design and optimization alkaline

7/26/2019 Design and Optimization Alkaline

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SPEH)OE

oolstyof

U.S.Oapmtmant

Potrolwn Er@rrasra

of Ermrgy

SPE/DOE 20238

Design and Optimization of Alkaline Flooding Formulations

T.F t. French and T,E, Burchfield, NatL

Inst. for Petroleum & Energy Research

SPE Membsrs

This paper waapreparedfor preamlatlon at the SPE/DOESevanlh Sympoalumon EnhanoadOil Raooveryheld In Tulsa,Oklahoma,April 22-25, 1SS0.

Thlapaper was aeleotedfo- preaarrtatlonby an SPEProgramOommlffeefollowing reviewof informationcontained in an abatractsubmittedby the author(s).Contelt, of the paper

aeprewnted, have not bean eviawadby the

Soolety

of

PetroleumEndnwrs

and aro subleofto mmectlonbYthe author(a).The materfalt~ PreWnf@ doesnot n~~*~lY ~fl~t

anYpoaitlonof theSooietyof Pmolaum

Englnwra,reofficers,ormembara.ParmraxewnteddtspE mwtinware8ubl@towbli~tionre~ewWEdltofialQJmminwb

f fhe ~lav

of PetroteumEnglnwra.Perrniwionto oopyis rwtrlotd to anabatrwf ofnotmorethanSWwords.Illustration maynotbe00PIed.Theabafraotshouldoontainoormplouousacknowtadgme

of where and by whomthe papar is presented.Write PubllcationaManager, SPE, P.O. Box S3SSS6,Richardson,TX 75CSXWSS.Telex, 7S09S9SPEDAL.

Ths firtalseotionof this paper Isan exampleof how screening

criterfa,phaaebehaviorteats, and oorefloodscan be usedto design

The state+f-the-art for alkaline flooding technology is the

andoptimizean aikalineflood for a speoifkcoil field, The example Is

injeotion of combinations of aikaiis with synthetic surfactants.

for the designof a Iow-PH,surfactant-enhancedaikaiineflood in the

Surlaotant-enhanced aikaiine flooding formulations with icw-pH

RangerZons of the Wilmington(CA),ffeld,where a high-pHaikaline

aikaline agentshave potentiaifor irforeasedoii recovery. They reaot

ficod was previously ccnductsd, That projeot ertoounteredsevere

iess with reservoir mirmrais and facilitate the use of iow

probiemswith aikeli consumptionandcoaling. A bw.pH aikali (such

concentrations of surlaotants because surfactant adsorption is

as NaHC03 or NaHC03 + Na2C03) in ccmbinatbn with synthetic

reducedin the presanoeof aikalineagents.

surfactant should be effective for producing incremsntai oii in the

RangerZone of Wilmingtonfield, Problemsassociatedwith high pH

Laboratory experiment and resuits from field projects have

fioods, such as Intractable scsies and high consumptlcm,wiii be

been evaluated and used to establish guidelines for designing

mitigated.

optimumaikaiineficods. Fora reservoirto be a osndidatefor alkailtte

flooding,the reservoirshould ccntakr iittleor no gypsum,the divaiertt

~

ion exchangeoapacityshouldbe les~than 5 maqkg, andthe in situ

pH shoukf be greaterthan 6.5.

Aikaiine agents have an appeal for enhanced oii recovery

because of their iow cost and favorable performance in laboratory

Two optimizedaikalinesystemswh chexhibittypicai inteffaclal

tests.

Aikaiine ag~nts mobiiize oil eff iciently in laboratory

tension (iFil behavioraredesofibed, Onesystemwasoptimizedwith

experiments: however, fieid applications of aikai ine fiooding

a very iow acid (acid number = 0,13 mg KOHlg) crude oil from

processeshave usualiy beendisappdnting.

Delsware-ChiicfereOK),field, The other systemwasoptimizedwith

an acidio

(aCid

number= 1.59 mg KOH/g)crudeoii from Wilmington

In the past 60 yeara, more than 50 alkaiine fiooding fieid

(CA), oii f ield. A mixture of synthetic sur faotantand low-pH alkaii projects have been initiated in the United States. Deapfte this

producedbwer ilV andsustainedlow iFf bnger thaneitherreactant

extensive field testing, aikai ine fiooding ie not yet feasible as a

alone. This effsotwas obeenrsdwiththe ackiiocrudeand the slightly

commercial.soaieoperation. in many of the tests, aikaiine agents

acidic crude. it was ooncluded that surfactant-enhancsd alkaiine wereextensivelyoonsumadby mineraidissolutionand bn exchange

fioodirtg with IOW-PHaikaiis shows promise with both acidic and

reaotions,andthe depositionof scaleat prcductbn weliswas severa.

siightiyackfiooiie.

Recentiy,Wyoming,Louisiana,and Texashavebeenthe most

Synthetic surfaotant is an expensive component of icw-pH

active statesfor aikaiineflooding. Caiifomiawas a major site at one

aikaiine fbcding formuiatione. Dilute(0.1 .0.2 %) oortcenfratbnsof

the added synthetio surfactant are being used in some current

time, but reoentEORpilotteatson the WestCoast have not included

aikaiineflooding.

aikaiine flooding field projeots. Laboratory resuits ehowed that

sur factant iosses by adsorpt ion are reduced under aikaiine

Evaluationof past aikaiinefieldtests is difficultbaoauesof the

conditions. Loseesby precipitatbn shoufdaiec be reduced due to

the bwering of divalentbn ocnoentrstionby aikalinepreflush.

scarcity of reported information. Data on reservoir mineralogy,oii

properties,and brine wa%es areoftenunavailable. HOIfever,when

Referertossndiiiusfrationatendofpaper

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DESIGNAND OPTIMIZATION OF ALKALINE FLOODINGFORMULATIONS

SPE/DOE20238

publishedflefd resutteare oomblnedwith laboratorydata, then there

laa auffiolenfiylargedatabaw to cfeveiopgoodcriteriafor aoreenhrg,

deslgnlng,and optimizingalkalinefloodingformulellons.

