Abstract

Abstract The geochemical characteristics of shale such as total organic content, type and maturity, shale sedimentary environment, geological characteristics, and scale of development were analyzed to study the geological characteristics and resource potential of lacustrine shale in the Lower Jurassic Ziliujing Formation in the Sichuan Basin. The Lower Jurassic Ziliujing Formation lacustrine shale is mainly developed in the Dongyuemiao and Da'anzhai members. The geochemical analysis of the organic carbon content, kerogen macerals, biomarker compounds and vitrinite reflectance of the shale samples showed that the total organic content is generally over 1.0%; the main organic type is II1-III, but type II1 is in the central part of the basin; the vitrinite reflectance value (Ro) is 1.05%–1.82%, thus the shale has a strong ability to generate gas. The thickness of the distributed Ziliujing shale is approximately 40–150 m, the average porosity is 1%–5%, and the permeability is 0.001×10−3–0.100×10−3 μm2. The lacustrine shale consists of different assemblages: pure shale, shale with imbedded lime band, and shale with thin-middle shell limestone. The shale has high quartz content, favorable for exploitation of shale gas; the lime band and the shelly limestone, which are developed in the shale can further improve the shale economic recoverability. The estimated shale gas resources of the Ziliujing lacustrine shale by volumetric method is about 3.8×1012–8.7×1012 m3.

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