基于等效岩石组分理论的饱和度指数影响因素

岩石的非阿尔奇特性主要受到孔隙结构、流体分布状态、岩石骨架附加导电、润湿性、临界饱和度等的综合影响。本文应用等效岩石组分模型进行了导电模拟,引入了孔隙结构效率、饱和度因子、饱和度指数、临界饱和度等参数,综合分析了各参数对饱和度指数的影响。研究表明:临界饱和度和第一饱和度因子对饱和度指数的影响最大,第二饱和度因子的影响次之,孔隙结构效率的影响最小,表现为:饱和度指数随着临界饱和度和第一饱和度因子的增大而增大,随着孔隙结构效率和第二饱和度因子的增大而减小。文中对中国东部G油田的岩心进行了实验分析,低孔低渗、中孔低渗、高孔低渗岩心的实验测量结果表明,在岩心孔隙度范围为15.2%～20.8%时,利用等效岩石组分模型拟合的含水饱和度—电阻率指数曲线的相关系数(0.93～0.97)较传统的阿尔奇模型拟合的相关系数(0.76～0.84)大。因此应用等效岩石组分理论能更加精确地描述岩石的非阿尔奇特性,从而明显提高饱和度计算的精度。

Study on the influential factors of saturation exponent based on the equivalent rock element theory

Rock non-Archie property is affected by pore structure,fluid distribution,rock matrix’s additional conductance,wettability,critical saturation,etc.This work simulates the conductivity of porous rock using the equivalent rock element theory.We introduce a few parameters,such as pore structure efficiency,saturation factors,critical saturation and their influences on saturation exponent.The result shows that critical saturation and the first saturation factor have the largest effects on saturation exponent,secondly the second saturation factor.Pore structure efficiency has little effect on saturation exponent.Saturation exponent increases with the increase of critical saturation and the first saturation factor.But it decreases with the increase of the pore structure efficiency and the second saturation.We select core samples from G oilfield(East China) for petrophysical experiments and verification of our theory.The experiments of different permeability cores demonstrate the coefficient of saturation-resistivity index fitted by the equivalent rock element theory is between 0.93 to 0.97,higher than that by conventional Archie equations(0.76～0.84) when porosity ranges from 15.2% to 20.8%.The equivalent rock element theory depict rock non-Archie property more exactly,thus will enhance the saturation calculation precision.