~of~~ofA~E

SPE 11780

Adsorption of Sulfonate on Kaolinite and Alumina in thePresence of Gypsumby P. Somasundaran,* K.P. Ananthapadmanabhan,* and K.V. Viswanathan,Columbia U.

. Members SPE.AIME

~-

Copyright 1983 Society of Petroleum Engineers

This paper was P'e8ented a!1IIe InternaiKlnal Symposium on Oilfield and Geolhermal Chemistry held in DerIY8r, CO.. June 1-3, 1983. The ma1erial issIAIject 10 COffection by llleau!hOf. Permission 10 copy is resIrK:ted 10 an absttac1 of not mote lhan 3OOWOfds. Wrh SPE, 6200 North Central Ex-~, 0- 64706, Dallas, Texas ~ USA. Telex 730989 SPEDAL.

ABSTRACT composi tion of the reservoir rock, since rocks inaddition to kaolinite and quartz do contain various

~ss of surfactants by adsorption and precipita- sparingly soluble minerals that are much DM>re activetion that can occur during enhanced oil recovery by in interacting with surfactants. Behavior of systemsmicellar flooding is a complex phenomenon dependent containing minerals such as limestone and gypsum cannot only on solution properties such as pH and salinity, be markedly different fram that of kaolinite/sulfonatebut also on the presence of even minor mineral con- or alumina/sulfonate. For example, earlier work withstituents such as gypsum and limestone. In this paper, limestone h~s shown the depletion of sulfonate uponthe results on adsorption of isamerically pure decyl- contact with it to be much more severe than in other)enzenesulfonate on gypS\DII, kaolinite and alumina are systems tested under similar conditions (6). Two

~resented: Sulfonate abstraction by kaolinite and major phenomena to be considered in these systems duealumina in the presence of trace amounts of gypsum to the presence of dissolved inorganics are the sul-is also determined. fonate precipitation and activation of inert minerals

such as quartz for adsorption. Since these phenomenacan playa governing role in determining the totalsurfactant loss upon contact with rock, it becomesimportant to understand the adsorption propertiesof Ddnerals and mineral mixtures that can cause severeproblems. In this study the adsorption behavior ofkaolinite and al1DDina systems containing gypsum isexaminei as a function of relevant variables. Sinceprecipitation of sulfonate by the dissolved gypsumspecies appears to be the major phenC8lenon controllingthe system behavior, a detailed thermodynamic analysisof the solubility and stability of gypsum and precip-itatior. of sulfonate is also included.

Adsorption of sulfonates varied significantlyfrom mineral to mineral. Gypsum exhibi ted a sharpincrease in adsorption above 4-6x 10-5 kmol/m3 ofresidual sulfonate. Tests using the supernatant ofgypsum showed sulfonate precipitation by the dissolvedmineral species to be a major factor responsible for ttIEhigh uptake.

A therD>dynamic analysis of the solubility andstability characteristics of qypsum and anhydrite ispresented. The sharp rise in abstraction has beenshown to correspond to the onset of sulfonate pre-cipitation. Presence of trace amounts of qypsumeither with alumina or kaolinite is found to markedlyincrease the sulfonate uptake by these minerals. It isshown that in kaolinite-qypsum and alumina-gypsummixtures, the total abstraction at high sulfonatelevels is due to adsorption on alumina and kaoliniteand precipitation caused by qypsum.

MATERIALS AND METHODS

Kaol~ite

Hamoionic Na-kaolinite prepared from well crystal-lized kaolinite samples purchased from the clay reposi-tory at the University of Missouri was used foradsorption tests. The procedure used for the prepara-tion and characterization of homoionic Na-kaolinitehas been described elsewhere (7). B.E.T. surfacearea of thj,s kaolinite sample was 9.0 11\2/1].

INTROOOCl'ION

Alumina

Alumina used was a Linde (A) high plrity samplepurchased from Union Carbide Corporation. B.E.T.surface area of this sample was deterDlined to be 15

m2/g.

Loss of surfactants by adsorption in tertiaryoil recovery systems is a complex process governed bya number of interacting phenomena due to the multi-component nature of the surfactants and the reservoirf'luids as well as the heterogeneous nature of the

:ervoir rock. Past studies have shown the sulfonate.~sorption to be strongly influenced by various system

parameters such as pH, ionic strength, temperature,

inorqwc~ type, and ~urfactant ~~ition and type(1-8). Surfactant adsorption or loss can be expectedto be influenced markedly also by the mineralogical

97

ca.

