Emulsions Fundamentals and Applications in the Petroleum Industry

10 Breaking Produced-Fluid and Process-Stream Emulsions Downloaded by UNIV OF ARIZONA on December 7, 2012 | http://pubs.acs.org Publication Date: May 5, 1992 | doi: 10.1021/ba-1992-0231.ch010

Gerhard Leopold Department of Energy, Mines, and Resources, C A N M E T , Fuel Processing Laboratory, P.O. Bag 1280, Devon, Alberta, Canada, TOC 1E0

This chapter will briefly review the nature and the consequential sources of oil-field emulsions encountered in the handling of producedfluids recovered at a wellhead and subsequently processed (i.e., "broken") at central treatment facilities. The principal factors and agents commonly employed in the separation of both the oil and the water phases found in these produced-fluid streams will be discussed. Subsequently, this chapter will describe sampling and testing techniques that assist in characterizing a process stream's composition and thus in evaluating the effectiveness of a particular separation process. Finally, the major components of a typical oil-field emulsiontreatment facility will be described. Selection and design criteria of appropriate separation equipment will also be presented.

Source and Nature of Process-Stream Emulsions A n e m u l s i o n is a system c o n s i s t i n g o f a l i q u i d d i s p e r s e d as d r o p l e t s i n a s e c o n d i m m i s c i b l e l i q u i d , o f t e n s t a b i l i z e d b y an e m u l s i f y i n g agent. I n t h e o i l field, the t w o basic types o f e m u l s i o n s are w a t e r - i n - o i l a n d o i l - i n - w a t e r ; o i l i n - w a t e r e m u l s i o n s are o f t e n t e r m e d reverse e m u l s i o n s . M o r e t h a n 9 5 % o f the c r u d e - o i l e m u l s i o n s f o r m e d i n t h e o i l field are o f the w a t e r - i n - o i l t y p e . N o n e t h e l e s s , o i l - i n - w a t e r e m u l s i o n s are r e c e i v i n g g r o w i n g interest i n p o l l u t i o n a b a t e m e n t as they are r e a d i l y m i s c i b l e w i t h water. P e t r o l e u m e m u l s i o n s vary f r o m o n e o i l field to another s i m p l y because c r u d e o i l differs a c c o r d i n g to its geological age, c h e m i c a l c o m p o s i t i o n , a n d associated i m p u r i t i e s . F u r t h e r m o r e , t h e p r o d u c e d w a t e r s c h e m i c a l a n d p h y s i c a l p r o p e r t i e s , w h i c h also are specific to i n d i v i d u a l reservoirs, w i l l affect e m u l s i o n characteristics as w e l l . 0065-2393/92/0231-0341 $012.00/0 © 1992 American Chemical Society

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

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Downloaded by UNIV OF ARIZONA on December 7, 2012 | http://pubs.acs.org Publication Date: May 5, 1992 | doi: 10.1021/ba-1992-0231.ch010

Croup Gathering Systems. T h e g a t h e r i n g system i n p e t r o l e u m p r o d u c t i o n operations consists p r i m a r i l y o f the p i p e s , valves, a n d fittings necessary to c o n n e c t t h e p r o d u c t i o n w e l l h e a d to t h e separation e q u i p m e n t . T h e c o n f i g u r a t i o n o f the g a t h e r i n g system t y p i c a l l y entails several flow lines c o n n e c t i n g the i n d i v i d u a l w e l l s to a g r o u p h e a d e r o r test h e a d e r system as d i c t a t e d b y t h e size a n d layout o f t h e p a r t i c u l a r o i l field. C o n s e q u e n t l y , t h e nature o f t h e c o m p o s i t e e m u l s i o n sent to t h e treatment facilities is deter m i n e d b y t h e c o m b i n a t i o n o f p r o d u c e d fluids f r o m i n d i v i d u a l w e l l s . T h e c o m b i n a t i o n o f several w e l l s ' p r o d u c t i o n i n a p a r t i c u l a r o i l field may gener ate a n average e m u l s i o n that c a n b e m o r e manageably t r e a t e d t h a n p r o d u c t i o n f r o m a n i n d i v i d u a l w e l l . F o r e x a m p l e , excessive w a t e r p r o d u c t i o n f r o m a single w e l l is m o r e effectively treated i n a g r o u p heater treater t h a n i f s p e c i a l equipment for water removal were required.

Trucked versus Pipelined Emulsions. O v e r the years transpor tation o f p r o d u c e d l i q u i d s has e v o l v e d f r o m t h e use o f w o o d e n barrels filled at t h e w e l l h e a d to a system o f p i p e l i n e s a n d t r u c k s . I n a s m u c h as i t is u s u a l l y m u c h c h e a p e r to use p i p e l i n e s t h a n t r u c k s , t h e s e l e c t i o n o f e i t h e r transpor t a t i o n m o d e is generally not d i c t a t e d b y e c o n o m i c s alone. S o m e o f the major advantages o f u s i n g p i p e l i n e s are 1.

economy

2. r e l i a b i l i t y (e.g., i n t h e face o f w e a t h e r a n d b r e a k d o w n s ) 3. c o n t r o l (i.e., variety o f flow rates) 4. c o n t i n u i t y B e c a u s e o f t h e i r h i g h viscosities a n d densities (i.e., l o w A P I gravities ), heavy oils a n d t h e i r e m u l s i o n s are c u r r e n t l y t r a n s p o r t e d m a i n l y b y t r u c k s . T h e major p r o b l e m s i n p i p e l i n i n g heavy c r u d e oils are associated w i t h p o u r p o i n t (i.e., wax c r y s t a l l i z a t i o n p r o b l e m s ) a n d viscosity (i.e., flow p r o b l e m s ) . 1

Several t e c h n i q u e s are e m p l o y e d b y t h e i n d u s t r y to o v e r c o m e these p r o b l e m s ; t h e t w o most c o m m o n l y u s e d methods are t h e a p p l i c a t i o n o f heat a n d d i l u t i o n w i t h a solvent (i.e., l o w - v i s c o s i t y h y d r o c a r b o n s s u c h as c o n d e n sate, n a t u r a l gasoline, a n d , most o f t e n , naphtha). B o t h m e t h o d s serve t o r e d u c e t h e t r a n s p o r t e d c r u d e oil's viscosity; d i l u t i o n w i l l also r e d u c e t h e h e a v y - o i l mixture's p o u r p o i n t . A n innovative t e c h n i q u e i n v o l v i n g t h e p r e p a r a t i o n o f a l o w e r - v i s c o s i t y unstable s l u r r y - e m u l s i o n system b y m i x i n g w a t e r w i t h t h e o i l as a means o f c o n v e y i n g c r u d e o i l has y e t to b e p r o v e n o n a c o m m e r c i a l scale. T h e t e c h n i c a l p r o b l e m s a n d issues l i m i t i n g t h e a p p l i c a t i o n o f this t e c h n i q u e (analo gous to c r u d e - o i l e m u l s i o n p i p e l i n i n g ) are t o sustain t h e t w o i m m i s c i b l e l i q u i d s i n a stable e m u l s i o n d u r i n g transport a n d to d e s t a b i l i z e t h e e m u l s i o n APÏ

1

gravity is defined in the Glossary.


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o n c e i t arrives at the d e l i v e r y p o i n t (i.e., t o separate w a t e r f r o m the o i l ) . T h e s e l e c t i o n o f a n effective p a i r o f e m u l s i f y i n g a n d d e m u l s i f y i n g agents is c r u c i a l t o t h e m e t h o d ' s success.


T r u c k i n g is a m o r e e c o n o m i c a n d expedient m e t h o d o f t r a n s p o r t i n g p r o d u c e d e m u l s i o n s to p r o d u c t i o n t r e a t m e n t facilities, p a r t i c u l a r l y f o r heavy c r u d e oils that are d i f f i c u l t to p u m p . H o w e v e r , over e x t e n d e d distances (i.e., t r a v e l i n g t i m e i n excess o f 1 h ) , free-water s e t t l i n g c a n b e q u i t e p r o n o u n c e d w i t h i n a t a n k e r t r u c k . A g i t a t i o n d u e t o t r a v e l o v e r r o u g h roads m a y also p r o m o t e some degree o f coalescence. Oil R e c o v e r y Scheme. T h e type o f o i l r e c o v e r y process e m p l o y e d influences t h e nature o f the e m u l s i o n e v e n t u a l l y p r o d u c e d f r o m a specific s u b t e r r a n e a n zone o r reservoir. F o r o i l - b e a r i n g f o r m a t i o n s u n d e r p r i m a r y recovery, t h e p r o d u c e d fluids are w i t h d r a w n f r o m a specific z o n e o r reser v o i r a n d l i f t e d t o t h e surface b y e i t h e r n a t u r a l (reservoir pressure) o r artifi c i a l ( b o t t o m h o l e p u m p o r gas) means. T h e r e s u l t i n g e m u l s i o n is s i m p l y a c o m b i n a t i o n o f t h e p e t r o l e u m a n d any associated w a t e r a n d gas i n t h e reservoir. N a t u r a l l y o c c u r r i n g e m u l s i f y i n g agents are u s u a l l y present i n suf ficient quantities t o stabilize t h e e m u l s i o n . F u r t h e r m o r e , t h e agitation aris i n g f r o m the t u r b u l e n t flow o f the o i l - w a t e r m i x t u r e t h r o u g h the w e l l casing, t u b i n g , d o w n h o l e p u m p ( i f r e q u i r e d ) , a n d surface e q u i p m e n t is u s u a l l y a m p l e to p r o m o t e e m u l s i f i c a t i o n . ( T h e terms " d o w n h o l e " a n d " b o t t o m h o l e " r e f e r t o the lowest d e p t h , n o r m a l l y the p r o d u c i n g z o n e , o f a n o i l w e l l . ) T o i m p r o v e u l t i m a t e o i l r e c o v e r y f r o m some reservoirs, e i t h e r w a t e r o r (natural) gas i n j e c t i o n is u s e d t o displace the o i l t o the p r o d u c i n g w e l l b o r e . S u c h processes are c a t e g o r i z e d as secondary recovery. T h e i n t r o d u c t i o n o f an i n j e c t e d fluid t o t h e r e s e r v o i r adds a n e w constituent t o t h e p r o d u c e d e m u l s i o n . C o n s e q u e n t l y , t h e source a n d nature o f t h e selected i n j e c t i o n fluid m u s t b e closely s c r u t i n i z e d , n o t o n l y f o r its effect o n t h e r e c o v e r y process, b u t also f o r its i m p a c t o n t h e nature a n d stability o f the p r o d u c e d e m u l s i o n . ( F o r e x a m p l e , t h e c o m p a t i b i l i t y o f the i n j e c t e d w a t e r w i t h t h e connate w a t e r present i n the reservoir must b e e n s u r e d to p r e v e n t p r e c i p i t a t i o n that w o u l d result i n f o r m a t i o n p l u g g i n g . ) T e r t i a r y o r e n h a n c e d o i l r e c o v e r y ( E O R ) incorporates a v a r i e t y o f t e c h n i q u e s i n v o l v i n g m o r e elaborate i n j e c t i o n schemes t h a n e m p l o y e d i n secon dary recovery. T h e t r e a t m e n t o f E O R - p r o d u c e d e m u l s i o n s m u s t b e a p p r o a c h e d i n d e p e n d e n t l y f r o m any p r i m a r y o r secondary p r o d u c t i o n f r o m the same field o r reservoir. S t a n d a r d d e m u l s i f i e r s a n d t r e a t m e n t m e t h o d s u s e d d u r i n g p r i m a r y a n d secondary recovery operations m a y n o t h a n d l e E O R produced emulsions. Specifically, E O R activity c a n b e classified i n t o three major types: (1) c h e m i c a l , (2) m i s c i b l e d i s p l a c e m e n t , a n d (3) t h e r m a l . T h e first category i n c l u d e s the i n j e c t i o n o f surfactants ( m i c e l l a r ) , p o l y m e r s , alkaline (caustic), a n d c a r b o n d i o x i d e . I n m i s c i b l e d i s p l a c e m e n t , a gas o r l i q u i d h y d r o c a r b o n is i n j e c t e d i n t o the reservoir w h e r e i t b e c o m e s m i s c i b l e w i t h the h y d r o c a r b o n s


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INDUSTRY

i n d i g e n o u s to the reservoir. T h e t h e r m a l category i n c l u d e s a l l processes that r e l y o n the a d d i t i o n o f heat to the reservoir to l o w e r the viscosity o f h i g h density c r u d e oils. A m o n g the m o r e p o p u l a r t h e r m a l r e c o v e r y processes are steam i n j e c t i o n , hot-water flooding, a n d i n situ c o m b u s t i o n .


T h e i n t r o d u c t i o n o f heat to the r e s e r v o i r affects the p r o p e r t i e s o f the reservoir fluids (e.g., l o w e r i n g o i l viscosity). I n the extreme case o f fire flooding, w h e r e c o m b u s t i o n temperatures o f 480 °C (900 ° F ) can be attained, thermal cracking and generation of combustion products can introduce new constituents to the p r o d u c e d e m u l s i o n . U n d e r c e r t a i n c o n d i t i o n s o f steam i n j e c t i o n , m i l d e r forms o f t h e r m a l c r a c k i n g o f i n situ heavy c r u d e oils are also possible. T h u s the e m u l s i o n s p r o d u c e d f r o m a p a r t i c u l a r r e s e r v o i r u n d e r p r i m a r y a n d secondary r e c o v e r y m a y b e p h y s i c a l l y a n d c h e m i c a l l y dis t i n c t f r o m t h e r m a l l y r e c o v e r e d fluids. C h a n g e s i n the nature o f not o n l y the o i l a n d w a t e r b u t also the e m u l s i f y i n g agents (i.e., n a t u r a l l y o c c u r r i n g surfactants) result d u r i n g the t h e r m a l r e c o v e r y process.

Co-mingled Production. F o r e c o n o m i c reasons, specific w e l l bores are sometimes c o m p l e t e d to p r o d u c e f r o m m o r e t h a n one o i l - b e a r i n g z o n e simultaneously. T h i s system is t e r m e d c o - m i n g l e d p r o d u c t i o n . T h e c o m p a t i b i l i t y o f the c o - m i n g l e d p r o d u c e d fluids must b e deter m i n e d b e f o r e i n i t i a t i n g s u c h an o p e r a t i o n . C h e m i c a l c o m p a t i b i l i t y o f the p r o d u c e d waters must b e c o n f i r m e d . O t h e r w i s e , the f o r m a t i o n o f solids (precipitates) c o u l d result i n o p e r a t i o n a l p r o b l e m s s u c h as p l u g g i n g , as w e l l as treating d i f f i c u l t i e s .

Agents Employed in Emulsion Treatment Chemicals. C h e m i c a l t r e a t m e n t o f e m u l s i o n s requires the d i s p e r s i o n o f a c h e m i c a l d e m u l s i f i e r , o r e m u l s i o n breaker. D e m u l s i f i e r s are sur face-active agents c o m p r i s i n g relatively h i g h - m o l e c u l a r - w e i g h t p o l y m e r s . W h e n a d d e d to an e m u l s i o n , t h e y migrate to the o i l - w a t e r interface a n d r u p t u r e the film, o r at least w e a k e n it sufficiently f o r the e m u l s i f y i n g agent to b e d i s p e r s e d b a c k i n t o the o i l a n d for droplets o f the d i s p e r s e d phase to attract, c o l l i d e , a n d coalesce. T h e r e m a i n i n g step is to b r i n g these larger droplets i n t o contact w i t h o u t excessive agitation, w h i c h m i g h t redisperse the droplets. Several factors affect d e m u l s i f i e r p e r f o r m a n c e : t e m p e r a t u r e , p H , a n d the nature o f the aqueous-phase salt. I n most cases, an increase i n t e m p e r a ture results i n a decrease i n e m u l s i o n stability. C o n s e q u e n t l y , f o r a p a r t i c u l a r e m u l s i o n , less d e m u l s i f i e r is r e q u i r e d at h i g h e r t r e a t i n g temperatures to effect the same degree o f t r e a t m e n t . Studies (1 ) o n the effect o f p H o n the i n s t a b i l i t y o f c r u d e - o i l - w a t e r e m u l s i o n s have s h o w n that a p H o f 10.5 p r o d u c e d the least stable e m u l s i o n s . F u r t h e r m o r e , basic p H p r o d u c e d o i l - i n w a t e r e m u l s i o n s a n d a c i d i c p H generated w a t e r - i n - o i l e m u l s i o n s .


