Evaluation and analysis of paleoenvironments of the Neogene oil shale of Zhangcun Formation, Qinshui basin

In order to deeply analyze the indication of oil shale development characteristics on paleoenvironments and provide theoretical guidance for oil shale resource evaluation, the organic geochemistry and elemental geochemistry characteristics of the Neogene Zhangcun Formation oil shale in the central part of the Qinshui basin were analyzed by Rock-Eval and TOC and the paleoclimate and paleogeographic environments of the depositional period were discussed as well. The results show that the oil shale of Zhangcun Formation has the low oil content which Tar=4.15%, higher hydrocarbon potential, kerogen is of sapropel type(I₁), which has relatively shallow burial depth. The element enrichment coefficients indexes indicated that the source of organic matters are a mixed source, but productivity of lakes provided major material for oil shale. The climate was warm and humid during the depositional period, and the water in the basin was gradually desalted from salt lake, while the oil shale was formed in an anaerobic and deep lake environment with weak stratification. The geochemical characteristics of oil shale are well coupled with the palaeoclimate and palaeogeographical environments.