A Time-Dependent Hydro-mechanical Coupling Model of Reservoir Sandstone During CO₂ Geological Storage

Time-dependent deformation of rock affects the structural and hydrologic properties in terms of porosity and permeability, which can directly influence security and injectivity of CO₂ geological storages in a saline aquifer. To investigate the time-dependent response of deep saline aquifer subjected to CO₂ geological storage in terms of the permeability and deformation evolution of stratum rock skeleton under external stresses and pore fluid pressure, the rock permeability evolution under the flow-through of sodium chloride solution with mixed CO₂ and creep curves of reservoir rock sample was studied after long-term hydro-mechanical laboratory testing. Furthermore, the time-dependent hydro-mechanical coupling mathematical model, including the porous creep constitutive equation and the time-dependent relationship between volumetric deformation and porosity, was proposed to characterize the long-term influences of evolving permeability and deformation in a saline reservoir. To verify this time-dependent hydro-mechanical coupling model, the coupled multicomponent multiphase flow and geomechanical simulator TOUGH-FLAC could be applied with the embedded user-defined constitutive model of porous creep constitutive equation and the corrected permeability as function of volumetric strain in the external module. In general, calculated results are akin to observed results, and the time-dependent hydro-mechanical coupling model has practical value.