Abstract:

Oils from intervals in the Chepaizi areas of Junggar basin are divided into two groups based on physical properties, chemical components, biomarkers and stable carbon isotope composition of the oils. One group includes the oils trapped in the reservoir beds of Jurassic and the beds below Jurassic (named as the lower series of strata oils), and another one includes those in reservoir beds of Cretaceous and the beds above Cretaceous (named as the upper series of strata oils). The oils in same group have similar physical and chemical characteristics, while those in different group are of differences in these characteristics. The lower series of strata oils have the same source and come from the Permian source rock, and the upper series of strata oils have the same source as well and are from mainly the Jurassic rock. Results of oil-sources division and correlation for these oils by making use of nitrogen compounds distributions are completely identical with those by density, viscosity, group composition and other biomarker parameters just mentioned above, indicating that nitrogen compounds could be used in oil-sources division and correlation. Finally, oil-pool forming model is established for the Chepaizi uplift. it is just next to sag areas with favorable structural location, and has abundant oil-gas resources. The uplift is the dominant destination for hydrocarbon migration. Multiple faults and uncomformable surfaces of this area form excellent migration pathways. Lateral migration happened when oil and gas migrating vertically along faults encountered uncomformable surfaces. Thus in the space Z-chart or a ladder migration routes form and finally multiple oil pool types and hydrocarbon-bearing layers are formed.

Key words: biomarker, nitrogen compound, oil, geochemistry, oil source, oil reservoir formation, Chepaizi swell, Junggar basin