Microemulsions as a Possible Tool for Tertiary Oil Recovery

4 Microemulsions as a Possible Tool for Tertiary O i l

Downloaded by UNIV LAVAL on July 11, 2016 | http://pubs.acs.org Publication Date: January 26, 1979 | doi: 10.1021/bk-1979-0090.ch004

Recovery JACQUES E. DESNOYERS, REJEAN BEAUDOIN, and GERALD PERRON Department of Chemistry, Université de Sherbrooke, Sherbrooke, Quebec, Canada J1K 2R1 GENEVIEVE ROUX Laboratoire de Thermodynamique et Cinétique Chimique, U.E.R. Sciences, B.P. 45, 63170 Aubière, France The primary o i l recovery takes advantage of the pressure exerted by the natural gases which forces the o i l through the wells. When this pressure drops, i t can be built-up again by water flooding. Unfortunately, after these primary and secondary processes, there s t i l l remains up to 70% of the o i l adsorbed on the porous clays. Consequently, in recent years, there have been tremendous efforts made to develop tertiary o i l recovery processes, namely carbon dioxide injection, steam flooding, surfactant flooding and the use of microemulsions. In this latter technique, illustrated in Fig. 1, the aim is to dissolve the o i l into the microemulsion, then to displace this slug with a polymer solution, used for mobility control, and finally to recover the o i l by water injection (1). Nature of Microemulsions. Microemulsions are rather complex mixtures of water, o i l , surfactant, cosurfactant, usually alcohols, and often other additives such as electrolytes which, when added in the right proportions, form spontaneously a transparent or translucid liquid. One of the most important features of these microemulsions is the large quantity of o i l that can be dissolved or dispersed in i t . It is primarily for this reason that they are used to such a large extent commercially as water soluble waxes, cutting oils, wetting agents, herbicides and pesticides, synthetic blood, etc. (2). Despite the obvious importance of these systems, with the notable exception of Schulman et al. (3), few fundamental studies have been made until fairly recently. S t i l l now strong disagreement exists amongst authors on the origin of the stability and on the structure of microemulsions. Following the original suggestions of Schulman, many consider microemulsions as a special case of emulsions where the small size of the droplets comes from the formation of a mixed film having a near zero or negative interfacial tension (3). Others, following the school of Friberg (4), prefer to consider the microemulsion as a swollen or inverse micelle. Their evidence comes mainly from very systematic studies of phase diagrams which indicate that the microemulsions are in fact extensions of the normal micelThis chapter not subject to U.S. Copyright. Published 1979 American Chemical Society. Tomlinson et al.; Chemistry for Energy ACS Symposium Series; American Chemical Society: Washington, DC, 1979.

CHEMISTRY

INJECTION WELL

FOR ENERGY

PRODUCTION WELL

STABILIZED OIL BANK


MICROEMULSION SLUG (Polymer Solution)

Academic Press Figure

1.

Oil extraction

by using microemulsions

(I)

THE THREE STRUCTUREFORMING ELEMENTS SHOW AN AREA WITH ION PAIRS AND INVERSE MICELLES

c

6

c

2

A PLANE AT CONSTANT CONTENT (50X)

C OH

^«,* •χ

1

Β

uF P-XYLENE IS SUITABLE TO SHOW THE

%*C

5

W/O MICROEMULSION AREA DEPENDENCE

5

ON THE RATIO BETWEEN THE THREE STRUCTURE-FORMING

.1

¥J

C

ELEMENTS

/

1 2 ° 4 / C OH* 50% C C S

q

6

2

THE W/O MICROEMULSIONS CONTAIΝI SOI HYDROCARBON ARE A DIRECT CONTINUATION OF THE INVERSE MICELLAR AREA AT OX HYDROCARBON AND THE THREE

STRUCTURE-FORMING

ELEMENTS FOR THE AREA ARE SIMILAR

C SÔ4 12

•507.C C 6

2

*507.

c

6

C

2

Academic Press Figure

2.

Phase

diagram

of a water-pentanol-sodium microemulsion (4)

dodecylsulfate-^-xylene

Tomlinson et al.; Chemistry for Energy ACS Symposium Series; American Chemical Society: Washington, DC, 1979.

