银额盆地查干凹陷原油地化特征及油源对比

银额盆地东部查干凹陷首次发现轻质低硫成熟原油，其饱和径含量在90％以上，成熟度相当于镜煤反射率Ro1．0％左右，是生油高峰阶段的产物；原油全碳同位素δ^13C值－31．1‰。原油生物标志物中类异戊二烯含量较高，植烷与姥皖烷均势；三环萜烷含量高于五环萜烷；含有较高的TS C29、Ts、C30重排藿烷、伽马蜡烷；藿烷中以C50藿烷为主，C32以上升藿烷含量极低；孕甾烷含量高；甾烷中以C29甾烷为主，C27甾烷含量也较高，异胆甾烷含量高于胆甾烷；重排甾烷含量低；甾烷的含量与萜烷含量相当，是典型的湖相原油。已发现的天然气中甲烷含量达80％，为湿气。原油和源岩生物标志物组成特征分析对比表明下白垩统巴音戈壁组源岩是主要油源岩。生物标志物特征示原油具有一定的运移效应。

Geochemical Characteristics of Oil and Source Rock Correlation in the Chagan Sag of Yingen-Ejinaqi Basin, NW China

It is the first time that some crude oil has been discovered in the Chagan Sag, the eastern of the Yingen-Ejinaqi basin, NW China. The geochemical characterist ics of the oils (including oil sands) and source rock have been studied in this paper. The oils, in which saturated hydrocarbon accounts for more than 90%, belo ngs to maturated oils with a lower density and lower sulfur content at the gener aton peak stage (equal to Ro=1.0%±). The δ13C value of the whole o il is -31.1‰. The features of the biomarkers in the oils are as follows: relati vely high abundance of isoprenoidies, no preference between pristane and phytane ; the proportion of tricyclic terpanes over pentacyclic terpanes; relatively hig h amounts of Ts, C29Ts, C30-diahopane and gammacerane; the signific ant amounts of C30 hopane and much lower concentration of homohopanes (hig her than C32); high amounts of pregnanes; the significant proportion of C 29 sterane, relatively high abundance of C27 sterane, the proportion of isocholestane over cholestane; low concentration of diacholestane; equivalen t amounts between steranes and terpanes. The proportion of methane in the discov ered natural gas is up to 80%, reflecting that it belongs to wet gas.The oil-so urce correlation shows that the crude oils in Chagan Sag are generated from Lowe r Cretaceous Bayingebi Formation, and can be described as typical lacustrine oil s. Biomarkers reveal that the oil has a certain migration effect.