic fracture propagation (the spread of fractures) traveling long distances to connect with drinking water aquifers.

  12. Correlating fracture trends and hydraulic head using semivariogram cloud analysis.

    PubMed

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

    2005-01-01

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

  13. 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.

  14. Hydraulic fracturing and permeability enhancement in granite from subcritical/brittle to supercritical/ductile conditions

    NASA Astrophysics Data System (ADS)

    Watanabe, Noriaki; Egawa, Motoki; Sakaguchi, Kiyotoshi; Ishibashi, Takuya; Tsuchiya, Noriyoshi

    2017-06-01

    Hydraulic fracturing experiments were conducted at 200-450°C by injecting water into cylindrical granite samples containing a borehole at an initial effective confining pressure of 40 MPa. Intensive fracturing was observed at all temperatures, but the fracturing characteristics varied with temperature, perhaps due to differences in the water viscosity. At the lowest considered temperature (200°C), fewer fractures propagated linearly from the borehole, and the breakdown pressure was twice the confining pressure. However, these characteristics disappeared with increasing temperature; the fracture pattern shifted toward the formation of a greater number of shorter fractures over the entire body of the sample, and the breakdown pressure decreased greatly. Hydraulic fracturing significantly increased the permeability at all temperatures, and this permeability enhancement was likely to form a productive geothermal reservoir even at the highest considered temperature, which exceeded both the brittle-ductile transition temperature of granite and the critical temperature of water.

  15. 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.

  16. Controlled Source Electromagnetic Monitoring of Hydraulic Fracturing

    NASA Astrophysics Data System (ADS)

    Couchman, M. J.; Everett, M. E.

    2016-12-01

    Controlled Source Electromagnetics (CSEM) have been used as a direct hydrocarbon indicator since the 1960s, with a resurgence in marine conventional settings in the new millennium, with many studies revolving around detecting a thin resistive layer such as a reservoir at 1m-3km depth. The presence of the resistive layer is characterized by a jump in electric field amplitude recorded at the boundary between the layer and the host sediments. Here the lessons learned from these studies are applied to terrestrial unconventional settings. However, unlike in marine settings where resistive hydrocarbon-charged fluids comprise a conventional reservoir, on land we are interested in electrically conductive injected fluids. The work shown here is a means to develop further methods to enable more reliable terrestrial CSEM monitoring of the flow of injected fluids associated with hydraulic fracturing of unconventional reservoirs and to detect subsurface fluids based on their CSEM signature and in turn, to infer the subsurface flow of electrically conductive injected fluids. Overall this project attempts to create more efficient fracturing, by determining fluid pathways, hence making projects more cost effective by reducing the cost of extraction. The predictive model developed focuses on the mapping of fluid flow in from a horizontal pipe in a uniform halfspace using a long in-line Horizontal Electric Dipole (HED) with electric field amplitude recorded by an array of electric field sensors. The code provided has been edited to include a long-dipole source in addition to the half dipole source originally in place in order to align with current CSEM field practices. The well casing has also been included due to its large effect on CSEM response.

  17. EPA Study of Hydraulic Fracturing and Drinking Water Resources

    EPA Science Inventory

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

  18. Hydraulic Fracturing in Coalbed Methane Development, Raton Basin, Southern Colorado

    EPA Pesticide Factsheets

    Pioneer Natural Resources has performed hydraulic fractures on 2400 shallow CBM wells in the Raton Basin with no impact to drinking water. This presentation, given by Pioneer Natural Resources, discusses why might be.

  19. EPA Published Research Related to the Hydraulic Fracturing Study

    EPA Pesticide Factsheets

    A list of publications that will support the draft assessment report on the potential impacts of hydraulic fracturing on drinking water resources. These publications have undergone peer review through the journal where the paper has been published.

  20. Executive Summary, Hydraulic Fracturing Study - Draft Assessment 2015

    EPA Pesticide Factsheets

    In this Executive Summary of the HF Draft report, EPA highlights the reviews of scientific literature to assess the potential for hydraulic fracturing for oil and gas to change the quality or quantity of drinking water resources.

  1. What can we learn from ultrasonic velocities monitoring during hydraulic fracturing of tight shale ?

    NASA Astrophysics Data System (ADS)

    Fortin, Jérôme; Stanchits, Sergei

    2016-04-01

    Methods of prediction the size and aperture of created hydraulic fracture are essential for a proper design of unconventional reservoir well stimulation. Several theoretical models describing hydraulic fracture propagation have been developed. However, there is a lack of direct field measurements of hydraulic fracture dimensions, verifying results of these models. Monitoring of elastic wave parameters may be a useful tool to estimate fracture dimensions. Indeed, the elastic wave velocity in a medium containing a fracture is sensitive to the fracture geometry and its conditions: dry fracture or saturated with fluid. In this paper, we focus on ultrasonic velocities monitoring during hydraulic fracturing of tight shale. We report the results of hydraulic fracturing of Niobrara shale outcrop block of 279 x 279 x 381 mm size from Colorado, USA. In this experiment, the block was loaded in a polyaxial loading frame made by TerraTek, a Schlumberger Company. Stresses were applied to the rock blocks independently in three directions using flat jacks. Then viscous fluid was injected into borehole at a constant flow rate. 20 PZT sensors were embedded into pockets drilled in the rock. They were used for registration of Acoustic Emission (AE) signals and for periodical ultrasonic transmissions to measure P-wave velocities in different directions. Our results show that ultrasonic measurements can be useful for understanding the mechanics of the crack growth. More precisely, from the evolution of the P-velocities and their amplitudes during the loading, we are able: (i) to estimate the velocity of the hydraulic fracture which was found to be 0.15 mm/s (that is close to the fracture velocity inferred from the dynamic of AE spatial evolution). (ii) In addition, the evolution of the P-velocities during the loading shows that a liquid-free crack always precedes the liquid front. In our experiment, the lag is estimated to be 15 mm. (iii) Finally, at fixed distances from the borehole

  2. Linear Elastic and Cohesive Fracture Analysis to Model Hydraulic Fracture in Brittle and Ductile Rocks

    NASA Astrophysics Data System (ADS)

    Yao, Yao

    2012-05-01

    Hydraulic fracturing technology is being widely used within the oil and gas industry for both waste injection and unconventional gas production wells. It is essential to predict the behavior of hydraulic fractures accurately based on understanding the fundamental mechanism(s). The prevailing approach for hydraulic fracture modeling continues to rely on computational methods based on Linear Elastic Fracture Mechanics (LEFM). Generally, these methods give reasonable predictions for hard rock hydraulic fracture processes, but still have inherent limitations, especially when fluid injection is performed in soft rock/sand or other non-conventional formations. These methods typically give very conservative predictions on fracture geometry and inaccurate estimation of required fracture pressure. One of the reasons the LEFM-based methods fail to give accurate predictions for these materials is that the fracture process zone ahead of the crack tip and softening effect should not be neglected in ductile rock fracture analysis. A 3D pore pressure cohesive zone model has been developed and applied to predict hydraulic fracturing under fluid injection. The cohesive zone method is a numerical tool developed to model crack initiation and growth in quasi-brittle materials considering the material softening effect. The pore pressure cohesive zone model has been applied to investigate the hydraulic fracture with different rock properties. The hydraulic fracture predictions of a three-layer water injection case have been compared using the pore pressure cohesive zone model with revised parameters, LEFM-based pseudo 3D model, a Perkins-Kern-Nordgren (PKN) model, and an analytical solution. Based on the size of the fracture process zone and its effect on crack extension in ductile rock, the fundamental mechanical difference of LEFM and cohesive fracture mechanics-based methods is discussed. An effective fracture toughness method has been proposed to consider the fracture process zone

  3. GCFR thermal-hydraulic experiments

    SciTech Connect

    Schlueter, G.; Baxi, C.B.; Dalle Donne, M.; Gat, U.; Fenech, H.; Hanson, D.; Hudina, M.

    1980-01-01

    The thermal-hydraulic experimental studies performed and planned for the Gas-Cooled Fast Reactor (GCFR) core assemblies are described. The experiments consist of basic studies performed to obtain correlations, and bundle experiments which provide input for code validation and design verification. These studies have been performed and are planned at European laboratories, US national laboratories, Universities in the US, and at General Atomic Company

  4. 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.

  5. Periodic Hydraulic Testing for Discerning Fracture Network Connections

    NASA Astrophysics Data System (ADS)

    Becker, M.; Le Borgne, T.; Bour, O.; Guihéneuf, N.; Cole, M.

    2015-12-01

    Discrete fracture network (DFN) models often predict highly variable hydraulic connections between injection and pumping wells used for enhanced oil recovery, geothermal energy extraction, and groundwater remediation. Such connections can be difficult to verify in fractured rock systems because standard pumping or pulse interference tests interrogate too large a volume to pinpoint specific connections. Three field examples are presented in which periodic hydraulic tests were used to obtain information about hydraulic connectivity in fractured bedrock. The first site, a sandstone in New York State, involves only a single fracture at a scale of about 10 m. The second site, a granite in Brittany, France, involves a fracture network at about the same scale. The third site, a granite/schist in the U.S. State of New Hampshire, involves a complex network at scale of 30-60 m. In each case periodic testing provided an enhanced view of hydraulic connectivity over previous constant rate tests. Periodic testing is particularly adept at measuring hydraulic diffusivity, which is a more effective parameter than permeability for identify the complexity of flow pathways between measurement locations. Periodic tests were also conducted at multiple frequencies which provides a range in the radius of hydraulic penetration away from the oscillating well. By varying the radius of penetration, we attempt to interrogate the structure of the fracture network. Periodic tests, therefore, may be uniquely suited for verifying and/or calibrating DFN models.

  6. Integration of fracturing dynamics and pressure transient analysis for hydraulic fracture evaluation

    SciTech Connect

    Arihara, N.; Abbaszadeh, M.; Wright, C.A.; Hyodo, M.

    1996-12-31

    This paper presents pre- and post-fracture pressure transient analysis, combined with net fracture pressure interpretation, for a well in a naturally fractured geothermal reservoir. Integrated analysis was performed to achieve a consistent interpretation of the created fracture geometry, propagation, conductivity, shrinkage, reservoir flow behavior, and formation permeability characteristics. The interpreted data includes two-rate pre-frac injection tests, step-rate injection tests, a series of pressure falloff tests, and the net fracturing pressure from a massive fracture treatment. Pressure transient analyses were performed utilizing advanced well test interpretation techniques and a thermal reservoir simulator with fracture propagation option. Hydraulic fracture propagation analysis was also performed Milt a generalized 3-D dynamic fracture growth model simulator. Three major conclusions resulted from the combined analysis: (1) that an increasing number of hydraulic fractures were being simultaneously propagated during the fracture treatment. (2) that the reservoir behaved as a composite reservoir Keith the outer region permeability being greater than the permeability of the region immediately surrounding the wellbore, and (3) that the created fractures extended into the outer region during the fracture treatment but retreated to the inner region several days after stimulation had ceased. These conclusions were apparent from independent pressure transient analysis and from independent hydraulic fracture propagation analysis. Integrated interpretation, however, increased the confidence in these conclusions and greatly aided the quantification of the created hydraulic fracture geometry and characterization of the reservoir permeability.

  7. Radium release mechanisms during hydraulic fracturing of Marcellus Shale

    NASA Astrophysics Data System (ADS)

    Sharma, M.; Landis, J. D.; Renock, D. J.

    2016-12-01

    Wastewater co-produced with methane from Devonian Marcellus Shale is hypersaline and enriched in Ra. Recent studies find that water injected during hydraulic fracturing can leach out significant quantities of Na, Ca, Ba and Sr from solid phases in the shale over just hours to days. Here, we show with water-rock leaching experiments that the measured 226Ra/228Ra ratios of Marcellus wastewater could also derive from rapid leaching of mineral and organic phases of the shale. Radium isotopes 226Ra (t1/2 = 1600 a) and 228Ra (t1/2 = 5.8 a) are produced through radioactive decay of 238U (t1/2 = 4.5 Ga) and 232Th (t1/2 = 14 Ga), respectively. In the absence of processes that fractionate U, Th and Ra from one another, the decay rates of each parent-daughter pair become identical over 5 half-lives of the daughter radionuclide reaching a condition of secular equilibrium. Water-rock interaction may induce pronounced deviations from secular equilibrium in the water phase, however. Such is the case during hydraulic fracturing, where Ra is soluble and mobile, and is orphaned from insoluble U and Th parents. Once 226Ra and 228Ra are mobilized no fractionation between these isotopes is expected during their transport to the surface. Thus the 226Ra/228Ra ratio in wastewater provides a fingerprint of Ra source(s). Leaching Marcellus Shale with pure water under anoxic conditions releases mainly 228Ra from clays; extraction of 228Ra from radiation damaged sites is likely the dominant contributing mechanism. Using a novel isotope dilution technique we find that 90% of the Ra released in pure water partitions back onto rock (possibly clays). In comparison, leaching with high ionic strength solutions induces the release of 226Ra from mainly organics; the breakdown of organic matter in these solutions may be the driving mechanism controlling 226Ra release in solution. Radium released by high ionic strength solutions strongly partitions into water and results in the development of leachates

  8. Imaging 3D strain field monitoring during hydraulic fracturing processes

    NASA Astrophysics Data System (ADS)

    Chen, Rongzhang; Zaghloul, Mohamed A. S.; Yan, Aidong; Li, Shuo; Lu, Guanyi; Ames, Brandon C.; Zolfaghari, Navid; Bunger, Andrew P.; Li, Ming-Jun; Chen, Kevin P.

    2016-05-01

    In this paper, we present a distributed fiber optic sensing scheme to study 3D strain fields inside concrete cubes during hydraulic fracturing process. Optical fibers embedded in concrete were used to monitor 3D strain field build-up with external hydraulic pressures. High spatial resolution strain fields were interrogated by the in-fiber Rayleigh backscattering with 1-cm spatial resolution using optical frequency domain reflectometry. The fiber optics sensor scheme presented in this paper provides scientists and engineers a unique laboratory tool to understand the hydraulic fracturing processes in various rock formations and its impacts to environments.

  9. Permeability Enhancement in Enhanced Geothermal System as a result of Hydraulic Fracturing and Jacking

    NASA Astrophysics Data System (ADS)

    Jalali, Mohammadreza; Klepikova, Maria; Fisch, Hansruedi; Amann, Florian; Loew, Simon

    2016-04-01

    A decameter-scale in-situ hydraulic stimulation and circulation (ISC) experiment has been initiated by the newly-founded Swiss Competence Centre for Energy Research - Supply of Electricity (SCCER-SoE) at Nagra's Grimsel Test Site (GTS) as a part of the work-package WP1 of the Deep Underground Laboratory (DUG-Lab) initiative. The experiment area is situated in the southern part of the GTS in a low fracture density volume of the Grimsel granodiorite. The hydraulic properties of the granitic rock mass are supposed to be similar to those expected in the crystalline basement of the alpine foreland where deep enhanced geothermal systems might be developed in future. The main objectives of the multi-disciplinary experiment are to provide a high resolution pre- and post-stimulation characterization of fracture permeability and connectivity, to investigate patterns of preferential flow paths, to describe the pressure propagation during the stimulation phases and to evaluate the efficiency of the fracture-matrix heat exchanger. A comprehensive test & monitoring layout including a fair number of boreholes instrumented with a variety of sensors (e.g. pressure, strain, displacement, temperature, and seismic sensors) is designed to collect detailed data during multiple hydraulic stimulation runs. The diffusion of fluid pressure is expected to be governed mainly by the properties and geometry of the existent fracture network. The hydraulic transmissivity of fractures are in the range of 10-7 to 10-9 m2/s whereas the matrix rock has a very low hydraulic conductivity (K ˜ 10-12 m/s). As part of the stress measurement campaign during the pre-stimulation phase of the ISC experiment, a series of hydraulic fracturing (HF) and hydraulic tests in pre-existing fractures (HTPF) were conducted. The tests were accompanied by micro-seismic monitoring within several observation boreholes to investigate the initiation and propagation of the induced fractures. Together with results from over

  10. 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.

  11. Hydraulic fracture and resilience of epithelial monolayers under stretch

    NASA Astrophysics Data System (ADS)

    Arroyo, Marino; Lucantonio, Alessandro; Noselli, Giovanni; Casares, Laura; Desimone, Antonio; Trepat, Xavier

    Epithelial monolayers are very simple and prevalent tissues. Their functions include delimiting distinct physicochemical containers and protecting us from pathogens. Epithelial fracture disrupts the mechanical integrity of this barrier, and hence compromises these functions. Here, we show that in addition to the conventional fracture resulting from excessive tissue tension, epithelia can hydraulically fracture under stretch as a result of the poroelastic nature of the matrix. We will provide experimental evidence of this counterintuitive mechanism of fracture, in which cracks appear under compression. Intriguingly, unlike tensional fracture, which is localized and catastrophic, hydraulic epithelial fracture is distributed and reversible. We will also describe the active mechanisms responsible for crack healing, and the physical principles by which the poroelastic matrix contributes to this resilient behavior.

  12. Comparison of Measured and Modelled Hydraulic Conductivities of Fractured Sandstone Cores

    NASA Astrophysics Data System (ADS)

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

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

  13. 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.

  14. 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.

  15. Imaging hydraulic fractures by microseismic migration for downhole monitoring system

    NASA Astrophysics Data System (ADS)

    Lin, Ye; Zhang, Haijiang

    2016-12-01

    It has been a challenge to accurately characterize fracture zones created by hydraulic fracturing from microseismic event locations. This is because generally detected events are not complete due to the associated low signal to noise ratio and some fracturing stages may not produce microseismic events even if fractures are well developed. As a result, spatial distribution of microseismic events may not well represent fractured zones by hydraulic fracturing. Here, we propose a new way to characterize the fractured zones by reverse time migration (RTM) of microseismic waveforms from some events. This is based on the fact that fractures filled with proppants and other fluids can act as strong scatterers for seismic waves. Therefore, for multi-stage hydraulic fracturing, recorded waveforms from microseismic events induced in a more recent stage may be scattered by fractured zones from previous stages. Through RTM of microseismic waveforms in the current stage, we can determine fractured zones created in previous stages by imaging area of strong scattering. We test the feasibility of this method using synthetic models with different configurations of microseismic event locations and borehole sensor positions for a 2D downhole microseismic monitoring system. Synthetic tests show that with a few events fractured zones can be directly imaged and thus the stimulated reservoir volume (SRV) can be estimated. Compared to the conventional location-based SRV estimation method, the proposed new method does not depend on the completeness of detected events and only a limited number of detected and located events are necessary for characterizing fracture distribution. For simplicity, the 2D model is used for illustrating the concept of microseismic RTM for imaging the fracture zone but the method can be adapted to real cases in the future.

  16. 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

  17. 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.

  18. Optimizing Shear Stresses at the Tip of a Hydraulic Fracture - What Is the Ideal Orientation of Natural Fractures with respect to Hydraulic Fracture?

    NASA Astrophysics Data System (ADS)

    Sheibani, F.; Hager, B. H.

    2015-12-01

    While many shale and unconventional plays are naturally fractured (or contain planes of weakness), these are often cemented and effectively impermeable to flow. Stress shadow behind the tip of a hydraulic fracture stablizes natural fractures. It essentially means that if impermeable natural fractures and weakness planes are not opened when the hydraulic fracture tip passes, they will remain closed and impermeable to flow. In this work a detailed and comprehensive evaluation of tip shear stresses and associated natural fracture or weakness plane shear is presented. From analytical work, the theoretical shear stresses from a fracture tip are first presented. The effect of fracture length, in-situ pore pressure, maximum horizontal remote stress, net pressure, natural fracture friction coefficient and the direction of natural fracture with respect to the hydraulic fracture on shear stimulation at the tip are calculated using the plane strain analytical solution of a 2-D fracture, and assuming simple linear coulomb friction law. Since slippage along natural fractures will locally violate the assumptions used in the analytical solutions and to incorporate the effect of weakness planes on stress-strain and displacement field, 2-D and 3-D finite element model (FEM) simulations are presented that build upon both the analytical and continuum solutions. FEM models are capable of numerically simulating the slippage through weakness planes by using contact elements. This advantage makes FEM tools very appropriate for synthetically generating microseismicity, which can then be evaluated for mode, focal mechanism, and magnitude. The results of the simulations highlight the critical parameters involved in shearing and opening cemented natural fractures in unconventionals - which is a critical component of stimulation and production optimization for these plays. According to the results, the ideal orientation of natural fractures with respect to hydraulic fracture from shear

  19. 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

  20. Hydraulic fracturing model based on the discrete fracture model and the generalized J integral

    NASA Astrophysics Data System (ADS)

    Liu, Z. Q.; Liu, Z. F.; Wang, X. H.; Zeng, B.

    2016-08-01

    The hydraulic fracturing technique is an effective stimulation for low permeability reservoirs. In fracturing models, one key point is to accurately calculate the flux across the fracture surface and the stress intensity factor. To achieve high precision, the discrete fracture model is recommended to calculate the flux. Using the generalized J integral, the present work obtains an accurate simulation of the stress intensity factor. Based on the above factors, an alternative hydraulic fracturing model is presented. Examples are included to demonstrate the reliability of the proposed model and its ability to model the fracture propagation. Subsequently, the model is used to describe the relationship between the geometry of the fracture and the fracturing equipment parameters. The numerical results indicate that the working pressure and the pump power will significantly influence the fracturing process.

  1. 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.

  2. Earthquakes Induced by Hydraulic Fracturing in Poland Township, Ohio

    NASA Astrophysics Data System (ADS)

    Skoumal, R.; Brudzinski, M. R.; Currie, B. S.

    2014-12-01

    Felt seismicity induced by hydraulic fracturing is very rare with only a handful of reported cases worldwide. Using an optimized multi-station cross-correlation template matching routine, 77 earthquakes were identified in Poland Township, Mahoning County, Ohio that were closely related spatially and temporally to active hydraulic fracturing operations. We identified earthquakes as small as M ~1 up to M 3, one of the largest earthquakes induced by hydraulic fracturing in the United States. These events all occurred 4-12 March 2014 and the rate decayed once the Ohio Department of Natural Resources issued a shutdown of hydraulic fracturing at a nearby well on 10 March. Using a locally derived velocity model and double difference relocation, the earthquake epicenters occurred during six stimulation stages along two horizontal well legs that were located ~0.8 km away. Nearly 100 stages in nearby wells at greater distances from the earthquake source region did not coincide with detected seismicity. During the sequence, hypocenters migrated ~600 m along an azimuth of 083 degrees defining a vertically oriented plane of seismicity close to the top of the Precambrian basement. The focal mechanism determined for the M 3 event had a vertically oriented left-lateral fault plane consistent with the earthquake distribution and the regional stress field. The focal mechanism, orientation, and depth of hypocenters were similar to that of the 2011 Youngstown earthquake sequence that occurred ~20 km away, but was correlated with wastewater injection instead of hydraulic fracturing. Considering the relatively large magnitude of these events and the b-value of 0.85, it appears the hydraulic fracturing induced slip along a pre-existing fault/fracture zone optimally oriented in the regional stress field.

  3. Impact of ductility on hydraulic fracturing in shales

    NASA Astrophysics Data System (ADS)

    Auton, Lucy; MacMinn, Chris

    2015-11-01

    Hydraulic fracturing is a method for extracting natural gas and oil from low-permeability rocks such as shale via the injection of fluid at high pressure. This creates fractures in the rock, providing hydraulic access deeper into the reservoir and enabling gas to be collected from a larger region of the rock. Fracture is the tensile failure of a brittle material upon reaching a threshold tensile stress, but some shales have a high clay content and may yield plastically before fracturing. Plastic deformation is the shear failure of a ductile material, during which stress relaxes through irreversible rearrangements of the particles of the material. Here, we investigate the impact of the ductility of shales on hydraulic fracturing. We consider a simple, axisymmetric model for radially outward fluid injection from a wellbore into a ductile porous rock. We solve the model semi-analytically at steady state, and numerically in general. We find that plastic deformation greatly reduces the maximum tensile stress, and that this maximum stress does not always occur at the wellbore. These results imply that hydraulic fracturing may fail in ductile rocks, or that the required injection rate for fracking may be much larger than the rate predicted from purely elastic models.

  4. 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

  5. Estimating the hydraulic conductivity of two-dimensional fracture networks

    NASA Astrophysics Data System (ADS)

    Leung, C. T.; Zimmerman, R. W.

    2010-12-01

    Most oil and gas reservoirs, as well as most potential sites for nuclear waste disposal, are naturally fractured. In these sites, the network of fractures will provide the main path for fluid to flow through the rock mass. In many cases, the fracture density is so high as to make it impractical to model it with a discrete fracture network (DFN) approach. For such rock masses, it would be useful to have recourse to analytical, or semi-analytical, methods to estimate the macroscopic hydraulic conductivity of the fracture network. We have investigated single-phase fluid flow through stochastically generated two-dimensional fracture networks. The centres and orientations of the fractures are uniformly distributed, whereas their lengths follow either a lognormal distribution or a power law distribution. We have considered the case where the fractures in the network each have the same aperture, as well as the case where the aperture of each fracture is directly proportional to the fracture length. The discrete fracture network flow and transport simulator NAPSAC, developed by Serco (Didcot, UK), is used to establish the “true” macroscopic hydraulic conductivity of the network. We then attempt to match this conductivity using a simple estimation method that does not require extensive computation. For our calculations, fracture networks are represented as networks composed of conducting segments (bonds) between nodes. Each bond represents the region of a single fracture between two adjacent intersections with other fractures. We assume that the bonds are arranged on a kagome lattice, with some fraction of the bonds randomly missing. The conductance of each bond is then replaced with some effective conductance, Ceff, which we take to be the arithmetic mean of the individual conductances, averaged over each bond, rather than over each fracture. This is in contrast to the usual approximation used in effective medium theories, wherein the geometric mean is used. Our

  6. 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

  7. 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.

  8. Fault activation by hydraulic fracturing in western Canada.

    PubMed

    Bao, Xuewei; Eaton, David W

    2016-12-16

    Hydraulic fracturing has been inferred to trigger the majority of injection-induced earthquakes in western Canada, in contrast to the Midwestern United States, where massive saltwater disposal is the dominant triggering mechanism. A template-based earthquake catalog from a seismically active Canadian shale play, combined with comprehensive injection data during a 4-month interval, shows that earthquakes are tightly clustered in space and time near hydraulic fracturing sites. The largest event [moment magnitude (MW) 3.9] occurred several weeks after injection along a fault that appears to extend from the injection zone into crystalline basement. Patterns of seismicity indicate that stress changes during operations can activate fault slip to an offset distance of >1 km, whereas pressurization by hydraulic fracturing into a fault yields episodic seismicity that can persist for months.

  9. Fault activation by hydraulic fracturing in western Canada

    NASA Astrophysics Data System (ADS)

    Bao, Xuewei; Eaton, David W.

    2016-12-01

    Hydraulic fracturing has been inferred to trigger the majority of injection-induced earthquakes in western Canada, in contrast to the Midwestern United States, where massive saltwater disposal is the dominant triggering mechanism. A template-based earthquake catalog from a seismically active Canadian shale play, combined with comprehensive injection data during a 4-month interval, shows that earthquakes are tightly clustered in space and time near hydraulic fracturing sites. The largest event [moment magnitude (MW) 3.9] occurred several weeks after injection along a fault that appears to extend from the injection zone into crystalline basement. Patterns of seismicity indicate that stress changes during operations can activate fault slip to an offset distance of >1 km, whereas pressurization by hydraulic fracturing into a fault yields episodic seismicity that can persist for months.

