Sedimentary Environment Evolution And Reservoir Prediction Of The Jurassic Badaowan Formation In The Chepaizi Uplift And Its Periphery,Junggar Basin

The Jurassic Badaowan Formation in the Chepaizi Uplift and its periphery is the main source rock layer as well as the important oil-gas accumulation layer in the northwestern margin of Junggar Basin.Through several sequence stratigraphy and sedimentary facies analysis methods,the sedimentary environment evolution of the Badaowan Formation in the study area was analysed,and the favorable reservoir was predicted,combined with the previous research achievements.The results show that the main source directions were SE and E during the Badaowan Formation depositing period in the study area.The paleotopography was high in the west and low in the east,and the sedimentary center was located in the northeast of the study area.In the Badaowan Formation,3 third-order sequences(LSQ1-LSQ3)and 6 forth-order sequences(MSQ1-MSQ6)can be classified.The early depositing period of MSQ1,MSQ3,MSQ5 and the maximum flooding period of LSQ2,LSQ3 were the key periods for reservoir development.In these periods,the sedimentary environment had significant control effects on the favorable reservoir distribution.During the depositing period of the Badaowan Formation,there were mainly alluvial fan facies,fan delta facies,braided fluvial facies,braided fluvial delta facies and lake facies.The Badaowan Formation deposited in a tectonically stable lake-transgression period with small scale lake-regressions,which caused the oscillating migration of the sedimentary system toward the land.The favorable reservoirs are mostly located in LSQ1 and MSQ5,followed by MSQ3.The most favorable exploration targets are located in the northwest part of the study area.