Abstract: Single-layer thick sand reservoir is developed in the ZH5 block of shallow water area, Dagang Oilfield, but the current exploitation effect is poor. Therefore it is urgent to study on interbeds to search for unaffected areas by water injection and tap the remained oil. The interbeds in the study area mainly fall into muddy and petrophysical interbeds by the effective identification methods of porosity-permeability intersection and logging curve. The vertical corresponding relationship of interbeds is poor; while the horizontal distribution characteristics are controlled by those of sedimentary microfacies, mainly developed on the side of beach bar sedimentation. The muddy interbeds distribute in bands along the central-south of the block. The petrophysical interbeds are in unstable platy distribution. Through sealing the water flooded layer of ZH29-29 well, the water controlling effect is good.