CO2 Trapping Mechanisms in Geological Carbon Sequestration: A Critical Review of Multiscale Processes and Storage Security

Geological carbon sequestration is a critical strategy for reducing atmospheric CO2 emissions and mitigating climate change; however, its long-term effectiveness depends on a robust understanding of subsurface trapping mechanisms. This review synthesizes recent advances in evidence-based CO2 trapping by systematically examining four primary mechanisms—structural/stratigraphic, residual (capillary), solubility, and mineral trapping—using insights from experimental studies, field observations, and numerical modeling. The analysis highlights that structural trapping provides immediate containment controlled by caprock integrity and reservoir geometry, while residual trapping immobilizes CO2 at the pore scale through capillary forces and multiphase flow dynamics. Over longer timescales, solubility trapping enhances storage security via dissolution and density-driven convection, whereas mineral trapping offers the most permanent form of sequestration through geochemical conversion to stable carbonates, albeit with slower kinetics. Recent findings emphasize the strong coupling among trapping mechanisms, the influence of wettability, heterogeneity, and flow regimes, and the growing role of engineered injection strategies and enhanced mineralization approaches. Overall, the review demonstrates that secure and scalable CO2 storage requires an integrated, multiscale understanding of these interacting processes, supported by improved monitoring, modeling, and experimental validation to reduce uncertainty and optimize storage performance.