~

98

88nta1 conditions (AG~98- 1.135 kcal/mo1e. AGo1.057 kcal/mo1e). ~48

behavior of gypsum is conducted here and the precipi-tation behavior of sulfonate in Ca solutions is e~-mined.

Even though, anhydrite is the stable phase at7SoC, to our knowledge information on the kineticsof this reaction, particularly in aqueous solutions,is not available. Thus, while calciua sulfateunder reservoir conditions may be present as anhydrite,the exact nature of the solid under our adsorptiontest conditions is in question. Therefore, theactivity of bivalent calcium in equilibrium withthe solid phase is estimated for both gypsUII and an-hydrite. The chemical equilibria involved in thedissolution process are:

~um Solubility and Su!fonate Precip!tation

Gypsum <ca5°4' 2B~O) in aqueous solution canundergo a number of d~ssolution reactions. Inaddition, it can also exist as anhydrite (ca5°4) orhemihydrite (Caso4' ~20) depending upon the t-pera-ture and other solution conditions. '1t1e extent ofdissolution would indeed depend upon the stable solidphase. '111e therlROdynamically stable solid phaseunder the experimental conditions can be determinedin th~ following manner. ~+

+Caso4.2H20 (s) (5)ca.CaS°4-2H20 (s} t ~. (a) + 282° (1,)

2++...CaSO (-14 Ca (6)

2-SO4

+:: H504

+ H {11

:; (8)HSO4 + H

+Caso4,2H20 (s) ... caso4'laHiO (s) + 3/2 H2O (2)

The free energy changes involved in the abovereacUons can be readily calculated using the availa-ble data at room temperature (13,14), For othertemperatures, free energy values can be calculatedusing the equation (15 ),

ca2+ ....+ CIJ (9)

H2SO4

Caoo +

(3) 2+ ...+"-

casO4(aq)

+ -H + OR

(10)

::; Ii];)802where,AG~ ' AG~ = Free energy change at the reference

temperature, 8(298.1SoK) and at T

AS~ = Entropy dhange involved in the reactionat the reference temperature 9

A~ I'l' - ACop& p'l'

- A~~

Using the above equilibria and the stoichiometricrestriction that the total dissolved calcium is equalto the total dissolved sulfate, the activity of variousspeci~s can be estimated. Preliminary calculationsshowed that the major species in the pH range of4 to 9 are Ca2+, soi- and Cas°4 (aq). Activity ofCa2+ in equilibrium with anhydrite and gypSUID aregiven in Table 3. As expected frCD t1-.e phase stabilityconsiderations, the activity of Ca2+ in equilbriuawith gypsum is higher than that with anhydrite.

4c? T = ~ange in heat capacity at temperatureP T and under constant pressure

conditions.

Lack of thermodynamic data for CaSO4(aq) makes itdifficult tP estimate the total solubility from thermo-dynamic considerations. The solubility of gypsumunder the test conditions was therefore determined~rimentally and the results are qiven in Table 4.

T = Absolute Temperature

In order to understand the precipitation behaviorof ~lfo~te in the pres~n~ of gypsum, in addition toCa2 ac~vity, the solub~l~ty prOduct of Ca(DBS)2 alsoneeds to be determined. '!his was done bY contactingsulfonate solutions of different concentrations with5 x 10-4 kmol/m3 CaC12 in 10-1 kmolfm3 HaCl. Resultsgiven in Figure 6 shows that the onset of precipitationis at 2.8-3 x 10-4 kmol/1R3 sulfonate. The solubilityprOduct of Ca(DBS)2 was calculated using this data'and y, the activity coefficient, obtained using theDavies equation:

G~ and s~ values are available in the literature(13, l~ . 6c;T was estimated using the equation (15

ACOpT

. ~~"2 ~fr1 1z, (4)

2 [ Ix logyi - AiZi 1=i7i"" O.2tl~

where Y i is the stoiChiometric coefficient of species. i' and Zi is the absolute value of the Charge

(Y. is the positive for products and negative forreActants), 111e relevant thermod~amic constants usedin the calculation are given in Table 2. 'rt1e freemergy change involved in reaction (1), given in

Figure 5 shows that t.Go becomes negative at about46°C, indicating that anhydrite is the stable phaseabove this temperature, Similar calculations madefor the hemihydrite suggests that the formation ofCaso4' ~ HiO will not take place under the experi-

where Ai = 0.568 at 750C a~d I is ~e ionic strengthttle value of K obtained J.S 7-8xlO 12 Ckmol/m3) 3.

sp

99

4

major contribution to abstr~ction is only from pre-cipitation. Possible particle/particle interactionsdue to the overlap of electrical double layers andattractive van Der Waals forces can also influencethe adsorption behavior at high solids concentrationIn any case, extrapolation of the curves in Fiqure 7to obtain the value of AC due to precipitation alonewill be justified only when the reasons for thecomplex behavior of the system are fully establi-shed.