4.

DESNOYERS ET A L .

Microemulsions

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Oil

Recovery

35

l a r p h a s e , a s shown i n F i g . 2. As i s o f t e n t h e c a s e , we h a v e become i n v o l v e d i n m i c r o e m u l s i o n s somwehat by a c c i d e n t . I n t h e l a s t f i v e y e a r s o r so we h a v e been making s y s t e m a t i c s t u d i e s o f t h e thermodynamic p r o p e r t i e s of a q u e o u s o r g a n i c m i x t u r e s and o f e l e c t r o l y t e s i n t h e s e m i x e d s o l vents. Of p a r t i c u l a r i n t e r e s t w e r e o u r h e a t c a p a c i t y m e a s u r e m e n t s . W i t h a d i f f e r e n t i a l f l o w m i c r o c a l o r i m e t e r (5,6) i t i s p o s s i b l e t o m e a s u r e h e a t c a p a c i t i e s p e r u n i t v o l u m e t o a b o u t 10 p a r t s p e r j a i l l i o n a n d , f r o m t h e s e d a t a , d e r i v e a p p a r e n t (φ^) and p a r t i a l ( C ) m o l a l h e a t c a p a c i t i e s o f e a c h component. T h e s e C a r e a m e a s u r e o f t h e i n t r i n s i c h e a t c a p a c i t y o f t h e component p l u s c o n t r i b u t i o n s from t h e v a r i o u s i n t e r a c t i o n s between t h e components. B e i n g a s e cond d e r i v a t i v e o f t h e c h e m i c a l p o t e n t i a l w i t h r e s p e c t t o t e m p e r a t u r e , heat c a p a c i t y i s e s p e c i a l l y s e n s i t i v e t o changes i n the s t r u c t u r e o f s o l u t i o n s and i n p a r t i c u l a r t o t h o s e r e s u l t i n g i n e n e r g y f l u c t u a t i o n s i n t h e system. Organic m o l e c u l e s whigh a r e s o l u b l e i n water u s u a l l y have s t a n d a r d ( i n f i n i t e d i l u t i o n ) C w h i c h a r e s i g n i f i c a n t l y more p o s i t i v e than the molar heat c a p a c i t y C o f t h e p u r e s u b s t a n c e s . W i t h many l i q u i d s which are completely m i s c i b l e i n water (dimethylformamide, d ^ o x a n e ^ a c e t o n e , e t c . ) C d e c r e a s e s i n a f a i r l y r e g u l a r way f r o m C t o Cp. However, w i t h c e r t a i n h y d r o p h o b i c a l c o h o l s ( 7 ) , a l k o x y e t h a n o l s (8) and a m i n e s (9), C u n d e r g o e s d r a s t i c c h a n g e s i n t h e w a t e r - r i c h r e g i o n , e s p e c i a l l y a t lower temperature. Examples o f t h e s e c h a n g e s a r e shown i n F i g . 3 f o r t e r t - b u t a n o l , t r i e t h y l a m i n e and 2 - b u t o x y e t h a n o l i n w a t e r . T h e s e s y s t e m s show n e a r l y a f i r s t o r h i g h e r o r d e r t r a n s i t i o n , and b e y o n d 0.05 m o l e f r a c t i o n t h e C are c o n s t a n t and h a v e t h e v a l u e o f C , s u g g e s t i n g t h a t i n t h i s c o n c e n t r a t i o n r a n g e t h e o r g a n i c m o l e c u l e s l o c a l l y s e l d o m come i n t o c o n t a c t w i t h w a t e r m o l e c u l e s . T h e r e i s t h e r e f o r e some k i n d o f m i c r o p h a s e s e p a r a t i o n o c c u r i n g i n t h e s e b i n a r y s y s t e m s i n a way w h i c h c o u l d be a n a l o g o u s t o m i c e l l i z a t i o n ( 1 0 ) . C o n t i n u i n g s t u d i e s i n o u r l a b o r a t o r y seem t o i n d i c a t e t h a t t h e a d d i t i o n o f s u r f a c e a c t i v e m o l e c u l e s s t a b i l i z e f u r t h e r these pseudo-phases ( t r a n s i t i o n s a r e s h a r p e r and o c c u r a t l o w e r c o n c e n t r a t i o n s ) . I t i s our c o n t e n t i o n t h a t the s t r u c t u r e s which e x i s t i n these b i n a r y systems a r e l o c a l l y n o t t o o d i f f e r e n t f r o m t h o s e o f many s o - c a l l e d m i c r o e m u l s i o n s . p


