Numerical Study Of Gas Production From Methane Hydrate Reservoir By Depressurization

Natural gas hydrates is considered as a future energy because of its tremendous resources and high efficiency. At the moment much progress has been acquired in the fundamental researches of hydrates, but the researches of the development regular is still lagging.On the basic of survey and study of the numerical model of exploitation of gas hydrates both at home and abroad, and taking into account of the depressurization mechanism and characters of the thermodynamics and kinetics of the gas hydrates, this paper established a four-phase (gas, water, hydrates, ice), four-components (free methane, resolved methane, water, hydrates) mathematical model for gas hydrates reservoir of depressurization. We use implicit method to calculate pressure and explicit method to calculate saturation successively and then calculate temperature in implicit method.On the basic of the mathematical model, software of numerical simulation of hydrates of depressurization exploitation is developed. Using this software, analyzed the results of the experiment. By matching the simulation and experiment results, necessary parameters are obtained, and verified the accuracy of the software. Simulated the actual gas hydrates reservoir and analyzed the regular of gas production, and the distribution of pressure, temperature and saturation of the hydrates. On this basis, the sensitivity of the hydrates reservoir production of the affecting parameters is analyzed and the simulation results shows: the drop down index of permeability greatly infects the production; permeability anisotropy affects the distribution of the pressure and hydrates saturation in the reservoir; and permeability anisotropy is the same as index of hydrates decomposition rate, has no affects on the accumulation production of the gas well.