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SPE 20037
Phase Behavior Properties of COz/Heavy Oil Mixtures for
EOR Applications
S, 3, Sayegh, Petroleum Recovery Inst., and M, Sarbar, Esso Resources Canada
SPEMembers
SPE
Copyright 1990, ScUWNyof Petroleum Er@neer8 Inc,
Thi s p ap ar W8Sp rep ared for p re ean ln tl on et Ih e Wth Cal if orni a Reg io nal Mwt ln g h el d In Ven tu ra, Cal if orni a, AN 4-6 1~.
Thin papar wae wlecmd for praaerdation by an SPE Pr~ram Commit tee fo llowing review of Informal Ion contained i r ran abstract aubmlt ted by the author e). Contents of Ihe pwar,
a 8
prwanled, have not been reviewed by the Society of Pel roleum E’g lneem and are eubjact to correct ion by the author s). Tha mater ial , ae preeented, does not naoeaaari ly rel lect
any posi t ionof the SooIe ty of Petroleum Englneera, I taof f lcerei or memti ra. Pepera prewnted at SPE meetlngareubjaa0publicationeviewyEdllorlalomml ltwa ot the Soale ty
of Petroteum Englnaera. Permiaalon to copy{erestricted toan abstract ofnot morethanZCKIwords. I l luetratbna may notbe copied.The abstract ahoutdOontalnccmpkxwa i:kmladgmmt
of where nd by whom Ihe paper 10presented, Wri te Publ lcat lona Manager, W“E, P,O. Sox 833S3S, Richardson, TX 7608S-3S38. Telex, 730S69 SPEDAL,
ABsTRAcr
The objectiveof thisstudyis to measurethe
phasebehaviorandpnysicalpropertiesfa Canadim
heavy crude oil (llOAPljsaturatedwith carbon
dioxideaa a functionof pressureand temperature.
Thesedatsare usedto evaluatethe feasibilityf
usingcarbondioxideas a pretreatmentfor steam
floodsor as a steamadditive.
Experimentalmeasurementswere carriedout at
69,@F (21°C),the reservoirtemperature,and at
284°F(14@C). Thesaturationressureserebetween
400 ,Jsi(2.8MPa)and 1,500psi (10.3MPa).At each
pressurelevelthevolubilityf CC+in theoil,the
density,and theviscosityof the saturatedmixture
weremeasured,
The resultsshowedan increasein thevolubility
of C% in the oil with increasingpressureand
decreasingtemperature,hilethe densitiesof the
ml.xturesid not change to a large extentwith
changingcompositions,
The most dramaticeffect
observedwas the decreaeein vlscoeitywith C
%
issolutionntheoil: A 53-foldreductionoccure
at 69.80F(210C)and a 2-foldredu~tionat 2840F
(14CPC)
SARA analysesof varioussampleawere carried
out
It waa found that at 69,@F (21°C)some
redistributionf asphaltenesndresinsoccurredat
pressuresibovetheiquefactionresaureofC~ (850
pqior 5.9MPa).
These results indicate that, frov a phase
behaviorpolntof view,enhanccdoil recovetybyC02
injectionin the heavyoil reservoiris fetiaible,
and thatviscosityreductionwouldplaya m~jorrole
in improvingproductivityt lowertemperatures.he
asphaltenes/resitls
alanceshould be taken into
accountwhenstilectinghe injectionpressure.
INTRODUC1’ION
Conventionaluse of C02 for improvingoil
recovery has been mostly for miscible flood
applicationswhere the displacementof crudeoil
from the pore space within the reservoirsis
achievedby thesolventactionof CC+whichprevents
formationof an interfacebetweenthe drivingand
thedrivenfluid, The diapl.acementrocessis very
effectiveand potentially00%of the oilin place
couldbe recoveredfromthe sweptzone.
However,in heavyoiiand biturnenouseservoirs
suchmiscibilityannotbe obtainedand it willnot
be a factorin increasingil recovery.Rather,the
enhancementof oil recoverywill be the resultof
the highsdubilityof C% in low API 8ravityoils
which~n turnwouldresultin:
(1)
A substantialiscosityreduction-10-fold
or morecan he easilyachieved.
(2)
Considerable
oil
swelling
(10-30%)
depending
on the saturationpressu”,
reservoirtemperature,nd the crudeoils
composition.
(3)
Improved
reservoir
energy
‘?
after C
?
treatmentsinceC
gas will come out o
solutionand provde a drivingforce to
sweeptheoiloutof thereservoir.
