Chapter 28 Laboratory Apparatus for Study of the Flow of Foam in Porous Media Under Reservoir Conditions 1
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C. W. Nutt,1,2 R. W. Burley,1,2 A. J . MacKinnon, and P. V. Broadhurst 1Heriot-Watt University, Edinburgh, United Kingdom IMOD Processes Ltd., Linlithgow, West Lothian, E H 49 7JU, United Kingdom ICI Chemicals and Polymers Ltd., Wilton, Cleveland, Great Britain 2
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The numerous previous studies of the flow of foam in porous media and of its application for improving the displacement of o i l from such media, have almost always been conducted under ambient conditions of temperature and pressure; there have been very few reports of laboratory studies under reservoir conditions. Although many interfacial properties are known to be temperature dependant, little attention has been paid to the influence of temperature upon the properties of foam. Furthermore, the rheological properties of foams, and their effectiveness for the displacement of o i l are strongly dependant upon foam quality, which is in turn strongly dependant upon the pressure to which the foam is subjected. This paper describes an apparatus for the determination of the viscous properties of foam, and for the measurement of its a b i l i t y to displace o i l from porous media, under reservoir conditions, and w i l l report and discuss some of the preliminary results obtained. It i s now well e s t a b l i s h e d t h r o u g h s t u d i e s i n many l a b o r a t o r i e s t h r o u g h o u t t h e w o r l d t h a t foam injection shows c o n s i d e r a b l e promise a s an a g e n t f o r the improvement o f o i l r e c o v e r y from watered-out porous media, and f o r t h e d i v e r s i o n o f the flow o f other o i l - d i s p l a c i n g f l u i d s from more p e r m e a b l e paths into less permeable paths i n t h e medium* ). W h i l s t the reasons f o r the effectiveness o f foam f o r these purposes are not completely c l e a r , the explanation i s t h o u g h t t o l i e i n t h e b e h a v i o u r o f t h e foam lamellae 1
0097-6156/89/0396-0518$06.00A) o 1989 American Chemical Society
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d u r i n g t h e i r m o t i o n t h r o u g h t h e p o r e s t r u c t u r e , and t o derive from the rheological properties of the i n t e r f a c i a l l a y e r s o f the l a m e l l a e ( » > . Comparison o f t h e b e h a v i o u r o f foams f o r m e d by s u r f a c t a n t s w h i c h a r e t y p i c a l o f t h e main c l a s s e s o f c o m m e r c i a l l y available r e a g e n t s has r e v e a l e d t h a t t h e e f f e c t i v e n e s s o f a foam depends s t r o n g l y on t h e c h e m i c a l n a t u r e o f t h e f o a m i n g a g e n t as w e l l as on t h e q u a l i t y o f t h e foaro< >. Now i t has been the u s u a l p r a c t i c e t o c o n d u c t laboratory tests of the effectiveness of foam to improve o i l recovery from porous media at room t e m p e r a t u r e and a t m o s p h e r i c p r e s s u r e . Y e t i t i s well established that the stability of foams often diminishes with increase of temperature, and indeed the ability o f aqueous s o l u t i o n s o f many s u r f a c t a n t s to form foams disappears completely at a characteristic temperature which is less than the t e m p e r a t u r e w i t h i n many deep o i l fields. Moreover, since t h e e f f e c t i v e n e s s o f a foam t o d i s p l a c e o i l , o r to s e l e c t i v e l y d i v e r t flow, are functions of foam quality and since t h e q u a l i t y o f a foam i s s t r o n g l y dependant upon the pressure, the selection of a foaming agent f o r EOR a p p l i c a t i o n s t h e r e f o r r e q u i r e s an u n d e r s t a n d i n g o f t h e b e h a v i o u r o f t h e foam at the elevated t e m p e r a t u r e and p r e s s u r e which e x i s t s i n t h e o i l f i e l d . Experimental study of these aspects is therefor required, but regrettably few such i n v e s t i g a t i o n s have been r e p o r t e d < 4 - 6 ) . T h i s p a p e r is concerned w i t h a d e s c r i p t i o n o f an a p p a r a t u s d e s i g n e d f o r t h i s p u r p o s e , and a preliminary report of some aspects of its performance together with some p r e l i m i n a r y o b s e r v a t i o n s on the e f f e c t o f p r e s s u r e on t h e a p p a r e n t v i s c o s i t y o f a foam f l o w i n g i n a s t r a i g h t c a p i l l a r y tube. 2
