Investigation Into Fracture Network Permeability Evolution And Geothermal Reservoir Deformation In Response To Hydraulic Stimulation Utilizing Coupled Thermo Hydro Mechanical Modeling

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Investigation Into Fracture Network Permeability Evolution and Geothermal Reservoir Deformation in Response to Hydraulic Stimulation, Utilizing Coupled Thermo-hydro-mechanical Modeling

Author : Stefano Benato
Publisher :
ISBN 13 :
Total Pages : 320 pages
Book Rating : 4.:/5 (922 download)

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Book Synopsis Investigation Into Fracture Network Permeability Evolution and Geothermal Reservoir Deformation in Response to Hydraulic Stimulation, Utilizing Coupled Thermo-hydro-mechanical Modeling by : Stefano Benato

Download or read book Investigation Into Fracture Network Permeability Evolution and Geothermal Reservoir Deformation in Response to Hydraulic Stimulation, Utilizing Coupled Thermo-hydro-mechanical Modeling written by Stefano Benato and published by . This book was released on 2014 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: A series of hydraulic stimulations aimed at enhancing reservoir fracture-permeability were carried out in Desert Peak geothermal well 27-15 from September 2010 to March 2013. Fracture-permeability is controlled by the combined influence of induced thermal (T), hydrologic (H), and mechanical (M) processes, also known as THM. A hydro-mechanical (FLAC3D) model first, and a dual-porosity thermo-hydro-mechanical (TFReact) model second, are implemented to test if the proposed conceptual model is generally able to reproduce observations from the stimulation treatment. Numerical simulations are performed to determine: a) pore pressure diffusion and stress field modifications, b) development of mechanical deformation, and, above all c) relative impact of thermo-mechanical vs. shear deformation on reservoir permeability evolution. Both FLAC3D and TFReact coupled models display an evident cause-effect relation between stimulation of either the shallow or the extended intervals and shear deformation on a deep known structural feature, the STF ("Shearing Target Fault" - where most of the induced microseismicity is observed). Injection-induced thermo-mechanical and hydro-mechanical processes are found to govern permeability enhancement during stimulation of the shallow interval in well 27-15. Conversely, induced shear failure processes developing on a larger structural feature (STF) seem to control most of the permeability gain produced during the well 27-15 extended interval stimulation. Distinctive signatures at the well-head (pressure curve) are shown by the different permeability-change processes, and this is confirmed and matched by coupled THM simulation results.

Discrete Fracture Network Modeling of Hydraulic Stimulation

Author : Mark W. McClure
Publisher : Springer Science & Business Media
ISBN 13 : 3319003836
Total Pages : 96 pages
Book Rating : 4.3/5 (19 download)

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Book Synopsis Discrete Fracture Network Modeling of Hydraulic Stimulation by : Mark W. McClure

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.

Discrete Fracture Network Modeling of Hydraulic Stimulation

Author : Mark McClure
Publisher : Springer
ISBN 13 : 9783319003849
Total Pages : 90 pages
Book Rating : 4.0/5 (38 download)

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Book Synopsis Discrete Fracture Network Modeling of Hydraulic Stimulation by : Mark McClure

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.

Numerical Modeling of Hydraulic Fracture Propagation Using Thermo-hydro-mechanical Analysis with Brittle Damage Model by Finite Element Method

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Author : Kyoung Min
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (874 download)

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Book Synopsis Numerical Modeling of Hydraulic Fracture Propagation Using Thermo-hydro-mechanical Analysis with Brittle Damage Model by Finite Element Method by : Kyoung Min

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

Fracture Propagation and Permeability Change Under Poro-thermoelastic Loads & Silica Reactivity in Enhanced Geothermal Systems

Author :
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (873 download)

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Book Synopsis Fracture Propagation and Permeability Change Under Poro-thermoelastic Loads & Silica Reactivity in Enhanced Geothermal Systems by :

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.

