AbstractIn this paper, an integrated numerical technique is presented to implement global optimization of displacement efficiency in hydrocarbon reservoirs. This technique chooses the net present value (NPV) as an objective function, which accounts for production- and injection- performance as well as reservoir performance. The flowing and various artificial lifting methods are incorporated into the production performance models, which have been successfully applied in more than forty oil fields. Meanwhile, the reservoir geological model is improved by continuous monitoring and surveillance. Then the objective function is maximized to generate the optimum field production-injection strategies at different development stages using a hybrid genetic algorithm (GA). Such an integrated technique can maximize the displacement efficiency in a fixed well pattern and/or an oil field under different practical constraints. This technique is applied in a water-alternating-gas (WAG) miscible flooding reservoir, and the field performance has shown that the displacement efficiency is significantly improved and the production-injection rates are well controlled. The field water-cut remains low and stable, though the gas-oil ratio is slightly higher than the original ratio. This method can be applied to develop the optimum production- and injection- strategies in a hydrocarbon reservoir so that the displacement efficiency is maximized and the reservoir life is extended.