Estimation of Su1£onateLoss in Mixed Miner,!;l Systems

As mentioned earlier, addition of l' gypsum toalumina and kaolinite resulted in hiqher sulfonateuptake under D)st conditions. 'nle total dissolvedCa in qyps\DD + alumina arid qyps\S + kaolinite systemsare given in Table 4. Precipitation of Ca(DBS)2 areexpected in alumina and kaolinite syste8s at 1.1 x ]0-and 7.lx 10-5 kJlK>l/.3 sulfonate respectively. Thesharp rise in abstraction in gypsum + kaolinite systemrGK,does occur at 7-8x 10-5 kmol;.3 of sulfonate.In fact it is possible to predict values of abstractionabove this concentration, assuminq that

o:.~ted results show that while anhydrite will causeprecipitation around 6 - 6.4 x 10-5 k801/m3

sulfonate, qyp8um will cause precipitation around5.2 - 5.5 x 10-5 Jaaol/m3. ~e sharP rise in ~e

abstraction isotherm is around 4-6xlO-s kmol/msulfonate. ~e scatter in the data makes it diffi-cult to determine the Ca controlling phase.

Activity of Ca2+ in equilibrium with the solidphase should be constant as long as the solid ispresent and is in equilibrium with the solution.Under this condition, irrespective of the amount ofinitial sul£onate level, the residual sulfonateconcentration should remain at a value dictated by

equation 12. ~is will result in a vertical ab-straction line. ExaDlination of Fiquz;e 2 suggests thatthe abstraction line is only nearly vertical and thatthe residual sulfonate does increase in the testedrange. It should be noted that the therlDOdynamiccriterion.requires. the ~olid ~~ dissolve continuouslyto replenJ.sh solut1.on W1.th Ca that is beingdepleted by the sulfonate. ~e increase in sulfonatein the precipitation region suggests that the solidis not in total equilibrium with the solution. Itis possible that the dissolution kinetics is affectedby the adsorbed/preclpi tated sulfonate on the solid.

rGK = rK + rp

where r is the contributions from precipitation toabstrac~on. rp can be calculated using the valuesfor initial Ca, residual sulfonate and the solUbilityproduct. 'rt1ese results given in Table 5 show that thepredicted values of abstraction are in fair agreementwi th the experimental resul ts. Similar predictionsfor gypsum + alumina system above 1..1 x 10-4 kmol/m3sulfonate, given in Table 6 also are in agre_entwith the experimental values obtained for abstraction.Evidently, the sulfonate loss at high sulfonatelevels is due to both precipitation and adsorption on

1taolinite/allDBina.

At low sulfonate levels, presence of gypsum en-hanced the abstraction in the case of alumina anddecreased i~ in the case of kaolinite. Under theexperimenta;l conditions alumina and the edge surfaceof kaolinite are expected to be weakly positivelycharged. While the decrease in abstraction in thepresence of kaolinite system could be due tocaapetition between sulfonate and dissolved sulfate,such effects are not evident in the alumina system.A detailed study of the charge characteristics of theminerals and the uptake of Ca and SO4 by the mineralsalong wi th that of sulfonate may help to understandthe behavior of this system.

Precipitation behavior of gypsum supernatantprepared by contactin9 the mineral with 2 x 10-1kD>1/a3 MaCl was tested as follows. 5 ml of the supernatant was mixed with equal volume of sulfonatesolutions of different concentrations. ~ain,predictions of precipitation at 7.7 x 10- (9YPsum)and 8.8 x 10-5 (anhydrite) are in agreement with theresults in FitJUre 2.

In general, it is difficult to isolate adsorptionfraa precipitation. Dtimation of the precipitationfrca supernatant tests can be l~er than the actualprecipitation in abstraction tests, since in theformer solid is not present to replenish thesolution continuously with calcium that is beingdepleted by precipitation. Since adsorption is asurface area dependent phen~non, one llethod toisolate precipitation from adsorption is by conducting Itests as a function of solid to liquid ratio. Olangein sulfonate concentration in the bulk can be expressedas:

OONCLOSIOHS

AC = r s + P

where r is the adsorption density in ~l/g and Sis the solid to liquid ratio in kg/.. ttlus, theslope of 6C vs. 5 curve at constant equilibrium con-centration should yield r. However, if precipitationoccurs also on the mineral surface, then isolation of! fr08 r could be difficult. .

