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Collaborating Authors
Wang, Yarlong
Abstract Wellbore integrity in a gas hydrate bearing formation during drilling and production is a great challenge in the energy industry since a complex thermal-hydraulic-mechanical interaction with decomposed solid hydrate process is involved. A wellbore temperature increase and/or depressurization process may induce additional stresses and thermal and fluid flows, which may trigger wellbore instability, sand production, and undesired fracturing. Production-related wellbore integrity issues such as solid production during wellbore depressurization or heating are also widely observed and studied. To understand the thermal-hydraulic-mechanical behavior with hydrate decomposition (THMD) process and to simulate the THM responses of hydrate gas bearing sediments to wellbore pressure and temperature variations under a given in-situ stress regime during drilling and production, a fully coupled THMD model is presented in this paper. The conceptual THMD model with simplified semi-analytical solutions for the induced stress, pore pressure, and temperature at the wellbore and inside the formation is discussed. A linear Mohr-Coulomb criterion is utilized to define the onset of the wellbore instability or plastic yielding when sand production defined by effective plastic strain (EPS) is considered with a cohesion dependent on hydrate saturation. Numerical method with Laplace transformation is used to solve the transformed homogeneous PDE. We conclude that thermally- and hydration-induced stresses will affect wellbore integrity during hydrate gas production due to wellbore pressure reduction and temperature increase. Unlike the stress perturbation in the conventional gas reservoir, critical temperature and pressure for the equilibrium phase change must be surpassed to induce additional incremental stresses due to the hydrate decomposition. Additional fluid mass and energy transfer may take place with induced temperature and pore pressure because of the hydrate decomposition/recomposition. In addition, the hydrate saturation changes due to the typical drilling strategy applied may reduce the hydrate formation significantly, which will affect the design of production pressure control and management. Thus, pressure optimization is crucial for both maximum production and wellbore integrity.
- Europe > Norway (0.67)
- North America > United States > Texas (0.46)
- North America > Canada > British Columbia (0.28)
- North America > United States > Alaska (0.28)
ABSTRACT: A coupled formulation is developed, based on a dual-porosity model to simulate a naturally fractured aquifer under non-isothermal and two-phase fluid flow conditions. Two-phase flow coupled to the deformation in a dual-porosity type media, and local thermal non-equilibrium (LTNE) conditions are imposed for the energy transport between and among, respectively, two fluid and porous solid phases. Along and through them conductive and convective mechanisms may dominate. More importantly, different physical parameters reflect different rock types and fracture characteristics are defined and interpreted so that the corresponding rock behaviors may be represented. Models and physical interpretations developed and proposed by different researchers are reviewed and compared. The model is applicable in reservoir simulation of naturally fractured formations with two-phasefluidflow, such as safety design of CO2 injection and sequestration, oil/gas storage injectivity or capacity evaluation, and heat extraction design in geo-thermal reservoir. 1. INTRODUCTION The coupled thermo-hydro-mechanical (THM) response of a fluid-saturated naturally fractured medium is characterized by bulk skeleton deformation, fluid diffusion and heat transport processes via fluid flux through both matrix and fractures. The hydraulic process of the fluid flowing through the fissured porous skeleton and the mechanical responses to external loading may be calculated by poroelastic theory and the two processes are also coupled with each other simultaneously. When the saturated fissured porous block is heated, the pore pressure inside the porous may rise depending on the formation permeability, solid expands and these two processes shall be interacting with each other following the effective stress principle. Evaluations of THM responses under multiphase fluid flow via the entire porous formation subject to THM loading can be conducted based on their fundamental behaviors following an extended poroelastic constitutive laws with dual porosity and corresponding transport mechanisms in each fluid phase. Either drained moduli for the bulk porous skeleton and those for the matrix and fractured systems separately may be used. Accumulation and dissipation of the thermal potential on and through the fissured porous skeleton and fluid also follow energy conservation equilibrium condition. Separate non-equilibrium thermal energy transport processes may take place along or through the porous matrix and the fracture