Shale gas reservoir geology of the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in western Hubei and northeastern Chongqing

The Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation are important strata for shale gas exploration in the western Hubei and northeastern Chongqing area. At present, no breakthrough has been made in exploration, and the main factors controlling shale gas enrichment are unclear. The spatial and temporal distribution, geochemical features, reservoir properties and gas-bearing capacities of high-quality shale of deep-water continental shelf facies in the Wufeng-Longmaxi formations were studied based on the analysis of drill core and field outcrop data of well JD1 and its adjacent area in Jianshi area. Organic-rich shale was developed well in the Wufeng-Longmaxi formations. The organic-rich shale of deep-water continental shelf facies was mainly found in the Katian, Hirnantian and Rhuddanian stages, which featured substantial thickness, high TOC content, medium maturity, favorable reservoir conditions and medium burial depth, showing a good potential for shale gas enrichment. The organic-rich shale of deep-water continental shelf facies in the Katian, Hirnantian and Rhuddanian stages had a stable structure with few fractures, and a regional cap rock in the Middle and Lower Triassic and these are the main controls for shale gas enrichment in the Wufeng-Longmaxi formations in the western Hubei and northeastern Chongqing area.