Page 295 - Petrophysics 2E

266 PmoPHysrcs: RESERVOIR ROCK PROPERTIES

I I I I I1111 I I I I Illll I I I Illl
0,Ol I
IO too I
RESISTIVITY RATIO, I
Figure 4.37. Water saturation as a function of resistivity index, witb variable water
resistivity [28J

nu 2.0
R,=O.S ohmr

$2
-
a
y.

100
RATIO,
1
10
RESISTIVITY
O.Ol1
II
K)
Figure 4.38. Water saturation as a function of res#stiv#@ index with variable Qu [28].
from the Waxman and Smits model [31]. In the same study, Waxman
and Thomas investigated the effect of temperature on the electrical
conductivity of shaly cores, and showed that:

(a) the shaly sand formation resistivity factor, as defined by Waxman and
Smits, is independent of temperature, and
(b) the observed increase in conductivity of shaly cores with
increasing temperature, as illustrated by Figure 4.39, is due to
two temperaturedependent parameters: the equivalent counterion
conductance, C,,, and the resistivity of the equilibrating brine, Rw
as shown in Figure 4.40.