Analysis on model fitting of adsorption isotherms in shales tested by volumetric method and gravimetric method

The adsorption isotherms test at different temperatures on 12 shale samples selected randomly was conducted using volumetric method and gravimetric method. Six different single-component fitting models (Freundlich,Langmuir, D-R,Langmuir-Freundlich,double Langmuir,Toth) were used to fit the experimental data,and their fitting degree was investigated. Considering different samples,temperature,equilibrium pressure and experimental methods,the results show that the fitting result order from good to badis:Langmuir-Freundlich,double Langmuir,Toth,D-R,Freundlich, and Langmuir. Among them,the Langmuir-Freundlich equation and double Langmuir equation could describe the curve most accurately under the condition of higher equilibrium pressure and lower experiment condition respectively.