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Modeling of Methane Adsorption on Organic–Rich Shales
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 78th EAGE Conference and Exhibition 2016, May 2016, Volume 2016, p.1 - 5
Abstract
Recovery of gas from organic–rich shales has become a focus for resource development worldwide. Excess adsorption isotherms of methane at 35 , 50 , and 65 and pressure up to 12 MPa were measured on Lower Cambrian shales from Sichuan Basin of China. Classic adsorption models (Langmuir, Freundlich, and Dubinin–Astakhov equations) had been applied to model the experimental data, and tested their validity in the methane–shale systems. Both the Langmuir and Dubinin–Astakhov (D–A) equations are adequate for the adsorption data, but the D–A equation based on potential theory is found to be superior.
The assumption of energetically homogeneous surface in the Langmuir equation is not appropriate for shale, and Langmuir equation cannot satisfactorily match the volume adsorbed in low pressure (< 2MPa). All these subcritical models cannot describe supercritical adsorption data at high pressure (> 10 MPa), though no maximum was observed for the excess adsorption isotherms in the experimental pressure range.