Page 89 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

Basic Principles, Definitions, and Data 77

[154] showed that each of the relative permeabilities could be calculated even
when gravity is not neglected. Other calculations of relative permeabilities have
been proposed by Higgins [155], Guerrero and Stewart [156,157], and a graphical
technique has been presented by Jones and Rozelle [158].
An example water-oil relative permeability plot vs. water saturation is given
in Figure 5-54. Several features will be described that pertain to generating
relative permeability curves from cores in the laboratory. If a clean, dry core is
completely saturated with water, the permeability at 100% Sw should be similar
to the equivalent liquid permeability obtained from gas flow measurements at
100% Sg. Exceptions to this generality include some low-permeability systems
and other cores that contain clays or minerals that interact with the water used.
If a clean core is used, it will probably be strongly water-wet when saturated
with brine. As crude oil is injected into the core, the relative permeability to
water decreases during the drainage cycle (decreases in wetting phase) while
the relative permeability to oil increases. Some water that resides in the nooks
and crannies of the pore space cannot be displaced by the oil, regardless of
the throughput volume. This water saturation, which does not contribute
significantly to occupying the flow paths, is called the irreducible water satura-
tion, Siw. With the core at Siw, there is 100% relative permeability to oil (only

I .o f 1.0
\ I I I I
c
.- I
0
c
0 I
2
rc I- 0.8
. 0.8
-
-I
0 I
e I
> 0.6 4
k
-
-1
m /
a -
0.4 L 0.4
a 1
k! I
w
- -Sor -
>
0.2
c 0.2
a
J
W \
a \
0 I ‘lo
0 20 40 60 80 loo
WATER SATURATION. % pore volume

Figure 5-54. Example of water-oil relative permeability data.