Effects of Stress on CO2 Hydrate Sequestration Stability in Deep-sea Sediments: A Molecular Dynamics Simulation Study

Hydrate-based CO 2 sequestration technology represents a highly promising strategy for deep-sea carbon storage. The stability of CO 2 hydrate sequestration within the confined space of deep-sea sediments is a critical factor determining its feasibility. In this study, molecular dynamics (MD) simulations were utilized to investigate the effects of shear, compressive, and shear-compressive coupling stress on the structural stability, phase transition, rheological behavior, and mechanical properties of CO 2 hydrate within clay nanopores of various sizes. The results indicate that under shear stress, CO 2 hydrate undergoes dissociation progressing from the periphery towards the center, with the extent of dissociation directly proportional to the shear rate. Additionally, the bound water layer coating the clay surface exhibits shear-thinning behavior. Under compressive stress, the CO 2 hydrate displays overall structural destruction. Under shear-compressive coupling stress, the dissociation of CO 2 hydrate is accelerated, but the destruction is primarily dominated by compressive stress-induced dissociation. Furthermore, pore size significantly influences the stability of CO 2 hydrate. This study reveals, at the microscopic level, the influence laws of stress type, magnitude, and pore size on the stability of CO 2 hydrate in confined spaces, providing a theoretical basis for evaluating the stability of CO 2 hydrate sequestration in deep-sea sediments.