Dual regulation of CO2 hydrate formation by clay mineral and kinetic promoter: mechanistic insights for marine sequestration

Hydrate-based CO 2 sequestration is recognized as a promising strategy to mitigate global warming due to its large storage potential and long-term stability. However, the role of clay minerals widely distributed in marine sediments in regulating hydrate formation remains poorly understood, hindering field-scale deployment. In this study, low-field nuclear magnetic resonance was used to investigate the effects of typical clay minerals (montmorillonite, illite, and kaolinite) on the kinetics and spatial evolution of CO 2 hydrate formation. The results demonstrate that, despite the presence of sodium dodecyl sulfate as a kinetic promoter, clay minerals generally exhibit an inhibitory effect. This inhibition arises from two synergistic mechanisms: clay-induced reduction in water activity limits the availability of free water molecules, while adsorption and electrostatic interactions between clay particles and the promoter modify the zeta potential and Derjaguin–Landau–Verwey–Overbeek interaction energy, increasing foam viscosity, suppressing local drainage, and narrowing Plateau–Gibbs channels, thereby weakening the promoting effect of the promoter. Among them, montmorillonite exhibits the strongest inhibition due to its large specific surface area and interlayer swelling, resulting in a 7.98% reduction in sequestration efficiency compared with the seawater system (70.57%). Considering clay-induced inhibition, the global and northern South China Sea hydrate-based CO 2 sequestration storage capacities were evaluated, indicating a reduction of at least 2520 Gt CO 2 globally and ∼23.43% locally. These findings provide pore-scale insights into clay–hydrate interactions and guidance for hydrate-based CO 2 sequestration site selection.