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 ob-tained, the existing problems and future development directions of the CH4 recovery from NGH by CO2-con-taining gas mixture are pointed out.