准噶尔盆地液态烃分子碳同位素组成特征及其应用

Stable Carbon Isotope Compositions of Liquid Hydrocarbon Molecules and their Application

文章报导了准噶尔盆地不同地区、不同产层原油和烃源岩样品中正构烷烃和类异成二烯烃碳同位素组成特征。在ｎＣ１１－ｎＣ３４之间，保罗系湖沼相成因的原油，正构烷烃δ１３Ｃ值大部分分布在－２７．０‰──３２．４‰之间，比海相地层的原油重，具有富集１３Ｃ的特征。ⅡＡ型烃源岩产出原油的单烃δ１３Ｃ值比ⅡＢ型的轻，相对富集１２Ｃ。碳源组成相同的原油在正构烷烃和类异成二烯烃碳同位素组成上，有相似的分布范围和较为一致的总体变化趋势，因此单烃碳同位素组成可用于油－油对比和油－源对比中。

This paper reports carbon isotopic compositions of individual n-alkanes and isoprenoids from crude oil and source rock samples in the Junggar Basin. Between nC11 and nC34 , the most part of isotopic compositions of n-alkanes originating from the Jurassic limnetic factes is-27.0‰, to-32.4‰,,heavier than that of the crude oil from the marine factes strata, characterized by 13C-rich isotope.The n-alkane δ13C values of the crude oil from the type Ⅱ A source rock are lighter than that of the type Ⅱ B oil, it suggests that n-alkane be richer in 12C relatively.If crude oils are derived from the same group of organism or,at least,from organism using the same carbon source, the δ13C values of these n-alkanes and isoprenoids have a similar distributional range and total variational trend. Therefore, these data can be used in the source rock/oil correlation.The isotopic compositions of individual n-alkanes of the oil from the Cainan oil field become similar to that from the lower Jurassic Sangonghe source rock, they show a variation from-26.0‰,to-32.0‰,in the nC11 to nC32 range, among the same carbon numbers, the δ13C differences is less than 2‰,especially the δ13C value of n-alkanes in the Cainan oil matches that in the saturated hydrocarbon fractions from the lower Jurassic Sangonghe source rock.In the Pencan-2 well, the δ13C values of crude oil n-alkanes coincide with that of the Badaowan source.The Du-71 well is located on the southern margin of the Junggar Basin, its productive strata are shallower.The δ13C values of C11-C23 n-alkanes vary from heavier to lighter with increasing of the carbon number, ranging from - 25. 4‰, to - 33.0‰, These values have a similar trend to the Toutunhe source rock. Through the study on microbiology, it has been proved that there is a great amount of Methanococcus in the Toutunhe hydrocarbon source rock.Therefore, the origin of the Dushanzi oil is possibly related to archaeobacteria.