Organic Geochemical Characteristics of the Shale from Y1 Well in Chengkou Area of Northeastern Chongqing and Exploration Prospects

A study has been conducted based on the drilling data and geochemical data from the Y1 Well in Chengkou of Northeastern Chongqing, including total organic carbon (TOC), kerogen microcomponent, equivalent vitrinite reflectance (Ro) and carbon isotope composition, which are the organic geochemistry characteristics of Wufeng-Longmaxi Formation shale. The characteristics of shale gas accumulation were determined by analyzing the microstructure, homogenization temperature and laser Raman data of fluid inclusions in the shale. Results show that carbonaceous shale is well developed in Upper Ordovician Wufeng Formation and Lower Silurian Longmaxi Formation in the Y1 Well. Organic-rich shale (TOC>2%) has a thickness up to 83 m. The kerogen type of the samples is mainly TypeⅠ, belonging to the moisture hydrocarbon generation stage. Numerous hydrocarbon inclusions and hydrocarbon-rich brine inclusions with methane gas in the fractured veins of shale indicate that the shale of Wufeng Formation-Longmaxi Formation in the Chengkou area has been supplied with sufficient shale gas. The associated brine inclusions with high homogenization temperature and high salinity indicate good preservation conditions during the shale gas accumulation period in the Chengkou area. The exploration results of the Y1 Well reveal good exploration prospects for shale gas in the lower Paleozoic strata in the Chengkou area.