Abstract: The physical characteristics and genesis of the upper part of the 3rd member of Eocene Shahejie Formation (E₂s₃^u) in Kenli L oilfield of Laizhou Bay sag in Bohai Bay basin were clarified by using a variety of analyses and testing methods, such as casting thin sections, SEM, X diffraction, pore permeability test and drilling test, combined with the related research results of regional tectonic setting and sedimentary system, the physical properties control factors of E₂s₃^u were discussed, and applied in oilfield water injection development. The results show that:the reservoir of E₂s₃^u with the average porosity of 28.9% and the average permeability of 762.7×10^-3μm² belongs to "high porosity-permeability" reservoir,the reservoir space is mainly primary intergranular pores with secondary intergranular pores, mold holes, and micro-fractures; the average width of the micro-fractures is 180 μm, the existence of the micro-fractures provided a highly efficient seepage channels, which makes drilling test pore permeability is obviously better than that through core test. The physical properties of high quality reservoirs are mainly affected by system tract, fault activity and burial, the thick net sandstone under transgressive system tract is the material basis of forming high-quality reservoirs; the developed micro-fractures improved seepage capacity; rapid burial slowed the drainage of reservoir pore water and the decline of reservoir physical properties. Based on high-quality reservoir development characteristics and production dynamic data, optimizing layered allocation of water wells, reducing uneven water flooding in the horizontal and vertical directions, and then Kenli L oilfield achieved balanced displacement.

Key words: high quality reservoir, micro-fracture, control factors, E₂s₃^u, Kenli L oilfield