Page 150 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

Formation Evaluation 119

I I I I I I I
90

80
8
.-
3
* 70

z
0
F 60
U
a
3
I-
2 50
a
W
% 40
3
w
-
d 30
0
2
8 20
a
-
E
IO

0
5 IO I5 20 25 30 35 40

POROSITY, O/'o
Figure 5-64. Timur chart for estimating permeability 11981.

This is because the mudcake is mostly clay particles and has very little water
associated with it. The clay particles in the mudcake tend to align themselves
parallel to the borehole wall, developing a high horizontal resistivity, R,, (Figure
5-67). Since the mud filtrate is composed only of fluid and has no solids, it
will have a lower resistivity. If the resistivity of the mud (R,) is known, Rmc and
Rd can be estimated with the following equations:
Rmf = Km(Rm)'." (5-88)