Study on Subdivision Waterflood Technical Policy of Low Permeability Reservoir in Middle-High Water Cut Stage

The reservoir is developed by reverse nine-spot well pattern and synchronous waterflood method. Because the injection-production ratio of reservoir is high in early stage, the oil well production is relatively stable. However, due to the sedimentary environment, reservoir fractures and interlayer heterogeneity, the single layer water breakthrough is serious. The reservoir reaches the middle-high water content stage quickly, resulting in poor waterflood development. In order to improve low permeability reservoir waterflood development in middle-high water content stage, the waterflood technical policy optimization is carried out based on reasonable pressure keeping level, optimal injection-production ratio and optimal water injection intensity. According to the actual production situation of well group, the feasibility of cyclic water injection and liquid production increasing method is demonstrated. The results show that the reasonable pressure keeping level is 85%, the optimal injection-production ratio is 1.1–1.2, the optimal water injection intensity is 1–2 m3/m \(\cdot\) d, the optimal half cycle of water injection is 1–2 months, and the optimal liquid production increasing time is water content of 60%–85%. After the field popularization and implementation, the reservoir water content decreased by 1.8 percentage and the natural decline decreased by 3.9 percentage, which provides theoretical basis and application effect for subdivision waterflood development of low permeability reservoir in middle-high water content stage.