This paper is dMded into three seotbna: the rote of syrtthetio

eurfactants in alkaline flooding, the use of aoreening crtterta to

evaluate fiekf prospeots, and the design and optimization of a

chemicaiformubtbn.

t

P~

PhaseBe;wior

Equal volumes (4 mL) of Wilmingtonoil A and aqueousphase

were sealed in 10-mL grsduated ampoules. The samples were

placed in an oven at 52 C. Observationswere madeafter 1 week.

Thesampleswereobsewedet that the andevaluated. Theaan@es

were then evatuatedwhile being shaken. Finally,the sampleswere

evaluated again after 1 more day. The observation while shaking

providedinfonnatbn aboutthe type of emutsionformed (oil- n.water

or water-ln+ii), the easeof emufaifbatlon,the stabilityrdthe emulsbn

(while shaking), and the amount (qualitative)of 011em~dslfied. The

final evak@on (1 day after shaking) provides wfditional data on

emulsbn stability.

The emulsions formed were evaluated according to the

followingcriteria

o

Novisibleemuisifkation

1

Blaokemulsbn

2

Brownemulsbn that changesto black

whileehaking

3

Brownemulsbn

4

Brownenwlsbn oontalning>90% of

the oii inthe sample

Higher values of emuision quaiity correlate with greater

interracial activity and nearness to optimal conditions. Thie visuai

method for determining optimal saiinity for producing interfaclali

activeeyatemsis onlyslightlydifferentfrom thoseused by others.2

J

Interglacialensbn

Irrterfacialpropertiesof seleotedsystemswere measuredwitha

spinning drop interfaclal tensbmeter at 52C. The transient iFT

behavior of nonequilibriated samples was monitored over a time

intervalof severalhours.

SurfaotantTransporlthrough PorousMedia

Unfired, oil-free Berea sandstoneoores (25,4X 3.7 cm) were

mounted in Hassler-typeooreholders. Frontal advance rates were

approximately0.5W(I (0.152rnld),provfdinga oore residencetimeof

about 1.7 days, Surlaotanttransportthrough the oii-free oores was

monitoredqt 52C (overwontroiled).

SilmTube Sandpaoke

Slim tube experimentswere performedat resewoir te~erature (52

C) to determine alkali consumption while propagating a pH front

through Wilmington sand, The slim tubes were oonstruofed of

stainlesssteeltubingwith anouterdiameterof0.535cm andan inner

I

diameterof 0.457cm. ~ tubes were 50tt (18,23m) in terrgthand

were paokedwith tofuenwrfraoted Wifmingfonsendto a porosityof

0.28%. Th8 sandpacks were eaturated wNI Mte folkwed by

Wilmingtoncrude

011A. After watertbodktg, tke afkalineaolutbrts

were injaotedat a frontaladvenoerateof 2 tutl (0.61nvcf)oDifferentfaf

pressuresrangedfrom 1.0to 3.0 paiM (6.9to 20.7k P rn).

Oii Dis@eoementTeats

Oil dispfaoementteatswere conduotedat reeewoirtemperature(52

C) in aandpacks (25.4 by 3.7 om) made with OfeanSdWWmington

serwf.Theooreswere peekedinfOTefion~ afeeveawith Tefbno end

caps am then piti irra Haaafertype ooraholder. E% wepaokfrrg,

the sandwas olemed bySoxhfetextreoth wtthtolueneamfwas not

fired. After determining initial brine permeability, the oores were

saturatadwith tittered Wilmingtonoif A andweferfbodad to residual

oil saturetbn. Chemicalslugswere injectedat a frontal edvanw rate

of 1fVD,

Surfactarrt

Anaiytbal methods used for measurement of surfaotant

oonoentratbn were two-phaeetitretbn and HPLC. The two-phase

titratbn was described by Rosen and t30fdsmith,4and the HPLC

prooedureissirnliarto that desoribedby HofmanandAngstadt,6The

wavelength used for absorbenoe measurementof PetmatepB-100

surfactant was 222 nm, whbh is very close to the wavelength

selectedby Hofmanand Arrgatadt.

Alkalinity

Effiuent sampleewere oolleotedin 5-ml incrementsand oerrtrituged

before the volume of oil ooifeotedwas determined. The aqueous

phasewasthen eeparatedandanaiyzedfor alkalinityby titratbn to pH

4 with0,1N HCL

ElementalAnalysis

The effluents were anaiyzed for siiloon with atomic absorption

spectroscopy,

Thebwer pHalkailsottenfailto aohievetheultra-bw iFTvalues

necessaryfor sfgnitbant rnobiiizatknof oil. Itwasdiscoveredin 1955

that the additfonof very small cmoentrafbna of aynthetiotrurfaotant

to alkalineSObtiOnscoutdsignitkantty i~rove transientIFTbehavbr

andoil rrmbiiizatbnwithwetkty atkalinechemkals.6 Twoexamplesof

optimized alkaline systems are presented whkh exhibit fypbel IFT

behavbr with andwithoutaddedaurfaotant.

AcidicCrude

The first example isfor a pH 9.3 mixtureof 0.095 N NaHC03

and 0.095 N Na2C03 that was tested at 5P C with oil B from the

Ranger Zone of Wilmington, CA field. The Wilmingtonorude oil is

acidio(Table1) and quite reaotivewith aikaii. F&l showsthat alkali

oeuseea very rapid bwertng of IFT to 55 @4/min Only2 minutes;

however,1~ baginaincreasingimmediately. Within32 minutes,IFT

inoreasedto 500 @N/m.

When 0.1% Neodol 25-9 afoohol ethoxylate Surfactantand

alkaliwereoombfned(Fig. 1),the reauttwas a rapiddeoreasein IFT,

folbwed bya sustained,verysbw, irwreasein IFT. Theminimum1~

was 4 @Urnfor the oornbinatbn of aurfaotantand aikali, much lower

thanfor surtaofant(shownin Fig.2) or aikaliabne. The iFT withthe

oombinatbn of syntheticaurtaotantandalkaliwasatllibebw 50 @J/m

after 16mirrutee.

