One kind of 3D coupled thermo-hydro-mechanical-migratory model for saturated-unsaturated dual-porosity medium was established,in which the stress field and the temperature field are single,but the seepage field and th...One kind of 3D coupled thermo-hydro-mechanical-migratory model for saturated-unsaturated dual-porosity medium was established,in which the stress field and the temperature field are single,but the seepage field and the concentration field are double,and the influences of sets,spaces,angles,continuity ratios,stiffness of fractures on the constitutive relationship of the medium can be considered.The relative three-dimensional program of finite element method was also developed.By comparing with the existing computation example,reliability of the model and the program were verified.Taking a hypothetical nuclear waste repository as a calculation example,the radioactive nuclide leak was simulated numerically with both the rock mass and the buffer being unsaturated media,and the temperatures,negative pore pressures,flow velocities,nuclide concentrations and normal stresses in the rock mass were investigated.The results showed that the temperatures,negative pore pressures and nuclide concentrations in the buffer all present nonlinear changes and distributions that even though the saturation degree in porosity is only about 1/9 of that in fracture,the flow velocity of underground water in fracture is about 6 times of that in porosity because the permeability coefficient of fracture is almost four orders higher than that of porosity,and that the regions of stress concentration occur at the vicinity of two sides of the boundary between buffer and disposal pit wall.展开更多
Based on the characteristics of fractures in naturally fractured reservoir and a discrete-fracture model, a fracture network numerical well test model is developed. Bottom hole pressure response curves and the pressur...Based on the characteristics of fractures in naturally fractured reservoir and a discrete-fracture model, a fracture network numerical well test model is developed. Bottom hole pressure response curves and the pressure field are obtained by solving the model equations with the finite-element method. By analyzing bottom hole pressure curves and the fluid flow in the pressure field, seven flow stages can be recognized on the curves. An upscaling method is developed to compare with the dual-porosity model （DPM）. The comparisons results show that the DPM overestimates the inter-porosity coefficient ）, and the storage factor w. The analysis results show that fracture conductivity plays a leading role in the fluid flow. Matrix permeability influences the beginning time of flow from the matrix to fractures. Fractures density is another important parameter controlling the flow. The fracture linear flow is hidden under the large fracture density. The pressure propagation is slower in the direction of larger fracture density.展开更多
This paper compares numerical modeling of the effect of stress on solute transport （advection and matrix diffusion） in fractured rocks in which fracture apertures are correlated with fracture lengths. It is mainly m...This paper compares numerical modeling of the effect of stress on solute transport （advection and matrix diffusion） in fractured rocks in which fracture apertures are correlated with fracture lengths. It is mainly motivated by the performance and safety assessments of underground radioactive waste repositories. Five research teams used different approaches to model stress/deformation, flow and transport pro- cesses, based on either discrete fracture network or equivalent continuum models. The simulation results derived by various teams generally demonstrated that rock stresses could significantly influence solute transport processes through stress-induced changes in fracture apertures and associated changes in per- meability. Reasonably good agreement was achieved regarding advection and matrix diffusion given the same fracture network, while some observed discrepancies could be explained by different mechanical or transport modeling approaches.展开更多
Stress-dependent permeability models are developed for the organic pores and inorganic cleats/fractures in unconventional gas reservoirs,which are modeled as Biot’s porous media of dual-porosity.Further considering m...Stress-dependent permeability models are developed for the organic pores and inorganic cleats/fractures in unconventional gas reservoirs,which are modeled as Biot’s porous media of dual-porosity.Further considering multiple flow mechanisms such as dynamic effects of gas flow and surface diffusion,apparent permeability models are obtained to investigate the characteristics of unconventional gas migration.Compared to the gas transfer in single-porosity reservoirs,the gas migration ability of cleats in dual-porosity stratums rarely changes while that of organic pores is greatly improved because cleats sustain major geomechanical shrinkage deformation when the pore pressure drops.Further,the mass flux of reservoirs is dominated by the mass flux of cleats,which has a lower peak value,but a much longer production term than those in single-porosity reservoirs due to the interaction between organic pores and cleats.Parametric analysis is conducted to identify key factors significantly impacting mass flux in unconventional reservoirs.Reasons for the mass flux variation are also explored in terms of gas migration ability and pore pressure distribution.展开更多
基金supported by the National Key Basic Research and Development Program of China("973"Project)(Grant No.2010CB732101)the Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering(Grant No.SKLQ008)
文摘One kind of 3D coupled thermo-hydro-mechanical-migratory model for saturated-unsaturated dual-porosity medium was established,in which the stress field and the temperature field are single,but the seepage field and the concentration field are double,and the influences of sets,spaces,angles,continuity ratios,stiffness of fractures on the constitutive relationship of the medium can be considered.The relative three-dimensional program of finite element method was also developed.By comparing with the existing computation example,reliability of the model and the program were verified.Taking a hypothetical nuclear waste repository as a calculation example,the radioactive nuclide leak was simulated numerically with both the rock mass and the buffer being unsaturated media,and the temperatures,negative pore pressures,flow velocities,nuclide concentrations and normal stresses in the rock mass were investigated.The results showed that the temperatures,negative pore pressures and nuclide concentrations in the buffer all present nonlinear changes and distributions that even though the saturation degree in porosity is only about 1/9 of that in fracture,the flow velocity of underground water in fracture is about 6 times of that in porosity because the permeability coefficient of fracture is almost four orders higher than that of porosity,and that the regions of stress concentration occur at the vicinity of two sides of the boundary between buffer and disposal pit wall.
