Expanding Of Sedimentary Facies And Sand Body Of The Xujiahe Formation In Bazhong-Tongnanba Area,Northeast Sichuan Basin

Based on field outcrop,drilling geology,logging and seismic data,and analytical data for heavy minerals of the research aera,this paper illustrates provenance and depositional system,sets up the sequence stratigraphic framework and reveals expanding characteristics of sedimentary faces and sand body of the Xujiahe Formation in the Northeast Sichuan Basin.The following conclusions are drawn:(1)The Xujiahe Formation devrlops several sources and main material source directions are Longmen Mountain from the Northwest,Micang Mountain from the Northeast and Daba Mountain from the East.(2)The Xujiahe Formation can be devided into 3 super long sequences: Xu1 Segment,Xu2-Xu3 Segment and Xu4-Xu5 Segment.5 long sequences: Xu1 Segment,Xu2 Segment,Xu3 Segment,Xu4 Segment and Xu5 Segment.17 medium sequences: MSC1-MSC17.(3)Xu1 Segment,Xu3 Segment and Xu5 Segment belong to offshore lake and shallow lake facies and develop mudflats and bank bars and swamp deposit such as carbargilite and thin coal beds in local areas.Xu2 Segment and Xu4 Segment belong to braided river delta front subfacies and develop underwater distributary channel and mouth bar.(4)The sand body of the Xujiahe Formation mainly develops in Xu2 Segment and Xu4 Segment.In Yuanba area,the sand body mainly develops in Xu2 Segment and Xu4 Segment.In Bazhong and Tongnanba areas,the sand body mianly develops in Xu4 Segment.