Synergistic exploitation of gas hydrates through surface seawater injection coupled with depressurization: Application and optimization in the South China Sea

• Warm seawater injection coupled with depressurization enhances long-term gas hydrate production by supplying additional heat during the decomposition phase. • Optimal injection rates and depths are critical: excessive rates impede depressurization, while appropriate depths balance thermal supplementation and pressure gradient. • A 'depressurization-driven sensible-heat supply window' identifies the optimal timing for seawater injection, with 170 days of initial depressurization being optimal in the South China Sea study area. • The integrated approach leverages renewable thermal energy, offering a sustainable and economically viable strategy for commercial-scale hydrate exploitation.