矿化度及水型变化对饱和度评价模型中m、n、B值的影响机理研究

Analysis of saline type and salinity effect on parameters m, n and B of saturation evaluation models

在岩石物理实验的基础上,综合运用水岩相互作用、表面物理、电化学等方面的理论,研究水型及矿化度变化对阿尔奇模型中的m、n值以及Waxman-Smits模型中B参数的影响及作用机理.结果表明,水型及矿化度的变化不仅对m、n、B值产生影响,由于在不同的浓度范围内,地层水矿化度对岩石颗粒表面偶电层厚度及平衡离子活动性的影响不同,还导致Archie公式中的m、n值以及Waxman-Smits模型中的B参数在不同矿化度范围内表现出不同的特征:低矿化度情况下,m、n、B值随着矿化度的降低而迅速减小;而当矿化度升高到一定程度以后,m、n、B值趋于稳定,此时的岩电参数是偶电层中扩散层消失后岩石电学特征的反映.

Based on petrophysical experiments and water-rock reaction, surface physics and electrochemistry theories, mechanism of water saline type and salinity effect on parameters m and n of Archie equation and parameter B of Waxman-Smits model are studied. Parameters m, n and B are not only related with salinity, but also show different characteristics in different range of salinity. The length of electrical double layer （EDL） λD and activity of counter ion are controlled by electrolyte solution concentration and valence of counter ion. Under lower salinity condition, parameters m, n and B increase with solution concentration. But when the concentration is high enough, parameters m, n and B maintain steady, do not change obviously with salinity. The state of parameters m, n and B keeping steady in the case of high salinity reflects the electricity characteristics of the rock when diffuse layer of EDL disappears in high concentrated salt solution.