AN INVESTIGATION ON THE GEOCHEMICAL CHARACTERISTICS OF CRUDE OIL FROM WENLIU AREA IN THE DONGPU SAG, BOHAI BAY BASIN
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摘要: 对东濮凹陷文留地区原油样和油砂样进行了族组分、碳同位素、饱和烃色谱—质谱实验分析,结果表明,文留地区沙河街组原油与含油砂岩抽提物的饱和烃含量在38.3%-79.3%;原油碳同位素值分布于-27.0‰～-28.0‰,饱和烃碳同位素值在-27.4‰～-28.7‰,族组分之间的碳同位素分馏效应较小;多数样品Pr/Ph小于0.5,具有明显的植烷优势;αααC2920R/20(R+S),C29ββ/(αα+ββ)参数显示处于低熟状态;甾烷系列中C27含量略占优势,重排甾烷含量与成熟度相关,随样品成熟度增高,重排甾烷/规则甾烷值增大,低熟油样品的重排甾烷/规则甾烷值小于0.3。分布在中央隆起带文西断层与文东断层之间地区的样品,其γ-蜡烷含量较高,γ-蜡烷/C30藿烷分布于0.40～0.99,γ-蜡烷/H3122S.分布于2.11～4.15,反映了陆相咸水湖相原油特征。分布于文东断层以东的原油样品γ-蜡烷含量低,γ-蜡烷/C30藿烷分布于0.05～0.15,γ-蜡烷/H3122S分布于0.16～0.28,反映了低盐度的淡水—微咸水相原油特征。Abstract: The group composition and carbon isotope of oil,chromatogram and mass spectrum of saturation hydrocarbon in the source rocks and crude oil from Wenliu area in Dongpu Sag,Bohai Bay Basin were analyzed.The studying results show that the crude oil in the Shahejie Formation was mainly immature.The content of saturation hydrocarbon in the samples is 38.3%～79.3%.The carbon isotope of group composition of crude oil is-27.4‰～-28.7‰,and the fractionation effect of the carbon isotope of group composition is not obvious.There is predominance of phytane to pristane,and the ratio of pristane to phytane is lower than 0.5 in most samples.For the most samples,the values of αααC2920R/20(R+S) and C29ββ/(αα+ββ) are lower than 0.40,the content of diasteranes is low,and the sterane of C27 is predominance in the series of steranes.The ratio of diasteranes to regsteranes is related to the maturity of samples.High maturity is correspond to high value of the ratio.For the samples distributing between the Wendong fault and Wenxi fault,the content of Gammacerance is high,the ratio of gamma-cerance to C30hopanes is 0.40～0.99,the ratio of gammacerance to HC3122S is 2.11～4.15 and the geochemical characteristics demonstrated that they formed in the salt lake facies sedimentary environment.For the samples located in the east of Wendong fault,the content of Gammacerance was low,the ratio of gammacerance to C30 hopanes is 0.05～0.15,the ratio of gammacerance to HC3122S is 0.16～0.28,and the geochemistry characteristics demonstrated that they formed in the sedimentary environment of low salty.
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Key words:
- biomarker /
- immature oil /
- saline lake /
- Dongpu Sag /
- Bohai Bay Basin
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