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S e l e c t i o n o f a suitable c h e m i c a l e m u l s i o n b r e a k e r a n d dosage is c r u c i a l . A p a r t i c u l a r d e m u l s i f i e r m a y b e effective a n d efficient f o r one e m u l s i o n yet e n t i r e l y unsatisfactory for another. C o n t e m p o r a r y d e m u l s i f i e r s are f o r m u l a t e d w i t h p o l y m e r i c chains o f ethylene a n d p r o p y l e n e oxides o f a l c o h o l , alkyl p h e n o l s , a m i n o c o m p o u n d s , a n d resinous materials that have h y d r o x y a c c e p t o r groups. E a c h o f these p o l y m e r s is c a r e f u l l y f o r m u l a t e d to y i e l d a m o l e c u l e w i t h a p a r t i c u l a r affinity for water. D e m u l s i f i e r dosage is also i m p o r t a n t ; excessive d e m u l s i f i e r a d d i t i o n c a n i n h i b i t the efficiency o f e m u l sion breakdown. D e m u l s i f i e r s are v e r y s i m i l a r to emulsifiers because b o t h are surfactant i n nature. C o n s e q u e n t l y , the action o f the d e m u l s i f i e r i n e m u l s i o n b r e a k i n g is to " u n l o c k " the effect o f the e m u l s i f y i n g agent(s) present. T h i s u n l o c k i n g is a c c o m p l i s h e d i n t h r e e f u n d a m e n t a l steps (2): flocculation, coalescence, a n d solids w e t t i n g . Flocculation. T h e first action o f the d e m u l s i f i e r o n an e m u l s i o n i n volves a j o i n i n g t o g e t h e r o r flocculation o f the s m a l l w a t e r d r o p l e t s . W h e n m a g n i f i e d , the flocks take o n the appearance o f b u n c h e s o f fish eggs. I f the e m u l s i f i e r film s u r r o u n d i n g the w a t e r d r o p l e t is v e r y weak, it w i l l b r e a k u n d e r this flocculation f o r c e a n d coalescence w i l l take p l a c e w i t h o u t f u r t h e r c h e m i c a l action. B r i g h t o i l is an i n d i c a t o r o f g o o d flocculation. I n most cases, h o w e v e r , the film remains intact, a n d therefore, a d d i t i o n a l t r e a t m e n t is r e q u i r e d . 2

Coalescence. T h e r u p t u r i n g o f the e m u l s i f i e r film a n d the u n i t i n g o f water droplets is d e f i n e d as coalescence. O n c e coalescence begins, the water droplets g r o w large e n o u g h to settle out. G o o d coalescence is c h a r a c t e r i z e d b y a d i s t i n c t w a t e r phase. Solids Wetting. I n most c r u d e o i l , solids s u c h as i r o n sulfide, silt, clay, d r i l l i n g m u d solids, a n d p a r a f f i n c o m p l i c a t e the d e m u l s i f i c a t i o n process. O f t e n s u c h solids are the p r i m a r y s t a b i l i z i n g m a t e r i a l , a n d t h e i r r e m o v a l is a l l that is necessary to achieve satisfactory t r e a t m e n t . T o r e m o v e solids f r o m the interface, they c a n e i t h e r be d i s p e r s e d i n the o i l o r w a t e r - w e t t e d a n d r e m o v e d w i t h the water.

Agitation. T h e effectiveness o f any d e m u l s i f i e r a d d e d to a t r e a t m e n t system is d i r e c t l y d e p e n d e n t u p o n its m a k i n g o p t i m u m contact w i t h the e m u l s i o n . T h e r e f o r e , the e m u l s i o n must b e sufficiently agitated after the c h e m i c a l d e m u l s i f i e r has b e e n a d d e d . I n c r e a s e d m i l d agitation, s u c h as i n flow lines a n d i n settling tanks, is b e n e f i c i a l i n p r o m o t i n g coalescence. R e The term "bright oil" reiers to the shiny color that is characteristic of treated oil (2). Further discussion on the subject of oil brightness is presented in the subsection "Oil Color" in the section "Interpreting Results".

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e m u l s i f i c a t i o n m a y o c c u r i f an e m u l s i o n is agitated severely o n c e i t has b r o k e n i n t o w a t e r a n d o i l . T h i s sort o f agitation m a y o c c u r i n gas separators, p u m p s , o r o t h e r locations i n t h e system.


Gravity. S e t t l i n g is the s i m p l e s t a n d o n e o f the oldest t e c h n i q u e s to separate t w o i m m i s c i b l e phases. C o n s e q u e n t l y , s e t t l i n g is a basic c o m p o n e n t i n a l l t r e a t m e n t p r o c e d u r e s . T h e t r e a t m e n t vessel s h o u l d b e d e s i g n e d to ensure sufficient t i m e f o r q u i e t s e t t l i n g o f a l l associated w a t e r f r o m t h e o i l phase. Energy. Thermal. T h e a d d i t i o n o f heat p r o m o t e s t h e t r e a t m e n t process. F i r s t , i t r e d u c e s t h e viscosity o f t h e o i l . T h i s effect is especially i n s t r u m e n t a l i n t h e h a n d l i n g a n d t r e a t m e n t o f heavy c r u d e oils o r b i t u m e n e m u l s i o n s . S e c o n d , i t weakens o r r u p t u r e s the film b e t w e e n t h e o i l a n d w a t e r d r o p l e t s b y e x p a n d i n g t h e w a t e r present. L a s t , heat increases the d i f f e r e n c e i n densities o f the fluids a n d t h e r e b y tends to r e d u c e t h e s e t t l i n g time. H e a t , i n effect, accelerates the t r e a t i n g process. C o n s e q u e n t l y , its use can h e l p t o r e d u c e t h e r e q u i r e d size o f t h e t r e a t m e n t vessel. T h e r e is, h o w e v e r , a n u p p e r l i m i t t o h o w m u c h heat c a n b e a d d e d to a system because, at h i g h e r t e m p e r a t u r e s , l i g h t ends (that is, t h e m o r e v o l a t i l e h y d r o c a r b o n fractions) i n the o i l m a y v a p o r i z e . U n l e s s these l i g h t e r ends are c o n s e r v e d , b o t h t h e t r e a t e d oil's v o l u m e a n d its A P I gravity w i l l b e r e d u c e d (i.e., its d e n s i t y w i l l b e increased). T h e e c o n o m i c trade-offs o f l o n g e r t r e a t i n g t i m e , h e a t i n g costs, a n d u l t i m a t e o i l - p r o d u c t sales p r i c e cannot b e i g n o r e d . Mechanical. V a r i o u s m e c h a n i c a l devices are e m p l o y e d to s u p p l e m e n t t h e p e r f o r m a n c e o f the t r e a t m e n t vessel(s) i n t h e b r e a k i n g o f o i l - f i e l d p r o d u c e d e m u l s i o n s . T h e s e i n c l u d e , b u t are n o t l i m i t e d t o , f r e e - w a t e r k n o c k o u t s ( F W K O ) , gas separators, s e t t l i n g tanks, a n d g u n b a r r e l s . F r e e w a t e r k n o c k o u t systems are g e n e r a l l y u s e d i n c o n n e c t i o n w i t h h i g h w a t e r - t o o i l ratio p r o d u c t i o n ; separation o f gas m a y also o c c u r i n t h e u p p e r s e c t i o n ( F i g u r e 1). G a s separators, e i t h e r h o r i z o n t a l o r v e r t i c a l i n c o n f i g u r a t i o n , p r o v i d e t r e m e n d o u s agitation p o t e n t i a l , p r i n c i p a l l y t h r o u g h t h e t u r b u l e n t e v o l u t i o n o f the associated gas f r o m t h e p r o d u c e d l i q u i d s . W i t h o u t t h e efficient r e m o v a l o f gas i n these vessels, u n w a n t e d ( a n d u n c o n t r o l l a b l e ) agitation i n t h e d o w n s t r e a m t r e a t m e n t vessels m a y result. S e t t l i n g tanks are f u n d a m e n t a l l y s i m p l e i n t h e i r p r i n c i p l e o f o p e r a t i o n . T h e rate o f w a t e r d r o p o u t is n o t as c r u c i a l h e r e as w i t h t r e a t m e n t vessels because the i n j e c t e d chemical(s) m a y c o n t i n u e to operate o v e r a n extensive t i m e p e r i o d (days versus h o u r s ) . T h e w a t e r - o i l interface is f o u n d closer to the b o t t o m o f t h e tank. G u n barrels are s i m i l a r to s e t t l i n g tanks i n that t h e y c o m m o n l y operate at a t m o s p h e r i c pressure ( F i g u r e 2). T h e s p e e d o f w a t e r d r o p o u t is g e n e r a l l y


LEOPOLD


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In Emulsions; Schramm, Washington, D.C.L.; 20036 Advances in Chemistry; American Chemical Society: Washington, DC, 1992.

347

348


Gas outlet

Gas

Gas separating chamber Well production inlet I—^>

-«

I


Weir box Oil outlet

Adjustable interface nipple

Oil settling section

Water wash section Water outlet

Spreader Figure 2. Typical gun barrel settling tank with internal flume. (Reproduced with permission from reference 3. Copyright 1986 Gulf Publishing Company.)

not t o o i m p o r t a n t as g u n barrels u s u a l l y have a h i g h v o l u m e - t o - t h r o u g h p u t ratio. A s w i t h s e t t l i n g tanks, t h e c h e m i c a l m a y c o n t i n u e a c t i n g o v e r a l o n g t i m e , a n d t h e interface n e e d n o t b e c l e a n . Electrical. E l e c t r i c i t y is f r e q u e n t l y u s e d to s u p p l e m e n t ( a n d some times replace) heat as a n a i d t o the t r e a t i n g process. F u r t h e r m o r e , w h e r e e l e c t r i c i t y is m u c h c h e a p e r t h a n most o t h e r energy sources, e l e c t r i c a l l y i n d u c e d coalescence t e c h n i q u e s are g a i n i n g p r o m i n e n c e . T h e y are p a r t i c u l a r l y valuable w h e r e space is o f p r i m e i m p o r t a n c e because t h e use o f elec t r i c i t y accelerates t h e settling process e v e n m o r e t h a n heat a n d allows the use o f a s m a l l e r vessel.


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Testing Process-Stream Emulsions Sampling Process Streams.

T h e most c r i t i c a l step i n testing p r o

cess-stream e m u l s i o n s is to p r o c u r e a representative s a m p l e f r o m the total p r o d u c e d fluids. T e s t results w i l l otherwise b e meaningless. A g o o d s a m p l e t h e r e f o r e must be (2): • representative o f the system •

composite


• consistent w i t h the p r o d u c e d fluids to b e treated • free o f i n j e c t e d c h e m i c a l s • free o f c o n t a m i n a n t s •

stable

• 4 0 - 5 0 % water, i f possible • consistently obtainable G e n e r a l l y , a g o o d p l a c e to c o l l e c t a s a m p l e is o f f the m a i n flow l i n e i n t o the system, b e f o r e c h e m i c a l is a d d e d . I f there is n o r e a d i l y available s a m p l i n g p o i n t , the c h e m i c a l i n j e c t i o n l i n e c a n b e d i s c o n n e c t e d a n d a s a m p l e c a n b e t a k e n d i r e c t l y f r o m the i n j e c t i o n p o i n t . H o w e v e r , c a u t i o n m u s t b e exercised, because it is e x t r e m e l y d i f f i c u l t to o b t a i n u n c o n t a m i n a t e d samples f r o m c h e m i c a l i n j e c t i o n points i n spite o f p u r g i n g . C o n s e q u e n t l y , it is advis able to a v o i d i n j e c t i o n points as s a m p l i n g p o i n t s . A n i d e a l s a m p l e f o r b o t t l e testing (discussed i n the next section) is a stable c o m p o s i t e e m u l s i o n c o n t a i n i n g 3 0 % w a t e r . W h e n a c o m p o s i t e s a m p l e is not suitable, as e v i d e n c e d b y a lack o f stability, c h e m i c a l c o n t a m i n a t i o n , o r l o w w a t e r cut (content), a c o m p o s i t e o f several w e l l h e a d samples m u s t b e u s e d . [ " C u t " refers to the process o f d e t e r m i n i n g the B S & W (basic s e d i m e n t a n d water) content o f the o i l phase i n a s a m p l e o f p r o d u c e d fluid. C u t s c a n b e t a k e n f r o m the t o p , m i d d l e , o r interface o f the o i l phase.]

Testing Procedures. Bottle Test. T h e most w i d e l y a d o p t e d p r o c e d u r e for testing e m u l s i o n s is the s o - c a l l e d bottle test m e t h o d . A d e t a i l e d d e s c r i p t i o n o f the b o t t l e test p r o c e d u r e is p r o v i d e d i n A p p e n d i x A (2). A l s o , C h a p t e r 3 gives i n f o r m a t i o n o n this t o p i c . T h e p u r p o s e o f the bottle test is to p r o v i d e i n f o r m a t i o n about the effectiveness o f t r e a t m e n t c h e m i c a l s f o r a given emulsion. T h e bottle test is excellent f o r s c r e e n i n g p r o s p e c t i v e d e m u l s i f i e r c h e m i cals f o r p l a n t use. H o w e v e r , it is less r e l i a b l e w h e n d e t e r m i n i n g the q u a n t i t y (dosage) o f c h e m i c a l r e q u i r e d to treat a specific e m u l s i o n u n d e r p l a n t c o n d i tions. ( A r u l e o f t h u m b that has b e e n p r o p o s e d (4) correlates 6 - 8 h i n a b o t t l e test w i t h 24 h i n the p l a n t ) . F o r e x a m p l e , the bottle test m a y i n d i c a t e


350

EMULSIONS IN THE PETROLEUM

INDUSTRY

that 0.010 m L o f a specific d e m u l s i f i e r is r e q u i r e d to treat 100 m L o f an e m u l s i o n (i.e., 100 p p m ) ; yet, u n d e r p l a n t operations o n l y 50 m L is r e q u i r e d to treat 1 m o f e m u l s i o n (i.e., 50 p p m ) . Several factors m a y be i n f l u e n c i n g this d i v e r g e n c e (5): 3

• T h e chemical, injected continuously in-line during plant oper ations, m a y b e b e t t e r d i s p e r s e d t h a n i n the bottle test w h e r e a


specific v o l u m e is a d d e d . • T h e sample t a k e n f o r bottle test purposes f r o m a valve o r stopcock m a y be m o r e e m u l s i f i e d t h a n the e m u l s i o n i n the flow l i n e because o f s p l i t t i n g action o f the s a m p l i n g orifice. • T h e bottle test sample does not always r e p r e s e n t the f u l l stream. W e l l s (headers) p r o d u c i n g little or no water may have b e e n o m i t t e d f r o m the test. • T h e bottle test sample is t y p i c a l o f the average e m u l s i o n o n l y at the t i m e o f s a m p l i n g . A v a r i a t i o n i n the characteristics o f the e m u l s i o n flowing to the treater is l i k e l y s i m p l y because o f c o m b i n a t i o n s o f v a r i e d speeds o f p u m p strokes f o r wells p r o d u c i n g d i f f e r e n t w a t e r - c o n t e n t levels. • I n the bottle test, o n l y one d e m u l s i f i c a t i o n process occurs f o r a sample o f e m u l s i o n treated w i t h a fixed a m o u n t o f c h e m i c a l . I n the p l a n t , any r e s i d u a l d e m u l s i f i e r i n the treated o i l o r at the interface can act again o n fresh e m u l s i o n . E x p e r i m e n t s have s h o w n (5) that the t r e a t e d o i l f r o m a bottle test can be u s e d again to treat h a l f o f its v o l u m e o f fresh e m u l s i o n . S i m i l a r l y , o t h e r experiments have s h o w n that the w a t e r r e c o v e r e d f r o m a bottle test c a n also treat about h a l f its v o l u m e o f fresh e m u l sion.

