Research progress of the kinetics on natural gas hydrate replacement by CO2-containing mixed gas: A review

A clear understanding of the replacement characteristics and kinetic mechanism of CO2–CH4 hydrate has great significance for natural gas hydrate (NGH) exploitation. This paper presents a comprehensive overview on the research progress of kinetics on CH4 recovery from NGH by CO2 replacement, especially with CO2-containing mixed gas. The promoting effect of small molecule gas such as H2 and N2 on the replacement process of CO2–CH4 hydrate and its internal mechanism are deeply analyzed. Furthermore, based on the current conclusions obtained, the existing problems and future development directions of the CH4 recovery from NGH by CO2-containing gas mixture are pointed out.