Petroleum Emulsions - Advances in Chemistry (ACS Publications)

1 Petroleum Emulsions Basic Principles

Downloaded by FORDHAM UNIV on December 7, 2012 | http://pubs.acs.org Publication Date: May 5, 1992 | doi: 10.1021/ba-1992-0231.ch001

Laurier L . Schramm Petroleum Recovery Institute, 3512 33rd Street N.W., Calgary, Alberta, Canada T 2 L 2A6

This chapter provides an introduction to the occurrence, properties, and importance of petroleum emulsions. From light crude oils to bitumens, spanning a wide array of bulk physical properties and stabilities, a common starting point for understanding emulsions is provided by the fundamental principles of colloid science. These principles may be applied to emulsions in different ways to achieve quite different results. A desirable emulsion that must be carefully stabilized to assist one stage of an oil production process may be undesirable in another stage and necessitate a demulsification strategy. With an emphasis on the definition of important terms, the importance of interfacial properties to emulsion making and stability is demonstrated. Demulsification is more complex than just the reverse of emulsion making, but can still be approached from an understanding of how emulsions can be stabilized.

Importance of Emulsions I f t w o i m m i s c i b l e l i q u i d s are m i x e d together i n a c o n t a i n e r a n d t h e n shaken, e x a m i n a t i o n w i l l reveal that o n e o f the two phases has b e c o m e a c o l l e c t i o n o f d r o p l e t s that are d i s p e r s e d i n t h e o t h e r phase; a n e m u l s i o n has b e e n f o r m e d ( F i g u r e 1). E m u l s i o n s have l o n g b e e n o f great p r a c t i c a l interest because o f t h e i r w i d e s p r e a d o c c u r r e n c e i n everyday l i f e . S o m e i m p o r t a n t a n d f a m i l i a r e m u l s i o n s i n c l u d e those o c c u r r i n g i n foods ( m i l k , mayonnaise, etc.), c o s m e t ics (creams a n d lotions), p h a r m a c e u t i c a l s (soluble v i t a m i n a n d h o r m o n e p r o d u c t s ) , a n d a g r i c u l t u r a l p r o d u c t s (insecticide a n d h e r b i c i d e e m u l s i o n f o r m u l a t i o n s ) . I n a d d i t i o n to t h e i r w i d e o c c u r r e n c e , e m u l s i o n s have i m p o r 0065-2393/92/0231-0001 $13.25/0 © 1992 American Chemical Society

In Emulsions; Schramm, L.; Advances in Chemistry; American Chemical Society: Washington, DC, 1992.


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E M U L S I O N S I N T H E P E T R O L E U M INDUSTRY

Figure 1. Photomicrograph of an emulsified droplet of a crude oil, dispersed in the aqueous solution that was used to release it from the mineral matrix in which it was originally held. An interfacial film is obvious at the surface of the droplet. tant p r o p e r t i e s that may b e desirable, f o r example, i n a n a t u r a l o r f o r m u l a t e d p r o d u c t , o r u n d e s i r a b l e , s u c h as an u n w a n t e d e m u l s i o n i n an i n d u s t r i a l process. P e t r o l e u m e m u l s i o n s m a y not b e as f a m i l i a r b u t have a s i m i l a r l y widespread, long-standing, and important occurrence i n industry. E m u l sions m a y be e n c o u n t e r e d at a l l stages i n the p e t r o l e u m r e c o v e r y a n d p r o cessing i n d u s t r y ( d r i l l i n g fluid, p r o d u c t i o n , process p l a n t , a n d transportation e m u l s i o n s ) . T h i s c h a p t e r p r o v i d e s an i n t r o d u c t i o n to the basic p r i n c i p l e s i n v o l v e d i n the o c c u r r e n c e , m a k i n g , a n d b r e a k i n g o f p e t r o l e u m e m u l s i o n s . C r u d e oils consist of, at least, a range o f h y d r o c a r b o n s (alkanes, n a p h thenes, a n d a r o m a t i c c o m p o u n d s ) as w e l l as p h e n o l s , carboxylic acids, a n d metals. A significant f r a c t i o n o f s u l f u r a n d n i t r o g e n c o m p o u n d s m a y b e present as w e l l . T h e c a r b o n n u m b e r s o f a l l these c o m p o n e n t s range f r o m 1 (methane) t h r o u g h 50 o r m o r e (asphaltenes). S o m e o f these c o m p o n e n t s c a n f o r m films at o i l surfaces, a n d others are surface active. It is perhaps not s u r p r i s i n g , t h e n , that the tendencies to f o r m stable o r unstable e m u l s i o n s o f d i f f e r e n t k i n d s vary greatly a m o n g d i f f e r e n t oils. B e c a u s e o f the w i d e range o f possible c o m p o s i t i o n s , c r u d e oils c a n exhibit a w i d e range o f viscosities a n d densities, so m u c h so that these p r o p e r t i e s are u s e d to d i s t i n g u i s h l i g h t , heavy, a n d b i t u m i n o u s c r u d e oils. O n e set o f definitions c a n be c o m p i l e d as follows ( 1 - 3 ) :


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SCHRAMM

Viscosity Range (mPa-s), at Reservoir Temperature

Hydrocarbon Light crude oil Heavy crude oil Extra heavy crude oil Bitumen (tar)


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Basic Principles

Density Range (kg/m ), at 15.6 °C 3

< 10,000 < 10,000 < 10,000 > 10,000

1000 >1000

B e c a u s e the viscosities c o r r e s p o n d to a m b i e n t deposit t e m p e r a t u r e s , the v a r i a t i o n i n these p r o p e r t i e s over d i f f e r e n t t e m p e r a t u r e s is e v e n greater t h a n the table suggests. F o r e x a m p l e , b i t u m e n i n the A t h a b a s c a deposit o f n o r t h e r n A l b e r t a is c h e m i c a l l y s i m i l a r to c o n v e n t i o n a l o i l b u t has a viscosity, at reservoir t e m p e r a t u r e , o f about 1 0 mPa-s (1 m i l l i o n times greater t h a n that o f water). D u r i n g h e a t i n g , as part o f an o i l r e c o v e r y process s u c h as hotw a t e r flotation o r i n situ steam flooding, e m u l s i o n s h a v i n g a w i d e range o f viscosities c a n be f o r m e d , p a r t i c u l a r l y i f they are o f the w a t e r d i s p e r s e d i n o i l type. W h e n these d i f f e r e n t k i n d s o f oils are e m u l s i f i e d , the e m u l s i o n s m a y have viscosities that are m u c h greater t h a n , s i m i l a r to, o r m u c h less t h a n the viscosity o f the c o m p o n e n t o i l , a l l d e p e n d i n g o n the nature o f the e m u l s i o n formed. 6

