Lithologic reservoir exploration of Es~3 flexure slope break systems in Qibei slope of Qikou sag,Bohai Bay,China

Starting off with the analysis of the sedimentary background of slope belts and paleogeomorphology,this paper discusses the slope-break system characteristics and the relationship between sand stone distribution and oil-gas reservoir in high resolution sequence stratigraphic unit by comprehensively analyzing the 3-D seismic,logging,core,sand distribution and reservoir characteristic data.In the typical oil-rich Qikou sag of Bohai Bay Basin,there develops a three-grade slope-flat zone on the whole because of differential settlement,fault block tilt and basement structure.In the low systems tract of Es3-2,there develops an erosional-flexure slope break system including an erosional slope break zone which is located on the arch edge of first-grade slope-flat zone in the high part of slope.A classical flexure slope break zone develops in the mid-low part.The exploration and research indicate that the sandstone supplied by inner basin provenance,delivered by groove,controlled by slope-flat,accumulated by type of provenance of Es3 in the slope.In Es3 three third-order cycles and seven fourth-order high resolution cycles can be identified vertically and each layer overlaps upward the slope in order.Braided river delta front,offshore submerged fan and shallow lake dam bar and related lithologic traps develop in the slope break zone at all levels.All these lithologic traps adjoin the source rocks and have dominant migration,are accumulated,highly overlapped and connected each other.They are the important lithostratigraphic reservoir exploration targets in the slope region.