Comparison Analysis on Model of Methane Adsorption Isotherms in Shales

Isothermal adsorption experiments of methane on Lower Cambrian Niutitang black shales from the south of Sichuan Basin at 35°C and 65 °C have been conducted. Five different adsorption models ( Langmuir, Freundlich, Langmuir-Freundlich, D-R and Toth adsorption equations) were used to fit the experimental data, a nd fitting degree of these models were investigated. The results showed that all these models fit the experimental data well, and the more parameters were used in thes e models, the better matching results could be obtained. The Toth and Langmuir-Freundlich equations with three parameters fit better than Langmuir, Freundlich and D- R equations which all had two parameters. The composition of shale was complex, resulting in energy heterogeneity of the adsorption sites on the surface of shale, whi ch affected the fiting results in low pressure, and Toth equation could describe methane adsorption in shales with heterogeneous surface very well.