唐友军, 陈践发. 2011: 内蒙古西部额济纳旗苦水沟地区下石炭统白山组烃源岩分子化石的特征. 地质通报, 30(6): 888-894.
    引用本文: 唐友军, 陈践发. 2011: 内蒙古西部额济纳旗苦水沟地区下石炭统白山组烃源岩分子化石的特征. 地质通报, 30(6): 888-894.
    TANG You-jun, CHEN Jian-fa. 2011: Characteristics of molecular fossils in source rocks of Lower Carboniferous Baishan Formation in Kushuigou area of Ejin Banner, western Inner Mongolia.. Geological Bulletin of China, 30(6): 888-894.
    Citation: TANG You-jun, CHEN Jian-fa. 2011: Characteristics of molecular fossils in source rocks of Lower Carboniferous Baishan Formation in Kushuigou area of Ejin Banner, western Inner Mongolia.. Geological Bulletin of China, 30(6): 888-894.

    内蒙古西部额济纳旗苦水沟地区下石炭统白山组烃源岩分子化石的特征

    Characteristics of molecular fossils in source rocks of Lower Carboniferous Baishan Formation in Kushuigou area of Ejin Banner, western Inner Mongolia.

    • 摘要: 采用气相色谱、气相色谱-质谱技术,对额济纳旗苦水沟地区白山组烃源岩分子化石的特征进行了研究,剖析了分子化石蕴含的生源、沉积环境、成熟度等方面的信息及石油地质意义。白山组烃源岩饱和烃气相色谱为“前峰型”的单峰分布,主峰碳以C18为主, 表明有机质来源以海相有机质为主,Pr/Ph介于0.4~0.6之间,指示强还原的沉积环境。白山组烃源岩具有“长侧链的三环萜烷丰富、伽马蜡烷含量高和C27甾烷分布占优势”的分子化石组合特征,高伽马蜡烷含量揭示烃源岩有机相为咸水沉积环境,藿烷/甾烷比值的平均值为1.06,表明细菌和藻类对有机质的贡献处于均势,C27甾烷丰度较高,说明低等水生生物藻类是生烃母质主要的生源构成。甲基菲指数是衡量高演化有机质热演化的有效分子参数指标,白山组烃源岩甲基菲指数介于0.36~0.67之间,折算的镜质体反射率Rc为1.9~2.1,与实测的镜质体反射率相当,说明白山组烃源岩热演化处于过成熟阶段。

       

      Abstract: Based on gas chromatography and gas chromatography mass spectrometry techniques, the authors studied molecular fossils characteristics of the Baishan Formation source rocks in Kushuigou, Ejin Banner, and analyzed the information and petroleum geological significance indicated by sources of organic matter, sedimentary environment, maturity and some other factors. Gas chromatography peaks of saturated hydrocarbons from Baishan Formation source rocks showed “the former peak” of the single peak distribution and the main peak of carbon composed mainly of C18. This indicates that the main sources of organic matter were marine organic matter, and Pr/Ph ranged from 0.4 to 0.6, suggesting a strongly reducing sedimentary environment. Molecular fossil assemblages of Baishan Formation source rocks were abundant in tricyclic terpane with long side chains, had high level of gammacerane, and showed dominant distribution of C27 steranes. High content of gammacerane in organic matter suggested that organic facies of source rocks was in a saltwater sedimentary environment. The hopanes/steranes ratio was 1.06 on average, implying that bacteria and algae had almost the same contribution to organic matter. And high level of C27 steranes showed that alga was the main source of hydrocarbon precursors. The methylphenanthrene indexes of Baishan Formation, which were effective molecular parameter indexes for measuring thermal evolution of organic matter, ranged from 0.36 to 0.67, and their conversions into vitrinite reflectance Rc ranged 1.9 to 2.1, corresponding well to the actually measured data, indicating that source rocks of Baishan Formation are at the over-mature stage of thermal evolution.

       

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