A s s h o w n i n T a b l e I, p e t r o l e u m e m u l s i o n s m a y b e desirable o r u n d e sirable. F o r example, one k i n d o f o i l - w e l l d r i l l i n g fluid (or " m u d " ) is e m u l sion based. H e r e a stable e m u l s i o n (usually o i l d i s p e r s e d i n water) is u s e d to l u b r i c a t e the c u t t i n g b i t a n d to carry cuttings u p to the surface. T h i s e m u l sion is o b v i o u s l y desirable, a n d great care goes i n t o its p r o p e r p r e p a r a t i o n . A n e m u l s i o n may be desirable i n one part o f the o i l p r o d u c t i o n process a n d u n d e s i r a b l e at the next stage. F o r e x a m p l e , i n the o i l fields, an i n s i t u Table I. Examples of Emulsions in the Petroleum Industry Occurrence Undesirable Emulsions Well-head emulsions F u e l oil emulsions (marine) O i l sand flotation process, froth O i l sand flotation process, diluted froth O i l spill mousse emulsions Tanker bilge emulsions Desirable Emulsions Heavy oil pipeline emulsion O i l sand flotation process slurry Emulsion drilling fluid, oil-emulsion mud Emulsion drilling fluid, oil-base mud Asphalt emulsion Enhanced oil recovery i n situ emulsions

Usual Type

a

W/O W/O W/O or O/W O/W/O W/O O/W O/W O/W O/W W/O O/W O/W

"W/O means water-in-oil; O/W means oil-in-water. See the section "Definition and Classification of Emulsions".


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e m u l s i o n that is p u r p o s e l y c r e a t e d i n a reservoir as part o f a n o i l r e c o v e r y process m a y change to a d i f f e r e n t , u n d e s i r a b l e type o f e m u l s i o n (water d i s p e r s e d i n oil) w h e n p r o d u c e d at t h e w e l l h e a d . T h i s e m u l s i o n m a y have to be b r o k e n a n d r e f o r m u l a t e d as a n e w e m u l s i o n suitable for t r a n s p o r t a t i o n b y p i p e l i n e to a refinery. H e r e , t h e n e w e m u l s i o n w i l l have to b e b r o k e n a n d w a t e r f r o m t h e e m u l s i o n r e m o v e d ; o t h e r w i s e t h e w a t e r w o u l d cause process i n g p r o b l e m s i n t h e r e f i n i n g process. E m u l s i o n s may c o n t a i n not just o i l a n d water, b u t also s o l i d particles a n d e v e n gas. I n t h e large m i n i n g a n d p r o c e s s i n g operations a p p l i e d to C a n a d i a n o i l sands, b i t u m e n is separated f r o m t h e sand matrix i n large t u m b l e r s as an e m u l s i o n o f o i l d i s p e r s e d i n water, a n d t h e n f u r t h e r separated f r o m the t u m b l e r s l u r r y b y a flotation process. T h e p r o d u c t o f the flotation process is b i t u m i n o u s f r o t h , an e m u l s i o n that m a y b e e i t h e r w a t e r (and air) d i s p e r s e d i n t h e o i l ( p r i m a r y flotation) o r t h e reverse, o i l (and air) d i s p e r s e d i n w a t e r (secondary flotation). I n either case, t h e e m u l s i o n s must b e b r o k e n a n d t h e w a t e r r e m o v e d b e f o r e t h e b i t u m e n c a n b e u p g r a d e d to synthetic c r u d e o i l , b u t t h e p r e s e n c e o f s o l i d particles a n d film-forming c o m p o n e n t s f r o m t h e b i t u m e n c a n m a k e this r e m o v a l step v e r y d i f f i c u l t . S o m e e m u l s i o n s are m a d e to r e d u c e viscosity so that a n o i l c a n b e m a d e to flow. E m u l s i o n s o f asphalt, a s e m i s o l i d variety o f b i t u m e n d i s p e r s e d i n water, are f o r m u l a t e d to b e b o t h less viscous t h a n t h e o r i g i n a l asphalt a n d stable so that they c a n b e t r a n s p o r t e d a n d h a n d l e d . I n a p p l i c a t i o n , t h e e m u l s i o n s h o u l d shear t h i n a n d b r e a k to f o r m a suitable w a t e r - r e p e l l i n g roadway c o a t i n g m a t e r i a l . A n o t h e r example o f e m u l s i o n s that are f o r m u l a t e d for l o w e r viscosity w i t h g o o d stability are those m a d e f r o m heavy oils a n d i n t e n d e d f o r e c o n o m i c p i p e l i n e t r a n s p o r t a t i o n over large distances. H e r e again t h e e m u l s i o n s s h o u l d b e stable f o r transport b u t w i l l n e e d to b e b r o k e n at t h e e n d o f t h e p i p e l i n e . F i n a l l y , m a n y k i n d s o f e m u l s i o n s pose d i f f i c u l t p r o b l e m s w h e r e v e r t h e y may o c c u r . F o r example, c r u d e o i l w h e n s p i l l e d o n t h e o c e a n tends to b e c o m e e m u l s i f i e d i n t h e f o r m o f " c h o c o l a t e m o u s s e " e m u l s i o n s , so n a m e d f o r t h e i r c o l o r a n d s e m i s o l i d consistency. T h e s e w a t e r - i n - o i l e m u l s i o n s w i t h h i g h w a t e r c o n t e n t t e n d to b e q u i t e stable d u e to t h e strong s t a b i l i z i n g films that are present. M o u s s e e m u l s i o n s increase t h e q u a n t i t y o f p o l l u t a n t a n d are u s u a l l y v e r y m u c h m o r e viscous than t h e o i l itself. A l l o f t h e p e t r o l e u m e m u l s i o n applications o r p r o b l e m s just d i s c u s s e d have i n c o m m o n t h e same basic p r i n c i p l e s o f c o l l o i d science that g o v e r n t h e nature, stability, a n d p r o p e r t i e s o f e m u l s i o n s . T h e w i d e s p r e a d i m p o r t a n c e o f e m u l s i o n s i n general a n d scientific interest i n t h e i r f o r m a t i o n , stability, a n d p r o p e r t i e s have p r e c i p i t a t e d a w e a l t h o f p u b l i s h e d l i t e r a t u r e o n t h e subject. T h i s c h a p t e r p r o v i d e s an i n t r o d u c t i o n a n d is i n t e n d e d to c o m p l e m e n t t h e o t h e r chapters i n this b o o k o n p e t r o l e u m e m u l s i o n s . A g o o d starting p o i n t f o r f u r t h e r basic i n f o r m a t i o n is o n e o f the classic texts: B e c h e r ' s Emulsions: Theory and Practice (4) o r S u m n e r ' s Clayton's Theory of Emulsions and


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Basic Principles

5

Their Technical Treatment (5) a n d n u m e r o u s o t h e r books o n e m u l s i o n s (611). M o s t g o o d c o l l o i d c h e m i s t r y texts c o n t a i n i n t r o d u c t o r y chapters o n e m u l s i o n s (12-14), a n d some chapters i n specialist m o n o g r a p h s (15,16) give m u c h m o r e d e t a i l e d treatment o f advances i n specific e m u l s i o n areas.


