Experimental Studies In Hydraulic Fracture Growth
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Experimental Studies In Hydraulic Fracture Growth
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Author : Murtadha Jawad Al Tammar
language : en
Publisher:
Release Date : 2018
Experimental Studies In Hydraulic Fracture Growth written by Murtadha Jawad Al Tammar and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
Novel experimental capabilities to study hydraulic fracturing in the laboratory are developed and utilized in this research. Fracturing experiments are conducted using two-dimensional (2-D) test specimens that are made from synthetic, porous materials with well-characterized properties. Fracture growth during the experiments is captured with clear, high resolution images and subsequent image processing using Digital Image Correlation (DIC) analyses. First, we investigated the problem of a hydraulic fracture induced in a soft layer bounded by harder layers. The experiments reveal a clear tendency for induced fractures to avoid harder bounding layers. This is seen as fracture deflection or kinking away from the harder layers, fracture curving between the harder bounding layers, and fracture tilt from the maximum far-field stress direction. In addition, when a fracture is induced in a relatively thin layer, the fracture avoids the harder bounding layers by initiating and propagating parallel to the bounding interfaces. Fracture propagation parallel to the bounding layers is also observed in relatively wide layers when the far-field stress is isotropic or very low. Complex fracture trajectories are induced in layered specimens when the far-field differential stress is low or intermediate. In a second set of experiments, we used homogeneous specimens with multiple fluid injection ports. It is clearly shown that injection-induced stresses can appreciably affect hydraulic fracture trajectories and fracturing pressures. We show that induced hydraulic fractures, under our laboratory conditions, are attracted to regions of high pore pressure. Induced fractures tend to propagate towards neighboring high pore pressure injection ports. The recorded breakdown pressure in the fracturing experiments decreases significantly as the number of neighboring injectors increases. The influence of an adjacent fluid injection source on the hydraulic fracture trajectory can be minimized or suppressed when the applied far-field differential stress is relatively high. Preferential fracture growth due to changes in pore pressure in field applications as compared to our laboratory observations is also discussed. In a third set of experiments, we show that the breakdown pressure of test specimens can be reduced markedly with low injection rates, cyclic borehole pressurization, and/or constant pressure injection. This is largely related to the extent of pressurized region around the borehole caused by fluid leakoff in dry specimens and possible specimen weakening by fluid contact. The breakdown pressure can also be reduced by notching the specimen borehole when the injection fluid is allowed to flow and leak off along the borehole notch. In a fourth set of experiments, we compared fracture growth induced by a viscous liquid and a gas which are glycerin and nitrogen, respectively. The experiments show that fractures propagate through test specimens in a gradual manner when induced by glycerin at various injection rates. By contrast, nitrogen injection induces fractures that grow much more rapidly, which we attribute to its compressible nature and ultralow viscosity. The breakdown pressure is also shown to be markedly lower for nitrogen fractures compared to glycerin fractures. Moreover, an experimental evidence of fluid lag when fractures are induced with viscous fluids is demonstrated. Lastly, experiments were conducted to examine the behavior of an induced hydraulic fracture as it approaches a cemented natural fracture. We show a tendency for the induced hydraulic fracture to cross thick natural fractures filled with softer materials than the host rock and to be diverted by thick natural fractures with harder filling materials. The induced hydraulic fracture also tends to cross hard natural fractures when the natural fractures are relatively thin. In addition, the induced hydraulic fracture from the injection port is shown to be diverted by a thin, hard natural fracture that is placed relatively close to the injection port but crosses the same natural fracture when placed farther away from the injection port. These observations, and numerous others, documented in this dissertation provide fundamental insights on various aspects of hydraulic fracture propagation. Our extensive set of laboratory observations are also very useful in validating numerical hydraulic fracturing simulators due to the small-scale, 2-D nature, and characterized properties of the test specimens used in the experiments
Mechanics Of Hydraulic Fracturing
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Author : Xin-rong Zhang
language : en
Publisher: John Wiley & Sons
Release Date : 2023-01-05
Mechanics Of Hydraulic Fracturing written by Xin-rong Zhang and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023-01-05 with Technology & Engineering categories.
