水驱油藏相对渗透率曲线经验公式研究

摘要

In the process of oilfield development,the curve fitting method and empirical formula are usually used to determine the variation of relative permeability curve of water drive reservoirs,so as to accurately simulate the oil production and water cut.When using Willhite empirical formula to fit the relationship between relative permeability and water saturation of the outlet,the fitting error is large.Especially for the relative permeability curves with small interval and sharp change,the fitting error is larger.In order to accurately characterize the changing regularity of the oil-water relative permeability curves,on the basis of the analyses of the existing formulas,Willhite empirical formula was chosen as the basic fitting formula to study the relationship between phase index and water saturation,and the oil phase and water phase index were modified.The results show that the fitting accuracy of Willhite empirical formula can be improved obviously by using binomial relation to characterize the relationship between oil-water phase index and water saturation,and the average fitting error is controlled within 8％.The improved Willhite empirical formula can characterize the changing regularity of oil and water more accurately,and has certain practicability and popularization value.%油田开发过程中,通常采用曲线拟合和经验公式相结合的方法来确定水驱油藏相对渗透率曲线的变化形态,以便准确模拟油田的产油量和含水率.利用Willhite经验公式对相对渗透率与出口端含水饱和度之间的关系曲线进行拟合时,拟合出的曲线与原始曲线的误差较大;尤其是用Willhite经验公式拟合共渗区间小、形态变化剧烈的相渗曲线时,拟合误差更大.为了准确表征油水相对渗透率的变化规律,在深入分析国内外已有经验公式优缺点的基础上,选用Willhite经验公式作为基础拟合公式,研究油、水相指数与出口端含水饱和度的关系,并逐步修正油、水相指数.结果表明:采用二项式表征油、水相指数与含水饱和度之间关系时,可以明显提高Willhite经验公式的拟合精度,平均拟合误差小于8％.整体而言,改进的Willhite经验公式能够更准确的描述油水变化规律,具有一定的实用性和推广价值.