As oilfield development transitions into the post-waterflooding stage—especially entering the ultra-high water cut period—the distribution of remaining oil becomes increasingly scattered, escalating the challenge of potential exploitation [1–6]. As a critical production-enhancing measure under the economic conditions of post-waterflooding, re-perforation operations integrate dynamic and static data with detailed geological research results to carefully select target wells and layers. The goal of “increasing fluid production to enhance oil recovery” is established, focusing on re-perforating lobe-shaped channel sands or narrow strip-shaped offshore dam sand bodies primarily in units below P1 [7–10]. This approach aims to improve the utilization degree of oil layers and fully tap into the potential of remaining oil. The following analysis examines the effectiveness of potential exploitation through re-perforation of units below P1 in wells of Block X in a certain oilfield [11–13]. By improving injection-production relationships, tapping into remaining oil potential, and coordinately enhancing waterflooding development efficiency, this study provides valuable insights for exploring remaining oil potential in other post-waterflooding blocks during the ultra-high water cut period.