不同产地原油的碳稳定同位素组成特征研究

本文应用GC/MS、GC/IRMS和EA/IRMS等方法对6种不同产地原油的特征比值, 全油和正构烷烃组分的碳稳定同位素组成进行分析, 研究不同产地原油的碳稳定同位素组成特征, 并探讨其原因。结果显示, 6种原油的C₁₉+C₂₀/(C₁₉~C₂₂)、OEP₁和CPI_13-22特征比值不存在显著性差异, 不能作为区分这6种原油的有效指标。原油全样的δ13C值差异明显, 阿曼δ13C值最轻为-33.4‰, 巴西最重为-24.5‰, 其余4种原油介于两者之间。GC/IRMS分析结果显示不同油种具有不同的碳稳定同位素组成特征, 6种原油的正构烷烃δ13C值和分布曲线明显不同。单因素方差分析结果显示除个别油样外, 不同原油两两之间全油δ13C值和nC₂₀的δ13C值差异性显著(P < 0.05)。实验结果表明, 特征比值和碳稳定同位素组成相结合能更加有效的区分不同种类原油, 油品中同位素组成特征差异可为原油种类鉴别和溯源提供一个有效的技术支撑。

Research on the stable isotope composition characteristics of crude oils

In this study, GC/MS, GC/IRMS and EA/IRMS as the analytical methods were used to determine the characteristic ratios, bulk δ13C values and carbon isotope composition of the individual n-alkanes from six crude oils in different areas, which were compared and analyzed subsequently.The results showed that C₁₉+C₂₀/(C₁₉~C₂₂), OEP₁ and CPI_13-22 of different oils were not sharply demarcated t and even may be consistent, which can't be used as effective indicators to distinguish different types crude oils.The bulk δ13C values of six crude oils showed pronounced differences, which the most depleted was Oman and most enriched was Brazil, another four crude oils ranked among them.The results of GC/IRMS demonstrated that different carbon stable isotope composition characters existed in diverse types crude oils and significant differences could be found for δ13C values and profiles of n-alkanes.ANOVA results indicated that the deviations of the bulk δ13C and δ13C of nC₂₀ were significant among any two types oils (P < 0.05) except for exceptional oil samples. The study furthered evidences that the characteristic differences of stable carbon isotope composition in petroleum could provide an effective method support for identification and traceability of crude oils.It was worth noting that woul carbon isotope composition combined with characteristic ratioscound prominently improve the discernibility ability of crude oils from different origins.