Download or read book Micro mechanical Aspects of Hydraulic Fracture Propagation and Proppant Flow and Transport for Stimulation of Enhanced Geothermal Systems written by Ingrid Tomac and published by . This book was released on 2014 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Discrete Fracture Network Modeling of Hydraulic Stimulation written by Mark W. McClure and published by Springer Science & Business Media. This book was released on 2013-06-15 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: Discrete Fracture Network Modeling of Hydraulic Stimulation describes the development and testing of a model that couples fluid-flow, deformation, friction weakening, and permeability evolution in large, complex two-dimensional discrete fracture networks. The model can be used to explore the behavior of hydraulic stimulation in settings where matrix permeability is low and preexisting fractures play an important role, such as Enhanced Geothermal Systems and gas shale. Used also to describe pure shear stimulation, mixed-mechanism stimulation, or pure opening-mode stimulation. A variety of novel techniques to ensure efficiency and realistic model behavior are implemented, and tested. The simulation methodology can also be used as an efficient method for directly solving quasistatic fracture contact problems. Results show how stresses induced by fracture deformation during stimulation directly impact the mechanism of propagation and the resulting fracture network.

Download or read book Hydraulic fracturing and geothermal energy written by S. Nemat-Nassar and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 519 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydraulic fracturing has been and continues to be a major techno logical tool in oil and gas recovery, nuclear and other waste disposal, mining and particularly in-situ coal gasification, and, more recently, in geothermal heat recovery, particularly extracting heat from hot dry rock masses. The understanding of the fracture process under the ac tion of pressurized fluid at various temperatures is of fundamental scientific importance, which requires an adequate description of thermomechanical properties of subsurface rock, fluid-solid interaction effects, as well as degradation of the host rock due to temperature gradients introduced by heat extraction. Considerable progress has been made over the past several years in laboratory experiments, analytical and numerical modeling, and in-situ field studies in various aspects of hydraulic fracturing and geothermal energy extraction, by researchers in the United States and Japan and also elsewhere. However, the results have been scattered throughout the literature. Therefore, the time seemed ripe for bringing together selected researchers from the two countries, as well as observers from other countries, in order to survey the state of the art, exchange scientific information, and establish closer collaboration for further, better coordinated scientific effort in this important area of research and exploration.

Download or read book Experimental Investigation of Proppant Flow and Transport in Intersected Hydraulic Fractures written by Wenpei Ma and published by . This book was released on 2020 with total page 121 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study investigates proppant flow and transport in intersecting fractures at angles typical for intersections of pre-existing and new hydraulic fractures. Proppant is small granular material, which is placed into hydraulic fractures during geothermal and hydrocarbon reservoir stimulation and props the fluid paths open during reservoir exploitation. This study uses plexiglas laboratory slot experiments enhanced with an advanced image analysis for identifying particle trajectories and quantifying slurry velocities. Although proppant flow and transport has been broadly studied, the effects of intersecting fracture angles have not, especially coupled with fluid viscosities, flow rates, and proppant volumetric concentration effects. This study specifically investigates the role of intermediate fracture angles, which have been identified to occur most frequently when the new hydraulic fractures intercept the existing ones. Results show that proppant flow and transport behavior after the intersection is very sensitive to carrying fluid viscosity and flow rates alteration, while differentiating proppant volumetric concentrations have a limited effect. Fracture intersection angle itself has a clear effect on proppant flow velocities and proppant settlement; furthermore, it enhances the effects from fluid viscosity, fluid flow rates, and proppant volumetric concentrations. This study also studies the proppant agglomeration phenomenon in intersecting fractures. Different shapes of agglomerations are observed and categorized.

