Genesis assembly and distribution rule of deltaic front sand body in the upper series of strata in Xia'ermen oilfield

The upper series of strata in Xia'ermen oilfield is com- posed of a series of deltaic front sand body strata.Core,ge- ophysical logging and geological logging data suggest the presence of five sedimentary microfacies as subaqueous dis- tributary channel,mouth bar,sand sheet,distant sand bank and anterior slump deposit,and corresponding six sand body assemblies as incumbent subaqueous distributary channel sand body,incumbent mouth bar sand body,subaqueous distributary channel-mouth bar sand body,sand sheet- mouth bar sand body,sand sheet--subaqueous distributa- ry channel sand body,sand sheet-slump gravity flow sand body.Based on the study on sedimentary facies,from the characters of provenance supply on the basin bottom,the change of lake level and the landform of basin bottom,three kinds of sedimentary models of delta front as progradation, retrogradation and partial stacking are presented;and the temporal and spatial distribution characters of each model of sand body assembly are analyzed.Therefore,it is concluded that two sedimentary models as progradation and partial stacking are existed at the area.