Instability Analysis of Methane Hydrate Bearing Soil Considering Dissociation

Methane hydrate is the potential energy resources for natural gas, and naturally exists in both permafrost region and in the deep seabed ground. In Japan, we have found that a large amount of MH exist in the seafloor, especially in the Nankai Trough area, and we are attempting to extract methane gas from the MH contained ground by dissociating hydrates. It has been recognized that MH bearing sediments may undergo instability due to the hydrates dissociation. Wu and Grozic (2008) indicated that dissociation of even a small percentage of gas hydrates will lead to failure from experimental evidence. Kimoto et al. (2010) developed a numerical simulator for deformation of soil containing methane hydrates due to the dissociation of gas hydrates based on the chemo-thermo-mechanically coupled mixture theory. From the numerical results, they indicated that ground deformation localizes around the dissociated area. For unsaturated materials, In order to investigate a stability of ground during the dissociation of methane hydrate, we have conducted a linear stability analysis of a chemo-thermo-mechanically coupled system considering dissociation.