Emulsions as Colloidal Systems D e f i n i t i o n a n d Classification o f E m u l s i o n s . C o l l o i d a l d r o p lets (or particles o r b u b b l e s ) , as they are u s u a l l y d e f i n e d , have at least o n e d i m e n s i o n b e t w e e n about 1 a n d 1000 n m . E m u l s i o n s are a s p e c i a l k i n d o f c o l l o i d a l d i s p e r s i o n : o n e i n w h i c h a l i q u i d is d i s p e r s e d i n a c o n t i n u o u s l i q u i d phase o f d i f f e r e n t c o m p o s i t i o n . T h e d i s p e r s e d phase is sometimes r e f e r r e d to as t h e i n t e r n a l (disperse) phase, a n d t h e c o n t i n u o u s phase as t h e external phase. E m u l s i o n s also f o r m a rather special k i n d o f c o l l o i d a l system i n that the droplets o f t e n e x c e e d t h e size l i m i t o f 1000 n m . I n p e t r o l e u m e m u l s i o n s one o f the l i q u i d s is aqueous, a n d t h e o t h e r is h y d r o c a r b o n a n d r e f e r r e d to as o i l . T w o types o f e m u l s i o n are n o w r e a d i l y d i s t i n g u i s h e d i n p r i n c i p l e , d e p e n d i n g u p o n w h i c h k i n d o f l i q u i d forms t h e c o n t i n u o u s phase ( F i g u r e 2): 1. o i l - i n - w a t e r (O/W) f o r o i l d r o p l e t s d i s p e r s e d i n w a t e r 2. w a t e r - i n - o i l (W/O) f o r w a t e r droplets d i s p e r s e d i n o i l T h i s k i n d o f classification is n o t always a p p r o p r i a t e . F o r e x a m p l e , O/W/O denotes a m u l t i p l e e m u l s i o n c o n t a i n i n g o i l d r o p l e t s d i s p e r s e d i n aqueous droplets that are i n t u r n d i s p e r s e d i n a c o n t i n u o u s o i l phase. T h e type o f e m u l s i o n that is f o r m e d depends u p o n a n u m b e r o f factors. I f t h e ratio o f phase v o l u m e s is v e r y large o r v e r y s m a l l , t h e n t h e phase h a v i n g t h e s m a l l e r v o l u m e is f r e q u e n t l y t h e d i s p e r s e d phase. I f t h e ratio is closer to 1, t h e n

Figure 2. The two simplest kinds of emulsions. The droplet sizes have been greatly exaggerated.



6


o t h e r factors d e t e r m i n e the o u t c o m e . T a b l e I lists some s i m p l e examples o f p e t r o l e u m e m u l s i o n types. T w o v e r y d i f f e r e n t b r o a d types o f c o l l o i d a l dispersions have b e e n d i s t i n g u i s h e d since G r a h a m i n v e n t e d the t e r m " c o l l o i d " i n 1861. O r i g i n a l l y , c o l loids w e r e s u b d i v i d e d i n t o l y o p h o b i c a n d l y o p h i l i c c o l l o i d s (if the d i s p e r s i o n m e d i u m is aqueous t h e n the terms h y d r o p h o b i c a n d h y d r o p h i l i e , respec tively, are used). L y o p h i l i c c o l l o i d s are f o r m e d spontaneously w h e n the t w o phases are b r o u g h t together, because the d i s p e r s i o n is t h e r m o d y n a m i c a l l y m o r e stable t h a n the o r i g i n a l separated state. T h e t e r m l y o p h i l i c is less f r e q u e n t l y u s e d i n m o d e r n p r a c t i c e because m a n y o f the dispersions that w e r e o n c e t h o u g h t o f as l y o p h i l i c are n o w r e c o g n i z e d as single-phase sys tems i n w h i c h large m o l e c u l e s are d i s s o l v e d . L y o p h o b i c c o l l o i d s , w h i c h i n c l u d e a l l p e t r o l e u m e m u l s i o n s other t h a n the m i c r o e m u l s i o n s , are not f o r m e d spontaneously o n c o n t a c t o f the phases because they are t h e r m o d y n a m i c a l l y unstable c o m p a r e d w i t h the separated states. T h e s e dispersions c a n b e f o r m e d b y o t h e r means, h o w e v e r . M o s t p e t r o l e u m emulsions that w i l l be e n c o u n t e r e d i n p r a c t i c e c o n t a i n o i l , w a t e r , a n d an e m u l s i f y i n g agent. T h e e m u l s i f i e r may c o m p r i s e one o r m o r e o f the f o l l o w i n g : s i m p l e i n o r g a n i c electrolytes, surfactants, m a c r o m o l e c u l e s , o r finely d i v i d e d solids. T h e e m u l s i f y i n g agent may be n e e d e d to r e d u c e i n t e r f a c i a l t e n s i o n a n d a i d i n the f o r m a t i o n o f the i n c r e a s e d i n t e r f a c i a l area w i t h a m i n i m u m o f m e c h a n i c a l energy i n p u t , o r it m a y b e n e e d e d to f o r m a p r o t e c t i v e film at the d r o p l e t surfaces that acts to p r e v e n t coalescence w i t h other d r o p l e t s . T h e s e aspects w i l l b e discussed later; the r e s u l t i n g e m u l s i o n may w e l l have c o n s i d e r a b l e stability as a metastable d i s p e r s i o n . M o s t k i n d s o f e m u l s i o n s that w i l l b e e n c o u n t e r e d i n p r a c t i c e are l y o p h o bic, metastable e m u l s i o n s . H o w e v e r , t h e r e r e m a i n some grey areas i n w h i c h the d i s t i n c t i o n b e t w e e n l y o p h i l i c a n d l y o p h o b i c dispersions is not c o m p l e t e l y clear. A s p e c i a l class o f aggregated surfactant m o l e c u l e s t e r m e d " m i c e l l e s " a n d the m i c r o e m u l s i o n s o f e x t r e m e l y s m a l l d r o p l e t size are u s u ally b u t not always c o n s i d e r e d to be l y o p h i l i c , stable, c o l l o i d a l dispersions and w i l l be d i s c u s s e d separately. Stability. A c o n s e q u e n c e o f the s m a l l d r o p l e t size a n d p r e s e n c e o f an i n t e r f a c i a l film o n the droplets i n e m u l s i o n s is that q u i t e stable dispersions o f these species c a n be m a d e . T h a t is, the s u s p e n d e d d r o p l e t s d o not settle out o r float r a p i d l y , a n d the d r o p l e t s d o not coalesce q u i c k l y . S o m e use o f the t e r m stability has already b e e n m a d e w i t h o u t d e f i n i t i o n . C o l l o i d a l species c a n c o m e together i n v e r y d i f f e r e n t ways. I n the d e f i n i t i o n o f e m u l s i o n stability, stability is c o n s i d e r e d against three d i f f e r e n t processes: c r e a m i n g (sedimentation), aggregation, a n d coalescence. C r e a m i n g is the opposite o f s e d i m e n t a t i o n a n d results f r o m a density d i f f e r e n c e b e t w e e n the t w o l i q u i d phases. I n aggregation t w o o r m o r e droplets c l u m p together, t o u c h i n g o n l y at c e r t a i n p o i n t s , a n d w i t h v i r t u a l l y no change i n


