High-Pressure Sorption of Methane, Ethane, and Their Mixtures on Shales from Sichuan Basin, China

High-pressure sorption isotherms of CH4, C2H6, and their mixtures on shales from Sichuan Basin, China, were measured by a volumetric method. The sorption measurements for pure components were conducted at 40, 60, and 80 degrees C, with the pressure up to similar to 20 MPa. The binary sorption measurements were performed to similar to 11 MPa at 40 degrees C and similar to 16 MPa at 80 degrees C, and two feed gas compositions of C2H6 (10 and 20%) were studied. The excess sorption isotherms of pure components were fitted by the three-parameter Langmuir model, and the extended Langmuir (EL) model was used to predict the absolute sorption isotherms of binary mixtures. The sorption discrepancies of CH4/C2H6 were discussed, and the preferential sorption of C2H6 was quantitatively analyzed. As the temperature decreases, the excess sorption isotherm of C2H6 presents a more sharp increase and then a more rapid decrease. The excess sorption isotherms of C2H6 at 40 degrees C show significant differences with other CH4/C2H6 isotherms. In comparison to gas composition, the temperature has a more notable effect on binary excess sorption isotherms. C2H6 shows a stronger affinity than CH4, and its stronger affinity is less significant in the mixtures compared to the single component. The sorption selectivity presents a first increasing and later decreasing trend with the pressure. The presence of C2H6 mainly reduces the excess sorption of CH4 at a high pressure, and its effect at a low pressure is negligible.

Automated summary

High-pressure sorption isotherms were measured on shales from Sichuan Basin, China for CH4, C2H6, and their mixtures using a volumetric method. The temperature had a more notable effect on the binary excess sorption isotherms compared to gas composition. C2H6 showed stronger affinity than CH4, with its effect more significant at high pressures and less significant at low pressures.