# Fraction of total porosity occupied by clays

## Input(s)

\(\Phi_{S}\): Sonic Log Porosity (fraction)

\(\Phi_{D}\): Density Log Porosity (fraction)

## Output(s)

q: Fraction of the Total Porosity Occupied by Clays (fraction)

## Formula(s)

\[
q=\frac{\left(\Phi_{S}\right)-\left(\Phi_{D}\right)}{\Phi_{S}}
\]

## Reference(s)

Core Laboratories. 2005: Formation Evaluation and Petrophysics, Page: 98.