A large number of nanopores and complex fracture structures in shale reservoirs results in multi-scale flow of oil. With the development of shale oil reservoirs, the permeability of multi-scale media undergoes changes...A large number of nanopores and complex fracture structures in shale reservoirs results in multi-scale flow of oil. With the development of shale oil reservoirs, the permeability of multi-scale media undergoes changes due to stress sensitivity, which plays a crucial role in controlling pressure propagation and oil flow. This paper proposes a multi-scale coupled flow mathematical model of matrix nanopores, induced fractures, and hydraulic fractures. In this model, the micro-scale effects of shale oil flow in fractal nanopores, fractal induced fracture network, and stress sensitivity of multi-scale media are considered. We solved the model iteratively using Pedrosa transform, semi-analytic Segmented Bessel function, Laplace transform. The results of this model exhibit good agreement with the numerical solution and field production data, confirming the high accuracy of the model. As well, the influence of stress sensitivity on permeability, pressure and production is analyzed. It is shown that the permeability and production decrease significantly when induced fractures are weakly supported. Closed induced fractures can inhibit interporosity flow in the stimulated reservoir volume (SRV). It has been shown in sensitivity analysis that hydraulic fractures are beneficial to early production, and induced fractures in SRV are beneficial to middle production. The model can characterize multi-scale flow characteristics of shale oil, providing theoretical guidance for rapid productivity evaluation.展开更多
A coupling model is proposed in this paper by using the Green Function and Newman＇s product principle, and the solution method is provided here as well. This model can be used to describe the reservoir inflow and wel...A coupling model is proposed in this paper by using the Green Function and Newman＇s product principle, and the solution method is provided here as well. This model can be used to describe the reservoir inflow and wellbore flow for fishbone wells in an unsteady flow or pseudo-steady flow state. A case study indicates that the bottom hole pressure declines quickly in the unsteady flow period which is very short. The pressure drop per unit time remains unchanged under the pseudo-steady flow conditions. The distribution of flow rate along the main wellbore shows a wave shape under the unsteady flow condition, and the flow rate distribution in each branch is similar. The flow rate distribution along the main wellbore is irregular ＂U＂ shaped under the pseudo-steady flow condition, and the space-symmetrical branches have the same flow distribution pattern. In the initial production period, the flow rate increases significantly as the length of branches and the angle between branches and the main wellbore increase. As the production continues, the length and angle of branches have only a slight effect on the flow in fishbone wells.展开更多
Natural fractures(NFs)are common in shale and tight reservoirs,where staged multi-cluster fracturing of horizontal wells is a prevalent technique for reservoir stimulation.While NFs and stress interference are recogni...Natural fractures(NFs)are common in shale and tight reservoirs,where staged multi-cluster fracturing of horizontal wells is a prevalent technique for reservoir stimulation.While NFs and stress interference are recognized as significant factors affecting hydraulic fracture(HF)propagation,the combined influence of these factors remains poorly understood.To address this knowledge gap,a novel coupled hydromechanical-damage(HMD)model based on the phase field method is developed to investigate the propagation of multi-cluster HFs in fractured reservoirs.The comprehensive energy functional and control functions are established,while incorporating dynamic fluid distribution between multiple perforation clusters and refined changes in rock mechanical parameters during hydraulic fracturing.The HMD coupled multi-cluster HF propagation model investigates various scenarios,including single HF and single NF,reservoir heterogeneity,single HF and NF clusters,and multi-cluster HFs with NF clusters.The results show that the HMD coupling model can accurately capture the impact of approach angle(θ),stress difference and cementation strength on the interaction of HF and NF.The criterion of the open and cross zones is not fixed.The NF angle(a)is not a decisive parameter to discriminate the interaction.According to the relationship between approach angle(θ)and NF angle(a),the contact relationship of HF can be divided into three categories(θ=a,θ<a,andθ>a).The connected NF can increase the complexity of HF by inducing it to form branch fracture,resulting in a fractal dimension of HF as high as2.1280 at angles of±45°.Inter-fracture interference from the heel to the toe of HF shows the phenomenon of no,strong and weak interference.Interestingly,under the influence of NFs,distant HFs from the injection can become dominant fractures.However,as a gradually increases,inter-fracture stress interference becomes the primary factor influencing HF propagation,gradually superseding the dominance of NF induced fractures.展开更多
