Study on stress sensitivity of clayey silt hydrate-bearing sediments and its influence law on production

Marine clayey silt gas hydrate reservoirs are characterized by weak cementation and strong stress sensitivity. Accurate characterization of stress-dependent permeability under varying hydrate saturations is essential for reliable production prediction and development strategy optimization. Existing stress-sensitive permeability models fail to account for the heterogeneous spatial distribution of hydrates in porous media, leading to limited experimental reproducibility and non-trivial discrepancies in regression model fitting. Through integrated physical experiments and nuclear magnetic resonance imaging, this study systematically investigates permeability evolution in hydrate-bearing clayey silt sediments under stress conditions, reconstructs the three-dimensional hydrate distribution patterns, and develops an improved permeability model incorporating hydrate heterogeneity. The implemented model in TOUGH+Hydrate reveals critical insights into stress-sensitivity impacts on depressurization performance. Key results demonstrate an exponential permeability decline with increasing effective stress. The new model significantly improves fitting accuracy by reducing errors from 0.035 to 0.001 through explicit consideration of hydrate heterogeneity in the 2°C experiments. Numerical simulations highlight that stress-induced permeability reduction is a dominant, production-limiting factor across a range of operating pressures, reducing cumulative gas production by 58.4-81.3% compared to conventional models. The underlying mechanism is identified as the formation of a low-permeability zone just outside the dissociation front, which severely impedes pressure propagation and confines hydrate dissociation to near-wellbore regions.