  10. 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

  11. Orbital blowout fractures: experimental evidence for the pure hydraulic theory.

    PubMed

    Rhee, John S; Kilde, John; Yoganadan, Narayan; Pintar, Frank

    2002-01-01

    The mechanism of injury and the underlying biomechanics of orbital blowout fractures remain controversial. The "hydraulic" theory proposes that a generalized increased orbital content pressure results in direct compression and fracturing of the thin orbital bone. To examine the pure hydraulic mechanism of injury by eliminating the factor of globe-to-wall contact and its possible contribution to fracture thresholds and patterns. Five fresh human cadaver specimens were used for the study. In each cadaver head, 1 orbit was prepared to mimic the normal physiologic condition by increasing the hypotony of the cadaver globe to normal intraocular pressure (15-20 mm Hg) with intravitreous injection of isotonic sodium chloride solution (saline). The second orbit served as a "hydraulic control," whereby the globe and orbital contents were exenterated and replaced by a saline-filled balloon at physiologic intraocular pressure. A 1-kg pendulum measuring 2.5 cm in diameter was used to strike the cadaver heads. Drop heights ranged from 0.2 m to 1.1 m (1960 mJ to 10 780 mJ energy). Each head was struck twice, once to each orbit. Direct visualization, high-speed videography, and computed tomographic scans were used to determine injury patterns at various heights between the 2 orbits. A fracture threshold was found at a drop height of 0.3 m (2940 mJ). Fracture severity and displacement increased with incremental increases in drop height (energy). Fracture displacement, with herniation of orbital contents, was obtained at heights above 0.5 m (4900 mJ). Isolated orbital floor fractures were obtained at lower heights, with medial wall fractures occurring in conjunction with floor fractures at higher energies (> or =6860 mJ). The globe intact side and balloon (hydraulic control) side showed nearly identical fracture patterns and levels of displacement at each drop height. This study provides support for the "hydraulic" theory and evidence against the role of direct globe-to-wall contact

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

    EPA Pesticide Factsheets

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

  13. Sulfide Generation by Dominant Halanaerobium Microorganisms in Hydraulically Fractured Shales

    PubMed Central

    Booker, Anne E.; Borton, Mikayla A.; Daly, Rebecca A.; Welch, Susan A.; Nicora, Carrie D.; Hoyt, David W.; Wilson, Travis; Purvine, Samuel O.; Wolfe, Richard A.; Sharma, Shikha; Mouser, Paula J.; Cole, David R.; Lipton, Mary S.; Wrighton, Kelly C.

    2017-01-01

    ABSTRACT Hydraulic fracturing of black shale formations has greatly increased United States oil and natural gas recovery. However, the accumulation of biomass in subsurface reservoirs and pipelines is detrimental because of possible well souring, microbially induced corrosion, and pore clogging. Temporal sampling of produced fluids from a well in the Utica Shale revealed the dominance of Halanaerobium strains within the in situ microbial community and the potential for these microorganisms to catalyze thiosulfate-dependent sulfidogenesis. From these field data, we investigated biogenic sulfide production catalyzed by a Halanaerobium strain isolated from the produced fluids using proteogenomics and laboratory growth experiments. Analysis of Halanaerobium isolate genomes and reconstructed genomes from metagenomic data sets revealed the conserved presence of rhodanese-like proteins and anaerobic sulfite reductase complexes capable of converting thiosulfate to sulfide. Shotgun proteomics measurements using a Halanaerobium isolate verified that these proteins were more abundant when thiosulfate was present in the growth medium, and culture-based assays identified thiosulfate-dependent sulfide production by the same isolate. Increased production of sulfide and organic acids during the stationary growth phase suggests that fermentative Halanaerobium uses thiosulfate to remove excess reductant. These findings emphasize the potential detrimental effects that could arise from thiosulfate-reducing microorganisms in hydraulically fractured shales, which are undetected by current industry-wide corrosion diagnostics. IMPORTANCE Although thousands of wells in deep shale formations across the United States have been hydraulically fractured for oil and gas recovery, the impact of microbial metabolism within these environments is poorly understood. Our research demonstrates that dominant microbial populations in these subsurface ecosystems contain the conserved capacity for the

  14. Sulfide Generation by Dominant Halanaerobium Microorganisms in Hydraulically Fractured Shales.

    PubMed

    Booker, Anne E; Borton, Mikayla A; Daly, Rebecca A; Welch, Susan A; Nicora, Carrie D; Hoyt, David W; Wilson, Travis; Purvine, Samuel O; Wolfe, Richard A; Sharma, Shikha; Mouser, Paula J; Cole, David R; Lipton, Mary S; Wrighton, Kelly C; Wilkins, Michael J

    2017-01-01

    Hydraulic fracturing of black shale formations has greatly increased United States oil and natural gas recovery. However, the accumulation of biomass in subsurface reservoirs and pipelines is detrimental because of possible well souring, microbially induced corrosion, and pore clogging. Temporal sampling of produced fluids from a well in the Utica Shale revealed the dominance of Halanaerobium strains within the in situ microbial community and the potential for these microorganisms to catalyze thiosulfate-dependent sulfidogenesis. From these field data, we investigated biogenic sulfide production catalyzed by a Halanaerobium strain isolated from the produced fluids using proteogenomics and laboratory growth experiments. Analysis of Halanaerobium isolate genomes and reconstructed genomes from metagenomic data sets revealed the conserved presence of rhodanese-like proteins and anaerobic sulfite reductase complexes capable of converting thiosulfate to sulfide. Shotgun proteomics measurements using a Halanaerobium isolate verified that these proteins were more abundant when thiosulfate was present in the growth medium, and culture-based assays identified thiosulfate-dependent sulfide production by the same isolate. Increased production of sulfide and organic acids during the stationary growth phase suggests that fermentative Halanaerobium uses thiosulfate to remove excess reductant. These findings emphasize the potential detrimental effects that could arise from thiosulfate-reducing microorganisms in hydraulically fractured shales, which are undetected by current industry-wide corrosion diagnostics. IMPORTANCE Although thousands of wells in deep shale formations across the United States have been hydraulically fractured for oil and gas recovery, the impact of microbial metabolism within these environments is poorly understood. Our research demonstrates that dominant microbial populations in these subsurface ecosystems contain the conserved capacity for the reduction of

  15. Analysis of Non-Planar Multi-Fracture Propagation from Layered-Formation Inclined-Well Hydraulic Fracturing

    NASA Astrophysics Data System (ADS)

    Liu, Zhiyuan; Jin, Yan; Chen, Mian; Hou, Bing

    2016-05-01

    Current research shows that layered formation barriers can have a significant impact on the extension of fracture height; however, there are few studies on inclined-well near-wellbore fracture propagation shapes and penetrating patterns near the interface. We performed a true triaxial hydraulic fracturing experiment to study the layered formation of inclined-well near-wellbore and interface fracture propagation geometries influenced by formation conditions and perforation schemes. The results revealed that horizontal stress differences, perforation phase angles, borehole azimuths, and interlayer minimum horizontal in situ stress differences were the main factors that controlled the fracture propagation geometry. Under the conditions of large differences in horizontal stress, large perforation phase angles, and large angles between the borehole azimuth and the maximum horizontal in situ stress azimuth, the near-wellbore cracks presented a single main fracture with a large number of secondary fractures; in addition, the main and secondary fractures changed orientations. With moderate horizontal stress differences and less severe angle parameters, the fracture propagation geometry was simplified, forming a single main fracture. When all three parameters were small, the cracks displayed multiple main or network fractures. The surface morphology of spatial distribution was complex and the seam surface was rough. Under a crossing condition, the pattern of the penetrating fractures was highly affected by the near-wellbore fractures when the interlayer minimum horizontal in situ stress differences were small. Under large interlayer minimum horizontal in situ stress differences, the interface fractures began to deflect and generate new branches. The fluctuation and increase in fracturing pressure was caused by the dispersion of the fracturing fluid flow from multi-fractures and the large number of seam surfaces.

  16. Onset of Hydraulic Fracture Initiation Monitored by Acoustic Emission and Volumetric Deformation Measurements

    NASA Astrophysics Data System (ADS)

    Stanchits, Sergey; Surdi, Aniket; Gathogo, Patrick; Edelman, Eric; Suarez-Rivera, Roberto

    2014-09-01

    In this paper, the results of laboratory studies of fracture initiation, early propagation and breakdown are reported. Three experiments were conducted on a low permeability sandstone block, loaded in a polyaxial test frame, to representative effective in situ stress conditions. The blocks were instrumented with acoustic emission (AE) and volumetric deformation sensors. In two experiments, fluids of different viscosity were injected into the wellbore, fluid injection was interrupted soon after the breakdown pressure had been reached. This allowed us to investigate hydraulic fracture initiation. In the third test, fracture initiation criteria were applied to stop hydraulic fracture propagation significantly earlier, prior to breakdown, and as it propagated a short distance from the wellbore. The analysis of AE results shows an increase in AE activity and a change in the AE spatial correlation, during the fracture initiation. This early stage of fracturing correlates strongly with the onset of rock volumetric deformation, and is confirmed by the analysis of ultrasonic transmission monitoring. The rock microstructure, after the test, was investigated by analysis of scanning electron microscope images. These indicated the development of leak-off zone near the wellbore and a dry hydraulic fracture at the farther distance from the wellbore.

  17. Impacts of Hydraulic Fracturing in California - AN Overview of a Comprehensive Science Assessment

    NASA Astrophysics Data System (ADS)

    Birkholzer, J. T.; Long, J. C. S.; Feinstein, L.; Stringfellow, W. T.; Jordan, P. D.; Varadharajan, C.; Foxall, W.; Dobson, P. F.; Houseworth, J. E.

    2015-12-01

    In 2013, California's Senate Bill 4 required an independent science study to assess current and potential future hydraulic fracturing practices in California, and to evaluate potential impacts on water, air, seismicity, ecological systems, and health. The study, completed in July 2015, found that hydraulic fracturing currently supports about one quarter of California's oil production, and is expected to continue to do so in the near future. California's experience with hydraulic fracturing differs from that in other states because operators mostly conduct relatively shallow stimulations in relatively high-permeability reservoirs. The upside of this is that operations use relatively little water, but the downside is that in a few locations, fractures could extend into protected groundwater. The study also found that direct impacts of hydraulic fracturing appear small but have not been fully investigated in California. These direct impacts all stem from the use of stimulation chemicals and the study calls for precautionary limits on chemical use. Indirect impacts, which are not directly attributable to the stimulation activity but rather caused by oil and gas production enabled by stimulation, are likely more important. For example, underground injection of produced water from a hydraulically fractured reservoir causes problems common to all oil and gas production, such as the risk of inducing an earthquake or causing groundwater contamination. To date, there have been no reported cases of induced seismicity associated with produced water injection in California. However, it is difficult to distinguish California's frequent natural earthquakes from those possibly caused by water injection. California also disposes of produced water from all oil and gas production in percolation ponds and injects some of this water into protected aquifers. These are serious issues, often tagged to hydraulic fracturing but actually common to all oil and gas production.

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

    PubMed

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

    2015-07-01

    A U.S. map of water volumes used to hydraulically fracture oil and gas wells, 2011-2014Hydraulic fracturing water volumes differ regionally across the U.S.Discussion of variation in water use and potential environmental implications.

  19. Characteristic ruptures of micro-seismic hydraulic fractures

    NASA Astrophysics Data System (ADS)

    Viegas, G. F.; Smith-Boughner, L.; Urbancic, T.; Baig, A. M.

    2015-12-01

    Hydraulic fracturing is a process that involves the injection of fluids above lithostatic pressures to increase permeability of rocks at depth. During the fracturing process thousands of micro-seismic events are generated as the fracture front propagates outwards from the injection point. Sand or glass beads are frequently injected later in the stage to prop the fractures and maintain flow paths open. Because injection progresses in time and space changing the in situ characteristics the generated seismic events show a combination of seismic signatures between two end members: Coulomb stress transfer on favorably oriented fractures and fluid-induced tensile fractures. In this study we investigate the failure process of ~27,000 micro-seismic fractures induced during a hydraulic fracturing shale completion program. Our goal is to identify spatial and temporal distribution of families of events with similar characteristic rupture behaviors, for different injection phases and relative locations based on either rock formation, depth, source mechanism, fracture plane orientation, stress drop, etc., to classify distinct dynamic failure processes. In our analysis we estimate static and dynamic stress drop, radiated energy, seismic efficiency, moment tensor, fracture plane orientation, slip direction and rupture velocity. On average, the micro-seismic events have low radiated energy, low dynamic stress and low seismic efficiency failing in overshoot mode, with slow rupture velocities consistent with failure on fluid lubricated fractures with decreased friction resistance. Slip is accommodated on fracture planes with orientations dominated by the rock fabric and not always optimally oriented to the regional stress field. Subtle source characteristic differences can be identified: Events occurring in deeper formations tend to have faster rupture velocities and are more efficient in radiating energy. Variations in rupture velocity tend to correlate with variation in depth

  20. A Fracture Decoupling Experiment

    NASA Astrophysics Data System (ADS)

    Stroujkova, A. F.; Bonner, J. L.; Leidig, M.; Ferris, A. N.; Kim, W.; Carnevale, M.; Rath, T.; Lewkowicz, J.

    2012-12-01

    Multiple observations made at the Semipalatinsk Test Site suggest that conducting nuclear tests in the fracture zones left by previous explosions results in decreased seismic amplitudes for the second nuclear tests (or "repeat shots"). Decreased seismic amplitudes reduce both the probability of detection and the seismically estimated yield of a "repeat shot". In order to define the physical mechanism responsible for the amplitude reduction and to quantify the degree of the amplitude reduction in fractured rocks, Weston Geophysical Corp., in collaboration with Columbia University's Lamont Doherty Earth Observatory, conducted a multi-phase Fracture Decoupling Experiment (FDE) in central New Hampshire. The FDE involved conducting explosions of various yields in the damage/fracture zones of previously detonated explosions. In order to quantify rock damage after the blasts we performed well logging and seismic cross-hole tomography studies of the source region. Significant seismic velocity reduction was observed around the source regions after the initial explosions. Seismic waves produced by the explosions were recorded at near-source and local seismic networks, as well as several regional stations throughout northern New England. Our analysis confirms frequency dependent seismic amplitude reduction for the repeat shots compared to the explosions in un-fractured rocks. The amplitude reduction is caused by pore closing and/or by frictional losses within the fractured media.

  1. Potential Relationships Between Hydraulic Fracturing and Drinking Water Resources

    EPA Science Inventory

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

  2. Potential Relationships Between Hydraulic Fracturing and Drinking Water Resources

    EPA Science Inventory

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

  3. 78 FR 55253 - Notification of Public Teleconference of the Hydraulic Fracturing Research Advisory Panel

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-10

    ... information related to hydraulic fracturing and drinking water resources. DATES: The public teleconference... comments from the public on new and emerging information related to hydraulic fracturing and drinking water... between hydraulic fracturing and drinking water. In March 2013, the SAB Staff Office formed an SAB panel...

  4. Hydraulic Fracturing in Zoned Earth and Rockfill Dams: A Report of an Investigation.

    DTIC Science & Technology

    The investigation involves two parts: first, an experimental investigation to study the phenomenon of hydraulic fracturing under carefully...be reduced sufficiently by arching so that hydraulic fracturing can occur. Analyses were also performed to examine the effectiveness of various countermeasures which can reduce the arching and the likelihood of hydraulic fracturing .

  5. Modelling of hydraulic fracture propagation in inhomogeneous poroelastic medium

    NASA Astrophysics Data System (ADS)

    Baykin, A. N.; Golovin, S. V.

    2016-06-01

    In the paper a model for description of a hydraulic fracture propagation in inhomogeneous poroelastic medium is proposed. Among advantages of the presented numerical algorithm, there are incorporation of the near-tip analysis into the general computational scheme, account for the rock failure criterion on the base of the cohesive zone model, possibility for analysis of fracture propagation in inhomogeneous reservoirs. The numerical convergence of the algorithm is verified and the agreement of our numerical results with known solutions is established. The influence of the inhomogeneity of the reservoir permeability to the fracture time evolution is also demonstrated.

  6. 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.

  7. Analytic crack solutions for tilt fields around hydraulic fractures

    NASA Astrophysics Data System (ADS)

    Warpinski, Norman R.

    2000-10-01

    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 two-dimensional (2-D), penny-shaped, and 3-D-elliptic cracks and a 2-D-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.

  8. 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.

  9. Scale and Time Effects in Hydraulic Fracturing.

    DTIC Science & Technology

    1984-07-01

    Results on Teton Dam Silt Test Groove Dry Water Fracturing No. Size Density Content Pressure b d t/m 3 %kg/cm 2 in. in. - IG2 3. 1.51.5920.43.2 G3 2.0...a loose zone through which water pressures were applied. • 111 Table 5.2 Summary of Type IV Test Results on Teton Dam Silt Series Test Slot Dry Water Fracturing...Series Test Slot Dry Water Fracturing No. No. Width Density Content Pressure in. t/m 3 % kg/cm 2 S12 0.125 1.60 19.1 3.6 S13 0.25 1.60 19.5 3.9 I S14

  10. Laboratory investigation on the effect of in situ stresses on hydraulic fracture containment

    SciTech Connect

    Warpinski, N. R.; Clark, J. A.; Schmidt, R. A.; Huddle, C. W.

    1981-01-01

    Laboratory experiments have been conducted to determine the effect of in situ stress variations on hydraulic fracture containment. Fractures were initiated in layered rock samples with prescribed stress variations, and fracture growth characteristics were determined as a function of stress levels. Stress contrasts of 2-3 MPa were found to be sufficient to restrict fracture growth in laboratory samples of Nevada tuff and Tennessee and Nugget sandstones. The required stress level was found not to depend on mechanical rock properties. However, permeability and the resultant pore pressure effects were found to be important. Tests conducted at bimaterial interfaces between Nugget and Tennessee sandstone show that the resultant stresses set up near the interface due to the applied overburden stress affect the fracture behavior in the same way as the applied confining stresses. These results provide a guideline for determining the in situ stress contrast necessary to contain a fracture in a field treatment.

  11. Leakage losses from a hydraulic fracture and fracture propagation

    NASA Astrophysics Data System (ADS)

    Johnson, Robert E.; Gustafson, Craig W.

    1988-11-01

    The fluid mechanics of viscous fluid injection into a fracture embedded in a permeable rock formation is studied. Coupling between flow in the fracture and flow in the rock is retained. The analysis is based on a perturbation scheme that assumes the depth of penetration of the fluid into the rock is small compared to the characteristic length w30/k, where w0 is the characteristic crack width and k is the permeability. This restriction, however, is shown to be minor. The spatial dependence of the leakage rate per unit length from the fracture is found to be linear, decreasing from the well bore to the fracture tip where it vanishes. The magnitude of the leakage rate per unit length is found to decay in time as t-1/3 if the injection rate at the well bore is constant, and as t-1/2 if the well bore pressure is held constant. The results cast considerable doubt on the validity of Carter's well-known leakage formula (Drilling Prod. Prac. API 1957, 261) derived from a one-dimensional theory. Using the simple fracture propagation model made popular by Carter, the present work also predicts that the fracture grows at a rate proportional to t1/3 for a fixed well bore injection rate and a rate proportional to t1/4 for a fixed well bore pressure.

  12. Hydraulic tomography offers improved imaging of heterogeneity in fractured rocks.

    PubMed

    Illman, Walter A

    2014-01-01

    Fractured rocks have presented formidable challenges for accurately predicting groundwater flow and contaminant transport. This is mainly due to our difficulty in mapping the fracture-rock matrix system, their hydraulic properties and connectivity at resolutions that are meaningful for groundwater modeling. Over the last several decades, considerable effort has gone into creating maps of subsurface heterogeneity in hydraulic conductivity (K) and specific storage (Ss ) of fractured rocks. Developed methods include kriging, stochastic simulation, stochastic inverse modeling, and hydraulic tomography. In this article, I review the evolution of various heterogeneity mapping approaches and contend that hydraulic tomography, a recently developed aquifer characterization technique for unconsolidated deposits, is also a promising approach in yielding robust maps (or tomograms) of K and Ss heterogeneity for fractured rocks. While hydraulic tomography has recently been shown to be a robust technique, the resolution of the K and Ss tomograms mainly depends on the density of pumping and monitoring locations and the quality of data. The resolution will be improved through the development of new devices for higher density monitoring of pressure responses at discrete intervals in boreholes and potentially through the integration of other data from single-hole tests, borehole flowmeter profiling, and tracer tests. Other data from temperature and geophysical surveys as well as geological investigations may improve the accuracy of the maps, but more research is needed. Technological advances will undoubtedly lead to more accurate maps. However, more effort should go into evaluating these maps so that one can gain more confidence in their reliability. © 2013, National Ground Water Association.

  13. Periodic Hydraulic Tests in a Bedrock Fracture Network

    NASA Astrophysics Data System (ADS)

    Cole, M. C.; Becker, M.; Ciervo, C.

    2016-12-01

    Better understanding of groundwater flow through bedrock fracture networks is critical for the emerging field of enhanced geothermal systems, as well as traditional hydrogeologic characterization. Periodic hydraulic testing has shown promise for its sensitivity to local heterogeneity and, therefore, may provide useful information about flow channelization and short circuiting. Unlike conventional steady-rate pumping or injection tests, periodic tests create a disturbance such that heads in the pumping and observation wells are always in the transient state. The volume of hydraulic influence of the oscillating flow increases with period of oscillation. Thus, different portions of the formation may be interrogated even with a single well pair. We recently performed periodic pumping tests at the Mirror Lake experimental fractured rock hydrology field site in the Northeastern United States. Head in one well was oscillated while heads in five monitoring wells 30 to 60 m away were monitored. Head oscillation was accomplished through alternating injection and pumping from a surface tank and pressure was measured using a network of transducers in zones isolated by pneumatic packers. Periodicity of the induced signal was varied in order to investigate different volumes of the formation. Drawdown data from the monitoring wells were digitally filtered, which enabled use of responses that were too small or noisy for curve fitting methods. As expected, the volume of hydraulic influence increased with period, but well response was not strictly a function of distance from the source well. This anomalous response is attributed to variation in fracture network hydraulic connectivity. The ability to vary the effective penetration distance of hydraulic influence provided more information about network connectivity than from a constant rate pumping test. Estimates of hydraulic parameters displayed a decreasing trend with period length, which has been noted in previous periodic tests

  14. 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.

  15. Hydraulic Tomography in Fractured Sedimentary Rocks to Estimate High-Resolution 3-D Distribution of Hydraulic Conductivity

    NASA Astrophysics Data System (ADS)

    Tiedeman, C. R.; Barrash, W.; Thrash, C. J.; Patterson, J.; Johnson, C. D.

    2016-12-01

    Hydraulic tomography was performed in a 100 m2 by 20 m thick volume of contaminated fractured mudstones at the former Naval Air Warfare Center (NAWC) in the Newark Basin, New Jersey, with the objective of estimating the detailed distribution of hydraulic conductivity (K). Characterizing the fine-scale K variability is important for designing effective remediation strategies in complex geologic settings such as fractured rock. In the tomography experiment, packers isolated two to six intervals in each of seven boreholes in the volume of investigation, and fiber-optic pressure transducers enabled collection of high-resolution drawdown observations. A hydraulic tomography dataset was obtained by conducting multiple aquifer tests in which a given isolated well interval was pumped and drawdown was monitored in all other intervals. The collective data from all tests display a wide range of behavior indicative of highly heterogeneous K within the tested volume, such as: drawdown curves for different intervals crossing one another on drawdown-time plots; unique drawdown curve shapes for certain intervals; and intervals with negligible drawdown adjacent to intervals with large drawdown. Tomographic inversion of data from 15 tests conducted in the first field season focused on estimating the K distribution at a scale of 1 m3 over approximately 25% of the investigated volume, where observation density was greatest. The estimated K field is consistent with prior geologic, geophysical, and hydraulic information, including: highly variable K within bedding-plane-parting fractures that are the primary flow and transport paths at NAWC, connected high-K features perpendicular to bedding, and a spatially heterogeneous distribution of low-K rock matrix and closed fractures. Subsequent tomographic testing was conducted in the second field season, with the region of high observation density expanded to cover a greater volume of the wellfield.

  16. Intermediate-Scale Hydraulic Fracturing in a Deep Mine - kISMET Project Summary 2016

    SciTech Connect

    Oldenburg, C. M.; Dobson, P. F.; Wu, Y.; Cook, P. J.; Kneafsey, T. J.; Nakagawa, S.; Ulrich, C.; Siler, D. L.; Guglielmi, Y.; Ajo-Franklin, J. B.; Rutqvist, J.; Daley, T. M.; Birkholzer, J. T.; Wang, H. F.; Lord, N. E.; Haimson, B. C.; Sone, H.; Vigilante, P.; Roggenthen, W. M.; Doe, T. W.; Lee, M. Y.; Ingraham, M.; Huang, H.; Mattson, E. D.; Zhou, J.; Johnson, T. J.; Morris, J. P.; White, J. A.; Johnson, P. A.; Coblentz, D. D.; Heise, J.; Zoback, M. D.

    2016-11-04

    In support of the U.S. DOE SubTER Crosscut initiative, we established a field test facility in a deep mine and designed and carried out in situ hydraulic fracturing experiments in the crystalline rock at the site to characterize the stress field, understand the effects of rock fabric on fracturing, and gain experience in monitoring using geophysical methods. The project also included pre- and post-fracturing simulation and analysis, laboratory measurements and experiments, and we conducted an extended analysis of the local stress state using previously collected data. Some of these activities are still ongoing. The kISMET (permeability (k) and Induced Seismicity Management for Energy Technologies) experiments meet objectives in SubTER’s “stress” pillar and the “new subsurface signals” pillar. The kISMET site was established in the West Access Drift of SURF 4850 ft (1478 m) below ground (on the 4850L) in phyllite of the Precambrian Poorman Formation. We drilled and cored five near-vertical boreholes in a line on 3 m spacing, deviating the two outermost boreholes slightly to create a five-spot pattern around the test borehole centered in the test volume at ~1528 m (5013 ft). Laboratory measurements of core from the center test borehole showed P-wave velocity heterogeneity along each core indicating strong, fine-scale (~1 cm or smaller) changes in the mechanical properties of the rock. The load-displacement record on the core suggests that the elastic stiffness is anisotropic. Tensile strength ranges between 3-7.5 MPa and 5-12 MPa. Permeability measurements are planned, as are two types of laboratory miniature hydraulic fracturing experiments to investigate the importance of rock fabric (anisotropy and heterogeneity) on near-borehole hydraulic fracture generation. Pre-fracturing numerical simulations with INL’s FALCON discrete element code predicted a fracture radius of 1.2 m for a corresponding injection volume of 1.2 L for the planned fractures, and

  17. 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.

  18. Phase-field modeling of hydraulic fracture

    NASA Astrophysics Data System (ADS)

    Wilson, Zachary A.; Landis, Chad M.

    2016-11-01

    In this work a theoretical framework implementing the phase-field approach to fracture is used to couple the physics of flow through porous media and cracks with the mechanics of fracture. The main modeling challenge addressed in this work, which is a challenge for all diffuse crack representations, is on how to allow for the flow of fluid and the action of fluid pressure on the aggregate within the diffuse damage zone of the cracks. The theory is constructed by presenting the general physical balance laws and conducting a consistent thermodynamic analysis to constrain the constitutive relationships. Constitutive equations that reproduce the desired responses at the various limits of the phase-field parameter are proposed in order to capture Darcy-type flow in the intact porous medium and Stokes-type flow within open cracks. A finite element formulation for the solution of the governing model equations is presented and discussed. Finally, the theoretical and numerical model is shown to compare favorably to several important analytical solutions. More complex and interesting calculations are also presented to illustrate some of the advantageous features of the approach.

  19. 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.

  20. Influence of Natural Fractures Cohesive Properties on Geometry of Hydraulic Fracture Networks

    NASA Astrophysics Data System (ADS)

    Gonzalez-Chavez, M. A.; Dahi Taleghani, A.; Puyang, P.