616


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SPE)DOE 20238

Trov R. French and Thomas E. Btarchiield

3

--

Theconcfusbndrawn fromFigs.1 mcf2is0ratwnhWilmfngton

011, conWMkm of sytlhetk aurfectantandatkaliproducesbwer In

and sustains fewer lfT fonger, than either component alone. It

appearsthat for thisoil, verykw In lapradcmlnantfya resultof the

natural aurfactanfs produced by reactions wlfh the alkall, ml the

sustained low IFT is prtmari ly the rusuft of the added synthetto

eurtactant.7

Low-AcktCrude

The second example is for a light o %omDelsware-Chikfera

(OK),fkdd, (SeeTabfe1,) The alkaliusedwas a pfi 9.5 mixtureof

0.049 N NaHCO~,0.0078 N Na2C03, ml 0.0325N Na2HP04, The

experiments were conducted % S2 C, the same temperaturethat

was used for the heaviercFJde. The Delswara.Chllderaoil is stightfy

acidicand relativelyunreacifveto akall. Fig,3 sh6w8thatafkaliabn3

producedonfya smallreductbnin in.

The additbn of 0.1% PetrcetepB-100anionicsurfactantto the

alkaliresultedIna very rapidbwering of lfT to a bw value,whkh wee

sustainedfor a longperfcd. The minimum lFl of 2.9 mim for the

combinationof synthetfcsurfactantand alkali waa much bwer than

that & $evedwith either component alone. The IFT behavbr for

0.1%aurfactantabne is shownin Fig.4.

The resutfswith the Delsware-Chltdemcrude indicatethat even

for crude olla with very ~w acid numbers, the combinationof alkali

ati a bw concentratbn of syntheticSuffactantcan producevery bw

Il=rVsluee.a

Synthetic surfactant is an expensive component of IOW-PH

alkalinefboding formulations. Forthis reason,onlyxfilute(0.1-O.2%)

Concentration of added surfactant are used In current field

[email protected] $ As ahcwn above,very low concerrtratbns of surfactant

n alkal ine solution are sufficient to produce an ultra-low IFT. A

potentialproblemis that the surfactant,at these low levels, may not

propagatevery far Into an oil raeewolrbecauseof lossescaused by

preclplfetbn, adaorptbn, andphasetrepplng,

Precipitation

Calcium and magnesium ions present irr reservoka can

precipitate the aurfactants used in EOR applbatlons. Alkalis are

effectfve for reducing the levels of divalent ions in petroleum

reaervoirs,7*f~-11The effectivenessof different alkalis for reducing

dlvalent ion levels are: hydroxide < carbonate < silicate. The

preferred InjectionstrategyIs probablyto use an alkalineprefluahto

reducedivalentbn levelsbefore Injectinga forrnulatbn that con ains

surfacfant,

An example of the use of sodium bicarbonate in a preflush ie

shownin Fig.5.12 Sandstonecoreswere initiallysaturatedwith brine

contakrlng1,000ppm eachof cskium and magnesiumions. With a

aallne preflush of ecdlum chloride, calcium and magnesium Ions

persisted In the effluent long after the original brfne was displaced

from the core, while the injection of sodium bicwbonate reduced

fhek concentrationmucheartler. Onfy0,25 PVof l% NaHC@ woutd

be requiredto preclpfteteallof thecalcium(aa CaC@) in a brfnethat

contains600 ppmof caklum Ions.

Adsorption

SurfacfantlevelsIn an injectedsolutbn can also be reducedby

adsorption onto reaewoir rock. Numerous researchers have

meaaured the adsorption of anionio aunactants under alkaline

condltiorre. These reauftscan be summarizedby stating that alkali

reducedthe adsorptbn of anbnk surfactantsonto pureclay minerals

as much as 93% and

reduced

adsorption 7 to 49% when reservoir

sandstoneswere used.8*lo~12.13

Teble2 summarizesthe resuftsof severalcorefkods at two pH

levels. hr oil .free, high permeabili ty Berea sandstone cores,

eurfecfantretention (by edaorptbn) was reduced by 49% when the

pHwas Inmeasadfrnm &3 to 10.2.

The questbn of how much surfactant Is rqtrlfad for 90Cd

propagatbn fnto a particular reservoir has not been aafkfacfotity

answered, Measurements on the adsorptbn O?two anionic

s::actanta onto WilmingtonRangerZone sand aregtvanfn Table3.

Cabulatbna based on these data indfcetethat about 2 PVof 0.1%

surfacfant aofutbn would be rquired to meet raeervofr adsorption

raqulrements. Sinceadeorptbn lapartialtyreverafbte,his me be an

L

verestimate. It fahoped that at leastone of the afkaUnek teats

currently bel)~ conductedat tow eurfactantfevelawill pfovfde more

Informatbnaboutthe actual magNtudaof eudacterUfoaaaa.

Sciubilfty

AnoNrerway surfactant bases may ocour in a M88rvok is by

filtratbn.8 This effectshcukf be consideredwhendsslgnlng@kalltW-

surfactanffbode. Many EOReurfecfants@ comptexmixturesthat

are sparfngly soluble in aqueous solutions. Many popular EOR

surfactantshave bw aoiutrflttiesin brines. Forrnutstbnemade wltrr

these surfactants are of,m cloudy dlsperebne, instead of tme

aolutlone. For example, the fittersbilfty of 0.1% Petroetep B-1OO

surfactarrtat 50 C was greatfyreducedwhen mixedwith a reletfvefy

high Ionk strength alkaline eotutbn. At 50C, in 0.3% NaCl (fonk

strength = 0.051), 98.lA of the aurfactantworJtdpass through a

0.45pfifter, However,whena mbrfureof 0.032NN@HP04 +0.032N

NaHC03 + 0.016NNa2C@ wtfh a pH of 10waa addedto the 0.3%

NaCl (total bnlc strength = 0.155), the fractbn of surfactant that

passedthrough the filter was reducedto 22.1%.

