Simulation And Numerical Modeling Research On Depressurization And Heat Injection Exploitation Of Natural Gas Hydrate

Natural gas hydrate mainly distributed in the high latitude permafrost and submarine sediments.With the exhaustion of conventional fossil fuels like coal,oil,and natural gas,natural gas hydrate is considered to be an important energy in the future.The study of gas hydrate exploitation helps to develop the natural gas hydrate resources and alleviate the energy crisis.In this paper,the depressurization and heat injection exploration of natural gas hydrate is emulated by TOUGH+HYDRATE software platform.Under the condition of depressurization,four different bottom hole pressure(0.75MPa?1.50MPa?2.25MPa?3.00MPa)are considered;under the condition of depressurization and heat injection exploitation,four different heat injection temperature(40??50??60??70?)and four different heat injection rate are considered.Gas recovery velocity,the cumulative gas volume,hydrate consumption,the residual gas volume,gas water ratio and other gas production performance index are analyzed.The evolution regulations of the factors including the spatial distribution of pressure,temperature,hydrate saturation,liquid saturation,gas saturation with time and those factors in different bottom hole pressure,heat injection temperature,heat injection rate are researched deeply.Under the condition of depressurization,the cumulative gas volume increases with the decrease of bottom hole pressure.In 1200 days production period,the influence of bottom hole pressure is small due to constant temperature constant pressure at overburden and underburden.The area of gas hydrate decomposition is spherical and the radius is only about 3.5m.Under the condition of depressurization and heat injection exploitation,the cumulative gas volume increases with the rise of heat injection temperature and heat injection rate,the cumulative gas volume of depressurization and heat injection exploitation is 20 times more than depressurization.The area of gas hydrate decomposition is irregular cylindrical and the radius is about 10 m in 1200 days production period.Compared with the increasing heat injection temperature,when increasing the same injection heat,changing the heat injection rate can be better than changing the heat injection temperature.