Archie's laboratory experiments established a relationship between the formation resistivity factor and porosity, which set forth the use of two constants: m and a. From Archie's work these constants were regression constants representing the slope and intercept, respectively. Subsequent researchers used the general form of Archie's relation, but they found differing values for m and a. The terms cementation factor and tortuosity factor have been used to describe each of these terms. Conventional wisdom believes that a higher m relates to vuggy porosity and a lower m suggests fracture porosity. This is generally true if the tortuosity factor is assumed (typically 0.81 or 1.0) and the cementation factor is calculated.

However, if m and a are found simultaneously, theory and many laboratory observations suggest the opposite may be more likely. This study shows that the tortuosity factor, a, is a function of the average angle of electrical movement with respect to the bulk fluid flow, and cementation factor m is related to the flow area contrast between pore throat and pore body.

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