Abstract: Water drive curve methods are the important approaches for prediction of oilfield recoverable reserves by waterflooding process in China. The effective application of such methods depends on the reliability of linear stage selection and the rationality of limit watercut determination. However, for waterflooding oilfields with variable mobility, it is regulated to only take water-cut of 98% as basis for prediction of recoverable reserves in accordance with existing industry standard. This measure is not only improper, but also short of theoretical basis. Based on the previous study achievements by the author and the varied technical and economic conditions, this paper proposes the method for determination of economic limit water-cut to predict economic recoverable reserves of oil fields that have entered into middle-high water-cut stage characterized by production decline. The case study indicates that this method is practical and effective.

Key words: waterflooding oil field, water drive curve method, prediction, forecast, economic limit water-cut, economic recoverable reserve