Abstract

Oilfield development generally goes through multiple stages of development. Different stages have different development effects and features. Waterflooding characteristic curve is one of the main methods of development evaluation and oil recovery forecast in waterflooding oilfields. The chart of relationship between water content and recovery degree is directly applied to predict recovery factor. However, the production data could not be in accordance with the curve in the chart in the course of practical application. In order to improve the precision and applicability of water drive characteristic curve charts, based on seepage mechanics and material conservation principle, waterflooding characteristic formula between accumulative oil production and accumulative liquid production was deduced. Using mathematical equation method, a new relation between water-cut and recovery degree considering different time-phased actual development data was presented and the corresponding formula of water cut increasing rate was derived. Fitting parameters by regression fitting method from the actual production data was employed as the reference value for the revised mathematical model and the corresponding water drive curve cluster was drawn based on the fitting-curve. At the same time, the method of time-phased water drive effect evaluation was presented. Results showed that recovery factor of waterflooding reservoirs predicted by improved chart is more exact and the fitting degree of water cut between calculated and actual data is better than by existing charts, demonstrating that the improved chart has strong practicability in waterflooding development effect evaluation and index forecast. Those conclusions improve the waterflooding theory and provide useful guidance for effect evaluation of water displacing, water cut calculation and oil recovery ratio prediction for different stages. The presented research content furthers the theory of waterflooding, and builds theoretical foundation for the technologies of development evaluation in waterflooding reservoirs.

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