Particle-scale study of the mechanical properties of sandy hydrate-bearing sediments using DEM combined with CT images

Natural gas hydrate (NGH) is a promising clean energy source, understanding the mechanical properties of hydrate-bearing sediments (HBS) is hindered by the heterogeneous distribution of hydrates. While existing studies have explored sediment behavior, the effects of heterogeneous hydrate distribution and hydrate dissociation on HBS mechanics remain insufficiently addressed, limiting accurate prediction of reservoir deformation and NGH exploitation. In this study, the heterogeneous hydrate distribution was obtained based on X-ray computed tomography (CT) image. Heterogeneous HBS Digital cores' modeling and numerical biaxial compression experiments were conducted by the discrete element method (DEM). Hydrate dissociation was also considered, with particular attention to the effect of different dissociation degrees on the heterogeneous hydrate distribution HBS, including anisotropy, particle behaviour and mechanical property evolution. The results reveal that: 1) shear bands and particle rotation occur mainly in low hydrate saturation regions; 2) high hydrate saturation zones are crucial for the sediment's load-bearing capacity during shearing; and 3) as hydrate dissociation increases, the strength and stiffness of HBS decrease, fewer particles rotate, and anisotropy diminishes. These findings underscore the importance of considering hydrate distribution and dissociation effects in future HBS modeling, with broader implications for the safety and design of gas hydrate extraction.