A vulcanized rubber layer is usually used on the head of an axisymmetric body to keep it streamlined and watertight.The elastic boundary condition is considered when the flow noise of an axisymmetric body is calculate...A vulcanized rubber layer is usually used on the head of an axisymmetric body to keep it streamlined and watertight.The elastic boundary condition is considered when the flow noise of an axisymmetric body is calculated,and we employ the mutual coupling method between the vulcanized rubber layer and the How around to solve the flow-noise field for an axisymmetric body in water.The results show that the deformation of the vulcanized rubber layer is reduced with the increase in Young's modulus.The Young's modulus of the rubber material should be large enough to keep it streamlined,and the noise power levels in the peak of the axisymmetric body are smaller than the other positions,which provides us with important theoretical support for laying acoustic arrays on the head of the body.展开更多
"Generalized mobility"is used to realize the unification of tube flow and seepage in form and the unification of commonly used linear and nonlinear flow laws in form,which makes it possible to use the same f..."Generalized mobility"is used to realize the unification of tube flow and seepage in form and the unification of commonly used linear and nonlinear flow laws in form,which makes it possible to use the same form of motion equations to construct unified governing equations for reservoirs of different scales in different regions.Firstly,by defining the generalized mobility under different flow conditions,the basic equation governing fluid flow in reservoir coupling generalized tube flow and seepage is established.Secondly,two typical well test analysis models for coupling tube flow and seepage flow are given,namely,pipe-shaped composite reservoir model and partially open cylindrical reservoir model.The log-log pressure draw-down type-curve of composite pipe-shaped reservoir model can show characteristics of two sets of linear flow.The log-log pressure drawdown plot of partially opened cylindrical reservoir model can show the characteristics of spherical flow and linear flow,as well as spherical flow and radial flow.The pressure build-up derivative curves of the two models basically coincide with their respective pressure drawdown derivative curves in the early stage,pulling down features in the late stage,and the shorter the production time is,the earlier the pulling down feature appears.Finally,the practicability and reliability of the models presented in this paper are verified by three application examples.展开更多
In this paper, the iterative coupling approach is proposed for applications to solving multiphase flow equation systems in reservoir simulation, as it provides a more flexible time-stepping strategy than existing appr...In this paper, the iterative coupling approach is proposed for applications to solving multiphase flow equation systems in reservoir simulation, as it provides a more flexible time-stepping strategy than existing approaches. The iterative method decouples the whole equation systems into pressure and saturation/concentration equations, and then solves them in sequence, implicitly and semi-implicitly. At each time step, a series of iterations are computed, which involve solving linearized equations using specific tolerances that are iteration dependent. Following convergence of subproblems, material balance is checked. Convergence of time steps is based on material balance errors. Key components of the iterative method include phase scaling for deriving a pressure equation and use of several advanced numerical techniques. The iterative model is implemented for parallel computing platforms and shows high parallel efficiency and scalability.展开更多
