T-1189
THE A D S O R P T I O N OP A R A D I O A C T I V E T R A C E R AS A F U N C T I O N OF T E M P E R A T U R E A N D C O N C E N T R A T I O N
ON U N C O N S O L I D A T E D S A N D
ARTHUR LAKES LIBRARY COLORADO SCHOOL OF MINES
GOLDEN, COLORADO
by
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A Thesis s u bmitted to the Faculty and the B o ard of T r u s t e e s of the Colorado School of Mines in partial f u l f i l l m e n t of the r e q u i r e m e n t s •for the degree of M a ster of Scie n c e in P e t r o l e u m Engineering. S i g n e d : Golden, C olorado Date: ^ » 1968 A p p r o v e d srj^ Thesis A d v i s 6 r D 0 M» Bass Jr< Head of D e p a r t m e n t Golden, Colorado
T-1189
AB S T R A C T
This study was p e r f o r m e d to determine the a d s o r p t i o n of i o d i n e -131 as sodium iodide in aqueous solu t i o n as a f u n c t i o n of t e m perature and c o n c e n t r a t i o n of sodium i o dide on u n c o n s olid a t e d sand# The p r e d e t e r m i n e d t e m p e r a t u r e s were r o o m temp e r a t u r e (77° F), 100° F, 150° F, a n d 190° F. The i n d i v i d u a l s runs (five runs) were made at a c t i v i t i e s v a r y i n g from 691 cpm/cc to 21,123 cpm/cc*
It was found u n d e r the conditions studied that the m a x imum a d s o r p t i o n -obtained was 5^«93 p e r c e n t for a c o n c e n t r a t i o n of 21,123 cpm/cc for r o o m temperature (77° F), a n d a. n e g l i g i ble a d s o r p t i o n of 0#08 p e r c e n t at 190° F at a c o n c e n t r a t i o n
of 691 cpm/cc# It shows that sodium iodide u s e d as a t r a c e r
at l o w c o n c e n t r a t i o n a n d h i g h temperature exhib i t s little adsorption#
TABLE OF CONTENTS Page ABS TRACT a. . 0 .09.9. 99. .0.9 990. ...9. 9 9998. .9*99. 999,.9 1 1 .1. L I S T OF TABLES A N D FIGURES ... v A C K N O W L E D G M E N T ... viii jlNj. RODUCTION. ... ... ... 1 R E V I E W OF P REVIOUS T R A C E R S T U D I E S ... ^ A P P L I C A T I O N OF R A D I O I S O T O P E S T O W A T E R F L O O D I N G 6 D E T E R M I N A T I O N OF R A D I O A C T I V I T Y . ... 13 M A T E R I A L A N D APPA.RATUS . . . a . . . 18 E X P E R I M E N T A L PROCEDURE, ... 18 RiioULTS . . . s . . s . . . 19 D I S C U S S I O N .. . . s . . . * . . . , . . . 21 C O N C L U S I O N S ... 2^ A P P E N D I X a . . . . . . . . a . . . . . . . . . . . 28 LlTERATURd. ■ CITED. 87
iv
T-1189
LIST OF TABLES A N D FIGURES
Table Page 2? 27 28 29 30 31 32 33 3^ 35 36 3? 38 39 ^0 '-I-0
v
1 . Results of average p o r o s i t y t e s t , , , , , . ... 2 • Original a c t i v i t y for each r u n . . . • • • • • 0 e3® Run number o n e : r o o m temperature (77° F ) ,m ,
k * Run number One 1 0 0 F * » 9 9 » 9 9 9 9 9 9 a 9 9 9 9 0 9 9 9 9 9 9 5® Run n u m b e r One 1 5 0 F, i M O O • 3 1 , « t , S i) M 1 « a I M
6 9 Run number One 190 F 9999999999 9 009990999999
7® R un number. twos r o o m temperature (77° F ) , , , 0
8 9 Run number tWO 1 0 0 F9S999999 0 « 9 0 a 9 9 9 9 « 9 » 9 9 9
9 o Run n u m b e r two 150 F 9 9 9 9 0 999099909999999999
1 0 ., Run n umb e r two 190 O F 9 9 9 9 9 9 9 9 9 9 9 0 9 9 9 9 9 9 9 0 9 9 9
1 1 . Run n u mber threes r o o m temperature (77° F)..
