塔北隆起深层海相油藏中原油及族组分碳同位素组成的纵向分布特征及其地质意义

利用MAT252同位素质谱仪分析了塔里木盆地塔北隆起深层海相油藏中原油及族组分的碳同位素组成。研究表明该区深层海相油藏中原油的全油碳同位素组成主要受生源控制，受热力作用影响较小；而在继承生源的碳同位素组成的基础上，热力作用将对原油族组分的碳同位素组成及其逆转和分馏产生重要影响。总的趋势是随着油藏埋藏深度的增大和热力作用的加强，饱和烃组分的碳同位素组成逐渐变重，而沥青质组分的碳同位素组成不断变轻，族组分碳同位素逆转程度和分馏程度有所加强，并出现饱和烃﹥芳烃﹥非烃﹥沥青质的整体逆转现象。塔北隆起深层海相原油族组分的碳同位素组成的纵向变化特征，可以反映出热力作用对原油稳定性的影响。

Vertical Distribution Characteristics and Its Geological Significance for Carbon Isotopic Composition of Oils and Its Group Components of Deep Marine Oil Reservoirs in Tabei Uplift, Tarim Basin

The carbon isotopic compositions of the oils and its group components, which collected from the deep marine oil reservoirs in Tabei Uplift of Tarim Basin, were analyzed by the MAT252 Isotope Mass Spectrometer. The results showed that carbon isotopic compositions of these deep oils are mainly controlled by their parent material, and less affected by the thermal effects. Reversely, the carbon isotopic compositions and its reversed distributions and fractionations of these deep oil group components, on the basis of inheriting the carbon isotopic composition of parent materials, are evidently affected by the thermal effects. The carbon isotopic compositions of saturated hydrocarbons, with the increasing oil reservoirs depth and the enhancing thermal effect, gradually became heavy, but the carbon isotopic compositions of asphaltenes obviously lighten. The reversed distribution degree and fractionation degree of carbon isotope for these deep oil group components also increased, and there are totally reversed distribution in some samples that the distribution of δ13C values of the group components is saturated hydrocarbons﹥aromatics﹥non hydrocarbons﹥asphaltenes. The vertical distribution characteristics of oil group components of deep marine oil reservoirs in Tabei Uplift may indicate the influences of thermal effects on oil stability.