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The central feature is a high pressure c e l l ( l i n F i g u r e 1), a c y l i n d r i c a l v e s s e l , i n t e r n a l l y about 0.9 m in length and 0.1 ro i n i n t e r n a l d i a m e t e r mounted w i t h i t s a x i s h o r i z o n t a l . The c e l l i s constructed of selected stainless steel with a wall thickness and d e s i g n s u c h t h a t i t can w i t h s t a n d an i n t e r n a l p r e s s u r e o f 5250 p . s . i . g . The s c r e w e d - o n end c a p s o f t h i s test cell are capable of c a r r y i n g various d i f f e r e n t t e s t u n i t s ( 2 i n F i g u r e 1) w i t h i n t h e p r e s s u r e c e l l , and a r e p r o v i d e d w i t h i n l e t and outlet lines for the test fluid. The test units which can be incorporated i n c l u d e s t r a i g h t , g l a s s , c a p i l l a r y t u b e s up t o 0.76 m long and s a n d pack o r c o r e sample h o l d e r s up t o t h e same l e n g t h and 6.1 ro in diameter. Optical glass windows, 0.1 ro long and 0.01 ro wide a t t h e t o p and bottom o f t h e t e s t c e l l can p e r m i t v i s u a l observation o f the b e h a v i o u r o f the f l u i d w i t h i n g l a s s t e s t u n i t s .
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Figure i . Schematic representation of the flow o f t h e foam r h e o l o g y r i g . 1 3 5 7 9 11 13 15 17
High pressure cell Test unit Redded c e l l Non-return valve Water s t o r a g e v e s s e l S u r f a c t a n t pump pressure r e l i e f valve Pressure r e l i e f valve P r e s s u r e pump (hand o p e r a t e d )
2 4 6 3 10 12 14 16 18
diagram
End caps o f t e s t c e l l Foam g e n e r a t o r Gas i n redded c e l l Surfactant storage vessel Pressure r e l i e f valve W a t e r pump Non-return valve Pressure reducing valve Pressure r e l i e f valve
Discharge to drain D Filters F l ,F2 P Pre ss u r e gauge BPRV1 Back p r e s s u r e r e l i e f v a l v e BPRV2 Back p r e s s u r e r e l i e f v a l v e D i g i t a l b a1a nc e D/Bal Low p r e s s u r e n i t r o g e n b l a n k e t L.P.N2 H . P. N 2 H i g h p r e s s u r e n i t r o g e n s u p p l y Vac Vacuum ] i n e W Water supply
supply
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Another thick walled cylindrical, stainless s t e e l , v e s s e l ( 4 i n F i g u r e 1), i n s i d e diameter 0.03 m and i n s i d e l e n g t h 0.075 ro a l s o c a p a b l e o f w i t h s t a n d i n g an i n t e r n a l p r e s s u r e o f 5250 p . s . i . g . i s mounted c l o s e to the inlet feed of the h i g h p r e s s u r e t e s t c e l l . C o r e s o r sand packs can be installed within this v e s s e l , w h i c h s e r v e s as a foam g e n e r a t o r . Gas can be s u p p l i e d t o t h e foam g e n e r a t o r o r t o t h e t e s t c e l l from a rodded c e l l ( 5 in Figure 1), a stainless steel cylinder, inside dimensions a p p r o x i m a t e l y 0.5 m l o n g and 0.04 m d i a m e t e r , mounted with i t s a x i s v e r t i c a l , and d e s i g n e d f o r an i n t e r n a l w o r k i n g p r e s s u r e o f 6000 p . s . i . g Electrical strip heaters, wrapped around the three stainless steel v e s s e l s enable them to be operated at any desired temperature. Thermocouples strapped to the surfaces of the vessels permit measurement o f their temperatures and, coupled to controllers, maintain the vessels at constant t e m p e r a t u r e o r e n s u r e t h a t t h e r a t e o f change of the temperature of the vessels i s