Sequence Stratigraphy Framework Analyses of the Neogene Shawan Formation in Chepaizi Area,Junggar Basin

Based on the identification features of continental stratigraphic sequences on seismic profiles and wire-line logs,synthetic seismograms and the characteristics of lithologic combination,the Neogene Shawan formation is divided into one second-order sequence and two third-order sequences.The third-order sequence Ⅰ is braided as a delta front sequence,while the sequence Ⅱ is a lacustrine sequence.Each third-order sequence according to its characteristics can be divided into three system tracts:low stand,transgressive and high stand system tracts.Based on the identification and correlation of sequence stratigraphic unit,and according to the characteristics of the stratigraphic sequences,the tectonic evolution history and the variation of strata thickness,the sequence stratigraphy framework is shown to have a great,complete and stable thickness in the study area of south-east,and a thinner,incomplete one in the north-west.A preliminary analysis is made on the relationship between sequences and oil-gas exploration potentials,and exploration priorities and goals in each sequences are predicted.The favorable lithological reservoirs are found to be located mainly in the low stand system tracts of sequence Ⅰ and in the transgressive system tracts of sequence Ⅱ.