(4)
The loweringofInterracialensionbetween
theoiland theaqueousphases,
Also, due to the chemicalreactionsbetween
~%
arbonicacid(C +
O mixture)and thecarbonete
portions of t e reservoir rock, increased
permeabilltiesan be obtainedby C$ injection.
Thiscan be usedas a preconditioningrocessprior
to steaminjectionto improvesteaminjectivity.
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PKASEBEHAVIORPROPERTI~OF C132/W~ OIL~~~s ~R EOR @pLI~T~ONS
SPE20037
In orderto realizethesebeneficialeffects,
temperaturerecordedin one of the teats
9
gas must be injectedinto the reservoirand
was l,~F (-l~C).
This
had a negative
al owed to diffuseintothe oil it contacts.
But
effecton thedispersionndsolubilization
beforediffusioncan workas a practicalmeansof
of c~.
treatinga largevolumeof oil,it is necessarythat
theinjectedgas effectivelyenetratethereservoir
(c)
Excessivesand productioncen hinderoil
and providea largearealcontact.
The presenceof
production.hiscanoccurif theinjected
a fracturenetwork (dual porosity system) is
C% is inefficientlyispersedintotheoil
expectedto providelargearealcont~ctneededfor
phaseas a resultof, for example,high
the dispersionprocessto be effective.
injectionrates. Consequently,a large
amountof the injectedgasis producedwhen
Phasebehavlourstudiescan be usedas screening
the wells are put on production and can
tools to evaluste
the effectivenessf C(+ appli-
carry reservoirssnd into the producing
cation for improvedrecovery.
Phase behaviour well
propertiesof variousC% heavycrude-oil
~i&ures
havebeendeterminedby severalresearchers
. In Someof theseproblemscanbealeviatedby,for
general,viscosityreductionvasan importantfactor example, lowering the C02 injection rates,
for all the systems,especiallywith heavieroils
bY foaming~gent~~ilityf C?2~~thintheformation
controllinghem
and at l~wer temperatures.
On the other hand,
or polymers , or deployingan
swellingwas morepronouncedfor the lighteroils.
adequatebottomholesandcontrollingevicesuchas
Fromthesegeneralremarksit may be concludedthat
the one developedby TexacoCanadaResources20.
C% has a good potentialas an enhancingagent to
improveheavyoil production.
Based on this information,it was felt that
beneficial
results
may be obtained
by C02
The C% stimulation
process of heavy oil
pretreatmentf reservoirsriorto steaminjection.
reservoiraasalsoexaminedby numericalsimulation
Therefore,laboratoryeasurementsereconductedto
to includethe effectof parameterssuch8s gas/oil
determine
the
phase behaviour and physical
propertiesnd criticalgas saturations7-13.t may
be concludedfromthesestudiesthatthe processcan
propertiesof mixturesof a heavycrudeoil with
Cq . The experimentalprocedureand resultsare
be a successfulone providedthat certainfactors
discussedin detailin the followingsections.
are takenintoaccount.For example,n highinitial
oil saturationand adequatereservoirdepth (or
pressure)are desirablefeaturea.Aboutthreehuff-
Ex.PERm&PRmmE
n-puffcycleswere foundto be adequatein one of
thesestudiesg.
The
phase
L?havior apparatus is
shown
schematicallyn Figure1.
It consistsof twocells
The effectivenessf C% for enhancedheavyoil withfloatingpistons.
One of thesecellshas two
recoveryhas also been field tested worldwide.
windows for visual observationof the mixtures,
AshlandOil Canada Ltd. tried a single-wellC%
whiletheothercellhas no wiri>ws. The cellsare
injectionintobottomwaterin theGrandForksLower
connectedfromtheirbasesthrougha gearpumpfor
MannvilleC Pool (Alberta)during 1977. It circulatingndmixingthe fluids. The topsof the
concludedthatthe presenceof bottomwaterre uced
f
cells
are
connected
through two
capillary
the efficiencyof the C
huff-n-puffprocess. A viscometers:
The firsthas a large diameterfor
C% huff-n-puffstimulaton of North Balsa strip
high viscosityfluids,
while the second has a
leaae of HuntingtonBeach F eld (U.S.)has been
reportedby Pattonet al.a~‘, PhillipsPetroleum
smallerdiameterfor lower viscosityfluids. A
densitometeris also placed in line with the
obtainedencouragingesultsin itsc~l$est at Lick
viscometers. l’heholeapparatusis enclosedin a
CreekFieldof SouthernArkansas)U.S. 9 Improved thermostated m.