Mechanics of Hydraulic Fracturing Comprehensive single-volume reference work providing an overview of experimental results and predictive methods for hydraulic fracture growth in rocks Mechanics of Hydraulic Fracturing: Experiment, Model, and Monitoring provides a summary of the research in mechanics of hydraulic fractures during the past two decades, plus new research trends to look for in the future. The book covers the contributions from theory, modeling, and experimentation, including the application of models to reservoir stimulation, mining preconditioning, and the formation of geological structures. The four expert editors emphasize the variety of diverse methods and tools in hydraulic fracturing and help the reader understand hydraulic fracture mechanics in complex geological situations. To aid in reader comprehension, practical examples of new approaches and methods are presented throughout the book. Key topics covered in the book include: Prediction of fracture shapes, sizes, and distributions in sedimentary basins, plus their importance in petroleum industry Real-time monitoring methods, such as micro-seismicity and trace tracking How to uncover geometries of fractures like dikes and veins Fracture growth of individual foundations and its applications Researchers and professionals working in the field of fluid-driven fracture growth will find immense value in this comprehensive reference on hydraulic fracturing mechanics.
Hydraulic Fracture Propagation In Layered Rock
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Author :
language : en
Publisher:
Release Date : 1981
Hydraulic Fracture Propagation In Layered Rock written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1981 with categories.
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.
Hydraulic Fracturing Optimization
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Author : Andreas Michael
language : en
Publisher:
Release Date : 2016
Hydraulic Fracturing Optimization written by Andreas Michael and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
Hydraulic fracturing is a reservoir stimulation technique used in the petroleum industry since 1947. High pressure fluid composed mainly of water generates cracks near the wellbore improving the surrounding permeability and enhancing the flow of oil and gas to the surface. Advances in hydraulic fracturing coupled with developments in horizontal drilling, have unlocked vast quantities of unconventional resources, previously believed impossible to be produced. Fracture creation induces perturbations in the nearby in-situ stress regime suppressing the initiation and propagation of other fractures. Neighboring fractures are affected by this stress shadow effect, causing them to grow dissimilarly and they receive unequal portions of the injected fluid. Numerical simulation models have shown that non-uniform perforation cluster distributions with interior fractures closer to the exterior ones can balance out these stress shadow effects, promoting more homogeneous multiple fracture growth compared to uniform perforation cluster distributions. In this work, laboratory-scale tests on three perforation configurations are performed on transparent specimens using distinctly colored fracturing fluids such that fracture growth can be observed. A normal faulting stress regime is replicated with the introduction of an overburden load in a confined space. The results have shown that uniform perforation spacing configurations yields higher degree of fracture growth homogeneity, as maximum spacing minimizes stress shadow effects, compared to moving the middle perforation closer to the toe, or heel of the horizontal well. The experiments also showed a proclivity to form one dominant fracture. Time delay, neglected in most theoretical modelling studies, between fracture initiations is found to be a key parameter and is believed to be one of the major factors promoting this dominant fracture tendency along with wellbore pressure gradients. Moreover, in several cases, the injected bypassed perforation(s) to generate fracture(s) downstream. Finally, the compressibility of the fracturing fluid triggered somewhat unexpected transient pressure behavior. The understanding of the stress shadow effects and what influences them could lead to optimization of hydraulic fracturing treatment design in terms of productivity and cost. Therefore, achieving more homogeneous multiple fracture growth patterns can be pivotal on the economic feasibility of several stimulation treatments.
Hydraulic Fracture Propagation Through Geological Discontinuities
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Author : Ella María Llanos Rodríguez
language : en
Publisher:
Release Date : 2015
Hydraulic Fracture Propagation Through Geological Discontinuities written by Ella María Llanos Rodríguez and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with Hydraulic fracturing categories.
