Reservoir heterogeneity plays a crucial role at various stages of oilfield development. As one of the key factors influencing heterogeneity, interlayers significantly control the distribution of pressure and oil-water phases within the reservoir during the high water-cut stage. The upper part of the Cretaceous Quantou Formation Member 3 to Member 4 in the Toutai Oilfield belongs to a shallow-water fluvial-delta depositional system. To further guide the tapping of remaining oil potential in the oilfield, a study on reservoir interlayers was conducted. Through integrated analysis based on core-log relationship comparisons, three types of interlayers in the Fuyu oil layer were identified: argillaceous, physical property, and calcareous interlayers. The genesis of each type was analyzed, and electrical spider plot identification criteria for different interlayer types in the study area were established. The study also investigated the distinct impacts of point-bar lateral accretion interlayers in meandering rivers and interlayer stability on remaining oil distribution, thus providing a basis for the detailed characterization of reservoir geological features and research on remaining oil distribution.