oil recoveryhas also been achievedin the two
southernItaliantieavyoil fieldsof Piropoand
The firststepwaa to calibratethe viacometer
~onte~i,rillo2,14,
Repeatedly,successfulresults
and thedensitometer,The viscometerascalibrated
have also beeu re r d in variousoil fieldsin
Hungarysince1969P~‘.
usin~ glycerolas the referencefluid,whilethe
densitometerwaa calibratedusing nitrogenand
water, The calibrationswere done at both the
The followingare someof theobservationsnd
operatingtemperatures,v,i.z,69,@F (21°C)and
recommendationsrom the limitednumberof field
284°F(14Cf’C)O
The next stepwas to carryout the
testeof the stimulationf heavyoil.productionby
measurementsn oil/gasmixtures~t eachtemperature
theC% huff-n-puffrocess:
followingthe proceduredescribedbelow,
(a) Lirritedsuccea may be obtained if the
Abouthalfthe internalvolumeof theapparatus
reservoiria too shallowand/orits pressure
was filled with stock-tankoil, and then its
Is toolowto achl.evehighsolubilityofC02
viscosityand densityweremeasured.
Methanewas
in theheavyoil. Problemssuchas extenalve
then introducedinto thewindowedcellat 400 psi
firigeringnd excessivechannelingfurther
(2.8MPa),and thecirculatingumpactivated.This
decreasedtheC% dispersionand volubility.
hadtheeffectof withdrawingil fromthebottomof
thewindowedcell,passingit throughthe blindcell
(b) A high injectionrate of C (100tons/day,
‘?
and viscometers,hensprayingit throughthe gas
for example) can aubstantally cool the
phaseat thetopof thewindowedcell. This cawed
reservoiraroundthewellbore(thebottomhole
intimatemixingof the fluidsin theI\pparatusnd
saturatedthestock-tankil withmethaueto produce
liveoil.
—
nn.
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Qnw 9nfi Q7
S.G.SAYEGHANDM. SARBAR
3
U*
-vu-c
---- -..——.
The mixinglsaturatingtepwas carriedout for
at least four hours,and sometimesup to twelve
hours, depending on
hw fast the oil became
saturatedwith methane.
Duringthis processthe
systempressurewas monitored,and the mixturewas
assumedsaturatedwhen the systempressureremained
stable.
If the initialbatchof methanewas not
sufficientto saturatethe stock-tankoil, more
methanewas added. Carewas takenin thisstepto
keep the amountof free methaneto a minimumto
minimize possiblecompositionalChanges due to
vaporizationf componentsfromtheoil phaseto the
gas,
After the batchhad been saturated,excess
methane was purgedout at constantpressureby
openin8the pur8evalveand simultaneouslyriving
the pistonupwards.
The batch
was
left standingfor at least 12
hours,
sfter which samplesof known volume (as
measuredby the mo~ementof the floatin8piston)
weretakenfromthewindowedcell.
Eachsamplewas
flashedto atmosphericpressureand the amountsof
liquid(primarilystock-tankoil) and gas (mainly
methane)therebyproducedweredetermined.
Thegas
was then analysedin a gas chromatographynd the
densityof the stock-tankoil measured.This data
waa then used to calculatethe 8asloilratio and
compositionof the sample.
The 011 in the sample
was further characterizedusing the saturstes-
aromatics-restns-asphaltenesSARA)analysis.
The dendty and viscosityof the mixturewere
measured next..This was done by driving both
floatingpistonsin oppositedirections,thereby
flowing the contc~tsof the cells through the
densitometernd viscometer.
Carbondioxidewas then added t. the windowed
cell,whilekee>i.nghepressureconstantat 400psi
(2.8 MPa), and the above saturationprocedure
repeated.
Once equilibriumhad been attained,
sampleswere takenfrom the top and bottomof the
cells for compositionalmeasurements,and the
densitiesand viscositiesof the mixtureswere
measuredas describedabove.
This processwas
repeatedat the increasingpressuresof 900~ 1,200~
and 1,500psi (6,2,8.3and 10.3MPa,respectively),
thenat the reducedpressureof 400 psi.(2,8M?a).
The formationof multiplephaseswas indicated
if thepropertiesof the mixtureat the topof the
cell
were
differentfrom those at the bottom.