network, mainly by conduction within the solid matrix phase, depending on its permeability, and by conductive and convective heat transfer through the moving fluid in the fractures system. In an extreme scenario, perhaps typical of Granites and shales, through both the moving fluid and matrix heat flux is completely conductive, whereas in another extreme scenario, perhaps a naturally fractured sandstone, the heat flux along the solid phases (matrix and fracture) and fluid are conductive but a combined conductive and convective is dominating the fluid mass transport through the fracture. In addition, heat exchange between each adjacent system, i.e. between each fluid and solid system are transferable which are typically characterized by heat exchange coefficients assuming an instantaneous equilibrium condition may be reached at the contact areas. A convective components may also be incorporated depending on the hydraulic characteristics such as the fluid velocity between these systems. Simulating naturally fractured formation, early modeling work on the dual-porosity model initialized by Barentblatt et al, 1960 and Warren and Root 1963 assumed porous block is rigid. Studies on deformable skeleton were imposed later by Duguid and Lee, 1977 and a mixture theory is proposed by Aifantis [1977,1979,1980]. In these early work, the cross-coupling between the fracture and pore volume is ignored [Khalili and Valliappan, 1996; Khalili, 2003, 2008]. To improve Aifantisโs early work, improvement and extension of the dual-porosity formulations for single phase fluid flow are developed [Wilson and Aifantis, 1982; Khaled et al, 1984, Valliappan and Khalili-Naghadeh, 1990, Berryman and Wang, 1995; Berryman and Bridge, 2002; Berryman 2002, Khalili-Naghadeh and Valliappan 1991, Chen and Tuefel, 1997. Khalili and Valliappan, 1996, and Khalili and Selvadurai, 2003. The dual-porosity concept to include multiphase flow subject to a number of restrictions are also introduced [Lewis and Ghafouri, 1997; Bai et al., 1998; Pao and Lewis, 2002, and Nair et al. ,2005, Khalili, 2008].
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.54)
- North America > United States > Texas > Fort Worth Basin > Barnett Shale Formation (0.99)
- North America > United States > Pennsylvania > Warren Field (0.93)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (1.00)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Multiphase flow (1.00)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Drillstem/well testing (1.00)
ABSTRACT: Heat exchange and energy extraction from a low-permeability reservoir are important processes for EGS design. Cold water is circulated from a wellbore and carries warmer water up to the surface. Depending on the circulation velocity and temperature out to the surface, different extraction efficiency may be achieved. Such an efficiency also depends on the depth of the energy source, formation temperature gradient, hydraulic and thermal properties of the porous solid skeleton and fluid. Thus a model coupling the energy transfer from an injecting tubing, annulus and into/from the low-permeability formation must be established. A semi-analytical solution is obtained for energy transfer between tubing, annulus and porous formation. Temperature, fluid pressure and induced stresses can be calculated and heat extraction power can be evaluated by an integration over the circulating rate with annulus outlet temperature. One may evaluate and design a geothermal system based on the model proposed. 1 Introduction As one of cleaner and more economic viable resource, heat energy extracted from geothermal formations becomes increasingly attractive. Also decreasing cost of geothermal installations in deep hot dry rock (HDR), enhanced geothermal systems (EGS) have the potential to replace more costly and environmentally unfriendly technologies [Grasby 2011]. The advances in EGS are primarily motivated by the success and technologies developed in Enhanced Oil Recovery (EOR), staged hydraulic fracturing (SHF) of shale gas and shale oil formations with and without super-critical CO2 and enhancing methane while sequestrating CO2 permanently. While these technologies are gaining more attention for environmental purposes, energy extraction efficiency and economic evaluation are under serious considerations worldwide. Considering production and injection in a low-permeability HDR or shale formation, energy transfer and fluid flow, also carrying the energy, into a porous intact rock, which itself allows both fluid flow (ฮp) and heat flow (ฮT) through are diffusive processes. HF can increase productivity and further stimulate energy transfer processes by creating a large surface area. Seeing the critical role of hydraulic fracturing (McLennan 1980) in EGS to achieve higher production efficiency, extensive studies are conducted [McTique, 1989; Karshige, 1989, Wang and Papamichos, 1994; 1999, Wu et al., 2015, 2017]. It has been pointed out that drastic thermal stress changes when massive cold water is injected at a lower temperature into