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Basic Principles

7


total surface area. A g g r e g a t i o n is sometimes r e f e r r e d to as flocculation o r c o a g u l a t i o n . I n coalescence t w o o r m o r e d r o p l e t s fuse t o g e t h e r to f o r m a single larger u n i t w i t h a r e d u c e d total surface area. I n aggregation t h e species r e t a i n t h e i r i d e n t i t y b u t lose t h e i r k i n e t i c i n d e p e n d e n c e because the aggregate moves as a single u n i t . A g g r e g a t i o n o f droplets m a y l e a d to coalescence a n d the f o r m a t i o n o f larger droplets u n t i l the phases b e c o m e separated. I n coalescence, o n the o t h e r h a n d , t h e o r i g i n a l species lose t h e i r i d e n t i t y a n d b e c o m e part o f a n e w species. K i n e t i c stability c a n thus have d i f f e r e n t meanings. A n e m u l s i o n c a n b e k i n e t i c a l l y stable w i t h respect to coalescence b u t unstable w i t h respect to aggregation. O r , a system c o u l d b e k i n e t i c a l l y stable w i t h respect t o aggregation b u t unstable w i t h respect to s e d i m e n t a t i o n o r flotation. I n s u m m a r y , l y o p h o b i c e m u l s i o n s are t h e r m o d y n a m i c a l l y unstable b u t may b e relatively stable i n a k i n e t i c sense. S t a b i l i t y must b e u n d e r s t o o d i n terms o f a clearly d e f i n e d process. M i c r o e m u l s i o n s . I n some systems t h e a d d i t i o n o f a f o u r t h c o m p o nent, a cosurfactant, to a n o i l - w a t e r - s u r f a c t a n t system c a n cause the i n t e r f a c i a l t e n s i o n to d r o p t o near-zero values, easily o n t h e o r d e r o f 10~ to 1(Γ* m N / m ; l o w i n t e r f a c i a l t e n s i o n allows spontaneous o r n e a r l y spontaneous e m u l s i f i c a t i o n to v e r y s m a l l d r o p l e t sizes, c a . 10 n m o r s m a l l e r . T h e droplets c a n b e so s m a l l that they scatter little l i g h t ; t h e e m u l s i o n s appear to b e transparent a n d d o n o t break o n s t a n d i n g o r c e n t r i f u g i n g . U n l i k e coarse e m u l s i o n s , these m i c r o e m u l s i o n s are usually t h o u g h t to b e t h e r m o d y n a m i cally stable. T h e t h e r m o d y n a m i c stability is f r e q u e n t l y a t t r i b u t e d to t r a n sient negative i n t e r f a c i a l tensions, b u t this hypothesis a n d t h e q u e s t i o n o f w h e t h e r m i c r o e m u l s i o n s are r e a l l y l y o p h i l i c o r l y o p h o b i c dispersions are areas o f some d i s c u s s i o n i n t h e literature (17). A s a p r a c t i c a l matter, m i c r o e m u l s i o n s c a n b e f o r m e d , have some special qualities, a n d c a n have i m p o r t a n t applications. 3

M i c r o e m u l s i o n s c a n f o r m t h e basis f o r a n e n h a n c e d o i l r e c o v e r y ( E O R ) process (18-20). I n an o i l - c o n t a i n i n g reservoir, t h e relative o i l a n d w a t e r saturations d e p e n d u p o n t h e d i s t r i b u t i o n o f p o r e sizes i n t h e r o c k as f o l l o w s . T h e c a p i l l a r y pressure ( F ) , o r pressure d i f f e r e n c e across a n o i l - w a t e r i n t e r face s p a n n i n g a p o r e , is c

P = 2y cos θ I r c

p

(1)

w h e r e 7 is the o i l - w a t e r i n t e r f a c i a l t e n s i o n ; θ is t h e contact angle, w h i c h is the angle m e a s u r e d t h r o u g h t h e w a t e r phase at t h e p o i n t o f o i l - w a t e r - r o c k contact; a n d r is t h e p o r e r a d i u s . T h e basis f o r this e q u a t i o n is d i s c u s s e d f u r t h e r i n a later section. I n a n i d e a l i z e d w a t e r - w e t reservoir, t h e i n t e r f a c i a l t e n s i o n is fixed at some v a l u e , a n d t h e contact angle is z e r o . A n analogy c a n be d r a w n w i t h t h e rise o f w a t e r i n c a p i l l a r y tubes o f d i f f e r i n g r a d i i . I n a p




reservoir c o n s i s t i n g o f s u c h c a p i l l a r y tubes that c o n t a i n w a t e r a n d o i l , w a t e r w i l l b e i m b i b e d most strongly i n t o the smallest radius pores, d i s p l a c i n g any o i l present i n t h e m , u n t i l t h e hydrostatic a n d c a p i l l a r y pressures i n t h e system balance. T h e largest pores w i l l r e t a i n h i g h o i l contents. N o w as w a t e r is i n j e c t e d d u r i n g a secondary r e c o v e r y process, the a p p l i e d w a t e r pressure increases a n d the larger pores w i l l i m b i b e m o r e water, d i s p l a c i n g o i l , w h i c h may b e r e c o v e r e d at p r o d u c i n g w e l l s . T h e r e is a p r a c t i c a l l i m i t t o t h e extent that t h e a p p l i e d pressure c a n b e c h a n g e d b y p u m p i n g w a t e r i n t o a reservoir, h o w e v e r , so that after w a t e r - f l o o d i n g some r e s i d u a l o i l w i l l still b e left i n the f o r m o f o i l ganglia t r a p p e d i n the larger pores w h e r e the viscous forces o f t h e d r i v i n g w a t e r - f l o o d c o u l d n o t c o m p l e t e l y o v e r c o m e the c a p i l l a r y forces h o l d ing the o i l i n place. T h e ratio o f viscous forces t o c a p i l l a r y forces correlates w e l l w i t h r e s i d ual o i l saturation a n d is t e r m e d t h e c a p i l l a r y n u m b e r (N ). O n e f o r m u l a t i o n o f t h e c a p i l l a r y n u m b e r is c

(2)

N = 7]v/y c

w h e r e η a n d υ are the viscosity a n d v e l o c i t y , respectively, o f the d i s p l a c i n g fluid; a n d y is t h e i n t e r f a c i a l t e n s i o n . T h e f u n c t i o n a l f o r m o f t h e c o r r e l a t i o n is i l l u s t r a t e d i n F i g u r e 3 . D u r i n g w a t e r - f l o o d i n g , N is about 10~ , a n d at t h e 6

c

10"

6

10"

5

10"

4

10"

3

10"

2

Capillary Number Figure 3. A generalized capillary number correlation. (Courtesy of K. Taylor, Petroleum Recovery Institute, Calgary.)


1.