基金Project supported by the National Natural Science Foundation of China(No.5140232)the National Science and Technology Major Project(No.2011ZX05038003)the China Postdoctoral Science Foundation(No.2014M561074)
文摘Based on the characteristics of fractures in naturally fractured reservoir and a discrete-fracture model, a fracture network numerical well test model is developed. Bottom hole pressure response curves and the pressure field are obtained by solving the model equations with the finite-element method. By analyzing bottom hole pressure curves and the fluid flow in the pressure field, seven flow stages can be recognized on the curves. An upscaling method is developed to compare with the dual-porosity model （DPM）. The comparisons results show that the DPM overestimates the inter-porosity coefficient ）, and the storage factor w. The analysis results show that fracture conductivity plays a leading role in the fluid flow. Matrix permeability influences the beginning time of flow from the matrix to fractures. Fractures density is another important parameter controlling the flow. The fracture linear flow is hidden under the large fracture density. The pressure propagation is slower in the direction of larger fracture density.
基金the context of the international DECOVALEX-2011 ProjectLBNL from NDA via SERCO TAS was provided through the U.S. Department of Energy Contract No. DE-AC02-05CH11231supported by the Ministry of Education of the Czech Republic within the SGS project No. 7822/115 on the TUL
文摘This paper compares numerical modeling of the effect of stress on solute transport （advection and matrix diffusion） in fractured rocks in which fracture apertures are correlated with fracture lengths. It is mainly motivated by the performance and safety assessments of underground radioactive waste repositories. Five research teams used different approaches to model stress/deformation, flow and transport pro- cesses, based on either discrete fracture network or equivalent continuum models. The simulation results derived by various teams generally demonstrated that rock stresses could significantly influence solute transport processes through stress-induced changes in fracture apertures and associated changes in per- meability. Reasonably good agreement was achieved regarding advection and matrix diffusion given the same fracture network, while some observed discrepancies could be explained by different mechanical or transport modeling approaches.
基金the National Natural Science Foundation of China(Grant Nos.12102372 and 11872324)the Open Research Fund of CNMGE Platform&NSCC-TJ(Grant No.CNMGE2023011).
文摘Stress-dependent permeability models are developed for the organic pores and inorganic cleats/fractures in unconventional gas reservoirs,which are modeled as Biot’s porous media of dual-porosity.Further considering multiple flow mechanisms such as dynamic effects of gas flow and surface diffusion,apparent permeability models are obtained to investigate the characteristics of unconventional gas migration.Compared to the gas transfer in single-porosity reservoirs,the gas migration ability of cleats in dual-porosity stratums rarely changes while that of organic pores is greatly improved because cleats sustain major geomechanical shrinkage deformation when the pore pressure drops.Further,the mass flux of reservoirs is dominated by the mass flux of cleats,which has a lower peak value,but a much longer production term than those in single-porosity reservoirs due to the interaction between organic pores and cleats.Parametric analysis is conducted to identify key factors significantly impacting mass flux in unconventional reservoirs.Reasons for the mass flux variation are also explored in terms of gas migration ability and pore pressure distribution.
