正构烷烃单体碳、氢同位素在油源对比中的应用

Application of Free C and H Isotopes in Normal Alkane to Correlation of Oil Sources in Huanghua Depression

以黄骅坳陷古生界烃源岩作为研究对象,采用GC-IRMS和GC-TC-IRMS技术对烃源岩抽提物中的正构烷烃单体碳、氢同位素进行测定,揭示不同沉积环境中正构烷烃单体碳、氢同位素的组成特征。研究结果表明,下古生界烃源岩正构烷烃的δ13C和δD值分别为-29‰^-33‰和-110‰^-140‰;上古生界烃源岩正构烷烃的δ13C和δD值分别为-27‰^-29‰和-140‰^-170‰.从下古生界的海相到上古生界的海陆过渡相,正构烷烃明显存在一个富δ13C和贫δD的趋势。这表明,沉积环境是控制烃源岩正构烷烃氢同位素组成的主要因素。因此,在复杂的含油气系统中,正构烷烃单体碳、氢同位素组成分布特征对油源对比有着重要的意义,并且可用于母质来源及沉积环境的探讨。

The free carbon and hydrogen isotopes in n-alkane from the Paleozoic source rocks in Huanghua depression are determined using techniques of GC-IRMS and GC-TC-IRMS to reveal the isotope compositions in different sedimentary environments. The results indicate that the δ^13C and δD from n-alkane of Lower Paleozoic （marine facies） source rocks range from -29‰ to -33‰ and from -110‰ to -140%; while the δ^13C and δD from n-alkane of Upper Paleozoic （transitional facies） source rocks range from -27‰ to-29‰ and from - 140‰ to -170‰, respectively. From the marine facies to the transitional facies, there obviously exist the trend of rich-δ^13C and poor-δD for the n-alkane. These also show that sedimentary environment could be the main factor controlling the isotopic compositions. It is concluded that in complex petroliferoos systems, free C and H isotopic compositions and distributions from n-alkane are of significance in oil source correlations, and could be applied to investigation of related kerogens and sedimentary environments.