A Coupled Geomechanical–Geochemical Model for Predicting Caprock Breakthrough during CO 2 Storage

Creep deformation and chemical dissolution in caprock play a critical role in CO 2 sequestration by influencing the timing and likelihood of breakthrough. Under long-term stress and the interaction between CO 2 and water, the synergistic effects of creep and chemical dissolution gradually alter the pore structure. This weakens the sealing integrity of formation rocks and increases the risk of CO 2 migration through the overburden. Additionally, creep may couple with chemical dissolution processes, further modifying the properties of rocks. Therefore, considering their influence on the caprock is essential for accurately predicting breakthrough pressure and ensuring the long-term safety and reliability of CO 2 geological storage systems.This study proposes a multiphysics-coupled model to characterize the evolution of breakthrough pressure under nonlinear creep deformation and CO 2 -water-rock reaction kinetics. Validated against experimental data, the model demonstrates accurate predictions of breakthrough pressure and porosity under time-dependent geo-mechanical and geochemical processes. The initial breakthrough pressure of the caprock increases with increasing clay content, and a tighter pore structure corresponds to a higher breakthrough pressure. Stress variations promote rock creep, resulting in pore compaction and closure, thereby increasing the breakthrough pressure. Under specific temperature conditions, reduced activation energy ( E a ) and increased reaction rate constant ( k T ) exacerbate mineral dissolution, significantly enhancing pore connectivity and thereby reducing breakthrough pressure. This study provides a theoretical framework for dynamic caprock integrity assessment and multiobjective optimization of injection parameters, thereby supporting the safe deployment and long-term performance of carbon capture, utilization, and storage (CCUS) projects in alignment with carbon neutrality goals.