Shale gas accumulation conditions and exploration prospects of Wufeng−Longmaxi Formation in Shixi Area, Northern Guizhou

This paper is the result of oil and gas exploration engineering.

Objective The purpose of this paper is to reveal the shale gas accumulation conditions in the complex structural area and to identify the shale gas accumulation potential of Wufeng Formation−Longmaxi Formation in Northern Guizhou by analyzing the shale accumulation elements of Wufeng−Longmaxi Formation in Well SX 1.

Methods This paper focuses on the comprehensive study of shale gas accumulation from the three dimensions of "source, reservoir, and protection", based on the comprehensive experimental analysis of the series drilling coring, logging curves, seismic data, and geochemical testing and reservoir characteristics of Well SX−1.

Results The thickness of organic−rich shale in Wufeng−Longmaxi Formation of Well SX 1 is about 25 m, the TOC content is between 2.79% and 4.77%, and the equivalent vitrinite reflectance is about 2.01%−2.59%. The organic matter type is the primary type I, which has a good gas foundation. The content of brittle minerals in the organic−rich shale section is relatively high, with an average value of about 61.05%, indicating high brittleness. A large number of micro−nano pores are developed, mainly organic pores and inorganic−organic composite pores. The pore volume and specific surface area parameters are good, which provides a good reservoir space for the occurrence of shale gas. The roof and floor of the organic−rich shale section in the residual syncline have a good sealing ability. The three vertically form a good source−reservoir−cap assemblage. There are two large faults in the east and west of Well SX 1, but they are far from Well SX 1. At the same time, due to the good sealing of the faults and the gentle formation occurrence, Well SX 1 has a good gas−bearing display.

Conclusions In summary, the shale of Wufeng−Longmaxi Formation in the residual syncline in northern Guizhou also has oil and gas geological conditions with high efficiency and large−scale production of shale gas, which is the key direction of next exploration and research. The results expand the scope of shale gas exploration, broaden the depth and breadth of shale gas exploration around the Sichuan Basin, and are expected to form a new resource replacement area.