The effect of this behavbr k shown in Fig. 6, whkh la the

effluent analysis of a 52 C corefbod performed with the above

soiufbns in anoil-free,600 md Bereacore. Totalaurfactentratentbn

of 0.160 meqkg of corewaaqufte bw. However,the passageof the

surfactant through the core occurs in two distinct 8UffaCtantpeaks.

The secondpeakoccurred after V@ctbn of the bwer bnic strength

chaee brine w s resumed. This effect is believed to be due to

filtratbn, ratherthan tnie adaofiwbn.

This parlicufar experiment was performed in an oil-free core

with a refetivelyhigh fonk strengthalkalineeofutbn. ft isptWWth3dto

show that the eolubilnieso aurfactantsIn alkalineaohitbna need to

be considered. If oil had been present Inthe core, the mannerin

which the surfactant was propagated through the core could have

occurred differently,

~B.

Reservoir mineral, brine, and oil propettiss that are most

Important for determining the feaaibillty of alkaiine fbodhg were

prevbusfy identified from a detailed study of alkalinefield projects

conductedsince 1960.1 Some of the data publishedinthe chemical

literatureand reeuttsof Iatmratoryexperimentswere especiallyuseful

in correistbn of minerafcgyandthe albweble pH levelof the Injected

fluids. This is particularlyknpcrlantbacauaethe veIy high pH alkalis

are completely consumed by some of the minerala in petroisum

resewoks. A summaryof the ecreenlngcriteriafolbwa.

The C02 content of petroleum reservoirs la repotted only

kifrequentfy, Yet, ft is one of the moat Important parameters for

determiningwhether a reservoir is a candkfatefor alkalinefbcdlng.

Aikaiine flcwdlng ahoukf usually not be considered In reservolesof

high C02 content: molefraction of C02 (in producedgas) >0.01 or

pH c 6.5.1)14

Gypsum

The presenceof gypsum (anhydrtte)Isa deterrentto any~

of alkaline (or surfacfanf) ffoodlng. it has been shown that

l

9ypsum in a maewoir mn consume 10 PV of a We solution of

NaHCO$ Alkalinefiocding shouldbe rejectedfor any reservclrwith

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A

DESIGN AND OPTIMIZATION OF ALKALINE FLOODING FOIWJIATIONS

SPE/DOE 20238

Oreeferttran O.l%9Ypsum. Thisamount ofgypaum can bainfened

from 1000ppm sulfatebn inthe btfne.l

Kaolinfte

The presenceof kaoliniteIea seriousdeterrentto flcodtngwith

higher pH alkalis.ls Only bw pH (about8.2- 10) atkallastrcukf be

consideredfor use in reservoirsthat contain appreciableamcunteof

mollnite.

?dontrnorillonite

Montmorillonite,whkh is leasreactivewith atkalie,ladetrimental

to alkalinefboding processesbecause of tts high surface area arxl

vety highcatbn exchangecapacity. High CECvelueeare asacciated

with high montmorillontfe content. If divalenf Ions OCCUPYhe

exchange eltes, much of the injected alkali can be consumed by

adverse precipitation reactions.

The screening criterion for ion

exohangecapacity Is 5 meqkg. This corresponds rcughly with the

presenceof 1%montrncrilbnite and 0.4 wl % of diva[entbns in the

brine,1116

Limestone

High pH alkalis are reactive with l imestone and should be

avoided in dolomitic reservoirs. Low (Nai- iC03) and mcderate

(Na2C03) pH carbonates have been shown to be compatiblewith

dobmitlc cores.1718

AddJ@M&

Tne acid numberof crude oil was previouslythought to be an

important parameter for alkaline flooding processes. The

exparimentadescrfbed in the first section of this paper showedthat

oil acid numbermay not bean extremelyimpcrtarrtparameter. The

detaiiedstudyof 24 alkalinefield projectsthat was menticnedabove

failed to chow a correlation between oil acid number and project

success.

it appearsthatoil acid nuntwr is Importantfor achievingtowIn

in alkalinefbods that do not IncludeaddedsyntheticsurfacfantIn the

aikaline fbcding fonnulatbns. Even then, mechanismsother than

IFTbwering may resuttin nrobliizatbn of residualoil duringalkaline

fboding. The state-of-the-artin alkaline flooding is the combination

of bw-pH alkalis with small amountsof addedsyntheticsurfactants.

Underthcaeconditions,there is not enoughinformationto conclude

that oil acid number should be considered a criterion for alkaline

flooding,

Other parameterssuch aa temperature,penneablilty, salinity,

andoil viscosityhave thefamiliar limitsfor chemwl flooding,whose

valuea depend on the specific limitations of the surfactant and

polymer,1

Wilmington (CA), field is presented as an example of the

design and optlmlzatbn of an aikallne flood. Wilmingtonfield was

selectedbecauseit ie a large oil field that was the site of a previous

alkaline flood. An alkaline flooding prcject, which encountered

severe problemswith alkal conaumptbn and scaling,waapreviously

conductedIn the RangerZoneof the fletd.19-21

Resewoir parameters shown in Table 4 were taken from

publications by the City of Long Beach and Thums Long Beach

Company.l 9 The crude oil, furnished by Thums Long Beach

Mmpany, from Well A-52 and brine were analyzedafter deliveryto

NIPER. TherIXMmineralogyIsof sendfromWellD-4924.

Examination of the brine analysia provldee a very postiiie

hctbetbn that thle field shouldbe amenabteto alketineflooding. The

carbondbxlde cmtent shouldbeJecceptsbla,as indbatad by the pH

of 7.4. The total of 947 m f divalentbns iswetiwtthinthe ecreenlng

criterion of 0.4 wt. % (4,000 rn@t)which relatesto the dfvatemton

exchangecapacity.