In this work, incompressible and compressible flows of background gas are characterized in argon inductively coupled plasma by using a fluid model, and the respective influence of the two flows on the plasma propertie...In this work, incompressible and compressible flows of background gas are characterized in argon inductively coupled plasma by using a fluid model, and the respective influence of the two flows on the plasma properties is specified. In the incompressible flow, only the velocity variable is calculated, while in the compressible flow, both the velocity and density variables are calculated. The compressible flow is more realistic; nevertheless, a comparison of the two types of flow is convenient for people to investigate the respective role of velocity and density variables. The peripheral symmetric profile of metastable density near the chamber sidewall is broken in the incompressible flow. At the compressible flow, the electron density increases and the electron temperature decreases. Meanwhile, the metastable density peak shifts to the dielectric window from the discharge center, besides for the peripheral density profile distortion, similar to the incompressible flow.The velocity profile at incompressible flow is not altered when changing the inlet velocity, whereas clear peak shift of velocity profile from the inlet to the outlet at compressible flow is observed as increasing the gas flow rate. The shift of velocity peak is more obvious at low pressures for it is easy to compress the rarefied gas. The velocity profile variations at compressible flow show people the concrete residing processes of background molecule and plasma species in the chamber at different flow rates. Of more significance is it implied that in the usual linear method that people use to calculate the residence time, one important parameter in the gas flow dynamics, needs to be rectified. The spatial profile of pressure simulated exhibits obvious spatial gradient. This is helpful for experimentalists to understand their gas pressure measurements that are always taken at the chamber outlet. At the end, the work specification and limitations are listed.展开更多
This paper gives a numerical study on the flow and temperature fields in an induced plasma reactor, which worked in 0.5 ATM with air as a working gas. We employed a two-dimensional mode of an inductively coupled plas...This paper gives a numerical study on the flow and temperature fields in an induced plasma reactor, which worked in 0.5 ATM with air as a working gas. We employed a two-dimensional mode of an inductively coupled plasma to calculate the temperature and flow field of the reactor as well as the generator. The algorithm is based on the solutions of the two-dimensional continuity, momentum, and energy equations in term of vorticity, stream function and enthalpy. An upwind finite-difference scheme was adopted to solve those equations with appropriate boundary conditions. The computed results show that there is a flat region with little parameter change in the reactor, that the diameter of the region is not much larger than that of the generator and that a deep change of parameter exists in the outer side of the region.展开更多
We present a workflow linking coupled fluid-flow and geomechanical simulation with seismic modelling to predict seismic anisotropy induced by non-hydrostatic stress changes. We generate seismic models from coupled sim...We present a workflow linking coupled fluid-flow and geomechanical simulation with seismic modelling to predict seismic anisotropy induced by non-hydrostatic stress changes. We generate seismic models from coupled simulations to examine the relationship between reservoir geometry, stress path and seismic anisotropy. The results indicate that geometry influences the evolution of stress,which leads to stress-induced seismic anisotropy. Although stress anisotropy is high for the small reservoir, the effect of stress arching and the ability of the side-burden to support the excess load limit the overall change in effective stress and hence seismic anisotropy. For the extensive reservoir, stress anisotropy and induced seismic anisotropy are high. The extensive and elongate reservoirs experience significant compaction, where the inefficiency of the developed stress arching in the side-burden cannot support the excess load.The elongate reservoir displays significant stress asymmetry,with seismic anisotropy developing predominantly along the long-edge of the reservoir. We show that the link betweenstress path parameters and seismic anisotropy is complex,where the anisotropic symmetry is controlled not only by model geometry but also the nonlinear rock physics model used. Nevertheless, a workflow has been developed to model seismic anisotropy induced by non-hydrostatic stress changes, allowing field observations of anisotropy to be linked with geomechanical models.展开更多
In light of previous work [Phys. Rev. E 60 4000 （1999）], a modified coupled-map car-following model is proposed by considering the headways of two successive vehicles in front of a considered vehicle described by th...In light of previous work [Phys. Rev. E 60 4000 （1999）], a modified coupled-map car-following model is proposed by considering the headways of two successive vehicles in front of a considered vehicle described by the optimal velocity function. The non-jam conditions are given on the basis of control theory. Through simulation, we find that our model can exhibit a better effect as p = 0.65, which is a parameter in the optimal velocity function. The control scheme, which was proposed by Zhao and Gao, is introduced into the modified model and the feedback gain range is determined. In addition, a modified control method is applied to a mixed traffic system that consists of two types of vehicle. The range of gains is also obtained by theoretical analysis. Comparisons between our method and that of Zhao and Gao are carried out, and the corresponding numerical simulation results demonstrate that the temporal behavior of traffic flow obtained using our method is better than that proposed by Zhao and Gao in mixed traffic systems.展开更多
