Dictionary:Dar Zarrouk

(dar zar ruk') The name given by Maillet to resistivity parameters or curves that deal with layered anisotropic materials. The dar Zarrouk variable is the transversal unit resistance ($\rho _{T}$), the depth integral of the transverse resistivity perpendicular to the strata; the dar Zarrouk function is the longitudinal unit conductance (${\frac {1}{\rho _{L}}}$), the depth integral of the conductivity parallel to the strata; and the dar Zarrouk curve is a plot of the mean resistivity ($\rho _{T}$) of the formation down to the depth z, plotted versus the anisotropy coefficient times $z(\rho _{T}\rho _{L})^{1/2}$:

$\rho _{T}=\sum \rho _{i}z_{i}\ {\text{and}}\ {\frac {1}{\rho _{L}}}=\sum {\frac {z_{i}}{\rho _{i}}}$

where $z_{i}$ are layer thicknesses.