Micromechanical Analysis of Methane Hydrate-Bearing Sediments During Gas Extraction Considering Hydrate Dissociation and Particle Breakage

With the growing interest in methane hydrate exploitation, numerous studies have been focusing on methane hydrate-bearing sediments (HBS). Depressurization is recognized as an effective method for gas extraction from HBS. However, the microscale mechanical behavior of HBS during depressurization remains poorly understood. In this study, a pressure-dependent hydrate dissociation chemical model is coupled with discrete element method (DEM) simulations, and irregular particle breakage is incorporated via a particle breakage model. The coupled DEM framework reproduces both hydrate dissociation and particle breakage. Prior to depressurization, the presence of hydrate significantly increases the strength and stiffness of sediments. During depressurization, the hydrate dissociates and the sediment skeleton exhibits an increasing contact coordination number, while contact anisotropy remains unchanged. Upon complete hydrate dissociation, the mechanical response aligns with that of pure sediments. However, under increasing stress during depressurization, particle breakage becomes evident, leading to significantly larger volumetric contraction compared to cases without particle breakage. The extent of particle breakage in HBS is influenced by the hydrate saturation and distribution. These findings underscore the critical role of particle breakage in hydrate exploitation, highlighting its impact on sediment deformation and mechanical stability.