In fractured geothermal reservoirs,the fracture networks and internal fluid flow behaviors can significantly impact the thermal performance.In this study,we proposed a non-Darcy rough discrete fracture network(NR-DFN)...In fractured geothermal reservoirs,the fracture networks and internal fluid flow behaviors can significantly impact the thermal performance.In this study,we proposed a non-Darcy rough discrete fracture network(NR-DFN)model that can simultaneously consider the fracture evolution and non-Darcy flow dynamics in studying the thermo-hydro-mechanical(THM)coupling processes for heat extraction in geothermal reservoir.We further employed the model on the Habanero enhanced geothermal systems(EGS)project located in Australia.First,our findings illustrate a clear spatial-temporal variation in the thermal stress and pressure perturbations,as well as uneven spatial distribution of shear failure in 3D fracture networks.Activated shear failure is mainly concentrated in the first fracture cluster.Secondly,channeling flow have also been observed in DFNs during heat extraction and are further intensified by the expansion of fractures driven by thermal stresses.Moreover,the combined effect of non-Darcy flow and fracture evolution triggers a rapid decline in the resulting heat rate and temperature.The NR-DFN model framework and the Habanero EGS's results illustrate the importance of both fracture evolution and non-Darcy flow on the efficiency of EGS production and have the potential to promote the development of more sustainable and efficient EGS operations for stakeholders.展开更多
With policy support for carbon capture,utilization,and storage(CCUS),an integrated approach that combines energy storage fracturing,CO_(2)-enhanced oil recovery(EOR),and storage emerges as a promising direction for th...With policy support for carbon capture,utilization,and storage(CCUS),an integrated approach that combines energy storage fracturing,CO_(2)-enhanced oil recovery(EOR),and storage emerges as a promising direction for the shale oil industry.The process of energy storage fracturing induces significant changes in the pressure and saturation of the medium.However,conventional simulations often overlook the effects of fracturing and shut-in operations on the seepage field and production performance.Furthermore,fractured shale reservoirs exhibit complex non-Darcy flow characteristics due to intricate pore structures and multi-scale porous media.A comprehensive understanding of flow mechanisms is essential for effective reservoir development and CO_(2) storage.This study establishes a multi-component simulation model that encompasses the life-cycle of fracturing,shut-in,production,and CO_(2) huff-n-puff processes,thereby ensuring the continuity of the seepage field.The model accounts for the effect of nano-confinement on phase behavior by modifying the equation of state.Furthermore,the flux term is adjusted to incorporate Maxwell–Stefan diffusion,pre-/post-Darcy flow,and stress sensitivity.The embedded discrete fracture model(EDFM)is employed to simulate multiphase flow within multi-scale media,and the results from the validation model align satisfactorily with those derived from ECLIPSE.Mechanism analysis indicates that the interaction of multiple mechanisms significantly influences both production and storage performance.Under the multi-mechanism coupling,the cumulative oil production increased by 12.01%,while the utilization and storage factors increased by 62.93%and 8.93%,respectively.The role of molecular diffusion in shale oil reservoirs may be overstated,contributing only a 0.26% enhancement in oil production.Simulation results show that the energy storage fracturing strategy can increase oil production and net present value by 12.47%and 15.07%,respectively.Sensitivity analysis indicates that the CO_(2) injection rate is the main factor affecting the recovery factor,followed by CO_(2) injection time and the number of cycles,with fracturing fluid volume having the least impact.This study develops a multi-process,multi-mechanism simulation framework for multi-scale shale oil reservoirs.This framework provides a robust evaluation system for CCUS-EOR,facilitating informed decision-making in fracturing stimulation,development planning,and parameter optimization.展开更多
基金This study was supported by the National Natural Science Foundation of China(U22B2075,52274056,51974356).