    2014-12-01

    An integrated modeling methodology is proposed to analyze hydraulic fracturing jobs in the presence of the natural fracture network in the formation. A propagating hydraulic fracture may arrest, cross, or diverts into a preexisting natural crack depending on fracture properties of rock and magnitude and direction of principal rock stresses. Opening of natural fractures during fracturing treatment could define the effectiveness of the stimulation technique. Here, we present an integrated methodology initiated with lab scale fracturing properties using Double Cantilever Beam tests (DCB) to determine cohesive properties of rock and natural fractures. We used cohesive finite element models to reproduce laboratory results to verify the numerical model for the interaction of the hydraulic fracture and individual cemented natural fractures. Based on the initial investigations, we found out that distribution of pre-existing natural fractures could play a significant role in the final geometry of the induced fracture network; however in practice, there is not much information about the distribution of natural fractures in the subsurface due to the limited access. Hence, we propose a special optimization scheme to generate natural fracture geometry from the location of microseismic events. Accordingly, the criteria of evaluating the fitness of natural fracture realizations is defined as the total minimum distance squares of all microseismic events, which is the sum of minimum square distance for all microseismic events. Moreover, an additional constraint in this problem is that we need to set a minimum distance between fracture grids. Using generated natural fracture realizations, forward field-scale simulations are implemented using cohesive finite element analysis to find the best match with the recorded bottomhole pressure. To show the robustness of the proposed workflow for real field problem, we implemented this technique on available data from several well Chicontepec

  1. Scintillation gamma spectrometer for analysis of hydraulic fracturing waste products.

    PubMed

    Ying, Leong; O'Connor, Frank; Stolz, John F

    2015-01-01

    Flowback and produced wastewaters from unconventional hydraulic fracturing during oil and gas explorations typically brings to the surface Naturally Occurring Radioactive Materials (NORM), predominantly radioisotopes from the U238 and Th232 decay chains. Traditionally, radiological sampling are performed by sending collected small samples for laboratory tests either by radiochemical analysis or measurements by a high-resolution High-Purity Germanium (HPGe) gamma spectrometer. One of the main isotopes of concern is Ra226 which requires an extended 21-days quantification period to allow for full secular equilibrium to be established for the alpha counting of its progeny daughter Rn222. Field trials of a sodium iodide (NaI) scintillation detector offers a more economic solution for rapid screenings of radiological samples. To achieve the quantification accuracy, this gamma spectrometer must be efficiency calibrated with known standard sources prior to field deployments to analyze the radioactivity concentrations in hydraulic fracturing waste products.

  2. Experimental validation of microseismic emissions from a controlled hydraulic fracture in a synthetic layered medium

    NASA Astrophysics Data System (ADS)

    Roundtree, Russell

    A controlled hydraulic fracture experiment was performed on two medium sized (11" x 11" x 15") synthetic layered blocks of low permeability, low porosity Lyons sandstone sandwiched between cement. The purpose of the research was to better understand and characterize the fracture evolution as the fracture tip impinged upon the layer boundaries between the well bonded layers. It is also one of the first documented uses of passive microseismic used in a laboratory environment to characterize hydraulic fracturing. A relatively low viscosity fluid of 1000 centipoise, compared to properly scaled previous work (Casas 2005, and Athavale 2007), was pumped at a constant rate of 10 mL/minute through a steel cased hole landed and isolated in the sandstone layer. Efforts were made to contain the hydraulic fracture within the confines of the rock specimen to retain the created hydraulic fracture geometry. Two identical samples and treatment schedules were created and differed only in the monitoring system used to characterize the microseismic activity during the fracture treatment. The first block had eight embedded P-wave transducers placed in the sandstone layer to record the passive microseismic emissions and localize the location and time of the acoustic event. The second block had six compressional wave transducers and twelve shear wave transducers embedded in the sandstone layer of the block. The intention was to record and process the seismic data using conventional P-wave to S-wave difference timing techniques well known in industry. While this goal ultimately not possible due to the geometry of the receiver placements and the limitations of the Vallene acquisition processing software, the data received and the events localized from the 18 transducer test were of much higher numbers and quality than on the eight transducer test. This experiment proved conclusively that passive seismic emission recording can yield positive results in the laboratory. Just as in the field

  3. Mapping Three-Dimensional Hydraulic Heterogeneities in Fractured Granite through Transient Hydraulic Tomography

    NASA Astrophysics Data System (ADS)

    Zha, Y.; Yeh, T. C. J.; Illman, W. A.; Tanaka, T.; Bruines, P.; Onoe, H.; Saegusa, H.; Mao, D.

    2014-12-01

    Between 2005 and 2010, three independent sequential pumping tests were conducted in a fractured granite formation at the Mizunami Underground Research Laboratory (MIU) site in central Japan. Additional pumping operations were undertaken in the course of excavation of two vertical shafts at the site. During these events, groundwater responses were monitored in multiple observation intervals in several shallow and deep boreholes. In this study, we first visually inspected these responses at all observation intervals induced by each pumping event. We found that some intervals at far-distance boreholes showed rapid, and strong responses, while intervals of boreholes near the vicinity of the pumping locations showed little responses. Moreover, the locations of the rapid and slow responses varied with pumping locations. This preliminary inspection suggested that some boreholes are likely connected via fractures and some are separated by flow barrier(s). Subsequently, these drawdown data sets were analyzed using a three-dimensional (3-D) transient hydraulic tomography (HT) code to estimate the hydraulic conductivity (K) and specific storage (Ss) distributions. Results of the analysis depicted several large-scale high K and low K zones and some small-scale features at the MIU site. The locations of these high and low K estimates explain the observed fast and slow groundwater responses, and corroborate with the locations of fractures and fault zones estimated based on geologic information. The HT analysis nevertheless provides a detailed description of the hydraulic characteristics of the fracture and fault zones.

  4. A Geochemical Framework for Evaluating Shale-Hydraulic Fracture Fluid Interactions

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    The development of shale oil and gas reservoirs has increased dramatically due to the application of hydraulic fracturing techniques. Fracture fluids contain dissolved oxygen and numerous chemical additives [1] that are out of equilibrium with the reducing conditions in shale reservoirs and could react extensively with shale minerals and alter porosity. Yet, the complex dissolution-precipitation reactions in shales along with the poorly constrained characteristics of many fracture fluid additives hinder predictive modeling based on established reaction kinetics and thermodynamic constants [2]. Here, we are developing a reaction framework to better predict reaction progress and porosity evolution upon exposure of shales to hydraulic fracturing fluids. To this end, the reactive transport model CrunchFlow [3] was applied to the results of batch reactor experiments containing shales of different mineralogical and organic compositions exposed to simulated fracturing fluid. Despite relatively good agreement between modeled and experimental data for pH and aqueous Ca concentrations, which are strongly governed by carbonate dissolution, the model is presently unable to reproduce observed trends in aqueous Fe concentration. This is largely attributable to the dearth of thermodynamic data for certain fracture fluid components and the complex interactions between multiple Fe-bearing mineral phases. Experimental results revealed that the presence of organic fracture fluid components strongly influenced the precipitation of Fe-bearing phases, which are speculated to coat fracture fluid polymers that formed in the reactors. The incorporation of these effects in our reactive transport model will permit improved prediction of reservoir permeability evolution and metal release during hydraulic fracturing operations. [1] Stringfellow et al. (2014) J. Hazard. Mater. [2] Carroll et al. (2013) Environ. Sci. Technol. [3] Steefel and Maher (2009) Rev. Mineral. Geochem.

  5. 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.

  6. Long-period long-duration seismic events during hydraulic fracturing: Implications for tensile fracture development

    NASA Astrophysics Data System (ADS)

    Hu, Hongru; Li, Aibing; Zavala-Torres, Ricardo

    2017-05-01

    Long-period long-duration (LPLD) seismic events are observed from a microseismic data set acquired by surface receivers in the Eagle Ford Shale. These events are characterized by low frequencies of 10-60 Hz and long durations of 30-60 s. The seismograms are dominated with P waves, and the frequency spectra have peaks at several isolated frequencies, similar to volcanic tremors. The LPLD events are located close to the horizontal hydraulic treatment well and migrate away from the well with time. These observations suggest that the LPLD events are related to hydraulic fracturing and are possibly caused by the jerky opening and resonance of fluid-filled cracks. Imaging this type of LPLD events can potentially map fluid flow and tensile fracture development during hydraulic fracturing.

  7. 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.

  8. Scale-dependence of hydraulic properties observed in fractured sedimentary rocks through large scale pumping test

    NASA Astrophysics Data System (ADS)

    Guihéneuf, N.; Dausse, A.; de Dreuzy, J. R.; Cherry, J. A.; Parker, B. L.

    2016-12-01

    Predicting flow in fractured reservoirs remains challenging as it highly depends on hydraulic connectivity of fractures which can vary from point to point. Classical pumping experiments conducted in fractured reservoirs often display fractional flow and anomalous slow diffusion due to bottlenecks or dead zones, characteristic of heterogeneity. In order to investigate reservoir properties at a contaminated site in the Simi Hills (South California, USA), composed by sandstones (dominant calcite cement) inter-bedded with fine-grained formations (shales, siltstones and mudstones), a large scale pumping test was performed in a major fault over 151 days. Deconvolution was applied first to remove the effect of variable flow rates and obtain constant-rate responses of the reservoir. Next, pressure-transients were analyzed both in time and space to get flow dimension, n, through the pressure derivative and extract the anomalous diffusion exponent, dw, as well as the fractal dimension, df. Analysis revealed at least two kinds of responses characterized by flow dimensions of 0.08 and 0.39 and anomalous diffusion exponents of 2.16 and 2.93, respectively. These properties, which can be related to major geological structures (i.e. major faults and surrounding fractures network), shows decreasing hydraulic properties (transmissivity, T, and storativity, S), and consequently, decreasing hydraulic connectivity, with increasing scale of investigation. In particular, the major fault (n = 0.39 ; dw = 2.93) shows a relationship of about T S3 with T r-1.36 and S r-0.43, consistent with flow within a fracture, while the surrounding fractures network (n = 0.08 ; dw = 2.16) displays a relationship which follow T S with T r-1.07 and S r-0.91. This scale-dependence of hydraulic properties may help improve groundwater flow prediction in such fractured reservoirs and could be taken into account for long-term transport of contaminants at this site.

  9. 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.

  10. 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.

  11. A reassessment of in situ stress determination by hydraulic fracturing

    NASA Astrophysics Data System (ADS)

    Lakirouhani, A.; Detournay, E.; Bunger, A. P.

    2016-06-01

    Estimating in situ stress based on hydraulic fracturing data typically depends on interpretation of the breakdown, secondary breakdown (`reopening') and shut-in pressure. While it has been recognized that the near-wellbore stress field should be taken into account and that the compressibility of the injection system and the viscous flow of the fluid can diminish the accuracy of stress estimates, these issues have not been well quantified. A coupled numerical model that includes the compressibility of the injection system and the flow of a viscous fluid in a plane-strain hydraulic fracture extending from a wellbore, in an impermeable rock, and in the presence of a non-isotropic in situ stress field provides a basic tool for estimating the order of the error associated with hydraulic fracturing stress measurements under non-ideal conditions. The main findings of this work are model-based guidelines on the values of relevant dimensionless parameter groups to ensure sufficient accuracy of stress estimates that use idealized models. When these guidelines cannot be met under field conditions, the model can be further applied to obtain first-order corrections that account for compressibility, viscosity and near-wellbore effects.

  12. Experimental investigation of the hydraulic and heat-transfer properties of artificially fractured granite.

    PubMed

    Luo, Jin; Zhu, Yongqiang; Guo, Qinghai; Tan, Long; Zhuang, Yaqin; Liu, Mingliang; Zhang, Canhai; Xiang, Wei; Rohn, Joachim

    2017-01-05

    In this paper, the hydraulic and heat-transfer properties of two sets of artificially fractured granite samples are investigated. First, the morphological information is determined using 3D modelling technology. The area ratio is used to describe the roughness of the fracture surface. Second, the hydraulic properties of fractured granite are tested by exposing samples to different confining pressures and temperatures. The results show that the hydraulic properties of the fractures are affected mainly by the area ratio, with a larger area ratio producing a larger fracture aperture and higher hydraulic conductivity. Both the hydraulic apertureand the hydraulic conductivity decrease with an increase in the confining pressure. Furthermore, the fracture aperture decreases with increasing rock temperature, but the hydraulic conductivity increases owing to a reduction of the viscosity of the fluid flowing through. Finally, the heat-transfer efficiency of the samples under coupled hydro-thermal-mechanical conditions is analysed and discussed.

  13. Experimental investigation of the hydraulic and heat-transfer properties of artificially fractured granite

    PubMed Central

    Luo, Jin; Zhu, Yongqiang; Guo, Qinghai; Tan, Long; Zhuang, Yaqin; Liu, Mingliang; Zhang, Canhai; Xiang, Wei; Rohn, Joachim

    2017-01-01

    In this paper, the hydraulic and heat-transfer properties of two sets of artificially fractured granite samples are investigated. First, the morphological information is determined using 3D modelling technology. The area ratio is used to describe the roughness of the fracture surface. Second, the hydraulic properties of fractured granite are tested by exposing samples to different confining pressures and temperatures. The results show that the hydraulic properties of the fractures are affected mainly by the area ratio, with a larger area ratio producing a larger fracture aperture and higher hydraulic conductivity. Both the hydraulic apertureand the hydraulic conductivity decrease with an increase in the confining pressure. Furthermore, the fracture aperture decreases with increasing rock temperature, but the hydraulic conductivity increases owing to a reduction of the viscosity of the fluid flowing through. Finally, the heat-transfer efficiency of the samples under coupled hydro-thermal-mechanical conditions is analysed and discussed. PMID:28054594

  14. Experimental investigation of the hydraulic and heat-transfer properties of artificially fractured granite

    NASA Astrophysics Data System (ADS)

    Luo, Jin; Zhu, Yongqiang; Guo, Qinghai; Tan, Long; Zhuang, Yaqin; Liu, Mingliang; Zhang, Canhai; Xiang, Wei; Rohn, Joachim

    2017-01-01

    In this paper, the hydraulic and heat-transfer properties of two sets of artificially fractured granite samples are investigated. First, the morphological information is determined using 3D modelling technology. The area ratio is used to describe the roughness of the fracture surface. Second, the hydraulic properties of fractured granite are tested by exposing samples to different confining pressures and temperatures. The results show that the hydraulic properties of the fractures are affected mainly by the area ratio, with a larger area ratio producing a larger fracture aperture and higher hydraulic conductivity. Both the hydraulic apertureand the hydraulic conductivity decrease with an increase in the confining pressure. Furthermore, the fracture aperture decreases with increasing rock temperature, but the hydraulic conductivity increases owing to a reduction of the viscosity of the fluid flowing through. Finally, the heat-transfer efficiency of the samples under coupled hydro-thermal-mechanical conditions is analysed and discussed.

  15. Three Dimensional Stress Maps of Dynamic Hydraulic Fracture within Heavily Cross-Linked Hydrogels

    NASA Astrophysics Data System (ADS)

    Steinhardt, W.; Rubinstein, S.; Weitz, D.

    2014-12-01

    Hydraulic fractures (HFs) of oil and gas shales occur miles underground, below complex, layered heterogeneous rocks making any measurements of their dynamics, extent, or structure difficult to impossible. As such, model lab systems such as blocks of PMMA or rocks fractured with air or fluid (Bunger et al [2013], Alpern et al [2012]) are studied in order to understand the intricacies of HFs. However, due to the extreme energies necessary to fracture these materials the experiments are difficult, have little flexibility in the materials, and offer little no measure of the dynamics of the fracture. Heavily cross-linked hydrogels have been shown to be a good model to study brittle fracture (Livne et al [2004]). I will discuss a new system, which we have developed to study HFs within tough hydrogels which have the benefits of having highly tunable rheology, being optically clear, and having slower fracture speeds and breakdown pressures. By embedding fluorescent tracer particles within the gel together with laser sheet microscopy, we obtain the three dimensional stress and strain maps of the zone surrounding a hydraulic fracture tip.

  16. 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.

  17. Effects of skin and hydraulic fractures on SVE wells.

    PubMed

    Bradner, Graham C; Murdoch, Lawrence C

    2005-05-01

    Soil vapor extraction (SVE) systems are intended to cause substantial volumes of air to flow through the subsurface with the purpose of removing volatile contaminants. The effectiveness of SVE can be influenced by any effect that changes the specific gas capacity (discharge as a function of vacuum) of a well. Skins of low permeability material enveloping a well bore are widely recognized to affect the performance of wells used to recover water, natural gas, or petroleum, and skin can also significantly diminish the performance of an SVE well. Skins a few mm thick consisting of material whose gas phase permeability is 0.01 of the formation can reduce the specific gas capacity of an SVE well by factors of 2 to 10 or more. Hydraulic fractures created in the vicinities of shallow wells commonly resemble sand-filled layers shaped like flat-lying disks or gently dipping saucers. The contrast between the gas-phase permeability of the sand in the fracture and that of the formation is particularly important, with significant effects requiring the ratio to be greater than approximately 50. Shallow hydraulic fractures filled with several tenths of m3 of sand in formations that are several orders of magnitude less permeable than that of the enveloping formation should increase specific gas capacity by factors of 10 or more. Field tests of the effects of hydraulic fractures on the performance of SVE were conducted by creating four wells intersecting fractures and a suite of control wells created using conventional methods in silty saprolite. Specific gas capacities ranged over more than an order of magnitude for 10 wells completed within a small area (2 m2) and at the same depth. Specific capacities correlate to the drilling method that was used to create the bore for the well: lowest values occurred in wells drilled with a machine auger, slightly better results were obtained using a Shelby tube, and the best results were obtained from conventional wells bored with a hand auger

  18. 40 CFR 147.52 - State-administered program-Hydraulic Fracturing of Coal Beds.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 24 2013-07-01 2013-07-01 false State-administered program-Hydraulic... PROGRAMS Alabama § 147.52 State-administered program—Hydraulic Fracturing of Coal Beds. The UIC program for hydraulic fracturing of coal beds in the State of Alabama, except those on Indian lands, is the...

  19. Combining periodic hydraulic tests and surface tilt measurements to explore in situ fracture hydromechanics

    NASA Astrophysics Data System (ADS)

    Schuite, Jonathan; Longuevergne, Laurent; Bour, Olivier; Guihéneuf, Nicolas; Becker, Matthew W.; Cole, Matthew; Burbey, Thomas J.; Lavenant, Nicolas; Boudin, Frédéric

    2017-08-01

    Fractured bedrock reservoirs are of socio-economical importance, as they may be used for storage or retrieval of fluids and energy. In particular, the hydromechanical behavior of fractures needs to be understood as it has implications on flow and governs stability issues (e.g., microseismicity). Laboratory, numerical, or field experiments have brought considerable insights to this topic. Nevertheless, in situ hydromechanical experiments are relatively uncommon, mainly because of technical and instrumental limitations. Here we present the early stage development and validation of a novel approach aiming at capturing the integrated hydromechanical behavior of natural fractures. It combines the use of surface tiltmeters to monitor the deformation associated with the periodic pressurization of fractures at depth in crystalline rocks. Periodic injection and withdrawal advantageously avoids mobilizing or extracting significant amounts of fluid, and it hinders any risk of reservoir failure. The oscillatory perturbation is intended to (1) facilitate the recognition of its signature in tilt measurements and (2) vary the hydraulic penetration depth in order to sample different volumes of the fractured bedrock around the inlet and thereby assess scale effects typical of fractured systems. By stacking tilt signals, we managed to recover small tilt amplitudes associated with pressure-derived fracture deformation. Therewith, we distinguish differences in mechanical properties between the three tested fractures, but we show that tilt amplitudes are weakly dependent on pressure penetration depth. Using an elastic model, we obtain fracture stiffness estimates that are consistent with published data. Our results should encourage further improvement of the method.

  20. Evaluation of rock/fracture interactions during steam injection through vertical hydraulic fractures

    SciTech Connect

    Kovscek, A.R.; Johnston, R.M.; Patzek, T.W.

    1997-05-01

    The design, results, and analysis of a steamdrive pilot in the South Belridge diatomite, Kern County, California, are reviewed. Pilot results demonstrate that steam can be injected across a 1,000-ft-tall diatomite column using hydraulically fractured wells and that significant oil is produced in response to steaming. A computationally simple numerical model is proposed and used to analyze reservoir heating and volumetric sweep by steam. Results from the analysis show that hydraulic fractures undergoing steam injection can be dynamic and asymmetrical.

  1. 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

  2. Hydraulic fracturing in cells and tissues: fracking meets cell biology.

    PubMed

    Arroyo, Marino; Trepat, Xavier

    2017-02-01

    The animal body is largely made of water. A small fraction of body water is freely flowing in blood and lymph, but most of it is trapped in hydrogels such as the extracellular matrix (ECM), the cytoskeleton, and chromatin. Besides providing a medium for biological molecules to diffuse, water trapped in hydrogels plays a fundamental mechanical role. This role is well captured by the theory of poroelasticity, which explains how any deformation applied to a hydrogel causes pressure gradients and water flows, much like compressing a sponge squeezes water out of it. Here we review recent evidence that poroelastic pressures and flows can fracture essential biological barriers such as the nuclear envelope, the cellular cortex, and epithelial layers. This type of fracture is known in engineering literature as hydraulic fracturing or 'fracking'. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. En-Echelon Fracture Growth in Shales During Hydraulic Stimulation

    NASA Astrophysics Data System (ADS)

    Smith-Boughner, L.; Baig, A. M.; Urbancic, T.; Viegas, G. F.

    2015-12-01

    The goal of a hydraulic fracture treatment program is to activate a discrete fracture network (DFN) that connects as much of the reservoir as possible and produces pathways for the extraction of hydrocarbons at the production well. The activated DFN usually grows outwards from the treatment well along the direction of the local maximum horizontal stress, SHmax. However, individual fractures in the DFN will have varying orientations that need not align with the overall azimuth or growth. The orientations of the individual fractures are determined by which pre-existing fractures generated from geological processes. The idealized cases of pure shear failures from long term deformation are likely oriented about 30 degrees from the direction of the maximum principal stress at the time of their activation and are not necessarily aligned with the current SHmax. Generally, pre-existing fracture sets do not align with SHmax ,and these multiple sets will be activated and grow in an en-echelon fashion to create a connected network that can move fluid away from the well. We use mechanisms from microseismic data, combined with a stress inversion, to constrain the fracture orientations associated with microseismic events. We examine a number of stages from the zipper-frac completion of half pad in the Horn River Basin, where generally two fracture sets are activated during the completion. However, we observe, potentially due to subtle rotations in the stresses throughout the completion, that different fractures are activated with space. This heterogeneity in orientation relative to SH­max is critical input for the geomechanical models on how treatment design programs influences the propagation of fluid and proppant into the reservoir.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  5. 40 CFR 147.52 - State-administered program-Hydraulic Fracturing of Coal Beds.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Fracturing of Coal Beds. 147.52 Section 147.52 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... PROGRAMS Alabama § 147.52 State-administered program—Hydraulic Fracturing of Coal Beds. The UIC program for hydraulic fracturing of coal beds in the State of Alabama, except those on Indian lands, is the program...

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

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Fracturing of Coal Beds. 147.52 Section 147.52 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... PROGRAMS Alabama § 147.52 State-administered program—Hydraulic Fracturing of Coal Beds. The UIC program for hydraulic fracturing of coal beds in the State of Alabama, except those on Indian lands, is the program...

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

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Fracturing of Coal Beds. 147.52 Section 147.52 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... PROGRAMS Alabama § 147.52 State-administered program—Hydraulic Fracturing of Coal Beds. The UIC program for hydraulic fracturing of coal beds in the State of Alabama, except those on Indian lands, is the...

  8. 40 CFR 147.52 - State-administered program-Hydraulic Fracturing of Coal Beds.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Fracturing of Coal Beds. 147.52 Section 147.52 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... PROGRAMS Alabama § 147.52 State-administered program—Hydraulic Fracturing of Coal Beds. The UIC program for hydraulic fracturing of coal beds in the State of Alabama, except those on Indian lands, is the...

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  10. 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

  11. 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 >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.

  12. Simulation of Hydraulic and Natural Fracture Interaction Using a Coupled DFN-DEM Model

    SciTech Connect

    J. Zhou; H. Huang; M. Deo

    2016-03-01

    The presence of natural fractures will usually result in a complex fracture network due to the interactions between hydraulic and natural fracture. The reactivation of natural fractures can generally provide additional flow paths from formation to wellbore which play a crucial role in improving the hydrocarbon recovery in these ultra-low permeability reservoir. Thus, accurate description of the geometry of discrete fractures and bedding is highly desired for accurate flow and production predictions. Compared to conventional continuum models that implicitly represent the discrete feature, Discrete Fracture Network (DFN) models could realistically model the connectivity of discontinuities at both reservoir scale and well scale. In this work, a new hybrid numerical model that couples Discrete Fracture Network (DFN) and Dual-Lattice Discrete Element Method (DL-DEM) is proposed to investigate the interaction between hydraulic fracture and natural fractures. Based on the proposed model, the effects of natural fracture orientation, density and injection properties on hydraulic-natural fractures interaction are investigated.

  13. Development and implementation of a fluid flow code to evaluate block hydraulic behaviors of the fractured rock masses

    NASA Astrophysics Data System (ADS)

    Um, Jeong-Gi; Han, Jisu; Lee, Dahye; Cho, Taechin

    2017-04-01

    A computer program code was developed to estimate the hydraulic head distribution through the 2-D DFN(discrete fracture network) blocks considering hydraulic aperture of the individual fractures, and to determine flow quantity, directional block hydraulic conductivity and principal hydraulic conductivity tensor according to fracture geometry such as orientation, frequency and size of the fracture network systems. The generated stochastic DFN system is assumed to have a network structure in which the equivalent flow pipe composed linear fractures is complexly connected. DFN systems often include individual or group of sub-network that are isolated from a network that can act as fluid flow passages from one flow boundary to another, and the fluid flow is completely blocked due to lack of connectivity. Fractures that are completely or partially isolated in the DFN system do not contribute to the overall fluid flow through the DFN system and add to the burden of numerical computation. This sometimes leads to numerical instability and failure to provide a solution. In this study, geometric and mathematical routines were designed and implemented to classify and eliminate such sub-networks. The developed program code can calculate the total head at each node connected to the flow path with various aperture as well as hydraulic conductivity of the individual flow pipe using the SOR method. Numerical experiments have been carried out to explore the applicability of the developed program code. A total of 108 stochastic 2-D DFN blocks of 20 m×20 m with various hydraulic aperture were prepared using two joint sets with fixed input parameters of fracture orientation, frequency and size distribution. The hydraulic anisotropy and the chance for equivalent continuum behavior of the DFN system were found to depend on the variability of fracture aperture.

  14. Mineral Reactions in Shale Gas Reservoirs: Barite Scale Formation from Reusing Produced Water As Hydraulic Fracturing Fluid.

    PubMed

    Paukert Vankeuren, Amelia N; Hakala, J Alexandra; Jarvis, Karl; Moore, Johnathan E

    2017-08-15

    Hydraulic fracturing for gas production is now ubiquitous in shale plays, but relatively little is known about shale-hydraulic fracturing fluid (HFF) reactions within the reservoir. To investigate reactions during the shut-in period of hydraulic fracturing, experiments were conducted flowing different HFFs through fractured Marcellus shale cores at reservoir temperature and pressure (66 °C, 20 MPa) for one week. Results indicate HFFs with hydrochloric acid cause substantial dissolution of carbonate minerals, as expected, increasing effective fracture volume (fracture volume + near-fracture matrix porosity) by 56-65%. HFFs with reused produced water composition cause precipitation of secondary minerals, particularly barite, decreasing effective fracture volume by 1-3%. Barite precipitation occurs despite the presence of antiscalants in experiments with and without shale contact and is driven in part by addition of dissolved sulfate from the decomposition of persulfate breakers in HFF at reservoir conditions. The overall effect of mineral changes on the reservoir has yet to be quantified, but the significant amount of barite scale formed by HFFs with reused produced water composition could reduce effective fracture volume. Further study is required to extrapolate experimental results to reservoir-scale and to explore the effect that mineral changes from HFF interaction with shale might have on gas production.

