线性流的启动压力梯度不能用于平面径向流方程

Improper use of the starting pressure gradient of linear flow in the plane radial flow equation

启动压力梯度的物理概念及判别式是Bear于1972年在利用岩心测试资料研究达西定律的应用下限时提出来的,葛家理教授首次介绍到我国。所谓启动压力梯度,是指流体在饱和的岩心开始发生流动时的压力梯度。应当指出,线性流的压力梯度与流量成正比,启动压力梯度为常数;平面径向流的压力梯度与流量成正比,与径向半径成反比,而且,不同径向半径位置的启动压力梯度是不同的。有关学者将线性流启动的压力梯度及判别式直接用于平面径向流方程的正确性值得质疑。笔者对线性流和平面径向流的压力梯度和启动压力梯度问题进行了对比,并提出了启动流量的概念。同时,对低渗透致密油藏,提出了更为实用的启动生产压差和启动井底流压的评价方法。

Bear first presented a physical concept and discriminant of the starting pressure gradient in 1972 when he studied the applied lower limit of the Darcy law,and then Professor Ge Jiali introduced the starting pressure gradient to China in 1982.The so-called starting pressure gradient refers to a pressure gradient that makes a fluid in fluid-saturated cores begin to flow.It should be pointed out that the pressure gradient of linear flow is directly proportional to the flow rate,while the starting pressure gradient is a constant.The pressure gradient of plane radial flow is directly proportional to the flow rate but inversely to the radial radius.Moreover,the starting pressure gradient at a position of different radial radius is variable.It is controversial for the correctness to have directly applied the Bear＇s starting pressure gradient and discriminant of linear flow to the plane radial flow equation by some researchers.Theoretically,the paper analyzed both the pressure gradient and starting pressure gradient of linear flow and plane radial flow and proposed the conception of starting flow rate.At the same time,a more applicable method to evaluate the starting drawdown pressure and starting bottomhole flowing pressure of low permeability tight reservoirs was proposed.