A Novel Analytical Model of Gas-Water Relative Permeability in Hydrate-Bearing Sediments Under Creep

Summary As one of the critical seepage parameters, gas-water relative permeability (GWRP) governs gas-water behaviors. In the context of prolonged natural gas hydrate (NGH) extraction, creep characteristics of hydrate-bearing sediments (HBS) alter flow channels, resulting in a dynamic and nonlinear evolution of relative permeability. Therefore, it is crucial to accurately determine relative permeability during HBS creep. This investigation constructs an innovative GWRP model integrating HBS creep behaviors, pore morphology, occurrence modes of NGHs, and capillarity effects. The derived model is thoroughly verified through comparisons with available experimental data sets, the numerical models, and the classical analytical model. Additionally, a sensitivity analysis is performed using the proposed model, demonstrating its capability to accurately predict the GWRP evolution during HBS creep. Moreover, HBS creep behaviors under effective stress conditions not only induce the transformations between different modes of NGHs occurrence but also significantly reduce HBS permeability. For a given study case, when σ1 increases from 0 to 0.3 MPa, the gas phase (or liquid phase) effective permeability decreases by approximately 11.74% (or 15.24%). The proposed model not only deepens the understanding of GWRP evolution mechanisms but also offers practical insights for optimizing hydrate extraction strategies.