In order to reveal the sedimentary facies distribution and evolution pattern of the 2

nd

Member of Shahejie Formation in Bonan Subsag of Bohai Bay Basin and to find new target areas for future oil and gas exploration in Zhanhua depression

we classiffied and correlated the sand groups of the 2

nd

Member of Shahejie Formation

delineated the distribution of sedimentary facies in different historical periods and summarized the sedimentary evolution pattern based on the comprehensive study of core

logging and seismic data.Four sand groups were identified in the 2

nd

Member of the Shahejie Formation in Bonan Subsag.They overlap each other southwards and get larger progressively in distribution area.Near the uplift zone around the Bonan Subsag

fan delta front deposits are predominant and consist mainly of underwater distributary channel microfacies

followed by channel mouth bar and subaquatic interdistributary embayments.Inside the Bonan Subsag

shore-shallow lacustrine beach bars are predominant and can be divided into three types with different distribution patterns according to their origin

namely normal sandy beach bars

sandstone and carbonate mixed beach bars and storm beach bars.The sedimentary evolution of the 2

nd

Member of Shahejie Formation features in continuous enlarging of lake basin

progressive expanding of sedimentary range.decreasing of fan delta distribution area

and increasing of beach bar distribution area.