A new water flooding characteristic curve at ultra-high water cut stage

Abstract

A large number of field practices show that the water flooding characteristic curve will appear up-warping phenomenon in ultra-high water cut stage, and the conventional water flooding characteristic curve is difficult to accurately characterize. In this work, a new expression of oil–water relative permeability ratio (Kro/Krw) and water saturation (Sw) is proposed based on the statistical analysis of experimental data of oil–water relative permeability at high displacement multiples. The new expression has a simpler form and fewer unknown parameters. The results show that the expression can accurately fit the later section of the conventional relative permeability ratio curve, and the correlation coefficient is above 0.996. On this basis, a new type of water flooding characteristic curve suitable for the whole process of water flooding reservoir development is established by combining the reservoir engineering method. Numerical simulation and field application show that the new curve has higher accuracy and wider applicability than conventional curve. The prediction error of recoverable reserves calculated by the new curve is only 0.22%, and the error of geological reserves is less than 5%. According to the comparison between the actual data and the predicted data, the actual cumulative oil production is 2.579 × 106 t, the predicted by the new curve is 2.569 × 106 t, the actual ultimate oil recovery is 50.235%, and the predicted is 50.04%. The predicted value is consistent with the actual one. It provides a more reliable method to accurately predict reservoir development indexes and guides the oilfield’s subsequent decision-making.