Page 157 - Petrophysics

130 PETROPHYSICS: RESERVOIR ROCK PROPERTIES

Calculate the formation resistivity factor using the Humble equation:

0.81 0.81
F=-=-- - 126.56
$2 0.082
The plot of RQI versus @/( 1 - 0) shows two straight lines of slope
unity, indicating two hydraulic units. The corresponding FZI values
are 15 and 9 respectively. The corresponding values of HT are
obtained fiom Equation 3.52:
Hydraulic unit #1, FZI = 15:

1
1
&=-- - - 4.44 x 10-3 ym-2
=
FZ12 1!j2
Hydraulic unit #2, FZI = 9:

(b) Calculate tortuosity using Equation 3.50, and assuming m = 2:

This plot verifies that there are two hydraulic flow units in the
reservoir.
(c) Calculate free fluid index (FFI) using Equation 3.57:

FFI = $(l - &,,) = 0.08(1 - 0.15) = 0.068

Note that extrapolating the two straight lines to FFI = 100% yields
the same FZI values as are obtained from the plot of RQI versus &.
See also Figures 3.22-3.24.

EFFECT OF PACKING ON PERMEABILITY

The lack of global applicability of the Kozeny model has led researchers
to generate empirical correlations on a formation-by-formation level.
Since no plausible physical models exist, these correlations have not
been accurate enough to gain wide acceptance. This lack of accuracy
may however be acceptable when gauging the relative difference of
permeability of different zones, but not for obtaining an accurate
permeability.