not excessive, so a v o i d i n g u n n e c e s s a r y t h e r m a l s t r e s s i n them. As shown in Figure 1, for investigations at pressures up t o 2000 p . s . i . g . h i g h p r e s s u r e n i t r o g e n , from a c y l i n d e r , c a n be introduced into the rodded cell. The gas , 6, i n the rodded c e l l a t t h e d e s i r e d p r e s s u r e can be d r i v e n by t h e m o t i o n o f t h e p i s t o n , R, v i a a n o n - r e t u r n v a l v e , 7, t o t h e foam generator or directly t o t h e t e s t u n i t . The p o s i t i o n o f t h e p i s t o n c a n be d e t e r m i n e d by a digital position indicator gauge mounted on t h e end o f t h e p i s t o n rod(R i n F i g u r e 1), which t h u s p e r m i t s d e t e r m i n a t i o n o f t h e volume o f gas i n j e c t e d and t h e r a t e o f i n j e c t i o n . Two 4 1 cylindrical glass(QVF) vessels with s t a i n l e s s s t e e l end p l a t e s , s e r v e as r e s e r v o i r s ( F i g u r e 1) f o r s u r f a c t a n t s o l u t i o n ( B ) and w a t e r ( 9 ) . F a c i l i t y i s a v a i l a b l e t o e v a c u a t e t h e s e v e s s e l s as r e q u i r e d by means o f a r o t a r y vacuum pump w i t h g l a s s c o l d t r a p i n line to minimise water vapour. Another pipeline permits s u p p l y o f p u r e n i t r o g e n , o r o t h e r gas, a t low p r e s s u r e , t o the v e s s e l s , to provide a blanket, as desired. Proper operation and safety from over p r e s s u r e i s e n s u r e d by a p r e s s u r e r e l i e f valve(10 in F i g u r e 1) and t h e p r e s s u r e g a u g e ( P i n F i g u r e 1 ) . The desired surfactant solution, prepared by d i s s o l v i n g t h e a p p r o p r i a t e w e i g h t i n a known volume o f d i s t i l l e d w a t e r , can be i n t r o d u c e d into the storage v e s s e l ( 8 ) from which i t may be d i s c h a r g e d t o a d r a i n ( D in F i g u r e 1), or f e d v i a a f i l t e r ( F l i n F i g u r e 1), to one s i d e o f a d u a l p e r i s t a l t i c p u m p ( l l i n Figure 1). From the pump outlet the s u r f a c t a n t s o l u t i o n flows through a l i n e equiped with p r e s s u r e relief valve(13 in Figure IC), to a non-return valve(14 i n Figure IC), and t h e n c e t o t h e foam g e n e r a t o r , o r t o t h e t e s t c e l l as d e s i r e d . The r a t e o f d e l i v e r y o f solution can be
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controlled by suitable adjustment o f the v a r i a b l e volume s e t t i n g o f t h e pump, p r e v i o u s l y c a l i b r a t e d to p e r m i t easy o p e r a t i o n . The o t h e r p a r t o f t h e d u a l purop(12 i n F i g u r e 1) can s i m i l a r l y s u p p l y w a t e r from the r e s e r v o i r ( 9 i n Figure 1), v i a a filter(F2 i n Figure 1) p a s t a p r e s s u r e r e l i e f v a l v e ( 1 5 i n F i g u r e 1) t o t h e u n d e r s i d e o f t h e p i s t o n o f t h e rodded c e l l (5 i n F i g u r e .1). This in turn d r i v * » gag from tfh© u p p e r s i d e o f th© p i s t o n t o t h e o t h e r i n l e t o f t h e foam generator. To refill the redded c e l l w i t h h i g h p r e s s u r e g a s , t h e w a t e r from the underside o f t h e p i s t o n c a n be r e t u r n e d t o t h e reservoir(9) v i a a pressure reduction valve(16 i n Figure 1 ) . The filters(Fl and F2 i n Figure 1), 5 m i c r o n p o r e s i s e , i n t h e f e e d s t o t h e pumps, s e r v e to protect these devices from damage and additional s e c u r i t y i s p r o v i d e d by p r e s s u r e r e l i e f v a l v e s ( 1 3 and 15 i n F i g u r e 1) on t h e e f f l u e n t flow lines of the pumps. Foam created i n t h e foam generator i s fed d i r e c t l y t o the i n l e t o f the t e s t unit i n the t e s t cell, and the p r e s s u r e d r o p d e v e l o p e d by i t s f l o w through the t e s t unit i s measured by means of a differential pressure transducer, n o t shown i n t h e figure, connected between inlet and o u t l e t , and provided