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Numerical Modeling Of Fracture Permeability Change In Naturally Fractured Reservoirs Using A Fully Coupled Displacement Discontinuity Method
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Book Synopsis Numerical Modeling of Fracture Permeability Change in Naturally Fractured Reservoirs Using a Fully Coupled Displacement Discontinuity Method by : Qingfeng Tao
Download or read book Numerical Modeling of Fracture Permeability Change in Naturally Fractured Reservoirs Using a Fully Coupled Displacement Discontinuity Method written by Qingfeng Tao and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fractures are the main flow channels in naturally fractured reservoirs. Therefore the fracture permeability is a critical parameter to production optimization and reservoir management. Fluid pressure reduction caused by production induces an increase in effective stress in naturally fractured reservoirs. The change of effective stress induces fracture deformation and changes fracture aperture and permeability, which in turn influences the production. Coupled interactions exist in the fractured reservoir: (i) fluid pressure change induces matrix deformation and stress change; (ii) matrix deformation induces fluid volume change and fluid pressure change; (iii) fracture deformation induces the change of pore pressure and stress in the whole field (the influence disappears at infinity); (iv) the change of pore pressure and stress at any point has an influence on the fracture and induces fracture deformation. To model accurately the influence of pressure reduction on the fracture permeability change in naturally fractured reservoirs, all of these coupled processes need to be considered. Therefore, in this dissertation a fully coupled approach is developed to model the influence of production on fracture aperture and permeability by combining a finite difference method to solve the fluid flow in fractures, a fully coupled displacement discontinuity method to build the global relation of fracture deformation, and the Barton-Bandis model of fracture deformation to build the local relation of fracture deformation. The fully coupled approach is applied to simulate the fracture permeability change in naturally fracture reservoir under isotropic in situ stress conditions and high anisotropic in situ stress conditions, respectively. Under isotropic stress conditions, the fracture aperture and permeability decrease with pressure reduction caused by production, and the magnitude of the decrease is dependent on the initial effective in situ stress. Under highly anisotropic stress, the fracture permeability can be enhanced by production because of shear dilation. The enhancement of fracture permeability will benefit to the production of oil and gas.
Book Synopsis Hydraulic Fracture Modeling by : Yu-Shu Wu
Download or read book Hydraulic Fracture Modeling written by Yu-Shu Wu and published by Gulf Professional Publishing. This book was released on 2017-11-30 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydraulic Fracture Modeling delivers all the pertinent technology and solutions in one product to become the go-to source for petroleum and reservoir engineers. Providing tools and approaches, this multi-contributed reference presents current and upcoming developments for modeling rock fracturing including their limitations and problem-solving applications. Fractures are common in oil and gas reservoir formations, and with the ongoing increase in development of unconventional reservoirs, more petroleum engineers today need to know the latest technology surrounding hydraulic fracturing technology such as fracture rock modeling. There is tremendous research in the area but not all located in one place. Covering two types of modeling technologies, various effective fracturing approaches and model applications for fracturing, the book equips today's petroleum engineer with an all-inclusive product to characterize and optimize today's more complex reservoirs. - Offers understanding of the details surrounding fracturing and fracture modeling technology, including theories and quantitative methods - Provides academic and practical perspective from multiple contributors at the forefront of hydraulic fracturing and rock mechanics - Provides today's petroleum engineer with model validation tools backed by real-world case studies
Book Synopsis Numerical Modeling of Complex Hydraulic Fracture Development in Unconventional Reservoirs by : Kan Wu
Download or read book Numerical Modeling of Complex Hydraulic Fracture Development in Unconventional Reservoirs written by Kan Wu and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Successful creations of multiple hydraulic fractures in horizontal wells are critical for economic development of unconventional reservoirs. The recent advances in diagnostic techniques suggest that multi-fracturing stimulation in unconventional reservoirs has often caused complex fracture geometry. The most important factors that might be responsible for the fracture complexity are fracture interaction and the intersection of the hydraulic and natural fracture. The complexity of fracture geometry results in significant uncertainty in fracturing treatment designs and production optimization. Modeling complex fracture propagation can provide a vital link between fracture geometry and stimulation treatments and play a significant role in economically developing unconventional reservoirs. In this research, a novel fracture propagation model was developed to simulate