Methane hydrate, a form of clean energy also called flammable ice, has drawn global interest as an alternative energy resource of traditional fossil energy. The rate of gas production using depressurization depends on the effective permeability of the formations, which is controlled by not only hydrate saturation but also the porosity change of the host sediment. A decrease in pore pressure leads to an increase in the effective stress and the collapse of the bonded structure made by the hydrate resulting in the volume contraction and permeability reduction. On the other hand, the pore pressure drop induces hydrate dissociation, which increases the volume of the pore and permeability. In this study, we conducted a series of experiments to measure the effective permeability of HBSs with different hydrate saturation. The relationship between porosity, hydrate saturation and effective permeability is analyzed. Combining the consolidation analysis, we proposed a new method to estimate the change in effective permeability of hydrate-bearing sands during dissociation by depressurization.
Keywords permeability, soil compaction, hydrate dissociation, effective stress