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Dissociation‐Induced Deformation of Hydrate‐Bearing Silty Sand During Depressurization Under Constant Effective Stress

Hydrate dissociation‐induced deformation plays a crucial role in reservoir stability during the exploitation of natural gas hydrates. During the depressurization‐induced dissociation of pore hydrate, both hydrate saturation loss and effective stress rise tend to enhance the deformation. Previous studies have not been able to distinguish between deformations caused by these two factors. In this study, triaxial tests were conducted on carbon dioxide hydrate‐bearing sediments with constant effective stress but continuously decreasing gas pressure. Another stepwise depressurization test was conducted as a supplement to monitor the variation of hydrate saturation. The results show that the partial dissociation of hydrate along with the change of pressure‐temperature state cause deformation within the hydrate‐stability field. Effective confining pressure compresses the dissociating sediment under isotropic stress but restrains compression under constant deviatoric stress. Deviatoric stress enhances the deformation during axial loading, creep and depressurization‐induced dissociation.