Soluble Silicates - American Chemical Society

13

The

Role

of

Emulsification

Phenomena

in

Alkaline

Waterflooding of Heavy Crude Oils 1

Downloaded by UNIV OF BATH on June 26, 2016 | http://pubs.acs.org Publication Date: June 1, 1982 | doi: 10.1021/bk-1982-0194.ch013

P. R. BRAUER and D. T. WASAN Illinois Institute of Technology, Department of Chemical Engineering, Chicago, IL 60616 Greater improvements i n Enhanced Oil Recovery by alkaline flooding occurred in linear core floods where more in-situ emulsification was observed. These in-situ generated emulsions aided i n tertiary recovery by improving the areal sweep efficiency of the alkaline slug and by improving the dynamic mobility ratio within the core. Previous work in our laboratory (1) implied that higher recovery efficiency may be achieved through the injection of an extracted resinous component, deasphaltened crude oil slug, prior to the injection of the alkaline phase. Results indicated that improvements in tertiary recovery efficiency did occur. The injection of this extracted resinous crude component aided in recovery by preventing asphaltene deposition, thereby increasing permeability of oil to rock, by forming an oil bank, and again, in-situ emulsification was observed to aid in enhanced recovery. A microwave attenuation technique was used to monitor in-situ oil/water saturations during enhanced recovery for each alkaline core flood. Alkaline flooding i s based on the reaction that occurs between the alkaline water and the organic acids, naturally occurring in some crudes, to produce in-situ surfactants or emulsifying soaps at the oil/water interface. Recent literature (£-j>) summarizes several proposed mechanisms by which alkaline waterflooding w i l l enhance o i l recovery. These mechanisms include: emulsification and entrapment, emulsification and entrainment, and wettability reversal (oil-wet to water-wet or water-wet to oil-wet). Depending on the i n i t i a l reservoir and experimental conditions with respect to o i l , rock and injection water propert i e s , one or more of these proposed mechanisms may be controlling. 1

Current address: Cities Service Company, Energy Resources Group, Exploration and Production Research, Tulsa, OK 74102. 0097-6156/82/0194-0215$06.00/0 © 1982 American Chemical Society

Falcone; Soluble Silicates ACS Symposium Series; American Chemical Society: Washington, DC, 1982.