p

p

p

p

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p

M i c r o e m u l s i o n s and O i l R e c o v e r y . One o f t h e i n t e r e s t i n g f e a t u r e s o f t h e s e b i n a r y s o l u t i o n s , and o f many m i c r o e m u l s i o n s , i s t h e i r t e n d e n c y t o unmix a t h i g h e r tempe rature. F o r e x a m p l e t r i e t h y l a m i n e - w a t e r m i x t u r e s unmix i n t o n e a r l y p u r e t r i e t h y l a m i n e and n e a r l y p u r e w a t e r a t 18.5°C; s i m i l a r l y 2b u t o x y e t h a n o l h a s a l o w e r c r i t i c a l s o l u t i o n t e m p e r a t u r e a t 49 C. T h i s p h a s e s e p a r a t i o n s u g g e s t s a new a p p r o a c h t o t h e p r o b l e m o f t e r t i a r y o i l r e c o v e r y . We c a n u s e s u c h b i n a r y s y s t e m s t o d i s s o l v e t h e o i l a t l o w t e m p e r a t u r e and t h e n r e c o v e r a good p a r t o f t h e o i l s i m p l y by r a i s i n g t h e t e m p e r a t u r e some 20 t o 30 d e g r e e s . This i s b a s e d on t h e a s s u m p t i o n t h a t , a t h i g h t e m p e r a t u r e , t e r n a r y s y s t e m s w i l l a l s o t e n d t o s e p a r a t e i n t o two p h a s e s , one o f w h i c h w o u l d be very r i c h i n o i l . T h i s s h o u l d be e s p e c i a l l y u s e f u l f o r t h e l i g h t e r


CHEMISTRY FOR ENERGY

36


1000 Et.N

«5

e

5C

Τ ΒΑ

25

C

-I 0.2 MOLE Figure

3.

Partial

molal

0.4 FRACTION

heat capacities of triethyhmine, text-hutoxyethanol in water

L· Ο.β

0.8

2-butoxyethanol,


1.0

and

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DESNOYERS ET A L .

Microemulsions

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Oil

37

Recovery

oils.


Decane-2-Butoxyethanol-Water

Phase

Diagrams.