complex hydraulic fracture propagation in unconventional reservoirs. The model coupled rock deformation with fluid flow in the fractures and the horizontal wellbore. A Simplified Three Dimensional Displacement Discontinuity Method (S3D DDM) was proposed to describe rock deformation, calculating fracture opening and shearing as well as fracture interaction. This simplified 3D method is much more accurate than faster pseudo-3D methods for describing multiple fracture propagation but requires significantly less computational effort than fully three-dimensional methods. The mechanical interaction can enhance opening or induce closing of certain crack elements or non-planar propagation. Fluid flow in the fracture and the associated pressure drop were based on the lubrication theory. Fluid flow in the horizontal wellbore was treated as an electrical circuit network to compute the partition of flow rate between multiple fractures and maintain pressure compatibility between the horizontal wellbore and multiple fractures. Iteratively and fully coupled procedures were employed to couple rock deformation and fluid flow by the Newton-Raphson method and the Picard iteration method. The numerical model was applied to understand physical mechanisms of complex fracture geometry and offer insights for operators to design fracturing treatments and optimize the production. Modeling results suggested that non-planar fracture geometry could be generated by an initial fracture with an angle deviating from the direction of the maximum horizontal stress, or by multiple fracture propagation in closed spacing. Stress shadow effects are induced by opening fractures and affect multiple fracture propagation. For closely spaced multiple fractures growing simultaneously, width of the interior fractures are usually significantly restricted, and length of the exterior fractures are much longer than that of the interior fractures. The exterior fractures receive most of fluid and dominate propagation, resulting in immature development of the interior fractures. Natural fractures could further complicate fracture geometry. When a hydraulic fracture encounters a natural fracture and propagates along the pre-existing path of the natural fracture, fracture width on the natural fracture segment will be restricted and injection pressure will increase, as a result of stress shadow effects from hydraulic fracture segments and additional closing stresses from in-situ stress field. When multiple fractures propagate in naturally fracture reservoirs, complex fracture networks could be induced, which are affected by perforation cluster spacing, differential stress and natural fracture patterns. Combination of our numerical model and diagnostic methods (e.g. Microseismicity, DTS and DAS) is an effective approach to accurately characterize the complex fracture geometry. Furthermore, the physics-based complex fracture geometry provided by our model can be imported into reservoir simulation models for production analysis.
Book Synopsis Numerical Simulation in Hydraulic Fracturing: Multiphysics Theory and Applications by : Xinpu Shen
Download or read book Numerical Simulation in Hydraulic Fracturing: Multiphysics Theory and Applications written by Xinpu Shen and published by CRC Press. This book was released on 2017-03-27 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: The expansion of unconventional petroleum resources in the recent decade and the rapid development of computational technology have provided the opportunity to develop and apply 3D numerical modeling technology to simulate the hydraulic fracturing of shale and tight sand formations. This book presents 3D numerical modeling technologies for hydraulic fracturing developed in recent years, and introduces solutions to various 3D geomechanical problems related to hydraulic fracturing. In the solution processes of the case studies included in the book, fully coupled multi-physics modeling has been adopted, along with innovative computational techniques, such as submodeling. In practice, hydraulic fracturing is an essential project component in shale gas/oil development and tight sand oil, and provides an essential measure in the process of drilling cuttings reinjection (CRI). It is also an essential measure for widened mud weight window (MWW) when drilling through naturally fractured formations; the process of hydraulic plugging is a typical application of hydraulic fracturing. 3D modeling and numerical analysis of hydraulic fracturing is essential for the successful development of tight oil/gas formations: it provides accurate solutions for optimized stage intervals in a multistage fracking job. It also provides optimized well-spacing for the design of zipper-frac wells. Numerical estimation of casing integrity under stimulation injection in the hydraulic fracturing process is one of major concerns in the successful development of unconventional resources. This topic is also investigated numerically in this book. Numerical solutions to several other typical geomechanics problems related to hydraulic fracturing, such as fluid migration caused by fault reactivation and seismic activities, are also presented. This book can be used as a reference textbook to petroleum, geotechnical and geothermal engineers, to senior undergraduate, graduate and postgraduate students, and to geologists, hydrogeologists, geophysicists and applied mathematicians working in this field. This book is also a synthetic compendium of both the fundamentals and some of the most advanced aspects of hydraulic fracturing technology.
