Abstract: Bohai X oilfield has entered the late stage of high water cut development, and the oil-water relationship is complex. Aiming at the problem of uneven vertical operation, artificial physical simulation core is used to carry out the research on the distribution regularity of residual oil in thick oil layers under the production conditions of different injection positions of oil and water wells. The results show that the ultimate recovery is the highest when the injection wells perforated at the top and the production wells perforated all. The optimized perforation scheme can change the flow direction of oil and water, but the residual oil is still mainly concentrated at the top of the reservoir under the influence of gravity differentiation. The research results were applied to oilfield production, in which X1 well produced 200 m3 oil per day after it was put into production, and the period of waterless recovery was as long as 2 years. This method has certain effect on improving the water flooding effect of thick oil layer and can be appropriately popularized in offshore oilfield.