Dependence of the hydrate-based CO2 storage process on the hydrate reservoir environment in high-efficiency storage methods

CO2 storage in marine hydrates has a high gas storage capacity and long-term storage stability, which has attracted extensive research interest in the field of greenhouse gas (GHG) reduction. The dependence of CO2 hydrate formation properties on the reservoir environment in high-efficiency storage methods should be examined to determine suitable hydrate-based techniques. In this study, the nuclear magnetic resonance (NMR) technique was employed to analyze the hydrate distribution and phase transition process. Hydrates form a solid phase, which results in the T2 relaxation time. The T2 curve in large pores shifts to the left. Several parameters, including the initial water saturation, CO2 formation pressure and temperature, and the application of chemical additives (SiO2 nanoparticles, SDS and their mixtures) were analyzed. A high initial water saturation and suitable temperatures and pressures in marine sediments were found to be conducive to high-efficiency CO2 storage. Regardless of the used additive, the bound water in relatively small pores remained almost unchanged, and the free-water content in large pores linearly decreased with increasing hydrate saturation. Compared to pure seawater, the optimal kinetics additive content was 0.15 wt% SiO2 nanoparticles in 8-hour tests, which improved the water conversion percentage, GHG migration and CO2 storage efficiency by 49.2%, 41.30% and 4.17%, respectively. These results provide greater insights into the hydrate-based CO2 storage in marine sediments and contribute to potential kinetic additive applications.