LAUSR

Abstract The replacement method by CO 2 is regarded as a new approach to natural gas hydrate (NGH) exploitation method, by which methane production and carbon dioxide sequestration might be obtained simultaneously. In this study, CO 2 was used to recover CH 4 from hydrate reservoirs at different temperatures and pressures. During the CO 2 CH 4 recovery process, the pressure was selected from 2.1 to 3.4 MPa, and the temperature ranged from 274.2 to 281.2 K. Calculating the fugacity differences between the gas phase and the hydrate phase for CO 2 and CH 4 at different conditions, it has found rising pressure was positive for hydrates formation process that was helpful for the improvement of CH 4 recovery rate. Rising temperature promoted the trend of CH 4 hydrate decomposition for the whole process of CO 2 CH 4 replacement. The highest recovery rate was 46.6 % at 3.4 MPa 281.2 K for CO 2 CH 4 replacement reaction in this work.