文摘A large number of nanopores and complex fracture structures in shale reservoirs results in multi-scale flow of oil. With the development of shale oil reservoirs, the permeability of multi-scale media undergoes changes due to stress sensitivity, which plays a crucial role in controlling pressure propagation and oil flow. This paper proposes a multi-scale coupled flow mathematical model of matrix nanopores, induced fractures, and hydraulic fractures. In this model, the micro-scale effects of shale oil flow in fractal nanopores, fractal induced fracture network, and stress sensitivity of multi-scale media are considered. We solved the model iteratively using Pedrosa transform, semi-analytic Segmented Bessel function, Laplace transform. The results of this model exhibit good agreement with the numerical solution and field production data, confirming the high accuracy of the model. As well, the influence of stress sensitivity on permeability, pressure and production is analyzed. It is shown that the permeability and production decrease significantly when induced fractures are weakly supported. Closed induced fractures can inhibit interporosity flow in the stimulated reservoir volume (SRV). It has been shown in sensitivity analysis that hydraulic fractures are beneficial to early production, and induced fractures in SRV are beneficial to middle production. The model can characterize multi-scale flow characteristics of shale oil, providing theoretical guidance for rapid productivity evaluation.
基金support from the National Science and Technology Major Projects of China(Grant No. 2011ZX05031-003)
文摘A coupling model is proposed in this paper by using the Green Function and Newman＇s product principle, and the solution method is provided here as well. This model can be used to describe the reservoir inflow and wellbore flow for fishbone wells in an unsteady flow or pseudo-steady flow state. A case study indicates that the bottom hole pressure declines quickly in the unsteady flow period which is very short. The pressure drop per unit time remains unchanged under the pseudo-steady flow conditions. The distribution of flow rate along the main wellbore shows a wave shape under the unsteady flow condition, and the flow rate distribution in each branch is similar. The flow rate distribution along the main wellbore is irregular ＂U＂ shaped under the pseudo-steady flow condition, and the space-symmetrical branches have the same flow distribution pattern. In the initial production period, the flow rate increases significantly as the length of branches and the angle between branches and the main wellbore increase. As the production continues, the length and angle of branches have only a slight effect on the flow in fishbone wells.
基金supported by the National Natural Science Foundation of China(No.52174045)。
文摘Natural fractures(NFs)are common in shale and tight reservoirs,where staged multi-cluster fracturing of horizontal wells is a prevalent technique for reservoir stimulation.While NFs and stress interference are recognized as significant factors affecting hydraulic fracture(HF)propagation,the combined influence of these factors remains poorly understood.To address this knowledge gap,a novel coupled hydromechanical-damage(HMD)model based on the phase field method is developed to investigate the propagation of multi-cluster HFs in fractured reservoirs.The comprehensive energy functional and control functions are established,while incorporating dynamic fluid distribution between multiple perforation clusters and refined changes in rock mechanical parameters during hydraulic fracturing.The HMD coupled multi-cluster HF propagation model investigates various scenarios,including single HF and single NF,reservoir heterogeneity,single HF and NF clusters,and multi-cluster HFs with NF clusters.The results show that the HMD coupling model can accurately capture the impact of approach angle(θ),stress difference and cementation strength on the interaction of HF and NF.The criterion of the open and cross zones is not fixed.The NF angle(a)is not a decisive parameter to discriminate the interaction.According to the relationship between approach angle(θ)and NF angle(a),the contact relationship of HF can be divided into three categories(θ=a,θ<a,andθ>a).The connected NF can increase the complexity of HF by inducing it to form branch fracture,resulting in a fractal dimension of HF as high as2.1280 at angles of±45°.Inter-fracture interference from the heel to the toe of HF shows the phenomenon of no,strong and weak interference.Interestingly,under the influence of NFs,distant HFs from the injection can become dominant fractures.However,as a gradually increases,inter-fracture stress interference becomes the primary factor influencing HF propagation,gradually superseding the dominance of NF induced fractures.