Thermo-Hydro-Mechanical Modeling of Working Fluid Injection and Thermal Energy Extraction in Egs Fractures and Rock Matrix

Author :
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (967 download)

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Book Synopsis Thermo-Hydro-Mechanical Modeling of Working Fluid Injection and Thermal Energy Extraction in Egs Fractures and Rock Matrix by :

Download or read book Thermo-Hydro-Mechanical Modeling of Working Fluid Injection and Thermal Energy Extraction in Egs Fractures and Rock Matrix written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Development of enhanced geothermal systems (EGS) will require creation of a reservoir of sufficient volume to enable commercial-scale heat transfer from the reservoir rocks to the working fluid. A key assumption associated with reservoir creation/stimulation is that sufficient rock volumes can be hydraulically fractured via both tensile and shear failure, and more importantly by reactivation of naturally existing fractures (by shearing), to create the reservoir. The advancement of EGS greatly depends on our understanding of the dynamics of the intimately coupled rock-fracture-fluid-heat system and our ability to reliably predict how reservoirs behave under stimulation and production. Reliable performance predictions of EGS reservoirs require accurate and robust modeling for strongly coupled thermal-hydrological-mechanical (THM) processes. Conventionally, these types of problems have been solved using operator-splitting methods, usually by coupling a subsurface flow and heat transport simulators with a solid mechanics simulator via input files. An alternative approach is to solve the system of nonlinear partial differential equations that govern multiphase fluid flow, heat transport, and rock mechanics simultaneously, using a fully coupled, fully implicit solution procedure, in which all solution variables (pressure, enthalpy, and rock displacement fields) are solved simultaneously. This paper describes numerical simulations used to investigate the poro- and thermal- elastic effects of working fluid injection and thermal energy extraction on the properties of the fractures and rock matrix of a hypothetical EGS reservoir, using a novel simulation software FALCON (Podgorney et al., 2011), a finite element based simulator solving fully coupled multiphase fluid flow, heat transport, rock deformation, and fracturing using a global implicit approach. Investigations are also conducted on how these poro- and thermal-elastic effects are related to fracture permeability evolution.

Numerical study of the stimulation related thermo-hydro-mechanical processes in tight gas and deep geothermal reservoirs

Author : Wentao Feng
Publisher : Cuvillier Verlag
ISBN 13 : 3736961707
Total Pages : 204 pages
Book Rating : 4.7/5 (369 download)

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Book Synopsis Numerical study of the stimulation related thermo-hydro-mechanical processes in tight gas and deep geothermal reservoirs by : Wentao Feng

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.

Thermo-hydro-mechanical Analysis of Fractures and Wellbores in Petroleum/Geothermal Reservoirs

Author : Mohammadreza Safariforoshani
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (873 download)

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Book Synopsis Thermo-hydro-mechanical Analysis of Fractures and Wellbores in Petroleum/Geothermal Reservoirs by : Mohammadreza Safariforoshani

Download or read book Thermo-hydro-mechanical Analysis of Fractures and Wellbores in Petroleum/Geothermal Reservoirs written by Mohammadreza Safariforoshani and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The thesis considers three-dimensional analyses of fractures and wellbores in low-permeability petroleum/geothermal reservoirs, with a special emphasis on the role of coupled thermo-hydro-mechanical processes. Thermoporoelastic displacement discontinuity and stress discontinuity methods are elaborated for infinite media. Furthermore, injection/production-induced mass and heat transport inside fractures are studied by coupling the displacement discontinuity method with the finite element method. The resulting method is then used to simulate problems of interest in wellbores and fractures for related to drilling and stimulation. In the examination of fracture deformation, the nonlinear behavior of discontinuities and the change in status from joint (hydraulically open, mechanically closed) to hydraulic fracture (hydraulically open, mechanically open) are taken into account. Examples are presented to highlight the versatility of the method and the role of thermal and hydraulic effects, three-dimensionality, hydraulic/natural fracture deformation, and induced micro earthquakes. Specifically, injection/extraction operations in enhanced geothermal reservoirs and hydraulic/thermal stimulation of fractured reservoirs are studied and analyzed with reference to induced seismicity. In addition, the fictitious stress method is used to study three-dimensional wellbore stresses in the presence of a weakness plane. It is shown that the coupling of hydro-thermo-mechanical processes plays a very important role in low-permeability reservoirs and should be considered when predicting the behavior of fractures and wellbores. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151272

Thermo-Hydro-Mechanical Behavior of Conductive Fractures Using a Hybrid Finite Difference - Displacement Discontinuity Method

Author : Mohammadreza Jalali
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (126 download)

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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.