a deep HDR formation contributes to the initiation and propagation of fractures in HDR, which can not be justified by traditional hydraulic fracturing theory and is therefore referred to as thermal fracturing [Clifford et al. 1991, Charlez et al. 1996]. Calculation of thermal stress changes that induces thermal fractures and their geometry changes including the thermal cracking processes requires a fully coupled thermal-hydraulic-mechanical (THM) model. This model consists of two mass balance equations for the fracture and a matrix systems diffusion process with small portion of free gas flow. A dynamic thermal cracking zone can be created and considered once the effective tensile stresses exceed the tensile strength near a wellbore or hydraulic fractures. In addition, two mass balance equations, in the fracture and matrix systems respectively, and one equilibrium equations are coupled to the two aforementioned energy equations. Parts of these equations are nonlinear and stress dependent. Therefore solving this set of equations is challenging, yet the solution is a key to practical completion design and consequently researchers and companies have allocated effort intensively to find answer to this challenge in different ways. Over the years, there have been quite a few attempts made to simulate thermal fractures [Abousleiman et al. 1996, Tarasovs and Ghassemi 2010, Hofmann et al. 2016]. Nevertheless, there are challenges yet to overcome at least from the following perspectives. At first, to accurately assess the thermal stresses, thermally induced pressures, and the thermal conduction/convection associated to the temperature change in the reservoir must be properly addressed [Wang and Dusseault 2003]; secondly, to evaluate the size of a potential zone surrounding a wellbore or fracture where thermal crack could be initiated and propagating, from these cracked zone larger surface areas are created and more heat energy exchanged; Thirdly, boundary element method has been proposed and a kernel function corresponding to a temperature change inside the hydraulic fracture is required. Developing such a function and determining the heat transfer process along a hydraulic fracture with thermal leakage term are critical. Fourthly, calculating the radius and evaluating the THM properties of a thermal cracking zone surrounding a wellbore and hydraulic fracture are extremely important for thermal energy extraction and heat exchange efficiency in the EGS. lastly, to predict the thermal fracture propagation in a fractured deep geothermal reservoir, THM perturbations due to the interaction from the natural fractures must be properly addressed [Wang 2017].
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.94)
- Energy > Renewable > Geothermal > Geothermal Resource (1.00)
- Energy > Oil & Gas > Upstream (1.00)
ABSTRACT: Enhanced Geothermal Systems (EGS) in Hot Dry Rock (HDR), Enhanced Oil Recovery (EOR), and staged hydraulic fracturing (HF) in low-permeability reservoirs such as shale gas/oil formations using supercritical CO2 are technologies gaining more attention recently for environmental and energy efficiency considerations. In low-permeability HDR or shale formations, staged HF stimulates energy transfer processes by creating a large surface contact area. Heat flow (ฮT) is also allowed to penetrate through the porous solid skeleton and fluid saturating the pore volume of the porous skeleton. The mobile fluid on the other hand permits both conductive and convective heat transfer, the later is particularly dominating the heat transfer along the HF and Natural Fracture (NF) network due to (ฮp) and depending on fluid velocity (vf).Thus the enhanced heat flux accompanies by a larger heat exchange surface area either due to the incremental convection or HF may enhance both energy and fluid productivity in low-permeability formation. Focusing on the thermally induced response near a HY and impact on the fracture propagation and energy transport along these fractures, a computational algorithm for a coupled THM system and induced responses in the vicinity of a hydraulically loaded fracture (HF) and interaction in and between those from NF is developed and reviewed in this paper. 1. Introduction Thermally induced mechanical response and hydraulic flow are both important to induced stresses and fluid flow in geothermal related processes. Mechanical deformation is defined by both local thermal gradient and effective stresses which are associated with both the thermal stresses and the pore pressure including the thermal induced component at the same time. In general the temperature difference is controlled by both conductive and convective heat transfer in the porous media and the thermal conductivity and specific heat in the fluid are normally used to characterize these two processes, respectively[Boley and Weiner, 1960, Carslaw and Jeager, 1959]. Solving problems in a borehole and cavity, McTique 1986 and Kurashige 1989 extended Biot isothermal consolidation theory. Both conductive and convective heat transport