A Review of Multiscale Mechanics and Pore-Scale Flow in Natural Gas Hydrate-Bearing Sediments

Natural gas hydrates, as a promising clean energy resource with abundant reserves, face critical challenges in commercial exploitation due to thermo-hydro-mechanical (THM) coupling effects and formation stability concerns. This paper reviews recent advances in multiscale investigations of hydrate-bearing sediments, focusing on their mechanical responses and fluid flow behavior within porous media. Key challenges include: maintaining the integrity of core samples during recovery; limitations in pore-scale imaging and simulation caused by sample accessibility and computational constraints; complex fluid flow mechanisms in clay-rich and silty layers; and uncertainties associated with boundary conditions and phase change simplifications in coupled THM simulations. To address these issues, a multiscale research framework is recommended—integrating high-resolution imaging with molecular dynamics simulations, standardizing high-pressure in-situ core sampling and permeability testing procedures, and exploring reservoir–wellbore interaction and failure mechanisms. Future research should prioritize breakthroughs in microstructural characterization, scale-bridging constitutive modeling, and multiphysics coupling techniques to support the safe and efficient development of gas hydrate resources.