Deformation characteristics of methane hydrate-bearing clayey and sandy sediments during depressurization dissociation

Natural gas hydrate, a promising new energy, has been widely concerned from the past decades. Significant experimental efforts have been made to explore the mechanical characteristics of hydrate-bearing clayey sedi-ment under stable conditions, however, few studies focus on the creep characteristics of it during the dissociation process, which is closer to the actual condition of the reservoir. This study shows the triaxial creep test results of methane hydrate-bearing clayey sediment with the depressurization dissociation method, and the methane hydrate-bearing sandy sediments are added for comparison. The results show that in the creep process: (1) the depressurization has little effect on axial strain but causes the increase of the volumetric strain and the reduction of equivalent Poisson's ratio; (2) the number of depressurization times has no obvious effect on the total set-tlement and gas production rate during the depressurization process, the gas production rate is mainly deter-mined by the pore pressure; (3) the gas production rate of hydrate-bearing clayey sediments decreases during the depressurization process, while the hydrate-bearing sandy sediments show an opposite trend; (4) higher stress level causes a great increase of the axial strain, volumetric strain and equivalent Poisson's ratio, while it causes a slight increase of the gas production rate.

Automated summary

Natural gas hydrate, as a promising new energy, has attracted wide attention in the past decades. Experimental efforts have been made to explore the mechanical characteristics of hydrate-bearing clayey sediment under stable conditions, but few studies focus on its creep characteristics during the dissociation process. This study presents triaxial creep test results of methane hydrate-bearing clayey sediment using the depressurization dissociation method, with methane hydrate-bearing sandy sediments added for comparison. The results show that depressurization has little effect on axial strain but increases volumetric strain and reduces equivalent Poisson's ratio.