ISSN 1009-6248CN 61-1149/P 双月刊

主管单位:中国地质调查局

主办单位:中国地质调查局西安地质调查中心
中国地质学会

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    河套盆地临河坳陷庆浅1井区原油地球化学特征与油源对比

    Geochemical Characteristics of Crude Oil in the well Zone of Qingqian 1 in Linhe Depression of Hetao Basin, China: Implication for Oil-Source Correlation

    • 摘要: 河套盆地历经40余年的勘探,近年来,在临河坳陷取得了油气发现与突破。通过对临河坳陷吉西凸起庆格勒图地区庆浅1等4口钻井原油物理性质、族组成、碳同位素、饱和烃气相色谱及萜烷、甾烷等生物标志化合物特征分析表明,研究区4口钻井原油为稠油,是深部正常原油沿断裂运移到浅部形成的轻微降解次生稠油。4口钻井原油地球化学特征相似,全油碳同位素为-28‰~-24‰,饱和烃气相色谱呈单峰型,具有明显的植烷优势。萜烷类化合物以伽玛蜡烷为主,规则甾烷呈现出以C27甾烷占优势的"L"型分布特征,指示其烃源岩为陆相强还原性高盐度沉积环境,有机质母源以低等水生生物为主,同时存在高等植物的贡献;饱和烃气相色谱及生物标志化合物特征指示原油处于成熟阶段。萜烷和甾烷等生物标志化合物对比表明,研究区原油与古近系临河组烃源岩差异明显,与白垩系固原组烃源岩具有良好的亲缘关系。

       

      Abstract: After over four decades of exploration, the hydrocarbon discovery and exploration targets selection have been made in the Hetao Basin recently. In this paper, the crude oil of 4 wells (including Well Qingqian1 et al.) in Qinggeletu area of Jixi uplift has been analyzed from the aspects of basic physical properties, group components, carbon isotopes, gas chromatgraphy-mass spectrometry (GC-MS), terpane and sterane compounds. The results indicate that the crude oil in the study area is heavy oil, and it is the product of slight secondary degradation when the deep normal crude oil migrated to the shallow parts along the faults. The geochemical characteristics of crude oil in the 4 wells are similar:①the stable carbon isotope values range from-28‰ to-24‰. ②the gas chromatograms of saturated hydrocarbons appears as a single-peak type, with the phytane (Ph) dominance. ③the terpane compounds are characterized by a high content of gammacerane; and 4) the distribution patterns of regular steranes (C27, C28 and C29) appear to be in asymmetrical shaped-"L", with the C27 sterane dominance. As the aforementioned, the results indicate that the paleo-environments of the source rock was strong reducing and high paleo-salinity conditions in the lacustrine, and the organic matter origins are predominantly aquatic micro-organisms, with incorporations of terrestrial higher plants. According to the characteristics of biomarkers and GC-MS of saturated hydrocarbons, the crude oils were formed in the thermal-mature stage. Based on the biomarkers characteristics (terpanes and steranes), the crude oils show favorable correlations with the source rocks in Cretaceous Guyuan Formation, while the crude oil show poor correlations with the source rock in the Paleogene Linhe Formation.

       

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