1. Sulfonate adsorption/abstraction by re~rvoirrock minerals is affected markedly by the type ofmineral component present. AlUlaina and kaoliniteexhibit characteristic adsorption isotherms with aplateau region. In contrast to this. gypsum exhibitsan almos~ vertical rise in abstraction above certain

sulfonate level.Results of ~C vs. S at two levels of residualsulfonate are 9iven in Figure 7. Interestingly,

these plots exhibit a negative Slope above solidsconcentration 150 kg/m3. The reasons for thisbehavior is not clear at present. It is possiblethat gypsum absorbs water preferentially and the

2. Tests using the supernatant of gypsum showedprecipi tation to be a major phenomenon contributingto the sulfonate loss.

100

3. The thermodynamically stable solid calcium0sulfate phase at 75 C is anhydrite. Activity of

Ca2+ in equilibrium with anhydrite and metastabl~gypsum has been esti_ted.

4. Dick, S.G., Fuerstenau, D.W. and Healy, T.W.,"Adsorption of Alkylbenzenesulfonate Surfactantsat the Alumin~-Water Interface", J. 0011. InterfaceSci., 37(3), (1971), 595.

4. The sharp rise in abstraction in the case of9YP5~ has been correlated to the onset of Ca (CBS) 2precipitation.

sa.asundaran, P., and Fuerstenau, D.W., "The Heatand Entropy of Adsorption of long Ctlain Surfactantson Alumina in Aqueous Solutions", Trans. AIME,252 (1972)275.

5. The solubility pr~~ct of Ca (DDS) 2 has beendeterDlined to be 7.5 x 10- (kIDO1/m3) 3. Somasundaran, P. and Hanna, B.S. "Physicochemical

Aspects of Adsorption at Solid-Liquid Interface",Parts I & II, IJaproved Oil Recovery by sur!actant~~ Pol~~!: Flooding, Eds. D.O. Shah and a.s.Schechter, Acadeudc Press, (1977) 205-274

6. Addition of l' gypsum to alumina is f~nd toincrease the sulfonate uptake. In the case of kao-linite, such addition of gypsum caused a llarkedincrease in abstraction above7-8xIo-S kmol/.3 sul-fonate. 7. SODIasundaran, P. and Hanna, H.S., "Adsorption of

Sulfonates on Reservoir Rocks", SPE J.,l9(l979)22l7. In mixed mineral systems, at high sulfonate

levels the experimental abstraction is found to bethe sum of adsorption on the major component andprecipitation caused by gypsum.

8. Scamehorn, J.F., Schechter, R.S. and Wade, W.H.,"Adsorption of Surfactants on Mineral Oxide Sur-faces fr~ Aqueous Solutions", J. Coli. InterfaceSci., 85 (2), (1982),463.

8. A method to estimate adsorption and prec;L:pi~tion in abstraction systems is su9gested. 9 Somasundaran, P. "Adsorption from Flooding

Solutions in Porous Media", Ann. Report to DOE,NSF and a Consortium of Supporting Industrialorqanizations, Columbia Univ. 1980.

~LEOOE2(EN'rS

10. Reid, V.W., Lon9JRan, G.F. and Reinerth, E.,-Determination of Anionic-Active Detergents byTwo Phase Titration., Tenside, 4(9), (1967), 292.

The authors gratefully acknowledge the supportof the Department of Energy, the National ScienceFoundation (CPE-82-0l2l6), Imoco Production Co.,Olevron Oil Field Research Co., Exxon Research andEngineering, Gulf Research and Development, Marathon,Shell DevelolUent, Standard Oil Co. of CIlio, Texaco,and Union Oil Company of Ohio.

11. Tamamushi, B. and Tamaki, K., "Adsorption of ~9Chain Electrolytes at the Solid-Liquid Interface",Proc. 2nd. Int. Q)nq. Surface ActivitY III,Butte~rth, London, 1957.REFr;RENCES

;I.: Somasundaran, P. and Fuerstenau, D.W., "Mechan-isms of Alkyl Sulfonate Adsorption at theAlumina-Water Interface", J. Phys. Chem.,70, (1966) 90.

12. oelik, M., Goyal, A., Manev, E. and Somasundaran,P., -The Role of Surfactant Precipitation andkedissolution in the Adsorption of Sulfonate onMinerals", SPE paper 8263, (1979).

2:. Somasundaran, P., Healy, T.W. and Fuerstenau,D. W., "Surfactant Adsorption at the Solid-LiquidInterface--Dependence of Mechanism on O1ainLength", J. Phys. O1em., 68, (1964),3562.

