Enhanced CO2 sequestration based on hydrate technology with pressure oscillation in porous medium using NMR

Carbon dioxide (CO2) is a dominant greenhouse gas in the atmosphere that contributes to global warming. A promising approach to mitigate CO2 emissions is CO2 capture and storage (CCS) through clathrate hydrate crystallization under the seafloor; however, numerous issues regarding the mechanisms of concentration, efficiency, and stability of CO2 hydrate sequestration in seafloor sediments remain under dispute. This study employed low-field nuclear magnetic resonance (NMR) measurements to observe the in-situ formation of CO2 hydrate using the pressure oscillation method in porous media and evaluate the carbon sequestration efficiency. Our results indicate that CO2 hydrates are preferentially formed in large pore spaces, further hindering the subsequent gas contact with water in isolated pores. Additionally, a high initial water saturation is more conducive to high-quantity CO2 hydrate capture and sequestration in a pressure variation environment with a higher driving force. The proposed pressure oscillation method could effectively break the mass transfer barriers in the later stage of hydrate formation with the help of CO2 solubility fluctuations, significantly increase the rate of later hydrate formation, and shorten the period of hydrate sequestration.