# Formation factor - Archie's equation

## Input(s)

a: Tortuosity Factor (dimensionless)

\(\Phi\): Porosity (fraction)

m: Cementation Factor (dimensionless)

## Output(s)

\(F\): Formation Factor (dimensionless)

## Formula(s)

\[
F=\frac{a}{\Phi^{m}}
\]

Notes: \(a\) and \(m\) are measured from log-log plot of \(F\) vs Porosity.

## Reference(s)

Core Laboratories. 2005. Formation Evaluation and Petrophysics, Page: 38.