Numerical Investigation of the Deformation Characteristics of Hydrate-Bearing Sediments during Hydrate Extraction

The depressurization method is promising for the extraction of natural gas hydrates from marine sediments. Hydrate dissociation leads to degradation of the mechanical properties of hydrate-bearing sediments (HBSs). Understanding the deformation characteristics of HBSs is crucial for the safe extraction of natural gas hydrates. This study investigates the effects of initial hydrate saturation, hydrate morphology, depressurization amplitude, in situ stress, and hydrate dissociation rate on the deformation characteristics of HBSs using the discrete element method. The deformation characteristics of HBSs during depressurization and hydrate dissociation are analyzed from both macro- and microscopic perspectives. The presence of hydrates influences only the deformation evolution of HBSs, while the final volumetric strains of HBSs are similar under a given in situ stress and depressurization amplitude. The in situ stress and depressurization amplitude significantly affect the volumetric strain of HBSs, with the volumetric strain increasing as the in situ stress and depressurization amplitude rise. Hydrate morphology impacts the deformation characteristics of HBSs during depressurization and hydrate dissociation. The hydrate dissociation rate has a minimal effect on the deformation of HBSs when pore pressure is constant. These results enhance our understanding of the deformation characteristics of HBSs during hydrate extraction.