Abstract: Old oilfields in China have successively entered into the middle to late stage of oil production. Affected by strong reservoir heterogeneity, large amounts of remaining oils are still resorted in the subsurface and they have laid an important material foundation for a long-term stable yield in old oilfields. However, it is a highly integrated research problem to predict potential areas of remaining oil accumulation under a high water cut condition, but attempts to make this prediction theoretically and practically have never ceased though the insight into distributional laws of remaining oils tends to be simplified. Through a study on distributional laws of remaining oils in the Pu-1 oil group of the Pubei Oilfield peripheral to the Daqing Oilfield, a new cognition was obtained, besides a common insight into potential areas of remaining oils, that an underwater distributary channel crotch in lake-facies delta front deposits could be a favorable place for remaining oil accumulation, thus, a quantitative assessment of remaining oil distributions was made based on the response of oil wells located in crotches to oil production and the effect of oil-producing potential exploitation. The study results indicated that in terms of the enrichment mechanism of remaining oils, this kind of reservoirs could be characterized by: ①a relatively larger thickness of sand body; ②well-developed interlayers; ③complex depositional structures and assemblage types; and ④a direct connection of distributary channel crotches with the main part of underwater main steam channels. The underwater distributary channel crotch is a potential location of remaining oil accumulation that has not yet been dealt with in previous studies and it is the first time to discover remaining oils accumulated in this place. Therefore, the discovery of this new type of remaining oil reservoirs is of great theoretic significance and practical value in exploiting the potential of remaining oils accumulated in reservoirs related to river-delta-facies deposits.