Evaluation of shale gas resource potential of Longmaxi Formation in Zhaotong National Shale Gas Demonstration Area in the Northern Yunnan-Guizhou

The study area is located in the central and western part of Weixin Sag in the northern Yunnan-Guizhou to the southern margin of the southern Sichuan Low-steep fold belt. This paper analyzed the basic geological characteristics of the Longmaxi black shale using drilling, field outcrops, regional geology and other data. And the shale gas resource of Longmaxi black shale were evaluated by using volume method. The research results show that the studied Longmaxi black shale is relatively high in TOC, maturity and brittle mineral content, relatively saprolitic in organic matter type, and medium in physical properties and total gas content. The above characteristics of Longmaxi black shale has certain comparability with the major gas-producing shale in Weiyuan, Changning and North America. The preliminary estimation of shale gas resource of the Longmaxi Formation in the study area is 24871.8×10⁸ m³, which shows a good prospect for shale gas exploration. But affected by characteristics of reservoir development and preservation conditions, the shale gas resources are severely unevenly distributed. Shale gas resources with good quality are mainly distributed in the first layer, and the southern Sichuan low-steep fold belt in the northern part of the study area is the main area equipped with good quality resources. The wide anticline and box anticline structural belts with good preservation conditions are favorable areas for the next exploration.