"""Functions for computing resistivity from saturation
"""
[docs]def archie(sw, poro, m, n, a=1):
"""Compute the formation resistivity.
This function calculate formation resistivity from water saturation, porosity,
and Archie's parameters a, m, and n.
The formula for the Archie's Law is::
Rt = a * poro**m * sw**n
Args:
sw : 1d array. Water saturations.
poro : 1d array. Formation porosity.
a : Archie's parameter, constant.
m : Archie's parameter, cementation exponent.
n : Archie's parameter, saturation exponent.
Returns:
resistivity : 1d array.
Example:
>>> from petrophysics.resistivity import archie
>>> rt = archie(1.0, 0.2, 2, 2, 1)
0.04
"""
rt = a * poro**m * sw**n
return rt