A new type of unconventional gas reservoir from the nodular limestones of the Middle Permian Maokou Formation in the south‐eastern Sichuan Basin, south‐west China

作者：Ang Li, Xuanlong Shan, Kaiping Luo, Fengxun Li, Jinning Peng, Siyuan Su, Wenlei Pan, Mo Deng · 发表于：Geological Journal · 年份：2021 · DOI：10.1002/gj.4250 · 被引用次数：5 · 研究领域：Hydrocarbon exploration and reservoir analysis、Methane Hydrates and Related Phenomena、Geological Studies and Exploration

A set of nodular limestones was developed in the first member of the Middle Permian Maokou Formation (denoted as the Mao‐1 member) in the south‐eastern Sichuan Basin, south‐west China. Borehole coring has shown excellent signals of oil and gas from the Mao‐1 member carbonates, and many drilling wells have obtained industrial‐level gas flow. To assess the natural gas exploration potential of the Mao‐1 member in this area, sedimentary characteristics of drilling cores are described, and the formation mechanism of natural gas reservoir and its key controlling factors are also evaluated using data obtained from field geological survey, core observation, and laboratory experimental analysis. On this basis, the process of natural gas accumulation and evolution is examined. The results show that the Mao‐1 member nodular limestone comprises abundant marls and packstone to wackestone, and they were deposited in a lower part of the carbonate ramp setting. The marls exhibit rather high organic‐matter abundance and hydrocarbon generation capacity. Natural gas is mostly enriched in the marls developed talc diagenetic shrinkage pores and a certain number of organic‐matter pores, and their reservoir properties are much better than that of packstone‐wackestone. The natural gas in the Mao‐1 member is mainly self‐generated oil pyrolysis gas. The gas reservoir is characterized by the co‐existence of source rocks and reservoir, a lithology‐controlled reservoir, and a structure‐fracture‐controlle...