Investigation of methane sorption of overmature Wufeng-Longmaxi shale in the Jiaoshiba area, Eastern Sichuan Basin, China

Both the supercritical Dubinin-Radushkevich (SDR)-based and the Langmuir-based excess adsorption models are used to fit measured adsorption isotherms. Most of the methane adsorption phase density values fitted by both models are greater than the density of liquid phase methane at its boiling points, 424 mg/cm3. For the Langmuir-based model, a fixed adsorption density of 424, or 373 mg/cm3 was used in fitting the experimental data, which will result in higher maximum adsorbed capacity values. For the SDR-based model, maxima adsorbed capacity values remain stable and have nothing to do with sorption phase density.