SCHRAMM

Basic Principles

9

e n d o f the w a t e r - f l o o d the r e s i d u a l o i l saturation is still a r o u n d 4 5 % . H o w c o u l d a tertiary r e c o v e r y process b e d e s i g n e d so that the r e m a i n i n g o i l c o u l d be r e c o v e r e d ? L o w e r i n g the r e s i d u a l o i l saturation r e q u i r e s i n c r e a s i n g the c a p i l l a r y n u m b e r . T h i s increase c o u l d be d o n e b y r a i s i n g the viscous forces, that is, viscosity a n d v e l o c i t y , b u t i n p r a c t i c e the d e s i r e d o r d e r s - o f - m a g n i t u d e increase w i l l not be a c h i e v e d . B u t , a d d i n g a suitable surfactant a n d cosurfactant to the w a t e r w i l l decrease the i n t e r f a c i a l t e n s i o n f r o m about 30 m N / m b y 4 orders o f m a g n i t u d e a n d t h e r e b y increase the c a p i l l a r y n u m b e r to about 10" .


2

T h e m i c e l l e s present also h e l p to s o l u b i l i z e the released o i l d r o p l e t s ; h e n c e , this process is sometimes r e f e r r e d to as m i c e l l a r flooding. T h e e m u l sions c a n b e f o r m u l a t e d to have m o d e r a t e l y h i g h viscosities that h e l p to achieve a m o r e u n i f o r m d i s p l a c e m e n t front i n the reservoir; this u n i f o r m f r o n t gives i m p r o v e d sweep efficiency. T h u s , a n u m b e r o f factors c a n b e adjusted w h e n u s i n g a m i c r o e m u l s i o n system f o r e n h a n c e d o i l recovery. T h e s e are discussed i n d e t a i l i n C h a p t e r 7. M a k i n g E m u l s i o n s . M u c h o f this c h a p t e r is c o n c e r n e d w i t h e m u l s i o n p r o p e r t i e s a n d stability, a n d as a p r a c t i c a l matter chemists f r e q u e n t l y have to c o n t e n d w i t h a l r e a d y - f o r m e d e m u l s i o n s . N e v e r t h e l e s s , a f e w c o m ments o n h o w e m u l s i o n s m a y b e m a d e are a p p r o p r i a t e . T h e b r e a k i n g o f e m u l s i o n s w i l l be discussed later. E m u l s i o n s o f any significant stability c o n t a i n o i l , water, a n d at least one e m u l s i f y i n g agent. T h e e m u l s i f y i n g agent m a y l o w e r i n t e r f a c i a l t e n s i o n a n d t h e r e b y m a k e it easier to create s m a l l d r o p l e t s . A n o t h e r e m u l s i f y i n g agent may b e n e e d e d to stabilize the s m a l l droplets so that t h e y d o not coalesce to f o r m larger d r o p l e t s , o r e v e n separate out as a b u l k phase. Just a straightfor w a r d casual m i x i n g o f these c o m p o n e n t s s e l d o m , h o w e v e r , p r o d u c e s an e m u l s i o n that persists for any l e n g t h o f t i m e . I n the classical m e t h o d o f e m u l s i o n p r e p a r a t i o n , the e m u l s i f y i n g agent is d i s s o l v e d i n t o the phase i n w h i c h it is most s o l u b l e , after w h i c h the s e c o n d phase is a d d e d , a n d the w h o l e m i x t u r e is v i g o r o u s l y agitated. T h e agitation is c r u c i a l to p r o d u c i n g sufficiently s m a l l d r o p l e t s , a n d f r e q u e n t l y , after an i n i t i a l m i x i n g , a s e c o n d m i x i n g w i t h v e r y h i g h a p p l i e d m e c h a n i c a l shear forces is r e q u i r e d . T h i s latter m i x i n g carrbe p r o v i d e d b y a p r o p e l l e r - s t y l e m i x e r , b u t m o r e c o m m o n l y a c o l l o i d m i l l o r u l t r a s o u n d generator is e m p l o y e d . A m e t h o d r e q u i r i n g m u c h less m e c h a n i c a l energy uses phase i n v e r s i o n (see also the d i s c u s s i o n o f phase i n v e r s i o n t e m p e r a t u r e i n the section " E m u l s i f y i n g A g e n t s " ) . F o r example, i f u l t i m a t e l y a W / O e m u l s i o n is d e s i r e d , t h e n a coarse O / W e m u l s i o n is first p r e p a r e d b y the a d d i t i o n o f m e c h a n i c a l energy, a n d the o i l content is progressively i n c r e a s e d . A t some v o l u m e f r a c t i o n above 6 0 - 7 0 % , the e m u l s i o n w i l l s u d d e n l y i n v e r t a n d p r o d u c e a W / O e m u l s i o n o f m u c h s m a l l e r w a t e r d r o p l e t sizes t h a n w e r e the o i l d r o p l e t s i n the o r i g i n a l O / W e m u l s i o n .


10



Physical Characteristics of Emulsions A p p e a r a n c e . N o t a l l e m u l s i o n s e x h i b i t t h e classical " m i l k y " o p a q u e ness w i t h w h i c h they are u s u a l l y associated. A t r e m e n d o u s range o f appear ances is possible, d e p e n d i n g u p o n the d r o p l e t sizes a n d t h e d i f f e r e n c e i n refractive i n d i c e s b e t w e e n t h e phases. A n e m u l s i o n c a n b e transparent i f e i t h e r t h e refractive i n d e x o f each phase is t h e same, o r alternatively, i f t h e d i s p e r s e d phase is m a d e u p o f droplets that are s u f f i c i e n t l y s m a l l c o m p a r e d with the wavelength of the illuminating light. Thus an O/W microemulsion o f e v e n a c r u d e o i l i n w a t e r may b e transparent. I f t h e droplets are o f t h e o r d e r o f l - μ π ι d i a m e t e r , a d i l u t e O / W e m u l s i o n w i l l take o n a s o m e w h a t m i l k y - b l u e cast; i f t h e droplets are v e r y m u c h larger, the o i l phase w i l l b e c o m e q u i t e d i s t i n g u i s h a b l e a n d apparent. P h y s i c a l l y t h e nature o f the s i m p l e e m u l s i o n types c a n b e d e t e r m i n e d b y m e t h o d s s u c h as • Texture. T h e texture o f an e m u l s i o n f r e q u e n t l y reflects that o f the external phase. T h u s O / W e m u l s i o n s u s u a l l y f e e l w a t e r y o r c r e a m y , a n d W / O e m u l s i o n s f e e l o i l y o r greasy. T h i s d i s t i n c t i o n b e c o m e s less e v i d e n t as the e m u l s i o n viscosity increases, so that a v e r y viscous O / W e m u l s i o n m a y f e e l o i l y . • Mixing. A n e m u l s i o n r e a d i l y mixes w i t h a l i q u i d that is m i s c i ble w i t h the c o n t i n u o u s phase. T h u s , m i l k (O/W) c a n b e d i l u t e d w i t h water, a n d mayonnaise (W/O) c a n b e d i l u t e d w i t h o i l . U s u a l l y , a n e m u l s i o n that retains a u n i f o r m a n d m i l k y appearance w h e n greatly d i l u t e d is m o r e stable t h a n o n e that aggregates u p o n d i l u t i o n (15). • Dyeing.