The p h a s e d i a g r a m o f some o i l - s o l u b i l i z e r - w a t e r m u s t be measur e d as a f u n c t i o n o f temperature i n o r d e r to t e s t t h e above approach. F o r t h i s p u r p o s e d e c a n e (DEC) was c h o s e n a s a t y p i c a l o i l and 2-but o x y e t h a n o l (BE) a s t h e s o l u b i l i z e r . We t h o u g h t BE w o u l d be a good model s o l u b i l i z e r s i n c e the lower c r i t i c a l s o l u t i o n temperature f o r t h e BE-HÔ s y s t e m i s 49 C; t h i s g i v e s a good w o r k a b l e t e m p e r a t u r e range f o r our i n v e s t i g a t i o n . I n t h e s e e x p e r i m e n t s BE and DEC, f r o m B a k e r C h e m i c a l s ( P r a c t i c a l g r a d e ) , w e r e u s e d a s s u c h . Sodium d o d e c y l s u l f a t e (NaDDS), w h i c h was added t o t h e s o l u t i o n s i n some e x p e r i m e n t s , was f r o m BDH ( S p e c i a l l y p u r e ) . I t was d r i e d i n a vacuum o v e n b e f o r e u s e . The p h a s e d i a g r a m s w e r e d e t e r m i n e d by t h e c l o u d p o i n t t e c h n i que. A t a c o n s t a n t t e m p e r a t u r e (Sodev t e m p e r a t u r e contrôler, ± 0.001°C) t h e B E - H 0 s y s t e m s w e r e t i t r a t e d ( 2 . 5 m l G i l m o n t s y r i n ge) w i t h DEC u n t i l a s l i g h t c l o u d i n e s s a p p e a r e d , c o r r e s p o n d i n g t o t h e f o r m a t i o n o f two o r more p h a s e s . For temperature s t u d i e s , the t e m p e r a t u r e o f a known m i x t u r e o f BE-DEC-RÔ was v a r i e d u n t i l a c l o u d p o i n t was o b s e r v e d . The t e m p e r a t u r e was r e a d t o ± 0.01 C with a pre-calibrated thermistor. In general t h i s technique i s f a s t and q u i t e r e p r o d u c i b l e b u t d i f f i c u l t i e s a r e o f t e n e n c o u n t e r e d . I n t h e w a t e r - r i c h r e g i o n t h e s o l u b i l i t y o f DEC i s l o w . A t h i g h e r c o n c e n t r a t i o n s t h r e e p h a s e s o f t e n a p p e a r when e x c e s s DEC i s a d d e d . The t o p p h a s e c o n t a i n s m o s t l y DEC and t h e l o w e r one m o s t l y w a t e r . The c o e x i s t e n c e o f t h r e e p h a s e s i s t y p i c a l o f many m i c r o e m u l s i o n s systems ( 1 1 ) . To d e t e r m i n e t h e c o m p l e t e p h a s e d i a g r a m o f a t e r n a r y s y s t e m a s a f u n c t i o n of temperature, a t l e a s t a three-dimension diagram i s necessary. Such d i a g r a m s a r e u n f o r t u n a t e l y q u i t e d i f f i c u l t t o v i s u a l i z e and i t i s o f t e n p r e f e r a b l e t o r e d u c e t h e d i a g r a m s t o two d i m e n s i o n s by k e e p i n g t h e c o n c e n t r a t i o n o f some o f t h e components constant. Some r e s u l t s f o r t h e BE-RÔ p h a s e d i a g r a m a s a f u n c t i o n o f t e m p e r a t u r e f o r f i x e d q u a n t i t i e s o f DEC a r e shown i n F i g . 4. In t h i s d i a g r a m t h e m o l e f r a c t i o n o f BE r e f e r s t o t h e b i n a r y s y s t e m B E - H 0 ; e.g. Χ = 0 . 4 means 0.4 m o l e BE i n 0.6 m o l e s H 0 . On t h e o t h e r hand r e f e r s to the t e r n a r y systems; e.g. Χ Τ Λ 0.2 means 0.2 m o l e s o f DEC i n 0.8 m o l e s o f BE + R y ) . On t h e l e f t - h a n d s i d e o f F i g . 4 we h a v e t h e n o r m a l p h a s e d i a gram o f t h e b i n a r y BE-RÔ s y s t e m . The a d d i t i o n o f DEC s h i f t s t h e two p h a s e e q u i l i b r i a t o h i g h e r BE c o n c e n t r a t i o n s and t o l o w e r tem peratures. I f t h e a d d i t i o n o f a t h i r d component i s c o n t i n u e d beyond t h e c l o u d p o i n t , e v e n t u a l l y t h r e e d i s t i n c t phases appear. U n f o r t u n a t e l y t h e c l o u d p o i n t t e c h n i q u e g i v e s us t h e i n i t i a l c o n c e n t r a t i o n o r t e m p e r a t u r e where u n m i x i n g b e g i n s b u t i s n o t s u i t a b l e t o d i s t i n g u i s h b e t w e e n t h e c o e x i s t e n c e o f two p h a s e s and t h r e e phases. A l s o t h e t h r e e phase r e g i o n depends q u i t e c r i t i c a l l y on temperature. At h i g h e r t h a n 0.1, two o r more p h a s e s a p p e a r a t h i g h 2

2

β Ε

2

=

Ε

Γ




Figure 4. Phase diagram of decane-2-butoxyethanol-water for a constant centration of decane. The mole fraction of BE is expressed relative to water and the mole fraction of DEC relative to the BE-HgO.


