4‐甲基甾烷在油源对比中的应用——以渤南洼陷北部陡坡带为例
摘要: 同一洼陷不同次洼的烃源岩及生成的原油,由于古气候、古沉积环境较为相似,其常规生物标志化合物和同位素特征差别非常小,给油源分析带来困难。通过GC—MS分析提取原油和烃源岩中分子化石信息,主要依据4甲基甾烷的相对含量和不同构型的4甲基甾烷的分布特征来进行油源对比,为类似地区的油源分析提供了一种新思路。渤南洼陷发育Es4s和Es3x两套主力烃源岩,中部次洼、西部次洼和渤南深洼Es3x烃源岩的4甲基甾烷/C29甾烷值分别为4.51、2.79、1.27,是由于烃源岩中沟鞭藻有机质占总有机质的比例不同所造成。不同地区原油C20、C21、C23三环萜烷和ααα20RC27、C28、C29规则甾烷等特征非常相似,成熟度相当,中、西、东三个地区原油的4甲基甾烷/C29甾烷值分别为2.89,2.39和2.06,区别明显,各个地区4甲基甾烷的构型也不同。对比结果表明,渤南洼陷北部陡坡带Es4s和Es3x油气均为近源成藏,主要来源于其临近次洼的Es3x烃源岩。
Application of 4Methyl Steranes in OilSource Correlation:A case study from northern steep slope zone of Bonan Sag
Abstract: Because of the samilar paleoclimate and palosedimentary environment, regular biomarkers and isotope distinction of the source rocks and generated petroleum in the subsag belong to the same sag is tiny, which bring difficulties to oilsource correlation. By extracting molecular fossils information using GCMS technology, according to the relative content of 4methyl steranes and distribution characteristics of 4methyl steranes isomers, oilsource correlation work are performed ,which provides a new method for oilsource correlation in similar area. Es4s and Es3x two sets of source rocks are developed in the study area, they are characterized by high organic matter abundance, mature to over mature thermal evolution degrees. Organic matter of Es4s are formed in brackishsaline water with reductive environment, organic matter of Es3x are formed in freshsaline water with reductive environment , organic matter input of both source rocks are dominated by lower aquatic organisms and terrigenous higher plants, while terrigenous higher plants are more abundant near provenance. Relative content of 4methyl steranes of Es3x source rocks is higher than that of Es4s source rocks, indicating the better organic matter input of Es3x source rocks.The value of 4methyl steranes/C29 steranes of Es3x source rocks in the middle, west and deep subsag is 4.51,2.79 and 1.27, respectively, which is caused by the different proportion of dinophyceae in total organic matter. The distribution characteristics of C20, C21, C23 tricyclic terpanes and ααα20RC27,C28,C29regular steranes of oils with alike maturity in different region is quite similar, 4methyl steranes/C29steranes value of crude oils in the middle, west and east region is 2.89, 2.39, 2.06, respectively, which make a big difference, while the carbon isotope characteristics of crude oils are opposite, distribution characteristics of 4methyl steranes isomers of each region is also different. Oilsource correlation demonstrate that Es4s and Es3x crude oils of northern steep slope zone mainly originate from Es3x source rocks in nearby sag, crude oils of the western zone are provided by Es3x source rocks of the western sag, crude oils of the middle zone are provided by Es3x source rocks of the middle sag, crude oils of the eastern zone are provided by Es3x source rocks of deep sag in the eastern zone, and no contribution from source rocks of the Gubei Sag.
4‐甲基甾烷在油源对比中的应用——以渤南洼陷北部陡坡带为例[J]. 沉积学报, 2012, 30(4): 770-778.
引用本文: |
4‐甲基甾烷在油源对比中的应用——以渤南洼陷北部陡坡带为例[J]. 沉积学报, 2012, 30(4): 770-778.
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Application of 4Methyl Steranes in OilSource Correlation:A case study from northern steep slope zone of Bonan Sag[J]. Acta Sedimentologica Sinica, 2012, 30(4): 770-778.
Citation: |
Application of 4Methyl Steranes in OilSource Correlation:A case study from northern steep slope zone of Bonan Sag[J]. Acta Sedimentologica Sinica, 2012, 30(4): 770-778.
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