is incorporated in the formulation yet only the analytical solutions for conduction and a steady state solution for convective heat transport is presented by Kuraishige 1989. Semi-analytical solutions with different boundary conditions and coupled conductive-convective heat transport subject to a circular borehole are also developed by Wang and Papamichos, 1994, Wang and Dusseault, 2003. All these solutions are however developed by postulating an overall thermal conductivity on the bulk porous skeleton and fluid inside, thus a local thermal equilibrium condition is assumed instantaneously. The fluid conductivity is normally 0.6 W/m.K and those in a porous rock formation can vary between 2.71-2.8 W/m.K in Run Segment and Rosemanowes HDR [Murphy et al., 1977, Elsworth, 1989, Gelet et al., 2012]. The final parameter defining the heat conduction is the thermal diffusivity, c0 = ฮป/ฯCp, where ฮป, ฯ, and Cp are conductivity, density and specific heat of the medium, respectively. Considering heat conduction alone, the thermal diffusivities from variety of rocks and fluid are significantly different, changing between 10 to 10 cm/s [Karashige, 1989; McTique, 1990]. Aforementioned studies focused on thermal process when an instantaneously thermal equilibrium can be reached between the solid skeleton and the pore fluid locally. The conditions for local thermal equilibrium to prevail have been examined in a number of investigations [Nield 1998, Minkowycz et al. 1999, Vadasz 2007 and Virto et al. 2009]. They concluded that in a local thermal equilibrium may hold when the interstitial heat transfer coefficient between the solid and fluid is very large and the ratio of pore surface area to pore volume is sufficiently high. These conditions may be described using the Nield number Ni [Nield, 1998; Vadasz, 2007] or the Sparrow number Sp (Minkowycz et al., 1999), which is defined as hL/rhk, where h, L, rh, k, interstitial heat transfer coefficient, the thickness of the porous plate, pore throat radius, and thermal conductivity. The SP can also be expressed in terms of Nusselt number and one may refer to Minkowycz et al., [1999]. In general the classical heat transfer theory with local thermal equilibrium can still be used when the Sparrow number Sp>1, which corresponds to large interstitial heat transfer coefficients h and high pore surface area to pore volume ratios. For problems with small Sparrow numbers, local thermal equilibrium is no longer valid and local thermal non-equilibrium heat transfer poroelasticity theories should be used to precisely evaluate the pore pressure and thermal stresses in the porous media. Such a difference between heat transfer can be enlarged by the moving fluid, i.e. convection. The convective heat transfer by moving fluid must be incorporated for the high-permeability formation. This again highlights the different mechanisms and energy transport processes between the porous media and the fluid inside, i.e. if we may approximate heat exchanges and transfer between the moving fluid either inside a HY or NF as an equilibrium process without larger numerical errors. In addition, the thermally induced mechanical response coupled to the temperature on the porous solid skeleton adjacent to these HF will be calculated based on both the thermal induced stresses and pore pressure generated by either the conductive and convective heat inside the pore volume. The geometry changes due to thermal effects may be defined and quantified by the THM system developed in the following. Simulating THM responses in a fractured formation, Khalili and Selvadurai, 2003 and Gelet et al., 2012 presented a general THM formulation by a dual porosity model. Although a HDR is simulated in their studies, a dual porosity model may be applied to those heavily fractured formations. Furthermore a hydraulic fracturing is mainly caused by the tensile effective stress near the borehole wall due to the wellbore pressure increase, and this concentration can be affected by both pore pressure change due to hydraulic process and the thermally induced stresses due to a temperature difference between the injected fluid and from those on the solid skeleton and the fluid inside these porous skeleton in a EGS. In petroleum engineering, the pressurized fluid often has a temperature different from the formation, while if high compressible fluid is used, a borehole is often heated up. Because of the thermal expansion and the differential expansitivities of the rock skeleton and the fluid contained inside the pores, thermal stresses may be induced leading to borehole yield and failure. The quantification of the impact of thermally-induced stresses on hydraulic fracturing requires knowledge of the heat transport properties and the thermal expansion behavior. For either cases mentioned above, the ultimate hot water productivity and energy transport or heat exchange processes depend on the geometry change of the HF created and those geometry changes inside the NF network and it is the thermally induced effects are the focus in this paper.