Discrete Element Modeling of Rock Deformation, Fracture Network Development and Permeability Evolution Under Hydraulic Stimulation

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Author :
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (873 download)

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Book Synopsis Discrete Element Modeling of Rock Deformation, Fracture Network Development and Permeability Evolution Under Hydraulic Stimulation by :

Download or read book Discrete Element Modeling of Rock Deformation, Fracture Network Development and Permeability Evolution Under Hydraulic Stimulation written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Key challenges associated with the EGS reservoir development include the ability to reliably predict hydraulic fracturing and the deformation of natural fractures as well as estimating permeability evolution of the fracture network with time. We have developed a physics-based rock deformation and fracture propagation simulator by coupling a discrete element model (DEM) for fracturing with a network flow model. In DEM model, solid rock is represented by a network of discrete elements (often referred as particles) connected by various types of mechanical bonds such as springs, elastic beams or bonds that have more complex properties (such as stress-dependent elastic constants). Fracturing is represented explicitly as broken bonds (microcracks), which form and coalesce into macroscopic fractures when external and internal load is applied. The natural fractures are represented by a series of connected line segments. Mechanical bonds that intersect with such line segments are removed from the DEM model. A network flow model using conjugate lattice to the DEM network is developed and coupled with the DEM. The fluid pressure gradient exerts forces on individual elements of the DEM network, which therefore deforms the mechanical bonds and breaks them if the deformation reaches a prescribed threshold value. Such deformation/fracturing in turn changes the permeability of the flow network, which again changes the evolution of fluid pressure, intimately coupling the two processes. The intimate coupling between fracturing/deformation of fracture networks and fluid flow makes the meso-scale DEM- network flow simulations necessary in order to accurately evaluate the permeability evolution, as these methods have substantial advantages over conventional continuum mechanical models of elastic rock deformation. The challenges that must be overcome to simulate EGS reservoir stimulation, preliminary results, progress to date and near future research directions and opportunities will be discussed. Methodology for coupling the DEM model with continuum flow and heat transport models will also be discussed.

Numerical Investigation of Fractured Reservoir Response to Injection/extraction Using a Fully Coupled Displacement Discontinuity Method

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Author : Byungtark Lee
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (76 download)

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Book Synopsis Numerical Investigation of Fractured Reservoir Response to Injection/extraction Using a Fully Coupled Displacement Discontinuity Method by : Byungtark Lee

Download or read book Numerical Investigation of Fractured Reservoir Response to Injection/extraction Using a Fully Coupled Displacement Discontinuity Method written by Byungtark Lee and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In geothermal reservoirs and unconventional gas reservoirs with very low matrix permeability, fractures are the main routes of fluid flow and heat transport, so the fracture permeability change is important. In fact, reservoir development under this circumstance relies on generation and stimulation of a fracture network. This thesis presents numerical simulation of the response of a fractured rock to injection and extraction considering the role of poro-thermoelasticity and joint deformation. Fluid flow and heat transport in the fracture are treated using a finite difference method while the fracture and rock matrix deformation are determined using the displacement discontinuity method (DDM). The fractures response to fluid injection and extraction is affected both by the induced stresses as well as by the initial far-field stress. The latter is accounted for using the non-equilibrium condition, i.e., relaxing the assumption that the rock joints are in equilibrium with the in-situ stress state. The fully coupled DDM simulation has been used to carry out several case studies to model the fracture response under different injection/extractions, in-situ stresses, joint geometries and properties, for both equilibrium and non-equilibrium conditions. The following observations are made: i) Fluid injection increases the pressure causing the joint to open. For non-isothermal injection, cooling increases the fracture aperture drastically by inducing tensile stresses. Higher fracture aperture means higher conductivity. ii) In a single fracture under constant anisotropic in-situ stress (non-equilibrium condition), permanent shear slip is encountered on all fracture segments when the shear strength is overcome by shear stress in response to fluid injection. With cooling operation, the fracture segments in the vicinity of the injection point are opened due to cooling-induced tensile stress and injection pressure, and all the fracture segments experience slip. iii) Fluid pressure in fractures increases in response to compression. The fluid compressibility and joint stiffness play a role. iv) When there are injection and extraction in fractured reservoirs, the cooler fluid flows through the fracture channels from the injection point to extraction well extracting heat from the warmer reservoir matrix. As the matrix cools, the resulting thermal stress increases the fracture apertures and thus increases the fracture conductivity. v) Injection decreases the amount of effective stress due to pressure increase in fracture and matrix near a well. In contrast, extraction increases the amount of effective stress due to pressure drop in fracture and matrix.

