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

Abstract

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 °C, with the pressure up to ∼20 MPa. The binary sorption measurements were performed to ∼11 MPa at 40 °C and ∼16 MPa at 80 °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 °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.