Impact of Layered Heterogeneity on Hydrate Dissociation Dynamics and Fluid Production Behavior of Hydrate-Bearing Sediments

Natural gas hydrates have received increasing global attention as a widely distributed unconventional natural gas resource. While most laboratory studies have used homogeneous sediments to synthesize hydrate-bearing sediments (HBS), field explorations often reveal significant heterogeneity in the sediment properties. This work experimentally investigated the impact of layered heterogeneity in sediment on the hydrate dissociation dynamics and fluid production behavior. The results suggest that within the permeability range studied in this work, the layered heterogeneity of sediment permeability has a limited effect on the heat and mass transfer between adjacent layers when a vertical production well is employed, as fluid production predominantly occurs in the radial direction within each layer. Intermittent water production was observed during the constant-pressure production stage, except in scenarios where a fine sand middle layer was present. Additionally, the layered heterogeneity of the sediment porosity may result in a more heterogeneous hydrate distribution, leading to prolonged low-temperature periods during hydrate decomposition in layers with higher initial porosity. The findings of this work could enhance our understanding of how layered heterogeneity in sediment influences the hydrate dissociation dynamics and fluid production behavior.