Gas-Bearing Characteristics of Permian Shales in Hongxing Area, Sichuan Basin, China: A Comprehensive Evaluation and Comparison Using Multiple Methods

In situ gas content and adsorbed gas ratio are the key parameters for shale gas content evaluation, and they can provide important references for the selection of development target areas and optimization of later development strategies. As a new formation for shale gas exploration and development, the gas content and adsorbed gas ratio of the Permian in the Hongxing area are not clear, which limits further development work. In this study, five shale samples from the Wujiaping Formation in the Hongxing area of the Sichuan Basin were used for sealing and desorption experiments, and four methods, namely, the USBM method, the polynomial method, the Amoco method, and the CIF method, were used to evaluate the gas content of the shale, and the results of the CIF method were found to be more accurate in comparison. The in situ gas content of Permian shales in the Hongxing area ranged from 5.38 to 13.36 cm3/g, with an average value of 8.30 cm3/g, and the ratio of adsorbed gas ranged from 45.24 to 74.67%, with an average value of 54.9%. Comparison with other typical shale and coal formations in several sedimentary basins in China shows that the in situ gas content and adsorbed gas ratio of Wujiaping shale are higher than those of Longmaxi shale in the Sichuan Basin and Shahezi shale in the Songliao Basin but lower than those of Shanxi and Taiyuan coal in the Qinshui Basin. The Wujiaping shale in the study area has unique gas-bearing characteristics; the high in situ gas content shows its good resource potential, but the high adsorbed gas ratio puts forward higher technical requirements for the efficient development of this resource.