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ABSTRACT Much work has been done to develop empirical relationships between water resistivity, porosity, and water saturation. A modified theory on the relationship between formation resistivity factor and porosity is presented. This theory considers that, from the standpoint of the flow of electric current within a porous medium saturated with a conducting fluid or electrolyte, the pore space can be divided into flowing and stagnant regions. This assumption leads to a general expression, and formulas currently used in practice are special cases of this expression. The validity of this modified expression is established by the use of various data corresponding to sandstones, packings and suspensions of particles. For the case of natural rocks, the theory confirms Archie's equation using Frickle’s model and gives an interpretation of the physical significance of the so-called cementation exponent, n. A formula relating porosity and formation resistivity factor is presented. This equation is applicable not only to consolidated and unconsolidated materials, but also to dispersive systems. A comparison of calculated values (porosity) with experimental data shows the equation yields much more satisfactory results.