A s a r u l e o f t h u m b , a g o o d estimate o f p l a n t d e m u l s i f i e r dosage r e q u i r e m e n t is h a l f the dosage i n d i c a t e d b y a bottle test. Plant Test. T h e u l t i m a t e p r o o f o f a demulsifier's p e r f o r m a n c e is the p l a n t test. T h e most e n c o u r a g i n g bottle test results are o n l y an i n d i c a t i o n o f a given chemical's expected performance under plant conditions. T h e dura t i o n o f s u c h a test m a y b e as short as 1 day o r as l o n g as 2 weeks, d e p e n d i n g u p o n the p a r t i c u l a r t r e a t m e n t circumstances (i.e., e m u l s i o n a n d t r e a t m e n t facilities' nature a n d size).

characteristics

B e f o r e any c h e m i c a l change is m a d e i n a system that is o p e r a t i n g u n satisfactorily, the p e r f o r m a n c e o f the existing system c o n d i t i o n s s h o u l d b e m o n i t o r e d f u l l y a n d r e c o r d e d . T h e f o l l o w i n g data s h o u l d be i n c l u d e d (6):


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• i d e n t i f i c a t i o n o f the system • date a n d t i m e • a l l p r o d u c t i o n data ( o i l , water, gas, etc.) • a l l c h e m i c a l s , t h e i r c o n s u m p t i o n (daily), a n d p u m p s p e e d • t e m p e r a t u r e s o f vessels (heater treater, g u n b a r r e l , etc.) • a m o u n t o f interface i n t r e a t m e n t vessels


• w a t e r content at various points i n the p l a n t : 1. i n l e t stream(s) 2. samples o f the o i l phase i n F W K O t a k e n f r o m the h i g h a n d l o w petcocks 3. a l l interfaces i n a l l t r e a t m e n t vessels 4. o i l streams out o f a l l treaters and/or tanks • q u a l i t y o f r e c o v e r e d w a t e r (parts p e r m i l l i o n o f s u s p e n d e d o i l a n d insolubles) • amount of recycled oil • c o n d i t i o n o f the c h e m i c a l p u m p ( s ) •

BS&W o f sales o i l

• any o t h e r p e c u l i a r i t i e s i n the system

A l l o f this i n f o r m a t i o n is r e q u i r e d to establish a base l i n e a n d d e t e r m i n e r e t e n t i o n t i m e t h r o u g h o u t the p l a n t b e f o r e i n t r o d u c i n g the n e w chemical(s). T h e p l a n t test starts w h e n the n e w c h e m i c a l is first i n j e c t e d i n t o the system. T h e p e r f o r m a n c e o f the n e w c h e m i c a l is w e l l m o n i t o r e d u n t i l the system is c l e a r e d o f the o l d c h e m i c a l . R e p l a c i n g the o l d c h e m i c a l e n t i r e l y has the advantage o f d e m o n s t r a t i n g the q u i c k e s t results; h o w e v e r , there is also a greater risk o f a p l a n t upset. M o s t c h e m i c a l s are c o m p a t i b l e , b u t i n some circumstances a short p e r i o d o f e i t h e r p o o r o r e x c e p t i o n a l l y g o o d t r e a t m e n t d u r i n g the changeover results. G e n e r a l l y , the dosage o f the n e w c h e m i c a l is g r a d u a l l y i n c r e a s e d u n t i l the o l d m a t e r i a l is e n t i r e l y d i s p l a c e d . T h e f r e q u e n c y o f data c o l l e c t i o n s h o u l d b e l i n k e d to the plant's r e t e n t i o n t i m e . F o r e x a m p l e , i n a system w i t h a 12-h r e t e n t i o n t i m e , the cuts o n the system s h o u l d be m a d e every 2 h ; a system that has a r e t e n t i o n t i m e o f 15 m i n m u s t be m o n i t o r e d c o n t i n u o u s l y .

Interpreting Results. O b j e c t i v i t y is p a r a m o u n t i n i n t e r p r e t i n g b o t h bottle test a n d p l a n t test results. Items to c o n s i d e r i n c l u d e the f o l l o w ing.


352



Centrifuge Cut. T h e c e n t r i f u g e c u t is g e n e r a l l y c o n s i d e r e d t o b e t h e most i m p o r t a n t attribute o f bottle testing. ( T h e t e r m " c e n t r i f u g e c u t " refers to t h e m e t h o d o f analysis rather t h a n t h e p o i n t o f s a m p l i n g . T h u s , a c e n t r i fuge c u t c a n b e t a k e n f r o m t h e t o p , m i d d l e , o r interface o f t h e o i l phase.) A l t h o u g h there are a f e w instances w h e r e e m u l s i o n s c a n b e e v a l u a t e d w i t h o u t this final step, o m i t t i n g this step is g e n e r a l l y p o o r p r a c t i c e because s m a l l quantities o f basic s e d i m e n t o r w a t e r m a y b e o v e r l o o k e d . B o t t l e testing m u s t y i e l d at least p i p e l i n e specifications that c u r r e n t l y a m o u n t to a m a x i m u m a l l o w a b l e B S & W o f 0.5%. M i n i m u m basic s e d i m e n t (i.e., t h e e n t i r e p o r t i o n o f B S & W is c o m p o s e d o f s i m p l y water) is h i g h l y favorable i n that i t w i l l r e d u c e t h e b u i l d u p a n d subsequent h a n d l i n g o f tank b o t t o m s . Oil Color. E m u l s i o n s are characteristically h a z y i n appearance, i n contrast to t h e brightness o f t r e a t e d o i l . T h e hazy c o l o r is d u e to a h i g h c o n c e n t r a t i o n o f fine w a t e r d r o p l e t s d i s p e r s e d i n the o i l s a m p l e . E s s e n t i a l l y , o i l brightness is a measure o f t h e w a t e r d r o p l e t size a n d the a m o u n t o f d i s p e r s e d w a t e r i n t h e o i l phase. W h e n these w a t e r d r o p l e t s b e c o m e i n v i s i b l e to t h e n a k e d eye, t h e o i l phase takes o n a " c l o u d y " appearance (6). A l t e r n a t i v e l y , as an e m u l s i o n coalesces i n t o larger d r o p l e t s , t h e o i l phase b e c o m e s b r i g h t e r . C o n s e q u e n t l y , t h e o i l brightness c a n b e i n c r e a s e d i n t w o ways: e i t h e r t h r o u g h a r e d u c t i o n i n t h e n u m b e r o f d r o p l e t s o r t h r o u g h a n increase i n w a t e r d r o p l e t size. A r e d u c e d n u m b e r o f particles i m p l i e s that the c r u d e o i l is b e c o m i n g d r i e r ; this is n o t necessarily t h e case for i n c r e a s e d d r o p l e t size. C o n s e q u e n t l y , o i l brightness c a n b e d e c e p t i v e as a sole d e t e r m i n a n t i n s e l e c t i n g a n a p p r o p r i a t e c h e m i c a l . It f o l l o w s that c o l o r is n o guarantee o f a successful d e m u l s i f i e r , b u t haziness is assurance that t h e c h e m i c a l is i n e f f e c t i v e . Interface. T h e d e s i r e d interface, r e f e r r e d to as a m i r r o r interface, has a s h i n y o i l at its t o p surface. Solids present i n t h e c r u d e o i l f r e q u e n t l y p r e v e n t t h e o c c u r r e n c e o f a m i r r o r interface e v e n i n t h e presence o f selected c h e m i c a l s . I f the c r u d e o i l has n o k n o w n p a r a f f i n p r o b l e m s o r solids a n d has a m e d i u m to l o w density, a s m o o t h interface s h o u l d b e e x p e c t e d . H o w e v e r , the opposite c i r c u m s t a n c e s s h o u l d n o t b e expected t o p r o d u c e a s m o o t h i n t e r f a c e . H o w e v e r , i f any o f the a f o r e m e n t i o n e d p r o b l e m s is present b u t a s m o o t h interface is s t i l l o b s e r v e d , t h e n e m u l s i o n is q u i t e l i k e l y h e l d u p i n t h e o i l phase. Water Quality. T h i s characteristic (i.e., t u r b i d i t y ) is u s u a l l y d i f f i c u l t to i n t e r p r e t i n the bottle test a n d c o n s e q u e n t l y to correlate w i t h p l a n t b e h a v i o r . C l e a r w a t e r is d e f i n i t e l y t h e d e s i r e d result. C o m p l i c a t i o n s , h o w ever, arise w h e n solids are p r e s e n t i n t h e c r u d e o i l . T h e r e f o r e , it is necessary to r e m o v e the solids w i t h t h e w a t e r , a l o n g w i t h any o i l a d s o r b e d o n these


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Emulsions

353


solids. R e m o v i n g the o i l w i l l d i s c o l o r the w a t e r somewhat; t h e r e f o r e , a c l e a r p r o d u c t m a y be u n l i k e l y . W e t t i n g agents a p p l i e d w i t h d e m u l s i f i e r s i n treat i n g plants have i m p r o v e d the d e h y d r a t i o n a n d d e o i l e d the solids to a r e m a r k able extent (2). H o w e v e r , this result has not b e e n o b s e r v e d i n bottle testing w h e r e the w a t e r is f r e q u e n t l y m o r e t u r b i d w h e n the w e t t i n g agents are i n c l u d e d . D e o i l i n g o f the solids is a c o n c e n t r a t i o n effect, a n d h i g h c o n centrations o f surfactants w i t h p a r t i a l w a t e r s o l u b i l i t y m a k e the w a t e r phase turbid. Sludge. S l u d g e c a n f o r m o r a c c u m u l a t e at the m i d d l e , at the i n t e r f a c e , or at the surface o f the o i l phase. I n c e r t a i n systems, n o n c o a l e s c e d w a t e r d r o p l e t s w i l l result i n a loose a g g l o m e r a t i o n that separates i n t o w a t e r a n d o i l w i t h o u t any p r o b l e m . T h i s separation is a f o r m o f " m i d d l e " sludge that w i l l not a c c u m u l a t e . H o w e v e r , " i n t e r f a c e " sludge m a y o r m a y not a c c u m u l a t e , d e p e n d i n g u p o n b o t h the system a n d the sludge stability. T h i s sludge c a n b e s t a b i l i z e d b y finely d i v i d e d solids a n d o t h e r c o n t a m i n a n t s to f o r m pads. L o o s e interface sludge c a n b e d e t e c t e d s w i r l i n g about the axis o f the test b o t t l e . F i n a l l y , " s u r f a c e " sludge, the most d i f f i c u l t to d e s c r i b e , is w a t e r i n the f o r m o f d r o p l e t s that r e m a i n floating o n top o f the o i l phase. Surface sludge c a n be d e t r i m e n t a l i n systems i n w h i c h r e s i d e n c e t i m e is c r i t i c a l , i n that the sludge c a n b e c a r r i e d over. S l u d g i n g characteristics c a n appear as o v e r t r e a t m e n t . T h e d i f f e r e n c e b e t w e e n the t w o is that sludge c a n b e present at any g i v e n ratio, l o w o r h i g h , d e p e n d i n g u p o n the c r u d e o i l ; o v e r t r e a t m e n t traits are n o t a b l y associated w i t h excessive c h e m i c a l . S l u d g i n g characteristics o f a d e m u l s i f i e r s h o u l d b e i d e n t i f i e d d u r i n g the course o f the bottle test w o r k . T h i s i d e n t i f i c a t i o n is easily d o n e b y u s i n g an excess a m o u n t o f the c h e m i c a l (i.e., 4 m L o f 1 0 % solution) i n a bottle a n d o b s e r v i n g the c o n d i t i o n o f the o i l after agitation. I f top, m i d d l e , o r interface sludge is n o t e d or i f the o i l is r e - e m u l s i f i e d , the c h e m i c a l s h o u l d be u s e d w i t h c a u t i o n .

Selecting Appropriate Separation Equipment T h i s section b r i e f l y discusses the m o r e f r e q u e n t l y e m p l o y e d e q u i p m e n t types that c o m p r i s e a t y p i c a l e m u l s i o n - t r e a t m e n t p l a n t c o n f i g u r a t i o n ( F i g u r e 3). A p p e n d i x Β describes C A N M E T ' s p i l o t - s c a l e d e m u l s i o n - t r e a t m e n t facilities l o c a t e d at the C o a l R e s e a r c h L a b o r a t o r i e s near D e v o n , A l b e r t a , Canada.

Free-Water Knockout. B y d e f i n i t i o n , free w a t e r is any w a t e r asso c i a t e d w i t h the c r u d e - o i l e m u l s i o n that settles out w i t h i n 5 m i n w h i l e the p r o d u c e d fluids are stationary i n a s e t t l i n g space w i t h i n a vessel. F r e e - w a t e r k n o c k o u t s ( F W K O ) are s i m p l y three-phase separation vessels that separate



Water

Oil Chemical^ Injection

Oil Water

TREATING SECTION

I>—c

1—

Vapor Recovery

Oil

Flotation Cell Π,Π,Π,Π

Disposal

SEPARATION SECTION

Flowline Heater

L A C T Unit

[Reject

Manual Gauging

u

Clean Oil To Trucking

D

Water To Disposal/ Injection Well(s)

f Water

FWKO

Heater Treater

Gas

Oil

with

STORAGE SHIPPING SECTION

Storage Tank

Oil &Gas Separator

Figure 3. Typical flow diagram of production facilities. (Reproduced permission from reference 7. Copyright 1987 Elsevier.)

Clean Oil To Pipeline

GATHERING S Y S T E M

Test Separator

From Oil Well(s)

Gas


5

G H

α

Ζ

c

M hd w H w ο r M

Η

r δ ζ

C

m

οι

10.