Download or read book Numerical Modeling of Nonlinear Problems in Hydraulic Fracturing written by Endrina Rivas and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydraulic fracturing is a stimulation technique in which fluid is injected at high pressure into low-permeability reservoirs to create a fracture network for enhanced production of oil and gas. It is the primary purpose of hydraulic fracturing to enhance well production. The three main mechanisms during hydraulic fracturing for oil and gas production which largely impact the reservoir production are: (1) fracture propagation during initial pad fluid injection, which defines the extent of the fracture; (2) fracture propagation during injection of proppant slurry (fluid mixed with granular material), creating a propped reservoir zone; and (3) shear dilation of natural fractures surrounding the hydraulically fractured zone, creating a broader stimulated zone. The thesis has three objectives that support the simulation of mechanisms that lead to enhanced production of a hydraulically-fractured reservoir. The first objective is to develop a numerical model for the simulation of the mechanical deformation and shear dilation of naturally fractured rock masses. In this work, a two-dimensional model for the simulation of discrete fracture networks (DFN) is developed using the extended finite element method (XFEM), in which the mesh does not conform to the natural fracture network. The model incorporates contact, cohesion, and friction between blocks of rock. Shear dilation is an important mechanism impacting the overall nonlinear response of naturally fractured rock masses and is also included in the model--physics previously not simulated within an XFEM context. Here, shear dilation is modeled through a linear dilation model, capped by a dilation limiting displacement. Highly nonlinear problems involving multiple joint sets are investigated within a quasi-static context. An explicit scheme is used in conjunction with the dynamic relaxation technique to obtain equilibrium solutions in the face of the nonlinear constitutive models from contact, cohesion, friction, and dilation. The numerical implementation is verified and its convergence illustrated using a shear test and a biaxial test. The model is then applied to the practical problem of the stability of a slope of fractured rock. The second objective is to develop a numerical model for the simulation of proppant transport through planar fractures. This work presents the numerical methodology for simulation of proppant transport through a hydraulic fracture using the finite volume method. Proppant models commonly used in the hydraulic fracturing literature solve the linearized advection equation; this work presents solution methods for the nonlinear form of the proppant flux equation. The complexities of solving the nonlinear and heterogeneous hyperbolic advection equation that governs proppant transport are tackled, particularly handling shock waves that are generated due to the nonlinear flux function and the spatially-varying width and pressure gradient along the fracture. A critical time step is derived for the proppant transport problem solved using an explicit solution strategy. Additionally, a predictor-corrector algorithm is developed to constrain the proppant from exceeding the physically admissible range. The model can capture the mechanisms of proppant bridging occurring in sections of narrow fracture width, tip screen-out occurring when fractures become saturated with proppant, and flushing of proppant into new fracture segments. The results are verified by comparison with characteristic solutions and the model is used to simulate proppant transport through a KGD fracture. The final objective is to develop a numerical model for the simulation of proppant transport through propagating non-planar fractures. This work presents the first monolithic coupled numerical model for simulating proppant transport through a propagating hydraulic fracture. A fracture is propagated through a two-dimensional domain, driven by the flow of a proppant-laden slurry. Modeling of the slurry flow includes the effects of proppant bridging and the subsequent flow of fracturing fluid through the packed proppant pack. This allows for the simulation of a tip screen-out, a phenomenon in which there is a high degree of physical interaction between the rock deformation, fluid flow, and proppant transport. Tip screen-out also leads to shock wave formation in the solution. Numerical implementation of the model is verified and the model is then used to simulate a tip screen-out in both planar and non-planar fractures. An analysis of the fracture aperture, fluid pressure, and proppant concentration profiles throughout the simulation is performed for three different coupling schemes: monolithic, sequential, and loose coupling. It is demonstrated that even with time step refinement, the loosely-coupled scheme fails to converge to the same results as the monolithic and sequential schemes. The monolithic and sequential algorithms yield the same solution up to the onset of a tip screen-out, after which the sequential scheme fails to converge. The monolithic scheme is shown to be more efficient than the sequential algorithm (requiring fewer iterations) and has comparable computational cost to the loose coupling algorithm. Thus, the monolithic scheme is shown to be optimal in terms of computational efficiency, robustness, and accuracy. In addition to this finding, a robust and more efficient algorithm for injection-rate controlled hydraulic fracturing simulation based on global mass conservation is presented in the thesis.

Download or read book Designing Enhanced Geothermal and Hydraulic Fracturing Systems Based on Multiple Stages and Proppant written by Sogo Shiozawa and published by . This book was released on 2015 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report consists of two chapters. In the first chapter, designs of Enhanced Geothermal Systems (EGS) with horizontal wells, multiple stages, and proppant are discussed. In EGS, hydraulic stimulation is used to improve well productivity. EGS is typically performed in a nearly vertical well, in one stage, with no proppant. Horizontal wells, multiple stages, and proppant are not used because they are considered not necessary and/or technically infeasible. We found that an EGS design with multiple stages and proppant could give dramatically improved economic performance relative to current designs. We reviewed the literature in order to assess the technical viability of our proposed design. The proposed design would increase cost but deliver substantial improvements in flow rate (and revenue) per well. The second chapter describes a simulation study of proppant transport with Newtonian fluid in a fully three-dimensional hydraulic fracturing simulator, CFRAC. This model has capability to handle proppant settling due to gravity, proppant migration away from the fracture walls, and fracture closure. In the model, the conservation equations of fluid and proppant are sequentially solved in a first-order finite difference scheme. A special algorithm is applied to handle proppant packing due to fracture closure. Our simulation results show good agreement with results from other recently published proppant modeling studies. Sensitivity analysis was performed in order to investigate the effect fluid viscosity, proppant density, and proppant size. Finally, simulations of the tip-screen out (TSO) were performed.

