Mechanical integrity analysis of caprock during the CO2 injection phase

Abstract

CO₂ geological storage is one of the important means to mitigate the greenhouse effect. The safe underground storage of CO₂ largely depends on the mechanical integrity of the caprock. This paper establishes a fluid-solid coupling model for CO₂ geological storage to study the changes in pore pressure, vertical displacement, and effective stress in the caprock during the CO₂ 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 CO₂ 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 CO₂ injection, the stress state does not reach the limit, and the caprock remains stable.