Measurement and modeling of the adsorption isotherms of CH and CH on shale samples.

CH and CH are two common components in shale gas. Adsorption isotherms of CH, CH, and their binary mixtures on shale samples are significant for understanding the fundamental mechanisms of shale gas storage and the recovery of shale resources from shale reservoirs. In this study, the thermogravimetric method is applied to obtain the adsorption isotherms of CH, CH and their binary mixtures on two typical shale core samples. A simplified local density theory/Peng-Robinson equation of state (SLD-PR EOS) model is then applied to calculate the adsorption of CH and CH on shale, and the efficiency of the SLD-PR EOS model is thus evaluated. The results show that CH exhibits a higher adsorption capacity than CH on shale samples, indicating the greater affinity of CH to organic shale. As the molar fraction of CH increases in the CH/CH mixtures, the adsorption capacity of the gas mixtures increases, indicating the preferential adsorption of CH on shale. Based on the predicted results from the SLD-PR EOS model, a reasonable agreement has been achieved with the measured adsorption isotherms of CH and CH, validating the reliability of the SLD-PR EOS model for predicting adsorption isotherms of CH and CH on shale samples. In addition, the SLD-PR EOS model is more accurate in predicting the adsorption of CH on shale than that of CH. This study is expected to inspire a new strategy for predicting the adsorption of hydrocarbons on shale and to provide a basic understanding of competitive adsorption of gas mixtures in shale reservoirs.