Quantitative Characterization of Remaining Oil in the Mid-Late Development Stage of Typical Jurassic Edge-Water Layered Reservoirs in Ordos Basin

To enhance the accuracy of remaining oil characterization during the mid-late development stage of Jurassic reservoirs in the Ordos Basin, a comprehensive multi-method quantitative analysis was conducted using a typical edge-water layered reservoir in the older development area of the Yan’an Formation in the Hujianshan Oilfield. By integrating production performance analysis, reservoir engineering, and numerical simulation, a systematic approach was adopted. First, dominant waterflooding displacement directions were identified through waterflooding behavior analysis. Second, the sweep efficiency and displacement range were delineated based on waterflooding mechanisms and patterns, and the remaining recoverable reserves per well were estimated. By subtracting the recoverable reserves in the water-swept zones, a remaining oil distribution map reflecting actual reservoir development characteristics was constructed. Finally, combined with the current remaining oil distribution predicted by the numerical simulation method, the remaining oil enrichment area is finally optimized. The results indicate that the distribution of remaining oil is primarily influenced by the structure, water flooding of injected water, single well recovery extent, interlayers and so on. The enriched remaining oil zones are found in structural highs, areas flanking uneven waterflood fronts, localized regions with reserve loss due to casing integrity issues, and unswept zones in reservoir highs. This integrated quantitative characterization approach offers valuable guidance for development adjustments in the mid-late stages of similar edge- and bottom-water reservoirs.