216

S O L U B L E SILICATES

Many s t u d i e s to date, have r e l a t e d e m u l s i f i c a t i o n to o i l recovery. M c A u l i f f e ' s r e s u l t s (Jl*1) showed that the i n j e c t i o n of d i l u t e o i l - i n - w a t e r emulsions, prepared e x t e r n a l to the porous medium, enhanced o i l recovery. D ' E l l a ^ C8) a l s o showed that the i n j e c t i o n of prepared w a t e r - i n - o i l emulsions can be used e f f e c t i v e l y i n secondary and t e r t i a r y recovery of v i s c o u s crude o i l s . Rather than the e x t e r n a l p r e p a r a t i o n of emulsions f o r enhanced recovery, Cash (£) proposes that r e s i d u a l o i l can be m o b i l i z e d by spontaneous e m u l s i f i c a t i o n w i t h i n the core. Each of these i n v e s t i g a t o r s has shown the c a p a b i l i t i e s of e i t h e r e x t e r n a l l y prepared emulsions or i n - s i t u generated emulsions f o r improving o i l r e c o v e r y . These emulsions can enhance recovery by improving the a r e a l sweep e f f i c i e n c y Q ) . In the case of the o i l e x t e r n a l emulsion, m i s c i b i l i t y w i t h r e s i d u a l o i l can occur, l e a d i n g to a d d i t i o n a l o i l recovery through m i s c i b l e displacement. R e s u l t s of our experimentation Q J suggests that the occur rence of p e r m e a b i l i t y r e d u c t i o n s during enhanced o i l recovery may be avoided and the formation of a continuous o i l bank may be i n i t i a t e d and maintained by u s i n g a s l u g of an e x t r a c t e d r e s i n ous f r a c t i o n . These r e s u l t s support the work of L i c h a a and H e r r e r a (10,11), where they found that severe p e r m e a b i l i t y r e ductions due to asphaltene d e p o s i t i o n , could be avoided by the i n j e c t i o n of a mixture of h i g h l y r e s i n o u s Boscon Crude (29% wt. r e s i n ) w i t h a Boscon r e f i n e d o i l . Cooke (2) recommended a s i m i l a r process where a bank of h i g h l y a c i d i c crude o i l would be i n j e c t e d p r i o r to the i n j e c t i o n of the a l k a l i n e water f o r cases where the crude o i l a c i d c o n c e n t r a t i o n i s low. The present study u t i l i z e s a microwave a t t e n u a t i o n t e c h nique to study o i l bank formation and propagation d u r i n g l i n e a r core t e s t s . T h i s technique, f i r s t developed by Parsons (12). was employed to monitor the dynamic i n - s i t u water c o n c e n t r a t i o n during the a l k a l i n e core f l o o d i n g experiments. Experimental Two crude o i l s were used f o r t h i s study. Huntington Beach Crude from W e l l S-47, which has an API of 23.0 , an a c i d number of 0.65 mg KOH/gram of crude, and a b u l k shear v i s c o s i t y of 10 cp at the r e s e r v o i r temperature of 165°F. The other C a l i f o r n i a n crude o i l used was Wilmington F i e l d Crude from W e l l C-331. T h i s crude has an API of 21.3 , an a c i d number of 0.86, and a b u l k ο shear v i s c o s i t y of 35 cps at the r e s e r v o i r temperature of 125 F. The t e r t i a r y o i l recovery experiments were performed i n one i n c h by f o u r i n c h by twelve i n c h Berea sandstone c o r e s . The average p o r o s i t y was 0.20 and average b r i n e p e r m e a b i l i t y was 600 md. Each experiment was conducted i n the f o l l o w i n g sequence: (1) Purge core w i t h n i t r o g e n (2) Evacuate and b r i n e f l o o d at 45mm Hg Abs. to achieve f u l l i n i t i a l saturation.


13.

B R A U E R A N D WASAN

Emulsification

Phenomena

217


(3)

Heat core to r e s e r v o i r temperature w h i l e f l o w i n g two a d d i t i o n a l pore volumes of b r i n e f o r c l a y c o n d i t i o n i n g . Determine b r i n e saturated pore volume and b r i n e per m e a b i l i t y at r e s e r v o i r temperature. (4) O i l s a t u r a t i o n u n t i l produced oil/aqueous r a t i o exceeds 100/1. (5) B r i n e f l o o d (secondary recovery) u n t i l produced aqueous/ o i l r a t i o exceeds 100/1. (6) 1.0% B r i n e p r e f l u s h (0.05 pv. f o r Wilmington t e s t only) (7) Continous i n j e c t i o n of a l k a l i n e s o l u t i o n u n t i l f i n a l produced w a t e r / o i l r a t i o exceeds 100/1. F r o n t a l advance r a t e s were 1 f t / d a y a f t e r i n i t i a l b r i n e s a t u r a t i o n and 3 f t / d a y during b r i n e s a t u r a t i o n . The b r i n e used f o r the Huntington Beach core t e s t contains 0.75% NaCl, whereas the b r i n e used f o r the Wilmington F i e l d core t e s t s contained 1.0% NaCl and 1100 ppm Calcium Ion. S u f f i c i e n t back pressure was main t a i n e d on the system throughout the experiment to prevent the o i l from de-gasing w h i l e w i t h i n the core. Microwave scans were performed every two hours during t e r t i ary recovery and more f r e q u e n t l y where r e q u i r e d . The data f o r each core f l o o d i s presented i n the form of microwave p r o f i l e s showing the v a r i a t i o n i n average o i l s a t u r a t i o n w i t h d i s t a n c e along the core. During t e r t i a r y recovery, the produced f l u i d s were analyzed m i c r o s c o p i c a l l y f o r the presence of o i l - i n - w a t e r and w a t e r - i n o i l emulsions. K a r l F i s c h e r a n a l y s i s was performed on the pro duced f l u i d samples i n order to determine the amount of o i l p r e sent i n the aqueous phase and the amount of water present i n the o i l phase. A l s o pH readings were recorded f o r the produced aqueous phase throughout t e r t i a r y recovery. R e s u l t s and D i s c u s s i o n Several a l k a l i n e chemicals have been employed f o r v a r i o u s aspects of enhanced o i l recovery. Two of the most f a v o r a b l e a l k a l i n e chemicals t e s t e d and used i n t e r t i a r y o i l recovery are sodium o r t h o s i l i c a t e and sodium hydroxide. Comparing t h e i r char a c t e r i s t i c s , both chemicals r e a c t w i t h a c i d s i n crude o i l to form s u r f a c t a n t s , p r e c i p i t a t e hardness ions and change rock s u r f a c e w e t t a b i l i t y . One d i f f e r e n c e between the two chemicals i s that the i n t e r f a c i a l p r o p e r t i e s f o r sodium o r t h o s i l i c a t e systems are l e s s a f f e c t e d by hardness ions (13), hence s l i g h t l y lower i n t e r f a c i a l t e n s i o n s would occur. Lower i n t e r f a c i a l tensions can a i d i n i n - s i t u emulsion formation. T h i s study i s the s t a r t of a systematic study of v a r i o u s concentrations of sodium o r t h o s i l i c a t e and sodium hydroxide against Wilmington F i e l d Crude. I n i t i a l a l k a l i n e core t e s t s were performed u s i n g 0.6% sodium o r t h o s i l i c a t e or sodium hydroxide w i t h 1.0% NaCl. P r i o r to the continuous i n j e c t i o n of the a l k a l i n e phase, a 0.05 pv s l u g of 1.0% NaCl was i n j e c t e d as a p r e -



