Molecular dynamics simulation of existing state of methane in graphite slit special-shaped holes

Shale gas mainly exists as a state of absorbed and free in the pores of shale. The multiformity of structures of organic pores makes it difference in the existing state of shale gas. The graphite model was used as shale organic matrix in Materials Studio and two types of holes (rectangle and triangle) in graphite slit were built. Under the condition of 38 MPa and 345 K,the methane densities in different holes and different locations were calculated and the absorption state of methane was studied by using molecular dynamic method. The maximum density of rectangular holes was high up to 0. 599 g / cm3 and the value of density was high up to 0. 456 g / cm3 in the bottom of the triangle vertex angle, where the densities weretion function in pore was higher than the interface of slit. Finally,the shale samples collected in the field were imaged by scan electron microscope,and then the organic matter boundary can be identified clearly in the SEM images. Then the first and second absorbed layers were outlined in the image of the studied area. Based on the simulation results of density distributions,the possible shale gas content was calculated. above or close to the density of liquid methane. At the same time,the value of radial distribu