柴西地区古近系油砂有机地球化学特征  

The Organic Geochemistry of Palaeogene Oil Sands in Western Qaidam Basin

作　　者：李萌瑶 赵欣[1] 周科[1] 王有孝[2] 

机构地区：[1]长安大学地球科学与资源学院,西安710054 [2]中国科学院地质与地球物理研究所兰州油气资源研究中心,兰州730000

出　　处：《新疆石油地质》2014年第2期177-181,共5页Xinjiang Petroleum Geology

基　　金：中国地质调查局科技项目(1212011121222)

摘　　要：通过对柴达木盆地西部坳陷区古近系下油砂山组和下干柴沟组油砂抽提物及原油样品饱和烃的GC-MS分析,研究了生物标志化合物的地球化学特征。结果表明,油砂和原油形成于还原性较强的盐湖环境,有机质类型主要为Ⅱ型干酪根,含有丰富C27规则甾烷、藿烷和长链三环萜烷,反映了低等水生藻类和细菌对有机质成烃的贡献。m(αααC29甾烷20S)/m[αααC29甾烷(20S+20R)]值和m(αααC29甾烷ββ)/m[αααC29甾烷(αα+ββ)]值揭示下油砂山组和下干柴沟组油砂是低成熟—成熟原油运移至储集层后而形成的。部分低碳数正构烷烃及姥鲛烷、植烷等的缺失,表明油砂中烃类曾受到了强烈的细菌微生物改造等次生蚀变作用,这与油砂受构造运动被抬升而暴露于地表的地质背景相一致。Based on the extraction and the GC-MS analysis of saturated hydrocarbons from oil sand samples of the Palaeogene Lower You- shashan formation and Lower Ganchaigou formation in western Qaidam basin, the geochemical characteristic of biomarkers in these hydro- carbons are studied. The results show that the hydrocarbons of oil sands and crude oils formed in a strong reducing saline lacustrine deposi- tional environment. The type of organic matter is mainly II kerogen, in which contains abundant C27 regular sterane, hopance and long-chain tricyclene, reflecting the contribution of the algae of lower aquatic plants and bacteria to the hydrocarbons from organic matter. The ratios of m（ctc^et C29 sterane 20S）/m[c^c^c^C29 sterane （20S＋20R）] and m（c^cta C29 steranel313）/m[ctc^c~ C29 sterane （c^c~＋~[3） ] reveal that the oil sands of Lower Youshashan and Lower Ganchaigou formations are generated after low mature- mature crude oil migrating into the reservoir. The loss of relative low n-alkane and Pr and Ph suggests that hydrocarbons in the oil sands once endured heavy biodegradation and some other sec- ondary alterations. It is related to the geological background that the oil sands were uplifted and exposed to the surface due to tectonic movement.

关 键 词：柴达木盆地 油砂 下油砂山组 下干柴沟组 生物标志化合物 有机地球化学特征 

分 类 号：TE112.221[石油与天然气工程—油气勘探]