218

SOLUBLE

SILICATES

f l u s h s o l u t i o n to separate the a l k a l i n e phase from the hardness ions i n the connate b r i n e . Core t e s t s r e s u l t s are presented i n Tables I and I I . R e s u l t s show that s l i g h t l y b e t t e r o i l r e covery e f f i c i e n c y (27-28% v s . 21-22%) can occur when u s i n g the sodium o r t h o s i l i c a t e system. A t y p i c a l microwave p r o f i l e f o r secondary recovery of W i l mington F i e l d crude i s presented i n F i g u r e 1. Examination of the microwave o i l s a t u r a t i o n p r o f i l e during t e r t i a r y o i l recovery f o r each of the f l o o d s , shows s i m i l a r o i l banking c h a r a c t e r i s t i c s f o r each a l k a l i n e chemical. In core t e s t s 1 and 2, using sodium o r t h o s i l i c a t e , e a r l y formation of an o i l bank was observed ( F i g ure 2 ) . T h i s o i l bank flows down the l e n g t h of the core and o i l i s produced at hour 18 i n t o t e r t i a r y o i l recovery. Comparing the microwave s a t u r a t i o n p r o f i l e s f o r core t e s t s 3 and 4 u s i n g sodium hydroxide, e a r l y formation of an o i l bank was again ob served (Figure 3 ) . T h i s o i l bank a l s o i s continuous and i s pro duced at hour 18 i n t o t e r t i a r y recovery. Comparison of the o i l banking during t e r t i a r y o i l recovery f o r s i m i l a r c o n c e n t r a t i o n s of sodium o r t h o s i l i c a t e and sodium hydroxide w i t h i n a hardness i o n environment, d i d not i n d i c a t e why one chemical may be p r e ferred . Comparison of the produced f l u i d a n a l y s i s f o r these f l o o d s w i l l g i v e us an i n d i c a t i o n of why one process may be p r e f e r r e d . Produced f l u i d a n a l y s i s f o r these f l o o d s show pH breakthrough o c c u r r i n g at s i m i l a r times f o r each process (Figure 4,5). So, the two processes cannot be separated by comparing c a u s t i c break through times. Each of these f l o o d s produced o i l - i n - w a t e r and w a t e r - i n - o i l emulsions c o i n c i d e n t w i t h pH breakthrough. These i n - s i t u gen erated emulsions d i d not cause s i g n i f i c a n t i n c r e a s e s i n the t o t a l pressure drop across the l e n g t h of the core. K a r l F i s c h e r a n a l y s i s of produced o i l and aqueous phase showed that more emulsi f i c a t i o n occurred i n the sodium o r t h o s i l i c a t e f l o o d s . R e s u l t s i n d i c a t e over 2.3% i n c o r p o r a t i o n of water i n t o the o i l phase and over 4.0% i n c o r p o r a t i o n of o i l i n t o the water phase f o r the so dium o r t h o s i l i c a t e f l o o d s . For the sodium hydroxide f l o o d s , o n l y 1.4% water-in-oij. emulsion and 0.6% o i l - i n - w a t e r emulsion was produced. These p r e l i m i n a r y r e s u l t s suggest that t h i s sodium o r t h o s i l i c a t e system e m u l s i f i e s o i l b e t t e r than the sodium hydroxide system. These i n - s i t u generated emulsions may have i n c r e a s e d the displacement c a p a b i l i t i e s of the a l k a l i n e phase by improving the m o b i l i t y r a t i o and/or the a r e a l sweep e f f i c i e n c y w i t h i n the core, thus causing the s l i g h t i n c r e a s e i n t e r t i a r y o i l recovery f o r the sodium o r t h o s i l i c a t e f l o o d s . Previous work (1) i n core f l o o d s w i t h the system, Huntington Beach Crude v s . 0.5% Na^SiO^ p l u s 0.75% NaCl, showed channeling of the crude o i l during the i n j e c t i o n of the c a u s t i c s l u g ( F i g u r e 6). The channeling phenomena along w i t h the f a c t that emulsions were not observed u n t i l a f t e r 95% of the recovered o i l was p r o duced, c o u l d have l e a d to lower o i l recovery e f f i c i e n c i e s . To