Book Synopsis Challenges in Modelling and Simulation of Shale Gas Reservoirs by : Jebraeel Gholinezhad
Download or read book Challenges in Modelling and Simulation of Shale Gas Reservoirs written by Jebraeel Gholinezhad and published by Springer. This book was released on 2017-12-27 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book addresses the problems involved in the modelling and simulation of shale gas reservoirs, and details recent advances in the field. It discusses various modelling and simulation challenges, such as the complexity of fracture networks, adsorption phenomena, non-Darcy flow, and natural fracture networks, presenting the latest findings in these areas. It also discusses the difficulties of developing shale gas models, and compares analytical modelling and numerical simulations of shale gas reservoirs with those of conventional reservoirs. Offering a comprehensive review of the state-of-the-art in developing shale gas models and simulators in the upstream oil industry, it allows readers to gain a better understanding of these reservoirs and encourages more systematic research on efficient exploitation of shale gas plays. It is a valuable resource for researchers interested in the modelling of unconventional reservoirs and graduate students studying reservoir engineering. It is also of interest to practising reservoir and production engineers.
Book Synopsis Thermo-Hydro-Mechanical Behavior of Conductive Fractures Using a Hybrid Finite Difference - Displacement Discontinuity Method by : Mohammadreza Jalali
Download or read book Thermo-Hydro-Mechanical Behavior of Conductive Fractures Using a Hybrid Finite Difference - Displacement Discontinuity Method written by Mohammadreza Jalali and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Large amounts of hydrocarbon reserves are trapped in fractured reservoirs where fluid flux is far more rapid along fractures than through the porous matrix, even though the volume of the pore space may be a hundred times greater than the volume of the fractures. These are considered extremely challenging in terms of accurate recovery prediction because of their complexity and heterogeneity. Conventional reservoir simulators are generally not suited to naturally fractured reservoirs' production history simulation, especially when production processes are associated with large pressure and temperature changes that lead to large redistribution of effective stresses, causing natural fracture aperture alterations. In this case, all the effective processes, i.e. hydraulic, thermal and geomechanical, should be considered simultaneously to explain and evaluate the behavior of stress-sensitive reservoirs over the production period. This is called thermo-hydro-mechanical (THM) coupling. In this study, a fully coupled thermo-hydro-mechanical approach is developed to simulate the physical behavior of fractures in a plane strain thermo-poroelastic medium. A hybrid numerical method, which implements both the finite difference method (FDM) and the displacement discontinuity method (DDM), is established to study the pressure, temperature, deformation and stress variations of fractures and surrounding rocks during production processes. This method is straightforward and can be implemented in conventional reservoir simulators to update fracture conductivity as it uses the same grid block as the reservoir grids and requires only discretization of fractures. The hybrid model is then verified with couple of analytical solutions for the fracture aperture variation under different conditions. This model is implemented for some examples to present the behavior of fracture network as well as its surrounding rock under thermal injection and production. The results of this work clearly show the importance of rate, aspect ratio (i.e. geometry) and the coupling effects among fracture flow rate and aperture changes arising from coupled stress, pressure and temperature changes. The outcomes of this approach can be used to study the behavior of hydraulic injection for induced fracturing and promoting of shearing such as hydraulic fracturing of shale gas or shale oil reservoirs as well as massive waste disposal in the porous carbonate rocks. Furthermore, implementation of this technique should be able to lead to a better understanding of induced seismicity in injection projects of all kinds, whether it is for waste water disposal, or for the extraction of geothermal energy.