E m u l s i o n s are most r e a d i l y a n d consistently c o l o r e d

b y dyes s o l u b l e i n t h e c o n t i n u o u s phase. • Conductance. O / W e m u l s i o n s u s u a l l y have a v e r y h i g h spe cific c o n d u c t a n c e , l i k e that o f t h e aqueous phase itself, b u t W / O e m u l s i o n s have a v e r y l o w specific c o n d u c t a n c e . A s i m p l e test apparatus is d e s c r i b e d i n r e f e r e n c e 15. • Inversion.

I f a n e m u l s i o n is v e r y c o n c e n t r a t e d , i t w i l l p r o b a

bly i n v e r t w h e n d i l u t e d w i t h a d d i t i o n a l i n t e r n a l phase. • Fluorescence.

I f t h e o i l phase

fluoresces,

then

fluorescence

m i c r o s c o p y c a n b e u s e d to d e t e r m i n e the e m u l s i o n type as l o n g as t h e d r o p l e t sizes are larger t h a n the microscope's l i m i t o f r e s o l u t i o n (>0.5 μ π ι ) . E m u l s i o n s d o n o t always o c c u r i n t h e i d e a l i z e d f o r m o f droplets o f one phase d i s p e r s e d i n another. T h e o c c u r r e n c e o f m u l t i p l e e m u l s i o n s , o f t h e



1.

SCHRAMM

Basic Principles

11

types O/W/O a n d W / O A V , has already b e e n m e n t i o n e d . P e t r o l e u m e m u l sions m a y also o c c u r w i t h i n another type o f c o l l o i d a l d i s p e r s i o n . F o r e x a m p l e , i n a gas-flooding e n h a n c e d o i l r e c o v e r y process o n e o f t h e ways t o i m p r o v e t h e areal sweep efficiency, that is, to m a x i m i z e t h e a m o u n t o f t h e r e s e r v o i r c o n t a c t e d b y i n j e c t e d fluids, is t o inject t h e gas as p a r t o f a f o a m . H o w e v e r , most s u c h foams are d e s t a b i l i z e d b y contact w i t h e v e n s m a l l amounts o f c r u d e o i l . T h e m e c h a n i s m o f d e s t a b i l i z a t i o n appears (21 ) t o i n v o l v e e m u l s i f i c a t i o n o f the o i l i n t o droplets that are s m a l l e n o u g h to p e r m i t t h e i r passage i n s i d e t h e foam's l a m e l l a r s t r u c t u r e . S u c h e m u l s i f i e d o i l d r o p lets are s h o w n i n F i g u r e 4. O n c e i n s i d e t h e f o a m l a m e l l a e , t h e o i l d r o p l e t s have a d e s t a b i l i z i n g effect o n t h e f o a m b y p e n e t r a t i n g t h r o u g h a n d p o s s i b l y s p r e a d i n g over t h e aqueous-gas interface. T h e l i m i t i n g step, h o w e v e r , is a p p a r e n t l y the e m u l s i f i c a t i o n a n d i m b i b i t i o n o f o i l i n t o t h e f o a m . D r o p l e t Sizes. A s stated p r e v i o u s l y , c o l l o i d a l d r o p l e t s are b e t w e e n about 10" a n d 1 μ π ι i n d i a m e t e r , a n d i n p r a c t i c e , e m u l s i o n droplets are o f t e n larger (e.g., t h e fat droplets i n m i l k ) . I n fact, e m u l s i o n droplets u s u a l l y 3

Figure 4. Photomicrograph of an enhanced oil recovery process foam contain ing emulsified crude-oil droplets. The droplets have traveled within the narrow lamellae to accumulate and sometimes coalesce in the plateau borders of the foam, where they are held preferentially. The presence of such emulsified oil droplets in the foam structure has a destabilizing effect on the foam.



12


have diameters greater t h a n 0.2 μπι a n d m a y b e larger t h a n 50 μ ι η . E m u l sion stability is not necessarily a f u n c t i o n o f d r o p l e t size, a l t h o u g h t h e r e m a y b e a n o p t i m u m size f o r a n i n d i v i d u a l e m u l s i o n type. C h a r a c t e r i z i n g a n e m u l s i o n i n terms o f a g i v e n d r o p l e t size is v e r y c o m m o n b u t g e n e r a l l y i n a p p r o p r i a t e because t h e r e is i n e v i t a b l y a size d i s t r i b u t i o n . T h e size d i s t r i b u t i o n is u s u a l l y r e p r e s e n t e d b y a h i s t o g r a m o f sizes, o r , i f there are suffi cient data, a d i s t r i b u t i o n f u n c t i o n . I n some e m u l s i o n s , a d r o p l e t size d i s t r i b u t i o n that is h e a v i l y w e i g h t e d t o w a r d t h e s m a l l e r sizes w i l l represent t h e most stable e m u l s i o n . I n s u c h cases changes i n the size d i s t r i b u t i o n c u r v e w i t h t i m e y i e l d a measure o f the stability o f the e m u l s i o n s . T h e d r o p l e t size d i s t r i b u t i o n also has a n i m p o r t a n t i n f l u e n c e o n the viscosity. F o r electrostatically o r sterically i n t e r a c t i n g d r o p lets, e m u l s i o n viscosity w i l l b e h i g h e r w h e n droplets are smaller. T h e viscos ity w i l l also b e h i g h e r w h e n the d r o p l e t sizes are relatively h o m o g e n e o u s , that is, w h e n t h e d r o p l e t size d i s t r i b u t i o n is n a r r o w rather t h a n w i d e (4). I f t h e d r o p l e t size is large e n o u g h , t h e n o p t i c a l m i c r o s c o p y c a n b e u s e d to d e t e r m i n e t h e size a n d size d i s t r i b u t i o n . E m u l s i o n s w i t h somewhat s m a l l er d r o p l e t sizes c a n b e c h a r a c t e r i z e d b y u s i n g cryogenic-stage s c a n n i n g e l e c t r o n m i c r o s c o p y . I f t h e e m u l s i o n c o n c e n t r a t i o n is not too h i g h , a n d the droplets are v e r y s m a l l , l i g h t scattering c a n y i e l d d r o p l e t size i n f o r m a t i o n . W h e n a b e a m o f l i g h t enters a n e m u l s i o n , some l i g h t is a b s o r b e d , some is scattered, a n d some is t r a n s m i t t e d . M a n y d i l u t e , fine e m u l s i o n s s h o w a noticeable t u r b i d i t y g i v e n b y I // t

0

=expM)

