Investigation of variation in shale gas adsorption capacity with burial depth: Insights from the adsorption potential theory

In this study, the Polanyi theory was applied to investigate variation in shale gas adsorption capacity with burial depth. Analyses were implemented on background data of two shale samples with respective TOC contents of 4.00% and 4.51% TOC, accompanied by combination of the Polanyi theory and isothermal adsorption parameters. Shale gas adsorption capacity was found to first increase and then decrease as the burial depth grew, and the burial depth corresponding to the maximum adsorption capacity was basically constant within the study area. Specifically, pressure coefficient had the largest impact on the minimum adsorption potential, reaching 1.721 mol/kJ, while the ground temperature gradient was the most influential factor on the burial depth corresponding to the maximum adsorption capacity, reaching 1080 m. When the burial depth was shallower than 3200 m, the pressure coefficient dominated, whereas in deeper parts, the ground temperature gradient became dominant.