Dynamic Study On Buck Production With Natural Gas Hydrate Under Multi-field Coupling

China is rich in natural gas hydrate reserves,and natural gas hydrate is an important energy object for China's future development and utilization.In 2017,China successfully carried out gas hydrate decompression testing and production in the South China Sea,becoming the first country in the world to successfully complete the sea trial production,marking China's leading position in the development and research of natural gas hydrates in the sea area.At present,most of the simulations of gas hydrate depressurization are based on laboratory simulations.Based on the full investigation of domestic and foreign literature,this paper considers the kinetics of hydrate decomposition and the changes in pressure and temperature during mining,and establishes a gas hydrate mine The actual multi-field coupling mathematics model for buckling in field mining is selected.The cylindrical coordinate system is selected,and the radial non-uniform and longitudinal uniform grid system is adopted.The implicit and explicit solution methods are respectively adopted by the finite difference method to obtain different mining methods.The formation pressure,temperature and distribution characteristics of each phase saturation,as well as the parameter sensitivity analysis of pressure and temperature were taken.In addition,although natural gas hydrate is a relatively clean energy source,considering the leakage of methane gas during the mining process has a very serious greenhouse effect,this paper also established a mathematical model for the leakage of methane under the seabed in the process of gas hydrate production.The model was solved to obtain the characteristics of the concentration change of the seabed methane leakage,and the sensitivity of the parameters was analyzed.Finally,the methane leakage mathematical model established in this paper was applied to the monitoring data of the measured methane leakage concentration in a certain sea area of China.The peak concentration of methane leakage and the seawater flow rate were obtained,and the gas hydrates of the same sea area and the same kind were collected.Pressure mining and its impact on the environment during mining have important guiding significance.