Examinationof the rock mineralogyrevealsthat there am not

slgnifkent amountsof anyclays. Ontytraces of kaollnltearxf mbred-

Iayerilliie/smactiteare present. (3ypaumispresent,but onty in trace

amounts. Despfte the clean appearanceof the brfne and rock,

severe probfems were encountered with alkali consumption and

scaling durfngthe previous projectthat was conckwtedwith acdfum

ot.hosilkate.

The low-clay, low-gypsum cartent of the Wilmington sand

indkates that reactionwith alkalishouldbe smell. Yet, the published

data show that losses of orthcsilicate in the RangerZone could be

very high. Chemical consumption flow experiments showed that

after 36 days af reskfence time, losses of Otihosilkate were afmut

169msqkg of rock.21

Much of the scale formation was attributed to magnesium

silicate. The apparentsourceof magnesiumis thebrine. Laboratory

tests22 demonstrate the reaction of silicate with brine magnesium

ions, but it is not enough to account for the amount of Silicate

consumption. This, abne, suggeststhat the mineralanafyeiemaynot

be fully representative; however, plagicclase is another possible

ecurceof magnesium.

Plagicclasefeldspar is a majorcomponentin the RangerZone

sand analysis shown in Table 4. PiagloclaeeISsomewhatreactive

with alkali,15and this reaction coufd account for some of the alkali

consumptbn tn the field test.21 In laboratorymeasurementsof alkal}

transmission through Wilmington sand22there were both a fast

reaction, as if with exchange Ions, and a slow reaction, as if by

aluminosilicatedissolution. A comparisonof fast alkaliceneumptbn

for three alkalis,andfor mixtures, is given in Table 5. Ali vafueein

Table5 weredeterminedby NIPER. The value for OIthMOSte is an

order of magnttudefewerthan that reportedin Ref. 21. Among the

differences in experimental conditions is the time of residence, If

consumption had been evaluated after 36 days in these

experiments, as it was In Ref. 21, consumptbn cculd have been

higher.

The size of the alkaline slug required to satisfy the alkali

consumption capacity (ACC) of the Wilmington resewoir was

cakulated fromthe folbwlrrgr

wi ~nsumW Kg&f o~kxpmk --(1)

m

dugs ize(PV) =

alkali consumed

alkali concentration x a

...................(2)

where equivalentsfig of rock is the experimentallymeasured alkal

consumption, p is bulk rock density In kg/dr , Injected alkali

concentration b normality, and a is the fractional porosity of the

reservoir.

Cakulatbne with these equatbns were madewith the data

given in Table 5 for exparfmerrtallydetermined atkaliconsumptbn

measurementsusing Wilmingtonflefd aand. Resultsfrom sandpack

floods with carbonate mixtures and results from. ellm-tube

experiments with pure carbonates were used for calculatbns.

Resktencetime in the slimtubewas approximately1 rtwnth.

From Eqs. 1 and 2, the size of a slug of 0.095N NaHC03

neededto satisfythe ACC of the reeewcdrfa0,18 PV. (Thisb onlya

fifth of the amountof sodiumsilicatethat wouldbe requfredto satfefy

61s


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:PRAX3E 20238 Trov R. French and Thomas E. RurcW ld

8

,. _,---

-.

.

the ACC). The sizeof a 0.095N Na2C03slugis 0.51PV. The larger

value for Na2C03 reflects the increased reactivityof the Na2C03.

The sandpack flood results snow that only 0,22 PV of the 0.19N

equinormal mixture of carbonates would be needed to satisfy

consumption requirements.

This value reflects the higher

concentratbnof the solutionmorethanthe shorter residencetime In

the cores.

These results for alkali consumption are, at best, only

estimates. Theyare, however,very encouraging. It appearsthatthe

lower pH alkalis ehould propagate into the resewolr a substantial

distancebeforebeingcompletelyconsumedby rook-alkalireacfbns.

Just as important,these bwer pH alkaliswill notcausethe intractable

sillcstescalesthat w8reencounteredinthe prevbus pibt pmject.21

ebMmBsFwQmmwwl

One of the mechanismsfor mobllizatbn of residualoil is IFT

reduction, and phase behavior tests can be used to optimize the

parametersthatwillproducelowIFT. Theexperimentalpmcadurefor

performing these tests was described above and in previous

p*,51ications,2-3,7-8Sinm the

10W pl falkalissuch

as NaHC03 and

Na2C03 dc not produce the uitra-bw IFT valueaof the higher-pH

alkalis,smallamountsof syntheticeurfactantswereaddedto the alkali

to promotefurther Iowerfngof IIT. Wilmingtonoil A wasusedfor the

phase bahavbr tests.

Salinity requirementdiagrams (SRD) for two ionic surfactants

andone nonioniceurfactantwere prepsredfrom the phase behavbr

test results. Surfactantconcentratbn was usedfor the abscissain

the SRDSand NaCl concentration was used for the ordinate. All

sen@&sccrrfahwcf0.095NNaHC03 + 0.025NNa2C03(PH=9.3) or

0.19NNa2C03(PH= 10.8). Theareas indketed inthe SRDSarethe

areas where interracial activity was visually obsewed. The

experimentswereconductedat 52 C.

The salinity requirement diagram for Petrostep B-105, an

anicnlc sutfactant,is shown in Figure7. Theareas indicatedarethe

zones where interracial activity was observed. The figure shows

changes that occur as surfacfant concentration increases and pH

Increases, The additbn of sudactant to sodium cwbcnate or to

sodiumbicarbonatemixedwith sodiumcarbonatecausesthe optimai

salinityto incfeaseat anyeurfactantccncentrstbn; the optimalsalinity

of the mixedcarbonatesis higherthan theoptimalsalinityfor sodium

carbonate;the optimai salinity for mixedcarbonatesis afwayshigher

andcloserto theoptimaleaiinityof thecommercialsurfactants.Thisis

becausea lowerconcentratbn of naturaieurfactantis availabiefrom

the cnrde oii at PH9.3 than at pH 10.8. The equinormsimixtureof

NaHC03 and Na2C03 is especially interesting because of the

Interracialactivity that occurs between 2.4 and 3.8?40NaCi St O.1%

surfactant concentration,

This optimai salinity brackets the

Wilmingtonresetvcirbrinecompositionwhkh la2.7%.

