Natural gas hydrates represent a significant strategic energy resource for the 21st century. However, hydrate dissociation during production can trigger reservoir instability, particularly when external thermal fluid injection is employed. Based on the geological conditions at the GMGS3-W18 site in the South China Sea, this study investigates the multiphysical coupling behavior during thermally stimulated hydrate dissociation using the fully coupled thermal-hydraulic-mechanical-chemical (THMC) simulator HydrateBiot. The analysis focuses on the effects of water injection rate and temperature on hydrate dissociation behavior, reservoir mechanical response, and energy efficiency. Simulation results indicate that the water injection rate and temperature are key parameters controlling the production performance. As the injection rate increases from 2 kg/s to 5 kg/s, the hydrate dissociation front advances over 60 m from the wellbore. Increasing the injection temperature from 30 to 90 °C significantly accelerates hydrate dissociation. Mechanically, the region near the injection well experiences a sharp reduction in effective stress and expansion. When the injection rate exceeds 3 kg/s, the stress path in this region instantly crosses the Mohr-Coulomb failure criterion, indicating a high shear failure risk. In contrast, the production well region develops a compression zone with increased effective stress due to depressurization. Energy efficiency ratio analysis suggests that to balance production performance and reservoir safety, an injection rate of 2–3 kg/s combined with a temperature of 60 °C is recommended. This strategy helps maintain reservoir stability, mitigates shear failure risk, and keeps the energy efficiency ratio (EER) above 1.5.
Li et al. (Tue,) studied this question.