ORGANIC GEOCHEMISTRY OF THE SOURCE ROCKS IN THE DONGYING FORMATION OF THE SOUTH BOZHONG SUBSAG
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摘要:
应用有机碳、干酪根、岩石热解、氯仿沥青“A”、族组分、Ro、饱和烃色谱-质谱等有机地球化学分析测试资料，重点对渤中凹陷南洼东营组烃源岩的有机质丰度、类型、成熟度及母质来源与沉积环境进行了研究，为东营组资源潜力评价与油源对比提供依据。结果显示，东三段有机碳含量较高，属于优质的烃源岩；岩石热解实验与干酪根显微组分观察显示东营组烃源岩有机质类型主要是Ⅱ1-Ⅱ2型；生物标志化合物特征中表现为较低的Pr/Ph值和伽马蜡烷指数，结合Pr/nC17和Ph/nC18指示南洼东营组沉积为弱氧化还原的淡水—微咸水滨浅湖相沉积环境；正构烷烃的分布、较高含量的C29甾烷、4-甲基甾烷指数、C19/C23三环萜烷和C24四环萜烷/C26三环萜烷值显示有机质母质以混源为主，往上沉积陆源碎屑的供给越多；镜质体反射率Ro、CPI、OEP、C2920S/（20S+20R）、C29ββ/（αα+ββ）、Ts/Tm等参数表明东三段烃源岩处于成熟演化阶段，已开始大量生烃，东二段位于低熟阶段，东一段位于低熟—未熟阶段。
Abstract:This paper is devoted to the studies of organic matter abundance, type, maturity, parent matter source and depositional environment of the source rocks in the Dongying Formation of the south Bozhong subsag. Analysis results of organic carbon, kerogen, rock pyrolysis, chloroform bitumen "A", group components, Ro, saturated hydrocarbon chromatography-mass spectrometry are collected for the purpose of resource evaluation and source comparison. Results suggest that E3d3 is a high-quality source rock with rather high content of organic carbon. Rock pyrolysis experiments and kerogen maceral observation proves that the organic matters of the source rocks of the Dongying Formation are dominated by type Ⅱ1-Ⅱ2; The biomarkers are relatively low in Pr/Ph and Gamma-paraffin index, and the combination of Pr/nC17 and Ph/nC18 indicates a weak reduction and fresh-brackish water dominated shallow-lacustrine environment in which the Dongying Formation was deposited. The distribution of n-alkanes, high content of C29 steranes, 4-methylsteranes, C19/C23 tricyclic terpanes and C24 tetracyclic terpanes /C26 tricyclic terpanes suggest that the organic matters are coming from a mixed source, with certain amount of terrigenous input. The parameters of Ro, CPI, OEP, C2920S/(20S+20R), C29ββ/(αα+ββ) and Ts/Tm confirm that the source rocks of the E3d3 have matured and started to generate substantial amount of hydrocarbons. However, the E3d2 still remain in the stage of low maturity, and the E3d1 in the stage of low maturity and/or even immature.
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表 1 陆相烃源岩有机质丰度评价指标
Table 1. Evaluation index of organic matter abundance in terrestrial hydrocarbon source rocks
指标 湖盆水体类型 非生油岩 生油岩类型 差 中等 好 最好 TOC/% 淡水—半咸水 <0.4 0.4~0.6 >0.6~1.0 >1.0~2.0 >2.0 咸水—超咸水 <0.2 0.2~0.4 >0.4~0.6 >0.6~0.8 >0.8 “A”/% / <0.015 0.015~0.050 >0.050~0.100 >0.100~0.200 >0.200 HC/10−6 / <100 100~200 >200~500 >500~1000 >1000 S1+S2/（mg·g−1） / / <2 2-6 >6~20 >20 
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