Book Synopsis Drilling Geomechanics in Naturally Fractured Reservoirs Near Salt Structures by : Juan Pedro Morales Salazar
Download or read book Drilling Geomechanics in Naturally Fractured Reservoirs Near Salt Structures written by Juan Pedro Morales Salazar and published by Springer Nature. This book was released on with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Numerical Framework for Coupled Flow, Large Deformation, and Large Slip for Fractured and Faulted Reservoirs by : Timothy Myung Joon Yeo
Download or read book A Numerical Framework for Coupled Flow, Large Deformation, and Large Slip for Fractured and Faulted Reservoirs written by Timothy Myung Joon Yeo and published by . This book was released on 2022 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Many applications of the numerical modeling of coupled flow and deformation for subsurface reservoirs are based on the assumption of small deformation. This approximation makes two assumptions: the displacement gradients in the reference configuration are infinitesimal, and the displacement itself is very small compared to the characteristic length of the problem of interest. The small deformation approximation is usually valid in subsurface reservoirs because a typical reservoir rock is stiff and, therefore, exhibits small deformation. However, this assumption may not be valid in some subsurface reservoirs that experience substantial compaction or shear. Some examples demonstrate the substantial subsidence due to a large amount of hydrocarbon production, underground water removal, and softening of the rock due to thermal injections. Accounting for large deformations can be particularly important in fractured or faulted reservoirs. There, fractures can have a significant impact on the fluid flow by acting as flow conduits or flow barriers. Considering that fractures and faults typically have a very small aperture, even small deformation or small tangential slip of the fracture could significantly impact the flow by changing flow directions or fracture permeability. Therefore, a new numerical framework for coupled fluid flow, large deformation, and large slip for fractured and faulted reservoirs is developed by employing the mixed standard Galerkin finite element and two-point flux approximation finite volume methods. The developed framework models the fracture as a large deformation frictional contact using the Node-To-Segment (NTS) contact element with the penalty formulation. The algorithms to dynamically update flow connections around the fracture and their transmissibility are presented for non-matching grids along the fracture due to the tangential slip. The coupled equations are solved in a fully coupled way using the Newton-Raphson method with the active set strategy. In order to model the realistic behavior of the fracture, fracture permeability is updated depending on the fracture states, stress, and deformation. The linear slip-weakening model and gravity are also incorporated in the model. The developed framework is verified with several benchmark problems having analytical solutions, including the single fracture slip problem, the Mandel problem, and the strip footing problem. Afterward, the relative errors of the coupled flow and small deformation model are computed for various model problems with various material properties in order to investigate the applicability of the coupled small deformation model. Finally, the developed framework was applied to model fluid injection into the faulted overburden-reservoir-underburden system in order to model the reactivation of the fault. Even though the stiffness of the system is high and deformation is indeed small, the coupled large deformation model indicates a faster increase in the fault slip area compared to the small deformation model. A separate section of the dissertation presents a framework to solve the small deformation frictional contact problem using the method of augmented Lagrangian with the polynomial pressure projection (PPP) stabilization. This method successfully suppresses spurious oscillations on the normal contact traction and demonstrates the capability to precisely apply the constraints on the contact without introducing additional global degrees of freedom.
Book Synopsis Numerical Modeling of Complex Hydraulic Fracture Propagation in Layered Reservoirs with Auto-optimization by : Jiacheng Wang (Ph. D.)
Download or read book Numerical Modeling of Complex Hydraulic Fracture Propagation in Layered Reservoirs with Auto-optimization written by Jiacheng Wang (Ph. D.) and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydraulic fracturing brings economic unconventional reservoir developments, and multi-cluster completion designs result in complex hydraulic fracture geometries. Therefore, accurate yet efficient modeling of the propagation of multiple non-planar hydraulic fractures is desired to study the mechanisms of hydraulic fracture propagation and optimize field completion designs. In this research, a novel hydraulic fracture model is developed to simulate the propagation of multiple hydraulic fractures with proppant transport in layered and naturally fractured reservoirs. The simplified three-dimensional displacement discontinuity method (S3D DDM) is enhanced to compute the hydraulic fracture deformation and propagation with analytical fracture height growth and vertical width variation. Using a single row of DDM elements, the enhanced S3D DDM hydraulic fracture model computes the fully 3D geometries with a similar computational intensity to a 2D model. Then an Eulerian-Lagrangian proppant transport model is developed, where the slurry flow rate and pressure are solved within the Eulerian regime, and the movement of solid proppant particles is solved within the Lagrangian regime. The adaptive proppant gridding scheme in the model allows a smaller grid size at the earlier fracturing stage for higher resolution and a larger grid size at the later fracturing stage for higher efficiency. Besides the physical model, an optimization module that utilizes advanced optimization algorithms such as genetic algorithm (GA) and pattern search algorithm (PSA) is proposed to automatically optimize the completion designs according to the preset targets. Numerical results show that hydraulic fracture propagation is under the combined influence of the in-situ stress, pumping schedule, natural fractures, and cluster placement. Hence, numerical simulation is needed to predict complex hydraulic fracture geometries under various geologic and completion settings. The complex hydraulic fracture geometries, together with fracturing fluid and proppant properties, also affect proppant placement. Moreover, the stress contrast at layer interfaces can cause proppant bridging and form barriers on the proppant transport path. The optimized completion designs increase effective hydraulic and propped areas, but they vary depending on the optimization targets. The developed hydraulic fracture model provides insights into the hydraulic fracturing process and benefits unconventional reservoir development
Book Synopsis Modeling of Complex Hydraulic Fractures in Naturally Fractured Formations by : Meng Cao (Ph. D.)
