Page 82 - Open-Hole Log Analysis and Formation Evaluation

. Inverted oil Oil based Water based Coring Fluid TABLE 4.2 Air Gas Oil emulsion oil Inverted ‘Oil based. based Water Yr ” Goring Fluid 4.1 TABLE
:
at
for
Gas
the
cut
The
fluid
fluid
Water
cases
"tudes
taken
the
is

storage.
to
only
for
CORING
reservoir
a
saturation
ooo
not
saturations
Nonoxidized
original
saturations.
coring
time
to
for
is
Saturation
example,
of these
hydrocarbons.
the
ensure
the
covering
given
crude
not
fluid
FLUIDS
coring fluids. The
of gas,
always
a
reservoir oil by the
that
porosity
core
Once the
changes
produce
oil,
’ cap pressure ' @, & lithology, emulsion __ S,, Sw telative ¢, & lithology, Measurements Coring Fluids Required Uncertain Gas Water emulsion Oil Oil — Water Filtrate Effects of Coring Fluids Toco coma
is
used
no
in
surface,
5S,
saturation
and
Oil-based
oil saturation.
core
range
fact that
objective.
cut,
important.
will
is
and
of
cores
at
as
further
Wettability,
muds
it
can
changes.
the
wettability,
and water in
Table
either
Table 4.1
coring
4.2
permeability
&,,./ Ro
take
of consequence—for
travels
having
Fable
a water filtrate that
relative
saturation
surface
in
lists
an
4.3
increase
; S,,, wettability, relative : water/oil cap permeability, 2y/kyo, cap pressure Suited to Meet the Core Objectives Uncertain No change Increased No change No’ change _ .- Increased Water Saturations Effect on Core on Reservoir Fluid Saturation UO LULU te
place
fluids
oil
at
the
the
or
estimates
during
example,
changes
and
.
summarizes the
the
core
three
most
~
filtrate
if the
documents
permeability cap
decrease
occur.
invades the core,
initial
effects
barrel
change
retrieved at surface, precautions
the
the formation. Water-based muds,
It is worthwhile to review the causes and approximate magni-
initial
must be
fluid saturations are changed by the coring
reservoir
being
flushing mechanism but do not substantially alter
- different ten and transportation from the times: different coring suitable of water is core of various may ‘replace displacing pressure permeability, . pressure of Analysis. Decreased Replaced Decreased Replaced Replaced Decreased Hydrocarbon
TABLE 4.3. Changes in Saturation as a Function of Reservoir Content and Coring Fluid
69

Formation Coring Initial Change Saturations Change Saturation
Content Fluid Saturations Due to in Core Barrel Due to at Surface
Case
1 Oil/water, Water based, O 70 Flushing 30 Shrinkage 12
oil badly G Expansion Expansion 40 ous
productive 6 3 flushed vo ~ cov Ww 30 Expulsion 70 Expulsion — 48 OUR OUB
a
a
°
N
g
we
Ss
32,
506
SS
53
25
25
a
2
Bo
8
=
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se
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68
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282
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8
5 “wr QO oO gna SHA E28 Bus 2 oO 8 o wT &. oO vo eB 3B 2864 25 3 UST Sd Bu ORs 5 oO 8.32.9 Vu ZEBo5 ts OUB OUB oo t | mw am A 184 || oo i 8 Oo oo O88 So 5 om 5 Gee G BSS s aad o & Re} a c oO aA oO OUBsB OUF
a0
a
6 Oo THA end s8 pow ¥ 6 28é SRS Heo %Z OUB SCRASCRAR Se Qa .$2, on - SCRARSA A aa gi|fil/s3Egtl4téss3 BB 6 a S“SSZQBRBACLR OUR
8
7 eS EBS SzOS yi 8 o g B 4 B a oS 4? OO8B ooocne 418 ooo BE 2B S§ a ooo OUB
38
a
8 Water, B g Vv Oil based, oO s i Invasion OD 8 40 if Shrinkage 35
water badly G Expansion 10 Ou
productive flushed a = W 100 ooo Flushing 60 ooo Explusion 55 NO Nt OusB
oO
Oo
ww
o
an
mt oN
aaa
<&3
Ou8
wn
. |)
&
cS
gos
B25
Sse
S63
AseZ
UC
bes
wy
oe
10 Oil/water, 7B Water based, 2 oO BS 5 eq 2 t F rus. Wn hing on ~ 25 Shrinka ge Qe 22 ® °
depleted badly 15 Flushing 5 Expansion 10 OB
reservoir flushed 30 Invasion 70 Expulsion 68