Sedimentary microfacies in the upper submember of the fourth member of the Shahejie Formation in the Yibei Oil Field, Shandong

The D43 block in the Yibei Oil Field lies in the slope zone of the northeastern Yihezhuang uplift in the Jiyang depression. Controlled by the regional tectonic movement, the multiphase regional unconformity, widespread stratigraphic overlap and erosion are observed in the study area. The fault-block and lithologic oil reservoirs formed in the complex fault-thrust anticline are believed to have great petroleum exploration potential. The present paper focuses on the tectonic evolution, sedimentary microfacies and stratigraphic division of the upper submember of the fourth member of the Shahejie Formation in the D43 block, Yibei Oil Field in the light of well logs, seismic and analytical data. The results of research show that the principal source of detritus lay to the ancient uplift in the southwest. Horizontally, the upper submember of the fourth member of the Shahejie Formation is mostly built up the fan delta facies include the fan delta front and littoral-shallow lake beach/bar subfacies. Vertically, there are gradations from the fan delta to the littoral-shallow lake beech-bar depositional systems. The sedimentary microfacies in the upper submember of the fourth member of the Shahejie Formation including the subaqueous distributary channel, channel-mouth bar, sandbar and carbonate shoal microfacies, which are interpreted as the good oil reservoirs. The bathyal lake oil mudstones and oil shales in the third member of the Shahejie Formation occur as good source rocks and cap rocks of the fourth member of the Shahejie Formation.