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Abstract This study focuses on the development of complex fluvial bottom-water reservoirs in Bohai Bay. The reservoir architecture is significantly influenced by channel migration, resulting in pronounced variations in channel width (80–700 meters), reservoir thickness (5–13.5 meters), and rapid lateral facies changes. These features contribute to strong reservoir heterogeneity. Early development efforts were constrained by limited geological data—only two exploration wells—and low seismic resolution, making it difficult to define reservoir geometry and interbedded thin layers. Furthermore, the multi-phase, interwoven channel system introduces complexity in reservoir connectivity and fluid flow characterization. The presence of bottom water increases the risk of early water break through, making it challenging to achieve high drilling success rates in high-quality zones. To address these challenges, a phased "near-to-far, deep-to-shallow" development strategy was adopted. Geological understanding was progressively expanded outward from the exploration wells. Deeper landing sections were utilized to enhance structural interpretation of upper formations and assess overlying channel sand body risks. An oblique channel drilling strategy was implemented to maximize sweeping efficiency and contact with favorable facies. Additionally, a Deep Azimuthal Resistivity (DAR) tool was deployed to identify real-time structural and lateral variations within a 9-meter radius around the wellbore. This enabled dynamic well trajectory adjustments to maintain optimal reservoir contact. During this phase, 14 horizontal wells were drilled. The DAR tool enabled real-time resistivity imaging, guiding precise trajectory adjustments and improving contact with high-quality reservoir zones to over 90%. The tool also supported informed well completion decisions and injection-production pattern optimization. Notably, Well X12H achieved a 98% reservoir encounter rate over a 780-meter horizontal section, setting a record in Bohai Bay and contributing to overall reservoir production exceeding design expectations by 100%. Additionally, logging and DAR data enhanced geological model resolution, clarified reservoir boundaries, and confirmed marginal reserves. This led to the identification of four additional infill well locations, further improving field development efficiency. This study demonstrates that integrating a phased development strategy with advanced deep reservoir mapping significantly improves well placement accuracy and reservoir contact rates in fluvial bottom-water systems. The approach provides a replicable model for boosting reserves and production in similarly complex, data-limited reservoirs. It also highlights the value of real-time geosteering in overcoming connectivity uncertainties and early water breakthrough risks. Furthermore, the high reservoir exposure rates and proactive well placement strategy also lay a solid foundation for late-life brownfield optimization, effectively delaying water breakthrough, extending production plateaus, and reducing future sidetrack demands, collectively enhancing ultimate recovery in a mature asset context.