- North America > Canada (0.68)
- North America > United States > Texas > Harris County > Houston (0.28)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.75)
- Energy > Oil & Gas > Upstream (1.00)
- Energy > Renewable > Geothermal > Geothermal Resource (0.54)
ABSTRACT A heat extraction process between hot dry rock formation and a cylindrical well with a tubing installed inside is simulation. A wellbore/reservoir coupling formulation is proposed and solutions for temperature, fluid pressure along the annulus and tubing, and the induced pore pressure, temperature and stresses induced inside the HDR formation adjacent to the well bore are calculated. The heat extraction from the geothermal formation by injecting cold water into a tubing and circulating out from the annulus can be evaluated. Surface temperature and cold water injecting rate can be controlled to achieve desired efficiency. 1 INTRODUCTION Enormous geothermal energy resources exist worldwide (Raymond 2018). It can supply a renewable and clean source of power with the heat removed from a geothermal reservoir being naturally replenished. The high capacity factor of geothermal power makes geothermal energy particularly attractive as a renewable base load energy supply. With the decreasing cost of geothermal installations in deep hot dry rock (HDR), enhanced geothermal systems (EGS) have the potential to replace more costly and environmentally unfriendly technologies (Grasby 2011). EGS in HDR and Enhanced Oil Recovery (EOR) or hydraulic fracturing (HF) of shale gas and shale oil formations using super-critical CO2 are technologies gaining more attention recently for environmental and energy efficiency considerations. In low-permeability HDR or shale formations, HF may further stimulate energy transfer processes by creating a large surface area. Fluid (ฮp) and heat flow (ฮT) through intact rock are diffusion processes, and enhanced flux accompanies a larger exchange surface area. Seeing the critical role of hydraulic fracturing (McLennan 1980) in EGS to achieve higher production efficiency, extensive studies are conducted (McTique, 1989; Karshige, 1989, Wang and Papamichos, 1994; 1999, Wang 2017). It has been pointed out that drastic thermal stress changes when massive cold water is injected at a lower temperature into a deep HDR formation contributes to the initiation and propagation of fractures in HDR, which can not be justified by traditional hydraulic fracturing theory and is therefore referred to as thermal fracturing (Clifford et al.1991, Charlez et al. 1996). Calculation of thermal stress changes that induces thermal fractures and their geometry changes including the thermal cracking processes requires a fully coupled thermal-hydraulic-mechanical (THM) model. This model consists of two mass balance equations for the fracture and a matrix systems diffusion process with small portion of free gas flow. A dynamic thermal cracking zone can be created and considered once the effective tensile stresses exceed the tensile strength near a wellbore or hydraulic fractures. In addition, two mass balance equations, in the fracture and matrix systems respectively, and one equilibrium equations are coupled to the two aforementioned energy equations. Parts of these equations are nonlinear and stress dependent. Therefore solving this set of equations is challenging, yet the solution is a key to practical completion design and consequently researchers and companies have allocated effort intensively to find answer to this challenge in different ways. Over the years, there have been quite a few attempts made to simulate thermal fractures (Abousleiman et al. 1996, Tarasovs and Ghassemi 2010, Hofmann et al. 2016). Nevertheless, there are challenges yet to overcome at least from the following perspectives. First, to accurately assess the thermal stress, the thermal convection associated temperature distribution in reservoir must be properly addressed (Wang and Dusseault 2003); secondly, to evaluate the potential zone in the reservoir where thermal fracture could be initiated and propagating, from a boundary condition's perspective, the overburden stress redistribution within the reservoir must also be carefully addressed (Osorio et al. 1999); Thirdly, boundary element method has been proposed and a kernel function corresponding to a temperature change inside the hydraulic fracture is required. Developing such a function and determining the heat transfer process along a hydraulic fracture with thermal leakage term are critical. Fourthly, calculating the radius and evaluating the THM properties of a thermal cracking zone surrounding a wellbore and hydraulic fracture are extremely important for thermal energy extraction and heat exchange efficiency in the EGS. lastly but not the least, to predict the thermal fracture propagation in a fractured deep geothermal reservoir, the disturbance by local natural fractures must be properly addressed (Wang 2017).
