Sequence Stratigraphy and Prediction of Lithologic Traps of Palaeogene in Chepaizi Area,Junggar Basin

To study the palaeogene growth and development,and distribution characteristics of sequence stratigraphic bed in Chepaizi area,the sequence stratigraphy is used with a discussion of its principle,method and technology.Based on composite analyses of seismic,drilling,well logging and outcrop data,together with interwell and log-seismic correlations,the palaeogene sequence stratigraphic classification and features are obtained with two third-scale sequences and four system tracts identified.It is shown that the structure of this area assumes a large-scale slope with a small distinct slope break,with the development of a tract of Lowstand systems under the slope break.The tract of Lowstand systems and that of Transgressive systems are divided by first flooding surface.The tract of Highstand systems is undergrown or not identified.From the tract of Lowstand systems develop diffluent rivers of fan delta and barfacies of beach.From the tract of Transgressive systems develop mudstone and siltstone in beach barfacies.Stratigraphic development is controlled by sediment sources,relic landform,climatic conditions and lake level changes.The sequence stratigraphic framework of palaeogene in Chepaizi area is established.Under the sequence stratigraphic framework,favorable sectors of oil and gas bearing are predicted in studied area,which would play an important role in the search of lithologic subtle reservoirs in northwestern margin of Jungger Basin.