Source of the Jurassic Oil in the Western Mahu Sag of Junggar Basin, NW China

In recent years, important breakthroughs have been made in the exploration of the northwestern margin of Mahu sag in Junggar basin. The estimated amount of oil deposits in this region seems to be as large as 100-million-ton lithologic reservoir. A certain scale of oil reservoirs was found in the Jurassic Badaowan formation, which indicates that the Jurassic reservoir has promising prospects for exploration. The geochemical characteristics of Jurassic crude oil and Permian source rocks and oil accumulation factors are studied in this paper. The results show that carbon isotope values (δ13C) and the biomarker parameters (γ/C30H and C24Tet/C26TT) have a good application in oil source correlation. Crude oil in Jurassic reservoir was generated from Permian Fengcheng (P1f) source rock. The main hydrocarbon expulsion period of the P1f source rock was between late Permian and middle Cretaceous. The crude oil migrated upward into the Jurassic lithologic traps through faults or superimposed sand bodies.