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

Carbon dioxide (CO 2 ) is a dominant greenhouse gas in the atmosphere that contributes to global warming. A promising approach to mitigate CO 2 emissions is CO 2 capture and storage (CCS) through clathrate hydrate crystallization under the seafloor; however, numerous issues regarding the mechanisms of concentration, efficiency, and stability of CO 2 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 CO 2 hydrate using the pressure oscillation method in porous media and evaluate the carbon sequestration efficiency. Our results indicate that CO 2 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 CO 2 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 CO 2 solubility fluctuations, significantly increase the rate of later hydrate formation, and shorten the period of hydrate sequestration. • Enhanced CO 2 sequestration method is proposed based on hydrate technology. • CO 2 hydrate formation characteristics are obtained by T 2 logmean time distribution analysis. • Pressure oscillation can effectively break the mass transfer barriers. • Pressure oscillation can significantly shorten the period of hydrate sequestration.