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

Abstract

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.