Page 329 - Petrophysics 2E
P. 329
298 PETROPHYSICS: RESERVOIR ROCK PROPERTIES
The determination of the irreducible water saturation, Swi, constitutes
the fourth phase. Capillary pressure data published by Osborne and
Hoga, and the correlative porosity data from 276 core samples in San
Andres reservoir were used with the following empirical equations
for determining relative-permeability values and, subsequently, hi
values [51]:
(4.162)
kro = ( ) (4.163)
3
0.9 - Sw
0.9 - Swi
Figure 4.54 shows the relationship between the porosity and the
irreducible water saturation, described by the following equation
obtained by the least-squares method:
log hi = - 1.4706 log $ + 2.729 (4.164)
where both Swi and $ are expressed in percentages.
The fifth phase of the core analysis involved measurements of grain
density for log analysis purposes. Rock fragments representative of the
32 samples, used for plug-core analysis, were crushed to grain-size. Grain
volume was determined on a helium porosimeter giving an average grain
density of 2.85 g/cc.
100
1
1 10 100
Irreducible Water Saturation, %
Figure 4.54. Relationship of porosity to irreducible water, West Howard-Glasscock
Unit [50].
