Abstract
Submarine methane-rich fluids migrating through geological conduits significantly influence gas hydrate production during depressurization. However, the coupled effects of methane, water, and heat delivered by these fluids on hydrate dissociation and methane recovery remain unclear. This study establishes a conceptual coupled numerical model of “pressure reduction–fluid response–reservoir evolution” based on reservoir parameters from Well W11 in the Shenhu area, South China Sea (SCS), and representative conduit characteristics. Hydrate dissociation and gas production are simulated under steady pressure reduction conditions with varying fluid invasion scenarios. Results show that the invasion of methane-rich fluid into gas hydrate systems exhibits a three-phase impact on gas production dynamics. Initially, the invasion has little effect on gas production; in the intermediate stage, it temporarily inhibits gas production; and under sustained invasion, it significantly enhances gas production. Limited water inflow with enhanced heat input promotes efficient hydrate-derived gas recovery. High methane flux enhances gas production while limiting hydrate dissociation. Excessive methane input may induce secondary hydrate formation, with the amount of newly formed hydrate exceeding that of the dissociated hydrate in the reservoir. A strong synergistic “1 + 1 > 2” effect occurs under low water or methane invasion, increasing gas output up to 4.3 times compared with a no-invasion case. These findings enhance understanding of dynamic hydrate exploitation systems and support the safe and efficient co-production of gas hydrates and associated deep gas.