Hydraulic fracturing is a stimulation technique widely used to enhance hydrocarbon production and geothermal energy extraction. Other applications include waste disposal and cave inducement and preconditioning of ore for mining. Rocks are naturally fractured and therefore the little-understood problem of hydraulic fracture growth through these pre-existing discontinuities is a key area of research. Mathematical criteria for predicting whether an induced fracture will cross a discontinuity have been published by several authors. Some used parameters that are difficult to quantify, neglected the stress induced by the hydraulic fracture itself and ignored fluid viscosity effects on crossing behaviour. Others ignored the presence of fluid in the hydraulic fracture, the possibility of fracture re-initiation after slippage and the effect of surface features on crossing. Numerical studies have shown that viscosity-dominated hydraulic fractures would induce slip on the discontinuity more easily than toughness-dominated hydraulic fractures. This implies that crossing should be more difficult for viscosity-dominated hydraulic fractures. To investigate the interaction between hydraulic and natural fractures, laboratory experiments are combined with numerical and analytical work in this thesis to extend two previously published criteria. This thesis shows the effect of viscosity on the crossing interaction is complex and cannot be predicted based only on whether slip occurs on the discontinuity before the hydraulic fracture intersects it. The laboratory work can also be applied to improved understanding of the effect of the stress field on crossing as it relates to hydraulic fracture height growth. Prediction of the effect of weak bedding planes on height growth has recently gained importance as the risk of vertical growth of fractures into aquifers has emerged as a concern in shale gas and coal seam gas operations. The findings herein can be applied to this problem if the frictional interfaces are considered to represent weak bedding planes. Complete treatment of the height growth problem requires considering fracture growth through elastic layers with contrasts in physical properties. The experiments show hydraulic fractures may grow to become elliptical because they extend more quickly and further in the direction of maximum stress or in the direction with fewer discontinuities. The preparation of the samples underlined the effect of local imperfections on discontinuities. Small areas of higher or lower contact stress can aid or inhibit fracture initiation. Rock plates must be smooth and flat in order to control this parameter and obtain valid experimental comparisons for contact stress and the other parameters controlling crossing. Numerical and analytical results are presented as a mathematical expression with universal curves for the locations of slip starting points, providing an important aid for designing industrial hydraulic fractures. One difference between the approach used here and that used by others is their use of the fracture-tip singular stress solution, meaning they do not consider the effect of the non-singular stresses existing around a pressurised fracture. This thesis therefore improves their work. Experimental and theoretical outcomes herein suggest that hydraulic fracture growth through an orthogonal discontinuity does not depend primarily on the interface friction coefficient. This finding contradicts several models.
Examining The Effect Of Cemented Natural Fractures On Hydraulic Fracture Propagation In Hydrostone Block Experiments
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Author : Benjamin Lee Bahorich
language : en
Publisher:
Release Date : 2012
Examining The Effect Of Cemented Natural Fractures On Hydraulic Fracture Propagation In Hydrostone Block Experiments written by Benjamin Lee Bahorich and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
Micro seismic data and coring studies suggest that hydraulic fractures interact heavily with natural fractures creating complex fracture networks in naturally fractured reservoirs such as the Barnett shale, the Eagle Ford shale, and the Marcellus shale. However, since direct observations of subsurface hydraulic fracture geometries are incomplete or nonexistent, we look to properly scaled experimental research and computer modeling based on realistic assumptions to help us understand fracture intersection geometries. Most experimental analysis of this problem has focused on natural fractures with frictional interfaces. However, core observations from the Barnett and other shale plays suggest that natural fractures are largely cemented. To examine hydraulic fracture interactions with cemented natural fractures, we performed 9 hydraulic fracturing experiments in gypsum cement blocks that contained embedded planar glass, sandstone, and plaster discontinuities which acted as proxies for cemented natural fractures. There were three main fracture intersection geometries observed in our experimental program. 1) A hydraulic fracture is diverted into a different propagation path(s) along a natural fracture. 2) A taller hydraulic fracture bypasses a shorter natural fracture by propagating around it via height growth while also separating the weakly bonded interface between the natural fracture and the host rock. 3) A hydraulic fracture bypasses a natural fracture and also diverts down it to form separate fractures. The three main factors that seemed to have the strongest influence on fracture intersection geometry were the angle of intersection, the ratio of hydraulic fracture height to natural fracture height, and the differential stress. Our results show that bypass, separation of weakly bonded interfaces, diversion, and mixed mode propagation are likely in hydraulic fracture intersections with cemented natural fractures. The impact of this finding is that we need fully 3D computer models capable of accounting for bypass and mixed mode I-III fracture propagation in order to realistically simulate subsurface hydraulic fracture geometries.
Geomechanics And Hydraulic Fracturing For Shale Reservoirs
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Author : Yu Wang
language : en
Publisher: Scientific Research Publishing, Inc. USA
Release Date : 2020-07-01
Geomechanics And Hydraulic Fracturing For Shale Reservoirs written by Yu Wang and has been published by Scientific Research Publishing, Inc. USA this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-07-01 with Art categories.