with by-pass and isolation valves f o r protection against accidental overloading. The w a t e r pumped t o t h e u n d e r s i d e o f t h e p i s t o n of t h e r o d d e d c e l l c a n a l s o be d e l i v e r e d t o t h e t e s t cell, to f i l l the jacket surrounding the test unit(Figure 1 ) . The c o n t e n t s o f t h e j a c k e t c a n be discharge-id v i a a b a c k - p r e s s u r e r e l i e f valve(BPRVl in Figure 1) which i s a r r a n g e d t o open when t h e w a t e r p r e s s u r e e x c e e d s t h a t o f t h e foam f l o w i n g t o t h e i n l e t of the t e s t u n i t . Foam leaves the test unit via another b a c k - p r e s s u r e r e l i e f v a l v e ( B P R V 2 i n F i g u r e 1 ) . I n most of t h e i n v e s t i g a t i o n s w h i c h a r e p l a n n e d t h e foam w i l l be c o l l e c t e d i n a s u i t a b l e v e s s e l on a continuous weighing top loading d i g i t a l balance(D/Bal i n Figure 1). As shown i n Figure 1, the s e t t i n g of this back-pressure r e l i e f v a l v e i s d e t e r m i n e d by t h e w a t e r pressure applied to the jacket surrounding the t e s t u n i t so t h a t f l o w o u t o f t h e t e s t u n i t o c c u r s when t h e internal pressure i n the u n i t exceeds t h a t i n the water j a c k e t s u r r o u n d i n g the t e s t u n i t . F a c i l i t y i s p r o v i d e d t o b r i n g t h e e q u i p m e n t up t o the d e s i r e d a b s o l u t e p r e s s u r e w i t h o u t s u b j e c t i n g the t e s t u n i t t o e x c e s s i v e p r e s s u r e d i f f e r e n c e between i t s interior and e x t e r i o r . T h i s i s a c c o m p l i s h e d by f i r s t f i l l i n g t h e t e s t c e l l w i t h w a t e r by means of a hand operated h y d r a u l i c pump(17 i n F i g u r e 1) t o a s u i t a b l e v a l u e as i n d i c a t e d on t h e B o u r d o n dial gauges(P i n F i g u r e 1 ) . The p r e s s u r e t h u s d e v e l o p e d i s u s e d a l s o t o control the appropriate back-pressure r e l i e f valve
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which remains closed u n t i l the internal pressure i n t h e t e s t u n i t h a s i n c r e a s e d t o t h e same v a l u e as t h e external pressure. Once t h e n e c e s s a r y p r e s s u r e has been r e a c h e d , the supply o f water from t h e hand operated pump i s d i s c o n t i n u e d and t h e t e s t c e l l w a t e r j a c k e t connected t o the p e r i s t a l t i c pump used t o supply water to the rodded c e l l . E x c e s s i v e p r e s s u r e d i f f e r e n c e between t h e i n t e r i o r o f t h e t e s t c e l l and exterior i s a v o i d e d by f e e d i n g t h e i n l e t p r e s s u r e o f the t e s t u n i t t o t h e o t h e r b a c k - p r e s s u r e r e l i e f valve which opens t o p e r m i t w a t e r from t h e e x t e r i o r o f t h e test unit t o be d i s c h a r g e d should the external pressure become too high. A pressure r e l i e f valve(18 in Figure 1) provides additional protection. F a c i l i t i e s are provided to f i t pressure transducers a t v a r i o u s p o i n t s on t h e f l o w l i n e s , s h o u l d i t be d e s i r e d t o m o n i t o r such p r e s s u r e s i n t h e f u t u r e . Signals from the d i g i t a l balance, t h e rodded c e l l r o d p o s i t i o n i n d i c a t o r , t h e gauge i n d i c a t i n g t h e pressure differential over the test unit and t h e output o f thermocouples i n d i c a t i n g the temperature o f foam entering and leaving the t e s t unit are t r a n s m i t t e d t o a d a t a l o g g i n g f a c i l i t y and r e c o r d e d on f l o p p y d i s c s on an A c o r n "BBC Mode B" microcomputer, and conveyed t o an Acorn " A r c h i m e d e s " computer f o r p r o c e s s i n g as d e s i r e d . S e v e r a l h u n d r e d v a l u e s f o r e a c h of the v a r i a b l e s could be r e c o r d e d during a run lasting up t o n i n e t y minutes, in this way, f o r subsequent a n a l y s i s .
