Page 302 - Petrophysics 2E

LAB-DERIVED EVALUATION OF SHALY 273

TABLE 4.1 1
f.AB0RATORY VALUES OF s, AND IRL

0.2 46.1
0.3 17.6
0.4 8.9
0.5 5.2
0.6 3.4
0.7 2.3
0.8 1.7
1 .o 1 .0

the Shannon sandstone [32]. The following approach is based on this
procedure.

(1) The effective volume concentration of clay-exchange cations, Qv ,
can be calculated from:

and the formation resistivity factor for the shaly sands is obtained
from the Waxman and Smits Equation 4.130, or:

where the formation water resistivity is equal to 0.386 ohm-m,
and the specific counterion activity or equivalent conductance of
clay-exchange cations is 2.9 liter/eq.ohm-m from Figure 4.40. Using
Equation 4.139 one obtains:

C,, = (1 - 0.83e-0.5/0.386) 3.83 = 2.96

Inasmuch as RwCeq = 0.386 x 296 = 1.14, the equation describing
F* for the Shannon sandstone field is:

F* = FR(~ + 1.144,)

The values of Qv and F * for the first core sample in Table 4.12 are:

)
1 (2.65) (0.042) = 0.30liter/eq.ohm-m
Qv=(&-