This book is intended as a reference book for advanced graduate students and research engineers in shale gas development or rock mechanical engineering. Globally, there is widespread interest in exploiting shale gas resources to meet rising energy demands, maintain energy security and stability in supply and reduce dependence on higher carbon sources of energy, namely coal and oil. However, extracting shale gas is a resource intensive process and is dependent on the geological and geomechanical characteristics of the source rocks, making the development of certain formations uneconomic using current technologies. Therefore, evaluation of the physical and mechanical properties of shale, together with technological advancements, is critical in verifying the economic viability of such formation. Accurate geomechanical information about the rock and its variation through the shale is important since stresses along the wellbore can control fracture initiation and frac development. In addition, hydraulic fracturing has been widely employed to enhance the production of oil and gas from underground reservoirs. Hydraulic fracturing is a complex operation in which the fluid is pumped at a high pressure into a selected section of the wellbore. The interaction between the hydraulic fractures and natural fractures is the key to fracturing effectiveness prediction and high gas development. The development and growth of a hydraulic fracture through the natural fracture systems of shale is probably more complex than can be described here, but may be somewhat predictable if the fracture system and the development of stresses can be explained. As a result, comprehensive shale geomechanical experiments, physical modeling experiment and numerical investigations should be conducted to reveal the fracturing mechanical behaviors of shale.
An Experimental Study Of Hydraulic Fracturing
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Author : Gary William Jaworski
language : en
Publisher:
Release Date : 1979
An Experimental Study Of Hydraulic Fracturing written by Gary William Jaworski and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1979 with Earth dams categories.
Experimental Investigation Of Geomechanical Aspects Of Hydraulic Fracturing Unconventional Formations
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Author : Emad Abbad Alabbad
language : en
Publisher:
Release Date : 2014
Experimental Investigation Of Geomechanical Aspects Of Hydraulic Fracturing Unconventional Formations written by Emad Abbad Alabbad and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
Understanding the mechanisms that govern hydraulic fracturing applications in unconventional formations, such as gas-bearing shales, is of increasing interest to the petroleum upstream industry. Among such mechanisms, the geomechanical interactions between hydraulic fractures and pre-existing fractures on one hand, and simultaneous multiple hydraulic fractures on the other hand are seen of high importance. Although the petroleum engineering and related literature contains a number of studies that discusses such topics of hydraulic fracture interactions, there still remain some aspects that require answers, validations, or further supporting data. Particularly, experimental evidence is fairly scarce and keenly needed to solidify the understanding of such complex applications. In this work, the investigation methodology uses a series of hydraulic fracturing laboratory tests performed on synthetic rocks made of gypsum-based cements such as hydrostone and plaster in various experimental set ups. Those laboratory tests aim to closely investigate hydraulic fracture intersection with pre-existing fractures by assessing some factors that govern its outcomes. Specifically, the roles of the pre-existing fracture cementation, aperture, and relative height on the intersection mode are examined. The results show dominant effect of the cement-fill type relative to the host-rock matrix in determining whether hydraulic fracture crossing the pre-existing interface may occur. Similarly, hydraulic fracture height relative to the height of the pre-existing fracture may dictate the intersection results. However, the intersection mode seems to be insensitive of the pre-existing fracture aperture. Moreover, simultaneous multi-fracture propagation is examined and found to be impacted by the interference of the stresses induced from each fracturing source on neighboring fracturing sources. Such stress interference increases as the number of the propagating hydraulic fractures increase. While hydraulic fractures initiating from fracturing sources located in the middle of the fracturing stage seem to have inhibited propagation, outer hydraulic fractures may continue propagating with outward curvatures. Overall, the experimental results and analyses offer more insights for understanding hydraulic fracture complexity in unconventional formations.
Hydraulic Fracturing And Rock Mechanics
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Author : Yu Zhao
language : en
Publisher: Springer Nature
Release Date : 2023-06-21
Hydraulic Fracturing And Rock Mechanics written by Yu Zhao and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023-06-21 with Science categories.
This open access book is the first to consider the effect of non-uniform fluid pressure in hydraulic fractures. The book covers the key topics in the process of hydraulic fracture nucleation, growth, interaction and fracture network formation. Laboratory experiments and theoretical modeling are combined to elucidate the formation mechanism of complex fracture networks. This book is suitable for master’s/Ph.D. students, scientists and engineers majoring in rock mechanics and petroleum engineering who need to use a more reliable model to predict fracture behavior.