The replacement of CH4 by injecting CO2 in methane hydrates is a promising method for simultaneously allowing geologic CO2 sequestration and CH4 recovery. However, the carbon dioxide hydrate layer formed on the MH surface acts as a barrier, which causes the slow diffusivity of CO2. Therefore, in this study, we proposed using an operation of multi-depressurization to increase the diffusivity of CO2 and enhance the CH4 recovery in the CH4/CO2 replacement processes. The results proved that both the value of the methane replacement rate and the carbon dioxide storage rate increase significantly.
Keywords hydrate, CH4 recovery, CH4/CO2 replacement, multi-depressurization