西藏北羌塘盆地光明湖地区上侏罗统白龙冰河组烃源岩有机质特征

    Organic Matter Characteristics of Source Rocks in Upper Jurassic Bailongbinghe Formation of the Guangmingco Area in North Qiangtang Basin, Tibet

    • 摘要: 通过对研究区露头烃源岩样品进行Rock-Eval热解模拟实验、干酪根镜鉴、镜质体反射率、族组分分离、单体烃碳同位素等分析,对北羌塘盆地光明湖地区侏罗系白龙冰河组烃源岩有机质特征进行研究。结果表明,该区白龙冰河组烃源岩以碳酸盐岩为主,有机碳含量0.01%~1.21%,平均值为0.39%,有机质丰度较高;干酪根显微组分以腐泥组为主,含量70%~92%,平均值为80%,以Ⅱ1型为主,主峰碳、(nC21-/ nC22+)轻/重比及Pr/nC17-Ph/nC18的相关图均表明有机质来自低等水生生物,有机质类型较好;镜质体反射率最小值1.409%,最大值2.423%,平均值为1.909%,有机质的热演化程度总体较高,达到高成熟-过成熟阶段。

       

      Abstract: The studied area locates in the Guangmingco area of north Qiangtang Basin. On the bases of Rock-Eval pyrolysis simulation experiment, kerogen identification, vitrinite reflection, ethnic component separation, and carbon isotope analysis of source rocks in outcrop samples of Jurassic Bailongbinghe Formation, the organic matter characteristics of source rocks were studied. The results indicated source rocks of Bailongbinghe Formation were dominated by carbonate and with high organic matter abundance, the organic carbon content obtained from 0.01% to 1.21%, averaging 0.39%. The content of sapropel in the kerogen ranged from 70% to 92%, averaging 80%, consistent with type Ⅱ1 kerogen. The main peak of carbon isotope, the ratio of (nC21-/ nC22+) and Pr/nC17-Ph/nC18 correlation diagram indicated that the organic matter came from lower aquatic organisms and the type of organic matter was well. The vitrinite reflection value was in the range from 1.409% to 2.423%, averaging 1.909%. The thermal evolution of organic matter is generally high, reaching high maturity-over mature stage.

       

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