Recovering methane from quartz sand-bearing hydrate with gaseous CO2

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 CO2-CH4 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 CO2-CH4 replacement. The highest recovery rate was 46.6 % at 3.4 MPa 281.2 K for CO2-CH4 replacement reaction in this work. (C) 2017 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.