The e x p e r i m e n t s i n i t i a l l y c o n d u c t e d were designed to t e s t t h e p e r f o r m a n c e o f t h e a p p a r a t u s by d e t e r m i n a t i o n of the e f f e c t o f p r e s s u r e on t h e v i s c o s i t y / q u a l i t y spectrum o f a t y p i c a l foaming agent when i t flows through a s t r a i g h t c a p i l l a r y t u b e . The method u s e d i s based on a t e c h n i q u e r e c e n t l y developed i n the laboratories( ) f o r this purpose, at atmospheric pressure. The v i s c o s i t y / f o a m q u a l i t y s p e c t r u m at a fixed p res s ure i s d e r i v e d from a s i n g l e e x p e r i m e n t i n which t h e foam g e n e r a t i n g v e s s e l i s f i r s t f i l l e d completely with foaming a g e n t s o l u t i o n , and then t h e g a s s u p p l y i s t u r n e d on. I n i t i a l l y , aqueous s o l u t i o n i s d i s p l a c e d from the g e n e r a t o r , b u t once gas break-through commences a wet foam i s discharged. As g a s f l o w c o n t i n u e s , t h e foam becomes drier and d r i e r until u.11imate 1 y o n l y g a s f 1 ows . D e t e r m i n a t i o n o f t h e r o d d e d c e l l r o d p o s i t i o n , as a function of time(Figure 2 shows a t y p i c a l s e t o f r e s u l t s ) , permits computation o f the v o l u m e t r i c gas f l o w r a t e i n t o t h e foam g e n e r a t o r . Figure 3 shows a t y p i c a l s e t o f r e s u l t s f o r t h e cumulative weight of fluid discharged from the 7
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F i g u r e 2. T y p i c a l p l o t o f d a t a output from the r i g , showing values of the p o s i t i o n o f the rodded c e l l p i s t o n as a f u n c t i o n o f t i m e , d u r i n g an e x p e r i m e n t . RUH No. S78S7(26) DATE 38 83
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F i g u r e 3. T y p i c a l p l o t o f d a t a output from the r i g , showing values o f the weight o f e f f l u e n t from t h e c a p i l l a r y t e s t u n i t as a f u n c t i o n o f t i m e , during an experiment. The p o r t i o n o f t h e c u r v e f r o m B - C shows the efflux of surfactant solution from the foam g e n e r a t o r which p r e c e d e s g a s b r e a k - t h r o u g h . P o r t i o n C D shows t h e e f f l u x o f foam o f i n c r e a s i n g q u a l i t y . A t times l a r g e r than D only "dry" gas, without liquid phase, emerges.
