Experimental study on the gas phase permeability of methane hydrate-bearing clayey sediments

The permeability of hydrate-bearing sediment is one of the important parameters that influences the gas production rate of the hydrate reservoirs. In this study, a series of experiments were performed to investigate the gas phase permeability of kaolin clay with different hydrate saturations (0%, 2.59%, 4.23%, 11.44%, 16.84%, 22.91%, 27.57%, 28.85%, 34.16%, and 40.46%) at effective axial stresses of 1 MPa, 3 MPa. The results indicated that the gas phase permeability of the kaolin clay firstly decreases and then increases with the increase of hydrate saturation, due to the effect of blockage of hydrate particles and the increase of pores in inter-aggregate zones during methane hydrate formation. And there is a critical hydrate saturation that the gas phase permeability of hydrate-bearing clayey specimen equals to that of pure clayey specimen. Furthermore, the gas phase permeability of hydrate-bearing clayey specimens under high effective axial stresses is less than that under low effective axial stresses, due to the compaction of pore spaces and pore throats. And the stress sensitive index clearly increases with the increase of hydrate saturation, and the increase tendency become gentle when the hydrate saturation higher than 30%.