Accurately predicting the dynamic evolution of permeability during CO2 injection into shale reservoirs is crucial for carbon sequestration and enhanced shale gas recovery. However, traditional permeability models often fail to comprehensively describe the full-range evolution of permeability throughout the entire CO2 injection process in shale—from the low-pressure gaseous state to the supercritical state. To address this limitation, this study develops a shale permeability evolution model based on a dual-elastic system comprising both the matrix and fractures, determined by component permeability weighting. By incorporating key factors such as mechanical degradation of the matrix, secondary adsorption, and strain hysteresis effects, we establish a governing equation for permeability evolution under multi-effect coupling. Utilizing an overlapping dual-elastic medium structure, we perform parallel cross-coupling numerical solutions, achieving an accurate representation of the nonlinear permeability evolution during full-pressure CO2 injection. Furthermore, a decoupled analysis of influencing effects reveals that the degradation of mechanical parameters of the matrix material due to CO2 defines the boundary thresholds for permeability fluctuation ranges. The asynchronous response between mechanical strain and adsorption strain significantly amplifies differences across evolutionary stages, leading to clearly distinguishable phase transitions. Additionally, the strain hysteresis effect prolongs the duration of evolution. Gas adsorption and mechanical responses jointly regulate the transition points between evolutionary stages, with the secondary adsorption-induced swelling strain particularly enhancing phase differentiation throughout the evolution process. This study also provides an in-depth analysis of the fundamental framework of fluid-solid coupled permeability modeling and explores the characteristics of different numerical simulation methods. The findings not only deepen the understanding of shale permeability evolution during CO2 injection but also offer valuable insights for theoretical modeling and numerical simulation of permeability in geological fluid sequestration.
LI et al. (Sun,) studied this question.