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apparatus, during the course o f an e x p e r i m e n t . The results d e m o n s t r a t e c l e a r l y how i n t h e i n i t i a l s t a g e , aqueous s u r f a c t a n t s o l u t i o n i s e l u t e d from the foam g e n e r a t o r , f o l l o w e d by foam o n c e g a s b r e a k - t h r o u g h h a s commenced. The s t e a d y d e c l i n e i n t h e r a t e o f i n c r e a s e o f c u m u l a t i v e w e i g h t o f foam t h r o u g h t h e course, o f t h e e x p e r i m e n t shown by t h e r e s u l t s i n F i g u r e 3, clearly demonstrates how t h e foam q u a l i t y s t e a d i l y i n c r e a s e s i n d r y n e s s u n t i l a t the end o f the experiment, only gas emerges from t h e foam g e n e r a t o r . A f t e r gas break-through. the incremental rate of increase i n e f f l u e n t w e i g h t c a n be t a k e n a s a m e a s u r e o f t h e i n c r e m e n t a l w e i g h t o f l i q u i d i n t h e foam. T h i s , together with a knowledge of the instantaneous volumetric gas flow rate, permits c a l c u l a t i o n of the q u a l i t y o f the foam. P r o v i d e d t h e p r e s s u r e drop over the foam generator is sufficiently small, the volumetric flow rate f o r such calculations can be taken to be constant throughout an e x p e r i m e n t and e q u a l t o t h a t i n d i c a t e d by d a t a s u c h a s t h a t shown in F i g u r e 2. T h i s a s s u m p t i o n was j u s t i f i e d i n t h e s t u d i e s at atmospheric pressure reported p r e v i o u s l y ( > , but i n the present i n v e s t i g a t i o n s c o r r e c t i o n f o r changes i n pressure drop across the foam generator during the c o u r s e o f a n e x p e r i m e n t may b e n e c e s s a r y . By c o n d u c t i n g a s e r i e s o f such measurements a t a number o f d i f f e r e n t gas f l o w rates, measurements of the pressure drop across a c a p i l l a r y tube having a known d i a m e t e r and length, during each experiment (Figure 4 shows a typical set of values of the d i f f e r e n t i a l p r e s s u r e gauge o u t p u t as a function of time), p e r m i t e v a l u a t i o n o f t h e w a l l s h e a r s t r e s s and w a l l shear r a t e as f u n c t i o n s o f t i m e * ) , and thereby for the range of foam q u a l i t i e s c r e a t e d d u r i n g t h e e x p e r i m e n t . P r e v i o u s s t u d i e s * > h a v e shown t h a t under such conditions, at atmospheric pressure, foam conforms c l o s e l y t o t h e s i m p l e power law r e l a t i o n for n o n - N e w t o n .1 a n f l u i d s : 7
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n w
(1)
where K i s t h e f l o w c o n s i s t e n c y , n i.s thf? p o w e r .1 nde>;, JJ«P>K> i s t h e a p p a r e n t v i s c o s i t y , i'w i s t h e w a l l s h e a r s t r e s s , a n d #w i s t h e w a l l s h e a r r a t e . The results shown i n F i g u r e 2 i l l u s t r a t e t h a t a s a t i s f a c t o r i l y c o n s t a n t gas f l o w r a t e over a p e r i o d o f t i m e i n e x c e s s o f one h o u r c o u l d be a c h i e v e d r e a d i l y . Consideration of the slope of the effluent weight/time curve j u s t a f t e r g a s b r e a k t h r o u g h , shown i n F i g u r e 3, i n d i c a t e s t h a t t h e foam first breaking through had a quality of about 60%, whilst that emerging n e a r t h e end o f t h e run has a quality of approximately 92%. The foam q u a l i t y a t i n t e r m e d i a t e
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DATE 38 83 88
RUH No. S78S7
5888 TIME sec
F i g u r e 4. D i f f e r e n t i a l p r e s s u r e function o f time, during a atmospheric pressure.
