以碳酸盐岩为主体的复杂储层,其多元的孔隙结构和强烈的非均质性导致经典的阿尔奇方程产生非阿尔奇特性。基于2028块岩心岩电实测数据,结合三维数字岩心微观数值模拟,深入分析组成碳酸盐岩多元复杂孔隙空间的不同“元素”(基质孔隙、裂缝与溶孔、洞)各自的导电特性及其对m、n值的影响,阐述了它们的分布特点和变化规律。认为碳酸盐岩优值的分布与变化虽然是多种影响因素的交织,但主要受岩石孔隙结构控制,其物理意义在于表征孔隙结构对岩石导电性的影响,可定义为孔隙结构指数。在影响碳酸盐岩n值变化的诸多因素中,主导因素是岩石的润湿性,导致岩石储集空间油气微观分布状态的差异性。n值的物理意义在于表征与描述微观孔隙中油气分布状态的差异性对岩石导电性的影响,应定义为油气饱和度微观分布状态指数(饱和度指数)。在此基础上,为拓展阿尔奇方程在碳酸盐岩等复杂储层的应用提出可行的思路与方法。
A non-Archie phenomenon, where the saturation exponent varies with the water saturation, has been observed for carbonate rocks. It is caused by complicated pore structure and heterogeneity in texture. It is critical to explain the non-Archie phenomenon exactly and find out how to modify it. We assume the pore space of carbonate is composed of different kind of elements, such as matrix pore, fraetures, vugs. The effect of pore space elements on the value of m and n were studied by numerical simulation of electrical conductivity of carbonate based on 3-D digital cores and experimental electrical measurements of 2 028 carbonate samples. The results indicate that the value of rn for carbonate reservoir is dominated by the structure of pore space. The parameter of m describes the effect of pore space on electrical conductivity of carbonate. So it can be defined as exponent of pore structure. Many factors have effect on the value of n. The wettability of rock has the greatest impact on the value of n because the wettability determines the micro distribution of oil (or gas) in pore space. The value of n is to describe the effect of pore fluid distribution on electrical conductivity and can be defined as exponent of saturation. A new method is proposed to modify the Archie ' s equation in order to apply it directly to complex carbonate reservoir.