13. Garrels, R.M. and Christ, C.C., Solutions,Minerals and Equilibria, Freeman, COOper & CO.,California, 1965.

14. Stumm ,W. and Morgan, J.J., hluatic Olel8istry, 2ndEd., John Wiley & Sons, N.Y., 1981.3. Wakamatsu, T. and Fuerstenau, C.W., "The Effect

of Itjdrocarbon Clain Length on the Msorptionof Su1fonates at the Solid-Water Interface", AdvanClem. Ser., 79 (1968)161.

15. Duby, P.F., "Graphical Representation of f)Iuili-bria in Aqueous Systems at High Temperatures",High Temperature, High Pressure Electrochemistryin Aqueous Solutions, Eds. Staehle, R.W., JonesD. de. G. and Slater, J.E., National Assoc.of COrrosion Engineers, 1976.

101

'r8ble 1

EXPBRIMENTAL ~I'fI~ FOR ADSORPTION9F ALKYLBEllZDlBSUUOIIATES*

T-.'eratur. 7SoCMaCl 10-1 ~l/aJ

AllainAGyPS"

1.. h

4 h

2h

72 h Gyps-(--HI

10 89 in10 al of8aCJ.

Al~...+10 89 --in 10 al ..Cl

xaol1nJ.te +20 89 9YPS-1ft 20 al ..Cl

..

50 kg/-

1 b

75 t 2oC

4500 'P8

10-1 _11.:

-33.9 z 10

PreoonditJ.oninq ~

0In4i tJ.o..inq 'li8ewith SUlfonate

Soli& Ooncentratio..

Cantri~tion ~

~rature

~ntrifu9ation Speed

Ionic Strength

200 kg/83

1b

75 :t 2°C

4500 r(8

10-1 _l/a3

1.8.10-3

~l. 2'r8bl. 5

FREE aEa;y CW FORMAfiOW AaaI BBt'IIDP'l CW GYPSUM.~RITE AKI amA.moS~-AT 25uc .

BXPBRIMEftAL vs. CAImLA'rZD ABSTRACTION~ GYPSUM +~LIMrrB SY-

'ft)Ul dis..lved calci- ~ 7.8 x 10-3k801/a3

C41culaUd Abstracti- - rGK -rK + rp

~ - ~ ,Residual z.pert-tAl CA1C1ilAtedSuUODA!- AbstrACUoo _tractioo

k80l/a- _1/0 _lIS

1 x 10-4 6 x 10-6 3.9 x 10-5

-4 -5 -5,.5xlO 3.5xl0 6.5x~0

-4 -5-52xlO 6xl0 7.5xl0

-4 -5 -53 & lO 9 x 10 8.3 & lO-

Wkcal/8D1

-429.19

-315.56

-132.18

-171.55

-214.22

-312.67

-177.34

-179.94

.177.94

-56.69

-37.595

SOC&Va..,.l-l

46.36

25.50

-13.20

1&..

4.1

16.716

-2.519

c.BO4o2B20

CASO4

~2+

~+

~«8)2(.)

CaSO4 (aq)

802-4

aq-C

~4

H2O

(8-

-ta frC8 ~ (13)

~l. 6Table 3

ACTIVITr CW Ca 2+~~LIBRtUM wxm ARBYDRXTEAJro GYPSUM AT 75uc :

BXPBRIMEH'rAL VB. CALCULATED ABS'l'RAC'fi<MIN AUlMrMA .. GYPSIM Sysi;D(-

-3 31"U1 di8so1ged ca1ci- - 3.9 x 10 _1/8

calculated Abstraction e rAG . r A .. rp

~_1 Exper18e.,~ Ca1cnlatedSUUooa~ -traction _traction

-1/8- _1/0 _1/"

-4 -5 -52 x 10 3.4 x 10 6.5 x 10

-4 -5 -53 x 10 7.5 x 10 9.3 x 10

-4 -4 -45 x 10 1.2 x 10 1.2 x 10

, .10,-4 1.2 x 10-4 1.3 x 10-4-

START 06.Z6.29.4j,- ~

-0e

z0i=

'JA:

tornID

ct

lo-s,Z

~-':Irn

9.91

~

STOP

fig. 1-An8IyIicaI ~~8m 01 ~.

0

'0E

w~octI-Q.=-

W

~Z010-oJ=-cn

0-..."0e

z0-=~~",m4...

i0...-'~",

0.3

0.2

01

- 00e...au.. "OJ.04

.0..2

-0.3

.0.4

1.0

0.8

0.... , - I I

K KU U

0.4

0.2

~10-8 ~. 10-8TOTAL SULFONATE CONCENTRATION, kmol/m8

,-"I ~--'CoOz-