基于Weibull模型的相渗关系表征研究

摘要

This study aims to solve the large inaccuracy in characterizing the relative permeability relationship at ultra low and ultra high water saturations in gas reservoirs.We conducted a thorough analysis of measured experimental data for relative permeabilities of rock core samples.We found a good linear relationship between the natural log of water and oil relative permeability ratio,ln (Krw/Kro),and double natural log of normalized water saturation,ln(ln1/1-Swn).These two parameters fit a Weibull function.On this basis,a new equation for the relationship between relative permeability is proposed based on a Weibull model;this improves the fitting calculation for the relative permeability fractional flow equation.Compared to traditional methods used in reservoir physics,this method and the relative permeability fractional flow equation derived from it,can significantly improve the fitting accuracy for water production rate in the ultra low to medium water cutting period.%针对特低含水饱和度和特高含水饱和度时相渗关系表征误差较大的问题,通过对大量岩芯样品的相对渗透率测定实验数据进行详尽分析,发现水、油相对渗透率比值的自然对数ln(Krw/Kro)与标准化后的含水饱和度Swn的双重自然对数ln (ln1/1-Swn)之间具有良好的线性关系,两者符合Weibull函数关系.在此基础上,基于Weibull模型提出了一种新的相渗关系表征关系式,并以此为基础改进了相渗分流量方程的拟合计算方法.该方法及由其推导的相渗分流量方程较传统油层物理学方法计算的分流量方程在特低-中含水期内能大幅度提高产水率的拟合精度.