基金Supported by the National Natural Science Foundation of China under Grant No 11174235the Science and Technology Development Project of Shaanxi Province(No 2010KJXX-02)+1 种基金the Program for New Century Excellent Talents in University(No NCET-08-0455)the Excellent Doctorate Foundation of Northwestern Polytechnical University.
文摘A vulcanized rubber layer is usually used on the head of an axisymmetric body to keep it streamlined and watertight.The elastic boundary condition is considered when the flow noise of an axisymmetric body is calculated,and we employ the mutual coupling method between the vulcanized rubber layer and the How around to solve the flow-noise field for an axisymmetric body in water.The results show that the deformation of the vulcanized rubber layer is reduced with the increase in Young's modulus.The Young's modulus of the rubber material should be large enough to keep it streamlined,and the noise power levels in the peak of the axisymmetric body are smaller than the other positions,which provides us with important theoretical support for laying acoustic arrays on the head of the body.
基金Supported by the Scientific Research Project of Key Laboratory of Shaanxi Provincial Department of Education(13JS090)。
文摘"Generalized mobility"is used to realize the unification of tube flow and seepage in form and the unification of commonly used linear and nonlinear flow laws in form,which makes it possible to use the same form of motion equations to construct unified governing equations for reservoirs of different scales in different regions.Firstly,by defining the generalized mobility under different flow conditions,the basic equation governing fluid flow in reservoir coupling generalized tube flow and seepage is established.Secondly,two typical well test analysis models for coupling tube flow and seepage flow are given,namely,pipe-shaped composite reservoir model and partially open cylindrical reservoir model.The log-log pressure draw-down type-curve of composite pipe-shaped reservoir model can show characteristics of two sets of linear flow.The log-log pressure drawdown plot of partially opened cylindrical reservoir model can show the characteristics of spherical flow and linear flow,as well as spherical flow and radial flow.The pressure build-up derivative curves of the two models basically coincide with their respective pressure drawdown derivative curves in the early stage,pulling down features in the late stage,and the shorter the production time is,the earlier the pulling down feature appears.Finally,the practicability and reliability of the models presented in this paper are verified by three application examples.
文摘In this paper, the iterative coupling approach is proposed for applications to solving multiphase flow equation systems in reservoir simulation, as it provides a more flexible time-stepping strategy than existing approaches. The iterative method decouples the whole equation systems into pressure and saturation/concentration equations, and then solves them in sequence, implicitly and semi-implicitly. At each time step, a series of iterations are computed, which involve solving linearized equations using specific tolerances that are iteration dependent. Following convergence of subproblems, material balance is checked. Convergence of time steps is based on material balance errors. Key components of the iterative method include phase scaling for deriving a pressure equation and use of several advanced numerical techniques. The iterative model is implemented for parallel computing platforms and shows high parallel efficiency and scalability.
基金Project supported by the National Natural Science Foundations of China(Grant No.11305023)
文摘In this work, incompressible and compressible flows of background gas are characterized in argon inductively coupled plasma by using a fluid model, and the respective influence of the two flows on the plasma properties is specified. In the incompressible flow, only the velocity variable is calculated, while in the compressible flow, both the velocity and density variables are calculated. The compressible flow is more realistic; nevertheless, a comparison of the two types of flow is convenient for people to investigate the respective role of velocity and density variables. The peripheral symmetric profile of metastable density near the chamber sidewall is broken in the incompressible flow. At the compressible flow, the electron density increases and the electron temperature decreases. Meanwhile, the metastable density peak shifts to the dielectric window from the discharge center, besides for the peripheral density profile distortion, similar to the incompressible flow.The velocity profile at incompressible flow is not altered when changing the inlet velocity, whereas clear peak shift of velocity profile from the inlet to the outlet at compressible flow is observed as increasing the gas flow rate. The shift of velocity peak is more obvious at low pressures for it is easy to compress the rarefied gas. The velocity profile variations at compressible flow show people the concrete residing processes of background molecule and plasma species in the chamber at different flow rates. Of more significance is it implied that in the usual linear method that people use to calculate the residence time, one important parameter in the gas flow dynamics, needs to be rectified. The spatial profile of pressure simulated exhibits obvious spatial gradient. This is helpful for experimentalists to understand their gas pressure measurements that are always taken at the chamber outlet. At the end, the work specification and limitations are listed.