1 2 o Run n u m b e r three 100 F ® o ® 9 © o a 9 9 © 9 9 9 a 9 9 9 9 9 9 9 13® R u n n u mber thre e 130 F o s s a a a e s a o o a o s o o o o o s o 1 4 0 Run n u mber thre e 1 9 0 F ® 9 e 0 0 9 9 9 O 8 8 ® 9 ® 8 9 « 9 9 9 O
15 0 Run n u m b e r fours r o o m temperature (77° F).,«.
Table Page 17 • Ran n u m b e r four i30 F 9 o . 3 3 9 9 . « 9 o . « o a . 9 . e 9 9 9 9 . .
18 * Run n u m b e r four 190 F t . o o . o e . . . a . . e o o . * . •••?*• ^1 19® R u n n u m b e r five: d e t e r m i n a t i o n of d e s o r p t i o n as a f u n c t i o n of t e m p erature » • 9 « » » « a • » » » • 9 »•••«»•« ^2 20. C o m p a r i s o n of d e c a y m a t h e m a t i c a l l y c a l c u l a t e d w i t h a c tual d e cay c a l c u l a t e d f r o m o b s e r v e d r e a d i n g s . . . . ...o...s.... ...* .< «.«• ^3 Figure 1. B l o c h d i a g r a m of a basic s c i n t i l l a t i o n c o u n t i n g s y otsliltt(0M OM tI»>)M M 9O9)teM n M 93»M 9M 91)1 2. R u n n u m b e r one: total p e r c e n t a d s o r b e d as a funct>ion of i/eniperatureaasa.asaa.oastaa.a.aa.oa. ^3 j o R u n n u m b e r o n e : room temperature (77° F ) . , <,«<>••• ^6 o R u n n U m b e r one 100 f a a a a a a s . o . o e o s a a o a a a a a o a a a a 47 3 0 R u n n u m b e r one 130 j^aaasas.a.saas.daaaao.aaoaoa ^8 o
8 o Run n u m b e r one 190 t a . a . a . o a . a o 9 9 9 3 9 9 . 0 9 . .sa.oa ^9 7« R u n n u m b e r two: total p e r c e n t a d s o r b e d as a
f u n c t i o n of temperature.-oooo...0 . 9 . 0 0 . 9 .00.909 3 ^
80 R u n n u m b e r two: room temp e r a t u r e (77° F )••••■.•• 31 9 0 R u n n u m b e r two 100 F a . s . e a o o o a s o a o a s o o o a a . s e . a o 32 10. R u n n u m b e r two 130 1 . . . 9 . 9’ao. ....ao.o.o... 3r
T-118.9
Figure
11 • Run. n u m b e r tvv o 130 1% «> n t < i •» m «• 9 1 « m ««• m • > • 54 12# R u n n u m b e r three: total percent a d s o r b e d as a
f u n c t i o n of tempe r a t u r e ....e. • 55
13• Run n u m b e r three: r oom temperature (77° F }»•»»•• 5^
14. Run n u m b e r three 100° F « » . , , . . » . . . * , * , a 3 ,»«*».., 57 15• R u n n u m b e r three 150 D . . . * . * . . . . ? . . ® . . . . 5^ l 6 # R u n n u m b e r three 130 F*a* * a « « « » o « » » a » » * » » 59 17* Run n u m b e r four: total perc e n t a d s o r b e d as a
1 u n c t i o n of temperu-ture 9 9 9 . 9 0 . 0 e a . 9 9 o . a 9g . o 9 9 9 .. 60 18. Ru n n u m b e r 19. R u n n u m b e r 20. Ru n n u m b e r 21. Ru n n u m b e r O O D e s o r p t i o n 2 3 o C o m p a r i s o n data...s.. >'JIU L/dil^C* J. Cc O t4JL \ ( ( !/••••••• ) F« a . 0 0 . 0 0 0 0 . . e . . . 0 0 . 0 . 0 ) F # » 9 0 9 » » 9 9 S ® # S 9 » 9 9 9 * 9 » ® * » 8 * ) F a 0 3 s * a S 8 O S 3 9 « 9 S 3 9 9 f f i « 9 9 * * O a .•O0...0a..e..«9..0....O.OO..9...a..eO..a 61 6 1 62 62 63 64
vii
ACKNOWLEDGMENT.