13.

TABLE I .


219

Emulsification Phenomena

BRAUER A N D WASAN

CORE TEST DATA

CORE TEST

POROSITY

CRUDE OIL

1

0.205

Wilmington F i e l d

0.6% Na,Si0, + 1.0% NaCl 4 4

2

0.225


0.6% Na,Si0, + 1.0% NaCl 4 4

3

0.229


0.6% NaOH + l.C)% NaCl

4

0.228


0.6% NaOH + l.C)% NaCl

5

0.215

Huntington Beach

0.5% Na.SiO, + 0.75% NaCl 4 4

6

0.210

Huntington Beach

0.5% Na.SiO, + 0.75% NaCl 4 4

TABLE I I .

CORE TEST

s

o

i

S0

R

ALKALINE SLUG

CORE TEST DATA

% SECONDARY RECOVERY

S 0

F

% TERTIARY RECOVERY

1

0.72 pv

0.45 pv

38

0.33 pv

27

2

0.71 pv

0.41 pv

41.6

0.29 pv

28

3

0.73 pv

0.44 pv

39

0.35 pv

22

4

0.715 pv

0.42 pv

41.4

0.33 pv

21

5

0.64 pv

0.41 pv

37

0.31 pv

25

6

0.61 pv

0.37 pv

39

0.24 pv

31


SOLUBLE


220

1.5

2.5

3.5

4.5

INCHES Figure 1.

5.5

6.5

ALONG

7.5

8.5

9.5 10.5

CORE

Secondary recovery profiles for core test 1.


SILICATES

Emulsification



221

Phenomena

20 -15H ~L5

25

35

4.5 5.5 INCHES

Figure

3.

Microwave

Ί

20 pH

4.

δ\5 9.5 10.5

CORE

profiles for tertiary oil recovery, core test 3; 0.6% NaOH 1.0% NaCl vs. C-331 crude.

10 Figure

β'.5 75

ALONG

30

'—I

1

40

+

Γ

50

H O U R S INTO T.O.R.

