基于Petrobras方法含水综合IPR曲线公式的修正

提出并推导了含水油井综合IPR曲线的两个新公式，并推导了综合IPR曲线上最大产油量处斜率的精确表达式。确定综合IPR曲线分为两个步骤：一是计算采液指数，二是计算任意流压──产量点。Petrobras方法第一步骤采用产量加权平均法，第二步骤使用流压加权平均法，故理论上不严格，实际上存在较大的误差。文中提出的第一种方法是两个步骤全采用产量加权平均法，第二种方法是两个步骤全采用流压加权平均法，并推导出了采用流压加权平均法时在综合IPR曲线的最大产油量处斜率的精确表达式。该表达式与原式比较极为简单。最后对三种方法的计算结果进行了比较和讨论，利用新公式可以更精确地进行油井产能的预测。

The Modified Formulas for the Composite IPR Curves Based on Petrobras Method

This paper provides two improved methods about the composite IPR curve on petrobras method. It is divided into two steps to determine the composite IPR curve from the test data. The first step is to calculatethe productivity index. The second step is to predict the composite IPR curve. Petrobras method adopts the flow rate -weighted average at the first step and adopts the flowing bottom hole pressure-weighted average at the second step. It is not strict in theory and its result is not correct in practical application. This paper provides two new methods. The first method adopts the flowing bottom hole pressure-weighted average in two steps. The paper also derives the accurate expression of the slope of the composite IPR curve at the point of the maximum oil flow rate. The new expression is very simple compared with the old one. At the end,the calculating results of three methods are compared and discussed- New formulas can be used to accurately predict the composite IPR curve.