The financial support p r o v i d e d by T e xas P e t r o l e u m C o m pany is g r e a t l y a ppreciated. P r o f e s s o r Jerry R, B e r g e s o n * s inspi r i n g guidance, advice, a n d s u g g e s t i o n s are v e r y m u c h appreciated. Thanks are exten d e d a l s o to Dr, Jo J. Burnett a n d P r o f e s s o r D, M, Bass for their v a l u a b l e assistance.
T-1189
I N T R O D U C T I O N
The i n j e c t i o n of w ater into a r e s e r v o i r as a secondary recov e r y t e c h n i q u e has become a n important m e t h o d of p r o d u c
tion of crude oil. Oil, c o m m o n l y speaking, occurs in the
p ores of sandstone and limes t o n e formations. The h e t e r o g e
n e i ties that often exist in the r e s e r v o i r d e c r e a s e p r o d u c tion efficiency. The early d e t e c t i o n of these h e t e r o g e n e i ties may increase the e f f i c i e n c y of oil p r o d u c t i o n by water flooding.
In a s y s t e m of u n k n o w n f l o w performance, d i r e c t i o n a l p e r m e a b i l i t y can be such that the i njected w a t e r flows to one or two output w e l l s r e s u l t i n g in p oor r e c o v e r y f r o m the other wells.
The c h a r a c t e r i s t i c s of p r o d u c i n g f o r m a t i o n s m a y be d e t e r m i n e d by core analysis, by subsurface m e a s u r e m e n t s of te m p e r a t u r e a n d pressure, a n d by well h e a d t e s t s 0 C a l c u l a tions i n volving these d ata are based on the a s s u m p t i o n that the c o n d i t i o n s b e t w e e n wells are similar or compa r a b l e to those o b t a i n e d at the well bore 0 Trac e r s a d d e d to w ater at the i n j e c t i o n well or w e l l s a n d d e t e c t e d at the p r oducing
wells will supply the data to evaluate c e r t a i n r e s e r v o i r c o n d i t i o n s b e t w e e n wells that otherwise w o u l d be i m p o s s i b l e to evaluate.
Two types of tracers are norm a l l y u sed in tracing flows: chemical tracers, such as chlorides, nitrates, bromides,
a m m o n i u m t h i o c y a n a t e , p o t a s s i u m iodide; a n d r a d i o a c t i v e t r a c e r s , a s carbon-14, tritium, calcium-45 > sulfur-35 % i o d i n e - 1 3 1 >
cobalt-60, iridium-192, a n d potassium-42.
A p p l i c a t i o n s of r a d i o i s o t o p e s c a n be f ound in d i f f u s i o n studies of chemistry, and exchange r e a c t i o n of a n a l y t i c a l chemistry; in h y d r o l o g y to study u n d e r g r o u n d w a t e r s a n d r i v e r flows; in m e t e o r o l o g y for w e a t h e r forecasting; in m e d i c i n e for the d i a g n o s i s of tumors, thyroid disorders, anemia, v i r u s infection, e t c 0 ; a n d also in food technology, a g r o n o m y , etc.
The present i n v e s t i g a t i o n was c o n c e r n e d in the study of the b e h a v i o r of a d s o r p t i o n of a r a d i o a c t i v e trac e r as a f u n c tion of temperature and c o n c e n t r a t i o n in a p o r o u s medium®
T his ^investigation was to be cond u c t e d initi a l l y in a 2 0 - f o o t long, 2 7 / 8-in d i a m e t e r tube housing a n u n c o n s o l i d a t e d core s u r r o u n d e d by 7-in. c a sing w h i c h was to act as a c o n s t a n t t e m p e r a t u r e bath.
However, the h e a l t h h a z a r d that would be c r e a t e d b y 'the large a m o u n t of r a d i o a c t i v e mate r i a l n e c e s s a r y for c o n
T-1189
3
e x p e r i m e n t a l p r o c e d u r e u t i l i z e d in this w o r k e l i m i n a t e d storage a n d h e a l t h prob l e m s while still p r o d u c i n g m e a n i n g ful d a t a 0
The m e thod c o n s i s t e d of putting exact a m o u n t s of sand a n d r a d i o i s o t o p e in a f lask a n d c o n t r o l l i n g a d s o r p t i o n u t i li z i n g a c onstant t e m p erature bath* Total a d s o r p t i o n as a f u n c t i o n of tempe r a t u r e a n d c o n c e n t r a t i o n could then be d etermined.
