1. Lecture15 RESISTIVITY
Introduction
Resistivity Is the rock property on which the entire
science of logging first developed.
Different materials have different abilities to resist the
flow of electricity.
Resistivity is measured by electric logs.
The reciprocal of resistivity is conductivity.
Resistivity is a basic measurement of a reservoirs fluid
saturation.
the ability of the rock to transmit a current is almost
entirely a function of water in the pores. Hydrocarbons,
like the rock's matrix, are non-conductive; therefore, as
the hydrocarbon saturation of the pores increases, the
rock's resistivity also increases
As for the saltwater, is a conductor and has a low
resistivity.
The measured units are called ohm-meters.
Resistivity logs are plotted on a logarithmic scale.
2. Corrections For Induction Log readings
Hole size and mud resistivity corrections
Example 15.1: - Using 6FF40
tool, Ra= 20 ohm-m, dh=14.6”,
Rm=0.35 ohm-m, stand-off
=1.5 in, find Rt.
Sol.: -
By using Chart 15.1, Hole signal = 5.5
mmhos/m
C =
1000
R
=
1000
20
= 50 m − mho/m
Ct corr. = Ct- hole signal
Ct corr.= 50-5.5=44.5 m − mho/m
RILcorr.=Rt =
1000
44.5
= 22.4 ohm − m
