Research On Adsorption Characteristics Of Multicomponent Shale Gas Of Longmaxi Formation In Yinin Region Sichuan Province

Selected the shale samples from Longmaxi formation in Yibin region Sichuan Province,geochemical properties and pore structure characteristics of shale samples were determined;Using volume method to detect the isothermal adsorption in shale samples under different proportions mixed gas.Discuss the characteristics of competitive adsorption and selection for multicomponents.Explained the the adsorption mechanism by thermodynamics.Geochemical properties showed that the total organic carbon content and clay minerals of shale samples were high,organic matter were rich and had high maturity.Samples contained large numbers of micro-mesopores,which provided considerable specific surface area.Clay mineral made the pore structures of shale samples more complicatedly and beneficial to the reservoir and adsorption of shale gas.The experiment results showed that the multi-component adsorption isothermals belonged to I type adsorption isotherm,which were more favorable for gas adsorption under low temperature and low pressure.In the different proportion of CH₄-CO₂,the adsorption capacity was affected by original CO₂.The experimental results of CH₄-C₂H₆,the total adsorption capacity was lower than the adsorption capacity of CH₄-CO₂,and the adsorption capacity of the three single component gases from large to small was CO₂>C₂H₆>CH₄.The volume ration of free phase and selectivity showed that CO₂ and C₂H₆ had the advantage in competitive adsorption,preferentially adsorbed on shale surface,and CH₄adsorption was relatively lagged behind.The parameters of the multi-component adsorption models were obtained from the single component adsorption models and the fitting results showed that the Langmuir multi-component adsorption model had better fitting effect.Isosteric heat of adsorption was positively related to the amount of adsorption.When the content of CO₂ in the two components was higher,the isosteric adsorption heat and the limit adsorption heat were higher.Meanwhile C₂H₆ occupied high energy adsorption sites and released a large amount of heat during the adsorption process,thus increasing the value of the equal amount of adsorption heat.