(3)

w h e r e I is the i n t e n s i t y o f t h e t r a n s m i t t e d b e a m , I is the i n t e n s i t y o f the i n c i d e n t b e a m , τ is t u r b i d i t y , a n d I is t h e l e n g t h o f the p a t h t h r o u g h the s a m p l e . F r o m R a y l e i g h t h e o r y , t h e i n t e n s i t y o f l i g h t scattered f r o m e a c h d r o p l e t d e p e n d s largely o n its size a n d shape a n d o n t h e d i f f e r e n c e i n refractive i n d e x b e t w e e n the d r o p l e t a n d the m e d i u m . F o r a n e m u l s i o n , e a c h s p h e r i c a l d r o p l e t scatters l i g h t h a v i n g a n i n t e n s i t y l at a distance χ f r o m t h e d r o p l e t , a c c o r d i n g to t h e f o l l o w i n g r e l a t i o n s h i p : t

0

d

(4)

I /I ocr /x K* d

0

e

2

w h e r e λ is t h e w a v e l e n g t h o f t h e l i g h t a n d r is t h e d r o p l e t radius. T h e scattering i n t e n s i t y is p r o p o r t i o n a l to l/λ , so b l u e l i g h t ( λ = 4 5 0 n m ) is scattered m u c h m o r e t h a n r e d l i g h t ( λ = 650 n m ) . W i t h i n c i d e n t w h i t e light, a d i l u t e e m u l s i o n o f O . l - 1 - μ π ι size droplets w i l l , therefore, t e n d t o appear b l u e w h e n v i e w e d at right angles t o t h e i n c i d e n t l i g h t b e a m . I f t h e droplets are s m a l l e r t h a n 5 0 n m o r so, the e m u l s i o n w i l l appear to b e transparent. 4


1.

SCHRAMM

Basic Principles

T h e s e approaches

13

to d e t e r m i n i n g d r o p l e t size d i s t r i b u t i o n s are d i s

c u s s e d i n d e t a i l i n C h a p t e r 3.

Conductivity.

Conductivity can be used to distinguish O/W f r o m

W / O e m u l s i o n s b e c a u s e the c o n d u c t i v i t y is v e r y h i g h w h e n t h e aqueous phase is c o n t i n u o u s a n d c o n d u c t i v i t y is v e r y l o w w h e n o i l is t h e c o n t i n u o u s phase. O f the n u m e r o u s equations p r o p o s e d (4) to d e s c r i b e t h e c o n d u c t i v i t y o f e m u l s i o n s (#c ), t w o are c i t e d h e r e f o r i l l u s t r a t i o n . I f t h e c o n d u c t i v i t y o f E

the d i s p e r s e d phase ( K ) is m u c h s m a l l e r t h a n that o f t h e c o n t i n u o u s phase d


(fCc), * C »

*D>

_8KC(2-0)(1-0)

(

5

)

(4 + φ ) ( 4 - φ )

E

w h e r e φ is the dispersed-phase v o l u m e f r a c t i o n . If, o n t h e o t h e r h a n d , t h e c o n d u c t i v i t y o f t h e d i s p e r s e d phase (#c ) is m u c h greater t h a n that o f t h e D

c o n t i n u o u s phase ( K ) , K ΡPB F r r R c

p

R R t Γ T l

2

K

υ V V V W χ

A

R

c o u n t e r i o n charge n u m b e r individual ion-charge numbers

ζ z

{

Greek a , a , a 7 7 7° T

e m p i r i c a l constants i n equations d e s c r i b i n g e m u l s i o n viscosity o i l - w a t e r i n t e r f a c i a l t e n s i o n also u s e d as a t e r m i n the r e p u l s i v e energy expression for s p h e r i c a l d r o p l e t s shear rate surface t e n s i o n surface excess o f surfactant

δ e ζ Ύ]

distance f r o m d r o p l e t surface to S t e r n p l a n e permittivity zeta p o t e n t i a l viscosity

0

s

x

2


1.

SCHRAMM

Basic Principles

47

i n t r i n s i c viscosity

VD

%ed %el

viscosity o f c o n t i n u o u s phase apparent viscosity d i f f e r e n t i a l viscosity r e d u c e d viscosity relative viscosity specific increase i n viscosity


θ

contact angle o f a n o i l - w a t e r interface i n contact w i t h a s o l i d surface

Ι/κ

d o u b l e - l a y e r thickness

Kc

c o n d u c t i v i t y o f c o n t i n u o u s phase c o n d u c t i v i t y o f d i s p e r s e d phase conductivity o f emulsions

«Ό

λ μ ΤΓ

Ε

w a v e l e n g t h o f l i g h t (in l i g h t - s c a t t e r i n g e x p e r i m e n t ) electrophoretic mobility e x p a n d i n g pressure (surface pressure) external fluid density d r o p l e t density charge density

Pi Ρ σ σ° τ

surface charge density turbidity

Τγ

shear stress y i e l d stress

2

Ψ

dispersed-phase v o l u m e f r a c t i o n potential

ω

surface p o t e n t i a l angular v e l o c i t y

Φ

Acknowledgments I t h a n k E d d y Isaacs ( A l b e r t a R e s e a r c h C o u n c i l ) a n d K a r i n M a n n h a r d t (Pe t r o l e u m R e c o v e r y Institute) f o r v e r y h e l p f u l discussions a n d suggestions r e g a r d i n g the m a n u s c r i p t . V a l u a b l e suggestions o f f e r e d b y the external ref erees are also gratefully a c k n o w l e d g e d .

References 1. Martinez, A . R. In The Future of Heavy Crude and Tar Sands; Meyer, R. F . ; Wynn, J. C . ; Olson, J. C . , Eds.; U N I T A R : N e w York, 1982; pp xvii-xviii. 2. Danyluk, M.; Galbraith, B.; Omana, R. In The Future of Heavy Crude and Tar Sands; Meyer, R. F.; Wynn, J. C . ; Olson, J. C . , Eds.; U N I T A R : New York, 1982; pp 3-6.

American Chemical Society Library 1155 16th St., N.W. In Emulsions; Schramm, L.; Washington, D.C. 20036

Advances in Chemistry; American Chemical Society: Washington, DC, 1992.