LEOPOLD



355

large amounts o f free w a t e r f r o m the c r u d e - o i l e m u l s i o n . A n y p r o d u c e d gases associated w i t h these p r o d u c e d l i q u i d s are also separated a n d r e m o v e d


o v e r h e a d ( F i g u r e 1). A l t h o u g h F W K O s are not c o n s i d e r e d to b e t r e a t m e n t e q u i p m e n t p e r se, t h e i r d i s c u s s i o n here is a p p r o p r i a t e because t h e y are u s e d extensively i n c o n j u n c t i o n w i t h t r e a t m e n t e q u i p m e n t . S p e c i f i c applications f o r F W K O vary w i t h each situation. I n some cases, the a m o u n t o f w a t e r r e m o v e d b y the F W K O m a y not be c r u c i a l p r o v i d e d the t r e a t m e n t facilities d o w n s t r e a m are p e r f o r m i n g effectively. W h e n excessive amounts o f w a t e r are p r o d u c e d w i t h the c r u d e - o i l e m u l s i o n , as i n secondary r e c o v e r y (i.e., water-flood) projects, it m a y b e necessary to specify r e q u i r e m e n t s o f 2 0 % w a t e r to ensure p r o p e r treater p e r f o r m a n c e . T h r e e - P h a s e Separators. I n a d d i t i o n to F W K O s , this category i n c l u d e s a b r o a d array o f t r e a t i n g vessels d e s i g n e d , as t h e i r n a m e suggests, to separate p r o d u c e d fluids i n t o three d i s t i n c t p r o d u c t s : gas a n d t w o i m m i s c i b l e l i q u i d s o f d i f f e r e n t densities (i.e., o i l a n d w a t e r ) . G e n e r a l l y , s u c h vessels are e m p l o y e d w h e r e separation o r m e a s u r e m e n t o f a l l three phases is r e q u i r e d (i.e., p r o d u c t i o n testing o f i n d i v i d u a l w e l l s o r streams). Separators e m p l o y as m a n y as three d i f f e r e n t f u n d a m e n t a l separation m e c h a n i s m s : (1) gravitational separation, (2) i m p i n g e m e n t a n d coalescence, a n d (3) c e n t r i f u g a l separation ( F i g u r e 4). Gravitational Separation. T h i s process is b o t h the s i m p l e s t a n d most u n i v e r s a l l y e m p l o y e d i n a l l types o f separators. It is b a s e d u p o n the fact that aqueous c o m p o n e n t s o f an i n l e t stream have a greater d e n s i t y t h a n the associated p e t r o l e u m fractions. T h u s , aqueous c o m p o n e n t s are subject to greater d o w n w a r d gravitational f o r c e . T h e l i q u i d (aqueous) d r o p l e t s settle out o f a l i g h t e r ( p e t r o l e u m ) phase i f the gravitational f o r c e a c t i n g o n the d r o p l e t is greater t h a n the d r a g f o r c e o f the o i l flowing a r o u n d the d r o p l e t . F u r t h e r m o r e , f o r c o n v e n t i o n a l c r u d e - o i l e m u l s i o n s , the w a t e r present i n the l i q u i d phase is u s u a l l y h e a v i e r t h a n the o i l phase, a n d i t s u b s e q u e n t l y settles b e l o w the o i l . I n h e a v y - o i l e m u l s i o n s , i n w h i c h the t w o l i q u i d s are o f s i m i l a r densities, separation b y means o f gravity is e x t r e m e l y i n e f f i c i e n t . T h e r e f o r e , agents s u c h as c h e m i c a l s , heat, a n d e l e c t r i c i t y are e m p l o y e d to increase the rate o f separation. Impingement and Coalescence. I m p i n g e m e n t separation relies u p o n the d i f f e r e n c e i n m o m e n t u m , e i t h e r b e t w e e n a gas p a r t i c l e a n d a l i q u i d droplev, o r b e t w e e n t w o l i q u i d d r o p l e t s . It occurs w h e n l i q u i d - l a d e n gas approaches a c o a l e s c i n g device o r target (e.g., w i r e m e s h p a d , vane e l e m e n t , o r filter cartridge). T h i s c o a l e s c i n g d e v i c e causes the gas to f o l l o w a tortuous p a t h , w h i l e the l i q u i d d r o p l e t s c o n t i n u e i n a straighter p a t h a& a result o f


356


, vessel wall


liquid particle ·

GRAVITY SEPARATION

liquid particle -

ν

vessel wall

IMPINGEMENT SEPARATION

Figure 4. Schematic of separation processes. (Reproduced with permission from reference 6. Copyright 1990 Petroleum Industry Training Service.)


10.

LEOPOLD


and Process-Stream

Emulsions

357


t h e i r greater m o m e n t u m . T h e s e l i q u i d d r o p l e t s c o n s e q u e n t l y i m p i n g e the targets o r c o l l i d e w i t h each o t h e r a n d t h e r e b y coalesce. A s these d r o p l e t s increase i n size, the effects o f gravity b e c o m e significant, a n d the d r o p l e t s f a l l t o w a r d the l i q u i d c o l l e c t i o n section o f the vessel. Centrifugal Separation. T h e final separation process e m p l o y e d i n the d e s i g n o f three-phase separators relies o n the fact that fluid phases w i t h d i f f e r e n t densities have d i f f e r e n t m o m e n t u m . C e n t r i f u g a l separation takes p l a c e w h e n the i n l e t stream is f o r c e d to rotate at h i g h velocities i n s i d e a vessel t h r o u g h the use o f a tangential e n t r y o r deflector. T h e change i n d i r e c t i o n forces the l i q u i d d r o p l e t s to the vessel w a l l because o f t h e i r greater m o m e n t u m . T h e r e they coalesce a n d e v e n t u a l l y d r o p to the vessel's l i q u i d section.

Heater Treaters. T h e heater treater is the u l t i m a t e p r o c e s s i n g step i n the e m u l s i o n - t r e a t m e n t p l a n t schematic. T h i s vessel effects the actual b r e a k i n g o f the e m u l s i o n i n t o treated o i l a n d p r o d u c e d o i l y w a t e r streams. O i l - f i e l d e m u l s i o n treaters are e i t h e r h o r i z o n t a l o r v e r t i c a l i n o r i e n t a t i o n . H o r i z o n t a l heater treaters n o r m a l l y have a h i g h t h r o u g h p u t r e q u i r i n g r a p i d d e m u l s i f i e r a c t i o n . T h e large interface area (and c o n s e q u e n t l y shallow fluid depth) i n a h o r i z o n t a l heater treater requires that the interface b e v e r y c l e a n (i.e., sharp, u n o b s t r u c t e d ) . C o n s e q u e n t l y , this treater c a n tolerate v e r y l i t t l e interface b u i l d u p . T h e h i g h e r the t h r o u g h p u t , the l o w e r the tolerance f o r interface b u i l d u p . V e r t i c a l treaters have a m u c h l o w e r v o l u m e - t o - t h r o u g h p u t ratio t h a n g u n barrels. A s a result, m o r e c o m p l e t e t r e a t m e n t is necessary i n a shorter t i m e . Solids c o n t r o l is as i m p o r t a n t as interface c o n t r o l , just as w i t h the h o r i z o n t a l treater. F i g u r e 5 illustrates a schematic o f a v e r t i c a l heater treater that also e m p l o y s a d u a l - p o l a r i t y electrostatic g r i d to effect m o r e efficient coalescence a n d t h e r e b y b e t t e r o i l - w a t e r separation.

Induced Gas Flotation. M e c h a n i c a l l y i n d u c e d gas flotation ( I G F ) is e m p l o y e d extensively to r e m o v e s u s p e n d e d solids, o i l , a n d o t h e r o r g a n i c matter f r o m o i l - f i e l d a n d r e f i n e r y wastewaters. C o n s e q u e n t l y , these I G F units are p a r t i c u l a r l y s u i t e d to the treatment o f o i l - i n - w a t e r o r reverse e m u l s i o n s . S u c h units generally f o l l o w gravity o i l - w a t e r separation units s u c h as F W K O s , g u n barrels, a n d s k i m tanks i n o i l - f i e l d - p r o d u c e d w a t e r treatment schemes, a n d also h a n d l e the o i l y w a t e r streams g e n e r a t e d f r o m all treaters i n a specific p r o d u c e d - f l u i d treatment p l a n t . I n d u c e d gas flotation c a n c l e a n large quantities o f wastewater c o n t a i n i n g 2 0 0 - 5 0 0 0 p p m o f s u s p e n d e d o i l , d e p e n d i n g u p o n the nature o f the o i l a n d its e m u l s i o n w i t h the p r o d u c e d water. I n most cases, the o i l content o f the I G F effluent w a t e r is less t h a n 10 p p m after a 4 - m i n c l e a n i n g c y c l e .


358


1, ι

, I


I

r, )

OH out

Emulsion

Electrode assembly detail Figure 5. Dual-polarity

electrostatic treater, simplified internal

structure.


10.

LEOPOLD

359

Breaking Produced-Fluid and Process-Stream Emulsions

T h e s e units g e n e r a l l y consist o f f o u r flotation cells ( F i g u r e 6), each o f w h i c h is e q u i p p e d w i t h a m o t o r - d r i v e n self-aerating r o t o r m e c h a n i s m . T h e f o l l o w i n g describes t h e p r i n c i p l e o f o p e r a t i o n (8):


As the rotor spins, it acts as a pump, forcing water through a disperser and creating a vacuum in the standpipe. The vacuum pulls gas into the standpipe and thoroughly mixes it with the water. As the gas-water mixture travels through the disperser at high velocity, a mixing force is created, causing the gas to form minute bubbles. Oil particles and suspended solids attach to the gas bubbles as they rise to the surface. The oil and suspended solids gather in a dense froth at the surface, are removed from the cell by skimmer paddles, and collected in internal launders. T h e o i l a n d solids c o l l e c t e d f r o m the l a u n d e r s are t h e n passed a l o n g t o the o i l - h a n d l i n g system; t h e r e c o v e r e d p r o d u c e d water, p r o v i d i n g i t meets the necessary r e q u i r e m e n t s , is e i t h e r d i s p o s e d o f o r r e u t i l i z e d i n t h e o i l r e c o v e r y process. I f the w a t e r is t o b e r e i n j e c t e d , c l e a n i n g b y the I G F u n i t prevents f o r m a t i o n p l u g g i n g a n d r e d u c e d p u m p efficiency. I f the w a t e r is t o b e u s e d f o r steam g e n e r a t i o n , t h e I G F is u s e d b e f o r e t h e t r a d i t i o n a l b o i l e r pretreatment equipment.

Figure 6. Induced gas flotation cell, section view. (Courtesy ofWEMCO cess Equipment Company.)


Pro-

360

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

Process Plant Design Considerations W h e n d e t e r m i n i n g t h e size o f a treater f o r a specific service, three signifi cant b u t i n d e p e n d e n t variables m u s t b e d e f i n e d : (1) t h e vessel's d i a m e t e r , (2) t h e l e n g t h - t o - h e i g h t ratio o f the c o a l e s c i n g section, a n d (3) t h e average t r e a t i n g t e m p e r a t u r e . I n t h e absence o f a u n i q u e s o l u t i o n , u n d e r l y i n g as sumptions and engineering judgement must be employed i n developing an a p p r o p r i a t e treater d e s i g n . B r i e f l y , this iterative process is as follows (3):


1. A t r e a t i n g t e m p e r a t u r e is c h o s e n . 2. T h e o i l viscosity at t h e t r e a t i n g t e m p e r a t u r e is d e t e r m i n e d . 3. T h e d i a m e t e r o f the w a t e r d r o p l e t that m u s t b e r e m o v e d f r o m the o i l at t h e t r e a t i n g t e m p e r a t u r e is d e t e r m i n e d . 4. T h e treater g e o m e t r y necessary to satisfy t h e s e t t l i n g c r i t e r i a is d e t e r m i n e d . 5. T h e g e o m e t r y is c h e c k e d to ensure that it p r o v i d e s sufficient retention time. 6. T h e p r o c e d u r e is r e p e a t e d f o r d i f f e r e n t a s s u m e d t r e a t i n g temperatures. T h i s p r o c e d u r e , a l t h o u g h i t does not y i e l d t h e o v e r a l l d i m e n s i o n s o f the treater ( i n c l u d i n g t h e i n l e t gas separation a n d F W K O sections), does p r o vide a methodology for specifying the heating requirements and a m i n i m u m size f o r t h e c o a l e s c i n g section (where t h e treatment actually occurs). It is also i n v a l u a b l e w h e n e v a l u a t i n g v e n d o r proposals a n d w h e n l i m i t e d l a b o r a t o r y data are available.

Vessel Capacity Determination. Vessel Diameter. F o r c o n v e n t i o n a l o i l - t r e a t m e n t systems, t h e specific g r a v i t y d i f f e r e n c e b e t w e e n t h e d i s p e r s e d w a t e r droplets a n d t h e o i l s h o u l d result i n t h e w a t e r " s i n k i n g " to the b o t t o m o f the treater vessel. T h e d o w n w a r d v e l o c i t y o f the w a t e r d r o p l e t m u s t b e sufficient to o v e r c o m e t h e u p w a r d v e l o c i t y o f the o i l phase t h r o u g h o u t t h e treater. A g e n e r a l s i z i n g e q u a t i o n is d e r i v e d b y setting these t w o velocities e q u a l to each o t h e r (3). F o r h o r i z o n t a l vessels, 3

d = 0.2418

(l)

L «àSGcP e

m

F o r v e r t i c a l vessels, 1/2

d = 0.1691

àSGcE

(2)

Specific (i.e., "relative") gravity is defined as the ratio of the weight of a given volume of a liquid at 15.5 °C (60 °F) to the weight of the same volume of water at 15.5 °C (60 °F). 3


10.

LEOPOLD


and Process-Stream

Emulsions

361

w h e r e d is vessel d i a m e t e r (m), Q is the o i l flow rate (m /h), μ is o i l viscosity ( m P a · s), L is the l e n g t h o f the c o a l e s c i n g section (m), A S G is the d i f f e r e n c e i n specific gravity b e t w e e n the o i l a n d w a t e r (relative to the water), a n d d is the d i a m e t e r o f a w a t e r d r o p l e t (μτη). 3

Q

e f f

m


I n a h o r i z o n t a l vessel, the cross-sectional area o f the flow f o r the u p w a r d v e l o c i t y o f the o i l is a f u n c t i o n o f the vessel d i a m e t e r a n d the l e n g t h o f the coalescing section. F o r a v e r t i c a l treater, the h e i g h t o f the coalescing section does not e n t e r the e q u a t i o n . F o r l a r g e r d i a m e t e r , v e r t i c a l - f l o w treaters (i.e., s u c h as g u n barrels) a c o r r e c t i o n factor f o r s h o r t - c i r c u i t i n g effects m u s t b e i n c l u d e d i n the e q u a t i o n . Retention Time. T o effectively d e m u l s i f y an o i l - i n - w a t e r e m u l s i o n , it m u s t be h e l d at a suitable t r e a t i n g t e m p e r a t u r e f o r a specific t i m e p e r i o d . I n the absence o f e x p e r i m e n t a l data, 2 0 - 3 0 m i n is u s u a l l y a realistic estimate f o r r e t e n t i o n t i m e f o r c o n v e n t i o n a l o i l projects; f o r h e a v y - o i l r e c o v e r y o p e r a tions, r e t e n t i o n times c o u l d be several h o u r s . N o n e t h e l e s s , the vessel g e o m etry a n d specifications r e q u i r e d f o r a specific r e t e n t i o n t i m e m a y not neces sarily b e the same as those d i c t a t e d b y the settling r e q u i r e m e n t s . T h e s o l u t i o n is to select the larger g e o m e t r y a n d d i m e n s i o n s d e t e r m i n e d b y e i t h e r o f the t w o c r i t e r i a . T h e r e t e n t i o n t i m e is d e t e r m i n e d as follows (3). F o r h o r i z o n t a l vessels, i =^ 2 32ρ

(3)

r

0

F o r v e r t i c a l vessels, t = - ^ 3369ρ

(4) ο

w h e r e t is r e t e n t i o n t i m e ( m i n ) , d is vessel d i a m e t e r (m), Q is o i l flow rate (m /h), L is the l e n g t h o f the coalescing section (m), a n d h is the h e i g h t o f the coalescing section (m). T

3

Q

e f f

Water Droplet Size. T o find a s o l u t i o n to the settling e q u a t i o n (i.e., f o r e i t h e r e q u a t i o n 1 or 2), the w a t e r d r o p l e t size, d , m u s t b e k n o w n . Q u a l i t a t i v e l y , the w a t e r d r o p l e t size is e x p e c t e d to increase w i t h an increase i n r e t e n t i o n t i m e i n the c o a l e s c i n g section a n d w i t h heat i n p u t . C o n v e r s e l y , it s h o u l d decrease w i t h increase i n the oil-phase viscosity. F u r t h e r m o r e , vis cosity w i l l have a greater effect o n coalescence t h a n t e m p e r a t u r e . P r a c t i c a l experience i n the d e s i g n o f treaters has r e s u l t e d i n a r e l i a b l e c o r r e l a t i o n o f w a t e r d r o p l e t size to oil-phase viscosity (3): m

d

m

= 500/i


(5)

362


w h e r e d is the d i a m e t e r o f a w a t e r d r o p l e t (μϊη), ( m P a · s). m

a n d μ is the o i l viscosity


N o n e t h e l e s s , there is n o substitute f o r actual e x p e r i m e n t a l data o n d r o p l e t coalescence. T h e u n i v e r s a l i t y o f e q u a t i o n 5 has still to b e p r o v e n .