Furthermore, vl.aual
indication of
the
precipitation;a solidphasewasobtainedif such
preci.pltstesere observedon the window of the
windowedcell.
RESULTS
I
Table 1 listsomeof themeasuredproperties
of the stock-tankoil:It is a heavyoil of abcut
llOAP’l,nd k.s a viscosityof 26,846cp (mPa.s)at
69.@F (21°C),and an averagemolecularweightof
628.The stock-tankil was recombinedithmethane
to a saturationpressureof 400 psi (2,8MPa).The
33
reeultantreco i d oilhsda gas/oilratioof 253
scf/bbl(4.5
/ ) and a vimosity of 21,680CP
mPa. s),
-
Therecombinedilwasusedin allthesubsequent
Oil/cO-&
measurements.The
results of
these
measurementst 69.@F (21°C)and at ?.84°F14@c)
are shown in Figures
2 to 9 and will now be
discussedin detail.
301ubilityf ~ in theOil:
Figure2 comparesthe gss/oilratios of ‘the
oil/CC+mixturesat both measurementtemperatures.
It is immediatelyvidentthatC% is moresoluble
in the oil at the lower temperaturethan at the
higher one.
For example,at the highesttest
pressureof 1,500psi (10.3MPa) the gas/oil a o
t 69.80F(21°C)was about337 scf/bbl(60 /
whileat 2840F(}4(PC)thevaluewas onlyabout19;
scf/bbl(35IT?/n+).
An importantpointto note in Figure2 is that
moregaswas leftin theoilafterthepressurehad
beendrawndown from 1,500to 400 psi(10.3to 2.8
MPa)thantheamountdissolvedwhenthe liveoilwas
firstsaturatedwithC@ at400 psi (2t8MPa). This
is probablya consequencef thefactthat,whenthe
oilwas takenthroughthepressurization-liberation
cycle, C
%
dissolvedin the oil and displaced
methane.
his is shownin Figure3 wherethemole
fractionof C
%
in the oillgasmixtureat 400 psi
(2,8MPa) at t e end of the cycle is hi8herthan
thatat the beginin8,
Figure 4 also reflects the
above observations but vis-a-visthe oil mole
fraction:themolefractionof theoilin thecycleo
mixtureis lessthanthatin theoriginalone.
Samplestaken fromthe top and bottomof the
cellsshowedsomewhatdifferentcompositions.
This
couldindicatethat therewere two phasesformed,
thetopone bein8richerin diesolvedgas thanthe
bottomone, Thesephasesappearto be veryclosein
properties,speciallytheirdensities(cf. Figure
5), and
were
difficultto separate. Complete
separationwtisnot achievedin any of the tests,
eventhoughsomeof themwereleftstandingfortwo
to three days.
Another possibilityis that a
residualamountof gaswas trappedneartheoillgas
interfaceat the lower temperaturedue to the
relativelyhigherviscosityof the mixture.
Dsnsitlesof the OiUGaa Mixtures:
The densitieeof the oil gas mixturesare
plottedin Figure5. It is to be notedthat the
densit;valuesdid not changeto large extent
duringthe courseof the measurements:he maximum
thanewas onlyl%at 69.8% (21°C)and 1,7%at 284°F
(14Cf9c)*
At 69.80F(21°C)the densityroseslightlywith
increasingpressure,while at 284°F (14@C) the
densitydecreasedslightlywithincreasingressure.
Thereare two counterbalancingffectstakingplace
in thisprocess:The firstis the increseingmount
of C% in theoil as the pressure increases(cf.
Figure3) whichwill decreasethe densityof the
mixturesinceC02hae a lowerdensitythantheoil.
The secondfactoris the increaseddensityof the
liquidswith increasingpressuredue to their
1
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1%
PHASEBEHAVIORPROPERTIESOF Mh/~EAW OILMI.mfJRBSR EORAPPLICATIONS
SPE20037
6
Cornpreesibilities,
Thene;trendofdensitych nges
mind thatat thistemperaturehe oil/gaamixtures
withincreasingressurewillde$endon therelative
were relativelyviscousand adhered
tO the windows
magnitudeof thesetwoeffects.
of the cell.
This made it hard to positively
identifythe}.esenceor absenceof a separateaolid
As mentionedbefore,sampleswere takenfromthe phase.
topandbottomof thecellsat eachtemperaturend
pressureand, as shown in Figures 2 to 4, a
On the other hand,
very clear indicationsof
differencewasobservedin the gascontentof these
solidsprecipitationerenotedat 284°F(14@C):As
samples. Nevertheless,ittle,if any,difference
soonasC% wasdissolvedin theoilat 400 pai(2,8
was observedin thedensitiesof thesesamples,This
MPa) fine particleswereobservedto adhereto the
,s not surprisingin view of the very weak windowof thecell.
dependenceof the densitiesof the mixtureson the
amount of C% dissolvedin the oil.