Simulated Evolution of Fractures and Fracture Networks Subject to Thermal Cooling

Author :
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (967 download)

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Book Synopsis Simulated Evolution of Fractures and Fracture Networks Subject to Thermal Cooling by :

Download or read book Simulated Evolution of Fractures and Fracture Networks Subject to Thermal Cooling written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Advancement of EGS requires improved prediction of fracture development and growth during reservoir stimulation and long-term operation. This, in turn, requires better understanding of the dynamics of the strongly coupled thermo-hydro-mechanical (THM) processes within fractured rocks. We have developed a physically based rock deformation and fracture propagation simulator by using a quasi-static discrete element model (DEM) to model mechanical rock deformation and fracture propagation induced by thermal stress and fluid pressure changes. We also developed a network model to simulate fluid flow and heat transport in both fractures and porous rock. In this paper, we describe results of simulations in which the DEM model and network flow & heat transport model are coupled together to provide realistic simulation of the changes of apertures and permeability of fractures and fracture networks induced by thermal cooling and fluid pressure changes within fractures. Various processes, such as Stokes flow in low velocity pores, convection-dominated heat transport in fractures, heat exchange between fluid-filled fractures and solid rock, heat conduction through low-permeability matrices and associated mechanical deformations are all incorporated into the coupled model. The effects of confining stresses, developing thermal stress and injection pressure on the permeability evolution of fracture and fracture networks are systematically investigated. Results are summarized in terms of implications for the development and evolution of fracture distribution during hydrofracturing and thermal stimulation for EGS.

3D Modeling of Coupled Rock Deformation and Thermo-poro-mechanical Processes in Fractures

Author : Chakra Rawal
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (813 download)

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Book Synopsis 3D Modeling of Coupled Rock Deformation and Thermo-poro-mechanical Processes in Fractures by : Chakra Rawal

Download or read book 3D Modeling of Coupled Rock Deformation and Thermo-poro-mechanical Processes in Fractures written by Chakra Rawal and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Problems involving coupled thermo-poro-chemo-mechanical processes are of great importance in geothermal and petroleum reservoir systems. In particular, economic power production from enhanced geothermal systems, effective water-flooding of petroleum reservoirs, and stimulation of gas shale reservoirs are significantly influenced by coupled processes. During such procedures, stress state in the reservoir is changed due to variation in pore fluid pressure and temperature. This can cause deformation and failure of weak planes of the formation with creation of new fractures, which impacts reservoir response. Incorporation of geomechanical factor into engineering analyses using fully coupled geomechanics-reservoir flow modeling exhibits computational challenges and numerical difficulties. In this study, we develop and apply efficient numerical models to solve 3D injection/extraction geomechanics problems formulated within the framework of thermo-poro-mechanical theory with reactive flow. The models rely on combining Displacement Discontinuity (DD) Boundary Element Method (BEM) and Finite Element Method (FEM) to solve the governing equations of thermo-poro-mechanical processes involving fracture/reservoir matrix. The integration of BEM and FEM is accomplished through direct and iterative procedures. In each case, the numerical algorithms are tested against a series of analytical solutions. 3D study of fluid injection and extraction into the geothermal reservoir illustrates that thermo-poro-mechanical processes change fracture aperture (fracture conductivity) significantly and influence the fluid flow. Simulations that consider joint stiffness heterogeneity show development of non-uniform flow paths within the crack. Undersaturated fluid injection causes large silica mass dissolution and increases fracture aperture while supersaturated fluid causes mineral precipitation and closes fracture aperture. Results show that for common reservoir and injection conditions, the impact of fully developed thermoelastic effect on fracture aperture tend to be greater compare to that of poroelastic effect. Poroelastic study of hydraulic fracturing demonstrates that large pore pressure increase especially during multiple hydraulic fracture creation causes effective tensile stress at the fracture surface and shear failure around the main fracture. Finally, a hybrid BEFEM model is developed to analyze stress redistribution in the overburden and within the reservoir during fluid injection and production. Numerical results show that fluid injection leads to reservoir dilation and induces vertical deformation, particularly near the injection well. However, fluid withdrawal causes reservoir to compact. The Mandel-Cryer effect is also successfully captured in numerical simulations, i.e., pore pressure increase/decrease is non-monotonic with a short time values that are above/below the background pore pressure.