  15. Determination of In-Situ Stresses Around Underground Excavations by Means of Hydraulic Fracturing

    DTIC Science & Technology

    inhomogeneous, precracked variable rock is suitable for hydraulic fracturing as a method of in-situ stress measurement. It was found that basically the Coeur...d’Alene quartzite is amenable to hydraulic fracturing testing. The rock has no consistent anisotropy, but is inhomogeneous with physical property...horizontal stress notwithstanding rock condition. Field stress measurements in the Coeur d’Alene mines using the hydraulic fracturing technique are recommended.

  16. Numerical investigation of hydraulic fracture network propagation in naturally fractured shale formations

    NASA Astrophysics Data System (ADS)

    Zou, Yushi; Zhang, Shicheng; Ma, Xinfang; Zhou, Tong; Zeng, Bo

    2016-03-01

    Hydraulic fracture network (HFN) propagation in naturally fractured shale formations is investigated numerically using a 3D complex fracturing model based on the discrete element method. To account for the plastic deformation behavior of shales, the Drucker-Prager plasticity model is incorporated into the fracturing model. Parametric studies are then conducted for different Young's moduli, horizontal differential stresses, natural fracture (NF) properties, injection rates, and number and spacing of perforation clusters. Numerical results show that horizontal differential stress primarily determines the generation of a complex HFN. The plastic deformation of shale can reduce the stimulated reservoir volume; this is more obvious with Young's modulus of less than 20 GPa. In addition, a higher injection rate could largely increase the fracture complexity index (FCI). Moreover, increasing perforation cluster numbers per fracturing stage is beneficial for increasing the FCI, but it also increases the potential merging of neighboring fractures, which may lead to non-uniform development of HFN in far-wellbore regions. To achieve uniform development of HFN within a fracturing stage, the distribution of NFs should be fully considered. The results presented here may provide improved understanding of HFN generation and are favorable for optimizing fracturing treatment designs for shale formations.

  17. XFEM modeling of hydraulic fracture in porous rocks with natural fractures

    NASA Astrophysics Data System (ADS)

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

    2017-08-01

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

  18. Determining the spatial altitude of the hydraulic fractures.

    NASA Astrophysics Data System (ADS)

    Khamiev, Marsel; Kosarev, Victor; Goncharova, Galina

    2016-04-01

    Mathematical modeling and numerical simulation are the most widely used approaches for the solving geological problems. They imply software tools which are based on Monte Carlo method. The results of this project presents shows the possibility of using PNL tool to determine fracturing location. The modeled media is a homogeneous rock (limestone) cut by a vertical borehole (d=216 mm) with metal casing 9 mm thick. The cement sheath is 35 mm thick. The borehole is filled with fresh water. The rock mass is cut by crack, filled with a mixture of doped (gadolinium oxide Gd2O3) proppant (75%) and water (25%). A pulse neutron logging (PNL) tool is used for quality control in hydraulic fracturing operations. It includes a fast neutron source (so-called "neutron generator") and a set of thermal (or epithermal) neutron-sensing devices, forming the so-called near (ND) and far (FD) detectors. To evaluate neutron properties various segments (sectors) of the rock mass, the detector must register only neutrons that come from this very formation. It's possible if detecting block includes some (6 for example) thermal neutron detectors arranged circumferentially inside the tool. As a result we get few independent well logs, each accords with define rock sector. Afterwards synthetic logs processing we can determine spatial position of the hydraulic fracture.

  19. Investigation of growth features in several hydraulic fractures

    NASA Astrophysics Data System (ADS)

    Bykov, Alexander; Galybin, Alexander; Evdokimov, Alexander; Zavialova, Natalia; Zavialov, Ivan; Negodiaev, Sergey; Perepechkin, Ilia

    2017-04-01

    In this paper we simulate the growth of three or more interacting hydraulic fractures in the horizontal well with a cross flow of fluid between them. Calculation of the dynamics of cracks is performed in three dimensional space. The computation of the movement of fracturing fluid with proppant is performed in the two-dimensional space (the flow was averaged along crack aperture). For determining the hydraulic pipe resistance coefficient we used a generalization of the Reynolds number for fluids with power rheology and a generalization of the von Karman equation made by Dodge and Meiner. The calculations showed that the first crack was developing faster than the rest in homogeneous medium. During the steady loading the outer cracks pinch the inner cracks and it was shown that only the first and last fracture develop in extreme case. It is also possible to simulate the parameters at which the two developing outer cracks pinch the central one in the horizontal direction. In this case, the central crack may grow in the vertical direction.

  20. Investigating the time clustering of induced microseismicity generated by hydraulic fracturing

    NASA Astrophysics Data System (ADS)

    Telesca, Luciano; Eisner, Leo; Stabile, Tony A.; Vlček, Josef

    2016-12-01

    By using the global and local coefficient of variation and the Allan Factor we investigated the time-clustering properties of the time dynamics of fluid-injection–induced microseismicity. The experiment consists of a microseismic monitoring through a nearly vertical borehole of 12 receivers of a hydraulic fracturing stimulation along a horizontal well separated into more than 20 sections (stages) The main finding of the applied methodology is the discrimination between fault triggering and new fracturing, being the first characterized by a clusterization of the induced microseismic events and the second by a Poissonian behaviour of the generated events.

  1. Failure Mode of the Water-filled Fractures under Hydraulic Pressure in Karst Tunnels

    NASA Astrophysics Data System (ADS)

    Dong, Xin; Lu, Hao; Huang, Houxu; Hao, Yiqing; Xia, Yuanpu

    2017-06-01

    Water-filled fractures continue to grow after the excavation of karst tunnels, and the hydraulic pressure in these fractures changes along with such growth. This paper simplifies the fractures in the surrounding rock as flat ellipses and then identifies the critical hydraulic pressure values required for the occurrence of tensile-shear and compression-shear failures in water-filled fractures in the case of plane stress. The occurrence of tensile-shear fracture requires a larger critical hydraulic pressure than compression-shear failure in the same fracture. This paper examines the effects of fracture strike and lateral pressure coefficient on critical hydraulic pressure, and identifies compression-shear failure as the main failure mode of water-filled fractures. This paper also analyses the hydraulic pressure distribution in fractures with different extensions, and reveals that hydraulic pressure decreases along with the continuous growth of fractures and cannot completely fill a newly formed fracture with water. Fracture growth may be interrupted under the effect of hydraulic tensile shear.

  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. Theme 3: Mechanical Integrity - Pre & Post Well Integrity Methods for Hydraulically Fractured/Stimulated Wells

    EPA Pesticide Factsheets

    This presentation looks into wellbore design and monitoring techniques that are critical in assuring that wellbore integrity is maintained in conjunction with hydraulic fracturing/stimulation completion practices.

  4. Phase-field modeling of fracture propagation under hydraulic stimulation in pre-fractured rocks

    NASA Astrophysics Data System (ADS)

    Khisamitov, Ildar; Mohseni, Seyed Ali; Meschke, Guenther

    2016-04-01

    The presentation presents the numerical analysis of hydraulic fracturing within Griffith theory of brittle damage. The phase-field method [1] is employed to model brittle fracture propagation driven by pressurized fluids within fully saturated porous rocks. The phase-field equation is coupled with the Biot-theory using the effective stress concept. The porous rock is assumed as fully saturated with incompressible fluid and deforms within elasticity theory. The hydraulic fracturing propagates under mode I crack opening in quasi-static regime with slow fluid flow in porous matrix and fracture. The phase-field approach for the modelling of brittle fracture [2] coincides with the maximum energy release rate criterion in fracture mechanics theory. The phase-field equation is approximated over entire the domain and introduces new degree of freedom (damage variable). Crack surface is represented by a smooth regularized damage distribution over the fractured area. The presented numerical investigations are characterized by different scenarios of hydraulic stimulation and the interaction of a new fracture emanating from the bore hole with pre-existing cracks. The scenarios include predefined fractures with different oriented to specific angle and spatial distribution over the entire domain. The undamaged rock matrix is modeled as an isotropic elastic material with initial porosity and isotropic matrix permeability. The flow within the undamaged region is governed by Darcy's law while the fluid flow in fractures is approximated by cubic law with the crack opening computed from the displacement solution and the damage variable distribution [3]. Initial fractures are modeled by an initial distribution of the damage variable and by special zero-thickness interface finite elements. Adaptive algorithms in conjunction with appropriately chosen refinement criteria are utilized to reduce the computational costs. References [1] M.J. Borden "A phase-field description of dynamic

  5. Experimental study on the mechanism of hydraulic fracture growth in a glutenite reservoir

    NASA Astrophysics Data System (ADS)

    Ma, Xinfang; Zou, Yushi; Li, Ning; Chen, Ming; Zhang, Yinuo; Liu, Zizhong

    2017-04-01

    Glutenite reservoirs are frequently significantly heterogeneous because of their unique depositional environment. The presence of gravel in this type of formation complicates the growth path of hydraulic fracture (HF). In this study, laboratory fracturing experiments were conducted on six large natural glutenite specimens (300 mm × 300 mm × 300 mm) using a true triaxial hydraulic fracturing system to investigate the growth law of HF in glutenite reservoirs. Before the experiments were performed, the rock properties of the gravel particles and matrix in the glutenite specimens were determined using various apparatuses. The effects of gravel size, horizontal differential stress, fracturing fluid type (or viscosity), and flow rate on the HF growth pattern, fracture width, and injection pressure were examined in detail. Similar to previous studies, four types of HF intersections with gravel particles, namely, termination, penetration, deflection, and attraction, were observed. The HF growth path in the glutenite specimens with large gravel (40 mm-100 mm) is likely branched and tortuous even under high horizontal differential stress. The HF growth path in the glutenite specimens with small gravel (less than 20 mm) is simple, but a process zone with multiple thin fractures may be created. Breakdown pressure may increase significantly when HF initiates from high-strength gravel particles, which are mainly composed of quartz. HF propagation is likely limited within high-strength gravel particles, thereby resulting in narrow fractures and even termination. The use of low-viscosity fluids, such as slickwater, and the low injection rate can further limit HF growth, particularly its width. As a response, high extension pressure builds up during fracturing.

  6. 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.

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

    USGS Publications Warehouse

    Paillet, Frederick 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

  8. 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

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

    SciTech Connect

    Bonneville, Alain; Jung, Hun Bok; Shao, Hongbo; Kabilan, Senthil; Um, Wooyong; Carroll, Kenneth C.; Varga, Tamas; Suresh, Niraj; Stephens, Sean A.; Fernandez, Carlos A.

    2014-12-14

    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 (up to 210 °C) for both the rock samples and the injected fluid. After fracturing, 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.

  10. 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

    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.

  11. Cryogenic Fracturing: Laboratory Visualization Experiments and Numerical Simulations Using Peridynamics

    NASA Astrophysics Data System (ADS)

    Martin-Short, R.; Edmiston, J. K.

    2015-12-01

    Typical hydraulic fracturing operations involve the use of a large quantity of water, which can be problematic for several reasons including possible formation (permeability) damage, disposal of waste water, and the use of precious local water resource. An alternate reservoir permeability enhancing technology not requiring water is cryogenic fracturing. This method induces controlled fracturing of rock formations by thermal shock and has potentially important applications in the geothermal and hydrocarbon industries. In this process, cryogenic fluid—such as liquid nitrogen—is injected into the subsurface, causing fracturing due to thermal gradients. These fractures may improve the formation permeability relative to that achievable by hydraulic fracturing alone. We conducted combined laboratory visualization and numerical simulations studies of thermal-shock-induced fracture initiation and propagation resulting from liquid nitrogen injection in rock and analog materials. The experiment used transparent soda-lime glass cubes to facilitate real-time visualization of fracture growth and the fracture network geometry. In this contribution, we report the effect of overall temperature difference between cryogenic fluid and solid material on the produced fracture network, by pre-heating the glass cubes to several temperatures and injecting liquid nitrogen. Temperatures are monitored at several points by thermocouple and the fracture evolution is captured visually by camera. The experiment was modeled using a customized, thermoelastic, fracture-capable numerical simulation code based on peridynamics. The performance of the numerical code was validated by the results of the laboratory experiments, and then the code was used to study the different factors affecting a cryogenic fracturing operation, including the evolution of residual stresses and constitutive relationships for material failure. In complex rock such as shale, understanding the process of cryogenic

  12. The evolution of an applied hydraulic fracture project, Frontier Formation Moxa Arch, Wyoming

    SciTech Connect

    Harkrider, J.D.; Aud, W.W.; Cipolla, C.L.; Hansen, J.T.

    1994-12-31

    This paper demonstrates a methodical approach in the implementation of current hydraulic fracturing technologies. Specific examples illustrating the evolution of a consistent reservoir/hydraulic fracturing interpretation are presented in a case history of three GRI-Industry Technology Transfer wells. Detailed modeling of these project wells provided an overall reservoir and hydraulic fracture description that was consistent with respect to all observations. Based on identification of the fracturing mechanisms occurring, the second and third project wells show the capabilities of real-time diagnostics in the implementation of hydraulic fracture treatments. By optimizing the pad volume and fluid integrity to avoid premature screenouts, significant cost savings and improved proppant placement were achieved. The production and pressure build-up response in the first project well verifies the overall interpretation of the reservoir/hydraulic fracture model and provides the basis for eliminating the use of moderate strength/higher cost proppant over sand in low permeability/higher closure stress environments.

  13. 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

  14. Laboratory Visualization Experiments of Temperature-induced Fractures Around a Borehole (Cryogenic Fracturing) in Shale and Analogue Rock Samples

    NASA Astrophysics Data System (ADS)

    Kneafsey, T. J.; Nakagawa, S.; Wu, Y. S.; Mukhopadhyay, S.

    2014-12-01

    In tight shales, hydraulic fracturing is the dominant method for improving reservoir permeability. However, injecting water-based liquids can induce formation damage and disposal problems, thus other techniques are being sought. One alternative to hydraulic fracturing is producing fractures thermally, using low-temperature fluids (cryogens). The primary consequence of thermal stimulation is that shrinkage fractures are produced around the borehole wall. Recently, cryogenic stimulation produced some promising results when the cryogen (typically liquid nitrogen and cold nitrogen gas) could be brought to reservoir depth. Numerical modeling also showed possible significant increases in gas production from a shale reservoir after cryogenic stimulation. However, geometry and the dynamic behavior of these thermally induced fractures under different stress regimes and rock anisotropy and heterogeneity is not yet well understood.Currently, we are conducting a series of laboratory thermal fracturing experiments on Mancos Shale and transparent glass blocks, by injecting liquid nitrogen under atmospheric pressure into room temperature blocks under various anisotropic stress states. The glass blocks allow clear optical visualization of fracture development and final fracturing patterns. For the shale blocks, X-ray CT is used to image both pre-existing and induced fractures. Also, the effect of borehole orientation with respect to the bedding planes and aligned preexisting fractures is examined. Our initial experiment on a uniaxially compressed glass block showed fracturing behavior which was distinctly different from conventional hydraulic fracturing. In addition to tensile fractures in the maximum principal stress directions, the thermal contraction by the cryogen induced (1) chaotic, spalling fractures around the borehole wall, and (2) a series of disk-shaped annular fractures perpendicular to the borehole. When applied to a horizontal borehole, the propagation plane of the

  15. 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.

  16. Impacts on water quality by hydraulic fracturing in Pennsylvania

    NASA Astrophysics Data System (ADS)

    Yan, B.; Stute, M.; Chillrud, S. N.; Ross, J. M.; Howarth, M.; Panettieri, R.; Saberi, P.

    2015-12-01

    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 have been conducted in adjacent counties of western NY (Chemung, Tioga, Broome, and Delaware) and northern PA (Bradford, Susquehanna, and Wayne). 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. Measurements include a suite of 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. Higher levels of major ions were observed in PA samples close to the gas wells in the valley, possibly from hydraulic fracturing activities. The lab analysis of samples collected in recently launched 100 Bottom Project is ongoing and the results will be presented in this conference.

  17. Nontrivial clustering of microseismicity induced by hydraulic fracturing

    NASA Astrophysics Data System (ADS)

    Maghsoudi, Samira; Eaton, David W.; Davidsen, Jörn

    2016-10-01

    For induced microseismicity associated with hydraulic fracturing, the frequency-magnitude distribution is typically characterized by a falloff with increasing magnitude that is significantly faster than for seismicity along active fault systems. This characteristic may arise from a break in scale invariance, possibly due to mechanical layering that typifies fine-grained sedimentary rocks in many shale gas and tight oil reservoirs. The latter would imply the presence of spatiotemporal magnitude correlations. Using three microseismic catalogs for well stimulations in widely separated locations with varying hydraulic-fracturing methods, we show that events with similar magnitudes indeed tend to cluster in space and time. In addition, we show that the interevent time distribution can be described by a universal functional form characterized by two power laws. One exponent can be related to the presence of interevent triggering as in aftershock sequences and is a consequence of the Omori-Utsu law. The other one is a reflection of the intrinsic spatial variation in the microseismic response rates. Taken together, these features are indicative of nontrivial spatiotemporal clustering of induced microseismicity and, hence, of direct relevance for time-dependent seismic hazard assessment.

  18. The Role of the Rock on Hydraulic Fracturing of Tight Shales

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    Successful economic production of oil and gas from nano-darcy-range permeability, tight shale reservoirs, is achieved via massive hydraulic fracturing. This is so despite their limited hydrocarbon in place, on per unit rock volume basis. As a reference, consider a typical average porosity of 6% and an average hydrocarbon saturation of 50% to 75%. The importance of tight shales results from their large areal extent and vertical thickness. For example, the areal extent of the Anwar field in Saudi Arabia of 3230 square miles (and 300 ft thick), while the Marcellus shale alone is over 100,000 square miles (and 70 to 150 ft thick). The low permeability of the rock matrix, the predominantly mineralized rock fabric, and the high capillary forces to both brines and hydrocarbons, restrict the mobility of pore fluids in these reservoirs. Thus, one anticipates that fluids do not move very far within tight shales. Successful production, therefore results from maximizing the surface area of contact with the reservoir by massive hydraulic fracturing from horizontal bore holes. This was the conceptual breakthrough of the previous decade and the one that triggered the emergence of gas shales, and recently oily shales, as important economic sources of energy. It is now understood that the process can be made substantially more efficient, more sustainable, and more cost effective by understanding the rock. This will be the breakthrough of this decade. Microseismic monitoring, mass balance calculations, and laboratory experiments of hydraulic fracturing on tight shales indicate the development of fracture complexity and fracture propagation that can not be explained in detail in this layered heterogeneous media. It is now clear that in tight shales the large-scale formation fabric is responsible for fracture complexity. For example, the presence and pervasiveness of mineralized fractures, bed interfaces, lithologic contacts, and other types of discontinuities, and their orientation

  19. Spontaneous rupture on natural fractures and seismic radiation during hydraulic fracturing treatments

    NASA Astrophysics Data System (ADS)

    Duan, Benchun

    2016-07-01

    We extend spontaneous rupture models in earthquake source studies to analyze fluid injection problems. We perform these analyses on a 2-D fracture network model with a propagating hydraulic fracture (HF) and three sets of natural fractures (NFs). We find that it is difficult for NFs that are either parallel or perpendicular to the HF to slip because of little resolved shear stress on them in the prestress field. Shear failure of optimally oriented NFs depends on frictional parameters, such as the critical slip distance in slip-weakening laws. Slip of NFs near the tips of the HF may affect HF opening. Nonsmooth fracture opening generates isolated spiky seismic signals, while unstable frictional slip radiates strong and continuous seismic signals with long-duration coda waves. These results suggest microseismicity may be primarily generated by unstable frictional slip on NFs with some contribution from nonsmooth opening motions on HFs and/or NFs.

  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. Coupled Mineral Dissolution and Precipitation Reactions in Shale-Hydraulic Fracturing Fluid Systems

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Hydraulic fracturing of low-permeability, hydrocarbon-rich shales has recently become an important energy source in the United States. However, hydrocarbon recovery rates are low and drop rapidly after a few months. Hydraulic fracture fluids, which contain dissolved oxygen and numerous organic additives, induce dissolution and precipitation reactions that change the porosity and permeability of the shale. To investigate these reactions, we studied the interactions of four shales (Eagle Ford, Barnett, Marcellus, and Green River) with a simulated hydraulic fracture fluid in batch reactors at 80 °C. The shales were chosen for both economic viability and chemical variety, allowing us to explore the reactivities of different components. The Eagle Ford shale is carbonate rich, and the Green River shale contains significant siderite and kerogen. The Barnett shale also has a high organic content, while the Marcellus shale has the highest fractions of clay and pyrite. Our experiments show that hydrochloric acid in the fluid promotes carbonate mineral dissolution, rapidly raising the pH from acidic to circumneutral levels for the Eagle Ford and Green River shales. Dissolution textures in the Green River shale and large cavities in the Barnett shale indicate significant mineralogical and physical changes in the reacted rock. Morphological changes are not readily apparent in the Eagle Ford and Marcellus shales. For all shales, ongoing changes to the solution Al: Si ratio suggest incongruent aluminosilicate dissolution. Siderite or pyrite dissolution occurs within days and is followed by the formation of secondary Fe precipitates in suspension and coating the walls of the reactor. However, little evidence of any coatings on shale surfaces was found. The net effect of these reactions on porosity and permeability and their influence on the long-term efficacy of oil and gas recovery after hydraulic fracturing are critical to the energy landscape of the United States.

  2. 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.

  3. 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...

  4. 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

    ... this proposed action in an accompanying Regulatory Impact Analysis available in the rulemaking docket... significantly increased public awareness of hydraulic fracturing and the potential impacts that it may have on... things, that operators engaging in hydraulic fracturing prepare cement bond logs and undertake pressure...

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

    PubMed Central

    Varela, Brian A.; Haines, Seth S.; Engle, Mark A.

    2015-01-01

    Abstract 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. PMID:26937056

  6. 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...

  7. 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...

  8. Influence of Hydraulic Fracturing on Overlying Aquifers in the Presence of Leaky Abandoned Wells.

    PubMed

    Brownlow, Joshua W; James, Scott C; Yelderman, Joe C

    2016-11-01

    The association between hydrocarbon-rich reservoirs and organic-rich source rocks means unconventional oil and gas plays usually occur in mature sedimentary basins-where large-scale conventional development has already taken place. Abandoned wells in proximity to hydraulic fracturing could be affected by increased fluid pressures and corresponding newly generated fractures that directly connect (frac hit) to an abandoned well or to existing fractures intersecting an abandoned well. If contaminants migrate to a pathway hydraulically connected to an abandoned well, upward leakage may occur. Potential effects of hydraulic fracturing on upward flow through a particular type of leaky abandoned well-abandoned oil and gas wells converted into water wells were investigated using numerical modeling. Several factors that affect flow to leaky wells were considered including proximity of a leaky well to hydraulic fracturing, flowback, production, and leaky well abandonment methods. The numerical model used historical records and available industry data for the Eagle Ford Shale play in south Texas. Numerical simulations indicate that upward contaminant migration could occur through leaky converted wells if certain spatial and hydraulic conditions exist. Upward flow through leaky converted wells increased with proximity to hydraulic fracturing, but decreased when flowback and production occurred. Volumetric flow rates ranged between 0 and 0.086 m(3) /d for hydraulic-fracturing scenarios. Potential groundwater impacts should be paired with plausible transport mechanisms, and upward flow through leaky abandoned wells could be unrelated to hydraulic fracturing. The results also underscore the need to evaluate historical activities.

  9. 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...

  10. 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...

  11. Technology and means of a coal seam interval hydraulic fracturing for the seam degassing intensification

    NASA Astrophysics Data System (ADS)

    Klishin, VI; Opruk, GY; Tatsienko, AL

    2017-02-01

    Interval hydraulic fracturing use for the seam degassing intensification actuality is explained. The known methods of degassing are reviewed. Technological scheme of the interval coal seam hydraulic fracturing implementation is worked out. The equipment to fulfill degassing intensification measures is suggested.

  12. 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...

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

    USGS Publications Warehouse

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

    2015-01-01

    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.

  14. Spalling and the development of a hydraulic-fracturing strategy for coal. Annual report, October 1989-September 1990

    SciTech Connect

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

    1990-10-01

    Laboratory hydraulic fracturing experiments were performed on coal blocks from a mine near Marion Center, PA, in order to identify the responsible mechanisms for the high treatment pressures in coal. Tests were performed on saturated as well as unsaturated blocks containing lined and unlined wellbores. Wellbore lining would prevent pore pressure buildup around the wellbore; it would also prevent blockage of fracture entrance by coal particles. For some of the blocks, the 'in-fracture' pressures were directly measured by placing horizontal boreholes, instrumented with pressure measuring probes, across the fracture path. Test results have indicated that the high treatment pressures observed are principally near wellbore effects. These include poroelastic effects around the wellbore and plugging of the fracture entrance at or near the wellbore. Furthermore, these tests have shown that the hypothesized mechanisms associated with fracture tip (e.g., tip plugging and collapse) and multiple parallel fracturing are not the primary causes of the high treatment pressures on a laboratory scale.

  15. Hydraulic Fracturing for Oil and Gas: Impacts from the Hydraulic Fracturing Water Cycle on Drinking Water Resources in the United States (Final Report)

    EPA Science Inventory

    This final report provides a review and synthesis of available scientific information concerning the relationship between hydraulic fracturing activities and drinking water resources in the United States.

    The report is organized around activities in the hydraulic...

  16. Hydraulic Fracturing for Oil and Gas: Impacts from the Hydraulic Fracturing Water Cycle on Drinking Water Resources in the United States (Final Report)

    EPA Science Inventory

    This final report provides a review and synthesis of available scientific information concerning the relationship between hydraulic fracturing activities and drinking water resources in the United States.

    The report is organized around activities in the hydraulic...

  17. The impact of in-situ stress and outcrop-based fracture geometry on hydraulic aperture and upscaled permeability in fractured reservoirs

    NASA Astrophysics Data System (ADS)

    Bisdom, Kevin; Bertotti, Giovanni; Nick, Hamidreza M.

    2016-10-01

    Aperture has a controlling impact on porosity and permeability and is a source of uncertainty in modeling of naturally fractured reservoirs. This uncertainty results from difficulties in accurately quantifying aperture in the subsurface and from a limited fundamental understanding of the mechanical and diagenetic processes that control aperture. In the absence of cement bridges and high pore pressure, fractures in the subsurface are generally considered to be closed. However, experimental work, outcrop analyses and subsurface data show that some fractures remain open, and that aperture varies even along a single fracture. However, most fracture flow models consider constant apertures for fractures. We create a stress-dependent heterogeneous aperture by combining Finite Element modeling of discrete fracture networks with an empirical aperture model. Using a modeling approach that considers fractures explicitly, we quantify equivalent permeability, i.e. combined matrix and stress-dependent fracture flow. Fracture networks extracted from a large outcropping pavement form the basis of these models. The results show that the angle between fracture strike and σ1 has a controlling impact on aperture and permeability, where hydraulic opening is maximum for an angle of 15°. At this angle, the fracture experiences a minor amount of shear displacement that allows the fracture to remain open even when fluid pressure is lower than the local normal stress. Averaging the heterogeneous aperture to scale up permeability probably results in an underestimation of flow, indicating the need to incorporate full aperture distributions rather than simplified aperture models in reservoir-scale flow models.

  18. 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.

