Research progress and scientific challenges in permeability evolution of hydrate bearing sediments

Natural gas hydrate production involves complex mass/heat transfer, phase transformation, and multiphase seepage processes, where permeability critically influences exploitation efficiency and sediment stability. This review summarizes progress in permeability evolution in hydrate-bearing sediments, covering: multiphase seepage theories involving absolute and relative permeability models; pore-scale methods, including Lattice Boltzmann, Pore Network models, CFD simulations, and microfluidic experiments, for investigating the effects of hydrate morphology and pore heterogeneity; core-scale experiments, such as seepage tests and X-ray CT, for quantifying permeability changes with hydrate saturation and stress sensitivity; site-scale scenarios involving pilot tests and numerical models are challenged by fluid migration prediction and reservoir stability. Key findings show hydrate dissociation induces dynamic pore structure changes and complex multiphase interactions, with existing models oversimplifying heterogeneous pore structures and hydrate distributions. Critical research gaps include: inadequate characterization of pore structure evolution during hydrate nucleation/dissociation; unclear gas-water flow mechanisms in deformable sediments; lack of multiscale correlation and coupled modeling for permeability-stress-phase change interactions. Addressing these offers critical insights for optimizing extraction, reducing energy use, and ensuring reservoir stability, enabling safe and efficient exploitation of natural gas hydrates as a strategic clean energy resource.