Page 127 - Open-Hole Log Analysis and Formation Evaluation
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the
are
very
rock
oil-wet,
Some
tionally,
interface
low
large
As
important
that can be
downward
water-wet,
smallest
a
of
to-the
and
systems
pore
an
the
oil
concept
progress
possible
rock/fluid
result,
rock/fluid
and
Therefore,
capillaries
systems
irreducible
by
expected to
no
capillaries.
channels
interphase
oil/water
in
or
of different
of oi!
and
fill
water,
considered water-wet,
water
offer
in
systems
will
systems
water
pore
on
There
distinguishing
single
the
density
is
are
between
a
porosity
comparing
the
meniscus
greater
trait
pore-size
At
the pores.
value
those with
are
saturation,
can
and
throats.
by
exhibiting
rock
saturation.
of
reservoir
being
distinct
and
r
the
more
is
capillary
resistance
the
the.time’
can
this
contact
surface
limit
preferentially
than
Figure
most
distribution.
oil
is
considered
to
(p, is
relative
permeability.
6.7
(see
pressure
105°
contact
the
angles
high
oil-wet
fig.
are
strongly
of pore
neutral.
referred
migrates
less
number
angle
curves
6.8).
the
@
amount
rather
illustrates
sizes
into
for
Note
than
at
because
resisted
or lines
pore
and
in
ris
of oil
Large-diameter pores offer little
75°
of small
considered
this
the
have
that
than
Tradi-
four
_
_ Water Wet irreducible water saturation. Clean sands of high permeability ‘with their attendant small pore throats tend to have very high irreducible water saturation, S,,;. Shaly, silty, low-permeability rocks minimum to as the saturation, if looked at in terms of water saturation, translates into a and This maximum possible oil @<90° oil saturation possible is
1
6,
=
2
=
=
rat
~
>
THE
FIGURE
600
800
200
400
0
Porosity,
0
6.8
2
6.7
Neutral
.
After
|
OF
Wetting
md
Capillary
20
Rock/Fluid
NS
|
Core Labs.
T
1
Phase
\
Pressure
B%
md
1
ROCK/FLUID
a
Oil
Porosity
23 5 md 2md oD 20% T ———————_ > Increasing irreducible water saturation PHYSICS
40
3
Wettability
Wet
and
Curves
and
as
SYSTEMS
Saturation:
N\
a
60
4
\
6%
Permeability
\
Percent
|
Function
re—
80
Pore
Contact Angle: After
4%
v
re,
Water Saturation:
Space
Percent Pore Space
100
0
of Permeability
go
40
Core Labs.
200
4
120.2
Ss
160
aw
=
—
2
‘D
=
and
o
“So
