The influence of reservoir and exploitation parameters on production capacity of gas hydrate

Studying the effects of reservoir parameters and exploitation parameters on the production capacity of natural gas hydrate is helpful for locating mining site and choosing mining method. Using the geological parameters of Station SH7 in the Shenhu sea area of South China Sea as the background, the effects of reservoir parameters including reservoir pressure, reservoir temperature, reservoir porosity, hydrate saturation, reservoir permeability, and the permeabilities of upper and lower layers, as well as the exploitation parameters including depressurization amplitude, the length of depressurization well, and sand blockage (which is reflected by changing the permeability of grid surrounding well), on gas hydrate production capacity by depressurization were numerically simulated and systematically analyzed with TOUGH+HYDRATE software. Results show that first, the gas production increased obviously with the increase of reservoir permeability. The gas production increased relatively with increase in reservoir pressure and reservoir porosity, and with the decrease in permeability of upper and lower layers. The gas production increased to some degree with the increase of reservoir temperature. The gas production increased first and then decreased with the increase of saturation. Therefore, in practical work, it is suggested to choose preferentially the reservoir with high permeability, high porosity, high temperature, low permeability of the upper and lower layers, and moderate hydrate saturation. Secondly, the gas production increased obviously with the increase of the depressurization amplitude and the length of depressurization well but decreased significantly with the degree of sand blockage. Therefore, it is suggested to increase the depressurization degree and the length of production well, and to reduce the sand blockage for increasing the gas production. This study provided a reference for the selection and determination of the site and method of gas-hydrate mining in China in the future.