Numerical Simulation on the Production Law of Gas Hydrate Reservoir by Heat Generation Powders Thermal Stimulation Assisted Depressurization

Abstract Natural gas hydrates have abundant reserves and are considered as alternative energy sources. At present, the development of hydrates still faces problems of insufficient production capacity and low heat utilization efficiency. In this study, a method of using heat generation powders thermal stimulation assisted depressurization to extract hydrates (HPTS-DP) is proposed. This method is based on the in-situ heat release characteristics of heat generation powders to improve energy utilization efficiency. In this method, CaO is used as the heat generation powders, and its hydration heat release characteristics are considered to establish a thermal-hydraulic-mechanical-chemical coupling model for the HPTS-DP. Referring to the basic data of the second hydrate trial production well in the South China Sea, the production flow laws of HPTS-DP and DP mining methods for hydrate reservoirs were compared and analyzed. The results indicate that during the long mining cycle, the hydrate decomposition mode of the HPTS-DP method exhibits a mixture mode of piston type and non-piston type modes, expanding the decomposition area of hydrates. Compared to the DP method, the cumulative gas production of the HPTS-DP method increased by 61.43% and the water gas ratio decreased by 19.96% after a simulation period equivalent to 1 year. The influence range of heat generation powders on production capacity was analyzed. When the range of CaO action is 3 m, 5 m, 8 m, and 10 m, the cumulative gas production increased by 4.20%, 14.33%, 35.01%, and 61.43%, respectively. Expanding the injection distance of heat generation powders as much as possible has become a potential research direction. The research results can provide theoretical support for the efficient development of gas hydrate reservoirs.