Product-Stream Quality Requirements, I n a d d i t i o n to the p i p e l i n e - m a r k e t i n g target o f 0 . 5 % B S & W that the t r e a t e d - o i l p r o d u c t m u s t satisfy, there are analogous constraints for the various i n t e r m e d i a t e process streams b a s e d u p o n the d o w n s t r e a m e q u i p m e n t s o p e r a t i n g d e s i g n range. F o r e x a m p l e , i f a h e a v y - o i l e m u l s i o n contains r o u g h l y 6 0 % water, a n d o n l y h a l f o f that q u a n t i t y c a n be r e m o v e d b y the F W K O (i.e., r e s u l t i n g i n 3 0 % B S & W still p r e s e n t i n its effluent stream), a h e a v y - o i l e v a p o r a t i o n ( H O E ) d e h y d r a t i o n u n i t r e q u i r i n g a n i n l e t stream c o n t a i n i n g n o m o r e t h a n 1 0 % w a t e r cannot s i m p l y be u s e d to r e d u c e the B S & W l e v e l to the p i p e l i n e specifications o f 0.5%. A n i n t e r m e d i a r y stage, p r e f e r a b l y a heater treater, m u s t b e e m p l o y e d to s u p p l e m e n t the t r e a t m e n t effort. T h e majority o f the r e m a i n i n g B S & W p r e f e r a b l y s h o u l d be r e m o v e d i n the first (primary) treat m e n t stage. T h u s any u n e x p e c t e d or i n f r e q u e n t excessive treatment d e mands c a n b e t r a n s f e r r e d o n to the secondary treatment stage. I n the forego i n g e x a m p l e , it w o u l d be b e t t e r to treat the e m u l s i o n i n the first stage to a n effluent l e v e l o f 5 % (if attainable) a n d have a d d e d t r e a t i n g capacity r e m a i n i n g i n the secondary treater, t h a n to m e r e l y target for the i n l e t c o n d i t i o n s o f the secondary treater. S i m i l a r arguments c a n be m a d e f o r the a d d i t i o n o f a d o w n s t r e a m filtering system to the gas flotation u n i t i n the o i l y w a t e r treat m e n t stage. Material Balance Requirements. R e g u l a r p r o d u c t i o n testing o f i n d i v i d u a l o i l w e l l s is a m a n d a t o r y r e q u i r e m e n t for p r o p e r p r o d u c t i o n ac c o u n t i n g . A g o o d p r a c t i c e is to place a w e l l o n a p r o d u c t i o n test 1 day o f every m o n t h , i f feasible, to d e t e r m i n e its i n d i v i d u a l o i l - , water-, a n d gasp r o d u c i n g rates. T h e results c a n t h e n b e u s e d to allocate that specific w e l l ' s c o n t r i b u t i o n to the o v e r a l l p r o d u c i n g rates o n a m o n t h l y basis b a s e d u p o n a fieldwide p r o r a t i o n factor. T h e s e allocations are u p d a t e d w i t h each n e w p r o d u c t i o n test f o r that specific w e l l . I n essence, the total v o l u m e o f fluids p r o d u c e d at the w e l l sites m u s t b e a c c o u n t e d f o r at the final effluent streams o f the t r e a t m e n t facilities ( e x c l u d i n g a c c u m u l a t i o n w i t h i n the i n d i v i d u a l vessels). T o effectively m o n i t o r the separation efficiency o f the p a r t i c u l a r treat m e n t e q u i p m e n t , t w o specific m e t h o d s are e m p l o y e d : c e n t r i f u g a t i o n (dis c u s s e d b r i e f l y u n d e r " T e s t i n g P r o c e d u r e s " ) a n d the D e a n - S t a r k analysis. T h e D e a n - S t a r k analysis d e t e r m i n e s the f r a c t i o n a l c o m p o s i t i o n o f o i l - h y d r o c a r b o n , water, a n d solids o f an e m u l s i o n stream b y u s i n g a d i s t i l l a t i o n process. Its results f o r h e a v y - o i l e m u l s i o n s are generally m o r e r e l i a b l e t h a n those o b t a i n e d b y c e n t r i f u g a t i o n ; h o w e v e r , the results o f c e n t r i f u g a t i o n are


10.

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Emulsions

363

available w i t h i n m i n u t e s o f s a m p l i n g , c o m p a r e d to a 1 - 2 - d a y t u r n a r o u n d f o r D e a n - S t a r k analyses. T h e s e results, w h e n c o u p l e d w i t h p r o c e s s - s t r e a m flow m e a s u r e m e n t s , p r o v i d e c o m p r e h e n s i v e i n f o r m a t i o n for c o n d u c t i n g c o m p o n e n t mass balances across the i n d i v i d u a l t r e a t i n g units a n d the entire p l a n t .


Summary T h i s c h a p t e r has dealt w i t h the i m p o r t a n t considerations i n v o l v e d i n c o m m e r c i a l d e m u l s i f i c a t i o n e q u i p m e n t . Just as i n C h a p t e r 9, w h i c h dealt w i t h c h o o s i n g the r i g h t d e m u l s i f i e r , h e r e too, n u m e r o u s t r e a t m e n t options are available. N o u n i q u e set o f c o n d i t i o n s c a n successfully b r e a k a l l o i l - f i e l d p r o d u c e d e m u l s i o n s . Instead, the r e s o l u t i o n o f any specific e m u l s i o n - t r e a t i n g p r o g r a m involves the s e l e c t i o n o f a p a r t i c u l a r set o f c o n d i t i o n s that, a c t i n g together, y i e l d a m a x i m u m t r e a t i n g p e r f o r m a n c e . W h e t h e r an e m u l s i o n comes f r o m a p r o d u c t i o n w e l l h e a d o r f r o m an u p g r a d e r o r refinery, the same choices have to b e m a d e a m o n g c h e m i c a l s to b e u s e d , d r i v i n g forces to be a p p l i e d , o p t i m u m e c o n o m i c s , a n d necessary p r o d u c t qualities to be achieved. T e s t i n g process-stream e m u l s i o n s is a necessity not o n l y for c h a r a c t e r i z i n g the e m u l s i o n itself, b u t also for establishing p e r f o r m a n c e o f the selected t r e a t i n g process. N e v e r t h e l e s s , s a m p l i n g a process-stream e m u l s i o n , the most c r i t i c a l step i n the testing p r o c e d u r e , is m o r e o f an art t h a n a science. E x t e n s i v e w o r k has b e e n d o n e to d e v e l o p s t a n d a r d m e t h o d s o f testing p r o cess-stream e m u l s i o n s . T e s t i n g p r o c e d u r e s , s u c h as the u b i q u i t o u s bottle test, c a n b e u s e d as a first estimate f o r e q u i p m e n t sizing. I n the final analysis, p i l o t - p l a n t testing o f the c h o s e n d e m u l s i f y i n g s c h e m e , w i t h actual field o r p l a n t samples, w i l l l i k e l y be n e e d e d to p r o v i d e realistic data f o r scale-up to p r o d u c t i o n levels. T h e bottle test a n d the p l a n t test, w h i c h is the u l t i m a t e d e t e r m i n a n t o f a successful set o f t r e a t i n g c o n d i t i o n s , have b e c o m e the o i l industry's stand ards. H o w e v e r , f u r t h e r w o r k s h o u l d be u n d e r t a k e n to d e v e l o p a n d refine s a m p l i n g t e c h n i q u e s (i.e., b o t h p r o c e d u r e s a n d h a r d w a r e ) to ensure that samples taken are t r u l y representative, c o m p o s i t e , a n d consistently o b t a i n able.

Appendix A: Bottle Test Procedure T h i s p r o c e d u r e is d e s c r i b e d f u r t h e r i n r e f e r e n c e 2.

Equipment.

T h e e q u i p m e n t n e e d e d is the f o l l o w i n g :

1. s a m p l i n g j u g 2. p o u r i n g d e v i c e


364


3. test bottles o r tubes: 1 7 5 - m L p r e s c r i p t i o n bottles, 1 0 0 - m L t a p e r e d c e n t r i f u g e tubes, a n d any test bottles o f adequate v o l u m e that w i l l a l l o w f o r suitable agitation a n d have a r e l i able 1 0 0 - m L m a r k 4. A P I c e n t r i f u g e tubes 5. pipettes: 0.2, 1.0, 2.0, a n d 10.0 m L 6. syringes: 0.25, 1.0, 5.0, a n d 25.0 m L 7. s o l u t i o n bottles: 15 a n d 30 m L


8. solvent: aromatic o r xylene, i s o p r o p y l a l c o h o l , a n d a 75:25 m i x t u r e o f xylene a n d i s o p r o p y l a l c o h o l 9. d e m u l s i f i e r samples 10. k n o c k o u t d r o p s (i.e., P e t r o l i t e F - 4 6 , F - 1 7 , o r R N - 3 0 0 3 : Champion DN-71) 11. w a t e r b a t h 12. t h e r m o m e t e r ( 0 - 1 0 0 °C) 13. m a r k i n g p e n , labels, a n d test b o o k 14. c e n t r i f u g e 15. o p t i o n a l e q u i p m e n t : s h a k i n g m a c h i n e , r e a d i n g l a m p , c e n t r i fuge t u b e rack, a n d c l o c k t i m e r o r stopwatch

Test Solutions. T h e s e l e c t i o n o f the most a p p r o p r i a t e s o l u t i o n f o r a specific test r e q u i r e s a g e n e r a l u n d e r s t a n d i n g o f the v o l u m e o f c h e m i c a l that w i l l b e r e q u i r e d . E m u l s i o n s o f h i g h - d e n s i t y , h i g h - v i s c o s i t y c r u d e oils m a y r e q u i r e 2 0 0 - 5 0 0 p p m ( 1 . 0 - 2 . 5 m L o f 2 % solution). C e r t a i n slop o i l tests r e q u i r e 1 0 0 0 - 2 0 0 0 p p m (1.0-2.5 m L o f 1 0 % solution). A l t e r n a t i v e l y , v e r y light o i l e m u l s i o n s m a y b e easily b r o k e n w i t h 1 0 - 2 0 p p m (0.05-0.10 m L o f 2 % solution). T h e m e t h o d u s e d to p r e p a r e 2 % solutions is as f o l l o w s : 1. M e a s u r e 24.5 m L o f solvent (i.e., heavy a r o m a t i c naphtha) into a 3 0 - m L bottle. 2. F i l l a 0 . 5 - m L syringe past the 0 . 5 - m L m a r k w i t h the d e s i r e d chemical demulsifier. 3. E x p e l a l l a i r b u b b l e s b y i n v e r t i n g t h e filled syringe a n d g r a d ually p u s h i n g the p i s t o n u p to the 0 . 5 - m L m a r k . 4. E m p t y the contents o f the filled syringe i n t o the bottle c o n t a i n i n g the solvent, a n d shake to dissolve.


10.

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Emulsions

5. M a r k the s o l u t i o n bottle w i t h the n a m e o r n u m b e r o f the demulsifier used.


6. R i n s e the syringe w i t h solvent b e f o r e i t is u s e d again o r p u t away. B e sure to rinse the p i p e t t e o r syringe u s e d to p l a c e solutions i n t o test bottles b e f o r e p l a c i n g it i n a d i f f e r e n t s o l u t i o n . A l s o be c e r t a i n to ensure the absence o f air b u b b l e s w h e n u s i n g syringes w i t h e i t h e r u n d i l u t e d c h e m i c a l o r s o l u tions.

Execution of Bottle Test. 1. P r e p a r e solutions (2 o r 10%) o r mixtures o f solutions o f the c h e m i c a l s to b e tested. 2. O b t a i n a c h e m i c a l - f r e e sample o f the c r u d e o i l to b e tested. 3. T e s t the sample as soon as p o s s i b l e . 4. R e m o v e free water, i f any, f r o m the s a m p l e ; measure a n d save. R e c o r d the a m o u n t o f free w a t e r i n the sample (i.e., 5, 10, o r 2 0 % , etc.). S o m e c h e m i c a l s are m o r e w a t e r - s o l u b l e o r o i l - s o l u b l e t h a n others. T h e p r e s e n c e o f free w a t e r c a n alter the test results, so it s h o u l d b e a d d e d to the o i l w h e n testing. 5 . F i l l t w o 1 2 - m L c e n t r i f u g e tubes w i t h 5 0 % (6 m L ) o f xylene o r gasoline. T o one t u b e a d d t w o d r o p s o f a 2 0 % k n o c k o u t d r o p s s o l u t i o n . A g i t a t e the s a m p l e w e l l , a n d fill b o t h tubes to 1 0 0 % w i t h c r u d e o i l to b e tested. M i x w e l l . S p i n i n c e n t r i f u g e for 5 m i n . R e c o r d o n test sheet the a m o u n t o f w a t e r a n d basic s e d i m e n t i n the t u b e w i t h o u t c h e m i c a l a n d the a m o u n t o f w a t e r i n the t u b e w i t h c h e m i c a l . 6. A d d 100 m L o f c r u d e o i l to test bottles. I f free w a t e r was present, a d d this to the test b o t t l e first, a n d t h e n fill to the 1 0 0 - m L m a r k w i t h c r u d e o i l (e.g., i f s a m p l e c o n t a i n e d 1 0 % free w a t e r , a d d 10 m L o f this w a t e r ) . 7. P l a c e the bottles i n a w a t e r b a t h a n d a l l o w 30 m i n to r e a c h the t e m p e r a t u r e at w h i c h the c h e m i c a l is i n j e c t e d . 8. A d d 2 % solutions o f the various c h e m i c a l s to the bottles. a. F r o m the d a i l y p r o d u c t i o n a n d a m o u n t o f c h e m i c a l u s e d , d e t e r m i n e the parts p e r m i l l i o n u s e d i n the sys tem.


365

366


b . O n the first test, r u n ratio tests at 0 . 5 , 0 . 7 5 , 1 , 1 . 5 , a n d 2 times the rate u s e d i n the p l a n t .


e. A f t e r e s t a b l i s h i n g the ratio that w i l l p r o d u c e accept able o i l , various c o m p o u n d s c a n be c h e c k e d at this ratio. R e m e m b e r that o i l m u s t b e treated i n the system a n d so must be treated i n the b o t t l e . 9. A g i t a t e the bottles a g i v e n n u m b e r o f times a n d place t h e m i n a w a t e r b a t h that is at the t e m p e r a t u r e o f the t r e a t i n g vessel. T h i r t y m i n u t e s after b e i n g p l a c i n g i n the w a t e r b a t h at t r e a t i n g vessel t e m p e r a t u r e , agitate the bottles a s e c o n d t i m e a n d r e t u r n to the w a t e r b a t h . N o t e s : a. T h i s is the i m p o r t a n t step; m a n y tests go astray h e r e . b . N o r m a l agitation is 200 times at c h e m i c a l i n j e c t i o n t e m p e r a t u r e , 10 to 100 times at t r e a t i n g vessel t e m p e r a t u r e . T h i s l e v e l is a g o o d starting place b u t s h o u l d not b e taken as a standard. c. C o r r e c t agitation is w h a t e v e r type o f agitation is re q u i r e d to r e p r o d u c e the system. d . I f results s i m i l a r to the p l a n t results c a n be o b t a i n e d i n the bottle test at the same c o n c e n t r a t i o n o f c h e m i c a l , the type o f agitation u s e d s h o u l d d u p l i c a t e the p l a n t results. e. O n the first test o f an e m u l s i o n , c h e m i c a l s k n o w n to have b e e n u s e d i n the system s h o u l d be t r i e d w i t h various types o f agitation. A test m e t h o d s h o u l d be selected f r o m these tests. I f n o n e o f the agitation v a r i a tions p r o d u c e c l e a n o i l at t w i c e the p l a n t c o n c e n t r a t i o n o r less, d i f f e r e n t types o f agitation s h o u l d b e t r i e d . 10. R e c o r d the a m o u n t o f w a t e r d o w n (i.e., settled at the bot tom) a. i m m e d i a t e l y b e f o r e agitation at t r e a t i n g vessel t e m p e r a t u r e a n d 1 h after. b . at the c o n c l u s i o n o f the test. c. at o t h e r times as d e s i r e d o r that are c r i t i c a l to the system. 11. T h e l e n g t h o f test t i m e is c a l c u l a t e d b y d i v i d i n g the d a i l y p r o d u c t i o n i n t o the capacity o f the t r e a t i n g vessel. 12. T a k e a d e e p g r i n d o n a l l bottles h a v i n g 7 5 % o r m o r e o f the total w a t e r d o w n . ( A d e e p g r i n d is a s a m p l e o f o i l t a k e n 1 0 - 1 5 m L above the w a t e r - o i l interface.)


