Recovering methane from quartz sand-bearing hydrate with gaseous CO_2

The replacement method by CO₂ 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, CO₂ was used to recover CH₄ from hydrate reservoirs at different temperatures and pressures. During the CO₂CH₄ 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 CO₂ and CH₄ at different conditions, it has found rising pressure was positive for hydrates formation process that was helpful for the improvement of CH₄ recovery rate. Rising temperature promoted the trend of CH₄ hydrate decomposition for the whole process of CO₂CH₄ replacement. The highest recovery rate was 46.6 % at 3.4 MPa 281.2 K for CO₂CH₄ replacement reaction in this work.