Experimental study on the mechanical properties of sediments containing CH4 and CO2 hydrate mixtures

CH4-CO2 replacement method for extracting methane from hydrate-bearing sediments has attracted more and more attention due to its twin advantages: CH4 recovery and CO2 geologic sequestration. In this study, a series of triaxial tests were conducted on sediments containing CH4 and CO2 hydrate mixtures to prove the mechanical stability of CH4-CO2 replacement in permafrost-associated methane hydrate-bearing sediments. And a comparative analysis was made between the mixed hydrate- and pure CH4/CO2 hydrate-bearing sediments containing ice. The stress-strain curves, failure strength, initial yield modulus, shear strength and the effects of CO2 hydrate volume ratio, confining pressure, temperature and strain rate on the mechanical properties of mixed hydrate-bearing sediments containing ice were investigated. The experimental results indicated that CH4-CO2 replacement was conducive to the stability of the methane hydrate-bearing layers during gas production.