Abstract: After nearly 30 years of development, CB oilfield has been at the late stage of development with high water content. In order to recognize the distribution of residual oil,guided by the theories of high resolution sequence stratigraphy, different classes of base level cycle were identified and compared by making full use of cores, drilling and logging data. Dongying formation is divided into one long-term, four middle-term and eleven shortterm base level cycles. The results indicate that in the early stage of base level rising and late stage of base level dropping, the sedimentary characteristics are mainly of underwater distributary channel and river mouth bars, the sand body has large thickness and good reservoir properties, in the late stage of base level rising and early stage of base level dropping, the sedimentary characteristics are mainly of river channel bar and subsea interdistributary bay, the sand body has little thickness and poor reservoir properties; in the middle stage of base level rising or dropping, the sedimentary characteristics are mainly of underwater distributary channel and river channel bar, and the thickness and properties of sand body is medium. Under the control of the base level cycle, the residual oil is mainly in the physical mutated area, the uncontrollable zone of well network, the inter-well detention zone and the fault nearby regions.