Download or read book Numerical study of the stimulation related thermo hydro mechanical processes in tight gas and deep geothermal reservoirs written by Wentao Feng and published by Cuvillier Verlag. This book was released on 2020-03-05 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydraulic fracturing in combination with horizontal well is playing a key role in the efficient development of unconventional gas/oil reservoirs and deep geothermal resources. However, the integral operation, especially from the perspective of THM (Thermal-Hydraulic-Mechanic) interactions have not been studied systematically. In this thesis, targeted improvements were achieved through developing a series of mathematical/physical models, and their implementation into the existing numerical tools (FLAC3Dplus and TOUGH2MP-FLAC3D), including: (a) a new thermal module for FLAC3Dplus based entirely on the finite volume method (FVM), which is especially developed for the fracturing process and can also achieve the modeling of gel breaking; (b) a rock damage module of TOUGH2MP-FLAC3D, which also considers the impacts of rock damaging process on evolution of permeability; (c) an in-depth improved FLAC3Dplus simulator that obtains the ability to simulate a 3D fracture propagation with arbitrary orientation. After the corresponding verifications, the improved tools were applied in different case studies to reveal: a) influences of the fluid’s viscosity on the fracturing results in tight sandstone reservoirs; b) the induced seismicity during the fracturing operation and the reactivation of the natural faults; and c) the fracture propagation with arbitrary orientation.

Download or read book New numerical approaches to model hydraulic fracturing in tight reservoirs with consideration of hydro mechanical coupling effects written by Lei Zhou and published by Cuvillier Verlag. This book was released on 2014-03-20 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, two new numerical approaches for hydraulic fracturing in tight reservoir were developed. A more physical-based numerical 3D-model was developed for simulating the whole hydraulic fracturing process including fracture propagation, closure and contact as well as proppant transport and settling. In this approach rock formation, pore and fracture systems were assembled together, in which hydro-mechanical coupling effect, proppant transport and settling as well as their influences on fracture closure and contact were fully considered. A combined FDM and FVM schema was used to solve the problem. Three applications by using the new approach were presented. The results illustrated the whole hydraulic fracturing process well and seemed to be logical, which confirmed the ability of the developed approach to model the in-situ hydraulic fracturing operation from injection start till fully closure. In order to investigate the orientation problem of hydraulic fracturing in tight reservoir, a new approach for simulating arbitrary fracture propagation and orientation in 2D was developed. It was solved by a hybrid schema of XFEM and FVM. Three numerical studies were illustrated, which proved the ability of the developed approach to solve the orientation problem in field cases.

Download or read book Discrete Fracture Network Modeling of Hydraulic Stimulation written by Mark McClure and published by Springer. This book was released on 2013-06-19 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: Discrete Fracture Network Modeling of Hydraulic Stimulation describes the development and testing of a model that couples fluid-flow, deformation, friction weakening, and permeability evolution in large, complex two-dimensional discrete fracture networks. The model can be used to explore the behavior of hydraulic stimulation in settings where matrix permeability is low and preexisting fractures play an important role, such as Enhanced Geothermal Systems and gas shale. Used also to describe pure shear stimulation, mixed-mechanism stimulation, or pure opening-mode stimulation. A variety of novel techniques to ensure efficiency and realistic model behavior are implemented, and tested. The simulation methodology can also be used as an efficient method for directly solving quasistatic fracture contact problems. Results show how stresses induced by fracture deformation during stimulation directly impact the mechanism of propagation and the resulting fracture network.