10.

LEOPOLD


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Emulsions

a. P l a c e this s a m p l e i n a c e n t r i f u g e t u b e c o n t a i n i n g 5 0 % solvent. M i x w e l l a n d c e n t r i f u g e f o r 5 m i n . b. T o t a l the s u m o f basic s e d i m e n t a n d w a t e r . R e c o r d the total o n the test sheet. c. A d d t w o drops o f 2 0 % k n o c k o u t d r o p s s o l u t i o n , m i x w e l l , a n d c e n t r i f u g e f o r another 5 m i n . d . R e c o r d the a m o u n t o f w a t e r w i t h c h e m i c a l o n the test sheet. B e c a u s e o n l y 5 0 % o i l is u s e d , readings s h o u l d be doubled. e. F o r c r u d e oils o f d e n s i t y 986 kg/m o r m o r e (i.e., A P I gravity 12 or less), 9 m L o f solvent s h o u l d be a d d e d to c e n t r i f u g e tubes b e f o r e filling t h e m to 1 0 0 % w i t h o i l .


3

f.

C l e a n the s a m p l i n g d e v i c e w e l l after each use.

13. T a k e a m i x e d g r i n d o n any sample c o n t a i n i n g 1 % w a t e r o r less after h a v i n g a d d e d the k n o c k o u t d r o p s . ( A m i x e d g r i n d involves r e m o v i n g the e n t i r e p o r t i o n , o r as m u c h as p o s s i b l e , or the w a t e r that has separated d u r i n g the settling p e r i o d . ) a. R e m o v e a l l w a t e r f r o m the test b o t t l e , b e i n g c a r e f u l not to r e m o v e any o f the o i l at the i n t e r f a c e . b. A g i t a t e the b o t t l e 10 times, p o u r the contents i n t o a c e n t r i f u g e t u b e c o n t a i n i n g 5 0 % solvent, a n d m i x w e l l . c. C e n t r i f u g e a n d r e c o r d the total a m o u n t o f w a t e r a n d basic s e d i m e n t . d . A d d t w o drops o f 2 0 % k n o c k o u t drops s o l u t i o n , m i x w e l l , a n d r e c o r d the total a m o u n t o f w a t e r w i t h c h e m i cal. 14. T h e best c h e m i c a l is one that p r o d u c e s saleable o i l at the lowest c o n c e n t r a t i o n o n the d e e p g r i n d a n d that has v e r y little o r n o basic s e d i m e n t i n the m i x e d g r i n d . I f a m i x e d g r i n d has b e e n extracted p r o p e r l y , u p to 1 % o f the w a t e r m a y be d u e to free w a t e r r e m a i n i n g i n the test b o t t l e . A n y a m o u n t over this is p r o b a b l y d u e to w a t e r b e i n g h e l d u p i n the c r u d e o i l o r to a p o o r i n t e r f a c e . 15. M i s c e l l a n e o u s notes. a. I n c l u d e the c o m p o u n d s b e i n g u s e d i n the system a n d that y o u are t r y i n g to beat i n each test. b. A s testing progresses, r e d u c e the dosage i n o r d e r to select the best c o m p o u n d . O n l y the first test s h o u l d b e at a rate w h e r e the c o m p e t i t i v e p r o d u c t w i l l b a r e l y treat. Tests thereafter s h o u l d be at about a 2 0 % l o w e r ratio.


367

368


c. L o w - d e n s i t y c r u d e oils s h o u l d b e agitated f r e q u e n t l y to ensure u n i f o r m samples i n a l l bottles.


Observations. T h e f o l l o w i n g are the m o r e i m p o r t a n t characteristics a n d observations o f effective d e m u l s i f i c a t i o n bottle tests. R e g a r d i n g the s p e e d o f w a t e r d r o p o u t , i n a s a m p l e w i t h h i g h w a t e r v o l u m e , a c h e m i c a l o r d e m u l s i f i e r w i t h a fast w a t e r d r o p o u t is r e q u i r e d . W h e r e F W K O s are i n v o l v e d , the s p e e d o f w a t e r d r o p o u t m a y b e c o m e the most i m p o r t a n t factor. I n samples w i t h l o w - w a t e r v o l u m e , o r those w i t h m o r e t h a n n o r m a l r e s i d e n c e t i m e , the s p e e d o f w a t e r d r o p o u t m a y be o f lesser significance i n s e l e c t i n g the best d e m u l s i f i e r . N o n e t h e l e s s , i n a l l cases the s p e e d o f w a t e r d r o p o u t a n d v o l u m e s h o u l d be r e c o r d e d . T h e s p e e d o f w a t e r b r e a k is i m p o r t a n t a n d s h o u l d b e evaluated. It is s o m e t i m e s m i s l e a d i n g i n that a f a s t - w a t e r - d r o p o u t c h e m i c a l w i l l s o m e t i m e s q u i t t r e a t i n g b e f o r e o i l that meets p i p e l i n e specifications is o b t a i n e d . A g o o d r u l e o f t h u m b is to n e v e r use any faster w a t e r b r e a k t h a n is n e e d e d . A m o n g the o t h e r p r i n c i p a l items to observe, w h i c h have b e e n discussed i n the p r i n c i p a l text {see " I n t e r p r e t i n g R e s u l t s " ) , are c e n t r i f u g e cut, o i l c o l o r , interface, w a t e r q u a l i t y , a n d sludge.

Possible Errors.

E r r o r s s u c h as the f o l l o w i n g c a n o c c u r .

1. S a m p l i n g errors. A b a d sample is one that is not r e p r e s e n tative, is aged, o r is c o n t a m i n a t e d w i t h c h e m i c a l o r r e c y c l e d oil. 2. P o u r i n g i n t o s a m p l e bottles c a n cause errors i f u n e q u a l amounts o f e m u l s i o n sample are p o u r e d i n t o each bottle o r i f the sample characteristics vary a m o n g i n d i v i d u a l bottles (usually because o f the presence o f free water). 3. E r r o r s i n a d d i n g the c h e m i c a l solutions are a d d i n g the w r o n g m i x t u r e to a bottle o r a d d i n g an i n a p p r o p r i a t e a m o u n t o f s o l u t i o n to a b o t t l e . 4. M i s p l a c i n g o r c o n f u s i n g s a m p l e bottles. 5 . C e n t r i f u g i n g the s a m p l e i n s u f f i c i e n t l y . L o o k f o r e m u l s i o n i n the o i l phase a n d w a t e r a d h e r i n g to the sides o f the c e n t r i fuge t u b e . C h e c k f o r e m u l s i o n o r w a t e r d r o p l e t s o n the sides o f the t u b e after c e n t r i f u g i n g b y t u r n i n g the sample u p s i d e down. 6. D r a w i n g the interface m a t e r i a l o f f a l o n g w i t h the free w a t e r i n the s a m p l e b o t t l e .


10.

LEOPOLD


and Process-Stream

Emulsions

369

Appendix B: Pilot-Scaled Plant for Heavy-Oil Emulsions Treatment


T h e C a n a d a C e n t r e f o r M i n e r a l a n d E n e r g y T e c h n o l o g y ( C A N M E T ) is t h e m a i n research a n d t e c h n o l o g y d e v e l o p m e n t a r m o f E n e r g y , M i n e s , a n d Resources C a n a d a . A s o n e o f C A N M E T s five laboratory groups, C o a l R e search L a b o r a t o r i e s ( C R L ) p e r f o r m s a n d sponsors research to e n h a n c e C a n a d i a n industry's c o m p e t i t i v e p o s i t i o n . W i t h laboratories i n D e v o n , A l b e r t a , and S y d n e y ( N o v a Scotia), C R L is w e l l l o c a t e d t o serve b o t h c o a l a n d o t h e r i n d u s t r y clients, n o t a b l y those i n t h e r e c o v e r y a n d p r o c e s s i n g o f o i l sands a n d heavy o i l . C A N M E T has a p i l o t - s c a l e d e m u l s i o n - t r e a t m e n t p l a n t ( F i g u r e B . l ) available to i n d u s t r y f o r p i l o t - s c a l e d investigation o f h e a v y - o i l - b i t u m e n separation f r o m o i l - f i e l d - p r o d u c e d waters. T h i s f a c i l i t y is d e s i g n e d to p r o cess e m u l s i o n s at a t h r o u g h p u t b e t w e e n 130 L / h (20 barrels p e r day) a n d 4 6 0 L/h (70 barrels p e r day) f o r r a w b i t u m e n - o i l o f A P I gravity b e t w e e n 8 a n d 15 (i.e., density b e t w e e n 1014 a n d 9 6 6 kg/m , respectively). 3

T h e u n i t operations i n t h e m i n i p l a n t e m p l o y p r o v e n e m u l s i o n - t r e a t m e n t p r i n c i p l e s : free-water k n o c k o u t , d u a l - p o l a r i t y electrostatic treatment ( D P E T ) , h e a v y - o i l evaporation ( H O E ) d e h y d r a t i o n , a n d i n d u c e d gas flota t i o n ( I G F ) . T h e o v e r a l l process c o n f i g u r a t i o n p r o v i d e s m a x i m u m flexibility and allows f o r p e r f o r m a n c e e v a l u a t i o n o f units o n e i t h e r a n i n d i v i d u a l basis o r i n various c o m b i n a t i o n s . C A N M E T researchers, w o r k i n g i n close c o o p e r a t i o n w i t h i n d u s t r y , w i l l seek to achieve the f o l l o w i n g objectives: • d e t e r m i n e t h e parameters that g o v e r n o i l - w a t e r separation and that c a n b e extrapolated to larger i n d u s t r i a l plants • evaluate the p e r f o r m a n c e o f c o n v e n t i o n a l e m u l s i o n - t r e a t m e n t and separation e q u i p m e n t i n p r o c e s s i n g u n i q u e a n d d i f f i c u l t to-separate e m u l s i o n s • test a n d evaluate n e w a n d innovative o n - l i n e process m o n i t o r ing and control equipment • p e r f o r m c o m p o n e n t a n d m a t e r i a l balances associated w i t h var ious process streams • i d e n t i f y an i n t e g r a t e d strategy i n c o r p o r a t i n g e q u i p m e n t selec t i o n , p l a n t layout, a n d o p e r a t i n g strategy (e.g., t h e usage o f d e m u l s i f i e r s o r diluents) that w o u l d o p t i m i z e e m u l s i o n - b r e a k i n g operations f o r specific t r o u b l e s o m e e m u l s i o n s . L a b o r a t o r y facilities a n d bench-scale e q u i p m e n t are also available i n s u p p o r t o f the w o r k c o n d u c t e d i n t h e m i n i p l a n t . L a b o r a t o r y facilities are generN O T E : Hanna F . Sieben was a contributor to this appendix.




370

1

! I

ο

§0


10.

LEOPOLD


and Process-Stream

Emulsions

371

ally e m p l o y e d i n c o n d u c t i n g p r e c u r s o r y studies a i m e d at d e f i n i n g p r o s p e c tive o p e r a t i n g c o n d i t i o n s f o r the p i l o t - s c a l e d operations.

Description of Major Equipment. T h e p r i n c i p a l k i n d s o f e q u i p m e n t c o m p r i s i n g the e m u l s i o n - t r e a t m e n t m i n i p l a n t are b r i e f l y d e s c r i b e d i n T a b l e B . l , a n d t h e i r i n t e r r e l a t i o n s h i p is p r e s e n t e d s c h e m a t i c a l l y i n F i g u r e s


B.2 through B.7. Feed Tanks (T-l, T-1A). F i g u r e B . 2 depicts s c h e m a t i c a l l y the p r o cess flow a r o u n d b o t h e m u l s i o n f e e d storage tanks. T h e e m u l s i o n f e e d tank ( T - l ) is d e s i g n e d to h o l d 15,900 L (100 b b l ) . T h i s h o r i z o n t a l tank is e q u i p p e d w i t h t w o i d e n t i c a l mixers a n d a r e c i r c u l a t i o n l o o p to ensure that e m u l s i o n f e e d is w e l l m i x e d a n d consistent t h r o u g h o u t a t y p i c a l r u n . T h e tank is also e q u i p p e d w i t h a steam-plate c o i l - t a n k heater capable o f r a i s i n g the f e e d t e m p e r a t u r e to 70 °C (160 ° F ) w i t h a heat l o a d o f 18.3 k W (62,500 Btu/h) d u r i n g h e a t - u p . A f e e d p u m p ( P - l ) is e m p l o y e d e i t h e r to r e c i r c u l a t e the tank's contents o r to transfer it to the p l a n t f o r p r o c e s s i n g . T h i s p u m p , a progressive cavity type, is d e s i g n e d to h a n d l e l i q u i d s w i t h a viscosity range o f 500 to 10,000 mPa-s at a discharge pressure o f 1034 k P a (150 psi) a n d a m a x i m u m flow rate o f 680 L / h (3.0 U . S . gallons p e r m i n u t e o r U S G P M ) . T h e auxiliary f e e d tank ( T - 1 A ) holds 2 8 4 0 L (18 b b l ) . T h i s tank is e q u i p p e d w i t h a m i x e r a n d a h e a t i n g c o i l that is r a t e d at 48 k W (163,800 B t u / h) a n d is capable o f r a i s i n g t h e f e e d t e m p e r a t u r e to 150 °C (300 ° F ) i n 2 h ; n o r m a l o p e r a t i n g t e m p e r a t u r e is e x p e c t e d to be a p p r o x i m a t e l y 80 °C (176 ° F ) . A sensor i n the tank is u s e d as a l o w - l e v e l a l a r m to shut o f f the heater. T h e auxiliary f e e d p u m p ( P - l A ) is capable o f g e n e r a t i n g a discharge pressure o f 517 k P a (75 psi) a n d a m a x i m u m flow rate o f 1590 L / h (7.0 U S G P M ) . It m a y also b e u s e d to d e l i v e r f e e d to the o t h e r process units o r to r e c i r c u l a t e the tank's contents. I n s t r u m e n t a t i o n is i n p l a c e d o w n s t r e a m o f b o t h f e e d tanks to c o n t r o l the f e e d flow rate a n d to measure the t e m p e r a t u r e a n d p H o f the f e e d . C o n n e c t i o n s are also available f o r the a d d i t i o n o f d e m u l s i f i e r o r diluent. Free-Water Knockout (FWKO, V-l). F i g u r e B . 3 is a process flow schematic o f the free-water k n o c k o u t unit's o p e r a t i o n . T h e F W K O vessel is a three-phase h o r i z o n t a l separator d e s i g n e d to h o l d 940 L (5.9 b b l ) a n d to operate safely at pressures u p to 517 k P a (75 psi) at 177 °C (350 ° F ) . E m u l s i o n f e e d c o n t a i n i n g greater t h a n 1 5 % (v/v) w a t e r enters the F W K O , first passing t h r o u g h a b a f f l e d " c o a l e s c i n g z o n e " , a n d t h e n i n t o a q u i e s c e n t separation area w h e r e free w a t e r collects i n the b o t t o m o f the vessel a n d any e v o l v e d gas leaves f r o m the top o f the vessel t h r o u g h a 304 SS (stainless steel) w i r e - m e s h mist e l i m i n a t o r . T h e r e m a i n i n g e m u l s i o n flows o v e r a w e i r i n t o the o i l r e c o v e r y side o f the vessel. I n s t r u m e n t a t i o n o n the u n i t i n c l u d e s pressure a n d t e m p e r a t u r e m e a -


