Tech Reservoir Tamu FluidSat
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Transcript of Tech Reservoir Tamu FluidSat
8/16/2019 Tech Reservoir Tamu FluidSat
http://slidepdf.com/reader/full/tech-reservoir-tamu-fluidsat 1/13
Fluid Saturations
Introduction
8/16/2019 Tech Reservoir Tamu FluidSat
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Fluid Saturations
• Definition - The fluid saturation for a particular fluid is the
fraction of pore volume occupied by that fluid
– Saturation is an intensive property
– Equation Form: So!o"! p# S$!$"! p# S%!%"! p
• These fluid volumes are measured under specific conditions of pressure and
temperature &e'%' reservoir# or laboratory(
– reservoir conditions are often noted as )in situ*
8/16/2019 Tech Reservoir Tamu FluidSat
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Fluid Saturations
• Fundamental +elationships
– ,ore volume is occupied by fluids &$ater# oil# and"or %as(
• for the t$o phase case# only one of the t$o saturations is independent# the other
must mae the sum of the saturations equal to unity &.(
• similarly# for the three phase case# only t$o saturations are independent
%o$
p
%o$
%o$ p
SSS!
!!!
.
!!!!
++=
++
=
++=
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Fluid Saturations
• Fundamental +elationships &continued(
– /ass of fluids in the pore volume is comprised of: $ater# oil#
and"or %as
• at laboratory conditions it is often assumed that %as density is ne%li%ible
[ ]%%oo$$ p
%%oo$$
%o$
S0S0S0!!0!0!0
mmmmassfluid
++=
++=
++=
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Initial Fluid Saturations in +eservoir
• 1oncepts: typical petroleum accumulation scenario
– pores are initially saturated $ith $ater &S$.(
– hydrocarbons mi%rate up dip into traps due to havin% density less than $ater density
&%ravity force(
– hydrocarbons &oil and"or %as( is distributed such that %ravity and capillary forces are
in equilibrium
• minimum interstitial $ater saturation remains in hydrocarbon 2one# even after accumulation occurs
– $ater $et# draina%e accumulation process
3 irreducible $ettin% phase saturation
– oil $et# imbibition accumulation process
3 residual non-$ettin% phase saturation
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Initial Fluid Saturations in +eservoir
• /ethods for determination of reservoir fluid saturations
– Direct /easurement
• 1ore 4nalysis ¤t topic(
– Indirect /easurement
• 1apillary ,ressure /easurement &previous topic(
• 5ell 6o% 4nalysis &future topic(
– electrical conductivity depends primarily on $ater saturation
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Fluid Saturations - 1ore 4nalysis
• Factors affectin% fluid saturations in cores
– flushin% of core by filtrate from drillin% fluids &especially for overbalanced drillin%(
• $ater filtrate
– $ater based mud
– oil emulsion mud
• oil filtrate – oil based mud
– inverted oil emulsion mud
• %as filtrate
– air drillin%
– foam drillin%
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Fluid Saturations - 1ore 4nalysis
• Factors affectin% fluid saturations in cores &continued(
– 1han%es in pressure and temperature as core sample is
brou%ht from bottomhole conditions to surface conditions
– E7ample: 8il 2one at minimum interstitial $ater saturation#
$ater based drillin% mud
FlushingDuringDrilling
Trip toSurface
Saturation at SurfaceCompared to Reservoir
Sw
? probably
So
Sg -
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Fluid Saturations - 1ore 4nalysis
• Factors affectin% fluid saturations in cores &continued(
– E7ample: 8il 2one at minimum interstitial $ater saturation# oil based drillin% mud
– Self Study: other e7amples in 6ecture9.'pdf
FlushingDuring
Drilling
Trip to
Surface
Saturation at SurfaceCompared to
Reservoir
Sw - - -
So -
Sg -
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4pplication of 1ore Saturations
• 4pplication of 1ore Saturations: 5ater ;ased /ud
– presence of oil 2one – ori%inal oil"%as contact
– ori%inal oil"$ater contact
• 4pplication of 1ore Saturations: 8il ;ased /ud
– fairly accurate minimum interstitial $ater saturation – ori%inal oil"$ater contact
• 8ther 4pplications of 1ore Saturations
– correlation of indirect methods
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Estimatin% Fluid 1ontact Depths
from 1ore SaturationsSo
Gas
ater
!il
"##
Depth
So ≈ 0 in gas zone
So > ≈0.15 in oil production
zone
0 < So < ≈0.15 in water
production zone
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/a7imum 5ater Saturation
for 8il and <as ,roduction
The trend shown here
continues for even lower
permeability with productive
reservoirs e!isting with
Sw>0."0 for #<0.01 md
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1ommentary on 1ore Saturations
• =ualitative !alue# 4;5 &pa%e .>?# bracets added(: )The
saturation values obtained directly from roc samples @coresA are usually notreliable for determinin% the quantity of each fluid in the roc @reservoirsA'
8ther uses e7ist for fluid-saturation determinations from core samples'*
•8verall !alue# 4;5 &pa%e ..>(:
)Thus# in summary# it is seen that
althou%h fluid-saturation determinations made on core samples at the surface
may not %ive a direct indication of the saturations $ithin the reservoir# they
are of value and do yield very useful and necessary information*