  19. Combined Finite-Discrete Element Method for Simulation of Hydraulic Fracturing

    NASA Astrophysics Data System (ADS)

    Yan, Chengzeng; Zheng, Hong; Sun, Guanhua; Ge, Xiurun

    2016-04-01

    Hydraulic fracturing is widely used in the exploitation of unconventional gas (such as shale gas).Thus, the study of hydraulic fracturing is of particular importance for petroleum industry. The combined finite-discrete element method (FDEM) proposed by Munjiza is an innovative numerical technique to capture progressive damage and failure processes in rock. However, it cannot model the fracturing process of rock driven by hydraulic pressure. In this study, we present a coupled hydro-mechanical model based on FDEM for the simulation of hydraulic fracturing in complex fracture geometries, where an algorithm for updating hydraulic fracture network is proposed. The algorithm can carry out connectivity searches for arbitrarily complex fracture networks. Then, we develop a new combined finite-discrete element method numerical code (Y-flow) for the simulation of hydraulic fracturing. Finally, several verification examples are given, and the simulation results agree well with the analytical or experimental results, indicating that the newly developed numerical code can capture hydraulic fracturing process correctly and effectively.

  20. 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.

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

    NASA Astrophysics Data System (ADS)

    Viswanathan, H. S.

    2016-12-01

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

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

    PubMed

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

    2005-02-01

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

  3. Asymptotic analysis of cross-hole hydraulic tests in fractured granite.

    PubMed

    Illman, Walter A; Tartakovsky, Daniel M

    2006-01-01

    Illman and Tartakovsky (2005a, 2005b) developed a new approach for the interpretation of three-dimensional pneumatic well tests conducted in porous or fractured geologic media, which is based on a straight-line analysis of late-time data. We modify this approach to interpret three-dimensional well tests in the saturated zone and use it to analyze the cross-hole hydraulic test data collected in the Full-Scale Engineered Barrier Experiment gallery at the Grimsel Test Site in Switzerland. The equivalent hydraulic conductivity and specific storage obtained from our analysis increase with the radial distance between the centroids of the pumping and monitoring intervals. Since this scale effect is observed from a single test type (cross-hole tests), it is less ambiguous than scale effects typically inferred from laboratory and multiple types of hydraulic tests (e.g., slug, single- and cross-hole tests). The statistical analysis of the estimated hydraulic parameters shows a strong correlation between equivalent hydraulic conductivity and specific storage.

  4. Measurement of Three Dimensional Strains Surrounding Hydraulic Fracture in Brittle Hydrogel

    NASA Astrophysics Data System (ADS)

    Steinhardt, W.; Rubinstein, S.

    2015-12-01

    Hydraulic fractures of oil and gas shales occur miles underground, below complex, layered rocks, making measurements of their dynamics, extent, or structure difficult to impossible. Rocks are heterogeneous at a wide range of length scales, and investigating how these non-uniformities affect the propagation and extent of fractures is vital to improving both the safety and efficiency of hydraulic fracturing operations. To study these effects we have developed a model system using brittle, heavily cross-linked hydrogels that we can fracture with fluids and observe with a fast camera (Livne et al. 2004). By embedding tracer particles within the gel and using laser sheet microscopy, we obtain three dimensional stress and strain maps of the zone surrounding a hydraulic fracture tip. Gels can also be set in layers or interfaces with tunable strengths or with designed heterogeneities, allowing us to understand the fundamental science of hydraulic fractures and investigate the dynamics of controllably complex materials.

  5. 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.

  6. 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.

  7. Hydraulic Fracture Propagation Through an Orthogonal Discontinuity: A Laboratory, Analytical and Numerical Study

    NASA Astrophysics Data System (ADS)

    Llanos, Ella María; Jeffrey, Robert G.; Hillis, Richard; Zhang, Xi

    2017-08-01

    Rocks are naturally fractured, and lack of knowledge of hydraulic fracture growth through the pre-existing discontinuities in rocks has impeded enhancing hydrocarbon extraction. This paper presents experimental results from uniaxial and biaxial tests, combined with numerical and analytical modelling results to develop a criterion for predicting whether a hydraulic fracture will cross a discontinuity, represented at the laboratory by unbonded machined frictional interfaces. The experimental results provide the first evidence for the impact of viscous fluid flow on the orthogonal fracture crossing. The fracture elliptical footprint also reflects the importance of both the applied loading stress and the viscosity in fracture propagation. The hydraulic fractures extend both in the direction of maximum compressive stress and in the direction with discontinuities that are arranged to be normal to the maximum compressive stress. The modelling results of fracture growth across discontinuities are obtained for the locations of slip starting points in initiating fracture crossing. Our analysis, in contrast to previous work on the prediction of frictional crossing, includes the non-singular stresses generated by the finite pressurised hydraulic fracture. Experimental and theoretical outcomes herein suggest that hydraulic fracture growth through an orthogonal discontinuity does not depend primarily on the interface friction coefficient.

  8. Mathematical Model of Hydraulic Fracturing of a Bed

    NASA Astrophysics Data System (ADS)

    Goncharova, G. S.; Khramchenkov, M. G.

    2016-07-01

    A study has been made of the problem on the process of formation of a zone of higher-than-average permeability with a moving boundary in an initially low-permeability porous medium (problem on hydraulic fracturing of a bed) in a three-dimensional formulation. A characteristic feature of the three-dimensional problem was the taking into account the existence of two zones (zone with a regular permeability and the destruction zone) in the porous medium, whose contact region was determined using the condition of mass balance on the moving boundary. Special features fundamental to the process of mass transfer in such filtration-inhomogeneous porous media have been revealed and analyzed.

  9. Treatment Process Requirements for Waters Containing Hydraulic Fracturing Chemicals

    NASA Astrophysics Data System (ADS)

    Stringfellow, W. T.; Camarillo, M. K.; Domen, J. K.; Sandelin, W.; Varadharajan, C.; Cooley, H.; Jordan, P. D.; Heberger, M. G.; Reagan, M. T.; Houseworth, J. E.; Birkholzer, J. T.

    2015-12-01

    A wide variety of chemical additives are used as part of the hydraulic fracturing (HyF) process. There is concern that HyF chemicals will be released into the environment and contaminate drinking water, agricultural water, or other water used for beneficial purposes. There is also interest in using produced water (water extracted from the subsurface during oil and gas production) for irrigation and other beneficial purposes, especially in the arid Southwest US. Reuse of produced water is not speculative: produced water can be low in salts and is being used in California for irrigation after minimal treatment. In this study, we identified chemicals that are used for hydraulic fracturing in California and conducted an analysis to determine if those chemicals would be removed by a variety of technically available treatment processes, including oil/water separation, air stripping, a variety of sorption media, advanced oxidation, biological treatment, and a variety of membrane treatment systems. The approach taken was to establish major physiochemical properties for individual chemicals (log Koc, Henry's constant, biodegradability, etc.), group chemicals by function (e.g corrosion inhibition, biocides), and use those properties to predict the fate of chemical additives in a treatment process. Results from this analysis is interpreted in the context of what is known about existing systems for the treatment of produced water before beneficial reuse, which includes a range of treatment systems from oil/water separators (the most common treatment) to sophisticated treatment trains used for purifying produced water for groundwater recharge. The results show that most HyF chemical additives will not be removed in existing treatment systems, but that more sophisticated treatment trains can be designed to remove additives before beneficial reuse.

  10. 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

  11. On the Importance of the Earthquake-Earthquake Triggering in Microseismicity Induced by Hydraulic Fracturing

    NASA Astrophysics Data System (ADS)

    Maghsoudi, S.; Eaton, D. W. S.; Davidsen, J.

    2015-12-01

    Permeability-enhancing treatments such as hydraulic fracturing induce microseismic events with reported magnitudes in the range of -3.0 to -0.5, although significantly larger induced earthquakes up to ML 4.4 have been reported. The primary controlling mechanism is thought to be diffusion of pore pressure away from the hydraulic fracture system, which leads to activation of fractures that are close to optimal orientation a critical state of stress. Understanding the specific primary and secondary triggering mechanisms during hydraulic fracturing is expected to furnish new insights regarding stress, strength of faults and rupture initiation and propagation. Here, we present evidence for the existence of earthquake-earthquake triggering cascades in microseismicity induced by hydraulic fracturing using novel methods from statistical seismology. While background seismicity dominates, we find that these triggering cascades exhibit features that also characterize tectonic aftershock sequences such as the empirical Omori-Utsu law and the productivity law. While this suggests that the underlying physical triggering mechanisms are similar in both cases, there are also pronounced differences. Specifically, we find that the magnitudes of earthquakes in microseismicity induced by hydraulic fracturing are not random but tend to cluster - independent of whether one considers background events or triggered events. We attribute this to the specific geometry associated with tight shale gas and oil reservoirs, which may lead to the occurrence of fracture arrest at bedding boundaries and gives rise to stratabound fracture networks. This has important implications for seismic hazard assessment and forecasting related to hydraulic fracturing.

  12. A fully coupled method for massively parallel simulation of hydraulically driven fractures in 3-dimensions: FULLY COUPLED PARALLEL SIMULATION OF HYDRAULIC FRACTURES IN 3-D

    DOE PAGES

    Settgast, Randolph R.; Fu, Pengcheng; Walsh, Stuart D. C.; ...

    2016-09-18

    This study describes a fully coupled finite element/finite volume approach for simulating field-scale hydraulically driven fractures in three dimensions, using massively parallel computing platforms. The proposed method is capable of capturing realistic representations of local heterogeneities, layering and natural fracture networks in a reservoir. A detailed description of the numerical implementation is provided, along with numerical studies comparing the model with both analytical solutions and experimental results. The results demonstrate the effectiveness of the proposed method for modeling large-scale problems involving hydraulically driven fractures in three dimensions.

  13. Organic compounds in hydraulic fracturing fluids and wastewaters: A review.

    PubMed

    Luek, Jenna L; Gonsior, Michael

    2017-10-15

    High volume hydraulic fracturing (HVHF) of shale to stimulate the release of natural gas produces a large quantity of wastewater in the form of flowback fluids and produced water. These wastewaters are highly variable in their composition and contain a mixture of fracturing fluid additives, geogenic inorganic and organic substances, and transformation products. The qualitative and quantitative analyses of organic compounds identified in HVHF fluids, flowback fluids, and produced waters are reviewed here to communicate knowledge gaps that exist in the composition of HVHF wastewaters. In general, analyses of organic compounds have focused on those amenable to gas chromatography, focusing on volatile and semi-volatile oil and gas compounds. Studies of more polar and non-volatile organic compounds have been limited by a lack of knowledge of what compounds may be present as well as quantitative methods and standards available for analyzing these complex mixtures. Liquid chromatography paired with high-resolution mass spectrometry has been used to investigate a number of additives and will be a key tool to further research on transformation products that are increasingly solubilized through physical, chemical, and biological processes in situ and during environmental contamination events. Diverse treatments have been tested and applied to HVHF wastewaters but limited information has been published on the quantitative removal of individual organic compounds. This review focuses on recently published information on organic compounds identified in flowback fluids and produced waters from HVHF. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

    PubMed

    Linkov, Igor; Trump, Benjamin; Jin, David; Mazurczak, Marcin; Schreurs, Miranda

    2014-01-01

    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 hazards associated with such technologies are not without controversy and are compounded by frequently changing information and an uncertain landscape of international politics and laws. Where each nation has its own energy policies and laws, predicting how a state with natural gas reserves that require hydraulic fracturing will regulate the industry is of paramount importance for potential developers and extractors. We present a method for predicting hydraulic fracturing decisions using multiple-criteria decision analysis. The case study evaluates the decisions of five hypothetical countries with differing political, social, environmental, and economic priorities, choosing among four policy alternatives: open hydraulic fracturing, limited hydraulic fracturing, completely banned hydraulic fracturing, and a cap and trade program. The result is a model that identifies the preferred policy alternative for each archetypal country and demonstrates the sensitivity the decision to particular metrics. Armed with such information, observers can predict each country's likely decisions related to natural gas exploration as more data become available or political situations change. Decision analysis provides a method to manage uncertainty and address forecasting concerns where rich and objective data may be lacking. For the case of hydraulic fracturing, the various political pressures and extreme uncertainty regarding the technology's risks and benefits serve as a prime platform to demonstrate how decision analysis can be used to predict future behaviors.

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

    SciTech Connect

    Murdoch, L. |; Siegrist, B.; Vesper, S.

    1997-12-31

    Many contaminated areas consist of a source area and a plume. In the source area, the contaminant moves vertically downward from a release point through the vadose zone to an underlying saturated region. Where contaminants are organic liquids, NAPL may accumulate on the water table, or it may continue to migrate downward through the saturated region. Early developments of permeable barrier technology have focused on intercepting horizontally moving plumes with vertical structures, such as trenches, filled with reactive material capable of immobilizing or degrading dissolved contaminants. This focus resulted in part from a need to economically treat the potentially large volumes of contaminated water in a plume, and in part from the availability of construction technology to create the vertical structures that could house reactive compounds. Contaminant source areas, however, have thus far remained largely excluded from the application of permeable barrier technology. One reason for this is the lack of conventional construction methods for creating suitable horizontal structures that would place reactive materials in the path of downward-moving contaminants. Methods of hydraulic fracturing have been widely used to create flat-lying to gently dipping layers of granular material in unconsolidated sediments. Most applications thus far have involved filling fractures with coarse-grained sand to create permeable layers that will increase the discharge of wells recovering contaminated water or vapor. However, it is possible to fill fractures with other compounds that alter the chemical composition of the subsurface. One early application involved development and field testing micro-encapsulated sodium percarbonate, a solid compound that releases oxygen and can create aerobic conditions suitable for biodegradation in the subsurface for several months.

  16. A National Assessment of the Potential Impacts of Hydraulic Fracturing Activities on Drinking Water Resources

    NASA Astrophysics Data System (ADS)

    Ridley, C.; Burden, S.; Fleming, M. M.; Knightes, C. D.; Koplos, J.; LeDuc, S. D.; Ring, S.; Stanek, J.; Tuccillo, M. E.; Weaver, J.; Frithsen, J.

    2015-12-01

    The U.S. Environmental Protection Agency recently released a draft assessment of the potential impacts of hydraulic fracturing on drinking water resources. As part of the draft assessment, we reviewed, analyzed, and synthesized information from over 950 sources and concluded that there are above and below ground mechanisms by which hydraulic fracturing activities have the potential to impact drinking water resources. These mechanisms include: Water withdrawals in times of, or in areas with, low water availability; Spills of hydraulic fracturing fluids and produced water; Fracturing directly into underground drinking water resources; Below ground migration of liquids and gases; and Inadequate treatment and discharge of wastewater. Of the potential mechanisms identified in this report, we found specific instances where one or more mechanisms led to impacts on drinking water resources, including contamination of drinking water wells. The number of identified cases, however, was small compared to the number of hydraulically fractured wells. This finding could reflect a rarity of effects on drinking water resources, but may also be due to other limiting factors. These factors include: insufficient pre- and post-fracturing data on the quality of drinking water resources; the paucity of long-term systematic studies; the presence of other sources of contamination precluding a definitive link between hydraulic fracturing activities and an impact; and the inaccessibility of some information on hydraulic fracturing activities and potential impacts. Disclaimer: The views expressed are those of the authors and do not necessarily reflect the views or polices of the EPA.

  17. 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.

  18. Water-Energy Metrics for Hydraulic Fracturing Versus Other Energy Technologies

    NASA Astrophysics Data System (ADS)

    Jackson, R. B.

    2015-12-01

    The combination of hydraulic fracturing and horizontal drilling has transformed energy production but drawn scrutiny for its water demands. Hydraulically fractured wells in the United States require millions of gallons of water per well and generate hundreds of billions of gallons of wastewater each year. Such wells also generate considerable energy. How does the water intensity (water per unit energy) for hydraulic fracturing compare with the intensity of other fossil fuels, nuclear power, and various renewables? I will use new data from plays such as the Marcellus and Bakken to address this question, comparing water metrics for extraction, processing, and, where relevant, electricity generation.

  19. Implementation of distributed feedback fiber laser sensor for acoustic measurements in hydraulic fracturing

    NASA Astrophysics Data System (ADS)

    Chen, Rongzhang; Yan, Aidong; Zaghloul, Mohamed A. S.; Lu, Guanyi; Bunger, Andrew P.; Miller, Gary A.; Cranch, Geoffrey A.; Chen, Kevin P.

    2016-09-01

    A distributed feedback (DFB) fiber laser strain sensor was implemented to measure acoustic emission induced by the hydraulic fracturing process. A study of practical sensor mounting configurations and their characteristics was carried out to find a practical solution. Combining the suitable mounting configuration and ultrahigh strain sensitivity of the DFB fiber laser, the evolution of the hydraulic fracturing process was well monitored. This study shows that fiber lasers can be useful alternatives to piezoelectric sensors in the field of hydraulic fracturing for gas and oil extraction.

  20. 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.

  1. Understanding Hydraulic Fracture Stimulations in Oil-Gas Developments Using Microseismicity (M<0)

    NASA Astrophysics Data System (ADS)

    Urbancic, T.; Baig, A. M.

    2011-12-01

    Microseismic monitoring is widely recognized as a powerful production optimization tool in the oil and gas industry. In particular, microseismic imaging has been shown to provide insight into the dynamic behavior of reservoirs during hydraulic fracture stimulations. In this presentation, we explore ideas and provide examples of preliminary work linking microseismicity, geology and engineering to build predictive reservoir models and to assist with their calibration and validation. Generally, microseismic imaging of hydraulic fractures focuses on mapping event locations. By simply examining the spatial and temporal variations in microseismicity, overall geometric measures such as orientation, fracture extent (height, length, and width) and fracture growth can be assessed. Examining fracture growth in the context of traditional hydraulic fracture models, estimates of fracture geometry based on microseismic data have been used to support the accepted fracture behavior. In hydraulic fracture stimulations, fractures are generally considered to develop along a single fracture azimuth or along a plane of fracturing controlled by regional stresses (i.e. along the direction of maximum principle stress), even within the context of a three-dimensional fracture network. In this study, we show how seismic moment tensors and source parameters have been used to assess the orientation of newly formed or reactivated fractures, as well as evaluate their size or time-dependent response to fluid injections. As well, using nearest-neighbor statistics, events can be grouped into behavioral domains, such as near-treatment-well and fracture extension regions, and used to outline a Discrete Fracture Network (DFN). Evaluating the spatial-temporal development of the DFN within the defined volumes can then be used to assess the fracture connectivity and enhanced permeability associated with the treatment. With moment tensor analysis, we show how petroleum engineers can also assess the

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

    PubMed

    Zhang, Zhaobin; Li, Xiao

    2016-08-23

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

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

    PubMed Central

    Zhang, Zhaobin; Li, Xiao

    2016-01-01

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

  4. Implementing ground surface deformation tools to characterize field-scale properties of a fractured aquifer during a short hydraulic test

    NASA Astrophysics Data System (ADS)

    Schuite, Jonathan; Longuevergne, Laurent; Bour, Olivier; Boudin, Frédérick; Durand, Stéphane

    2016-04-01

    In naturally fractured reservoirs, fluid flow is governed by the structural and hydromechanical properties of fracture networks or conductive fault zones. In order to ensure a sustained exploitation of resources or to assess the safety of underground storage, it is necessary to evaluate these properties. As they generally form highly heterogeneous and anisotropic reservoirs, fractured media may be well characterized by means of several complementary experimental methods or sounding techniques. In this framework, the observation of ground deformation has been proved useful to gain insight of a fractured reservoir's geometry and hydraulic properties. Commonly, large conductive structures like faults can be studied from surface deformation from satellite methods at monthly time scales, whereas meter scale fractures have to be examined under short-term in situ experiments using high accuracy intruments like tiltmeters or extensometers installed in boreholes or at the ground's surface. To the best of our knowledge, the feasability of a field scale (~ 100 m) characterization of a fractured reservoir with geodetic tools in a short term experiment has not yet been addressed. In the present study, we implement two complementary ground surface geodetic tools, namely tiltmetry and optical leveling, to monitor the deformation induced by a hydraulic recovery test at the Ploemeur hydrological observatory (France). Employing a simple purely elastic modeling approach, we show that the joint use of time constraining data (tilt) and spatially constraining data (vertical displacement) makes it possible to evaluate the geometry (dip, root depth and lateral extent) and the storativity of a hydraulically active fault zone, in good agreement with previous studies. Hence we demonstrate that the adequate use of two complementary ground surface deformation methods offer a rich insight of large conductive structure's properties using a single short term hydraulic load. Ground surface

  5. Seismological investigation of crack formation in hydraulic rock fracturing experiments and in natural geothermal environments. Progress report, September 1, 1979-August 31, 1980

    SciTech Connect

    Aki, K.

    1980-09-01

    Progress is reported in the following research areas: a synthesis of seismic experiments at the Fenton Hill Hot-Dry-Rock System; attenuation of high-frequency shear waves in the lithosphere; a new kinematic source model for deep volcanic tremors; ground motion in the near-field of a fluid-driven crack and its interpretation in the study of shallow volcanic tremor; low-velocity bodies under geothermal areas; and operation of event recorders in Mt. St. Helens and Newberry Peak with preliminary results from them. (MHR)

  6. Experimental Investigation into Hydraulic Fracture Network Propagation in Gas Shales Using CT Scanning Technology

    NASA Astrophysics Data System (ADS)

    Yushi, Zou; Shicheng, Zhang; Tong, Zhou; Xiang, Zhou; Tiankui, Guo

    2016-01-01

    Multistage fracturing of the horizontal well is recognized as the main stimulation technology for shale gas development. The hydraulic fracture geometry and stimulated reservoir volume (SRV) is interpreted by using the microseismic mapping technology. In this paper, we used a computerized tomography (CT) scanning technique to reveal the fracture geometry created in natural bedding-developed shale (cubic block of 30 cm × 30 cm × 30 cm) by laboratory fracturing. Experimental results show that partially opened bedding planes are helpful in increasing fracture complexity in shale. However, they tend to dominate fracture patterns for vertical stress difference Δ σ v ≤ 6 MPa, which decreases the vertical fracture number, resulting in the minimum SRV. A uniformly distributed complex fracture network requires the induced hydraulic fractures that can connect the pre-existing fractures as well as pulverize the continuum rock mass. In typical shale with a narrow (<0.05 mm) and closed natural fracture system, it is likely to create complex fracture for horizontal stress difference Δ σ h ≤ 6 MPa and simple transverse fracture for Δ σ h ≥ 9 MPa. However, high naturally fractured shale with a wide open natural fracture system (>0.1 mm) does not agree with the rule that low Δ σ h is favorable for uniformly creating a complex fracture network in zone. In such case, a moderate Δ σ h from 3 to 6 MPa is favorable for both the growth of new hydraulic fractures and the activation of a natural fracture system. Shale bedding, natural fracture, and geostress are objective formation conditions that we cannot change; we can only maximize the fracture complexity by controlling the engineering design for fluid viscosity, flow rate, and well completion type. Variable flow rate fracturing with low-viscosity slickwater fluid of 2.5 mPa s was proved to be an effective treatment to improve the connectivity of induced hydraulic fracture with pre-existing fractures. Moreover, the

  7. 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.

  8. 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

    -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

  9. Estimating spatially variable representative elementary scales in fractured architecture using hydraulic head observations

    NASA Astrophysics Data System (ADS)

    Wellman, Tristan P.; Poeter, Eileen P.

    2005-03-01

    Water resources within large-scale fractured aquifers are typically evaluated using continuum models. While any arbitrary scale of continuum can be imposed to represent fracture architecture, using the representative elementary volume eliminates errors that result from estimating network connectivity. In traditional theory, representative elementary scales (RES) are equal in magnitude and geometry throughout a domain and are normally determined using a structural indicator such as porosity or effective hydraulic conductivity. We present a fluid-based methodology, analyzing scale-dependent energy variation, to estimate RES using relatively low cost, readily available hydraulic head data. Hydraulic head predictions of RES (HYRES) reveal a spatial variation in elementary scale consistent with the flow field and fracture architecture. Porosity predictions of RES (PORRES) incorporate the structural effect of disconnected fracture regions but do not account for fluid behavior. RES estimated from hydraulic conductivity (KRES) are sensitive to fracture connectivity, which controls fluid movement, but are difficult to quantify because of scale and spatial variability. HYRES may be the superior approach for evaluating water resources because it is sensitive to fracture connectivity and avoids complications with scale and spatially dependent averaging. Our method is sensitive to fracture density, clustering, connectivity, and flow direction, but is insensitive to the magnitude of hydraulic gradient. HYRES is a novel approach to estimating spatially variable RES that improves water resource evaluation and flow characterization in fractured aquifers.

  10. Analysis of Hydraulic Fracturing Fluid Data from the FracFocus Chemical Disclosure Registry 1 (PDF)

    EPA Pesticide Factsheets

    The EPA analyzed data from the FracFocus Chemical Disclosure Registry 1.0 to better understand the chemicals and water used to hydraulically fracture oil and gas production wells across the United States.

  11. 75 FR 36387 - Informational Public Meetings for Hydraulic Fracturing Research Study; Correction

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-25

    ... Hydraulic Fracturing Research Study. The document contained an incorrect EPA Web site address in two places..., 2010, in FR doc. 2010-14897, on page 35023, in the third Column, correct the Web site addresses shown...

  12. 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...

  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. EPA Releases Draft Assessment on the Potential Impacts to Drinking Water Resources from Hydraulic Fracturing Activities

    EPA Pesticide Factsheets

    WASHINGTON-The Environmental Protection Agency (EPA) is releasing a draft assessment today on the potential impacts of hydraulic fracturing activities on drinking water resources in the United States. The assessment, done at the request of Congress, shows

  15. Analysis of Hydraulic Fracturing Fluid Data from the FracFocus Chemical Disclosure Registry 1

    EPA Pesticide Factsheets

    The EPA analyzed data from the FracFocus Chemical Disclosure Registry 1.0 to better understand the chemicals and water used to hydraulically fracture oil and gas production wells across the United States.

  16. Well Completions and Workovers for Wells with Hydraulic Fracturing- September 2012 Workshop

    EPA Pesticide Factsheets

    View presentations on well completions and workovers for wells with hydraulic fracturing, presented at the Stakeholder Workshop on Natural Gas in the Inventory of U.S. Greenhouse Gas (GHG) Emissions and Sinks on Thursday, September 13, 2012.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    In the framework of its research on the deep disposal of radioactive waste in shale formations, the French Institute for Radiological Protection and Nuclear Safety (IRSN) has developed a large array of in situ programs concerning the confining properties of shales in their underground research laboratory at Tournemire (SW France). One of its aims is to evaluate the occurrence and processes controlling radionuclide migration through the host rock, from the disposal system to the biosphere. Past research programs carried out at Tournemire covered mechanical, hydro-mechanical and physico-chemical properties of the Tournemire shale as well as water chemistry and long-term behaviour of the host rock. Studies show that fluid circulations in the undisturbed matrix are very slow (hydraulic conductivity of 10-14 to 10-15 m.s-1). However, recent work related to the occurrence of small scale fractures and clay-rich fault gouges indicate that fluid circulations may have been significantly modified in the vicinity of such features. To assess the transport properties associated with such faults, IRSN designed a series of in situ and laboratory experiments to evaluate the contribution of both diffusive and advective process on water and solute flux through a clay-rich fault zone (fault core and damaged zone) and in an undisturbed shale formation. As part of these studies, Modular Mini-Packer System (MMPS) hydraulic testing was conducted in multiple boreholes to characterize hydraulic conductivities within the formation. Pressure data collected during the hydraulic tests were analyzed using the nSIGHTS (n-dimensional Statistical Inverse Graphical Hydraulic Test Simulator) code to estimate hydraulic conductivity and formation pressures of the tested intervals. Preliminary results indicate hydraulic conductivities of 5.10-12 m.s-1 in the fault core and damaged zone and 10-14 m.s-1 in the adjacent undisturbed shale. Furthermore, when compared with neutron porosity data from borehole

  18. 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.

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

    SciTech Connect

    Mike L. Laue

    1997-05-08

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

  20. 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.

  1. Texas review of hydraulic fracturing water use and consumption

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  2. 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.

  3. 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.

  4. 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.

  5. Fluid-driven multiple fracture growth from a permeable bedding plane intersected by an ascending hydraulic fracture

    NASA Astrophysics Data System (ADS)

    Zhang, Xi; Jeffrey, Robert G.