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DESNOYERS ET A L .

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t e m p e r a t u r e s and a l s o a t l o w t e m p e r a t u r e s . T h i s p r o b a b l y s u g g e s t s t h a t t h e r e e x i s t s a l s o an upper c r i t i c a l temperature i n the b i n a r y s y s t e m BE-HÔ a t l o w t e m p e r a t u r e . T h e s e l o w e r and u p p e r c l o u d p o i n t s w e r e u n f o r t u n a t e l y n o t d e t e r m i n e d a t e x a c t l y t h e same X^ ^. S t i l l we c a n r e a d i l y s e e f r o m P i g . 4 t h a t f o r n e a r 0.1 ana Χ = 0.4 t h e s y s t e m w i l l e x i s t i n two p h a s e s b e l o w 20^0, w i l l be c o m p l e t e l y m i s c i b l e a b o v e t h i s t e m p e r a t u r e and i t w i l l a g a i n s e p a r a t e o u t i n t o two p h a s e s a b o v e 80 C. A g a i n t h r e e p h a s e s seem t o a p p e a r when t h e c l o u d p o i n t i s e x c e e d e d . A s i m i l a r phase diagram f o r a f i x e d X^ and a v a r i a b l e X ^ ^ i s shown i n F i g . 5. A t l o w X^ the system i s r e l a t i v e l y s i m p l e . For e x a m p l e , f o r X ^ = 0.45 ana ^ = 0.225 two p h a s e s e x i s t b e l o w 28 C ( p o i n t a ) , a s i n g l e p h a s e between 28°C and 55 C ( p o i n t s b and c ) and a g a i n two p h a s e s a b o v e 55°C ( p o i n t d) . A t h i g h X ^ ™ the s i t u a t i o n becomes v e r y c o m p l e x . O n l y one c a s e i s shown f o r X ^ = 0.70. A t Xp = 0.755 a c l e a r s o l u t i o n i s o b s e r v e d b e l o w 20 C ( p o i n t e;, a c l o u d y m i x t u r e a p p e a r s a b o v e 20 C b u t d o e s n o t u n m i x ( p o i n t g ) , and two d i s t i n c t p h a s e s a r e p r e s e n t a b o v e 35 C ( p o i n t h ) . We a r e p o s s i b l y i n a r e g i o n w h e r e l i q u i d c r y s t a l s o r i n v e r s e m i c e l l e s a r e formed. The t e r n a r y p h a s e d i a g r a m w h e r e t h e t e m p e r a t u r e i s k e p t c o n s t a n t a r e shown i n F i g . 6. H e r e X^ and X are both expressed r e l a t i v e to the t e r n a r y systems. I n t h i s d i a g r a m we show o n l y t h e cloud points corresponding to the i n i t i a l unmixing. I n t h e DECr i c h r e g i o n t h e d i a g r a m becomes t o o c o m p l e x t o f i x u n a m b i g u o u s l y the phase diagram. D a t a a r e shown f o r 2 5 , 40 and 70 C. A g a i n we c a n s e e t h a t f o r X^ b e t w e e n 0.2 and 0.5 t h e s o l u b i l i t y o f DEC i s l a r g e r a t 40°C t h a n a t 25 and 70°C. The e f f e c t o f a d d i n g a s u r f a c t a n t , (NaDDS), was a l s o i n v e s t i gated. One s u c h c a s e o n l y i s shown i n F i g . 6 w h e r e BE i s r e p l a c e d by a 5:1 m i x t u r e o f BE-NaDDS. The m a i n e f f e c t o f NaDDS i s t o i n crease the m i s c i b i l i t y range of the o i l i n water. Various ratios o f BE-NaDDS w e r e u s e d a n d , a s a f i r s t a p p r o x i m a t i o n , t h e c h a n g e i n the p h a s e d i a g r a m i s d i r e c t l y p r o p o r t i o n a l t o t h e c o n c e n t r a t i o n o f NaDDS. The a d d i t i o n o f a s u r f a c t a n t p r o b a b l y s t a b i l i z e s t h e m i c r o s t r u c t u r e s w h i c h w e r e a l r e a d y p r e s e n t i n t h e t e r n a r y s y s t e m BE-DECHÔ and d e c r e a s e s t h e q u a n t i t y o f BE n e e d e d t o s o l u b i l i z e DEC. Therefore the presence of a s u r f a c t a n t i s u s e f u l but not e s s e n t i a l to t h e s t a b i l i t y o f m i c r o e m u l s i o n s . E

