20037-Phase Behavior Properties of COHeavy Oil Mixtures for

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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.



2

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.



“

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

-



8

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,

---



.

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.

—.



6

PHASEBEHAVIORPROPERTIESOF

cO,/HEAVY

OIL

MIXTURES

FOREORAPPLICATIONS

SPE20037

&

REFERENCES

(1) Stright,Jr.,D.H,, Aziz,

K.,

Setari,A.,and (11)

Maini,B.B.,and Sayegh,S.G,:“Laboratory

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Techniquesfor Investigatingecoveryin

Bottom-Water Undersaturatedviscous oil Heavy Oil Reservoirs”,presentedat the

Reservoirs”,PT (October1977)1248-1258, 1983 Advances in

Petroleum Recovery

TechnologyConference,Calgary,Alberta,

(2) Bells,E.,Bilgeri,d,,Causin,e.,Chierici,

May 30-31.

G.L.,Gili,V.,

Mirabelli,G., and Sozzi,1.:

tlpiroPoeavy Oil Accumulation,driaticSea

(12)

Sayegh,S.G.,and Maini,B.B,:“Laboratory

Italy, Study of an ExploitationProcess”,

Evaluationof the ~ Huff-n-PuffProcess

presentedat the 19822nd EuropeanSymposium

for HeavyOil Reservoirs”,CPT (May/June

on EnhancedOil Recovery,Paris,November

1984)29-36.

8-10.

(13) Vasquez,J.M.:“Laboratorynvestigationof

(3) Miller,J.S., and Jones,R.A.: “A Laboratory

theBehaviourof C% withVenezuelanCrude

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HeavyOilafterC~ Saturation”,aperSPI@OE

oila”~presentedat the1983International

Symposiumon CC+ EOR, Budapest,Hungary,

9789 presentedat the 1981 Second Joint

March8-11.

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(14) “AGIPBoostsProductionat Ponte Dirillo

Field with C% EnrichedGas”,.Enhanced

(4) Sayeght S.G., Rae, D.N., Kokal, S,L., and

RecoveryWeek,(March9, 1987).

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Properties of

Lindbsrgh

Heavy

?

(15) Reid,T.B,,andRobinson,H.J.:“LickCreed

Mixturest’,resentedat the 1989~’~th,nnua

MeekinSandUnit Immiscible-Waterflood

TechnicalMeetingof the PetroleumSocietyof

Project”,paperSPEIDOE9795 presentedat

CIM,Banff,Alberta,28-31May.

the 1981 SPE/DOE2nd Joint Symposiumon

EnhancedOil Recovery.

(5) Chung,F,T.H. Jones,R.A,,and Nguyen,H.T.,

“MeasurementsadCorrelationsof thePhysical

(16) Nemeth, E.: “Mein Results of Field

Propertiesof C~-Heavy CrudeOil Mixtures”:

ExperimentEateblishingxploitationith

paperSPE 15080,presentedat the 198656th

C% in Hungary”,

CaliforniaRegionalMeeting of the SPE,

presentedat the 1983

Internationalsymposium

on ~ EOR,

Oakland,CA, April2-4.

Budapest,Hungary,March8-11.

(6) Jacoby,R.H,: “Phase Behavior of Light

(17)

Szittar,A,, and Biro,Z.: “C% Injection

Hydrocarbon-Heavyil or Tar Systems,and its

Projectin Southwestungary”,preaentedat

ApplicationoRecoveryProcessed”,nterstate

Oil CompactComm.Bull.,vol.27, no. 2, pp.

the19831nternationalympositimon~ EOR,

50-56,Dec.1985.

Budapest,Hungary,March8-11.

(18) Owete,S.0.,and Brigham,W.E.: “I?Iowof

(7) Shelton, J.L. and Morr.1.a,,E.: “Cyclic

FoamThroughPorousMedia”,U.S.Dept.of

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Report No. DOE/SF/1564-6

IncreaseRatesfrom Viscous-OilReservoirs”,

JPT (Au6.1973)890-896,

(DE8401241O).

(19)

Dandge,D.K,,and Heller,J.P.:“Polymers

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ParametricStudy of

forMobilityControlin C% Floods”,paper

the C+ Huff-n-Puff

SPE 16271 presentedat the 1987 SPE

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Oilfield

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4-6,

Sept.23-26.

(20)

9 Patton,J.T.,Sigmund,P,, Evans,E .,Ghose,

Livesey,D.B.,and Toma,P.: “Filterfor

s

SeparatingDiscreteSolid Elementsfroma

and Weinbrandt,R,:

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Fluid Stream”, U.S. Patent 4,434,054,

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February28, 1984,

paper SPE 8897 presentedat the 1980 50th

California Regional Meeting of the SPE

(21)

Pasadena,California,pril9-11.

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Emanuel, A.S.:

“A LaboratoryStudy of

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104,

81-32-42presentedat the 1981 32nd Annual

TechnicalMeetingof the PetroleumSocietyof

CIM,Calgary,Alberta,Mey 3-6.

m



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

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400

2.76

28.35 32.06 25.07

1,200 8,27

25.05

32,82

21.15

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400

2.76

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Ta bla 3: S AR A An aly llm

of

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Pr*@lutw

Pr9mur*

amph

s&turflt*l

Aromat lca

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o

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2,76

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ToP

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Bottom

lop

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25,87

22,80

2?.02

26,24

27,42

26,33

26,54

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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

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26.92

14,47

13,37

14,41

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VISCOSITIES OF FROG LAKE OIL/CO~

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PFWSURE

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MIXTURES.

fig,7

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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

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& 1,07

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10 20 30

40 50 60

MOLE PERCENTC02

SWELLINGFACTOIR VERSUSCOaCONTENTW FROGLAKE O/L/

COa M/XW?ES,

1,10

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‘~ ,,09

210C

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PRESS:RE

SWELLINGFACTORSOF FROG4AUE O/L/COe MIXtURES

20037-Phase Behavior Properties of COHeavy Oil Mixtures for

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Transcript of 20037-Phase Behavior Properties of COHeavy Oil Mixtures for