Similar experiments (see Figs, 8 and9) were performedwith

Nsodcl 25-9, a nonionic alcohol ethoxylate, and AES 1215-3S,an

anbnb alcoholethoxysulfate. Increasingthe concentratbn of either

of these surfactants resulted in an Increasedoptimal sailnity. This

behavbr is moredramatk than was observedInthe PetroetepB-105

system previouslydisramsed.

Theoptimaieallnitywindowis an importantconsiderationwhen

choosing a surfactant to be used in a spscifk oil field. The AES

1215-3S eurfactantgave somewhat higher IFT in combinatbn with

mixedcarbrates and aisc hada higherthan desiredoptimalsalinity

window at 0.1%surfactanfccncentratbn than the other surfactants.

Therefore, Neodol 25-9 and Petrcstep B-105 (in combinatbn with

the mixedcarbonates)were selectedfor oii mcbiiizatlontests. The

resufts of the salinity requirement tests and IFT tests at 0.19 0

surfactsntccncentratbnare summarizedin Tebte6.

Phase behavior results were ueed to design a series of

sandpack fbods. Injected chemicais and injection strategies are

summarizedin Table 7. The potymerconcentrationwas selectedsc

that a favorablerrwbilityratiowas assured. Ths shearrateexpected

at a frontal advance rate of 1 WD (0.3 m/d) for a 32% porosity

sandpackwith 400 mdpmneability wascalculated:

T

hearrate = (266.4)(V) ~

.........................................(3)

= 7.7 sac-f

where V . frontai advance rate (ff/D), 0 = porosity (fraction) and

K =

pe~eabii~y (N).

The viscosity of Wilmingtoncrude oil A used in this study was

measuredto be 78.8 cp (0.0786Pas)at the reservoirtemperatureof

52 C. This is muchhigherviscositythanthat repottedprevbusly for

oil fromthe RangerZor119 This differenceinviscosftymaybe me

to loss of solution gas. At the calculated shear rate, 3,000 ppm

4800CXbiopolymer has a viscosity of 118cp (0.118 Pae). Since

shear rate calculations for a sandpack are at best approximate,a

pciymer bwrcentratbn of 3,000 ppm is probabiy the minimum that

assuresa favorablerncbiiityratio. me 3,000-ppm@ymer siug was

folbwed by two iower concentrationsiugfsof 45 cp (0.045Pa.e)and

9 Cp(0.008Pas)Vieccsny.

The sandpack flood tests were conducted with and without

aikaii, with and without surfacfsnt, and with and without prefiush.

Resuttsof the sandpackfioods areccmoinedwith ccnsunqNbn and

adsorptbndata in othersectionsof this paper

n

orderto remmrnend

Injecfbn strategiesthat maybe successfulin Wilmingtonfield.

The amountof incrementaloii producedduring the sandpack

floods correlateswith the interfaciai tension measurementsgiven in

Table 7. The three systems that had iFTs bebw 4 f.tN/mproduced

the mostoil. me two eystemswith IFIs above 50 fdWmproduced

the ieastoil, Alkalineficodirrgwith aikalinepreflush(Wii-3)produced

31A more oii than aikaiine fiocding without preflush. Aikailne

floodingwith 0,1% eurfactant(Wii-3)produced83% moreoifthan the

equivalent flood without surfactant (Wil-4). Aikaline flooding with

0.1% surfactant (Wii-3) produced 49% more oil then flooding with

eurtactantabne (Wii-5).

In these iimited results,aikaivsurfacfarrvpciymerASP)fbcding

mobilized more oii than aikali/pclymer (AP) fboding, and rmnbnk

surfactant was superior to anionic surfactant. ASP flooding also

mcbiiiied more oil than surfactant@ciymer(SP)fiocding conducted

at equivalent ionic strength. These oil production results correlate

withother resultsthat ahowthat alkaiiandsurfactanfworktogetherto

mcbiiizeoii.

Sandpackfbcd effiuentswere also analyzedfor IX ,,aikaiinffy,

andsiibcn. Oniybackgroundlevels (5ppm)of silken weredetected,

The absence of dissolved silicon in the effluent is encouraging

becauseif confirmsthatsiikste scaleis notbeingproduced.

Wilmingtonfield reservoirdata were used for an examplecost

calculation. Forthis example,the floodingsequenceis:

0.25 PV 0.025NNaHC03 + 0.095NNa2C03

0.25 PV 0.095NNaHC03 + 0.025NNa2C03+ 3,000ppm

bia.?olymer+ 0.1% synthetb eurfactant

0.?0 PV 2,000 ppm bbpolymsr

005 PV 1,000ppm bbpclymsr

The purpcae of the alkaline prefiush is to satisfy the alkali

consumption due to reaction with the reservoir rock and brine, to

pmtacf the bw ooncentretioneurfactantfmm precipttatbnby divatent

ions,7*s,11,21end to reduce loseof eurfacfant

by a~pfbn BSS@

on a conservative38% oil recovery,the chemicalmet for recovering

crude oil would be $3.901bbl in this example, with 78gAof that

amountbeingsfxmt for polymer.

619


6/12

.

v

------- ---- -- -

.-.

.-.r ----- . -------- - ---, --------

-. -, -v- ---.

I o. Krumrine, P. H., J. S. Falcone, Jr., and T. C. CamPf@lt

SurfactantFfcoding 1: The Effectof AtkalineAdditfveacn IFT,

1.

For a reservoir to be a candidate for alkaline flooding, the

Surfaotant Adsorption, and Recovery Efficiency, BOO.Pet.

reservoir should contain little or nc gypsum, the divalent bn

Eng. J., Aug. 1982.

exchange capacity should be feesthan S mac kg,and the In

situ pH ahoukfbe greaterthan 6.6.

11, Latrrid,J, and Bazin,B. AlkalinePreffuahIna Lcw-PermaabUt

CfayeySandstone.J. Pet. sol. Eng.,3,1989, pp. 111-120.