β Ε


E

E

H e a t C a p a c i t y o f Decane i n M i c r o e m u l s i o n s . H e a t c a p a c i t y m e a s u r e m e n t s s h o u l d be v e r y u s e f u l i n d e t e r m i n ing the l o c a l s t r u c t u r e i n microemulsions. A complete study w i l l i n v o l v e k e e p i n g one component n e a r i n f i g i t e d i l u t i o n and v a r y t h e r a t i o o f t h e o t h e r two. The s t a n d a r d C o f t h e f i r s t component w i l l t h e n i n f o r m u s on t h e e n v i r o n m e n t o f t h e m o l e c u l e . This s h o u l d be done f o r BE, DEC and HÔ a s t h e r e f e r e n c e component. Then i n a s e c o n d s e t o f e x p e r i m e n t s t h e m o l e f r a c t i o n o f a l l com p o n e n t s s h o u l d be v a r i e d s i m u l t a n e o u s l y . T h i s i s a l o n g - t e r m p r o j e c t and o n l y p r e l i m i n a r y r e s u l t s w i l l be p r e s e n t e d h e r e f o r DEC a s p




Figure 5. Phase diagram of decane-2-butoxyetlianol-water for a constant concentration of 2-butoxyethanol. The mole fraction of BE is expressed relative to water only and the mole fraction of DEC relative to the BE-H 0 mixture. 2


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Figure 6. Phase diagram of decane-2-butoxyethanol-water for a constant temperature. All mole fractions are expressed relative to the other two components.


41

42


t h e r e f e r e n c e component. The a p p a r e n t m o l a l h e a t c a p a c i t y φ^, o f DEC was m e a s u r e d i n BEm i x t u r e s w i t h a f l o w m i c r o c a l o r i m e t e r (6,2.) f o l l o w i n g t h e u s u a l p r o c e d u r e f o r t e r n a r y s y s t e m s ( 1 2 ) . I n m o s t e x p e r i m e n t s DEC was k e p t a t v e r y l o w m o l a l i t i e s and X g was v a r i e d o v e r a w i d e r a n g e ( T a b l e 1 ) . I n p u r e w a t e r and i n v e r y d i l u t e BE s o l u t i o n s t h e s o l u b i l i t y o f DEC i s t o o l o w f o r d i r e c t φ m e a s u r e m e n t s . However Cp o f DEC i n p u r e w a t e r c a n be e s t i m a t e d r e a s o n a b l y w e l l t h r o u g h a d d i t i v i t y r u l e s (13,14) and h a s t h e v a l u e 1060 J Κ mol" at 25°C On t h e o t h e r hand Cl o f DEC i n p u r e BE i s a b o u t 345 J Κ mol . Except f o r data p o i n t s near = 0.05, w h i c h c o r r e s p o n d s t o t h e t r a n s i t i o n r e g i o n , φ^φΕΟ) d o e s n o t v a r g much w i t h t h e DEC o r BE c o n c e n t r a t i o n and h a s a v a l u e c l o s e t o C o f DEC i n p u r e BE. T h i s s t r o n g l y s u g g e s t s t h a t DEC m o l e c u l e s a r e e s s e n t i a l l y i n c o n t a c t w i t h BE o n l y . This i s again consistent with the hypothesis t h a t t h e BE-HÔ s y s t e m e x i s t s a s m i c r o p h a s e s a b o v e 0.05 m o l e fractions. E

1


p

TABLE I HEAT CAPACITY OF DECANE I N 2-BUT0XYETHAN0L-WATER MIXTURES AT

ÊC mol

V

kg

Φ (ΒΕΟ 0

BE

-1

0.0245 0.0329 0.0377 0.0476 0.0360 0.0630 0.0974 0.116 0.0268 0.0556 0.1113 0.2334 0.3303 0.9954 1.5546

J K" 0.05

p

1

mol"

1

242.5 291.6 324.6 356.8 327.6 331.0 350.5 372.7 341.5 342.2 339.3 353.0 352.0 345.3 344.7

0.10

0.20

0.45 pure

C o f p u r e d e c a n e = 314.6 J Κ mol" _ Cp o f d e c a n e i n p u r e w a t e r = 1060 J Κ

25°C.