Download or read book Modeling of Complex Hydraulic Fractures in Naturally Fractured Formations written by Meng Cao (Ph. D.) and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The formation of complex fracture networks with nonplanar and multistranded shapes, due to the interaction between hydraulic and natural fractures, has been indicated by cores, mine-back experiments, and multiple numerous fracture diagnostic techniques. Having a better understanding of the mechanisms and implications of creating complex fracture networks would be a big step in improving hydrocarbon recovery and geothermal energy in naturally fractured formations. This dissertation presents the development of an integrated fracturing- production/geothermal simulator that can simulate multiple fracture propagation in naturally fractured reservoirs. It provides a new model for the interaction between hydraulic and natural fractures, dynamically distributes fluid and partitions proppant among multiple perforation clusters, simulates fluid flow and heat transfer in the coupled fracture-matrix system in an efficient manner, and speeds up the numerical computation for large-scale problems. This integrated fracturing-production/geothermal simulator enables a very computationally efficient solution by combining the displacement discontinuity method (DDM) for fracture propagation with a general Green’s function solution for fluid flow and heat transfer from the matrix to the fracture since there is no need to discretize the matrix domain. The fracturing model solves stresses and fluid pressure in a fully coupled manner by using DDM for rock deformation and a finite volume method for fluid flow inside fractures. In addition, the fluid distribution and proppant partitioning among multiple perforation clusters are solved dynamically. The production/geothermal simulator computes pressure and temperature using a fully implicit method for the fracture network domain, and solves the reservoir domain by using a semi-analytical solution. A fast, adaptive integral method (AIM) is used to reduce the computational time significantly when solving for the displacement field in a large complex fracture network. The key to the fast Fourier transform (FFT)-based adaptive integral method is the fast matrix-vector multiplication algorithm. The large dense matrix is decomposed into far- field and near-field components. The far-field component is computed by using the uniformly spaced Cartesian grid, and this component provides the foundation to perform discrete fast Fourier transform. The sparse near-field component is calculated by using the grid for fracture elements. Based on the split of the dense matrix into far-field and near- field components, FFT is applied to accelerate the multiplication of matrix and vector since no dense matrices are used. Finally, the new model is applied to two separate field studies, the Hydraulic Fracturing Test Site #2 (HFTS #2) and the Utah Frontier Observatory for Research in Geothermal Energy (FORGE)
Book Synopsis Advances in the Study of Fractured Reservoirs by : G.H. Spence
Download or read book Advances in the Study of Fractured Reservoirs written by G.H. Spence and published by Geological Society of London. This book was released on 2014-08-27 with total page 421 pages. Available in PDF, EPUB and Kindle. Book excerpt: Naturally fractured reservoirs constitute a substantial percentage of remaining hydrocarbon resources; they create exploration targets in otherwise impermeable rocks, including under-explored crystalline basement; and they can be used as geological stores for anthropogenic carbon dioxide. Their complex behaviour during production has traditionally proved difficult to predict, causing a large degree of uncertainty in reservoir development. The applied study of naturally fractured reservoirs seeks to constrain this uncertainty by developing new understanding, and is necessarily a broad, integrated, interdisciplinary topic. This book addresses some of the challenges and advances in knowledge, approaches, concepts, and methods used to characterize the interplay of rock matrix and fracture networks, relevant to fluid flow and hydrocarbon recovery. Topics include: describing, characterizing and identifying controls on fracture networks from outcrops, cores, geophysical data, digital and numerical models; geomechanical influences on reservoir behaviour; numerical modelling and simulation of fluid flow; and case studies of the exploration and development of carbonate, siliciclastic and metamorphic naturally fractured reservoirs.
