用甲、乙型水驱曲线预测可采储量的结果分析

Comparison of analysis results by using two types of water drive curves for predicting unequal recoverable reserves

由于很多油田用乙型曲线预测水驱可采储量的相对误差大于用甲型曲线预测的相对误差,因此,普遍选用甲型曲线的预测结果.通过对甲型、乙型曲线表达式的推导和储量计算公式的对比可知,用乙型曲线预测储量结果是甲型曲线预测结果的最高极限,用甲型曲线预测的可采储量值小于用乙型曲线的预测值.油田实例还表明,也存在用乙型曲线预测误差小于用甲型曲线预测误差的现象,而且,即使选用相同数据点,2者预测值也可能相差较大.因此,用2种曲线预测储量不同的原因在于它们的表达式不能严密地互相推导,忽略常数C造成的.2者对制定油田生产规划都有一定的参考价值.

The predicted error of recoverable reserve by using type A of water drive curve(lgW p=A 1+B 1N p) in some oilfields is smaller than that by using type B(lgR WO =A 2+B 2N p), so the type A is always selected in many oilfields. The formulas for expressing two curves are different. The value of the recoverable reserve predicted by type A curve is lower than that by type B. This paper gives a method for getting expression of type A water curve from the expression of type B. The unsteady performances of two water drive curves for predicting recoverable reserves are described by taking an oilfield as an example. Their errors are also analyzed. Result of study shows that the difference of recoverable reserve predicted by the use of two curves may result from a constant ignored in the expressions. The results of prediction with type A and B are all referential to planning oilfield development.