Effects of end-member sediments on CO₂ hydrate formation: Implications for geological carbon storage

The conversion of CO₂ into solid hydrates for seabed storage is a promising greenhouse gas mitigation method, but the influence of reservoir types on hydrate formation remains unclear due to the complexity of marine sediments. This study examines three end-member sediments-montmorillonite, diatoms, and glass beads-representing clay-, silt-, and sand-dominated reservoirs, respectively. A series of kinetic experiments, morphological observations, and electrical sensitivity tests were conducted to assess the impact of these sediments on hydrate formation. The results show that the surface electric field and water migration properties of montmorillonite provide additional nucleation sites, promoting hydrate formation during the induction period. Gas consumption and hydrate conversion rate in the montmorillonite system were five times higher than those in the deionized water control group and ten times higher than those in the diatom and glass bead systems. While diatoms facilitated milder reactions in later stages, rapid hydrate formation in montmorillonite impeded further CO₂ mass transfer. Glass beads exhibited stringent formation conditions with Ostwald ripening effects. Hydrate films initially formed at the gas-liquid interface and spread into gas and water phases via surface tension-driven water migration. Electrical sensitivity tests revealed an inverse correlation between sensitivity and induction/reaction times across sediment types.