    2012-12-01

    In bedded sedimentary rocks, the energy for spontaneous growth of multiple vertical fractures from a bedding plane may be provided by an overpressurized sublayer fracture that connects a fluid source to the bedding plane. In this paper, using our coupled deformation and flow model, we study the processes and mechanisms involved in the formation and interaction of closely space fractures from preexisting flaws or starter fractures located along the bedding plane. Fracture growth from multiple flaws can be convergent, parallel or divergent, depending on the factors like contrasts in moduli and far-field stresses, flaw sizes and locations, and initial bed conductivity, fluid viscosity, and injection rate, as well as time. The results presented here have been obtained for conditions where fluid viscous dissipation is dominant, in contrast to other results available in literature based on uniform pressure assumption equivalent to use of an inviscid fluid. It is demonstrated that the earlier a hydraulic fracture starts to extend, the more likely it is to become the primary fracture in a system of closely spaced fractures. The fracture closest to the fluid source typically grows faster as a result of a higher pressure level because viscous dissipation results in a decrease in pressure with distance from the fluid source. But its development does not completely inhibit the growth of other hydraulic fractures. Simultaneous growth of closely spaced fractures is supported by the local stress and energetic analyses, and the fracture distance can be very small. Their length to spacing ratio is accordingly much larger than that predicted previously. Under certain circumstances, a longer and more permeable fracture may grow to a greater extent than a shorter fracture closer to the fluid source, which may grow toward and merge with the longer fracture to create fracture clusters adjacent to a bedding plane.

  6. Design and modeling of small scale multiple fracturing experiments

    SciTech Connect

    Cuderman, J F

    1981-12-01

    Recent experiments at the Nevada Test Site (NTS) have demonstrated the existence of three distinct fracture regimes. Depending on the pressure rise time in a borehole, one can obtain hydraulic, multiple, or explosive fracturing behavior. The use of propellants rather than explosives in tamped boreholes permits tailoring of the pressure risetime over a wide range since propellants having a wide range of burn rates are available. This technique of using the combustion gases from a full bore propellant charge to produce controlled borehole pressurization is termed High Energy Gas Fracturing (HEGF). Several series of HEGF, in 0.15 m and 0.2 m diameter boreholes at 12 m depths, have been completed in a tunnel complex at NTS where mineback permitted direct observation of fracturing obtained. Because such large experiments are costly and time consuming, smaller scale experiments are desirable, provided results from small experiments can be used to predict fracture behavior in larger boreholes. In order to design small scale gas fracture experiments, the available data from previous HEGF experiments were carefully reviewed, analytical elastic wave modeling was initiated, and semi-empirical modeling was conducted which combined predictions for statically pressurized boreholes with experimental data. The results of these efforts include (1) the definition of what constitutes small scale experiments for emplacement in a tunnel complex at the Nevada Test Site, (2) prediction of average crack radius, in ash fall tuff, as a function of borehole size and energy input per unit length, (3) definition of multiple-hydraulic and multiple-explosive fracture boundaries as a function of boreholes size and surface wave velocity, (4) semi-empirical criteria for estimating stress and acceleration, and (5) a proposal that multiple fracture orientations may be governed by in situ stresses.

  7. 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

  8. 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.

  9. Hydraulic fracture monitoring in hard rock at 410 m depth with an advanced fluid-injection protocol and extensive sensor array

    NASA Astrophysics Data System (ADS)

    Zang, A.; Stephansson, O.; Stenberg, L.; Plenkers, K.; Specht, S.; Milkereit, C.; Schill, E.; Kwiatek, G.; Dresen, G.; Zimmermann, G.; Dahm, T.; Weber, M.

    2016-11-01

    In this article, an underground experiment at the Äspö Hard Rock Laboratory (HRL) is described. Main goal is optimizing geothermal heat exchange in crystalline rock mass at depth by multi-stage hydraulic fracturing with minimal impact on the environment, i.e. seismic events. For this, three arrays with acoustic emission, microseismicity and electromagnetic sensors are installed mapping hydraulic fracture initiation and growth. Fractures are driven by three different water injection schemes (continuous, progressive, pulse pressurization). After a brief review of hydraulic fracture operations in crystalline rock mass at mine scale, the site geology and the stress conditions at Äspö HRL are described. Then, the continuous, single-flow rate and alternative, multiple-flow rate fracture breakdown tests in a horizontal borehole at depth level 410 m are described together with the monitoring networks and sensitivity. Monitoring results include the primary catalogue of acoustic emission hypocenters obtained from four hydraulic fractures with the in situ trigger and localizing network. The continuous versus alternative water injection schemes are discussed in terms of the fracture breakdown pressure, the fracture pattern from impression packer result and the monitoring at the arrays. An example of multi-stage hydraulic fracturing with several phases of opening and closing of fracture walls is evaluated using data from acoustic emissions, seismic broadband recordings and electromagnetic signal response. Based on our limited amount of in situ tests (six) and evaluation of three tests in Ävrö granodiorite, in the multiple-flow rate test with progressively increasing target pressure, the acoustic emission activity starts at a later stage in the fracturing process compared to the conventional fracturing case with continuous water injection. In tendency, also the total number and magnitude of acoustic events is found to be smaller in the progressive treatment with frequent

  10. Hydraulic fracture monitoring in hard rock at 410 m depth with an advanced fluid-injection protocol and extensive sensor array

    NASA Astrophysics Data System (ADS)

    Zang, Arno; Stephansson, Ove; Stenberg, Leif; Plenkers, Katrin; Specht, Sebastian; Milkereit, Claus; Schill, Eva; Kwiatek, Grzegorz; Dresen, Georg; Zimmermann, Günter; Dahm, Torsten; Weber, Michael

    2017-02-01

    In this paper, an underground experiment at the Äspö Hard Rock Laboratory (HRL) is described. Main goal is optimizing geothermal heat exchange in crystalline rock mass at depth by multistage hydraulic fracturing with minimal impact on the environment, that is, seismic events. For this, three arrays with acoustic emission, microseismicity and electromagnetic sensors are installed mapping hydraulic fracture initiation and growth. Fractures are driven by three different water injection schemes (continuous, progressive and pulse pressurization). After a brief review of hydraulic fracture operations in crystalline rock mass at mine scale, the site geology and the stress conditions at Äspö HRL are described. Then, the continuous, single-flow rate and alternative, multiple-flow rate fracture breakdown tests in a horizontal borehole at depth level 410 m are described together with the monitoring networks and sensitivity. Monitoring results include the primary catalogue of acoustic emission hypocentres obtained from four hydraulic fractures with the in situ trigger and localizing network. The continuous versus alternative water injection schemes are discussed in terms of the fracture breakdown pressure, the fracture pattern from impression packer result and the monitoring at the arrays. An example of multistage hydraulic fracturing with several phases of opening and closing of fracture walls is evaluated using data from acoustic emissions, seismic broad-band recordings and electromagnetic signal response. Based on our limited amount of in situ tests (six) and evaluation of three tests in Ävrö granodiorite, in the multiple-flow rate test with progressively increasing target pressure, the acoustic emission activity starts at a later stage in the fracturing process compared to the conventional fracturing case with continuous water injection. In tendency, also the total number and magnitude of acoustic events are found to be smaller in the progressive treatment with

  11. 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

    2015-08-04

    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.

  12. Variations in Fracturing Mechanisms Observed by Broadband Microseismic Monitoring of Hydraulic Treatment

    NASA Astrophysics Data System (ADS)

    Tang, Y.; Niu, F.; Chen, H.; Zuo, Q.

    2015-12-01

    Hydraulic fracturing is the key stimulation technology to improve unconventional hydrocarbon recovery nowadays. Stimulation increases permeability of tight formations by causing fractures at depth. It involves pumping high-pressure fluid into reservoir rocks to force the opening of cracks, which could allow oil and gas to flow freely. The progress of a fracturing operation must be monitored carefully as fracturing could activate existing faults, leading the fluid mixed with chemicals to propagate beyond the targeted treatment zone. In order to study dynamic processes involved in hydraulic fracturing, we deployed a small-scale seismic array consisting of 22 broadband seismographs at the surface above a hydraulic fracturing area to monitor the whole fracturing progress. We made continuous recording for 20 days, and detected a total of 961 microseismic events with relatively high signal-to-noise ratio (SNR) recordings. We found that these events occurred either during the fracturing operation or after the fluid pumping. Some of the events also do not seem to be directly induced by the pumping, based on their locations and sizes. We determined the focal mechanisms of all events using the P-wave polarity data, and found that both the microseismicity and their focal mechanisms exhibit significant spatial and temporal variations. This variability can be associated with the hydraulic treatment, pre-existing faults, as well as the evolving stress field during the treatment. We computed the Coulomb stress changes of the observed seismicity to seek its contribution to the observed seismic variability.

  13. A County Level Assessment of Water Withdrawals for Hydraulic Fracturing: Where are Impacts Most Likely?

    NASA Astrophysics Data System (ADS)

    Fleming, M. M.; LeDuc, S. D.; Clark, C.; Todd, J.

    2015-12-01

    Concerns have arisen of the potential effects of hydraulic fracturing water withdrawals on both water for human consumption and aquatic communities. Any impacts are likely to be location specific since current U.S. hydraulic fracturing activities are concentrated in particular regions, water availability is unevenly distributed, and hydraulic fracturing water use differs between locations, including the amount of water use per well, source water, and reuse rates. Here, we used FracFocus to estimate annual hydraulic fracturing water use, and combined this with U.S. Geological Survey water use data and water availability indices to identify U.S. counties where potential impacts may be most likely. We surveyed the literature to understand source water and reuse rates. Overall, we found that hydraulic fracturing water use and consumption are a small percentage relative to total water use and consumption for most U.S. counties. However, there are 26 counties where fracturing water use is greater than 10% compared to 2010 total water use, and eight and four counties at greater than 30% and 50%, respectively. We conclude hydraulic fracturing water use currently has the greatest potential for impacts in southern and western Texas due to relatively high fracturing water use, low reuse rates, low fresh water availability, and frequent drought. However, the availability of brackish groundwater in these areas is also high relative to fracturing water use, suggesting an alternative source that could reduce potential impacts. Comparatively, the potential for impacts appears to be lower in other U.S. regions. While our county-scale findings do not preclude the possibility of more localized water quantity effects, this study provides a relative indicator of areas where potential problems might arise. Disclaimer: The views expressed here are those of the authors and do not necessarily represent the views or policies of the U.S. Environmental Protection Agency.

  14. 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.

  15. Multi-hazard risk assessment applied to hydraulic fracturing operations

    NASA Astrophysics Data System (ADS)

    Garcia-Aristizabal, Alexander; Gasparini, Paolo; Russo, Raffaella; Capuano, Paolo

    2017-04-01

    Without exception, the exploitation of any energy resource produces impacts and intrinsically bears risks. Therefore, to make sound decisions about future energy resource exploitation, it is important to clearly understand the potential environmental impacts in the full life-cycle of an energy development project, distinguishing between the specific impacts intrinsically related to exploiting a given energy resource and those shared with the exploitation of other energy resources. Technological advances as directional drilling and hydraulic fracturing have led to a rapid expansion of unconventional resources (UR) exploration and exploitation; as a consequence, both public health and environmental concerns have risen. The main objective of a multi-hazard risk assessment applied to the development of UR is to assess the rate (or the likelihood) of occurrence of incidents and the relative potential impacts on surrounding environment, considering different hazards and their interactions. Such analyses have to be performed considering the different stages of development of a project; however, the discussion in this paper is mainly focused on the analysis applied to the hydraulic fracturing stage of a UR development project. The multi-hazard risk assessment applied to the development of UR poses a number of challenges, making of this one a particularly complex problem. First, a number of external hazards might be considered as potential triggering mechanisms. Such hazards can be either of natural origin or anthropogenic events caused by the same industrial activities. Second, failures might propagate through the industrial elements, leading to complex scenarios according to the layout of the industrial site. Third, there is a number of potential risk receptors, ranging from environmental elements (as the air, soil, surface water, or groundwater) to local communities and ecosystems. The multi-hazard risk approach for this problem is set by considering multiple hazards

  16. 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.

  17. Modelling Subduction Zone Magmatism Due to Hydraulic Fracture

    NASA Astrophysics Data System (ADS)

    Lawton, R.; Davies, J. H.

    2014-12-01

    The aim of this project is to test the hypothesis that subduction zone magmatism involves hydraulic fractures propagating from the oceanic crust to the mantle wedge source region (Davies, 1999). We aim to test this hypothesis by developing a numerical model of the process, and then comparing model outputs with observations. The hypothesis proposes that the water interconnects in the slab following an earthquake. If sufficient pressure develops a hydrofracture occurs. The hydrofracture will expand in the direction of the least compressive stress and propagate in the direction of the most compressive stress, which is out into the wedge. Therefore we can calculate the hydrofracture path and end-point, given the start location on the slab and the propagation distance. We can therefore predict where water is added to the mantle wedge. To take this further we have developed a thermal model of a subduction zone. The model uses a finite difference, marker-in-cell method to solve the heat equation (Gerya, 2010). The velocity field was prescribed using the analytical expression of cornerflow (Batchelor, 1967). The markers contained within the fixed grid are used to track the different compositions and their properties. The subduction zone thermal model was benchmarked (Van Keken, 2008). We used the hydrous melting parameterization of Katz et.al., (2003) to calculate the degree of melting caused by the addition of water to the wedge. We investigate models where the hydrofractures, with properties constrained by estimated water fluxes, have random end points. The model predicts degree of melting, magma productivity, temperature of the melt and water content in the melt for different initial water fluxes. Future models will also include the buoyancy effect of the melt and residue. Batchelor, Cambridge UP, 1967. Davies, Nature, 398: 142-145, 1999. Gerya, Cambridge UP, 2010. Katz, Geochem. Geophys. Geosy, 4(9), 2003 Van Keken et.al. Phys. Earth. Planet. In., 171:187-197, 2008.

  18. Hydraulic fracturing for natural gas: impact on health and environment.

    PubMed

    Carpenter, David O

    2016-03-01

    Shale deposits exist in many parts of the world and contain relatively large amounts of natural gas and oil. Recent technological developments in the process of horizontal hydraulic fracturing (hydrofracturing or fracking) have suddenly made it economically feasible to extract natural gas from shale. While natural gas is a much cleaner burning fuel than coal, there are a number of significant threats to human health from the extraction process as currently practiced. There are immediate threats to health resulting from air pollution from volatile organic compounds, which contain carcinogens such as benzene and ethyl-benzene, and which have adverse neurologic and respiratory effects. Hydrogen sulfide, a component of natural gas, is a potent neuro- and respiratory toxin. In addition, levels of formaldehyde are elevated around fracking sites due to truck traffic and conversion of methane to formaldehyde by sunlight. There are major concerns about water contamination because the chemicals used can get into both ground and surface water. Much of the produced water (up to 40% of what is injected) comes back out of the gas well with significant radioactivity because radium in subsurface rock is relatively water soluble. There are significant long-term threats beyond cancer, including exacerbation of climate change due to the release of methane into the atmosphere, and increased earthquake activity due to disruption of subsurface tectonic plates. While fracking for natural gas has significant economic benefits, and while natural gas is theoretically a better fossil fuel as compared to coal and oil, current fracking practices pose significant adverse health effects to workers and near-by residents. The health of the public should not be compromized simply for the economic benefits to the industry.

  19. A fully coupled method for massively parallel simulation of hydraulically driven fractures in 3-dimensions

    DOE PAGES

    Settgast, Randolph R.; Fu, Pengcheng; Walsh, Stuart D. C.; ...

    2016-09-18

    This study describes a fully coupled finite element/finite volume approach for simulating field-scale hydraulically driven fractures in three dimensions, using massively parallel computing platforms. The proposed method is capable of capturing realistic representations of local heterogeneities, layering and natural fracture networks in a reservoir. A detailed description of the numerical implementation is provided, along with numerical studies comparing the model with both analytical solutions and experimental results. The results demonstrate the effectiveness of the proposed method for modeling large-scale problems involving hydraulically driven fractures in three dimensions.

  20. 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.

  1. Using borehole flow logging to optimize hydraulic-test procedures in heterogeneous fractured aquifers

    USGS Publications Warehouse

    Paillet, F.L.

    1995-01-01

    Hydraulic properties of heterogeneous fractured aquifers are difficult to characterize, and such characterization usually requires equipment-intensive and time-consuming applications of hydraulic testing in situ. Conventional coring and geophysical logging techniques provide useful and reliable information on the distribution of bedding planes, fractures and solution openings along boreholes, but it is often unclear how these locally permeable features are organized into larger-scale zones of hydraulic conductivity. New boreholes flow-logging equipment provides techniques designed to identify hydraulically active fractures intersecting boreholes, and to indicate how these fractures might be connected to larger-scale flow paths in the surrounding aquifer. Potential complications in interpreting flowmeter logs include: 1) Ambient hydraulic conditions that mask the detection of hydraulically active fractures; 2) Inability to maintain quasi-steady drawdowns during aquifer tests, which causes temporal variations in flow intensity to be confused with inflows during pumping; and 3) Effects of uncontrolled background variations in hydraulic head, which also complicate the interpretation of inflows during aquifer tests. Application of these techniques is illustrated by the analysis of cross-borehole flowmeter data from an array of four bedrock boreholes in granitic schist at the Mirror Lake, New Hampshire, research site. Only two days of field operations were required to unambiguously identify the few fractures or fracture zones that contribute most inflow to boreholes in the CO borehole array during pumping. Such information was critical in the interpretation of water-quality data. This information also permitted the setting of the available string of two packers in each borehole so as to return the aquifer as close to pre-drilling conditions as possible with the available equipment.

  2. 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.

  3. HYDRAULIC FRACTURING IN PORUS AND NONPORUS ROCK AND ITS POTENTIAL FOR DETERMINING IN-SITU STRESSES AT GREAT DEPTH.

    DTIC Science & Technology

    The process of Hydraulic Fracturing as a method of determining in-situ stresses in brittle elastic formations at great depth is analyzed both...theoretically and experimentally. Theoretically, it is found that in attempting to relate the recorded hydraulic fracturing pressures to tectonic stresses...at great depth. The experimental results show that hydraulic fracturing occurred when the internal pressure achieved a critical value that could

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

    SciTech Connect

    Mike L. Laue

    1997-10-30

    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.

  5. 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.; 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.

  6. Pore pressure migration during hydraulic stimulation due to permeability enhancement by low-pressure subcritical fracture slip

    NASA Astrophysics Data System (ADS)

    Mukuhira, Yusuke; Moriya, Hirokazu; Ito, Takatoshi; Asanuma, Hiroshi; Häring, Markus

    2017-04-01

    Understanding the details of pressure migration during hydraulic stimulation is important for the design of an energy extraction system and reservoir management, as well as for the mitigation of hazardous-induced seismicity. Based on microseismic and regional stress information, we estimated the pore pressure increase required to generate shear slip on an existing fracture during stimulation. Spatiotemporal analysis of pore pressure migration revealed that lower pore pressure migrates farther and faster and that higher pore pressure migrates more slowly. These phenomena can be explained by the relationship between fracture permeability and stress state criticality. Subcritical fractures experience shear slip following smaller increases of pore pressure and promote migration of pore pressure because of their enhanced permeability. The difference in migration rates between lower and higher pore pressures suggests that the optimum wellhead pressure is the one that can stimulate relatively permeable fractures, selectively. Its selection optimizes economic benefits and minimizes seismic risk.

  7. Seismic refraction and electrical resistivity tests for fracture induced hydraulic anisotropy in a mountain watershed.

    NASA Astrophysics Data System (ADS)

    Mendieta, A. L.; Bradford, J.; Liberty, L. M.; McNamara, J. P.

    2016-12-01

    Granitic based terrains often have complex hydrogeological systems. It is often assumed that the bedrock is impermeable, unless it is fractured. If the bedrock is fractured this can greatly affect fluid flow, depending on fracture density and orientation. Recently there has been a substantial increase in the number of geophysical studies designed to investigate hydrologic processes in mountain watersheds, however few of these studies have taken fracture induced geophysical and hydraulic anisotropy into consideration. Vertically oriented fractures with a preferred orientation produce azimuthal anisotropy in the electrical resistivity, the seismic primary wave (P-wave) velocity, and the hydraulic permeability. By measuring the electrical and seismic anisotropy we can estimate fracture orientation and density which improves our understanding of hydraulic properties. Despite numerous previous studies of the hydrologic system, the subsurface hydraulic system at the Dry Creek Experimental Watershed (DCEW), located near Boise, Idaho, is not completely understood. This is particularly true of the deep (>5m) system which is difficult to study using conventional hydrologic measurements, particularly in rugged and remote mountain environments. From previous studies, it is hypothesized that there is a system of fractures that may be aligned according to the local stress field. To test for the preferential alignment, ergo the direction of preferential water flow, we collected seismic and electrical resistivity profiles along different azimuths. The preliminary results show an azimuthal dependence of the P-wave velocities in the bedrock, at depths greater than 18 m; P-wave velocities range from 3500 to 4100 m/s, which represents a 17.5 % difference. We interpret this difference to be caused by fractures present in the bedrock. At the same location, we measured an electric resistivity value of 29 ohm-m, and we expect a difference of 37 %, if the fractures are fully saturated

  8. 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.

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

    PubMed

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

    2011-03-01

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

  10. 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

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

    USGS Publications Warehouse

    Lane, J.W.; 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

  12. Numerical Investigation into the Influence of Bedding Plane on Hydraulic Fracture Network Propagation in Shale Formations

    NASA Astrophysics Data System (ADS)

    Yushi, Zou; Xinfang, Ma; Shicheng, Zhang; Tong, Zhou; Han, Li

    2016-09-01

    Shale formations are often characterized by low matrix permeability and contain numerous bedding planes (BPs) and natural fractures (NFs). Massive hydraulic fracturing is an important technology for the economic development of shale formations in which a large-scale hydraulic fracture network (HFN) is generated for hydrocarbon flow. In this study, HFN propagation is numerically investigated in a horizontally layered and naturally fractured shale formation by using a newly developed complex fracturing model based on the 3D discrete element method. In this model, a succession of continuous horizontal BP interfaces and vertical NFs is explicitly represented and a shale matrix block is considered impermeable, transversely isotropic, and linearly elastic. A series of simulations is performed to illustrate the influence of anisotropy, associated with the presence of BPs, on the HFN propagation geometry in shale formations. Modeling results reveal that the presence of BP interfaces increases the injection pressure during fracturing. HF deflection into a BP interface tends to occur under high strength and elastic anisotropy as well as in low vertical stress anisotropy conditions, which generate a T-shaped or horizontal fracture. Opened BP interfaces may limit the growth of the fracture upward and downward, resulting in a very low stimulated thickness. However, the opened BP interfaces favor fracture complexity because of the improved connection between HFs and NFs horizontally under moderate vertical stress anisotropy. This study may help predict the HF growth geometry and optimize the fracturing treatment designs in shale formations with complex depositional heterogeneity.

  13. 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

  14. On the possibility of magnetic nano-markers use for hydraulic fracturing in shale gas mining

    NASA Astrophysics Data System (ADS)

    Zawadzki, Jaroslaw; Bogacki, Jan

    2016-04-01

    Recently shale gas production became essential for the global economy, thanks to fast advances in shale fracturing technology. Shale gas extraction can be achieved by drilling techniques coupled with hydraulic fracturing. Further increasing of shale gas production is possible by improving the efficiency of hydraulic fracturing and assessing the spatial distribution of fractures in shale deposits. The latter can be achieved by adding magnetic markers to fracturing fluid or directly to proppant, which keeps the fracture pathways open. After that, the range of hydraulic fracturing can be assessed by measurement of vertical and horizontal component of earth's magnetic field before and after fracturing. The difference in these components caused by the presence of magnetic marker particles may allow to delineate spatial distribution of fractures. Due to the fact, that subterranean geological formations may contain minerals with significant magnetic properties, it is important to provide to the markers excellent magnetic properties which should be also, independent of harsh chemical and geological conditions. On the other hand it is of great significance to produce magnetic markers at an affordable price because of the large quantities of fracturing fluids or proppants used during shale fracturing. Examining the properties of nano-materials, it was found, that they possess clearly superior magnetic properties, as compared to the same structure but having a larger particle size. It should be then possible, to use lower amount of magnetic marker, to obtain the same effect. Although a research on properties of new magnetic nano-materials is very intensive, cheap magnetic nano-materials are not yet produced on a scale appropriate for shale gas mining. In this work we overview, in detail, geological, technological and economic aspects of using magnetic nano-markers in shale gas mining. Acknowledgment This work was supported by the NCBiR under Grant "Electromagnetic method to

  15. Induced seismicity caused by hydraulic fracturing in deep geothermal wells in Germany and adjacent areas

    NASA Astrophysics Data System (ADS)

    Plenefisch, Thomas; Brückner, Lisa; Ceranna, Lars; Gestermann, Nicolai; Houben, Georg; Tischner, Torsten; Wegler, Ulrich; Wellbrink, Matthias; Bönnemann, Christian; Bertram, Andreas; Kirschbaum, Bernd

    2016-04-01

    Recently, the BGR has worked out a study on the potential environmental impact caused by hydraulic fracturing or chemical stimulations in deep geothermal reservoirs in Germany and adjacent areas. The investigations and analyses are based on existing studies and information provided by operators. The two environmental impacts being essentially considered in the report are induced seismicity and possible contamination of the groundwater reservoirs which serve for drinking water supply. Altogether, in this study, information on 30 hydraulic frac operations and 26 chemical stimulations including information from neighboring countries were compiled and analyzed. Out of the hydraulic stimulations two thirds were carried out as waterfracs and one third as fracturing with proppants. Parameters used in the study to characterize the induced seismicity are maximum magnitude, number of seismic events, size of the seismically active volume, and the relation of this volume to fault zones and the cap rock, as well as, finally, the impacts at the Earth's surface. The response of the subsurface to hydraulic fracturing is variable: There are some activities, which cause perceptible seismic events, others, where no perceptible but instrumentally detected events occurred, and moreover activities without even any instrumentally detected events. A classification of seismic hazard with respect to tectonic region, geology, or depth of the layer is still difficult, since the number of hydraulic fracturing measures in deep geothermal wells is small making a statistically sound analysis impossible. However, there are some indications, that hydraulic fracturing in granite in tectonically active regions like the Upper Rhine Graben results in comparatively stronger, perceptible seismicity compared to hydraulic fracturing in the sedimentary rocks of the North German basin. The maximum magnitudes of induced earthquakes caused by hydraulic fracturing of deep geothermal wells in Germany are

  16. 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.

  17. Hydraulic anisotropy characterization of fracture-dominated media using azimuthal self potential

    NASA Astrophysics Data System (ADS)

    Wishart, Debonne N.

    Increasing attention has been given to the exploration and development of fractured-rock aquifers as new sources groundwater supply to meet the demand of a growing population. Today, the development of groundwater resources includes the application of cost-effective, non-invasive geophysical investigations to solve groundwater problems in the subsurface as part of an initiative to protect water quality. Electric geophysical investigations were undertaken to characterize hydraulic and electric anisotropy at the laboratory and field scales by combining and comparing asymmetric configurations of azimuthal self potential gradient (ASPG) and azimuthal resistivity surveys (ARS) on (1) a fracture block model, (2) pneumatically-fractured compressed clay sediments, and (3) fractured crystalline bedrock at four field sites throughout the north New Jersey Highlands Province. In situ electrokinetic self potentials observed on a fracture block model, field-scale fractures, and mechanically-induced fractures are consistent with electrokinetic theory. Linearity exists between ASPG and fracture strike density in all three fracture systems. The magnitude of electrokinetic SP scales with flow rate for any particular fracture set and the positive lobe of the ASPG anomaly indicates the flow direction. ASPG anisotropy appears diagnostic of (1) hydraulic gradient driving flow within fracture sets, and (2) fracture density (presumably controlling the strength of the streaming potential coefficient). Geophysical characterization of bulk rock anisotropy in fractures at four field sites in the New Jersey Highlands (NJH) showed ASPG captured hydraulic-anisotropy at three of four sites, whereas ARS data were dominated by resistivity heterogeneity at all but one site. Significant advantages of ASPG relative to ARS surveys in hydrogeologic site characterization of fracture-dominated media include its (1) cost-effectiveness, (2) sensitivity to fracture-induced anisotropy, (3) capability to

  18. Waterflooding simulation of reservoir containing horizontal well stimulated by multistage hydraulic fracturing

    NASA Astrophysics Data System (ADS)

    Mazo, A. B.; Khamidullin, M. R.; Potashev, K. A.

