Formation Evaluation Through Casing - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 146

Gamma Ray Index is defined as a linear rescaling of the GR log between GR min and
GR max such that:

GR GR
GR

-

Gamma RayIndex =

min

-
If this index is called X , then the alternative relationships can be stated in terms of
X as follows:

GR

max min

Relationship Equation

Linear V sh = X

Clavier

ë

(

0 7 2

)

û

V

sh =- -+

17 . 338 . X .

Steiber

05
15

. X

X

V

sh =

( )

. -

Bateman V sh = X ( X + GR Factor)

where the GR Factor is a number chosen to force the result to imitate the behavior
of either the Clavier or the Steiber relationship. Figure 11.8 illustrates compara-
tively the difference between these alternative relationships.

1

Linear
Clavier
Steiber
Bateman (Factor 1.25)
Bateman (Factor 1.5)

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

GR Index (X)

Fig. 11.8 V clay as a function of Gamma Ray Index