The geochemical, pore development and water-bearing characteristics of deep and ultra-deep marine shales and their effects on gas content: New implications from the shales of the first Lower Cambrian high-yield gas well (Z201) in China

作者：Hai-Tao Gao, Peng Cheng, Wei Wu, Chao Luo, Liang Xu, Tengfei Li, Haifeng Gai, Hui Tian · 发表于：Petroleum Science · 年份：2025 · DOI：10.1016/j.petsci.2025.02.011 · 被引用次数：6 · 研究领域：Hydrocarbon exploration and reservoir analysis、Methane Hydrates and Related Phenomena、Geological Studies and Exploration

The Lower Cambrian shales in the Sichuan Basin are considered one of the most promising shale gas resources in China. However, large-scale commercial development has not been achieved due to the relatively low and significantly variable gas contents of the drilled shales. Excitingly, the first major breakthrough in deep and ultra-deep Lower Cambrian shale gas was made recently in the well Z201 in the southern Sichuan Basin, with a gas yield exceeding 73 × 10 4 m 3 /d. The success of well Z201 provides a favorable geological case to reveal the distinct enrichment mechanism of deep and ultra-deep Lower Cambrian shale gas. In this study, at drilling site of well Z201, fresh shale core samples with different gas-in-place contents were collected, and their geochemical, pore development and water-bearing characteristics were analyzed systematically. The results showed that the Z201 organic-rich shales reached an overmature stage, with an average Raman maturity of 3.70%. The Z201 shales with high gas-in-place contents are mainly located in the Qiongzhusi 1 2 section and the upper Qiongzhusi 1 1 section, with an average gas-in-place content of 10.08 cm 3 /g. Compared to the shales with low gas-in-place contents, the shales with high gas-in-place contents exhibit higher total organic carbon contents, greater porosities, and lower water saturations, providing more effective pore spaces for shale gas enrichment. The effective pore structures of the deep and ultra-deep Lower Cambrian sha...