(1)	$\begin{array}{l}\displaystyle \frac{1}{R_t} = \frac{\phi_e^m \, s_w^n}{A R_w (1-V_{sh})} + \frac{V_{sh}}{R_{sh}} s_w^{n/2}\end{array}$

where

$\begin{array}{l}s_w\end{array}$	formation water saturation
$\begin{array}{l}\phi_e\end{array}$	effective porosity
$\begin{array}{l}V_{sh}\end{array}$	shaliness
$\begin{array}{l}R_t\end{array}$	specific electrical resistivity from OH logs
$\begin{array}{l}R_w\end{array}$	specific electrical resistivity of formation water
$\begin{array}{l}R_{sh}\end{array}$	specific electrical resistivity of wet shales
$\begin{array}{l}A\end{array}$	dimensionless constant, characterizing the rock matrix contribution to the total electrical resistivity	0.5 ÷ 1, default value is 1 for sandstones and 0.9 for limestones
$\begin{array}{l}m\end{array}$	formation matrix cementation exponent	1.5 ÷ 2.5, default value is 2
$\begin{array}{l}n\end{array}$	formation matrix water-saturation exponent	1.5 ÷ 2.5, default value is 2

Page tree

See Also