2. A mixture of synthetk aurfactantati bw-pH alkall produces

lower IFT and sustains fow IFT longer than either reactant

12. Peru, D. A. ad P. B. Lorenz, Surfactant-EnhancedLow PH

alone.Thlewas observedwith crudeshavingbw andhighacid

Alkaline Flooding,paper SpE 17117.

numbers.

3.

An alkaline preflush protects synthetic surfaotants from

preclpltatbn by removal of divalent krnsand reauttsin higher

incremental oil production, although sweep efficiency of

preflushaoMbns may be paw.

4. Alkali reducee the adaorptlon of surfactant; however, the

question of how much surfactant Is needed for good

prcI~I:~ through a reservoir has not been satisfactor ily

5.

A bw-pH alkali (euchas NaHC03 or NaHC03 \ Na2C03) In

ccm alnatlonwith synthetic surfactant should b~ effective for

producing incremental oil In the Ranger Zone of the

Wilmingtonfield,whichwas givenae an exar@a.

The authorswish to thank Dr. PhilipB. Lorenzfor his work on

definingthe screeningcriteria thatwere

described

n this paper. The

authorsalSCwlahto thankKerr.McGeeChemicalCorpcratbnandthe

U.S. Departmentof Energyfor sponeortngthework,

1

Lorenz, P, B. and D. A. Peru. Guidelines Help Select

Reservoirsfor NaHC03 EOR,Oil and Gss J. Sept. 11,1989,

pp. 53-57.

2.

Nelson, R. C., J. B. Lawson, D, R. Thigpen, and G. L.

Stegemeier. Cosurfactant-EnhancedAlkaline Flooding,

f s.

