Most conventional oilfields in Eastern China with waterflood operations have reached ultra-high water cut in recent decade. The high water injection demand and produced water treatment cost pose significant environmental threats. Therefore, optimizing waterflood performance is key to improving production efficiency. This study performs data analysis on waterflood operations of all the oilfields operated by Sinopec across Eastern China. The production mechanisms and most effective operations for different reservoir types at diverse production stages are identified using data-driven methods. Random Forest models (RFMs) are constructed and integrated with Shapley Additive exPlanations (SHAP) analysis to quantify the weights and patterns of key geological and engineering features. A comparison of the estimated ultimate recovery factors for different blocks shows that geological factors play dominant roles in medium-to-high permeability reservoirs while development parameters are more critical for low-permeability reservoirs. The analysis of temporal data regarding field development and production history is conducted to select oil production-increasing operations in blocks. The results show that the most influential field operations vary for the diverse production stages, and well patterns should be carefully designed to improve production efficiency and reduce ineffective water circulation.

The immiscible displacement behavior in porous media is crucial for oil recovery and subsurface remediation, yet how wettability influences this process across different pore structures remains unclear. Using a color-gradient lattice Boltzmann model, this study investigates immiscible displacement dynamics in porous media. Heterogeneous porous structures with various degrees of permeability were reconstructed using the quarter structure generation set algorithm, and wettability effects were analyzed with the contact angle set in the range of ${30}^{\circ }$ to ${150}^{\circ }$. The numerical results showed that porous heterogeneity greatly affects the displacement efficiency via permeability-dependent flow pathway optimization. Enhanced efficiency was observed in high-permeability media through low-tortuosity channels, whereas low-permeability systems exhibited reduced efficiency due to capillary trapping in pores with lower flow capacity. Wettability alters displacement patterns via capillary forces – under hydrophilic condition, the displacing fluid preferentially enters smaller pores. Fractal dimension and Euler number were used to quantify flow heterogeneity, revealing that increased permeability reduces flow complexity and improves connectivity. Moreover, permeability heterogeneity and wettability interact to disrupt classical linear flow responses, leading to non-monotonic efficiency trends in low-permeability systems. These findings highlight the importance of pore-scale multiphase flow in heterogeneous media and offer new insights for predicting wettability effects in subsurface flows.