Book Synopsis Coupled Geomechanics and Multiphase Flow Modeling in Naturally and Hydraulically Fractured Reservoirs by : Yanli Pei
Download or read book Coupled Geomechanics and Multiphase Flow Modeling in Naturally and Hydraulically Fractured Reservoirs written by Yanli Pei and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluid injection and production in highly fractured unconventional reservoirs could induce complex stress reorientation and redistribution. The strong stress sensitivity of fractured formations may also lead to non-negligible fracture opening or closure under the reservoir loading or unloading process. Hence, a coupled flow and geomechanics model is in high demand to assist with stress prediction and production forecast in unconventional reservoirs. In this dissertation, an enhanced geomechanics model is developed for fractured reservoirs and integrated with the in-house compositional reservoir simulator – UTCOMP for coupled flow and geomechanics modeling. The multiphase flow model is solved using the finite volume method (FVM) with an embedded discrete fracture model (EDFM) to represent flow through complex fractures. Based on static fracture assumption, the finite element method (FEM) is applied to solve the geomechanics model by incorporating fracture effects on rock deformation through pore pressure changes. An iterative coupling procedure is implemented between fluid flow and geomechanics, and the 3D coupled model is applied to predict spatiotemporal stress evolution in single-layer and multilayer unconventional reservoirs. To consider dynamic fracture properties, the geomechanics model is further enhanced by the extended finite element method (XFEM) with a modified linear elastic proppant model. The fracture surface is under the coeffects of pore pressure and proppant particles, and various enrichment functions are introduced to reproduce the discontinuous fields over fracture paths. The enhanced geomechanics model is validated against classical Sneddon and Elliot’s problem and presents a first-order spatial convergence rate. Numerical studies indicate that modeling fracture closure is necessary for poorly propped, highly stressed, or fast depleted reservoirs, and fracture opening can be significant under high permeability and low stiffness conditions. The coupled flow and geomechanics model is finally combined with a displacement discontinuity method (DDM) hydraulic fracture model to establish an integrated reservoir-geomechanics-fracture model for the end-to-end optimization of secondary stimulations. It is applied to Permian Basin and Sichuan Basin tight formations to optimize parent-child well spacing at different infill times. The integrated model provides hands-on guidelines for refracturing and infill drilling in multilayer unconventional reservoirs and can be easily adapted to other basins under their unique data
Book Synopsis Geomechanics, Fluid Dynamics and Well Testing, Applied to Naturally Fractured Carbonate Reservoirs by : Nelson Enrique Barros Galvis
Download or read book Geomechanics, Fluid Dynamics and Well Testing, Applied to Naturally Fractured Carbonate Reservoirs written by Nelson Enrique Barros Galvis and published by Springer. This book was released on 2018-05-02 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents an important step towards a deeper understanding of naturally fractured carbonate reservoirs (NFCRs). It demonstrates the various kinds of discontinuities using geological evidence, mathematical kinematics model and computed tomography and uses this as a basis for proposing a new classification for NFCRs. Additionally, this study takes advantage of rock mechanics theory to illustrate how natural fractures can collapse due to fluid flow and pressure changes in the fractured media. The explanations and mathematical modeling developed in this dissertation can be used as diagnostic tools to predict fluid velocity, fluid flow, tectonic fracture collapse, pressure behavior during reservoir depleting, considering stress-sensitive and non-stress-sensitive, with nonlinear terms in the diffusivity equation applied to NFCRs. Furthermore, the book presents the description of real reservoirs with their field data as the principal goal in the mathematical description of the realistic phenomenology of NFCRs.
Book Synopsis Numerical Modeling of Nonlinear Problems in Hydraulic Fracturing by : Endrina Rivas
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.
Book Synopsis Imaging the Mechanics of Hydraulic Fracturing in Naturally-fractured Reservoirs Using Induced Seismicity and Numerical Modeling by : Xueping Zhao
Download or read book Imaging the Mechanics of Hydraulic Fracturing in Naturally-fractured Reservoirs Using Induced Seismicity and Numerical Modeling written by Xueping Zhao and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Fractured Vuggy Carbonate Reservoir Simulation by : Jun Yao
Download or read book Fractured Vuggy Carbonate Reservoir Simulation written by Jun Yao and published by Springer. This book was released on 2017-08-08 with total page 253 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book solves the open problems in fluid flow modeling through the fractured vuggy carbonate reservoirs. Fractured vuggy carbonate reservoirs usually have complex pore structures, which contain not only matrix and fractures but also the vugs and cavities. Since the vugs and cavities are irregular in shape and vary in diameter from millimeters to meters, modeling fluid flow through fractured vuggy porous media is still a challenge. The existing modeling theory and methods are not suitable for such reservoir. It starts from the concept of discrete fracture and fracture-vug networks model, and then develops the corresponding mathematical models and numerical methods, including discrete fracture model, discrete fracture-vug model, hybrid model and multiscale models. Based on these discrete porous media models, some equivalent medium models and methods are also discussed. All the modeling and methods shared in this book offer the key recent solutions into this area.
Book Synopsis New numerical approaches to model hydraulic fracturing in tight reservoirs with consideration of hydro-mechanical coupling effects by : Lei Zhou
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.
