Depositional System Frameworks of the Jurassic in Junggar Basin

The Jurassic is one of significant oil-bearing strata in Junggar basin with relatively well-reserved sequences, various sedimentary facies and diversiformdepositional systems. Based on outcrop profiles, well data, logging data and seismic data, the Jurassic can be divided into seven sequences consisted of alluvial fan, stream, delta, fan delta, lacustrine and swampfacies which assemblaged in the tracts orderly. Research on provenance and lithofacies paleogeography indicates that there were eight sedimentary systems in the Jurassic in the Juggar basin, i.e., alluvial fan-braided stream-meandering stream-delta-lacustrine depositional system off Kalamay Mountains, delta fan-lacustrine depositional system in Wulungu, braided stream-meandering stream-delta-lacustrine depositional system off Delun Mountains, alluvial fan-braided stream-delta-lacustrine depositional system off Halaalate Mountains, alluvial fan-braided stream-delta-lacustrine depositional system in Cheguai, meandering stream-delta-lacustrine depositional system off Sikeshu Mountains, alluvial fan-braided stream-delta-lacustrine depositional system off Yilinhebier Mountains, meandering stream-delta-lacustrine depositional system off Bogeda Mountains. Among the eight depositional systems the depositional system off Kalamay Mountains was well developed in some sequences. These depositional systems controlled the favorable reservoir development of the Jurassic in Juggar Basin.