This also
indicatesthatverylongtimeswillbe requiredfor
SARAAnalysis of Oil Samples:
thesephasesto separateout completely.
Samplesof oil obtainedat the vario;;d~
saturation pressures were centrifuged
Viacositiea of Oil/~ Mixtures:
Saturates-Aromatics-Resins-Asphaltenes
(SARA;
ana,lyeisas performedon them,The centrifugation
Theviscositiesftheoil/C~ mixturesareshown
step was to sepsrateout any precipitatedsolids
in Figure6.
It is immediatelyevidentthat the
that remsinedsuependedin the oil sample.The
dissolutionof C% intothe oil.has the effectof resultsare discussedbelow.
effectivelyeducicgitsviscosity.Forexample,at
69,@F(21°C)theviscosityoftheliveoilis21,680 69,6’OF21°C)Oil Samrdes:
cp (mPa.s),whilethatof theoil saturatedwithC~
at 1,500psi.(10.3MPa) is about 403 CP (mPa.s),
Analyaes were carried out of oil samples
which is equivalentto a 53-foldreduction. The
obtainedat differentC% saturationpressuresat
effectis not that dramaticat 2840F(14CPC):The 69.@F (21°C).Sincenoasphaltenesereseenin the
viscosityof theliveoil is about19.6cp (mPa.sl~ windowof thephasebehaviourcellat 69.80F(210C),
while that of the C$-saturatedoil at 1,500 psi
and in order to minimizethe numberof samples,
(10,3MPa) is 9.2 cp (mPs.s),givinga viscosity
equalvolumeswerewithdrawnfromthe topand bottom
reductionfsctorof 2.1.
of the teatcell. These sampleswere thenmixed
together
and
analyzed for their saturates,
Anotherimportantobservations that,whenthe
aromatics,resinsand asphaltenesontent,
oil had been put thr~..?hhe pressurizationIteps
thendrawnbackto 400 psi (2.8MPa),the viscosity
The resultsare sumarizedin Table2.
It
iS
was lowerthanthatof theoil originallysaturated
evidentthatthemostsignificanthangeoccurredin
withC% at 400 psi (2.8MPa).Thisis a consequence
theasphalteneaontent.Thisremainedunchangedat
of the fact notedabovethst the oil retainedC
%
about15%fortheoil/C02mixturesbelow900psi (6.2
preferrentlallyo methanewhen‘i wastakenthroug
MPa) which is slightlyabove the Iiquification
the pressurization-iberationcycle. pressure of C$. The asphaltenecontent then
increasedto about 21% at pressuresover 900 psi
The viscositiesf the fluidsat thetop of the (6.2 MPa) an.iremainedthe same up to 1,500 psi
cells were, in general,lower than those of the (10.3 MPa). It also remainedthe same after
fluids at the bottom of the cells. This
iS depressurizationrom1,500psito 400 pai (10.3to
consistent with the gas/oil
ratioe of these
2.8MPa). Sincetherewas no vieualindicationof
phases,as notedinFigure2, andtheirC +content,
a solid phase separationwithin the cell, this
aa notedin Figure3.
increasein asphsl,teneontentmay be due to a
redistributionf the differentcomponentsof the
crude oil in the presenceof liquid~, i.e.the
Swelling& FormationVolumeFactors:
heavier
fractions
enriched
with
colloidal
The swellingand formationvolumefactorsof the
asphaltenesgraduallymigrateto the bottomof the
cell forming two distinctlayers.This can be
heavyoil/C
2
mixturesare showninFigures7,8 and explainedby the preferentialvolubilityof non-
9. It is c ear thatthe dl.saolutionf C% within
polarcomponentsof the heavycrudeoil withinthe
theoilcauaesswellingand amountof swellingwhich
liquidC , The resultsshownin Figure:. and 6
occursat69.@F (21°C)is 8reaterthanthatobserved
?
onfirmt f.a,
At
pressuresabove the Iiquifaction
at 284°F(14@C),
Ten percentswellingla achieved pressureof ~ the sampleswithdrawnfromthe top
at a C% pressureof 1,200psi (8.3MPa)at 69.80F
of thecellhaveconsiderablyighergasloilratioa
(21°C).Thiaienot significantlyncreasedhenthe
(GOR’s)thanthosefromthe bottomof thecelland
C% pressureis increasedfrom 1,200to 1,500pai
the viscositiesof the bottomsamplesare greater
(8.3 to 10.3MPa).
