In the ultra-high water cut stage, unconsolidated sandstone reservoirs suffer from severe reservoir property time-variation, streamline solidification, and inefficient water circulation. To tackle these problems, this study takes Chengdao Oilfield Block 1G as an example and establishes a dynamic geological model considering permeability time-varying characteristics based on logging, core, and production data. The flow field intensity index and streamline solidification rate are introduced to quantitatively characterize the preferential flow channels and high water-consumption zones. Results show that long-term water flooding increases the average permeability by 26.88% and expands the interlayer permeability ratio from 10.33 to 19.00. The streamline solidification rate reaches 75%, forming obvious “short-circuit” circulation. Three remaining oil enrichment patterns are identified, which are mainly controlled by sedimentary microfacies, structural highs, and well pattern control. A differential regulation strategy including 3D well pattern reconstruction and streamline diversion is proposed. Field prediction indicates that the cumulative incremental oil can reach 410,000 tons and the recovery factor is enhanced by 1.3%. This study not only reveals the dynamic evolution mechanism of flow field under water-rock coupling effects but also provides a practical technical system for flow field regulation and remaining oil tapping in similar offshore ultra-high water-cut unconsolidated sandstone reservoirs.
Ma et al. (Tue,) studied this question.