Is there shale gas exploration potential in Longtan/Wujiaping Formation in the eastern Sichuan Basin?

Aug. 19,2022
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The Longtan/Wujiaping Formation in the Sichuan Basin is a set of sedimentary strata developed on the denuded plane of the Dongwu Movement. Affected by the movement of the Emei ground fissure, three types of organic-rich shale were developed, including tidal flat-lagoon facies (Longtan Formation), shallow-water mixed shelf facies (Longtan Formation) and deep-water shelf facies (Wujiaping Formation). What are the differences in the geological characteristics of these three kinds of shale, and whether they have the potential for shale gas exploration? It is necessary to carry out a systematic comparative study.

ZHAI Changbo, DENG Mo and CAO Qinggu of Petroleum Exploration and Production Research Institute of SINOPEC published an article named “Basic characteristics and exploration potential of shale gas in Longtan Formation of Upper Permian in eastern Sichuan Basin” in “Petroleum Geology & Experiment”. In this paper, the typical wells SY1, SYx and HYx in the above-mentioned three facies in the eastern Sichuan Basin were systematically compared with the characteristics of shale gas formation conditions. The similarities and differences in hydrocarbon generation, minerals, storage and gas-bearing characteristics of the Longtan/Wujiaping Formation in different facies belts were discussed, the shale gas exploration potential was confirmed, and the exploration direction was pointed out.

Research shows that the mud shale of the tidal flat-lagoon facies in the Longtan Formation has a wide distribution range, a large accumulative thickness, a complex lithology, and coal seam is developed in the entire section. It has the characteristics of “high TOC, clay and gas contents, and high porosity”. In order to achieve effective production, it is necessary to increase the research on fracturing technology of deep coal measure formations. The second member of the Wujiaping Formation of deep-water shelf facies is composed of siliceous shale and mudstone, which has the characteristics of “high TOC content, high brittle mineral content, high porosity, high gas content, and high gas saturation”. Its organic matter type is Ⅱ1, with widespread organic pores. It is currently the main strata for the exploration and development of Permian shale gas in the Sichuan Basin. Well HYx deployed in the Shizhu area has carried out staged fracturing of horizontal wells in the second member of the Wujiaping Formation and achieved a major breakthrough. It is expected to be a new target for shale gas exploration after breakthroughs in the Wufeng and Longmaxi formations, which will help consolidate the natural gas resource foundation in the Sichuan Basin. It is also of great significance to ensure national energy security. The coal seam of the second member of the Longtan Formation in the shallow water mixed continental shelf is basically undeveloped, mudstone distribution is relatively stable, TOC content is medium, and organic pores are relatively developed, which deserves attention in future exploration.

Relevant research results were published in “Petroleum Geology & Experiment”, Volume 43, Issue 6, 2021 (doi: 10.11781/sysydz202106921), and a bilingual version is now online (http://jtp.cnki.net/bilingual/detail/html/SYSD202106002).

Corresponding Author: ZHAI Changbo
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CNKI Press Officer: LI Jingjing YANG Na
Email: ljj6806@cnki.net yn6791@cnki.net

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