In generaltheseresultsare
thanthe topsamples, Sincehigherviscositiesre
similarto thosereportedbefore,e.g.10% swell g
$?
always
associatedwith the higher asphaltene
was observedby Sankuret al, forWilmingtonoil ,
content,therefore,thisis clearevidencefor the
presenceof two layerswithintha cell.The same
trendwas observedfor the sampleobtainedafter
Precipitation of a Solid Phase:
depreaaurizationrom1,500psi to 400 pai (10,3to
2,8 MPa), This can be explainedby the high C%
No indicationof the precipitationf a solid
content of the oil after the depressurization
phase(heavyendsof thecrudeoil)was observedat
processand the fact thatthe recombinationf two
69,@F (21°C).
Nevertheless,t shouldbe kept in
layerais a slowprocess,
---
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SPE20037
S.G.SAYEGHANDM, SAWAR
5
A finalcommentbasedon theseresultscan be
made at this point: There was no asphaltenes
precipitationr solidphaseseparationbservedat
the higherpressures(900- 1,500psi, or 6.2 to
10,3MPa).
However,in orderto avoidany possible
negativeeffectof the asphaltenesredistribution
procese,it is recommendedfor the presentsystem
thatC$ shouldbe injectedintothe reservoirat
pressures below its liquefaction(saturation)
pressureso thatit remainsas a 8aa.
284°F(14&C) OilSamples:
Some asphaltenesprecipitationwas observed
while saturatingthe heavyoil with C% at 284°F
(14@C), Therefore,separateeamplesfrom the top
and bottomof the experimentalellwerewithdrawn
at each saturationpressureand were analyzed
separatelyas llstedin Table3.
Eventhoughthere
was
some differencein some of the physical.
properties(such as viscosities)of the top and
bottomphasesof the heavyoil/C
mixtures,SARA
analysesindicateonly a minor d fferencein the
asphaltenecontentof the samples(l-2%). Since
allof thevaluesforasphaltenesontentof topand
bottomphase are very close to the originaloil
(within1-2% differencerange},it can be also
concludedthat the amountof precipitationuring
thetestwas not significant.
DISCUSSION
The phase behaviorresults describedabove
indicatethat the application
of c% for the
stimulationf heavyoil productionis feasiblefor
the systemstudiedhere.This is indicatedby the
53-foldreductionintheoil’sviscositywhen itwas
saturatedwithC% at 1,500psi(10.3MPa)and69.@F
(21OC)*
The resultsalsoindicatethatC% is more
effectivein reducingthe oil’sviscosityat 69.80F
(21°C)than at 284°F(14@C). Thus to makeuse of
Cq’s viscosityreducingcharacteristicsit is
adviaableto injectit whenthe reservoiris at ita
originaltemperature(69.80For 21°Cin this case)
ratherthanduringorafterinjectingsteamintoit.
Accordingly,heindicationsrethatC02canbeueed
as a well stimulatingagent by, for example,the
huff-n-puffprocess, or can be used as a
pretreatmentgentpriorto steaminjection.
Solids(crudeoil heavyends)precipitationay
pose a problem in the application
of C% in
con~unctionwith steam flooding,and thiu point
needsto be takenIntoaccolmtwhendesigningsuch
a process.This problemcould also appear in a
firefloodapplication,inceoil andC% will be in
contactat hightemperature.
Successfulapplicationof C% to enhancedoil
recoverydependsupona largenumberof operational
and reservoirvariables,Theseincludethe amount
of C% injectedperwell,itsrateof injection,he
lengthof soak period,
the absoluteand relative
permeabilityharactcristicaf the reservoir,the
presenceor absenceof a mobilewatersaturation,
and reservoiremall scale heterogeneities.
he
effect of
these fhctors on the displacement
efficiencyof the process can be examined by
laboratorycore floodsusing reservoirmaterials,
temperatures ressures,and flowrates.