    2016-11-01

    The article presents a three-dimensional mathematical model for two-phase fluid flow near a multistage hydraulically fractured horizontal well (MSHFHW). The flow in the reservoir and in the fractures is simulated separately, and the flow rate is governed by Darcy's law. Finite volume method is used for spatial approximation. The obtained systems of linear equations for pressure in the reservoir and in the fractures are solved simultaneously, which allows us to avoid using iterative process for solution adjustment both in the fractures and the reservoir. Saturation is calculated by the implicit adaptive scheme AIM.

  19. Simulation of the Filtration in a Low-Permeability Pool with Two Perpendicular Technogenic Hydraulic Fractures

    NASA Astrophysics Data System (ADS)

    Davletbaev, A. Ya.; Mukhametova, Z. S.

    2017-05-01

    Results of numerical simulation of the filtration of a fluid in a well with two perpendicular technogenic hydraulic fractures in a low-permeability pool are presented. It was assumed that the filtration in the producing pool and in the fractures adheres to the Darcy law and the permeabilities of the fractures exceed the permeability of the pool by approximately 105 times. Because of the small opening of the fractures, as compared to their length and the distance between them and the boundaries of the pool, the flow of the fluid in the fractures was assumed to be one-dimensional. The influence of the flow capacity and geometry of the primary fracture on the change in the pressure in the well with time was analyzed, and the nonstationary pressure fields in the well-fractures-pool system were calculated.

  20. 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

  1. 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.

  2. A preliminary statistical model for hydraulic fracture-induced seismicity in the Western Canada Sedimentary Basin

    NASA Astrophysics Data System (ADS)

    Ghofrani, Hadi; Atkinson, Gail M.

    2016-10-01

    We characterize the statistical relationship between hydraulic fracturing and seismicity in western Canada by using the concept of cellular seismicity. We determine the regionally averaged probability that hydraulic fracture operations will be associated with M ≥ 3 seismicity within a 10 km grid cell. This rate is 0.01 to 0.026 at the 95th percentile confidence limit. Monte Carlo simulations confirm that the observed correlations are extremely unlikely (≪1%) to have been obtained by chance. Proximity to a disposal well and proximity to the Swan Hills Formation, which has been suggested as a proxy for basement controlled faults, appear to increase the likelihood that hydraulic fracturing will trigger seismicity.

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

    USGS Publications Warehouse

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

    2009-01-01

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

  4. Turbulent - laminar transition in the propagation of height-contained hydraulic fracture.

    NASA Astrophysics Data System (ADS)

    Zia, Haseeb; Lecampion, Brice

    2016-04-01

    Fluid flow is usually assumed to be laminar in the modelling of hydraulic fracture propagation. This approximation can however break down in certain cases where a low viscosity fluid (e.g. water) is injected at a high rate resulting in Reynolds numbers well into the turbulent flow regime. This is notably the case of hydraulic fracture propagation at glacier beds where Reynolds numbers above 100,000 are expected (Tsai and Rice 2010). Recent trend of high injection rate slickwater treatment for the hydraulic fracturing of oil and gas wells has also called the validity of the laminar flow assumption into question. Ames & Bunger (2015) recently investigated the effect of fully rough turbulent flow on the propagation of a height contained hydraulic fracture (Perkins & Kern 1961, Nordgren 1972). They have shown via dimensional analysis that the characteristic pressure should be larger and length shorter in the fully turbulent-rough regime compared to the laminar case. However, in practice, the range of Reynolds numbers for a typical slickwater treatment is expected to be from 1000 to 100,000 which coincides with the transition range from the fully laminar to fully turbulent-rough flows. Moreover, the Reynolds number is also expected to drop significantly in the tip region of a hydraulic fracture as the fracture width tends to zero. We present a numerical model that accommodates the complete laminar-turbulent transition of the flow and its impact on the propagation of a height contained hydraulic fracture. The numerical model is based on an explicit non-oscillatory central scheme for the solution of the coupled system of equations governing fluid flow and fracture elastic deformation. A volume of fluid method is used for tracking of the fracture front. The accuracy of the scheme is validated against the classical solution for the laminar flow regime. The relevance of the different limiting approximations (i.e. fully laminar versus fully turbulent regime) to simulate

  5. 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.

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

    USGS Publications Warehouse

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

    2015-01-01

    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.

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

    PubMed

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

    2009-01-26

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

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

    USGS Publications Warehouse

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

    2009-01-01

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

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

    SciTech Connect

    Mike L. Laue

    1998-02-05

    This project attempts to demonstrate the effectivensss of exploiting thin-layered, low energy deposits at the distal margin of a propagating turbinite complex through u se of hydraulically fractgured horizontal of high-angle wells. TGhe combinaton of a horizontal or high-angle weoo 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.

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

    NASA Astrophysics Data System (ADS)

    Hayashi, Kazuo; Haimson, Bezalel C.

    1991-10-01

    Characteristics of pressure decay curves obtained after shut-in in hydraulic fracturing stress measurements are studied in detail in an effort to enhance the reliability of the minimum compressive in situ stress determination. The analysis utilizes linear theory of elasticity, fracture mechanics, and global mass balance of fracturing fluid after shut-in. A small amount of crack growth takes place almost instantaneously just after shut-in due to equilibration of injected-fluid pressure within the fracture. Thereafter, the fracture gradually closes commensurate with the amount of fluid leakage into the rock and the net compliance of the pressured system consisting of the rock, the fracture, and the tubing conveying pressurized fluid from the surface to the depth of testing. Theoretical considerations and laboratory and field data suggest the closure process after shut-in can be considered to consist of three major stages: from cessation of fracture growth until fracture tip closure (stage I), from just after fracture tip closure until complete fracture closure (stage II), and from just after complete fracture closure until the test is stopped (stage III). An analysis of these stages reveals that the inverse of the pressure decrease rate is linear with respect to the fluid pressure in stages I and III. It is also shown that the far-field minimum compressive stress can be determined on the basis of these characteristics. The method of determination of the in situ minimum compressive stress is successfully applied to a sampling of shut-in curves obtained in laboratory and field experiments.

  11. 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.

  12. Modeling the Interaction Between Hydraulic and Natural Fractures Using Dual-Lattice Discrete Element Method

    SciTech Connect

    Zhou, Jing; Huang, Hai; Deo, Milind

    2015-10-01

    The interaction between hydraulic fractures (HF) and natural fractures (NF) will lead to complex fracture networks due to the branching and merging of natural and hydraulic fractures in unconventional reservoirs. In this paper, a newly developed hydraulic fracturing simulator based on discrete element method is used to predict the generation of complex fracture network in the presence of pre-existing natural fractures. By coupling geomechanics and reservoir flow within a dual lattice system, this simulator can effectively capture the poro-elastic effects and fluid leakoff into the formation. When HFs are intercepting single or multiple NFs, complex mechanisms such as direct crossing, arresting, dilating and branching can be simulated. Based on the model, the effects of injected fluid rate and viscosity, the orientation and permeability of NFs and stress anisotropy on the HF-NF interaction process are investigated. Combined impacts from multiple parameters are also examined in the paper. The numerical results show that large values of stress anisotropy, intercepting angle, injection rate and viscosity will impede the opening of NFs.

  13. Buckling and hydraulic mechanisms in orbital blowout fractures: fact or fiction?

    PubMed

    Ahmad, Fateh; Kirkpatrick, Niall A; Lyne, Jonathan; Urdang, Michael; Waterhouse, Norman

    2006-05-01

    Since the first description of orbital blowout fractures, there has been much confusion as to their etiology. Two principal mechanisms have been proposed to explain their production, the buckling and the hydraulic mechanisms caused, respectively, by trauma to the orbital rim and the globe of the eye. The aim of this study was to evaluate both mechanisms qualitatively and quantitatively. Our protocol used intact cadavers, quantifiable intraocular pressure, variable and quantifiable force, and quantifiable bone strain distribution with strain gauge analysis. One orbit of each cadaver was used to simulate each of the two mechanisms, allowing direct comparison. Fractures produced by the buckling mechanism were limited to the anterior part of the orbital floor, with strain readings reaching up to 3756 microepsilon. Posteriorly, strain did not exceed 221 microepsilon. In contrast, hydraulic-type fractures were much larger, involving anterior and posterior parts of the floor as well as the medial wall of the orbit. Here, strain exceeded 3756 microepsilon in both parts of the floor. Furthermore, we have demonstrated that the average energy required to fracture the orbital floor by the buckling mechanism is 1.54 J, whereas an average energy of 1.22 J is needed to produce this fracture by the hydraulic mechanism. Our results suggest that efforts to establish one or another mechanism as the primary etiology are misplaced. Both mechanisms produce orbital blowout fractures, with different and specific characteristics. We believe this provides the basis for our reclassification of such fractures.

  14. Mixed integer simulation optimization for optimal hydraulic fracturing and production of shale gas fields

    NASA Astrophysics Data System (ADS)

    Li, J. C.; Gong, B.; Wang, H. G.

    2016-08-01

    Optimal development of shale gas fields involves designing a most productive fracturing network for hydraulic stimulation processes and operating wells appropriately throughout the production time. A hydraulic fracturing network design-determining well placement, number of fracturing stages, and fracture lengths-is defined by specifying a set of integer ordered blocks to drill wells and create fractures in a discrete shale gas reservoir model. The well control variables such as bottom hole pressures or production rates for well operations are real valued. Shale gas development problems, therefore, can be mathematically formulated with mixed-integer optimization models. A shale gas reservoir simulator is used to evaluate the production performance for a hydraulic fracturing and well control plan. To find the optimal fracturing design and well operation is challenging because the problem is a mixed integer optimization problem and entails computationally expensive reservoir simulation. A dynamic simplex interpolation-based alternate subspace (DSIAS) search method is applied for mixed integer optimization problems associated with shale gas development projects. The optimization performance is demonstrated with the example case of the development of the Barnett Shale field. The optimization results of DSIAS are compared with those of a pattern search algorithm.

  15. Hydromechanical Normal Deformation Experiments and Coupling to Fracture Surface Geometry

    NASA Astrophysics Data System (ADS)

    Thörn, J.; Fransson, A. M.

    2015-12-01

    Civil engineering structures founded in fractured crystalline rock, such as the Fennoscandian Shield (Norway-Sweden-Finland) requires allowance for both stability and/or deformations of the rock mass and groundwater ingress and groundwater pressure changes. Coupling these issues could be the key to solving the challenges that arise from construction of e.g. hydropower dams, road and railroad tunnels, and most certainly the construction of nuclear waste repositories within fractured crystalline rock, all of which are currently planned in Sweden. Excavation related deformation in fractures may cause groundwater leakage even from the most elaborate pre-excavation grouting works. A better understanding on hydraulically (or grouting) induced deformations in the near-field of tunnels, where the stress field is re-distributed due to the opening may both provide a basis for more accurate numerical modelling and grouting or excavation procedures that minimize the damage on the completed grouting fans. Subjects of this study were experiments conducted as measurement of deformations in boreholes close to tunnels due to stepwise injection tests, and laboratory hydromechanical experiments conducted as flow and normal deformation measurements in a permeameter during cycles of up to 2.5 MPa confining pressure, and subsequent surface scanning of the samples for coupling of HM-results to geometric appearance, aperture and contact geometry. When expressed in terms of hydraulic aperture (b) and fracture normal stiffness (kn) the results of both in situ and lab experiments support a previously suggested relationship based on field data where kn is inversely proportional to roughly b2. The relationship was assumed to be valid for low compressive stress across fractures with limited previous deformation. One important data set used to establish the relationship was transmissivity and storage coefficients from hydraulic interference tests previously performed at Äspö Hard Rock

  16. Understanding the Geometry of Connected Fracture Flow with Multiperiod Oscillatory Hydraulic Tests.

    PubMed

    Sayler, Claire; Cardiff, Michael; Fort, Michael D

    2017-08-15

    An understanding of the spatial and hydraulic properties of fast preferential flow pathways in the subsurface is necessary in applications ranging from contaminant fate and transport modeling to design of energy extraction systems. One method for the characterization of fracture properties over interwellbore scales is Multiperiod Oscillatory Hydraulic (MOH) testing, in which the aquifer response to oscillatory pressure stimulations is observed. MOH tests were conducted on isolated intervals of wells in siliciclastic and carbonate aquifers in southern Wisconsin. The goal was to characterize the spatial properties of discrete fractures over interwellbore scales. MOH tests were conducted on two discrete fractured intervals intersecting two boreholes at one field site, and a nest of three piezometers at another field site. Fracture diffusivity estimates were obtained using analytical solutions that relate diffusivity to observed phase lag and amplitude decay. In addition, MOH tests were used to investigate the spatial extent of flow using different conceptual models of fracture geometry. Results indicated that fracture geometry at both field sites can be approximated by permeable two-dimensional fracture planes, oriented near-horizontally at one site, and near-vertically at the other. The technique used on MOH field data to characterize fracture geometry shows promise in revealing fracture network characteristics important to groundwater flow and transport. © 2017, National Ground Water Association.

  17. Measurement and Analysis of Full-Scale Hydraulic Fracture Initiation and Reorientation

    NASA Astrophysics Data System (ADS)

    Jeffrey, R. G.; Chen, Z. R.; Zhang, X.; Bunger, A. P.; Mills, K. W.

    2015-11-01

    Hydraulic fracture breakdown and reorientation data collected from two instrumented test borehole sites have been analyzed to assess the effect of the initiation type (axial or transverse) on the treating pressure. Vertical boreholes were drilled and fractures were placed in a conglomerate at depths of 140-180 m in a far-field stress field that favored horizontal fracture growth. Axial initiation resulted in high injection pressure, which was attributed to near-borehole tortuosity generated as the hydraulic fracture reoriented to align with the far-field stresses. Acoustic scanner logging of the boreholes after fracturing demonstrated that, in many cases, axial initiation occurred and when this was the case, treating pressures were high and consistent with near-borehole tortuous fracture paths. A fracture initiation analysis determined that initiation at abrasively cut circumferential slots should occur before axial initiation. Slots were cut to locate the initiation sites and to make transverse fracture initiation more likely. Transverse initiation from the vertical boreholes at pre-cut slots lowered the injection pressures during the fracture treatment by up to 12 MPa for water injected at approximately 500 L per minute.

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

    USGS Publications Warehouse

    Williams, J.H.; Paillet, Frederick 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.

  19. 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...

  20. 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...

  1. 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.

  2. Hydraulic fracturing to enhance the remediation of DNAPL in low permeability soils

    SciTech Connect

    Murdoch, L.; Slack, B.

    1996-08-01

    Meager rates of fluid flow are a major obstacle to in situ remediation of low permeability soils. This paper describes methods designed to avoid that obstacle by creating fractures and filling them with sand to increase well discharge and change paths of fluid flow in soil. Gently dipping fractures 10 m in maximum dimension and 1 to 2 cm thick can be created in some contaminated soils at depths of a few in or greater. Hydraulic fractures can also be used to create electrically conductive layers or to deliver granules of chemically or biologically active compounds that will degrade contaminants in place. Benefits of applying hydraulic fractures to DNAPL recovery include rates of fluid recovery, enhancing upward gradients to improve hydrodynamic stabilization, forming flat-lying reactive curtains to intersect compounds moving downward, or improving the performance of electrokinetics intended to recover compounds dissolved in water. 30 refs., 7 figs., 1 tab.

  3. Draft Genome Sequence of Methanohalophilus mahii Strain DAL1 Reconstructed from a Hydraulic Fracturing-Produced Water Metagenome

    PubMed Central

    Lipus, Daniel; Vikram, Amit

    2016-01-01

    We report here the 1,882,100-bp draft genome sequence of Methanohalophilus mahii strain DAL1, recovered from Marcellus Shale hydraulic fracturing-produced water using metagenomic contig binning. Genome annotation revealed several key methanogenesis genes and provides valuable information on archaeal activity associated with hydraulic fracturing-produced water environments. PMID:27587817

  4. 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...

  5. 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...

  6. Draft Genome Sequence of Methanohalophilus mahii Strain DAL1 Reconstructed from a Hydraulic Fracturing-Produced Water Metagenome.

    PubMed

    Lipus, Daniel; Vikram, Amit; Ross, Daniel E; Bibby, Kyle

    2016-09-01

    We report here the 1,882,100-bp draft genome sequence of Methanohalophilus mahii strain DAL1, recovered from Marcellus Shale hydraulic fracturing-produced water using metagenomic contig binning. Genome annotation revealed several key methanogenesis genes and provides valuable information on archaeal activity associated with hydraulic fracturing-produced water environments.

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

    EPA Science Inventory

    As the use of hydraulic fracturing has increased, concerns have been raised about potential public health effects that may arise if hydraulic fracturing-related chemicals were to impact drinking water resources. This study presents an overview of the chronic oral toxicity values—...

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

    EPA Science Inventory

    As the use of hydraulic fracturing has increased, concerns have been raised about potential public health effects that may arise if hydraulic fracturing-related chemicals were to impact drinking water resources. This study presents an overview of the chronic oral toxicity values—...

  9. Assessing the induced seismicity by hydraulic fracturing at the Wysin site (Poland)

    NASA Astrophysics Data System (ADS)

    Ángel López Comino, José; Cesca, Simone; Kriegerowski, Marius; Heimann, Sebastian; Dahm, Torsten; Mirek, Janusz; Lasocky, Stanislaw

    2017-04-01

    Induced seismicity related to industrial processes including shale gas and oil exploitation is a current issues that implies enough reasons to be concerned. Hydraulic fracturing usually induces weak events. However, scenarios with larger earthquakes are possible, e.g. if the injected fluids alter friction conditions and trigger the failure of neighbouring faults. This work is focused on a hydrofracking experiment monitored in the framework of the SHEER (SHale gas Exploration and Exploitation induced Risks) EU project at the Wysin site, located in the central-western part of the Peribaltic synclise of Pomerania, Poland. A specific network setup has been installed combining surface installation with three small-scale arrays and a shallow borehole installation. The fracking operations were carried out in June and July 2016 at a depth 4000 m. The monitoring has been operational before, during and after the termination of hydraulic fracturing operations. We apply a recently developed automated full waveform detection algorithm based on the stacking of smooth characteristic function and the identification of high coherence in the signals recorded at different stations. The method was tested with synthetic data and different detector levels yielding values of magnitude of completeness around 0.1. An unsupervised detection catalogue is generated with real data for a time period May-September 2016. We identify strong temporal changes (day/night) of the detection performance. A manual revision of the detected signals reveals that most detections are associated to local and regional seismic signals. Only two events could be assigned to the volume potentially affected by the fracking operations.

  10. 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.

  11. Numerical Study of Critical Role of Rock Heterogeneity in Hydraulic Fracture Propagation

    SciTech Connect

    J. Zhou; H. Huang; M. Deo

    2016-03-01

    Log and seismic data indicate that most shale formations have strong heterogeneity. Conventional analytical and semi-analytical fracture models are not enough to simulate the complex fracture propagation in these highly heterogeneous formation. Without considering the intrinsic heterogeneity, predicted morphology of hydraulic fracture may be biased and misleading in optimizing the completion strategy. In this paper, a fully coupling fluid flow and geomechanics hydraulic fracture simulator based on dual-lattice Discrete Element Method (DEM) is used to predict the hydraulic fracture propagation in heterogeneous reservoir. The heterogeneity of rock is simulated by assigning different material force constant and critical strain to different particles and is adjusted by conditioning to the measured data and observed geological features. Based on proposed model, the effects of heterogeneity at different scale on micromechanical behavior and induced macroscopic fractures are examined. From the numerical results, the microcrack will be more inclined to form at the grain weaker interface. The conventional simulator with homogeneous assumption is not applicable for highly heterogeneous shale formation.

  12. Elucidating hydraulic fracturing impacts on groundwater quality using a regional geospatial statistical modeling approach.

    PubMed

    Burton, Taylour G; Rifai, Hanadi S; Hildenbrand, Zacariah L; Carlton, Doug D; Fontenot, Brian E; Schug, Kevin A

    2016-03-01

    Hydraulic fracturing operations have been viewed as the cause of certain environmental issues including groundwater contamination. The potential for hydraulic fracturing to induce contaminant pathways in groundwater is not well understood since gas wells are completed while isolating the water table and the gas-bearing reservoirs lay thousands of feet below the water table. Recent studies have attributed ground water contamination to poor well construction and leaks in the wellbore annulus due to ruptured wellbore casings. In this paper, a geospatial model of the Barnett Shale region was created using ArcGIS. The model was used for spatial analysis of groundwater quality data in order to determine if regional variations in groundwater quality, as indicated by various groundwater constituent concentrations, may be associated with the presence of hydraulically fractured gas wells in the region. The Barnett Shale reservoir pressure, completions data, and fracture treatment data were evaluated as predictors of groundwater quality change. Results indicated that elevated concentrations of certain groundwater constituents are likely related to natural gas production in the study area and that beryllium, in this formation, could be used as an indicator variable for evaluating fracturing impacts on regional groundwater quality. Results also indicated that gas well density and formation pressures correlate to change in regional water quality whereas proximity to gas wells, by itself, does not. The results also provided indirect evidence supporting the possibility that micro annular fissures serve as a pathway transporting fluids and chemicals from the fractured wellbore to the overlying groundwater aquifers.

  13. 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

  14. 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.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

    Tomac, I.; Gutierrez, M.

    2015-12-01

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

  17. Multiscale pore networks and their effect on deformation and transport property alteration associated with hydraulic fracturing

    NASA Astrophysics Data System (ADS)

    Daigle, Hugh; Hayman, Nicholas; Jiang, Han; Tian, Xiao; Jiang, Chunbi

    2017-04-01

    clusters of organic-hosted pores prevents the overpressure from dissipating, resulting in localized overpressure at the micron scale. When the rock is subjected to a hydraulic fracture stimulation, the rock surrounding the main induced fracture experiences shear deformation. Those parts of the rock that contain overpressured fluids in the organic-hosted pores will be more likely to experience dilatancy in the form of brittle deformation; the portions of the rock lacking in organic-hosted pores will tend to experience compactive shear failure since the effective normal stresses are larger. The microcrack networks that propagate into the regions of organic-hosted porosity allow the hydrocarbons resident in those pores to migrate to the main induced tensile fractures. The disconnected nature of the microcrack networks causes only a slight increase in permeability, which is consistent with other observations. Our work illustrates how multiscale pore networks in shale interact with in situ stresses to affect the bulk shale rheology.

  18. 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

  19. Hydraulic fracturing model featuring initiation beyond the wellbore wall for directional well in coal bed

    NASA Astrophysics Data System (ADS)

    Li, Yuwei; Jia, Dan; Wang, Meng; Liu, Jia; Fu, Chunkai; Yang, Xinliang; Ai, Chi

    2016-08-01

    In developing internal fracture systems in coal beds, the initiation mechanism differs greatly from that of conventional ones and initiations may be produced beyond the wellbore wall. This paper describes the features of the internal structure of coal beds and RFPA2D simulation is used to attest the possible occurrence of initiation beyond the wellbore wall in coal bed hydraulic fracturing. Using the theory of elasticity and fracture mechanics, we analyse the stress distribution in the vicinal coal rock. Then by taking into consideration the effects of the spatial relationship between coal bed cleats and the wellbore, we establish a model for calculating both tensile and shear initiation pressure that occur along cleats beyond the wellbore wall. The simulation in this paper indicates that for shear initiations that happen along coal cleats, the pressure required to initiate fracture for cleats beyond the wellbore wall is evidently lower than that on the wellbore wall, thus it is easier to initiate shear fractures for cleats beyond the wellbore wall. For tensile failure, the pressure required to initiate tensile fracture for cleats beyond the wellbore wall is obviously higher than that for cleats at the wellbore wall, thus it is easier to initiate tensile fractures for cleats at the wellbore wall. On the one hand, this paper has proved the possible occurrence of initiations beyond the wellbore wall and has changed the current assumption that hydraulic fractures can only occur at the wellbore wall. On the other hand, the established theoretical model provides a new approach to calculating the initiation pressure in hydraulic fracturing.

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

    EPA Science Inventory

    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...

  1. Chloride concentration gradients in tank-stored hydraulic fracturing fluids following flowback

    Treesearch

    Pamela J. Edwards; Linda L. Tracy; William K. Wilson

    2011-01-01

    A natural gas well in West Virginia was hydraulically fractured and the flowback was recovered and stored in an 18-foot-deep tank. Both in situ field test kit and laboratory measurements of electrical conductivity and chloride concentrations increased substantially with depth, although the laboratory measurements showed a greater increase. The field test kit also...

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

    EPA Science Inventory

    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...

  3. IG Statement: EPA Inspector General Responds to Sen. Inhofe's Letter about Review of Hydraulic Fracturing

    EPA Pesticide Factsheets

    EPA IG Arthur Elkins Jr. responded to Sen. James Inhofe’s Oct 2, 2014, letter asserting that the EPA OIG should not proceed with a program evaluation of the EPA’s and states’ ability to manage potential threats to water resources from hydraulic fracturing.

  4. 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... announcing four (4) public informational meetings to explain its proposed plan to study the relationship.... EPA will provide the public with information about the Agency's preliminary plans for study scope and...

  5. 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.

  6. 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

    ... Bureau of Land Management 43 CFR Part 3160 RIN 1004-AE26 Oil and Gas; Well Stimulation, Including... public land and Indian land, strengthen regulations related to well- bore integrity, and address issues... ensure that hydraulic fracturing is conducted in a way that adequately protects the environment. Due...

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

    USGS Publications Warehouse

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

    1994-01-01

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

  8. Development of hydraulic fracture network propagation model in shale gas reservoirs: 2D, single-phase and 3D, multi-phase model development, parametric studies, and verification

    NASA Astrophysics Data System (ADS)

    Ahn, Chong Hyun

    The most effective method for stimulating shale gas reservoirs is a massive hydraulic fracture treatment. Recent analysis using microseismic technology have shown that complex fracture networks are commonly created in the field as a result of the stimulation of shale wells. The interaction between pre-existing natural fractures and the propagating hydraulic fracture is a critical factor affecting the created complex fracture network; however, many existing numerical models simulate only planar hydraulic fractures without considering the pre-existing fractures in the formation. The shale formations already contain a large number of natural fractures, so an accurate fracture propagation model needs to be developed to optimize the fracturing process. In this research, we first characterized the mechanics of hydraulic fracturing and fluid flow in the shale gas reservoir. Then, a 2D, single-phase numerical model and a 3D, 2-phase coupled model were developed, which integrate dynamic fracture propagation, interactions between hydraulic fractures and pre-existing natural fractures, fracture fluid leakoff, and fluid flow in a petroleum reservoir. By using the developed model, we conducted parametric studies to quantify the effects of treatment rate, treatment size, fracture fluid viscosity, differential horizontal stress, natural fracture spacing, fracture toughness, matrix permeability, and proppant size on the geometry of the hydraulic fracture network. The findings elucidate important trends in hydraulic fracturing of shale reservoirs that are useful in improving the design of treatments for specific reservoir settings.