文摘This paper gives a numerical study on the flow and temperature fields in an induced plasma reactor, which worked in 0.5 ATM with air as a working gas. We employed a two-dimensional mode of an inductively coupled plasma to calculate the temperature and flow field of the reactor as well as the generator. The algorithm is based on the solutions of the two-dimensional continuity, momentum, and energy equations in term of vorticity, stream function and enthalpy. An upwind finite-difference scheme was adopted to solve those equations with appropriate boundary conditions. The computed results show that there is a flat region with little parameter change in the reactor, that the diameter of the region is not much larger than that of the generator and that a deep change of parameter exists in the outer side of the region.
基金the sponsors of the IPEGG project, BG, BP, Statoilthe Research Council UK (EP/K035878/1+1 种基金 EP/K021869/1 NE/L000423/1) for financial support
文摘We present a workflow linking coupled fluid-flow and geomechanical simulation with seismic modelling to predict seismic anisotropy induced by non-hydrostatic stress changes. We generate seismic models from coupled simulations to examine the relationship between reservoir geometry, stress path and seismic anisotropy. The results indicate that geometry influences the evolution of stress,which leads to stress-induced seismic anisotropy. Although stress anisotropy is high for the small reservoir, the effect of stress arching and the ability of the side-burden to support the excess load limit the overall change in effective stress and hence seismic anisotropy. For the extensive reservoir, stress anisotropy and induced seismic anisotropy are high. The extensive and elongate reservoirs experience significant compaction, where the inefficiency of the developed stress arching in the side-burden cannot support the excess load.The elongate reservoir displays significant stress asymmetry,with seismic anisotropy developing predominantly along the long-edge of the reservoir. We show that the link betweenstress path parameters and seismic anisotropy is complex,where the anisotropic symmetry is controlled not only by model geometry but also the nonlinear rock physics model used. Nevertheless, a workflow has been developed to model seismic anisotropy induced by non-hydrostatic stress changes, allowing field observations of anisotropy to be linked with geomechanical models.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11372166,11372147,61074142,and 11072117)the Scientific Research Fund of Zhejiang Province,China(Grant No.LY13A010005)+1 种基金the Disciplinary Project of Ningbo City,China(Grant No.SZXL1067)the K.C.Wong Magna Fund in Ningbo University,China,and the Government of the Hong Kong Administrative Region,China(Grant No.119011)
文摘In light of previous work [Phys. Rev. E 60 4000 （1999）], a modified coupled-map car-following model is proposed by considering the headways of two successive vehicles in front of a considered vehicle described by the optimal velocity function. The non-jam conditions are given on the basis of control theory. Through simulation, we find that our model can exhibit a better effect as p = 0.65, which is a parameter in the optimal velocity function. The control scheme, which was proposed by Zhao and Gao, is introduced into the modified model and the feedback gain range is determined. In addition, a modified control method is applied to a mixed traffic system that consists of two types of vehicle. The range of gains is also obtained by theoretical analysis. Comparisons between our method and that of Zhao and Gao are carried out, and the corresponding numerical simulation results demonstrate that the temporal behavior of traffic flow obtained using our method is better than that proposed by Zhao and Gao in mixed traffic systems.