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.95)
- Energy > Oil & Gas > Upstream (1.00)
- Energy > Renewable > Geothermal > Geothermal Resource > Hot Dry Rock (0.44)
Abstract Refracturing is often required in shale and tight gas formations because of inadequate initial HF design or unexpectedly rapid production decline. Water blocking because of fracturing liquid incompatibility, unexpected proppant embedment and crushing, shorter or curved primary fracture length because of premature screen off, general pressure depletion, primary fracture mis-orientation from stress shadowing, unfavourable poroelastic effects limiting the performance of the stimulated volume, and, in general, formation permeability reduction from stress sensitivity may all contribute to unsatisfactory or rapidly declining production. We emphasize the role of geomechanics in candidate screening and review the major factors leading to production decline in unconventional reservoirs. Although the fracture geometry may be altered in a staged fracturing process, the primary focus should be given to the formation permeability enhancement either due to shear dilation or induced fractured network elongation.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.51)
- North America > United States > Texas > Haynesville Shale Formation (0.99)
- North America > United States > Texas > Fort Worth Basin > Barnett Shale Formation (0.99)
- North America > United States > Louisiana > Haynesville Shale Formation (0.99)
- (4 more...)
Abstract A general formulation for a coupled Thermal-Hydraulic-Mechanical with hydrate Dissociation (THMD) system is developed and applied to sand prediction for conventional gas and gas hydrate bearing sediments (GHBS). Two-phase fluid and conductive heat flow are coupled to an elastoplastic geomechanics model. Series of solutions for simplified models are presented. Fundamental geomechanics behaviors before and after plastic yielding, sanding, and gas hydrate dissociation are defined, discussed, and simulated differently and sanding onset for both conventional gas formations and GHBS are defined by an effective plastic strain (EPS) criterion. The accuracy and reliability of the proposed conventional model are verified by comparing the model prediction with the results of hollow cylinder tests on two different types of sandstone. The advantages of using the EPS over stress-based criteria as an indicator for onset of borehole collapse and sand production are discussed. Introducing a moving gas hydrate dissociation zone (front), the fundamental geomechanics behaviour and elastoplastic deformation of the skeleton formation are highlighted. The effects on sand prediction due to the characteristics of non-linear plastic yielding criteria and gas flow in porous media are also emphasized.
- North America > Canada (0.93)
- Asia (0.93)
- Europe > Norway (0.66)
- North America > United States > Texas (0.46)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.35)
- North America > United States > Gulf of Mexico > Central GOM > East Gulf Coast Tertiary Basin > Green Canyon > Block 237 > Green Canyon 237 Field > Wang Well (0.93)
- North America > Cuba > Gulf of Mexico (0.93)
- North America > United States > Alaska > North Slope Basin > Prudhoe Bay Field (0.89)
Abstract The effectiveness of a hydraulic fracturing technology has been primarily attributed to a creation of the geometry in the primary fracture. This concept however has been challenged particularly in low-permeability formations in which the size of a Stimulating Reservoir Volume (SRV) becomes the most important issue. Unlike the primary fracture, the area in the SRV is controlled by the fundamental geomechanics behaviors of the formation and a secondary fracture network propagation with possible different modes, and more importantly by the formation permeability change which is controlled by the induced stresses near the primary fracture. In this paper, the induced stresses near a hydraulic fracture in a pure elastic, poroelastic, dual-porosity media are analyzed and compared in order to characterize the low-permeability, sandstone and fractured formations, respectively. The general formulation for a fractured reservoir by a dual porosity model is developed and pore pressures and stresses near a wellbore and a hydraulic fracture are highlighted for production enhancement as the permeability change near a wellbore or a hydraulic fracture may contribute to such an enhancement significantly. Those key parameters controlling the pressure and stresses change and numerical method used are analyzed and presented.
Abstract A dual porosity formulations coupled geomechanics to two-phase fluid Flow in fractured reservoirs are developed and a Petrov-Galerkin finite element method is utilized. Formulations for saturation, with a time variable only, is incorporated with the displacement and pore pressures, which are fully coupled and solved simutaneously. A linear shape function is used for the pressures and saturation, and a quadratic one for displacement to avoid numerical oscillation. A consistent weighting function similar to the linear shape function is used for all interpolated variables. Solutions for pore pressures, stresses, and saturations near a wellbore and a hydraulic fracture in the dual porosity system simulating a fractured reservoir and in different phases are presented
Gravitational, tectonic, and earth structure related effects are major concerns for in-situ stresses determinations. The stress magnitude change, principal stress rotations and the range of these changes can be crucial for fracturing propagation, their geometry change, and ultimately the productivity. A field case is studied, focusing on quantified stress perturbations, the procedure for far field stress determination, and stress redistribution near a hydraulic tip for re-directed propagation analyses.
- North America > United States (1.00)
- Asia (0.96)
- Geology > Structural Geology (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)