_

χ

χ

mol

Conclusion. The w o r k p r e s e n t e d h e r e the s o l u b i l i z a t i o n of o i l i n c a n be u s e d a s m o d e l s y s t e m s demonstrated t h a t the use of

i s e s s e n t i a l l y a preliminary study of s i m p l e b i n a r y aqueous systems w h i c h f o r m i c r o e m u l s i o n s . S t i l l , i t was phase s e p a r a t i o n t o r e c o v e r t h e o i l


4. DESNOYERS ET AL.

43 Microemulsions and Tertiary Oil Recovery

from microemulsions is feasible. For this purpose BE is probably not the best solubilizer since the concentration range where the microemulsion can be destabilized by a change in temperature is too narrow and BE is not stable at high pH. Solubilizers like triethylamine and diethyImethylamine could be more interesting in this res pect since the lower critical solution region is very flat. These systems are presently under study in our laboratory. Acknowledgement.


JED is grateful to Imperial Oil and to the Quebec Ministry of Education for financial help. G.R. is also grateful for a FranceQuebec exchange fellowship. Abstract. Microemulsions are very promissing for tertiary o i l recovery in view of their capacity to dissolve large quantities of nonpolar molecules. Studies of the thermodynamics of organic aqueous mixtu res have indicated that some polar organic liquids miscible with water, such as alcohols, amines and alkoxyethanols can exist in water as microphases or aggregates similar to micelles. These microphases can be further stabilized by the addition of third com ponent such as a surfactant. As a model system the phase diagram of the ternary systems 2-butoxyethanol-decane-water was determined as a function of temperature. This ternary system unmixes at low and high temperatures. The effect of sodium dodecyl sulfate on the phase diagram was also investigated. The addition of a sur factant increases significantly the solubility of decane. Heat capacity measurements suggests that decane, when dissolved in a 2-butoxyethano1-water mixture, essentially comes in contact with the nonaqueous component only. Literature cited. 1. Bansal, V.K., Shaw, D.O. "Microemulsions, Theory and Practice" edited by Prince, L.M., Academic Press, New York, 1977, chap ter 7. 2. Prince, L.M. ref (1) chapter 1 and 2. 3. Prince, L.M. Ref (1) chapter 5. 4. Friberg, S. ref (1) chapter 6. 5. Picker, P., Leduc, P.Α., Philip, P.R., Desnoyers, J.Ε., J. Chem. Thermodyn. (1971), 3, 631. 6. Desnoyers, J.E., de Visser, C., Perron, G., Picker, P., J. Solution Chem. (1976), 5, 605. 7. de Visser, C., Perron, G., Desnoyers, J.E., Can. J. Chem. (1977), 55, 856. 8. Roux, G., Perron, G., Desnoyers, J.E., J. Solution Chem. (in press). 9. Roux, G., Perron, G., de Visser, C., Desnoyers, J.E. (in pre paration.


44


10. Roux, G., Perron, G., Desnoyers, J.E., J. Phys. Chem. (1978), 82, 966. 11. Friberg, S., Buraczewska, I., "Micellization, Solubilization and Microemulsions, edited by Millta, K.L., Plenum Press, New York, 1977, 791. 12. Avedikian, L . , Perron, G., Desnoyers, J.E., J. Solution Chem. (1975), 4, 331. 13. Nichols, N., Sköld, R., Spink, C., Suurkuusk, J . , Wadsö, I., J. Chem. Thermodyn. (1976), 8, 1081. 14. Perron, G., Desnoyers, J.E., Fluid Phase Equil. (in press).


RECEIVED July 18,1978.


Microemulsions as a Possible Tool for Tertiary Oil Recovery

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