The pH analysis of produced fluids, core tests 1 and 2; 0.6% Na SiO 1.0% NaCl vs. C-331 crude. k


k

+

222


13-

Π

I

ι

0.5

1X

12H

L

1

^ P

V

i n j e c t e d . pH_

==5

11 PH

10-

3-W


9-

8 7

π

ι—ι—ι

0

Figure 5.

10

1

20

1

1

1

1—ι

1—ι r~

1

30 40 50 H O U R S INTO T.O.R.

60

70

The pH analysis of produced fluids, core tests 3 and 4; 0.6% NaOH 1 % NaCl vs. C-331 crude.

111

454035-

soy

'I / 1

β

/

/

20-^^^^v

/

6

/

/

\ > »

J*

32 —

· ^

< 30oc

+

/

8

D I-

/

^

·8 >·—#12 3 2

__e^^

y

^#54

< 252015-

54/

1

1

1

1.5 2.5 3.5 Figure

6.

4.5

5.5

6.5 7.5

INCHES A L O N G

CORE

I

8.5

1

1

9.5 10.5

Microwave profiles during tertiary recovery for core test 5; Beach crude vs. 5000 ppm orthosilicate + 7500 ppm NaCl.

Huntington



13.

Emulsification


223

Phenomena

examine the idea of u s i n g an e x t r a c t e d r e s i n o u s component to improve recovery e f f i c i e n c y , a deasphaltened s l u g of Huntington Beach Crude was prepared f o l l o w i n g standard ASTM procedures (13). Following completion o f secondary recovery and p r i o r to the con tinuous i n j e c t i o n of the a l k a l i n e phase, a 0.05 pv s l u g of t h i s deasphaltened Huntington Beach Crude was i n j e c t e d . R e s u l t s f o r t h i s core t e s t a r e a l s o summarized i n Tables I and I I . T e r t i a r y o i l recovery increased to 31% from the 25% recorded i n the core t e s t where a deasphaltened s l u g was not employed. Comparing the t e r t i a r y o i l s a t u r a t i o n p r o f i l e s f o r the two core t e s t s , the e a r l y formation of an o i l bank a t hour 2 f o r core t e s t 6 i s ob served (Figure 7). T h i s o i l bank i s formed because of the i n j e c t i o n of the 0.05 pv s l u g of deasphaltened crude. The volume of o i l above r e s i d u a l s a t u r a t i o n (S0^) a t hour 2 represents the volume of o i l i n j e c t e d i n the deasphaltened crude s l u g . T h i s o i l bank flows down the l e n g t h o f the core and i s produced a t hour 9 (Figure 8 ) . Produced f l u i d a n a l y s i s showed pH breakthrough o c c u r r i n g at hour 21 (Figure 8 ) . The i n i t i a l o i l that i s produced w i t h i n the bank does not c o n t a i n any emulsions, but the remainder of the produced o i l d i d c o n t a i n w a t e r - i n - o i l emulsions. Oil-inwater emulsions were produced c o i n c i d e n t with the o i l bank. These i n - s i t u generated emulsions may have aided i n improving the r e covery e f f i c i e n c y f o r the deasphaltened crude core t e s t according to the reasons s t a t e d p r e v i o u s l y .

1.5

2.5

3.5

4.5

5.5

6.5

7.5

8.5

9.5

10.5

INCHES A L O N G C O R E Figure

7.

Microwave

profiles during tertiary recovery for core test 6.



224

12 1110 PH


9 8 7 0

Figure 8.

8

16 24 32 40 48 HOURS INTO T.O.R.

56

The pH and fractional flow of produced fluids, core test 6.

