Mechanical integrity analysis of caprock during the CO₂ injection phase

CO 2 geological storage is one of the important means to mitigate the greenhouse effect. The safe underground storage of CO 2 largely depends on the mechanical integrity of the caprock. This paper establishes a fluid-solid coupling model for CO 2 geological storage to study the changes in pore pressure, vertical displacement, and effective stress in the caprock during the CO 2 injection process. Combined with the Mohr-Coulomb criterion, the study determines whether mechanical failure occurs in the caprock. The results indicate that, at the beginning of CO 2 injection, significant changes occur in the pore pressure, vertical displacement, and effective stress at the bottom of the caprock near the injection well, which then tend to stabilize; the maximum pore pressure at the bottom of the caprock reaches 36.08 MPa; the caprock near the injection well is considered the most critical area, where the risk of mechanical failure is highest; at the end of CO 2 injection, the stress state does not reach the limit, and the caprock remains stable.