内蒙古海拉尔盆地侏罗系烃源岩地球化学特征

    GEOCHEMISTRY OF THE JURASSIC SOURCE ROCKS IN HAILAR BASIN, INNER MONGOLIA

    • 摘要: 在海拉尔盆地外围及周边地区选取了31块侏罗系野外烃源岩分析样品,进行了总有机碳、岩石中可溶有机质的抽提和岩石热解分析;针对该区侏罗系烃源岩,共对17口井岩心进行了取样地化分析,利用气相色谱-质谱对烃源岩氯仿抽提物及重要生物标志化合物开展了定性与定量检测,目的是对源岩地球化学特征进行系统评价,为下一步油气基础地质调查奠定基础.结果表明,海拉尔盆地外围及周边地区的侏罗系部分的烃源岩有机质丰度较高,应具备较好的生烃物质基础.海拉尔盆地侏罗系烃源岩总体属于淡水-半咸水环境,有机质类型多样,成熟度普遍较高.甾类化合物中以规则甾烷为主,沉积物中具有较高丰度的以五环三萜烷为主的三环萜烷化合物,显示了其应以藻类生源为主,高等植物为主的陆相沉积中的相对含量则较低.伽马蜡烷的含量普遍很低.OEP呈偶碳数优势,并且缺失高分子正构烷烃,说明烃源岩成熟度演化早期受到了微生物降解作用.

       

      Abstract: In the periphery and surrounding areas of the Hailar Basin, 31 samples of Jurassic source rocks from the field are selected to analyze rock pyrolysis, extraction of soluble organic matter from rocks and total organic carbon. In order to study the Jurassic hydrocarbon source rocks in this area, cores from 17 wells are sampled and analyzed. The chloroform extracts of the hydrocarbon source rocks and significant biomarkers are detected qualitatively and quantitatively with gas chromatography-mass spectrometry, aiming to systematically evaluate the geochemical characteristics of the source rocks for further geological survey of oil and gas. The results show that the source rocks in the periphery and surrounding areas of Hailar Basin are of high organic matter abundance, with good hydrocarbon generating condition. The environment of the Jurassic source rocks in Hailar Basin belongs to fresh water-brackish water, with diverse types of organic matter and generally high maturity. The steroids are of mainly regular sterane type. The sediment contains high abundance of tricyclic terpane, mainly as pentacyclic triterpane, reflecting a high content of algae. The content of gammacerane is very low. The advantage of even carbon number of OEP and the absence of high molecular normal paraffin shows that the maturity of hydrocarbon source rock has been degraded by microorganisms in the early stage.

       

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