基于甲型水驱规律曲线的表征方法改进

甲型水驱曲线可以用泰勒展开方法近似成双曲递减曲线来研究油藏产量递减规律，该方法仅在含油率初值邻域内具有二阶精度，导致在产量预测后期误差较大。为了更加精确地建立甲型水驱曲线与Arps递减规律之间的联系，提高甲型水驱曲线预测油田分年产量的计算精度，通过对常用的水驱曲线递减率公式进行对比、分析，提出了甲型水驱曲线递减率的幂函数拟合表征方法，利用方差函数最小值分析方法得到了甲型水驱曲线在不同含水阶段含油率幂函数拟合的误差。结果表明：含水率越高，含油率幂函数拟合方法的误差越小；当含水率大于70%时，甲型水驱曲线含油率幂函数拟合方法不仅在含油率初值邻域内拟合较好，且在全局内拟合最优。改进的含油率幂函数拟合方法可以用来快速预测甲型水驱曲线的产量剖面，实例应用表明该方法计算精度较高，适用于符合甲型水驱特征且含水率大于70%的油藏的产量预测。

Improvement of characterization method based on type A water drive curve

Type A water drive curve can be approximated to hyperbolic decline curve by Taylor expansion method to study the law of reservoir production decline. This method only has second-order precision in the neighborhood of initial oil cut, resulting in a large error in the late production prediction. In order to establish the relationship between the type A water drive curve and Arps decline law, and to improve the calculation accuracy of forecasting annual production of oilfields by the type A water drive curve, by comparing and analyzing the decline rate formulas of commonly used water drive curves, an oil cut power function fitting method for the decline rate of the type A water drive curve was proposed. The error of the oil cut power function fitting in different water cut stages was obtained by using the method of minimum value analysis of variance function. The results show that the higher the water cut is, the smaller the error of the oil cut power function fitting is, and when the water cut is greater than 70%, the oil cut power function fitting of the type A water drive curve not only fit better in the neighborhood of initial oil cut but also fit best in overall prediction time. The improved oil cut power function fitting method can be used to predict the annual oil production of the type A water drive curve quickly. The application proves the high accuracy of this method, and it is suitable for predicting the production of reservoirs with water cut greater than 70% which conform to the characteristics of type A water drive.