Molecular Simulation Of Adsorption Behaviors Of Shale Gas In Kerogen

Shale gas adsorption characteristics are of significance for high efficiency shale gas development.The model was built according to molecular structure of three types of kerogen.The adsorption behaviors of CH₄ in three types of kerogen were investigated by by Grand canonical Monte Carlo?GCMC?and Molecular Dynamic?MD?methods.We validated the models.On this basis,the effects of the temperature,geothermal gradient,atomic composition,and the specific surface area of the kerogen on the adsorption of methane were discussed.The microscopic adsorption mechanism of methane in kerogen was revealed.Results show that:The adsorption amount of the three kinds of kerogen in ascending order is:type I<type II<type III.The chemical structure of kerogen significantly influences its adsorption amount of methane:kerogens with more aromatic hydrocarbon and cyclane have a stronger affinity for methane,and C and S atoms significantly influences the adsorption of kerogen to methane.As temperature increases,the average isosteric adsorption heat of methane decreases,and it is always less than 42 kJ/mol,indicating that this adsorption is physical adsorption.At the same depth,the smaller the geothermal gradient is,the more methane adsorption.In addition,the adsorption amount of methane has a linear relationship with the specific surface area of kerogen.The microscopic adsorption mechanism of methane in the kerogen was studied from the molecular point of view,in order to provide theoretical support for the exploration and development of shale gas.