Characteristics And Application Of Biomarker Compounds Of Terrestrial Source Rocks In The Sichuan Basin

Along with evolution of sedimentary structure of the basin, five sets of continental hydrocarbon source rocks, characterized by continental sedimentation, are developed bottom up in the longitudinal direction, namely, the Upper Triassic T3x1, Mid-T3x2, T3x3, T3x3 and the Lower Jurassic Ziliujing upper segment, in Sichuan Basin. In which, the Upper Triassic continental hydrocarbon source rocks are mainly distributed in the Western Sichuan Depression, while T3x1 to T3x5 hydrocarbon source rocks expand toward the east, with the T3x5 hydrocarbon source rocks finally getting denudated to the north of Western Sichuan. The Lower Jurassic hydrocarbon source rocks reach the thickest in Dazhou and get thinned gradually toward the basin. This paper, referring to theories of petroleum geology, petroleum geochemistry and other disciplines, summarized and analyzed biomarker characteristics of the continental hydrocarbon source rocks in the basin, with diversified modern analysis and test methods in the integrated indoors-outdoors and macro-micro ways. Following conclusions were obtained finally:1?The four sets of Upper Triassic hydrocarbon source rocks have rich content of organic carbon, while such content is lowered in the Lower Jurassic Series. Nevertheless, the rocks are good hydrocarbon source rocks and the organic matters are dominated by kerogen ? and ? at the mature to high/over mature stage of thermal evolution. To be specific, T3x3 rocks are good gas source rocks, while the Lower Jurassic Series are good oil source rocks.2?Jurassic hydrocarbon source rocks of biomarker compounds generally present characteristic of "four compound contents are high while one is low+L-type". By contrast,the hydrocarbon source rocks of the first, third and fifth sections of Xujiahe River of the Triassic present characteristic of'four compound contents are low while one is high+L-type". The second sections of Xujiahe River is relatively special, for it usually present biomarker compound characteristic of "four compound contents are low while one is high+L-type"3-. According to the analysis and test data concerning natural gas and crude oil, it is believed that the T3x2 natural gas in Jiulongshan Gas Field is mainly source-mixed gas generated from the Mid-T3X2 and the deep marine hydrocarbon source rocks, while the Zhenzhuchong Formation natural gas is mainly generated from the T3x3 hydrocarbon rocks, and the crude oil in the Jurassic system of the Gongshanmiao Oil Field is mainly generated from the Lower Jurassic hydrocarbon source rocks, together with small amount of natural gas from the Xujiahe Formation.