Geochemical characterization and quantitative identification of mixed-source oils from the Baikouquan and Lower Wuerhe Formations in the eastern slope of the Mahu Sag, Junggar Basin, NW China

摘要

The quantitative identification of mixed-source oil is a popular yet difficult topic in current petroleum geochemistry research. The mixed-source oils of the Baikouquan and Lower Wuerhe formations in the eastern slope of the Mahu Sag of Junggar Basin were used as a typical example in this study. Quantitative research on mixed oils was carried out in the study area and good results were obtained using an approach combining organic geochemistry and chemometrics. The results of crude oil geochemistry research show that mixed-source crude oil is ubiquitous in the study area. After comprehensive analysis, it is likely that there are three endmembers in the current mixed-source oils. Two of the endmembers may represent mainly the contribution of the early and late source rocks of the Permian Fengcheng Formation and are dominated by late filled crude oil. However, the third endmember is quite different. Its hydrocarbons may have come from the source rocks of the Permian Lower Wuerhe Formation or the source rocks of the Fengcheng Formation under different lithofacies and sedimentary environments. The study area is dominated by hydrocarbons that accumulated from the Fengcheng Formation. Although the proportion of hydrocarbons generated in the late stage is not high, it plays a very important role in hydrocarbon migration and accumulation. This comprehensive comparative study shows that the chemometric method can play an important role in calculating the proportion of mixed-source oil and in endmember analysis.