Download or read book Energy Research Abstracts written by and published by . This book was released on 1985 with total page 780 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fully Coupled Geomechanics and Discrete Flow Network Modeling of Hydraulic Fracturing for Geothermal Applications written by and published by . This book was released on 2011 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Mechanics of Hydraulic Fracturing written by Xin-rong Zhang and published by John Wiley & Sons. This book was released on 2023-01-05 with total page 291 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Contemporary Developments in Hydraulic Fracturing written by Kenneth Imo-Imo Israel Eshiet and published by BoD – Books on Demand. This book was released on 2024-07-31 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fracture Propagation and Permeability Change Under Poro thermoelastic Loads Silica Reactivity in Enhanced Geothermal Systems written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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. Therefore, knowledge of the conditions leading to formation of fractures and fracture networks is of paramount importance. Furthermore, in the absence of natural fractures or adequate connectivity, artificial fractures are created in the reservoir using hydraulic fracturing. 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 developed advanced poro-thermo-chemo-mechanical fracture models for rock fracture research in support of EGS design. The fracture propagation models are based on a regular displacement discontinuity formulation. The fracture propagation studies include modeling interaction of induced fractures. In addition to the fracture propagation studies, two-dimensional solution algorithms have been developed and used to estimate the impact of pro-thermo-chemical processes on fracture permeability and reservoir pressure. Fracture permeability variation is studied using a coupled thermo-chemical model with quartz reaction kinetics. The model is applied to study quartz precipitation/dissolution, as well as the variation in fracture aperture and pressure. Also, a three-dimensional model of injection/extraction has been developed to consider the impact poro- and thermoelastic stresses on fracture slip and injection pressure. These investigations shed light on the processes involved in the observed phenomenon of injection pressure variation (e.g., in Coso), and allow the assessment of the potential of thermal and chemical stimulation strategies.

Download or read book Hydraulic Proppant Fracturing and Gravel Packing written by D. Mader and published by Elsevier. This book was released on 1989-03-01 with total page 1277 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many aspects of hydraulic proppant fracturing have changed since its innovation in 1947. The main significance of this book is its combination of technical and economical aspects to provide an integrated overview of the various applications of proppants in hydraulic fracturing, and gravel in sand control. The monitoring of fractures and gravel packs by well-logging and seismic techniques is also included.The book's extensive coverage of the subject should be of special interest to reservoir geologists and engineers, production engineers and technologists, and well log analysts.

Download or read book Numerical Simulation of Fluid Flow Proppant Transport and Fracture Propagation in Hydraulic Fractures for Unconventional Reservoirs written by Yatin Suri and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Modeling of Hydraulic Fracture Propagation Using Thermo hydro mechanical Analysis with Brittle Damage Model by Finite Element Method written by Kyoung Min and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Better understanding and control of crack growth direction during hydraulic fracturing are essential for enhancing productivity of geothermal and petroleum reservoirs. Structural analysis of fracture propagation and impact on fluid flow is a challenging issue because of the complexity of rock properties and physical aspects of rock failure and fracture growth. Realistic interpretation of the complex interactions between rock deformation, fluid flow, heat transfer, and fracture propagation induced by fluid injection is important for fracture network design. In this work, numerical models are developed to simulate rock failure and hydraulic fracture propagation. The influences of rock deformation, fluid flow, and heat transfer on fracturing processes are studied using a coupled thermo-hydro-mechanical (THM) analysis. The models are used to simulate microscopic and macroscopic fracture behaviors of laboratory-scale uniaxial and triaxial experiments on rock using an elastic/brittle damage model considering a stochastic heterogeneity distribution. The constitutive modeling by the energy release rate-based damage evolution allows characterizing brittle rock failure and strength degradation. This approach is then used to simulate the sequential process of heterogeneous rock failures from the initiation of microcracks to the growth of macrocracks. The hydraulic fracturing path, especially for fractures emanating from inclined wellbores and closed natural fractures, often involves mixed mode fracture propagation. Especially, when the fracture is inclined in a 3D stress field, the propagation cannot be modeled using 2D fracture models. Hence, 2D/3D mixed-modes fracture growth from an initially embedded circular crack is studied using the damage mechanics approach implemented in a finite element method. As a practical problem, hydraulic fracturing stimulation often involves fluid pressure change caused by injected fracturing fluid, fluid leakoff, and fracture propagation with brittle rock behavior and stress heterogeneities. In this dissertation, hydraulic fracture propagation is simulated using a coupled fluid flow/diffusion and rock deformation analysis. Later THM analysis is also carried out. The hydraulic forces in extended fractures are solved using a lubrication equation. Using a new moving-boundary element partition methodology (EPM), fracture propagation through heterogeneous media is predicted simply and efficiently. The method allows coupling fluid flow and rock deformation, and fracture propagation using the lubrication equation to solve for the fluid pressure through newly propagating crack paths. Using the proposed model, the 2D/3D hydraulic fracturing simulations are performed to investigate the role of material and rock heterogeneity. Furthermore, in geothermal and petroleum reservoir design, engineers can take advantage of thermal fracturing that occurs when heat transfers between injected flow and the rock matrix to create reservoir permeability. These thermal stresses are calculated using coupled THM analysis and their influence on crack propagation during reservoir stimulation are investigated using damage mechanics and thermal loading algorithms for newly fractured surfaces. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/150961