The r a d i o i s o t o p e t r acer used in this i n v e s t i g a t i o n was i o d i n e -131 in the f o r m of s o d i u m iodide in a n a q u e o u s s o l u tion* Both high a n d l o w a c t i v i t y tracer s o l u t i o n s were used.
R E V I E W QF PREVIOUS T R A C E R STUDIES
Very little i n f o r m a t i o n has b e e n p u b l i s h e d c o n c e r n i n g the a d s o r p t i o n of r a d i o a c t i v e m a t e r i a l s on r e s e r v o i r sands. No p u b l i s h e d lite r a t u r e was found w h i c h a p p l i e s to the a d s o r p t i o n of r a d i o a c t i v e m a t e r i a l s on sand as a f u n c t i o n of temperature. A r e v i e w of the r e s e a r c h l i t e r a t u r e on a d s o r p t i o n of r a d i o a c t i v e or n o n - r a d i o a c t i v e m a t e r i a l s r e v e a l e d that p r e v i o u s expe r i m e n t s were c o n d u c t e d at r o o m t e m p e r a t u r e only. It Is p ossible that h i g h t e m p e r a t u r e s such as those f ound in oil r e s e r v o i r s could be a n i m p o r t a n t fa c t o r in e v a l u a t i n g r a d i o a c t i v e m a t e r i a l s for t r a cing w a t e r floods.
G arst and Wood (1953) performed field experiments with
non-radioactive iodine and copper sa.lts and obtained satis
factory results. However, most of the research to evaluate
radioactive materials ability to solve petroleum engineering problems has been performed in laboratories.
Wainerdi and N i e lsen (195*0 used a r a d i o a c t i v e tracer
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5
a n d the u n i n v a d e d zone, in a water flood operation. They
f o und that the relative importance of the d i f f e r e n t zones d e p e n d e d on the prope r t i e s of the r e s e r v o i r sand, the i n j e c
tion f luid u s e d a n d the inje c t i o n rate. They used a five
spot model and m e a s u r e d the fluid satur a t i o n d i s t r i b u t i o n d u r i n g the displacement. They a c c o m p l i s h e d this by t a g g i n g the i n j e c t i o n fluid with s o d i u m iodide- 131.
C o o m b e r and T i r a t s o o (1950* P» 5^3) c o n d u c t e d s i m i l a r e x p e r i m e n t s to those of Wainerdi a n d N i e l s e n (195^) u s i n g i o d i n e -131 as a t r acer in the oil phase instead of the w a t e r phase w i t h the object of studying the d i s t r i b u t i o n of oil a n d w a t e r in the d i f f e r e n t zones.
S a l l e y ( 1 9 5 0 i P* ^2) u s e d sulfur-35 to study the a d s o r p tion of s u r factants used to increase oil r e c o v e r y in w a t e r f lood operations.
Watltins (1 955, p. M ) used a nonionic p o l y o x y e t h y l a t e d a l kyl phenol, in r a d i o a c t i v e and n o n - r a d i o a c t i v e f o r m s to m e a s u r e surfactants a d s o r p t i o n in oil reservoirs. T h e y found
that in their system surfa c t a n t s are r e m oved f r o m s o l u t i o n b y the sand adsorption, by oil adsorption, and b y the e m u l s i o n phase that is f o rmed b e t w e e n the oil and the w a t e r layers.