48

EMULSIONS IN THE PETROLEUM INDUSTRY

3. Khayan, M . In The Future of Heavy Crude and Tar Sands; Meyer, R. F.; Wynn, J. C . ; Olson, J. C . , Eds.; U N I T A R : New York, 1982; pp 7-11. 4. Becher, P. Emulsions: Theory and Practice, 2nd E d . ; A C S Monograph Series 162; American Chemical Society: Washington, D C , 1966. 5. Sumner, C . G . Clayton's The Theory of Emulsions and Their Technical Treat ment, 5th E d . ; Blakiston: New York, 1954. 6. Encyclopedia of Emulsion Technology; Becher, P., E d . ; Dekker: N e w York, 1983; V o l . 1. 7. Encyclopedia of Emulsion Technology; Becher, P., E d . ; Dekker: N e w York, 1985; V o l . 2. 8. Encyclopedia of Emulsion Technology; Becher, P., E d . ; Dekker: N e w York, 1988; V o l . 3. 9. Lissant, Κ. J. Demulsification: Industrial Applications; Surfactant Science Se ries 13; Dekker: N e w York, 1983; V o l . 13. 10. Micellization, Solubilization, and Microemulsions; Mittal, K . L . , E d . ; Plenum: New York, 1977; Vols. 1 and 2. 11. Macro- and Microemulsions; Shah, D . O., E d . ; A C S Symposium Series 272; American Chemical Society: Washington, D C , 1985. 12. Osipow, L . I. Surface Chemistry Theory and Industrial Applications; Reinhold: New York, 1962. 13. Ross, S.; Morrison, I. D . Colloidal Systems and Interfaces; Wiley: New York, 1988. 14. Colloid Science; Kruyt, H. R., E d . ; Elsevier: Amsterdam, Netherlands, 1952; V o l . 1. 15. Griffin, W . C . In Kirk-Othmer Encyclopedia of Chemical Technology, 2nd ed.; Interscience: New York, 1965; V o l . 8, pp 117-154. 16. Shaw, D . J. Introduction to Colloid and Surface Chemistry, 3rd ed.; Butterworth’s: London, 1981. 17. Microemulsions Theory and Practice; Prince, L . M., E d . ; Academic Press: New York, 1977. 18. Neogi, P. In Microemulsions: Structure and Dynamics; Friberg, S. E . ; Bothorel, P., Eds.; CRC Press: Boca Raton, FL, 1987; pp 197-212. 19. Poettmann, F . H . In Improved Oil Recovery; Interstate Compact Commission: Oklahoma City, O K , 1983; pp 173-250. 20. Bansal, V. K.; Shah, D . O. In Microemulsions: Theory and Practice; Prince, L . M., E d . ; Academic Press: New York, 1977; pp 149-173. 21. Schramm, L . L.; Novosad, J. J. Colloids Surf. 1990, 46, 21-43. 22. Whorlow, R. W . Rheological Techniques; Wiley: New York, 1980. 23. Van Wazer, J. R.; Lyons, J. W.; K i m , K. Y.; Colwell, R. E . Viscosity and Flow Measurement; Wiley: New York, 1963. 24. Fredrickson, A . G . Principles and Applications of Rheology; Prentice-Hall: E n glewood Cliffs, N J , 1964. 25. Schramm, L . L . J. Can. Pet. Technol. 1989, 28, 73-80. 26. Malhotra, A . K . ; Wasan, D . T. In Thin Liquid Films; Ivanov, I. B., E d . ; Surfac tant Science Series 29; Dekker: New York, 1988; pp 829-890. 27. Harkins, W . D . ; Alexander, A . E . In Physical Methods of Organic Chemistry; Weissberger, Α., E d . ; Interscience: New York, 1959; pp 757-814. 28. Padday, J. F . In Surface and Colloid Science; Matijevic, E . , E d . ; WileyInterscience: N e w York, 1969; V o l . 1, pp 101-149. 29. Miller, C . Α.; Neogi, P. Interfacial Phenomena Equilibrium and Dynamic Ef fects; Dekker: N e w York, 1985.


SCHRAMM

30.

Cayias, J. L.; Schechter, R. S.; Wade, W . H. In Adsorption at Interfaces; Mittal, K. L . , E d . ; A C S Symposium Series 8; American Chemical Society: Washington, D C , 1975; pp 234-247. Adamson, A . W . Physical Chemistry of Surfaces, 4th E d . ; Wiley: N e w York, 1982. Lake, L . W . Enhanced Oil Recovery; Prentice-Hall: Englewood Cliffs, N J , 1989. Rosen, M . J. Surfactants and Interfacial Phenomena, 2nd ed.; Wiley: N e w York, 1989. Industrial Applications of Surfactants; Karsa, D . R., E d . ; Royal Society of Chemistry: London, 1987. Anionic Surfactants: Physical Chemistry of Surfactant Action; Lucassen-Reynders, E . H., E d . ; Dekker: New York, 1981. Ross, S. J. Phys. Colloid Chem. 1950, 54, 429-436. Currie, C . C . In Foams; Bikerman, J. J., E d . ; Reinhold: N e w York, 1953; pp 297-329. Takamura, K . Can. J. Chem. Eng. 1982, 60, 538-545. Takamura, K . ; Chow, R. S. J. Can. Pet. Technol. 1983, 22, 22-30. Schramm, L . L.; Smith, R. G.; Stone, J. A . AOSTRA J. Res. 1984, 1, 5-14. Schramm, L . L.; Smith, R. G . Colloids Surf. 1985, 14, 67-85. Schramm, L . L.; Smith, R. G . Can. J. Chem. Eng. 1987, 65, 799-811. Schramm, L . L.; Smith, R. G . AOSTRA J. Res. 1989, 5, 87-107. Smith, R. G . ; Schramm, L . L . Fuel Proc. Technol. 1989, 23, 215-231. Verwey, E . J. W . ; Overbeek, J. T h . G . Theory of the Stability of Lyophobic Colloids; Elsevier: New York, 1948. Hunter, R. J. Zeta Potential in Colloid Science; Academic Press: N e w York, 1981. James, A . M . In Surface and Colloid Science; Good, R. J.; Stromberg, R. R., Eds.; Plenum: New York, 1979; V o l . 11, pp 121-186. Riddick, T. M . Control of Stability Through Zeta Potential; Zeta Meter: N e w York, 1968. O’Brien; White, L . R. J. Chem. Soc. Faraday 2 1978, 74, 1607-1626. Schramm, L . L . ; Smith, R. G. Canadian Patent 1,265,463, February 6, 1990. van Olphen, H . An Introduction to Clay Colloid Chemistry, 2nd E d . ; Wiley: New York, 1977. Cavallo, J. L.; Chang, D . L. Chem. Eng. Prog. 1990; 86, 54-59. The HLB System; I C I United States, Inc. (now I C I Americas, Inc.): Wilmington, D E , 1976. McCutcheon’s Emulsifiers and Detergents; M C Publishing C o . : G l e n Rock, N J , 1990; Vol. 1. Ross, S.; Chen, E . S.; Becher, P.; Ranauto, H . J. J. Phys. Chem. 1959, 63, 1681. Shinoda, K . ; Saito, H. J. Colloid Interface Sci. 1969, 30, 258-263. Cairns, R. J. R.; Grist, D . M.; Neustadter, E . L . In Theory and Practice of Emulsion Technology; Smith, A . L., E d . ; Academic Press: N e w York, 1976; pp 135-151. Jones, T. J.; Neustadter, E . L.; Whittingham, K . P. J. Can. Pet. Technol. 1978, 17, 100-108. Schramm, L . L.; Kwak, J. C . T. J. Can. Pet. Technol. 1988, 27, 26-35. Schramm, L . L . ; Hackman, L . P., unpublished results.

31. 32. 33. 34. 35.


49

1.

36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57.

58. 59. 60.

Basic

Principles

R E C E I V E D for review December 18, 1990. A C C E P T E D revised manuscript A p r i l 26, 1991.


Petroleum Emulsions - Advances in Chemistry (ACS Publications)

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