Objective The reservoir has entered a high water-cut development stage, facing challenges such as a sharp increase in water cut, and difficulty in enhancing and maintaining oil production. The coordinated development of well pattern infilling and chemical flooding is an important method to further enhance oil recovery (EOR) of high water cut reservoirs.

Method Firstly, the differences in EOR using chemical flooding with well pattern infilling under various development modes through plate sand-packed model experiments were investigated. Secondly, numerical simulations were conducted to analyze the impacts of multiple factors on the development effect. Finally, a case study was conducted on a typical block within the field.

Result The well pattern infilling enabled heterogeneous fluids to uniformly enlarge sweep efficiency and displace remaining oil, reducing the formation and propagation of preferential flow channels. With the commissioning of new wells, areas previously inaccessible to injected fluids can be forcibly mobilized to utilize residual oil, allowing chemical flooding systems to achieve EOR effects across a broader scope. The stronger the reservoir heterogeneity, the greater the EOR potential through well pattern infilling-chemical flooding. Increasing well pattern density and reducing well spacing enhance interwell connectivity, facilitating more comprehensive remaining oil mobilization. After the adoption of a 150 m × 75 m arranged well network in the Q block of the G oilfield, the streamline density in edge areas significantly increased, remaining oil was further extracted, and the maximum EOR reached 13.3%.

Conclusion Well pattern infilling-chemical flooding achieves dual benefits: well pattern infilling improves reservoir control and interwell connectivity, while chemical flooding efficiently displaces remaining oil in unswept regions. This synergistic approach further enhances oil recovery in high water-cut reservoirs.