372


Table B . l . Major Equipment List Tag

Name

Description

F e e d Tanks (Figure B.2) HT-1

F e e d tank heater

HT-1A MX-le

MX-1A

Auxiliary feed tank heater F e e d tank mixer (east end) Feed tank mixer (west end) Auxiliary feed tank mixer

P-l

Feed pump

P-l A

Auxiliary feed pump

T-l

Feed tank

T-1A

Auxiliary feed tank


MX-lw

Double-embossed plate eoil; 25-kW heating duty with steam 48 k W ; 460 V A C ; three-phase; 60 H z 1.5 hp; 575 V A C ; three-phase; 60 H z ; 1720 rpm; dual impeller at 350 rpm 1.5 hp; 575 V A C ; three-phase; 60 H z ; 1720 rpm; dual impeller at 350 rpm 1.5 hp; 460 V A C ; three-phase; 60 H z ; 1720 rpm; dual impeller at 350 rpm eccentric screw; 680 L/h at 1034 kPa (250 rpm); 1.5 hp; 460 V A C ; three-phase; 60 H z ; 1720 rpm Rotary vane; 1560 L/h at 517 kPa (40 rpm); 2.0 hp; 460 V A C ; three-phase; 60 H z ; 1140 rpm Horizontal; 2.4 m o.d. x 3.7 m long; 15,900-L capacity Horizontal; 1.2 m o.d. x 2.4 m long; 2840-L capacity

Free-Water Knockout (Figure B.3) V-l

F W K O vessel

Horizontal; three-phase separator; 0.8 m o.d. x 2.4 m long; 940-L capacity; M A W P 517 kPa at 177 °C c/w inlet flow baffles, coalescing plate section, oil overflow wire, 304 S S gas outlet mist eliminator, liquid outlet vortex breakers

Dual-Polarity Electrostatic Treater (Figure B.4) HT-3 MX-2 P-7

D P E T inlet heaters D P E T inlet mixer D P E T feed pump

V-2

D P E T vessel

3-20 k W ; 480 V A C ; three-phase; 60 H z 38-mm helical coil in-line mixer Progressing cavity; 570 L/h at 517 kPa (590 rpm); 0.5 hp; 480 V A C ; three-phase; 60 H z ; 1140 rpm Vertical; 1.2 m o.d. x 1.8 m high; 1720-L capacity; M A W P 517 kPa at 150 °C; c/w 2 k V A ; 480 V A C ; singlephase; 60 H z primary & 9.0, 12.5, 16.5, and 23.0 k V D C selectable secondary transformer

Heavy-Oil Evaporation Dehydrator (Figure B.5) HT-4

H O E inlet preheater

Horizontal; shell-tube heat exchanger; 56-kW process duty with superheated steam at 690 kPa; M A W P : shell (steam) 1034 kPa at 176 °C, tube (emulsion) 1034 kPa at 149 °C



10.

LEOPOLD


and Process-Stream

Emulsions

373

Tag

Name

Description

HT-5

Treated oil coolervapor condenser

P-6

H O E oil discharge pump

P-8

Skimmer feed pump

V-3

H O E vessel

V-5

L i q u i d accumulator

V-6

Skimmer vessel

Fin-fan-tube heat exchanger; cooling duty 20 k W ; condensing duty 44 k W ; M A W P : 1034 kPa at 177 °C (oil), 1034 kPa at 149 °C (vapors) Gear; 684 L/h at 345 kPa (590 rpm); 1.0 hp; 460 V A C ; three-phase; 60 H z ; 1725 rpm Gear; 342 L/h at 345 kPa (590 rpm); 0.25 hp; 460 V A C ; three-phase; 60 H z ; 1725 rpm Horizontal; 1.4 m i.d. x 2.1 m long; 3150-L capacity; M A W P 345 kPa at 177 °C Vertical; surge vessel; 0.2 m o.d. x 0.8 m high; 15-L capacity; M A W P 517 kPa at 65 °C Vertical; two-phase separator; 0.2 m o.d. x 1.5 m high; 30-L capacity; M A W P 517 kPa at 65 °C

Treated-Oil-Bitumen Tanks (Figure B.6) HT-2 HT-2A MX-2 P-2

P-2A T-2 T-2A

Treated-oil tank heater Auxiliary treated-oil tank heater Treated-oil tank mixer Treated-oil recirc. pump Auxiliary treated-oil recirc. pump Treated-oil tank Auxiliary treated-oil tank

Double-embossed plate coil; 1140 kPa; 25 k W heat load 20 k W ; 460 V A C ; three-phase; 60 H z 3.0 hp; 575 V A C ; three-phase; 60 H z ; 350 rpm; dual impeller Eccentric screw; 680 L/h at 1034 kPa; 1.5 hp; 460 V A C ; three-phase; 60 H z Rotary vane; 1560 L/h at 517 kPa; 2.0 hp; 460 V A C ; three-phase; 60 H z Vertical; 2.9 m o.d. x 1.9 m high; 11,130-L capacity Horizontal; 1.2 m o.d. x 2.4 m long; 2840-L capacity

Induced Gas Flotation (Figure B.7) P-3

Produced water pump

T-3

Produced water tank

V-4

I G F unit

0.25 hp; 230 V A C ; one-phase; 60 H z ; 1725 rpm Vertical; 0.9 m o.d. x 1.5 m high; 950-L capacity Four-cell flotation unit; 2280 L/h capacity at 25 °C; c/w one froth skimmer and disperser-impeller per cell



Τ-1

MX-ΙΑ

/

-

P-1A

Steam Condensate

'FT Λ

Figure B.2. Schematic flow sheet of feed tanks.

P-l

MX-1

T-1A

Auxiliary feed tank

OkD

Feed tank

MX-1

VENT

48 kW O HT-1A Q -

—. )

VENT

(PH


Emulsion to FWKO, DPET or HOE

Η

C/3

U C

Μ

r

Μ Η » Ο

*d

Μ

Η

ο ζ

10.

LEOPOLD


and Process-Stream

Emulsions

Gas

Vent Emulsion from


T - l

Feed

and/or

Tank Τ-1

a

375

FWKO

5r\

(Mb CI

Water Produced

T-3

Δ

to Tank

Λ

Δ

D""

Oil to e i t h e r DPET o r HOE

Figure B.3. Schematic flow sheet of free-water

knockout.

sûrement; l e v e l c o n t r o l ; o i l , w a t e r , a n d gas outlet flow-rate m e a s u r e m e n t ; a n d d e t e r m i n a t i o n o f t h e o u t g o i n g o i l a n d b i t u m e n density. T h e w a t e r l e a v i n g the F W K O is sent d i r e c t l y t o the i n d u c e d gas flotation ( I G F , V - 4 ) u n i t , a n d t h e e x i t i n g e m u l s i o n m a y b e sent t o e i t h e r t h e d u a l - p o l a r i t y e l e c trostatic treater ( D P E T , V - 2 ) o r t h e h e a v y - o i l e v a p o r a t i o n ( H O E , V - 3 ) d e h y drator f o r f u r t h e r treatment. D e m u l s i f i e r , d i l u e n t , o r b o t h m a y also b e a d d e d to t h e e x i t i n g e m u l s i o n stream. Dual-Polarity Electrostatic Treater (DPET, V-2). T h e D P E T (a C - E N a t c o v e r t i c a l V F H - C W W m o d e l ) process flow d i a g r a m is p r e s e n t e d i n F i g u r e B . 4 . T h e p u r p o s e o f this v e r t i c a l vessel is t o p r o v i d e f o r b o t h freew a t e r r e m o v a l a n d coalescence o f e n t r a i n e d w a t e r d r o p l e t s . W i t h i n t h e m i n i p l a n t ' s c o n f i g u r a t i o n , i t p r i n c i p a l l y serves as a p r i m a r y t r e a t i n g stage f o l l o w e d b y t h e H O E u n i t as t h e final treating step. N o n e t h e l e s s , e i t h e r t r e a t i n g u n i t m a y b e o p e r a t e d i n d e p e n d e n t l y o f the o t h e r i n a c h i e v i n g t h e u l t i m a t e goal, a t r e a t e d o i l - b i t u m e n m e e t i n g m a r k e t i n g specifications: a maximum of 0.5% B S & W . T h e D P E T is d e s i g n e d to h o l d 1720 L (10.8 b b l ) a n d operates safely at pressures u p to 5 1 7 k P a (75 psi) a n d t e m p e r a t u r e s u p to 150 °C (300 ° F ) . T h e a p p l i c a t i o n o f a high-voltage, d u a l - p o l a r i t y e l e c t r i c p o t e n t i a l to electrodes i n s i d e the vessel is u s e d to coalesce a n d r e m o v e s m a l l droplets o f w a t e r i n the o i l e m u l s i o n . T h e o i l s h o u l d b e degassed a n d have a w a t e r content less t h a n 1 5 % b e f o r e e n t e r i n g t h e vessel; h o w e v e r , t h e treater does have t h e c a p a b i l i t y f o r free-water k n o c k o u t . P r e h e a t e d e m u l s i o n is p u m p e d i n t o t h e b o t t o m p o r t i o n o f the vessel, b e l o w the electrodes, w h e r e free w a t e r gener ated b y h e a t i n g o r c h e m i c a l treatment m a y d r o p o u t . A s m o r e e m u l s i o n is


376

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

Wet Oil from FWKO

Wet Oil from F e e d l

Tank


and/or

-φ—-g—

2kVA Trans former 1 1

L DPET V-2

HT-3 *\

Τ-1"Π^Γ T-1À

MX-2

P-7

Sludge to Disposal

I

^

J

Wet Oil to HOE Water to Produced Water Tank T - 3

Figure B.4. Schematic flow sheet of DPET treater.

i n t r o d u c e d to the vessel, the e m u l s i o n rises u n t i l i t c o m e s i n t o contact w i t h the electrodes. T h e D P E T ' s electrodes are i n the f o r m o f c o n c e n t r i c c y l i n d r i c a l plates s u s p e n d e d f r o m the top o f the vessel a n d are c o n n e c t e d to a high-voltage t r a n s f o r m e r s u c h that adjacent plates are g i v e n opposite charges. A s the o i l passes t h r o u g h the electrodes, w a t e r d r o p l e t s are i n f l u e n c e d b y the field to create a s i n u s o i d a l m i g r a t i o n b e t w e e n plates o f o p p o s i t e charge. T h i s m o t i o n serves t w o p u r p o s e s : to restrict the u p w a r d flow o f the w a t e r i n r e l a t i o n to the o i l ; a n d to e n h a n c e the rate o f c o l l i s i o n o f w a t e r d r o p l e t s , w h i c h are d i s t o r t e d to f o r m d i p o l e s u n d e r the e l e c t r i c field, a n d t h e r e b y increase the rate o f coalescence. C l e a n o i l leaves f r o m the t o p o f the vessel, w h i l e w a t e r is d r a i n e d out f r o m the b o t t o m . I n s t r u m e n t a t i o n available o n this u n i t p e r m i t s p r e s s u r e a n d t e m p e r a t u r e m e a s u r e m e n t o f b o t h the f e e d a n d vessel c o n d i tions a n d the t r e a t e d o i l a n d o u t l e t w a t e r flow rates. T h e t r e a t e d o i l - b i t u m e n , w h i c h s h o u l d c o n t a i n less t h a n 0 . 5 % water, is t h e n t r a n s f e r r e d to the t r e a t e d o i l storage tank (T-2). T h e e x i t i n g w a t e r - r i c h s t r e a m is p u m p e d to a p r o d u c e d w a t e r storage tank (T-3) f r o m w h i c h it m a y be p u m p e d to the I G F . Heavy-Oil Evaporation Dehydrator (HOE, V-3). Figure B.5 illus trates the process flow schematics f o r the H O E u n i t . T h i s h o r i z o n t a l vessel c a n serve as e i t h e r a n alternative to the D P E T ( s h o u l d the o i l - b i t u m e n - r i c h stream e x i t i n g the F W K O c o n t a i n less t h a n 1 0 % water) o r as a secondary treater to the D P E T . T h e H O E u n i t is d e s i g n e d to process an e m u l s i o n c o m p o s e d o f o i l - b i t u m e n (70%), w a t e r (10%), a n d d i l u e n t (20%) at a c o m b i n e d rate o f 460 L / h (70 barrels p e r day) f o r r a w o i l - b i t u m e n o f A P I gravity


10.

LEOPOLD


and Process-Stream

377

Emulsions

b e t w e e n 8 a n d 15 (i.e., density b e t w e e n 1014 a n d 0.966 k g / m , respectively). C h a r t I s u m m a r i z e s the unit's process d e s i g n basis. 3

T h e e m u l s i o n f e d to the H O E c a n be p r e h e a t e d to a p p r o x i m a t e l y 125 °C (257 ° F ) b y a s h e l l - a n d - t u b e heat exchanger ( H T - 4 ) . T h e h o t e m u l s i o n is t h e n f e d i n t o the evaporator vessel (V-3), t h r o u g h a spreader, o n t o a w i d e , shallow tray. T h e spreader ensures that a t h i n u n i f o r m coat o f o i l is d e p o s i t e d


onto the tray, w h i c h is s l o p e d d o w n w a r d a n d is h e a t e d f r o m b e l o w b y steam coils. A s the e m u l s i o n runs d o w n the tray, water, l i g h t ends, a n d any r e m a i n i n g d i l u e n t are evaporated. T h i s process is r e p e a t e d c o n s e c u t i v e l y o n t w o a d d i t i o n a l trays. T h e treated o i l - b i t u m e n is c o l l e c t e d i n the b o t t o m o f the vessel, w h i l e the vapors exit at the t o p . T h e contact t e m p e r a t u r e i n the vessel is a p p r o x i mately 150 °C (300 ° F ) , a n d the total area o f the t h r e e trays is a p p r o x i m a t e l y 3.34 m (36 s q ft). T h e treated o i l , w h i c h s h o u l d c o n t a i n less t h a n 0 . 5 % (v/v) water, is t h e n p u m p e d f r o m the b o t t o m o f the evaporator, f a n - c o o l e d a n d sent to the t r e a t e d - o i l storage tank (T-2). T h e w a t e r - d i l u e n t vapors are also f a n - c o o l e d , sent to an a c c u m u l a t o r , a n d t h e n t r a n s f e r r e d to a gravity separa tor f o r d i l u e n t recovery. W a t e r is sent to the p r o d u c e d - w a t e r tank (T-3) b e f o r e b e i n g p r o c e s s e d t h r o u g h the I G F u n i t . T h e i n s t r u m e n t a t i o n o n this u n i t i n c l u d e s pressure a n d t e m p e r a t u r e c o n t r o l o f the p r e h e a t e d e m u l s i o n ; pressure a n d t e m p e r a t u r e m e a s u r e m e n t 2

Wet Oil f r o m Feed Tank(s), FWKO, Produced OU Tank(s)

Oil to Produced Oil Tank T - 2 and/or T-2À

Solvent Recovery

Water to Produced Water Tank T-3 Figure B.5. Schematic flow sheet of HOE treater.