Developing Coupled Fluid Flow and Geomechanics Simulators to Model Fracture Deformation

Author : Mohsen Babazadeh
Publisher :
ISBN 13 :
Total Pages : 440 pages
Book Rating : 4.:/5 (119 download)

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Book Synopsis Developing Coupled Fluid Flow and Geomechanics Simulators to Model Fracture Deformation by : Mohsen Babazadeh

Download or read book Developing Coupled Fluid Flow and Geomechanics Simulators to Model Fracture Deformation written by Mohsen Babazadeh and published by . This book was released on 2019 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation intends to advance fundamental understanding of two areas of interest in the petroleum industry: complex stimulated fracture network during hydraulic fracturing treatments and induced seismicity during wastewater disposal operations. Successful completion of hydraulic fractures in unconventional formations has been the primary source of increased oil and gas production in the US. However, field observations suggest that the hydraulic fracture networks are much more complex and different from the classical description of bi-wing planar fractures. Thus, the attempts to optimize this stimulation technique are hindered by the uncertainties in predicting the complex fracture network. A by-product of massive improvement in oil and gas production is a significant amount of water being co-produced from these formations. The common practice in the industry is to recycle wastewater for hydraulic fracturing purposes or reinject it into the reservoir through disposal wells. In certain regions of the US, this wastewater injection has led to historically high seismicity rates and earthquakes of Magnitude 5 and above which caused the public to be concerned. To maintain the social license to continue such operations, these concerns need to be addressed, and the physics behind such induced events need to be understood. Two novel hydraulic fracturing and induced seismicity simulators are developed that implicitly couple fluid flow with the stresses induced by fracture deformation in large, complex, three-dimensional discrete fracture networks. The simulators can describe the propagation of hydraulic fractures and opening and shear stimulation of natural fractures. Fracture elements can open or slide, depending on their stress state, fluid pressure, and mechanical properties. Fracture sliding occurs in the direction of maximum resolved shear stress. Nonlinear empirical relations are used to relate normal stress, fracture opening, and fracture sliding to fracture aperture and transmissivity. Field-scale hydraulic fracturing simulations were performed in a dense naturally fractured formation. Height containment of propagating hydraulic fractures between bedding layers is modeled with a vertically heterogeneous stress field or by explicitly imposing hydraulic fracture height containment as a model assumption. The propagating hydraulic fractures can cross natural fractures or terminate against them depending on the natural fracture orientation and stress anisotropy. The simulations demonstrate how interaction with natural fractures in the formation can help explain the high net pressures, relatively short hydraulic fracture lengths, and broad regions of microseismicity that are often observed in the field during stimulation in low permeability formations, some of which were not predicted by classical hydraulic fracturing models. Depending on input parameters, our simulations predicted a variety of stimulation behaviors, from long hydraulic fractures with minimal leakoff into surrounding fractures to broad regions of dense fracturing with a branching network of many natural and newly formed fractures. Induced seismicity simulator was developed to investigate the effects of multiple operational, hydraulic, and geophysical parameters on the magnitude of induced earthquakes. The rate-and-state framework is implemented to include the effect of fault nonlinear friction evolution and to model unstable earthquake rupture. The Embedded Discrete Fracture Model (EDFM) technique is used to model the fluid flow between the matrix and fractures efficiently. The results show that high-rate injections are more likely to induce a more significant earthquake, confirming the statistical correlation attributing induced events to high-rate injection wells. To understand the seismic occurrence outside of the injection zone, the effect of fault permeability structure on seismicity is studied by assigning non-uniform permeabilities as an input parameter. The model shows that the fault rupture is dominantly controlled by initial pressure and stress heterogeneity which ultimately affect the magnitude of an induced earthquake event