t r a n s d u c e r output, as a typical experiment at
28. NUTTETAL.
Flow of Foam Under Reservoir Conditions
527
times between these limits sometimes fluctuated i r r e g u l a r l y , sometimes b e c o m i n g d r i e r and t h e n s h o w i n g an a b r u p t i n c r e a s e i n w e t n e s s . Each s u c h irregularity was accompanied by c o r r e s p o n d i n g changes in the pressure drop observed f o r the flow through the c a p i l l a r y t u b e , a s i l l u s t r a t e d i n F i g u r e 4. T h e c h a n g e i n foam q u a l i t y i n d i c a t e d by t h e e f f l u e n t w e i g h t c u r v e was delayed by approximately 150 sees behind that i n d i c a t e d by t h e pressure drop/time curve, at the p a r t i c u l a r gas f l o w r a t e used i n t h a t e x p e r i m e n t . T h i s was due to the hold-up of effluent in the back-pressure r e l i e f valve i n the foam outlet line. These irregularities in foam q u a l i t y were c a u s e d by the gas f l o w p r o c e s s t h r o u g h t h e sand pack i n t h e foam g e n e r a t o r . From t i m e t o t i m e as t h e sand pack dried out, new g a s f l o w p a t h s d e v e l o p e d , a n d a s s o c i a t e d w i t h each such event t h e r e o c c u r r e d a t r a n s i e n t i n c r e a s e i n foam wetness. Careful p a c k i n g o f the foam g e n e r a t o r could minimise this phenomenon. Alternatively or additionally, the effect could be eliminated by inclusion of a mixing vessel of properly selected capacity, i n t h e foam f l o w l i n e between t h e g e n e r a t o r and t h e t e s t u n i t . The r h e o l o g i c a l b e h a v i o u r o f a t y p i c a l s u r f a c t a n t at a t m o s p h e r i c p r e s s u r e , d e r i v e d u s i n g t h i s t e c h n i q u e , has been r e p o r t e d and i l l u s t r a t e d i n various figures i n an e a r l i e r communication* ). 7
In the current program of investigations i t is intended t o study the r h e o l o g i c a l behaviour of foams formed by a range o f s u r f a c t a n t s , d u r i n g f l o w t h r o u g h a c a p i l l a r y tube, over the quality range 50-60% to 95%, at t e m p e r a t u r e s u p t o 100°C a n d p r e s s u r e s u p t o 2000 psig. After the addition of a pressure i n t e n s i f i e r the s t u d i e s o f c e r t a i n s e l e c t e d foams w i l l be e x t e n d e d t o p r e s s u r e s up t o 5,000 p s i g . By t h e a d d i t i o n o f o t h e r l i q u i d r e s e r v o i r s , e.g. f o r w a t e r and crude oils, and replacement of the capillary t e s t u n i t by a s a n d pack, t h e e f f e c t i v e n e s s of the same foams f o r enhanced o i l recovery at reservoir temperatures and pressures will be investigated.
The authors wish to record their thanks and a p p r e c i a t i o n t o I C I C h e m i c a l s and P o l y m e r s L t d . and t o O f f s h o r e S u p p l i e s O f f i c e f o r f i n a n c i a l s u p p o r t and f o r permission to publish this paper, and to Alval Engineering L t d f o r equipment manufacture and high pressure design input.
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REFERENCES (1) A l i J., Burley R.W. and Nutt C.W. "Foam Enhanced Oil Recovery from Sand Packs" Chem.Eng.Res.Des. 1985 63 101. (2) Giordano R.M and Slattery J . C . A.I.Chem.E. Symp.Series 1982 78 58. (3) Nutt C.W., Burley R.W., Stavenam A. and Naismith S.M. "Mechanism of the Displacement of Oil from a Porous Medium by Foam" (in press) (4) Heller J . P . and Runtamukkula M.S. "Critical Review of Foam Rheology Literature" Ind.Eng.Chem. 1987 26 318. (5) Farouq A l i S.M. and Sel by R . J . "Function, Characteristics of EOR Foam Behaviour Covered in Laboratory Investigations" Technology, O i l & Gas J . Feb 3 1986 57-63 (6) McPhee C . A . , Tehrani A.D.H. and Jolly R.P.S. S.Ρ.Ε. 1988 Paper No.17360 (7) Assar G.R., Nutt C.W. and Burley R.W. "The Viscosity-Quality Spectrum of Foam Flowing in Straight Capillary Tubes" (in press) Int. J. of Eng. Fluid Mech. 1988. RECEIVED
November 28, 1988