378


Chart I. Heavy-Oil Evaporation Dehydrator ( H O E ; V-3) Process Design Basis Process Flow to Preheater: at 40 °C (104 °F) to 127 °C (260 °F) Oil-bitumen (1,020 kg/m ): 324 L/h (729 lb/h) Water (1,000 kg/m ): 42 L/h (104 lb/h) Diluent (800 kg/m ): 93 L/h (163 lb/h) • pressure: 207 kPag (30 psig) • water evaporates i n the exchanger • 95% of diluent flashes in the exchanger • process heating duty: 56 k W (192 000 Btu/h) 3

3


3

Evaporator: contact temperature, 149 °C (300 °F) • • • •

remaining 5 % of diluent flashes steam is superheated 2% (v/v) of raw-oil-bitumen flashes tray duty: 7 k W (25 000 Btu/h)

Vapor Condenser: from 108 °C (227 °F) at 34 kPag (5 psig) to 38 °C (100 °F) • • • • • •

condense 46 kg/h (102 lb/h) steam condense 74 kg/h (163 lb/h) diluent condense 7 kg/h (15 lb/h) produced condensate cool all products to 38 °C (100 °F) condensing duty: 44 k W (149 000 Btu/h) based upon 27 °C (80 °F) ambient air cooling

Oil Cooler: from 149 °C (300 °F) to 38 °C (100 °F) • cool 318 L/h (714 lb/h) oil—bitumen • cooling duty: 20 k W (69 300 Btu/h) Recovered Products: at 38 °C (100 °F) and 345 kPag (50 psig) Oil-bitumen (1,020 kg/m ): 317 L/h (714 lb/h) Water (1,000 kg/m ): 41 L/h (102 lb/h) Diluent (800 kg/m ): 102 L/h (178 lb/h) • based upon 100% mass transfer equations • treated-oil—bitumen contains less than 0.5% (v/v) BS&W 3

3

3

a n d l e v e l c o n t r o l i n the evaporator vessel, the a c c u m u l a t o r , a n d the gravity separator; a n d m e a s u r e m e n t o f the o u t l e t flow rates o f the o i l , water, a n d diluent. Treated-Oil Tanks (T-2 and T-2A). T h e flow schematics f o r b o t h t r e a t e d o i l - b i t u m e n storage tanks are i l l u s t r a t e d i n F i g u r e B . 6 . T h e treated o i l - b i t u m e n storage tank (T-2) h o l d s 11,130 L (70 b b l ) . T r e a t e d o i l - b i t u m e n f r o m e i t h e r the D P E T o r the H O E treater can be f e d to this tank. T h e



Steam Condensate·

Vent

20 k W Q HT-2AQ-

Vent

{Q97J

FV 002

Wet Oil HOE

S-®-Nh- s

Treated Oil from HOE

P-2 Figure B.6. Schematic flow sheet of treated-oil tanks.

8

T-2

Treated oil tank

") T-2À

_

Auxiliary treated oil tank

BSW-097

Treated Oil from DPET


380



t r e a t e d - o i l p u m p (P-2), w h i c h is i d e n t i c a l to the e m u l s i o n f e e d p u m p ( P - l ) , c a n also be e m p l o y e d to (1) transfer any o f f - s p e c i f i c a t i o n (i.e., " w e t " ) o i l b i t u m e n b a c k to the H O E ( w i t h the o p t i o n o f passing i t t h r o u g h the a u x i l i a r y t r e a t e d o i l tank ( T - 2 A ) w h e r e b l e n d i n g w i t h d i l u e n t c a n occur) f o r f u r t h e r p r o c e s s i n g o r (2) r e c i r c u l a t e the contents o f tank T - 2 . T a n k T - 2 is also e q u i p p e d w i t h a n e l e c t r i c m i x e r a n d a steam-plate c o i l - t a n k heater i d e n t i c a l to the u n i t i n s t a l l e d i n the f e e d tank ( T - l ) . T h e a u x i l i a r y t r e a t e d - o i l tank ( T - 2 A ) h o l d s 2840 L (18 b b l ) . T h e i n l e t , w h i c h c a n accept flow f r o m the D P E T a n d the H O E o r the larger T - 2 tank, is e q u i p p e d w i t h a n i n - l i n e B S & W m e t e r to m o n i t o r the w a t e r content o f the t r e a t e d - o i l - b i t u m e n s t r e a m . I f the w a t e r content is n o t s u f f i c i e n t l y l o w , the p r o d u c t m a y be r e c y c l e d b a c k to the H O E treater. T h i s tank also has a heater a n d a l e v e l sensor to act as a l o w - l e v e l a l a r m to t u r n o f f the heater. A d d i t i o n a l i n s t r u m e n t a t i o n o n the u n i t allows f o r m e a s u r e m e n t o f t e m p e r a t u r e a n d pressure i n s i d e the vessel, flow-rate c o n t r o l o f the o f f - s p e c i fication o i l , a n d m e a s u r e m e n t o f r h e o l o g i c a l p r o p e r t i e s o f the o f f - s p e c i f i c a tion and produced oil. Induced Gas Flotation (IGF, V-4). F i g u r e B . 7 s c h e m a t i c a l l y depicts t h e process flow f o r the I G F u n i t . T h i s u n i t processes a l l the w a t e r streams g e n e r a t e d b y the o t h e r u n i t operations ( F W K O , D P E T , a n d H O E ) i n the m i n i p l a n t b y m o v i n g the r e m a i n i n g o i l f r o m i t p r i o r to d i s p o s a l o r f u r t h e r t r e a t m e n t . T h e o i l i n the w a t e r collects at the surface o f these b u b b l e s a n d is d r a w n out o f the b u l k l i q u i d as the b u b b l e s rise to the t o p . A n o i l y f o a m

Oily Water f r o m b o t h DPET a n d HOE

O i l y Water f r o m FWKO

3

ι

LCV920 Water to disposal

Prod. Water Tank T-3

P-3

Oil

Figure B.7. Schematic flow sheet of induced gas flotation.


10.

LEOPOLD


and Process-Stream

Emulsions

381

f o r m s at the t o p o f the cells a n d is s k i m m e d o f f a n d c o l l e c t e d . T h e o i l c o n t e n t


o f the w a t e r m a y b e r e d u c e d f r o m as h i g h as 5 0 0 0 p p m to less t h a n 10 p p m . I n s t r u m e n t a t i o n o n the u n i t consists o f a magnetic flowmeter to m e a sure f e e d rate a n d a l e v e l c o n t r o l l e r to m a i n t a i n p r o p e r l i q u i d h e i g h t i n the flotation cells. Demulsifier and Diluent Injection. T h e system available f o r d e m u l s i f i e r a d d i t i o n consists o f a f e e d p u m p a n d flexible hose c o n n e c t i o n s that a l l o w f o r c h e m i c a l i n j e c t i o n at various process p o i n t s . T h e m a x i m u m flow rate generated b y the d e m u l s i f i e r f e e d p u m p is 6.5 L / h (1.7 U . S . gallons p e r h o u r o r U S G P H ) . T h e d i l u e n t i n j e c t i o n system is i d e n t i c a l except that the f e e d p u m p m a y d e l i v e r u p to 76 L / h (20 U S G P H ) . Computer Monitoring System. A data a c q u i s i t i o n system is u s e d to m o n i t o r a n d l o g 27 various m e a s u r e m e n t s f r o m the m i n i p l a n t . T h e signals f r o m the i n s t r u m e n t s are f e d i n t o an a n a l o g - t o - d i g i t a l c o n v e r t e r , a n d the r e s u l t i n g d i g i t a l signal is c o n v e r t e d i n t o an a p p r o p r i a t e value b a s e d u p o n a scale factor for its respective i n s t r u m e n t .

Data and Results. Feed Characteristics. T o date, p l a n t test runs have b e e n c o n d u c t e d w i t h a b i t u m e n - i n - w a t e r e m u l s i o n c o m p r i s i n g 2 8 . 8 % (v/v) b i t u m e n o f 9 A P I gravity (i.e., density o f 1007 kg/m ). T h i s e m u l s i o n was p r o d u c e d at an i n situ o i l - s a n d t h e r m a l r e c o v e r y p r o j e c t i n n o r t h e r n A l b e r t a . A p p r o x i m a t e l y 11.1 m (70 b b l ) o f e m u l s i o n was treated. S e p a r a t i o n o f the b i t u m e n f r o m the w a t e r phase b y gravity segregation was not a p r a c t i c a l s o l u t i o n i n this case because o f the slight d i f f e r e n c e i n the t w o phases' densities (1010 a n d 1002 kg/m f o r b i t u m e n a n d water, respectively). C o n s e q u e n t l y , d e t e r m i n a t i o n o f stream c o m p o s i t i o n t h r o u g h c e n t r i f u g a t i o n (i.e., A S T M D 96, " S t a n d a r d T e s t M e t h o d f o r W a t e r a n d S e d i m e n t i n C r u d e O i l s " ) d i d not g e n e r a l l y p r o d u c e r e l i a b l e results. D e a n - S t a r k analysis, w h i c h was also e m p l o y e d , p r o v e d to be m o r e r e l i a b l e i n d e t e r m i n i n g b i t u m e n , water, a n d solids frac tions i n the e m u l s i o n . H o w e v e r , whereas the results f r o m c e n t r i f u g a t i o n are v i r t u a l l y i m m e d i a t e , D e a n - S t a r k analysis r e q u i r e s r o u g h l y 24 h . T a b l e B . 2 s u m m a r i z e s the c o m p a r a t i v e results o f b o t h m e t h o d s f o r a set o f e m u l s i o n f e e d samples. 3

3

3

Plant Operation Performance. T a b l e B . 3 s u m m a r i z e s the targeted flow c o m p o s i t i o n s f o r the i n t e g r a t e d p l a n t o p e r a t i o n o f a l l f o u r process units r e q u i r e d to treat the a f o r e m e n t i o n e d e m u l s i o n f e e d to acceptable p r o d u c t c o m p o s i t i o n s : T h e b i t u m e n ( d i l u t e d w i t h naphtha) must m e e t the p e t r o l e u m m a r k e t i n g r e q u i r e m e n t s o f n o m o r e t h a n 0 . 5 % B S & W ; for b o t h e c o n o m i c a l


382


a n d e n v i r o n m e n t a l reasons, t h e r e c o v e r e d p r o d u c e d w a t e r s h o u l d c o n t a i n n o m o r e t h a n 10 p p m o f b i t u m e n - o i l . T a b l e B . 4 represents a c o m p o s i t e mass balance f o r t h e e n t i r e p i l o t - p l a n t o p e r a t i o n . A n y differences i n t h e totals are d i r e c t l y attributable to s a m p l i n g e r r o r , e x p e r i m e n t a l e r r o r i n c o n d u c t i n g t h e D e a n - S t a r k analysis, a n d the flow m e a s u r e m e n t e r r o r . Table B.2. Dean-Stark Analysis vs. Centrifuge Comparative Results of Bitumen Cut


Centrifugation Method

Dean-Stark Analysis

Sample Number

% Difference

1 2 3 4 5 6 7 8

30.37 28.67 24.49 37.40 26.59 27.23 25.33 26.56

30.62 30.02 17.69 18.29 29.91 27.99 32.54 27.19

0.83 4.59 32.26 68.62 11.77 2.77 24.93 2.33

Avg.

28.33

26.78

6.71

NOTE: All values are percent of total weight. Table B . 3 . Typical Results of Emulsion-Treatment Miniplant Dean-Stark Analysis Process Stream

Emulsion Feed

DPET Oil Outlet

FWKO Oil Outlet

IGF Inlet

HOE Oil Outlet

Original Sample (g)

450.0

434.0

421.5

452.5

435.0

Bitumen (g) Water (g) Solids (g) Total Recovered (g)

129.0 319.1 0.4 448.5

126.0 67.0 0.3 193.3

371.5 48.3 1.0 420.8

448.6 2.2 0.1 450.9

5.0 427.8 0.3 433.1

Recovery (%)

99.67

44.55

99.83

99.64

99.56

Bitumen C u t (%) Water Cut (%) Solids C u t (%)

28.76 71.15 0.09

65.17 34.65 0.18

88.28 11.48 0.24

99.49 0.49 0.02

1.15 98.78 0.07

Table B.4. Typical Example of Emulsion-Treatment Miniplant Mass Balance Bitumen Process Emulsion feed Bitumen outlet Water outlet Total outlet Mass balance difference

*g 3,202 3,176 23 3,199 -3

% 28.8 99.4 0.3 28.7 -0.1

Water *B 7,893 16 7,910 7,926 33

Solids

% 71.1 0.5 99.6 71.2 0.4

h 9 4 6 10 1

% 0.1 0.1 0.1 0.1 11.1

Total 11,104 3,196 7,939 11,135 31 (0.3%)


10.

LEOPOLD


and Process-Stream

Emulsions

383

Acknowledgment T h a n k s to K . C . M c A u l e y f o r p r e p a r a t i o n o f t h e

figures.


References 1. Strassner, J. E. J. Pet. Technol. 1968, 3, 303-312. 2. Bessler, D . U . Demulsification; Petrolite Corporation: St. Louis, M O , 1984. 3. Arnold, K . ; Stewart, M . Surface Production Operations: Design of Oil-Handling Systems and Facilities; G u l f Publishing Company: Houston, T X , 1986; V o l . 1. 4. Bessler, D . U . Waste Oil Treatment; Petrolite Corporation: St. Louis, M O , 1981. 5. Claassen, E . J.; Harlan, J. T.; Trial, C . B. Emulsions; Champion Chemicals: Houston, T X , 1976. 6. "Conventional O i l Production Facilities: Selection and Design Concepts"; pre sented by the Petroleum Industry Training Service, Calgary, Alberta, Canada, 1990. 7. Chilingarian, G . V . ; Robertson, J. O . , Jr.; Kumar, S. Surface Operations in Petroleum Production; Developments i n Petroleum Science, 19A; Elsevier: Amster dam, Netherlands, 1987; V o l . I. 8. “WEMCO Depurator 1+1 Flotation Machine”; Technical Bulletin N o . F8-B5(885-5M), W E M C O : Sacramento, C A , 1985.

Additional Reading Angelidou, C . ; Keshavarz, E . ; Richardson, M . J.; Jameson, G . J. Ind. Eng. Chem. Process Des. Dev. 1977, 16(4), 436-441. Arnold, K.; Stewart, M., Jr. World Oil 1985, 2, 31-36. Arnold, K.; Stewart, M., Jr. W o r l d O i l 1985, 5, 91-98. Arnold, K . E.; Koszela, P. J. SPE Prod. Eng. 1990, 5(1), 59-64. Bessler, D . U . Demulsification of Enhanced Recovery Produced Fluids; Corporation: St. Louis, M O , 1984.

Petrolite

Bradley, B. W . Oil Gas J. 1985, 12, 42-45. Brunsmann, J. J.; Cornelissen, J.; Eilers, H . J. Water Pollut. Control Fed. 1962, 34, 44-54. Donaldson, E . C . ; Chilingarian, G . V . ; Yen, T . F . Enhanced Oil Recovery; Develop ments i n Petroleum Science, 19A; Elsevier: Amsterdam, Netherlands, 1985; V o l . I. Powers, M . L . Presented at the 63rd Annual Technical Conference of the Society of Petroleum Engineers, Houston, T X , October 2-5, 1988, paper S P E 18205; pp 241-252. Sport, M . C . J. Pet. Technol 1970, 8, 918-920.

RECEIVED

for review December 18, 1990. ACCEPTED revised manuscript M a y 23,

1991.


Emulsions Fundamentals and Applications in the Petroleum Industry

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