Impacts of particle size distribution on the permeability of hydrate-bearing sediments using a DEM-PNM approach

The permeability of hydrate-bearing sediments governs the efficiency and economic feasibility of gas production from natural hydrate reservoirs. Recent characterizations of natural hydrate-bearing sediments show a wide range of particle size distributions of host sediments. However, the role of particle size distribution on the permeability evolution of hydrate-bearing sediments during gas production has not been explored. This study deploys a joint Discrete Element Method and Pore Network Modeling (DEM-PNM) approach to investigate the impact of particle size on the effective and relative permeability of hydrate-bearing sediments. The results show that flow tortuosity increases and effective permeability decreases with increasing uniformity coefficient Cu of the sediments. Regardless of hydrate pore habits, i.e., grain coating or pore filling, a larger uniformity coefficient Cu results in a slower permeability reduction with increasing hydrate saturation. The results also highlight that the relative permeability to water and gas of hydrate-bearing sediments exhibits complex responses to sediment's uniformity coefficient, depending on hydrate pore habits. This study bridges the relationship among particle features, physically representative pore structures, and flow parameters using novel grain-based pore-scale simulations.