Based on the static and dynamic combination researches about the information of cores, well logging and well production performance, the characteristic, genesis, distribution of interbeds in thick reservoir of Paleogene Shahejie Formation in Dongpu Sag and their application in potential tapping of residual oil were studied. The results showed that the interbeds could be divided into muddy, physical and calcareous interbeds according to the category and electrics character of rocks; the muddy interbed was major, the muddy and physical interbeds were formed by sedimentation, and calcareous interbed were formed by diagenesis.