Abstract:

Shale gas is an unconventional natural gas reservoir that exists as adsorption, free and dissolved states. Adsorption is the main occurrence state of shale gas. It is very important to study the properties of shale gas adsorption and desorption for exploiting shale gas reservoir. Shale samples were selected from marine shale region in Jingmen, Hubei Province and Sichuan Province. A series of analyses are conducted to obtain the basic properties of shale, and the results indicate that the high degree of organic carbon content and organic matter maturity of the shale samples. MSB magnetic suspension balance adsorption instrument is used to proceed isothermal desorption experiments. The results show that the volume of desorption is low and nearly keeps no change under pressure of 33 MPa to 10 MPa. It increases rapidly when the pressure falls to the range of 10 MPa. The pressure range of 10 MPa to 0.5 MPa is the main period for desorbing the adsorption methane. Adsorption potential theory can be used to estimate the desorption status and desorption strength of shale samples. The larger adsorption potential leads to the more difficult desorption.

Key words: marine shale, isothermal desorption, desorption velocity, desorption efficiency, adsorption potential