Considerationshouldalso be given to other
factors such as reservoirheterogeneities,he
effect of gravitysegregationon the volumetric
distributionf theinjectedgas,and theextentof
the presence of natural fractures within the
reservoir.Ifthepresenceof an extensivefracture
network is found in
the reeervoir,
then
considerationouldbe givento applyinga ~ fo~
process.Injection.fC~ in theformofafosmwil.1
minimizethequickC dissipationntothefractures
%herebyaneffective
?
dispersionithintheoil in
thevicinityof thein ectionwellwillbeachieved.
(1)
(2)
(3)
(3)
(4)
(5)
CONCLUSIONS
C% dissolvedto a considerablextentin
theheavycrudeoilat 1,200psi(8.3MPa)
about303 scf/bblor 55 ~/m3), and caused
and 69.@F (21°C)(the as/oilratiowas
someoil swelling(about10%)as wellas a
significantiscosityreduction(about25-
fold),Whenoil was saturatedwithC% at
1,500psi (10,3MFa)at 69.&F (21°C)the
decreasein viscositywas about 50-fold
(fromabout22,000cp to about400CP).
The viscosityreductionof theheavycrude
oil by C% at 284°F (14@C) was not as
significantaa at 69.80F(21°C)sincethe
viscosity of
the
oil
was already
substantiallyreduced by the elevated
temperature.
Changesin thedensitiesof theheavycrude
oil/C~ mixtureswerenot significant.
In order to use C% as an effective
viizosityreducingagent in the present
re~ervoirsystemit ia advisableto inject
C% when tl’sreservoiris at its original
temperatureratherthan duringor after
stesminjection.
If asphalteneprecipitationrovesto be a
bigproblem,theinjectionpressuresshould
be adjustedso thattheC% willremainin
the
gaaeous
form at the
reservoir
temperature(i.,e.elow its liquificction
pressure).
AccordinLtothesefindingstheapplication
of C% for enhancedoil recoveryin the
heavy crude oil reservoiris feasible.
Viscosityreductionwouldplaya majorrole
in improvingproductivityspeciallywhen
it is usedas a wellstimulatinggent.
ACKNOWIJiWR4ENE
Theauthorswouldlike to thankEsaoResources
Canadaforgrantingpermissiono publishthiswork.
Acknowledgementis also made to J. Najman for
performingthe phasebehaviormeasurements,nd to
B. Fraserforhelpin preparingthismanuscript.
—.
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6
PHASEBEHAVIORPROPERTIESOF
cO,/HEAVY
OIL
MIXTURES
FOREORAPPLICATIONS
SPE20037
&
REFERENCES
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K.,
Setari,A.,and (11)
Maini,B.B.,and Sayegh,S.G,:“Laboratory
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?
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s
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CIM,Calgary,Alberta,Mey 3-6.
m
7/21/2019 20037-Phase Behavior Properties of COHeavy Oil Mixtures for
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a
9
Tsblt 1: Crud* O il P ropo rei .s
S a t ur a t i o n prasaura psi (fSpa)
D ma it y @ 69,
8 F
(21*C ) , 6/m l
Do n*i cy @ 2 S4*F 140” C), c /m l
Viscosity @ 69,8*F (21*C ) , 0p (m P&D)
Viscosit y @ 286*F (140*C ) , 0p (MFa.s)
fhs/oU ratio @ 69. S *F (21W, scfmbl (m’/m*)
C aC IOil ra io @ 2S 4° F (140’C ), scf/ bbl (m’ /M’)
Av@ra@ sohaular wci& IC
400 (2, 8)
0.989
0.990
0.905
0.903
26 , S 46
21,600
23.6 19,6
25. 3 (4. 5)
17.4 (31)
62S
1) S tock-ta nk oil w m rt coa bin.d with metharm
‘Mbla 2: SAP A Am lym s
of O l
S a a pl o a
from
67. S *F (21-C ) T* st s
Pr9mwre
Pt*amura
S a t ur a t a e Arout l ca
Rasi ns
pJ i n P a
8 9
—.
—— .
23.87
32,58 27.08
400
2?.89 29.32 27.32
400
2.76
28.35 32.06 25.07
1,200 8,27
25.05
32,82
21.15
1,500
10 34
24<20
33,16
22.26
400
2.76
23.77 32,51
22,04
Anphnl t*na8
\
14.47
14.95
14,5.2
20. ?s
20.39
21,68
Ta bla 3: S AR A An aly llm
of
Oil SaaplBB f r o m 284*F (140’C ) Tm m
Pr*@lutw
Pr9mur*
amph
s&turflt*l
Aromat lca
L-a.xcion
AlalLJl12AL—QL—~ ~
o
400
400
400
900
900
1,200
1,200
1,500
a,500
400
400
0
2,76
2.76
2,76
6,20
6,20
8,27
8.27
10.36
10. Y I
2.76
2,76
ToP
TOP
TOP
Bott om
TOP
Bott om
TOP
Bottrm
T(IF
Bottom
lop
Bott om
25,87
22,80
2?.02
26,24
27,42
26,33
26,54
25,54
26,00
26,16
23.44
23,76
32,58
31,17
3242s
32.91
31.01
32.9?
