A granular thermodynamic constitutive model considering THMC coupling effect for hydrate-bearing sediment

Abstract

The interaction among mechanical, hydraulic, and temperature fields plays a crucial role in determining gas production efficiency and reservoir mechanical response. Considering particle rearrangement and cementation degradation effect, this study establishes a thermodynamic model that couples thermal, hydraulic, mechanical, and chemical fields (THMC) for hydrate-bearing sediments. For the proposed model, the mechanical field incorporates pore pressure and cementation terms, the hydraulic field considers the porosity, volumetric strain, and thermal driving effect, and the thermal field couples heat conduction, heat convection, and energy dissipation from hydrate dissociation. Furthermore, gas/liquid seepage rate and temperature conservation equation are not introduced as assumptions but are inferred from thermodynamic identities. Numerical simulations are conducted to investigate the physical significance of the three coupling elements and the mechanism of crucial parameters influencing gas production efficiency and reservoir mechanical response. The proposed model is simulated and validated at varying hydrate saturation levels and depressurization pressures. The modeling outcomes indicate that the theoretical model can accurately anticipate mechanical responses, gas production efficiency, and temperature variations during the hydrate consolidation and dissociation process.