Comparative analysis of the consolidation and shear behaviors of CH4 and CO2 hydrate-bearing silty sediments

The successful production trial in Ignik Sikumi located in Alaska North Slope showed the significant potential of applying the CH4-CO2 replacement method to natural hydrate production. The comparison on the mechanical behaviors of CH4 and CO2 hydrate-bearing sediments is the key factor in assessing the geomechanical stability of hydrate reservoirs before and after the CH4-CO2 replacement. Large amount of hydrates have been discovered in silty reservoirs. However, studies focusing on the mechanical behaviors of CH4 and CO2 hydrate-bearing silty sediments are rare to date. This paper reports the results of a comparative analysis of the mechanical behaviors, including the isotropic consolidation behaviors and stress-strain relationships of CH4 and CO2 hydrate-bearing silty sediments. The results show that the CH4 and CO2 hydrate-bearing silty sediments present similar compression and swelling indexes. Various hydrate saturation shows differential effects on the strength and stiffness of CH4 and CO2 hydrate-bearing silty sediments. In addition, CO2 hydrate-bearing silty sediments displays weaker contraction behaviors than that of CH4 hydrate-bearing silty sediments.