Thermo-Hydro-Mechanical Coupling in Fractured Rock

Author : Hans-Joachim Kümpel
Publisher : Springer Science & Business Media
ISBN 13 : 9783764302535
Total Pages : 364 pages
Book Rating : 4.3/5 (25 download)

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Book Synopsis Thermo-Hydro-Mechanical Coupling in Fractured Rock by : Hans-Joachim Kümpel

Download or read book Thermo-Hydro-Mechanical Coupling in Fractured Rock written by Hans-Joachim Kümpel and published by Springer Science & Business Media. This book was released on 2003-03-21 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: The supply and protection of groundwater, the production of hydrocarbon reservoirs, land subsidence in coastal areas, exploitation of geothermal energy, the long-term disposal of critical wastes ... What do these issues have in common besides their high socio-economic impact? They are all closely related to fluid flow in porous and/or fractured rock. As the conditions of fluid flow in many cases depend on the mechanical behavior of rocks, coupling between the liquid phase and the rock matrix can generally not be neglected. For the past five years or so, studies of rock physics and rock mechanics linked to coupling phenomena have received increased attention. In recognition of this, a Euroconference on thermo-hydro-mechanical coupling in fractured rock was held at Bad Honnef, Germany, in November 2000. Most of the twenty papers collected in this volume were presented at this meeting. The contributions lead to deeper insight in processes where such coupling is relevant.

Modeling and Analysis of Reservoir Response to Stimulation by Water Injection

Author : Jun Ge
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (75 download)

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Book Synopsis Modeling and Analysis of Reservoir Response to Stimulation by Water Injection by : Jun Ge

Download or read book Modeling and Analysis of Reservoir Response to Stimulation by Water Injection written by Jun Ge and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The distributions of pore pressure and stresses around a fracture are of interest in conventional hydraulic fracturing operations, fracturing during water-flooding of petroleum reservoirs, shale gas, and injection/extraction operations in a geothermal reservoir. During the operations, the pore pressure will increase with fluid injection into the fracture and leak off to surround the formation. The pore pressure increase will induce the stress variations around the fracture surface. This can cause the slip of weakness planes in the formation and cause the variation of the permeability in the reservoir. Therefore, the investigation on the pore pressure and stress variations around a hydraulic fracture in petroleum and geothermal reservoirs has practical applications. The stress and pore pressure fields around a fracture are affected by: poroelastic, thermoelastic phenomena as well as by fracture opening under the combined action of applied pressure and in-situ stress. In our study, we built up two models. One is a model (WFPSD model) of water-flood induced fracturing from a single well in an infinite reservoir. WFPSD model calculates the length of a water flood fracture and the extent of the cooled and flooded zones. The second model (FracJStim model) calculates the stress and pore pressure distribution around a fracture of a given length under the action of applied internal pressure and in-situ stresses as well as their variation due to cooling and pore pressure changes. In our FracJStim model, the Structural Permeability Diagram is used to estimate the required additional pore pressure to reactivate the joints in the rock formations of the reservoir. By estimating the failed reservoir volume and comparing with the actual stimulated reservoir volume, the enhanced reservoir permeability in the stimulated zone can be estimated. In our research, the traditional two dimensional hydraulic fracturing propagation models are reviewed, the propagation and recession of a poroelastic PKN hydraulic fracturing model are studied, and the pore pressure and stress distributions around a hydraulically induced fracture are calculated and plotted at a specific time. The pore pressure and stress distributions are used to estimate the failure potentials of the joints in rock formations around the hydraulic fracture. The joint slips and rock failure result in permeability change which can be calculated under certain conditions. As a case study and verification step, the failure of rock mass around a hydraulic fracture for the stimulation of Barnett Shale is considered. With the simulations using our models, the pore pressure and poro-induced stresses around a hydraulic fracture are elliptically distributed near the fracture. From the case study on Barnett Shale, the required additional pore pressure is about 0.06 psi/ft. With the given treatment pressure, the enhanced permeability after the stimulation of hydraulic fracture is calculated and plotted. And the results can be verified by previous work by Palmer, Moschovidis and Cameron in 2007.

