CO₂ geological storage is one of the most important means to mitigate the greenhouse effect.The safety of CO₂ securely stored in underground reservoirs largely depends on the mechanical integrity of the caprock.This paper establishes a coupled fluid-solid 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.It analyzes the effects of CO₂ injection rate,caprock elastic parameters,and geostress factors on the occurrence of tensile and shear failures in the caprock.The results indicate that,at the initial stage of CO₂ injection, changes in pore pressure,vertical displacement,and effective stress at the bottom of the cap near the injection well are significant but gradually stabilize thereafter.The area near the injection well is considered the most critical part of the caprock,where the risk of mechanical failure is greatest.During the CO₂ injection process,the injection rate and geostress factors have the most significant impact on the occurrence of mechanical failures in the caprock.The findings of this study provide a theoretical basis for assessing the long-term stability and safety of CO₂ geological storage systems.