at Fourth Joint SPE/DOE Symposium on Enhanced Oil

~~~2ery, Tulsa, OK, Apr. 16-18, 1964, SPEIDOE Paper

.

3. Wasan, D, T,,

Enhanced Oil Recovery Through In Situ

Generateed Surfaotants Augmented by Chemical Injection,

Illlnois Instituteof Technobgy Annual Report1989.

13. Hurd, B. G,, Adsorption and Transportof CfWMbSlS@cfesIn

Latwratory Surfactant Waterfbodlng Exparfments, Pres. a

SPE Improved011Recovery

Symposium,

ube, OK, Mar.22

24, 1976, SPE paper 5818.

14. Coll ins, A. G., Geochemistry of Oitiiekf waters, Elaevle

Scientifk PublishingCO.,1975.

15. Thornton, S. L., Reaotbn of Sodium Hydroxidewith Silicate

Minerals,U.S. Dept.of EnergyReportNo.NIPER-128,N-11

Order No. BE86000275,Apr. 1986.

18, Smith, F, W., lon.Exchange Ckmdifbnintl of Sandstonesfo

Chemkal Flooding, J. Pet. Tech., v. 30, June 1976, p. 959

968.

17. Burk, J. H,, Comparison of Sodium Carbonate, Sodium

Hydroxkfe, and Scdlum 0rth0611kSt0or EOR, SPE Reservo

Eng., v.2, No. f, Feb. 1987.PP.9-1$.

18. Cheng,K, H. Chembal Consumptbn DuringAlkalineFfcodln

A Comparative Evaluation, Pras. at Fiftfr Joint SPE/DO

Symposium on Enhanced oil Recovery, Tuba, OK* Apr. 20

23, 1986, SPEIDOE paper 14944.

19. Gro$akurth, D. E., Cauatic Waterflcoding Demonstratio

Project,Ranger Zone Lon9 Beach Unfft ~lmin9ton Fiefd

California,Annual report,October197wuns 1977,U.S. Dep

of EnergyReportNo. SAN/1385-l.

20. Mayer,E. H.andV. S. Breit,AlkalineFfcodPredbtbn Studie

Ranger w pilot, Wilmington FieMt cal~omla, p~a. at Thir

Joint SPf3DOESympostumon EnharwedCMRecsvery,Tuls

OK, Apr. 4-7,1982, SPE/DOEpaper No. 10720.

21, DaubanP.L., R.A. Eaaterty,and M.M. WesfemtAn Eva~@n

of the Alkaline Waterllooding DemonstrationProject, Rang

ZoneWilmingtonFfetd,Ca[tfomia,US. De@,of EnergyRepo

No. DOE/BC/10830-51,May 1887.

4.

Rosen, M. J, and H. A. Goldsmith. Systematic Analysis of

Surface Active Agents. Wiley4nterscienoa,N. Y., 1972, pp.

22, Thornton, S. D. and P. B. Lorenz, Mineral-Alkali Reactbn

423.424.

Under Dynamk Conditima. U.S. Dept.of Energy ReportN

NIPER-340, Aug.1988.

5.

Hofman, Y. L. and H. P. Agnstadt, Analysisof EnhancedOil

Recovery Formulations. Chmmatographia, v. 24, 1987, pp.

666-879.

6. Peru, D. A. , Aqueous Flooding Methoda for Terliary Oil

Recovery,U.S. Patent4,817,7f5, Apr. 1989.

7.

French,T. R., D.A. Peru, and S, D,Thornton,Low

r

Alkaline

Chemical Formulations, U. S. Dept. of Energy e~rt No.

NIPER-375,Oct. 1956.

8. French, T. R. ,Deslgn and Optlmizatlon of Phoaphate-

Containlrrg Alkaline Flooding Formulations, U. S. Dept. of

EnergyFteporlNo. NIPER-446,Sept. 1989.

9.

Clark,S. R.,L M. Pitts,andS. M. Smfth,DaetgnandApplkatbn

of an Atkallne-Surlactant-PolymerRecovery System to West

Kiehl Field, Pres. at SPE RookyMountain Ragbnal Meeting,

May 1688,SPE paper No.17538.


7/12

TABLE 1.- Ctude

Oik

SPE 38

oil

Gravity,0APl

Totalaoidrwmber,mg KOH/g

Deiaware-Chikier

33.0

0.13

Wiknlngton011A 12.9 3.40

Wilmington011B

18.0

1.59

TABLE2,- Injaofbn of 0.1% PetroafepB-1OOeurfaotantIntounfiredBereacores

Chemical Permeability,

Chemioal

Chemical

Frontal

ini

fLCt8s ~-

Temp., advadoe vo:~,

Coreflood C

pH Inittal

Final Alkali Surfactant Alkali Surfactant

1 23

0.47

1.05 10.17 508 331

21.89 0.301

1.91 0.198

2

52

0.59

1.40 10.17

502 400

28.57 0.477

1.31 0.186

3

52 0.55

1.31 6.3

554 435 0

0.408 -

0.375

1Per kgof rook.

TABLE3.- Sutfactantadsorption

meq. adsorbecfl

Alkali

Sandstone

Surfaotant

Experiment

kg sandstone

.0325NNa2HP04

.0162NNa2C03+

.032NNaHC03

(0S% NaCl)

,0325NNa2HP04+

.0162NNa2Cm +

,032NNaHC03

(0.3%NaCl)

0.28NNaHC03

(1.48%NaCl)

0.14NNaHC03+

0,14NNa2C03

(1.26%NaCl)

0.085NNaHCOa

(2.4%NaCl)

0.067NNa2C03

(2.4%NaCl)

crushed

Berea

Berea

Wiimingm

sand

Wilmington

eand

Wiiminf$on

aand

Petroatep B-1OO

Petroatep B-1OO

Petrostep B-105

Petroatep B-105

Naodol 25-3S

Naodol 25-3S

Batch

0.834

Coreflood

0.198

Batch

2.18

2.26

slimtube(40 ft)

0.869

Slimtube(40ff)

0.622

sand

621


8/12

TAELE4.- WilmingtonRangerZonefletddata

OUA

spaoifiogravity@ 60~OF

0.9796

12.92

APIgravity,de9rees

KinernatioVISOOSW 1250F,*

413.0

Totaladd nutir, rn@gm

3,40

Nitrogen(ohemiluminescem), wt %

0.64

Carton, wt %

76.44

Hydrogen,WI%

10.84

Brine

Totaldissolvedsolids,mgA

26,600

Magnesium,IWL

322

Calcium,rr@

625

pH

7.4

Rookmineralogy,FO *ML 4660.8to 46*4 n

Quartz,%

74

Feldepar,% 23

Gypsum,%

trc

Kaolinite,%

trc

3

illite/mioe,%

Mixed-layerilliieMneotiie,%

tro

Plagioolesefetdepar,L

18

FektsparK,%

5

Resewoirparameters

Temperature,C

Permeabilii, rnd

Gross zonethickness,ft

Net zonethickness,ft

52

100 to 3,000

850

320

TABLE5.- Wilmingtonfieldsandalkaliconsumption

(oilpresent)

ReSdence

time,

Experiment

pH

meqlkg

days

Slimtube 1 0.087N NaHC03

Slimtube 2

0.067N Na2CQj

Slimtube 3

0.065N Ne4Si04

8.24

3.1

30

10.79 6.4 30

11.72

16.0

30

SandpaokWil 1

0.095N NaHC03+ 0.095N Na2C03

9.3

5.3

.8

SandpaokWil2

0.095N NaHC03+ 0.095N Na2C03

9.3

6.3

.8

Sandpackwit 3

0.095N NaHC03+ 0.095N Na2C03

9,3

10.9

.8

Sariip20k Wil4

0.095N NaHC03+ 0.095N Na2C03

9.3

4.9

.6


9/12

.

,.

SPE 20238

TASLE6.-

ReeukefSSHMY~lremti teeflngt

0.1%eurfeofentoncenfmfbn

~

~

Neodol Neodol Petmetep

22-9 5103 12.15-3s 229

S-102 12-15-3S

N-+ Na~ 3.0-3.S

2.4-3.s

3.0.4.1

2.9 3


10/12

SPE20258 -

NO2URFACTANT

4000

o o.1%PETROWEP3-100

E 3000-

g

g ~~ .

1000

1

9

0

200

400

600

800

TIME,

mln

Ffguro3.. TmnsfontIn ofDe12wereChlldoreil,PH9.S

0~400

o

TIME, Mln

Flguro4.- TmnslmtIFTof fwf2vmre-Chll*m

011md 0.1%P2tfoM@Ps-

lm Anionicsurwent

Preflueh3% Naci

o

0.5

1

1.5

2

2.5

3

PORE VOLUMES OF INJECTED FLUID

Ftgure 5.w

SodiumSlowbonetees

mflueh Addftfvo

634


11/12

S= 20238

ooc

E

1 2345678 9

Pore volume,

PV

Figure6.- SutiaotantTransportnan Oil-FreeBoraaCore

-i}

[

1

I

I

I

I

o

0.2

0.4

0.6 0.6

1.0

PETROSTEP B-lo5, wt. %

Flgura7.-ScMtyrequirmentdla ramforananlonloau~actantand

w:hrmaarbonats(PH1 .8)or

mixtureofsodiumcarboneto

r@aodlumbloerborwt.(PH9.3)

5%

C.


12/12

I

I

I I

I

I

I

o 0.5

1,0

1.5

2.0

2.5

3.0

AES 1215-2SCONCENTRATION,wt %

Ffgurs8.- SaWty mqufrsrwntdlsgmmfor

n

n on surfaotsntand

sodium

oarbonstoPH10.8)ors mlxtumofsodiumoarbonsto

[email protected])at W C.

12

1

aQ

2

0.5

1.0 1.5

2.0

2.5

3.0

NE,...>OI.25-9 CONCENTRATION. wt %

Ffgure9.- Ssllrrftyqu&nantdl agrsmfor a nonlonlesurfastsntand

sodium osr nsts (@f 10.8)

ors mfxturs

of sodiumcarbonata

andsodiumWuhonsts ( f 9.s)ats% C.

design and optimization alkaline

Documents