关键词: 四川盆地, 侏罗系, 成烃生物, 沉积有机相

Abstract: Three sets of organic-rich shales are developed in Jurassic in Sichuan Basin, including Dongyuemiao Member and
Da’anzhai Member of Ziliujing Formation and Qianfoya Formation. The hydrocarbon-forming organisms of the low-maturity source rocks from the Jurassic section in the Aojiaying area of northeastern Sichuan were analyzed by isolating kerogen. The results show that there are abundant types of hydrocarbon-forming organisms in the study area, including Botryococcus braunii, dinoflagellate , cyanobacteria and higher plants. Also, the characteristics of hydrocarbon-forming biological assemblages are developed in different layers. Higher plants are common in the Dongyuemiao Member, pico -plankton and shells are most abundant in the Da’anzhai Formation, and green algae , dinoflagellates and other hydrocarbon-forming biological types are developed in the Qianfoya Formation. Based on the development, occurrence and the combined characteristics of hydrocarbon-forming organisms, the Jurassic organic facies in the study area can be divided into seven types: pico -plankton bloom single algae organic facies (I), multi-algal symbiotic development-spore-pollen mixed organic facies (II), pico -plankton -shell mixed organic facies (III), planktonic algae-benthic algae-shell complex ecological organic facies (IV), shell-blue algae mixed organic facies (V), spore-pollen dominant organic facies (VI) and higher plant development organic facies (VII). Among them, type I and type II are the main organic facies types in the study area. Type Ⅰ mainly occurs in the Da’anzhai Member and the main hydrocarbon-forming organisms of the organic facies are pico -plankton that are often in a vigorous state. The total organic carbon content and hydrogen index of the sedimentary organic facies are high with the organic matter type being good. It is often developed in the semi-deep lake-deep lake facies. Type Ⅱ is mainly developed in the high-quality source rocks of the Qianfoya Formation, which is rich in various types of algae and pollen, with high total organic carbon content and hydrogen index, good organic matter type. It is mainly developed in shallow lake-semi-deep lake facies. 

Key words: Sichuan Basin, Jurassic, hydrocarbon-forming organisms, sedimentary organic facies