Numerical Simulation of a Coupled Hydro-Mechanical Model for CO ₂ Geosequestration in a Deep Saline Aquifer

Large-scale CO2 sequestration in deep saline aquifers is necessary to mitigate CO2 emission-related climate changes. However, the poroelastic changes due to CO2 injection can undermine the geomechanical stability of the aquifer, compromising the success of the CCS project. Therefore, this study examines the impact of CO2 injection in a deep saline aquifer using a hydro-mechanical model to demonstrate that incorporating solid mechanics enables the estimation of the pressure margin for fracture activation and shear slippage, thereby optimizing CO2 storage without inducing rock failure. First, the effect of solid deformation on CO2 plume migration and pressure buildup is compared with the results of the hydraulic model. It is found that considering solid deformation in the model significantly impacts the CO2 properties, affecting its distribution. The maximum pore pressure buildup occurs at the top of the aquifer adjacent to the injection zone, indicating the highest risk of rock failure in this region. Furthermore, the effects of reservoir permeability, porosity, anisotropy, injection velocity, initial temperature, and aquifer heterogeneities are further investigated numerically to predict the CO2 plume distribution, pore pressure buildup, vertical displacement, total stress evolution, and potential for tensile and shear failure. All of these parameters affect the distribution of scCO2 within the aquifer, thereby influencing the storage capacity. However, the storage capacity is significantly constrained by the pressure buildup in the reservoir. The study identifies that permeability is the key parameter contributing to the highest pore pressure buildup and rock failure.