新型水驱前缘解析法研究及应用

Research and application of new analytical method for frontal water-flooding

莱文莱特函数式中的含水率为含水饱和度的隐函数,在确定水驱前缘含水饱和度时常采用图解法,其精度受人为因素影响较大。为此,在新的油、水相渗规律研究基础上,提出了新型油水相渗比与含水饱和度关系式——Gao简化式。该式不仅可以转化为方次式和Willhite式,而且也将莱文莱特函数式中的含水率转化为含水饱和度的显函数,可直接导出水驱前缘含水饱和度、前缘后平均含水饱和度、见水后平均含水饱和度以及驱油效率等方程的解析式。这些解析方程式便于注水开发指标的计算和经典图形的自动绘制。经丘陵油田实际应用,运用解析法不仅可得到水驱前缘含水饱和度和其他注水开发指标,而且也能绘制出驱油效率与注水孔隙体积倍数、含水率与注水孔隙体积倍数等经典曲线,值得其他油田借鉴。

In view of the fact that the Leverett function is the implicit function of water saturation, the accuracy of water-flood front saturation which is often determined through graphical method is greatly affected by factitious factors, a new equation of oil-water relative permeability ratio and water saturation--Gao＇s simplified formula--is put forward based on the new rules of oil and water seepage. It can be further transformed into Willhite equation as well as multiple equations. In addition, it is able to transform Leverett function into the explicit function of water saturation from which the analytical equations of the water-flood front saturation, average water saturation after front, two-phase average water saturation after water breakthrough, and the oil displacement efficiency, etc. can be directly derived. These analytical equations facilitate the calculation of water-flood development indexes and the automatic drawing of classic graphics. After application in Qiuling Oilfield, water-flood front saturation and other water-flood development indexes, classic curves of oil displacement efficiency and injection pore volume multiple and of water ratio and injection pore volume multiple can be obtained through analytical method, the achievements of which can be adopted as a reference for other oilfields.