Abstract This paper evaluates the long-term impact of proppant size selection on hydraulic fracturing performance in the BSO field, where the target formations are characterized by low-quality, ductile reservoirs. Initially, 12/18 mesh proppant was used in over 40 wells, before shifting to 20/40 mesh based on expert recommendation to avoid potential proppant embedment. Following suboptimal results with 20/40 mesh, a full technical lookback was conducted to determine the optimal design direction for future development. Hydraulic fracturing design involves key inputs, including proppant size, fluid type, pad ratio, and pumping schedule, alongside reservoir data. In this study, all parameters were held constant except proppant size. Performance comparison was conducted between ~30 wells with 20/40 mesh and ~40 wells with 12/18 mesh. Evaluation metrics included normalized cumulative production, productivity index (PI), pump run life, and proppant flowback behavior. Fracture geometry vs. productivity index (PI), was analyzed to determine the stimulation efficiency of each design. Furthermore, Pressure Transient Analysis (PTA) was performed on 5 older wells with 12/18 mesh to detect potential proppant embedment. Wells fractured with 12/18 mesh proppant demonstrated more stable production performance and superior pump reliability compared to those with 20/40 mesh, which frequently encountered flowback issues and pump failures. PTA analysis confirmed no significant proppant embedment in the 12/18 wells, with consistent fracture lengths observed after a decade of production. The geometry analysis further revealed that 12/18 mesh designs achieved effective stimulation with shorter fractures and lower total proppant volumes, whereas 20/40 mesh required longer fractures and significantly more proppant to attain comparable productivity. These findings suggest that larger proppant provides better conductivity in ductile formations, enabling fracture geometry and material optimization without sacrificing well performance. This study offers a data-driven validation of proppant sizing decisions in ductile, low-quality reservoirs—areas where conventional wisdom often dominates design choices. By integrating PTA diagnostics and production analytics, the paper provides a practical framework to improve fracturing efficiency and reduce material requirements in future developments.