Summary and Conclusion 1. I n - s i t u generated emulsions were produced c o i n c i d e n t with breakthrough. 2. More i n - s i t u e m u l s i f i c a t i o n was observed w i t h the sodium o r t h o s i l i c a t e system r a t h e r than the sodium hydroxide system. 3. I n - s i t u generated emulsions could enhance recovery t e c h niques by improving the a r e a l sweep e f f i c i e n c y of the a l k a l i n e s l u g and by improving the dynamic m o b i l i t y r a t i o w i t h i n the c o r e . 4. Improvements i n enhanced recovery occurred when a de asphaltened crude o i l s l u g was i n j e c t e d p r i o r to the continuous a l k a l i n e phase. 5. The deasphaltened crude o i l s l u g , e x t r a c t e d r e s i n o u s com ponent, may have improved t e r t i a r y recovery by p r e v e n t i n g a s p h a l tene d e p o s i t i o n , thereby i n c r e a s i n g p e r m e a b i l i t y of o i l to rock, by forming an o i l bank, or again, i n - s i t u e m u l s i f i c a t i o n may have enhanced o i l recovery. pH



13. BRAUER AND WASAN

Emulsification Phenomena

225

Literature Cited 1. Pasquarelli, C. H.; Brauer, P. R.; Wasan, D. T.; Ciempil, M.; Perl, J. P., "The Role of Acidic, High Molecular Weight Crude Components in Enhanced Oil Recovery", SPE 8895. Paper pre sented at the 50th Annual California Regional Meeting of the Society of Petroleum Engineers of AIME. Los Angeles, California, April 9-11, 1980. 2. Cooke, C. E., Jr.; Williams, R. E.; Kolodize, P. Α., "Oil Recovery by Alkaline Waterflooding", JPT. December 1974, pp. 1365-1374. 3. Jennings, Η. Y.; Johnson, C. B.; McAuliffe, C. D., "A Caustic Waterflooding Process for Heavy Oils", JPT. December 1974, pp. 1344-1352. 4. Johnson, C. B., "Status of Caustic and Emulsion Method", JPT. January 1976, pp. 85-92. 5. Mayer, Ε. H.; Berg, R. L.; Carmichael, J. D.; Weinbrandt, R. Μ., "Alkaline Injection for Enhanced Oil Recovery--A Status Report", SPE 8848. Paper presented at the 50th An nual California Regional Meeting of the Society of Petroleum Engineers of AIME. Pasadena, California, April 9-11, 1980. 6. McAuliffe, C. D., "Crude Oil-in-Water Emulsions to Improve Fluid Flow in an Oil Reservoir", JPT. June 1973, pp. 721726. 7. McAuliffe, C. D., "Oil-in-Water Emulsions and Their Flow Properties in Porous Media", JPT. June 1973, pp. 727-733. 8. D"Elia-So, R.; Ferrer-G, J . , "Emulsion Flooding of Viscous Oil Reservoirs", SPE 4674. 48th Annual Fall Meeting. Las Vegas, Nevada, September 30 - October 3, 1973. 9. Cash, R. L., Jr.; Cayisas, J. L.; Haynes, M.; MacAllister, D. J.; Schares, T.; Schechter, R. S.; and Wade, W. Η., "Spontaneous Emulsification--A Possible Mechanism for En hanced Oil Recovery", SPE 5562. Paper presented at 50th Annual Fall Meeting of the Society of Petroleum Engineers of AIME. Dallas, Texas, September 28 - October 1, 1975. 10. Lichaa, P. Μ., "Asphaltene Deposition Problem in Venezuelan Crudes--Usage of Asphaltenes in Emulsion Stability". Paper presented at the Canada--Venezuela Oil Sands Symposium 77. Edmonton, Alberta, Canada, May 27 - June 4, 1977. 11. Lichaa, P. M.; Herrera, L., "Electrical and Other Effects Related to the Formation and Prevention of Asphaltene Deposi tion Problem in Venezuelan Crudes", SPE/AIME No. 5304. 1975. 12. Parsons, R. W., "Microwave Attenuation—A New Tool for Monitoring Saturations in Laboratory Flooding Experiments", SPE J. August 1975, pp. 302-310.


226

SOLUBLE SILICATES


13. Campbell, T. C., "The Role of Alkaline Chemicals in the Recovery of Low Gravity Crude Oils". SPE 8894. Paper presented at the 50th Annual California Regional Meeting of the Society of Petroleum Engineers of AIME. Pasadena, California, April 9-11, 1980. 14. Pasquarelli, C. Η., M.S. Thesis, Illinois Institute of Tech nology, Chicago, 1980. RECEIVED March 2, 1982.


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