Adsorption Behavior Study of Shale Gas: Models and New Combination Approach

Abstract Comparison of different adsorption models in the application of shale reservoir is performed, adsorption capability of shale is reconstructed by the combination of pure mineral adsorption capability with adsorption potential theory. Results are tested by experimental study of specific shale samples in China. The research is based on the high pressure adsorption experiment of methane, in the same time X-ray diffraction experiment is performed to get the mineral information of the shale samples, which are taken from Lungmaxi formation in China. With the experiment, different adsorption models including monolayer Langmuir model, multilayer BET model and D-A model are used to match the data. Also, adsorption capability of pure minerals is combined by adsorption potential theory, which is used to study the contribution of different minerals on the total adsorption capability of shale. Results show that Langmuir curve fits can be used to describe the adsorption behavior of shale, but BET curve fits give more accurate results, D-A curve fits make the best match. The use of characteristic curve can provide further information of the adsorption behavior, by which the unknown isothermal data can be forecasted. The adsorption capability with combination of pure mineral through adsorption potential theory (according to the mineral composition of each sample) gives reasonable results to indicate the total adsorption capability of shale, which means the new approach to get the adsorption information is applicable if the mineral composition and adsorption capability of each mineral are known.