Effects of soaking process on CH4-CO2 replacement efficiency for hydrate-bearing sediments

CH4-CO2 replacement method has the advantages of sequestering carbon dioxide and sediment stability compared to other methods such as depressurization and thermal stimulation. However, the production efficiency using CH4-CO2 replacement method is lower than any other method. In this study, effects of soaking process on CH4-CO2 replacement efficiency were determined. The soaking process was the time to close all valves for the enhancement of CH4-CO2 reaction which resulted in the long reaction time between the injected CO2 and methane hydrate and consisted of the 1st and the 2nd production with soaking time after dynamic replacement. Results showed that total replacement efficiency increased with increasing number of soaking processes and more soaking time. The increasing rate of replacement efficiency in the first soaking process was higher than that in the second process. However, the soaking process showed the disadvantage that the total production time increased with increasing soaking time and process, which could result in the production cost increase. Therefore, appropriate soaking time and number of soaking processes are required to improve the replacement efficiency considering production cost.