基金funded by the National Natural Science Foundation of China (No.U22A20166)Science and Technology Foundation of Guizhou Province (No.QKHJC-ZK[2023]YB074)+2 种基金Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical EngineeringInstitute of Rock and Soil MechanicsChinese Academy of Sciences (No.SKLGME022009)。
文摘In fractured geothermal reservoirs,the fracture networks and internal fluid flow behaviors can significantly impact the thermal performance.In this study,we proposed a non-Darcy rough discrete fracture network(NR-DFN)model that can simultaneously consider the fracture evolution and non-Darcy flow dynamics in studying the thermo-hydro-mechanical(THM)coupling processes for heat extraction in geothermal reservoir.We further employed the model on the Habanero enhanced geothermal systems(EGS)project located in Australia.First,our findings illustrate a clear spatial-temporal variation in the thermal stress and pressure perturbations,as well as uneven spatial distribution of shear failure in 3D fracture networks.Activated shear failure is mainly concentrated in the first fracture cluster.Secondly,channeling flow have also been observed in DFNs during heat extraction and are further intensified by the expansion of fractures driven by thermal stresses.Moreover,the combined effect of non-Darcy flow and fracture evolution triggers a rapid decline in the resulting heat rate and temperature.The NR-DFN model framework and the Habanero EGS's results illustrate the importance of both fracture evolution and non-Darcy flow on the efficiency of EGS production and have the potential to promote the development of more sustainable and efficient EGS operations for stakeholders.
基金the National Natural Science Foundation of China(No.52341401)the National Key Research and Development Program of China under grant(No.2022YFE0206700)+4 种基金the National Natural Science Foundation of China(No.42302272)the State-funded Postdoctoral Fellowship Program(No.GZB20230862)the Science Foundation of China University of Petroleum,Beijing(No.2462023XKBH006)the Science Foundation of China University of Petroleum,Beijing(No.2462021YJRC012)the Open Project Program of Key Laboratory of Groundwater Resources and Environment(Jilin University),Ministry of Education(No.202306ZDKF05).
文摘With policy support for carbon capture,utilization,and storage(CCUS),an integrated approach that combines energy storage fracturing,CO_(2)-enhanced oil recovery(EOR),and storage emerges as a promising direction for the shale oil industry.The process of energy storage fracturing induces significant changes in the pressure and saturation of the medium.However,conventional simulations often overlook the effects of fracturing and shut-in operations on the seepage field and production performance.Furthermore,fractured shale reservoirs exhibit complex non-Darcy flow characteristics due to intricate pore structures and multi-scale porous media.A comprehensive understanding of flow mechanisms is essential for effective reservoir development and CO_(2) storage.This study establishes a multi-component simulation model that encompasses the life-cycle of fracturing,shut-in,production,and CO_(2) huff-n-puff processes,thereby ensuring the continuity of the seepage field.The model accounts for the effect of nano-confinement on phase behavior by modifying the equation of state.Furthermore,the flux term is adjusted to incorporate Maxwell–Stefan diffusion,pre-/post-Darcy flow,and stress sensitivity.The embedded discrete fracture model(EDFM)is employed to simulate multiphase flow within multi-scale media,and the results from the validation model align satisfactorily with those derived from ECLIPSE.Mechanism analysis indicates that the interaction of multiple mechanisms significantly influences both production and storage performance.Under the multi-mechanism coupling,the cumulative oil production increased by 12.01%,while the utilization and storage factors increased by 62.93%and 8.93%,respectively.The role of molecular diffusion in shale oil reservoirs may be overstated,contributing only a 0.26% enhancement in oil production.Simulation results show that the energy storage fracturing strategy can increase oil production and net present value by 12.47%and 15.07%,respectively.Sensitivity analysis indicates that the CO_(2) injection rate is the main factor affecting the recovery factor,followed by CO_(2) injection time and the number of cycles,with fracturing fluid volume having the least impact.This study develops a multi-process,multi-mechanism simulation framework for multi-scale shale oil reservoirs.This framework provides a robust evaluation system for CCUS-EOR,facilitating informed decision-making in fracturing stimulation,development planning,and parameter optimization.
