Experimental Study And Numerical Simulation Of Gas Production From Natural Gas Hydrate

Natural gas hydrate is an important product as an alternative to fossil fuels in the future. With its advantages like widely distributed, a huge amount of resources, high energy density, and pollution-free, many countries in the world are highly concerned about it. Basic researches of natural gas hydrate will provide a theoretical basis and technical support for its commercial exploitation in the future.In this paper, we simulated the mode of occurrence and temperature and pressure conditions of natural gas hydrate in subsea, studied the production of it by the experiment in a three-dimensional porous medium model filled with quartz sand in the laboratory. This process is analyzed to reveal the impact of hydrate saturation, back pressure, porous medium permeability on system temperature, pressure, and gas production rate and cumulative gas production. According to the experimental results, when all other factors being equal, low back pressure or high hydrate saturation lead to long high-yield gas rate stage, high cumulative gas production and ultimate recovery. High porous medium permeability leads to high gas production rate, but has nothing to do with the cumulative gas production and ultimate recovery. And if back pressure is too small, and then gas hydrate will formation again. On the basis of gas production by decompression, we studied gas production by thermal stimulation by the experiment. We designed two schemes, continuous heat injection and cyclic heat injection. According to the results, both schemes lead to low gas production rate and low overall efficiency, but thermal stimulation can do as an adjunct to other methods like decompression. Besides, compare with continuous heat injection, cyclic heat injection lead to more stable on gas production rate and cumulative gas production even more.Based on experiments of gas production by decompression, we used conventional reservoir numerical simulation software to simulate gas production, and verified its results use experimental data. Further more, we applied the simulation model to a conceptual gas hydrate reservoir model. Aim at the process of gas production, we contrasted conceptual gas hydrate reservoir with conventional gas reservoir and low permeability gas reservoir, made recoverability evaluation. According to the results of simulations, the conceptual gas hydrate reservoir had a long high-yielding period, its ultimate recovery is comparable to natural gas reservoir. So there is a very good prospect for gas production from natural gas hydrate.