Enhancing real-time gas production from muddy methane hydrate reservoirs: The impact of optimal production pressure

The dynamic optimization of the depressurization strategy, especially production pressure, is very important to improve the exploitation efficiency of methane hydrate reservoirs for enhancing gas recovery. Previous studies lack specific conclusions on quantifying the optimal adjustment and multi-parameter sensitivity analysis of production pressure in hydrate reservoirs. Therefore, 10 hydrate cores with hydrate saturations (28.9 %∼44.6 %) using South China Sea soil within a core holder are remolded. The results show that there is an optimal production pressure during depressurization, which yields the maximum production rate. Compared to other gas production pressures (0∼7 MPa), the gas flow rate is increased by 0.015 ml/s at the optimal gas production pressure, which is an increase of almost 59 %. Meanwhile, combined with the permeability equation, gas production flow curves with correlation coefficients distribution between 0.91 and 0.97 are proposed. The logical reasoning and calculation formulae for the optimal gas production pressure under different in situ conditions are given. Finally, combined with an orthogonal experimental design, absolute permeability, and gas source pressure are prioritized parameters for obtaining maximum production rate and optimal production pressure, respectively. This study provides important theoretical guidance for dynamically optimizing the gas production pressure to improve the gas production efficiency.