一种新型水驱特征曲线关系式的理论推导

以中含水阶段油水相对渗透率比与含水饱和度成半对数直线关系为基础,结合贝克莱-列维尔特等饱和度面移动方程,利用物质平衡原理,推导出一种含水率与累积产液量关系的水驱特征曲线。剖析了该曲线特征,阐述了新型水驱特征曲线先减后增主要是由含水率对含水饱和度导数的多值性造成的,并且通过理论证明应该在含水率大于50%以后寻找水驱特征曲线的直线段,与传统经验认识相一致,同时提出如何合理选取线性回归起始点以提高预测精度。实例证明,该水驱特征曲线对于油田生产开发指标预测具有一定的实用性。

Theoreticalderivation of a new water flooding characteristic curve relationship

Based on the semi-logarithmic linear relationship between oil-water relative permeability ratio in medium water-bearing period and water saturation,a new kind of water-drive characteristic curve including water cut and cumulative liquid production was derived using isosaturation surface moving equation proposed by Buckley-Leverett and material balance principle.By analyzing the characteristics of the curve,the reason why the water-drive characteristic curve trend reduced at first and then increased later is due to the multiple values of water cut derivative on water saturation.The conclusion that the linear part of water-drive characteristic curve should be looked for after water cut is greater than 50%,which is consistent with the traditional experience. At the same time,the method of how to choose the start point of linear regression to increase the prediction accuracy was also proposed.The calculation results of actual example indicate that the new kind of water-drive characteristic curve has a certain practicability for the prediction of oil field production and development indices.