31,19
33.08
35,31
27.7)
34,19
33,34
27.08
32,66
26,21
26,31
27,06
26,00
27,61
26,05
25,36
29,83
2S,36
26.92
14,47
13,37
14,41
14.56
14,s1
14,20
14,66
15,33
14.33
16,30
14,00
15 98
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4. Ablowe PrWnumTroldllc+r
e,t.owvotuo vltcomttor
e, Thwmotta d oven
10 ,H1. 1VOIUOVISwmWW
5. SamplbPort
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12, Dllt9fwIt Id Pf9WJI*
6 .Wltdod Cal
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W,wator
R*wr*Olr
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q4,~pen Ditploctmtnt
0. BJP4st Llns
HEAVY OIL PHASE BEHAVIORAPPARATUS
60
t
‘E 40
1-
.
6AS/OfL RATIOSOF FROGLAKE OIL/COe
MIXTURES.
‘:&
400
f ig<2
Fig,1
BC, Bottom
I
1
1
I
1
I
1
02468
10 At MPo
PRESSURE
ml
IL
+,CH4
c, Top
...
21°t2,
30ttom
‘.
.,
a..
A 140*C, Top and Bottom
90
cog
n stock-tank
011
0
Recombined 011
$ 80
LL
~ 70
\\
40
1- W
o~
I
I
I
I
400
900 1200 1500 Psl
1 I
I
1~
0246810
12
Ml
w
c
.,
w.
10
‘lz
MPo
e----, ,-”
2s4
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,ooo\c,4,~ I
*E
1+1
2’1°,
Top and Bottom
\
50
A
140@C, Top and Bottom
g stock-tank Oil
C
D Recombined Oil
G
z
u
n
cl-h
C02
900 ““-’’””’ - _
,5,L
o
400
‘“OOOO-
1
I
1
I
I
I
I
024
10
42 MPa
PRE?SSUI?E
WVSITIESOF FROGLAKE OIL/CO~
MIXTURES.
L
I
I
1
1
I
0246
e 10 12 MPo
PRESSURE
VISCOSITIES OF FROG LAKE OIL/CO~
MIXTURES.
F1’&6
Fl@.5
‘E
21”C
‘ 4.20 -
A
140°c
%
m Stock-tonk011
“ 1,18 -
Recombined011
g 1,16 “
1-
a 1,54
“
L 1,12
-
g ,,, f):
g 1,08- CH4 ,,;”
4
E
1,06- *9’ w~~
1 04- .“””
a 1,0z ~,,””’” CH4
E
1,Of&”’
,,, ,., .O,
A
200 400 600 800 10001200 1400 16(
Psl
1
1
1
I
I
I
I
I
o
2
4
6
e
IO MPo
PFWSURE
FORMATION VOLUMEFACTORSOF FROG LAKE OIL
/COe
MIXTURES.
fig,7
I
(’
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1,11-
0 21”C ToP
1,10 -
021*C Bottom
A 140°C ToP
‘~ 1.09
-
A 140
C Bottom
‘E 1,08
-
& 1,07
-
0 /
~ 1,06
-
/
E 1.05 -
~ 1s34 “
~ 1,03
-
~ q ,02 .
1 Ofl
I
I
1.00~
1
i
I
I
10 20 30
40 50 60
MOLE PERCENTC02
SWELLINGFACTOIR VERSUSCOaCONTENTW FROGLAKE O/L/
COa M/XW?ES,
1,10
A 140”C
‘~ ,,09
210C
;fi
0“””
‘E 1.08 /0
~“ 1,07
/0
g q,)6
2 1,05 /“” ..’
j 1,02 “ e“/
~ 1,01
-
1
I
AM
I
1
1
I 1
1
800 100012001400 1600P61
-O-”-2ti 400 600
I
I
1
1
1
I
1
1
1
I
I
o
2
4
8
10 MPa
PRESS:RE
SWELLINGFACTORSOF FROG4AUE O/L/COe MIXtURES
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