  9. Natural hydraulic fractures and the mechanical stratigraphy of shale-dominated strata

    NASA Astrophysics Data System (ADS)

    Imber, Jonathan; Armstrong, Howard; Atar, Elizabeth; Clancy, Sarah; Daniels, Susan; Grattage, Joshua; Herringshaw, Liam; Trabucho-Alexandre, João; Warren, Cassandra; Wille, Jascha; Yahaya, Liyana

    2016-04-01

    The aim of this study is to investigate stratigraphic variations in the spatial distribution and density of natural hydraulic and other fractures within oil mature, shale-dominated strata from the Cleveland Basin, northeast England. The studied interval includes the Pliensbachian Cleveland Ironstone and Toarcian Whitby Mudstone Formations. The Cleveland Ironstone Formation (ca. 25m thick) consists of silt- and mudstone units with discrete ironstone layers (seams). Ironstones account for 20% of the thickness of the formation. The Whitby Mudstone Formation is up to ca. 100 m thick; up to 2% of its total thickness consists of discrete calcium carbonate horizons, such as the Top Jet Dogger. Natural hydraulic fractures, characterised by plumose marks and concentric arrest lines on fracture surfaces are ubiquitous throughout both formations; shear fractures with mm- to cm-scale displacements occur locally, particularly within silt- and mudstones. Natural hydraulic fractures locally contain thin, sometimes fibrous, calcite fills and are commonly observed to terminate at bedding plane interfaces between silt- or mudstone and carbonate beds. We have recorded fracture locations and apertures along 139 transects in both shale (i.e. silt- and mudstone intervals) and carbonate strata. Natural hydraulic and shear fractures, measured along transects up to 50m long within all lithologies in both formations, typically display uniform distributions. There is no correlation between spacing distribution and bulk extension in any lithology. Median fracture densities recorded within the Cleveland Ironstone Formation are higher in intervening ironstone beds (<2.1 fractures per m in ironstone layers) compared with dominant shales (<0.9 fractures per m in silt- and mudstones). A qualitatively similar pattern occurs within the Whitby Mudstone Formation. However, the absolute values of median fracture density within different members of the Whitby Mudstone Formation range from 2

  10. Scale dependence of the hydraulic properties of a fractured aquifer estimated using transfer functions

    NASA Astrophysics Data System (ADS)

    Pedretti, D.; Russian, A.; Sanchez-Vila, X.; Dentz, M.

    2016-07-01

    We present an investigation of the scale dependence of hydraulic parameters in fractured media based on the concept of transfer functions (TF). TF methods provide an inexpensive way to perform aquifer parameter estimation, as they relate the fluctuations of an observation time series (hydraulic head fluctuations) to an input function (aquifer recharge) in frequency domain. Fractured media are specially sensitive to this approach as hydraulic parameters are strongly scale-dependent, involving nonstationary statistical distributions. Our study is based on an extensive data set, involving up to 130 measurement points with periodic head measurements that in some cases extend for more than 30 years. For each point, we use a single-porosity and dual-continuum TF formulation to obtain a distribution of transmissivities and storativities in both mobile and immobile domains. Single-porosity TF estimates are compared with data obtained from the interpretation of over 60 hydraulic tests (slug and pumping tests). Results show that the TF is able to estimate the scale dependence of the hydraulic parameters, and it is consistent with the behavior of estimates from traditional hydraulic tests. In addition, the TF approach seems to provide an estimation of the system variance and the extension of the ergodic behavior of the aquifer (estimated in approximately 500 m in the analyzed aquifer). The scale dependence of transmissivity seems to be independent from the adopted formulation (single or dual-continuum), while storativity is more sensitive to the presence of multiple continua.

  11. A New Physics-Based Modeling of Multiple Non-Planar Hydraulic Fractures Propagation

    SciTech Connect

    Zhou, Jing; Huang, Hai; Deo, Milind; Jiang, Shu

    2015-10-01

    Because of the low permeability in shale plays, closely spaced hydraulic fractures and multilateral horizontal wells are generally required to improve production. Therefore, understanding the potential fracture interaction and stress evolution is critical in optimizing fracture/well design and completion strategy in multi-stage horizontal wells. In this paper, a novel fully coupled reservoir flow and geomechanics model based on the dual-lattice system is developed to simulate multiple non-planar fractures propagation. The numerical model from Discrete Element Method (DEM) is used to simulate the mechanics of fracture propagations and interactions, while a conjugate irregular lattice network is generated to represent fluid flow in both fractures and formation. The fluid flow in the formation is controlled by Darcy’s law, but within fractures it is simulated by using cubic law for laminar flow through parallel plates. Initiation, growth and coalescence of the microcracks will lead to the generation of macroscopic fractures, which is explicitly mimicked by failure and removal of bonds between particles from the discrete element network. We investigate the fracture propagation path in both homogeneous and heterogeneous reservoirs using the simulator developed. Stress shadow caused by the transverse fracture will change the orientation of principal stress in the fracture neighborhood, which may inhibit or alter the growth direction of nearby fracture clusters. However, the initial in-situ stress anisotropy often helps overcome this phenomenon. Under large in-situ stress anisotropy, the hydraulic fractures are more likely to propagate in a direction that is perpendicular to the minimum horizontal stress. Under small in-situ stress anisotropy, there is a greater chance for fractures from nearby clusters to merge with each other. Then, we examine the differences in fracture geometry caused by fracturing in cemented or uncemented wellbore. Moreover, the impact of

  12. Experimental Study of the Roles of Mechanical and Hydrologic Properties in the Initiation of Natural Hydraulic Fractures

    NASA Astrophysics Data System (ADS)

    French, M. E.; Goodwin, L. B.; Boutt, D. F.; Lilydahl, H.

    2008-12-01

    Natural hydraulic fractures (NHFs) are inferred to form where pore fluid pressure exceeds the least compressive stress; i.e., where the hydraulic fracture criterion is met. Although it has been shown that mechanical heterogeneities serve as nuclei for NHFs, the relative roles of mechanical anisotropy and hydrologic properties in initiating NHFs in porous granular media have not been fully explored. We designed an experimental protocol that produces a pore fluid pressure high enough to exceed the hydraulic fracture criterion, allowing us to initiate NHFs in the laboratory. Initially, cylindrical samples 13 cm long and 5 cm in diameter are saturated, σ1 is radial, and σ3 is axial. By dropping the end load (σ3) and pore fluid pressure simultaneously at the end caps, we produce a large pore fluid pressure gradient parallel to the long axis of the sample. This allows us to meet the hydraulic fracture criterion without separating the sample from its end caps. The time over which the pore fluid remains elevated is a function of hydraulic diffusivity. An initial test with a low diffusivity sandstone produced NHFs parallel to bedding laminae that were optimally oriented for failure. To evaluate the relative importance of mechanical heterogeneities such as bedding versus hydraulic properties, we are currently investigating variably cemented St. Peter sandstone. This quartz arenite exhibits a wide range of primary structures, from well developed bedding laminae to locally massive sandstone. Diagenesis has locally accentuated these structures, causing degree of cementation to vary with bedding, and the sandstone locally exhibits concretions that form elliptical rather than tabular heterogeneities. Bulk permeability varies from k=10-12 m2 to k=10-15 m2 and porosity varies from 5% to 28% in this suite of samples. Variations in a single sample are smaller, with permeability varying no more than an order of magnitude within a single core. Air minipermeameter and tracer tests

  13. Fully coupled simulation of multiple hydraulic fractures to propagate simultaneously from a perforated horizontal wellbore

    NASA Astrophysics Data System (ADS)

    Zeng, Qinglei; Liu, Zhanli; Wang, Tao; Gao, Yue; Zhuang, Zhuo

    2017-05-01

    In hydraulic fracturing process in shale rock, multiple fractures perpendicular to a horizontal wellbore are usually driven to propagate simultaneously by the pumping operation. In this paper, a numerical method is developed for the propagation of multiple hydraulic fractures (HFs) by fully coupling the deformation and fracturing of solid formation, fluid flow in fractures, fluid partitioning through a horizontal wellbore and perforation entry loss effect. The extended finite element method (XFEM) is adopted to model arbitrary growth of the fractures. Newton's iteration is proposed to solve these fully coupled nonlinear equations, which is more efficient comparing to the widely adopted fixed-point iteration in the literatures and avoids the need to impose fluid pressure boundary condition when solving flow equations. A secant iterative method based on the stress intensity factor (SIF) is proposed to capture different propagation velocities of multiple fractures. The numerical results are compared with theoretical solutions in literatures to verify the accuracy of the method. The simultaneous propagation of multiple HFs is simulated by the newly proposed algorithm. The coupled influences of propagation regime, stress interaction, wellbore pressure loss and perforation entry loss on simultaneous propagation of multiple HFs are investigated.

  14. Determination of hydraulic fracture parameters using a non-stationary fluid injection

    NASA Astrophysics Data System (ADS)

    Valov, A. V.; Golovin, S. V.

    2016-06-01

    In this paper, one provides a theoretical justification of the possibility of hydraulic fracture parameters determination by using a non-stationary fluid injection. It is assumed that the fluid is pumped into the fractured well with the time-periodic flow rate. It is shown that there is a phase shift between waves of fluid pressure and velocity. For the modelling purposes, the length and width of the fracture are assumed to be fixed. In the case of infinite fracture, one constructs an exact solution that ensures analytical determination of the phase shift in terms of the physical parameters of the problem. In the numerical calculation, the phase shift between pressure and velocity waves is found for a finite fracture. It is shown that the value of the phase shift depends on the physical parameters and on the fracture geometry. This makes it possible to determine parameters of hydraulic fracture, in particular its length, by the experimental measurement of the time shift and comparison with the numerical solution.

  15. Semi-analytical model of cross-borehole flow experiments for fractured medium characterization

    NASA Astrophysics Data System (ADS)

    Roubinet, D.; Irving, J.; Day-Lewis, F. D.

    2014-12-01

    The study of fractured rocks is extremely important in a wide variety of research fields where the fractures and faults can represent either rapid access to some resource of interest or potential pathways for the migration of contaminants in the subsurface. Identification of their presence and determination of their properties are critical and challenging tasks that have led to numerous fracture characterization methods. Among these methods, cross-borehole flowmeter analysis aims to evaluate fracture connections and hydraulic properties from vertical-flow-velocity measurements conducted in one or more observation boreholes under forced hydraulic conditions. Previous studies have demonstrated that analysis of these data can provide important information on fracture connectivity, transmissivity, and storativity. Estimating these properties requires the development of analytical and/or numerical modeling tools that are well adapted to the complexity of the problem. Quantitative analysis of cross-borehole flowmeter experiments, in particular, requires modeling formulations that: (i) can be adapted to a variety of fracture and experimental configurations; (ii) can take into account interactions between the boreholes because their radii of influence may overlap; and (iii) can be readily cast into an inversion framework that allows for not only the estimation of fracture hydraulic properties, but also an assessment of estimation error. To this end, we present a new semi-analytical formulation for cross-borehole flow in fractured media that links transient vertical-flow velocities measured in one or a series of observation wells during hydraulic forcing to the transmissivity and storativity of the fractures intersected by these wells. Our model addresses the above needs and provides a flexible and computationally efficient semi-analytical framework having strong potential for future adaptation to more complex configurations. The proposed modeling approach is demonstrated

  16. 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.

  17. Characteristics of high resolution hydraulic head profiles and vertical gradients in fractured sedimentary rocks

    NASA Astrophysics Data System (ADS)

    Meyer, Jessica R.; Parker, Beth L.; Cherry, John A.

    2014-09-01

    Accurately identifying the position of vertical hydraulic conductivity (Kv) contrasts is critical to the delineation of hydrogeologic units that serve as the basis for conceptual and numerical models of groundwater flow. High resolution head profiles have identified the position and thickness of Kv contrasts in clayey aquitards but this potential has not yet been thoroughly evaluated in sedimentary rocks. This paper describes an experiment in which head profiles with the highest, technically feasible resolution were obtained using Westbay® multilevel systems (MLS) installed in 15 cored holes at three sedimentary rock research sites with contrasting geologic and flow system conditions. MLSs were installed to maximum depths between 90 and 260 m with 2-5 monitoring zones per 10 m. Head profiles were measured over multiyear periods. The vertical component of hydraulic gradient (i.e., vertical gradient) was calculated for each pair of adjacent monitoring intervals in every MLS and then categorized based on its repeatability to facilitate interpretation of Kv contrasts and comparisons within boreholes, between boreholes at the same site, and between sites. The head and vertical gradient profiles from all three sites display systematic (i.e., simple, geometric) shapes defined by repeatable intervals of no to minimal vertical gradient, indicating relatively high Kv units, bounded by shorter depth intervals with large (up to -50 m/m) vertical gradients, indicating relatively low Kv units. The systematic nature of the profiles suggests flow in regular and interconnected fracture networks rather than dominated by a few key fractures with irregular orientations. The low Kv units were typically thin, with their positions and thicknesses not predicted by lithostratigraphy or detailed lithologic, geophysical, and horizontal hydraulic conductivity data. Hence, the position and thickness of units with contrasting Kv would not be evident if MLSs with the conventional number of

  18. 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.

  19. Correlation between Induced Seismic Events and Hydraulic Fracturing activities in California

    NASA Astrophysics Data System (ADS)

    Walker, R.; Aminzadeh, F.; Tiwari, A.

    2014-12-01

    Induced seismicity observed in Oklahoma and Ohio have raised environmental concern to an alarming level and thus any plausible correlation between subsurface injection and production activities have become an significant area of study. As per US Seismic Hazard map, California lies in highly sensitive zone, which makes understanding of stimulation induced seismic events critically important. The copious number of seismic events due to presence of numerous faults in California benefits understanding seismicity of the region but makes it difficult to distinguish induced seismic events from naturally occurring seismic events. Since regional models are considered more effective in understanding the seismicity of the region, this study aims in understanding impact of hydraulic fracturing activities in various oilfields in California. The focus of the study is to identify sensitive zones in California which might have observed seismic activities induced due to hydraulic fracturing. This has been done using the criteria of spatial and temporal co-relation between fracturing activities and seismic events for oilfields with significant number of fracturing activities. The seismic and well data used for this study is acquired from public sources and have been integrated in an efficient manner using the GIS tool and iterative querying. The two step methodology implemented for this work involves segregating the induced seismic events from natural events based on the depth of the event and seismic history of the region and then spatially and temporally studying it with regards to hydraulic fracturing in vicinity of the seismic event.

  20. Statistical Analysis of Seismicity Associated with Hydraulic Fracturing in Western Canada

    NASA Astrophysics Data System (ADS)

    Shcherbakov, R.; Ghofrani, H.; Kothari, S.; Atkinson, G. M.; Cheadle, B.; Eaton, D. W. S.; Tiampo, K. F.

    2015-12-01

    The unconventional extraction of shale oil or gas is typically carried out by the subsurface injection of large volumes of fluids. The fluids are used in the process of hydraulic fracturing and subsequent wastewater injection into high volume disposal wells. These operations are usually accompanied by various levels of seismic activity and sometimes result in the occurrence of moderate to large earthquakes. It is suggested that the increase in seismic activity within the central U.S. in the last decade or so is primely associated with large-scale disposal of wastewater. The Western Canada Sedimentary Basin (WCSB) is an active exploration area for the extraction of oil and gas. The average rate of seismicity is lower than in the central U.S., however, there are several active clusters, where in the last 8-10 years, there has been an increase in the occurrence of moderate earthquakes. In this study, we analyze the statistical properties of seismicity associated with the WCSB. We find that the increase in seismicity rate is mostly associated with the hydraulic fracturing operations in several well defined spatial zones. Hydraulic fracturing involves high-pressure injections of fluids and is performed in multiple stages. This is done along horizontal wells which are drilled at average depths of 2 to 3 km. The triggering of large earthquakes is mostly due to injection of fluids into nearby tectonic faults which are close to failure. To model the rate of the occurrence of earthquakes we introduce a modified version of the Epidemic Type Aftershock Sequence model. The earthquake occurrence rate associated with several prominent clusters is characterized by bursts of activity associated with specifics of hydraulic fracturing operations. The proposed model can be used in the probabilistic assessment and mitigation of the risks associated with hydraulic fracturing.

  1. 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.

  2. Hydraulic characterization for steam enhanced remediation conducted in fractured rock.

    PubMed

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

    2006-01-10

    To explore the viability of Steam Enhanced Remediation (SER) in fractured rock a small-scale steam injection and water/vapour extraction pilot study was conducted at the former Loring Air Force Base in northern Maine, USA. A detailed well testing program was undertaken to assist in the design of the injection and extraction well array, and to assess the possibility of off-site heat and contaminant migration. A structurally complex limestone having low matrix porosity and a sparse distribution of fractures underlies the study site. To characterize the groundwater and steam flow pathways, single-well slug tests and more than 100 pulse interference tests were conducted. The results of the well testing indicate that the study site is dominated by steeply dipping bedding plane fractures that are interconnected only between some wells in the injection/extraction array. The SER system was designed to take advantage of interconnected fractures located at depth in the eastern end of the site. An array of 29 wells located in an area of 60 by 40 m was used for steam injection and water/vapour extraction. The migration of heat was monitored in several wells using thermistor arrays having a 1.5 m vertical spacing. Temperature measurements obtained during and after the 3 month steam injection period showed that heat migration generally occurred along those fracture features identified by the pulse interference testing. Based on these results, it is concluded that the pulse interference tests were valuable in assisting with the design of the injection/extraction well geometry and in predicting the migration pathways of the hot water associated with the steam injection. The pulse interference test method should also prove useful in support of any other remedial method dependant on the fracture network for delivery of remedial fluid or extraction of contaminants.

  3. 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.

  4. 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.

  5. 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

    Brittle materials fracture under tensile or shear stress. When stress attains a critical threshold, crack propagation becomes unstable and proceeds dynamically. 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 radically modified when the material susceptible to cracking is bonded to a poroelastic medium, such as a hydrogel, a common situation in biological tissues. In particular, we show that the brittle material can fracture in compression and can resist cracking in tension, thanks to the hydraulic coupling with the hydrogel. In the case of multiple cracks, we find that localized fracture occurs when the permeability of the hydrogel is high, whereas decreased permeability leads to toughening by promoting multiple cracking. Our results may contribute to the understanding of fracture in biological tissues and provide inspiration for the design of tough, biomimetic materials.

  6. Reactivity of Dazomet, a Hydraulic Fracturing Additive: Hydrolysis and Interaction with Pyrite

    NASA Astrophysics Data System (ADS)

    Consolazio, N.; Lowry, G. V.; Karamalidis, A.; Hakala, A.

    2015-12-01

    The Marcellus Shale is currently the largest shale gas formation in play across the world. The low-permeability formation requires hydraulic fracturing to be produced. In this process, millions of gallons of water are blended with chemical additives and pumped into each well to fracture the reservoir rock. Although additives account for less than 2% of the fracking fluid mixture, they amount to hundreds of tons per frack job. The environmental properties of some of these additives have been studied, but their behavior under downhole conditions is not widely reported in the peer-reviewed literature. These compounds and their reaction products may return to the surface as produced or waste water. In the event of a spill or release, this water has the potential to contaminate surface soil and water. Of these additives, biocides may present a formidable challenge to water quality. Biocides are toxic compounds (by design), typically added to the Marcellus Shale to control bacteria in the well. An assessment of the most frequently used biocides indicated a need to study the chemical dazomet under reservoir conditions. The Marcellus Shale contains significant deposits of pyrite. This is a ubiquitous mineral within black shales that is known to react with organic compounds in both oxic and anoxic settings. Thus, the objective of our study was to determine the effect of pyrite on the hydrolysis of dazomet. Liquid chromatography-triple quadrupole mass spectrometry (LC-QQQ) was used to calculate the loss rate of aqueous dazomet. Gas chromatography-mass spectrometry (GC-MS) was used to identify the reaction products. Our experiments show that in water, dazomet rapidly hydrolyses in water to form organic and inorganic transformation products. This reaction rate was unaffected when performed under anoxic conditions. However, with pyrite we found an appreciable increase in the removal rate of dazomet. This was accompanied by a corresponding change in the distribution of observed

  7. Hydraulic-fracture stimulation treatments at East Mesa, Well 58-30. Geothermal-reservoir well-stimulation program

    SciTech Connect

    Not Available

    1981-02-01

    East Mesa Well 58-30 was selected for two stimulation treatments: a conventional hydraulic fracture in a deep, low permeability interval, and a dendritic fracture in a shallow, high permeability interval of completion. The well selection, pre-stimulation evaluation, fracture treatment design, and post-stimulation evaluation are presented.

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

    PubMed

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

    2016-05-03

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

  9. Geochemical simulation of fluid rock interactions to predict flowback water compostions during hydraulic fracturing

    NASA Astrophysics Data System (ADS)

    Kühn, Michael; Vieth-Hillebrand, Andrea; Wilke, Franziska D. H.

    2017-04-01

    Black shales are a heterogeneous mixture of minerals, organic matter and formation water and little is actually known about the fluid-rock interactions during hydraulic fracturing and their effects on composition of flowback and produced water. Geochemical simulations have been performed based on the analyses of "real" flowback water samples and artificial stimulation fluids from lab experiments with the aim to set up a chemical process model for shale gas reservoirs. Prediction of flowback water compositions for potential or already chosen sites requires validated and parameterized geochemical models. For the software "Geochemist's Workbench" (GWB) data bases are adapted and amended based on a literature review. Evaluation of the system has been performed in comparison with the results from laboratory experiments. Parameterization was done in regard to field data provided. Finally, reaction path models are applied for quantitative information about the mobility of compounds in specific settings. Our work leads to quantitative estimates of reservoir compounds in the flowback based on calibrations by laboratory experiments. Such information is crucial for the assessment of environmental impacts as well as to estimate human- and ecotoxicological effects of the flowback waters from a variety of natural gas shales. With a comprehensive knowledge about potential composition and mobility of flowback water, selection of water treatment techniques will become easier.

  10. Assessment of the Impacts of Hydraulic Fracturing at Bakken on Regional Water Resources

    NASA Astrophysics Data System (ADS)

    Lin, Z.; Lin, T.; Lim, S.; Borders, M.

    2015-12-01

    Unconventional oil production at the Bakken Shale of western North Dakota increased more than ten-fold from 2008 to 2014. Although unconventional oil production uses less water than conventional oil production per unit of energy, the cumulative water needs for unconventional oil production due to multiple drilling and fracturing operations may be locally or temporally significant. We collected and analyzed the data for a total of 8453 horizontal wells developed at Bakken in western North Dakota during 2007-2014. The hydraulic fracturing activities mainly occurred in a core area of four counties, including Dunn, McKenzie, Mountrail, and Williams. The annual total water used for hydraulic fracking in western North Dakota increased from 302 ac-ft in 2007 to 21,605 ac-ft in 2014, by more than 70 times in 8 years. The four-county core area accounted for about 90% of total hydraulic fracturing water use in western North Dakota. Compared to the total water uses of all types, hydraulic fracturing water use in the four-county core area accounted for 0.7% in 2007 and 43.1% in 2014. Statewide, this percentage increased from 0.1% to 6.1% in the same time period. As horizontal drilling and hydraulic fracturing technologies matured for unconventional oil development at Bakken, the total depth and the total length of laterals per well seemed to reach an optimal value in the last four years (2011-2014). However, the number of fracturing stages and the volume of fracking water used per completion are still on the rise. The average water use per well increased from about 1.7 ac-ft in 2007 to 11.4 ac-ft in 2014. Correspondingly, the water intensity (volume of fracking water used per foot of laterals) increased from 67 gallon/ft in 2007 to about 372 gallon/ft 2014. The results helped us better understand the environmental impacts of hydraulic fracturing at Bakken and better manage the water resources in the region.

  11. Method development for determining the hydraulic conductivity of fractured porous media

    SciTech Connect

    Dixon, Kenneth L.

    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

  12. Genome-Centric Analysis of Microbial Populations Enriched by Hydraulic Fracture Fluid Additives in a Coal Bed Methane Production Well.

    PubMed

    Robbins, Steven J; Evans, Paul N; Parks, Donovan H; Golding, Suzanne D; Tyson, Gene W

    2016-01-01

    Coal bed methane (CBM) is generated primarily through the microbial degradation of coal. Despite a limited understanding of the microorganisms responsible for this process, there is significant interest in developing methods to stimulate additional methane production from CBM wells. Physical techniques including hydraulic fracture stimulation are commonly applied to CBM wells, however the effects of specific additives contained in hydraulic fracture fluids on native CBM microbial communities are poorly understood. Here, metagenomic sequencing was applied to the formation waters of a hydraulically fractured and several non-fractured CBM production wells to determine the effect of this stimulation technique on the in-situ microbial community. The hydraulically fractured well was dominated by two microbial populations belonging to the class Phycisphaerae (within phylum Planctomycetes) and candidate phylum Aminicenantes. Populations from these phyla were absent or present at extremely low abundance in non-fractured CBM wells. Detailed metabolic reconstruction of near-complete genomes from these populations showed that their high relative abundance in the hydraulically fractured CBM well could be explained by the introduction of additional carbon sources, electron acceptors, and biocides contained in the hydraulic fracture fluid.

  13. Genome-Centric Analysis of Microbial Populations Enriched by Hydraulic Fracture Fluid Additives in a Coal Bed Methane Production Well

    PubMed Central

    Robbins, Steven J.; Evans, Paul N.; Parks, Donovan H.; Golding, Suzanne D.; Tyson, Gene W.

    2016-01-01

    Coal bed methane (CBM) is generated primarily through the microbial degradation of coal. Despite a limited understanding of the microorganisms responsible for this process, there is significant interest in developing methods to stimulate additional methane production from CBM wells. Physical techniques including hydraulic fracture stimulation are commonly applied to CBM wells, however the effects of specific additives contained in hydraulic fracture fluids on native CBM microbial communities are poorly understood. Here, metagenomic sequencing was applied to the formation waters of a hydraulically fractured and several non-fractured CBM production wells to determine the effect of this stimulation technique on the in-situ microbial community. The hydraulically fractured well was dominated by two microbial populations belonging to the class Phycisphaerae (within phylum Planctomycetes) and candidate phylum Aminicenantes. Populations from these phyla were absent or present at extremely low abundance in non-fractured CBM wells. Detailed metabolic reconstruction of near-complete genomes from these populations showed that their high relative abundance in the hydraulically fractured CBM well could be explained by the introduction of additional carbon sources, electron acceptors, and biocides contained in the hydraulic fracture fluid. PMID:27375557

  14. 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)…

  15. 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.

  16. Elastic and Viscoelastic Modeling of Stresses Induced by Hydraulic Fracturing in Shale Gas Reservoir

    NASA Astrophysics Data System (ADS)

    Trzeciak, Maciej; Sone, Hiroki; Dabrowski, Marcin; Jarosinski, Marek

    2017-04-01

    Hydraulic fracturing is one of the most important engineering tasks in the development of an unconventional gas or oil play. Further exploitation of the reservoir is strongly influenced by the effectiveness of this process. Knowledge about the in situ stress state, and its changes is critical for successful fracturing of a reservoir. Hydraulic fracturing is usually carried out in several stages. The previous stages influence the later ones, because the induced and reactivated fractures, and the corresponding strain tend to increase the minimum horizontal stress (Shmin). This phenomena may lead to changes in the stress regime. The stress state, and fracture network changes result also in consecutive scattering of the microseismic events related to each of the stages. The goal of the present work was to investigate what happens to the stress state after each of the hydraulic fracturing stages, and how it may affect the success of whole operation. Our investigation was divided in two major parts: first we characterized the rheological behavior of the shale rocks from prospective reservoir in northern Poland, and later we incorporated the constitutive models obtained in the laboratory into numerical models of the reservoir. Laboratory testing consisted of fourteen 72-hours-long triaxial creep tests, with ultrasonic acquisition (P, S1 and S2 waves) on cylindrical rock samples from different depths of one borehole. This procedure allowed us to construct a reliable vertical profile of rheological parameters. We did not only focus on the prospective intervals, but we also collected data for the interbedded marl or limestone layers. Numerical modeling was performed with different rheological settings: we started with a simple one layer isotropic elastic material, and then we increased the complexity in steps. Finally we arrived at layered anisotropic viscoelastic material with several fracturing stages which were superimposed on ea