A p p l i c a t i o n of R a d i o i s o t o p e s to Water-flooding
A n u m b e r of papers have b e e n p u b l i s h e d on the use of r a d i o i s o t o p e s for w a t e r f l o o d operations* Welge (1955> p. 77) injected trit i a t e d methane, t r i t i u m gas, a n d r a d i o ac t i v e k r y p t o n in one well and d e t e c t e d it at a p r o d u c i n g well* No a d s o r p t i o n was r e p o r t e d on krypton-85, since it
is a n inert gas® The r e s u l t s of titr i a t e d methane, and t r i t i u m gas indi c a t e d little adsorption, therefore, the three tracers i n v e s t i g a t e d are suitable for tracing*
H e c k (195^» P* 31) u s e d four n o n - r a d i o a c t i v e tracers,
dextrose, boron, ammonia, a n d f l o u r e s c e i n in his work. He
stated f rom his studies that either d extrose or b o r o n w o u l d make a s a t i s f a c t o r y trac e r to study the travel of injected w a t e r t h r o u g h B r a d f o r d sand* A m m o n i a w ould not be u s e f u l f or a n y study due to its h i g h adsorption* The f l o u r e s c e i n was a l s o strongly a d s o r b e d by the sand*
Watk i n s (195^, P® 209) was the first i n v e s t i g a t o r to c o n d u c t r e s e a r c h u s i n g r a d i o a c t i v e m a t e r i a l s as w a t e r tfacers in s e c o n d a r y r e c o v e r y operations. B o t h a dye t r acer and. a r a d i o a c t i v e iodine t r a c e r were injected into the i n j e c t i o n we l l w hile normal p r e s s u r e a n d i n j e c t i o n rates were m a i n -tained* He c o n c l u d e d that the c o m p a r a t i v e l y short h a lf-life l i m i t s the use of r a d i o a c t i v e iodine as a flood t r a c e r to s i t u a t i o n s where b r e a k t h r o u g h s of inje c t e d water b e t w e e n
T-1189
7
w e l l s m a y be e x p e c t e d w i t h i n a p p r o x i m a t e l y four half-lifes, or f o u r to five weeks. It was also c o n c l u d e d that r a d i o a c tive' tracers c o uld be u sed successfully, w i t h i n the r e s t r i c t i o n stat e d above to locate channels a n d zones of h i g h p e r m e a b i l i t y in the reservoir.
S m i t h and B r i g h a m (1965* P» 8) p r e s e n t e d the r e s ults of l a b o r a t o r y a n d field inves t i g a t i o n s on the use of t r a c e r in a 5 - spot f l o w a n d compa r e d the field results w i t h a d e v e l oped p r e d i c t i o n equation. The e q u a t i o n a l l o w s the c a l c u l a tion of the a m o u n t of tracer r equired for a g i v e n p r o d u c i n g p e a k concentration. A m m o n i u m t hiocyanate a n d p o t a s s i u m i o dide were used. The test results c o m p a r e d f a v o r a b l y w i t h p r e d i c t e d values, i n dicating that the e q u a t i o n c a n be u s e d w i t h some degr e e of confidence,
B a l d w i n (1966, p, 513) d e v e l o p e d a m e t h o d to p r e d i c t the e l u t i o n profile for a miscible tracer slug in a five spot pattern. The p r e d i c t i o n consists of d i v i d i n g the p a t t e r n into radial eleme n t s a n d a p p l y i n g a n a p p r o x i m a t e radi a l
s o l u t i o n of the d i s p e r s i o n e q u a t i o n to e ach of these e l e ments, To test this p r e d i c t i o n method, l a b o r a t o r y e x p e r i m e n t s were c o n d u c t e d in a f i ve-spot p a t t e r n model, w i t h b e r e a s a ndstone slabs s i m u l a t i n g one q u a r t e r of a five spot. A n a q u e o u s syst e m with triti a t e d w a ter was u s e d a s the t r acer fluid. E f f l u e n t c o n c e n t r a t i o n profiles were o b t a i n e d for
slug v o l u m e s r a n g i n g f r o m 280cc to 408cc w h i c h r e p r e s e n t s 0«7 to 10*2 p e r c e n t of the pore volume* A g r e e m e n t b e t w e e n p r e d i c t e d a n d exper i m e n t a l p rofiles was excellent*
B o t h S m i t h a n d B r i g h a m (19^5> P» 8), a n d B a l d w i n (1966, p. 513), i n t r o d u c e d a d i s p e r s i o n coeff i c i e n t in their p r e d i c t i o n methods, and n e g l e c t e d the effects of a d s o r p t i o n in the final results*
In all the l i t e r a t u r e surveyed, only three a u t h o r s d i s cussed the p r o b l e m of r a d i o a c t i v e a d s o r p t i o n of tracers by r e s
e r voir sands* It was r e p o r t e d that m any w a t e r soluble tracers
are e x c e s s i v e l y or totally a d s o r b e d by r e s e r v o i r sands, t h e r e by, h a ving a v e r y l i m i t e d use in tracing w a t e r floods.
