GEOCHEMICAL STUDY OF OIL/GAS MIGRATION ON THE NORTHWEST EDGE OF JUNGGAR BASIN

Taking the oil pool profiles of No.8-No.6 regions on the upper and lower plates of Ke-Wu Fracture on the northwest edge of Junggar Basin for example.thirteen Permian-Jurassic crude oils are sysematically sampled in this paper,and the physical and geochemical properties of crude oils are analysed, it is revealed that the crude oil density of No.8-No.6 regions gradually increases and polar compounds, low-molecular isohydrocarbons and pregnanes in the components of biomarkers are gradually enriched along the oil pool profiles ;besides.varied systems could exist during migration,that is to say.low carbonate hydrocarbons are caused molecular diffusion by decreases in temperature and pressure and the relative openness of systems,high carbonate polycyclic naphthenes are led to the frac tional distiolation of compounds due to stratiform segregation, and microbial degradation occurs in shallow reservoirs. The geochemical characteristics of oil/gas migration rule out the possibility that there are sourcelands within oil areas and further evidence that Lake Ma Depression is the oil source area of Ke-Wu Fault Terrace zone.