Modeling and Characterization of Hydraulic Stimulation and Induced Seismicity in Geothermal and Shale Gas Reservoirs

Author : Mark William McClure
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (821 download)

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Book Synopsis Modeling and Characterization of Hydraulic Stimulation and Induced Seismicity in Geothermal and Shale Gas Reservoirs by : Mark William McClure

Download or read book Modeling and Characterization of Hydraulic Stimulation and Induced Seismicity in Geothermal and Shale Gas Reservoirs written by Mark William McClure and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The classical concept of hydraulic fracturing is that large, wing-shaped tensile fractures propagate away from the wellbore. However, in low matrix permeability settings such as Enhanced Geothermal Systems (EGS) and gas shale, hydraulic fracturing creates complex networks that may contain both newly formed fractures and stimulated natural fractures. In this research, the overall approach has been to integrate field observations, laboratory observations, and understanding of fundamental physical processes into computational modeling that is specifically designed for complex hydraulic fracturing and to apply the modeling to develop deeper understanding and to solve practical problems. A computational model was developed that coupled fluid flow, stresses induced by fracture opening and sliding, transmissivity coupling to deformation, friction evolution, and fracture propagation in two-dimensional discrete fracture networks. The model is efficient enough to simulate networks with thousands of fractures. A variety of novel techniques were developed to enable the model to be accurate, efficient, realistic, and convergent to discretization refinement in time and space. Testing demonstrated that simulation results are affected profoundly by the stresses induced by fracture deformation, justifying the considerable effort required to include these stresses in the model. Four conceptual models were formulated that represent the main hypotheses about stimulation mechanism from the literature of hydraulic fracturing. We refer to the stimulation mechanisms as Pure Opening Mode (POM), Pure Shear Stimulation (PSS), Mixed-Mechanism Stimulation (MMS), and Primary Fracturing with Shear Stimulation Leakoff (PFSSL). Computational models were used to investigate the properties of each mechanism. Geological factors that affect stimulation mechanism were identified. Techniques for diagnosing stimulation mechanism were devised that incorporate interpretation of bottom hole pressure during injection, shut-in, and production, microseismic relocations, and wellbore image logs. A Tendency to Shear Stimulation (TSS) test was proposed as a way to help diagnose the mechanism by unambiguously measuring a formation's ability to experience shear stimulation. Modeling results suggested several potential sources for error in estimation of the least principal stress in low matrix permeability settings. The Crack-like Shear Stimulation (CSS) mechanism was identified as a potentially important physical process that may control the spreading of shear stimulation through the interaction of fluid flow, deformation, and slip-transmissivity coupling. The computational model also has the capability to couple fluid flow with rate and state earthquake simulation. The model was used to investigate the interaction of fluid flow, permeability evolution, and induced seismicity during injection into a single large fault. Using the model, a variety of observations about induced seismicity in EGS were explained. Producing fluid back after injection and gradually reducing injection pressure during stimulation were identified as strategies for minimizing induced seismicity. A review of historical EGS projects demonstrated that the severity of induced seismicity has been correlated to the degree of brittle fault zone development in the interval of injection. The fracture networks at each project were categorized along a continuum from thick, porous fault zones to thin cracks. Observations from specific EGS projects fell across the full continuum, a result that has implications not only for induced seismicity, but for fractured reservoirs in general. A pressure transient analysis was performed using data from the EGS project at Soultz-sous-Forêts. At Soultz, fluid injection induced slip and transmissivity enhancement in large fault zones. The pressure transient analysis showed that these fault zones are best described as slabs of single porosity, single permeability material. Evidence of dual porosity behavior was not found.