B o l i v a r and F a rouq (1 9 6 7 , P* 2) studied the q u a l i t a tive and q u a n t i t a t i v e flow b e h a v i o r of init i a t e d water,
toluene, and Isopropyl a l c o h o l in porous media* D i f f e r e n t
d i s p l a c e m e n t p r o c e s s e s were c o n s i d e r e d a n d evaluated, a l o n g w i t h the d e t e r m i n a t i o n of the a m o u n t of t r i tium a d s o r b e d on a rock surface* They r e p o r t e d that as m u c h as five p e r c e n t of the t r i t i u m was a d s o r b e d in the core at a f l o w a d v a n c e of two feet p e r day* They a lso r e p o r t e d that this a m o u n t d e crea s e d w i t h an increase in f l o w rate* T heir r e s u l t s i n d i c ated only 0*7 p e r c e n t a d s o r p t i o n w i t h a fluid m o v e m e n t of 20 feet p e r day.
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m a t e r i a l s as tracers, selected 13 that could be q u i c k l y and e a s i l y i d e ntified and whose a n a l y s i s was claimed to be a c c u r a t e w i t h i n five percent. T r i t i a t e d w a t e r was the only r a d i o a c t i v e tracer in the g r o u p of ‘13 tracers first
examined. S a l i c y l i c acid and ethylene diam i n e tetra-acetic
a c i d were e l i m i n a t e d by excessive stati s t i c a l error. The r e m a i n i n g 11 were f l o w e d t h r o u g h a 9~£'t. l i near sandstone m o d e l a n d b r e a k t h r o u g h e l u t i o n curves were obtained. The 13 tracers c o n s i d e r e d were, ethy l e n e d i a m i n e t etra-acetic acid, fluorescein, piric acid, salicylic acid, ammonium, boron, bromide, dicromate, iodide, nitrate, thiocynate,
and chlo r i d e ions, a n d triti a t e d water. These tracers were
u s e d to study the b e h a v i o r of w a t e r f l o o d tracers in c o n s o l i d a t e d cores, b a sed on the effects of t r acer a d s o r p t i o n and d e s o rption. F i n a l l y only three tracers were f i e l d - t e s t e d as b r e a k t h r o u g h tracers. It was c o n c l u d e d that the shape of the e l u t i o n curves d e p ends on diffusion, dispersion, a d s o r p tion, a n d desorptioii effects.
It was a s s u m e d that w h e n the t r a c e r c o n c e n t r a t i o n at a n y time would, equal the initial c o n c e n t r a t i o n no a d s o r p t i o n o c c u r e d a t that g i v e n time.
Wa t kins a n d o t hers (1956> P* ^'1) studied the c h a r a c t e ristics of the f o l l o w i n g r a d i oactive tracers; c e s i u m - 13^, seienium-75» iodine-131* a n d iridium-192, and some n o n - r a d i o
acti v e tracers® It was concl u d e d that cesium, s e l e n i u m a n d d yes such as f l u o r e s c e i n p r oved to be p o o r w a t e r tracers
b ecause of excessive a d s o r p t i o n by a solid surface. C o n
versely, iodine-131 a n d iridium-192 were found to have l o w a d s o r p t i o n c h a r a c t e r i s t i c s a n d to be suitable for use in
tracing w a t e r floods. The g a m m a r a d i a t i o n e m i t t e d by these two r a d i o i s o t o p e s m a k e s possi b l e the p o s i t i v e d e t e r m i n a t i o n of the p o i n t s of w a t e r entry into p r o d u c i n g wells. They a l s o f o u n d the a d s o r p t i o n of d e t e r g e n t s on c l e a n sand s u r
faces is intensive but reversible. The a d s o r p t i o n of d e t e r
g ents by sand s a t u r a t e d w i t h crude oil Is two to three times as great as the a d s o r p t i o n on clean sand. T h e y a l s o found that the c o n c e n t r a t i o n of the d e t e r g e n t is i m p o r t a n t on a d s o r p t i o n 0 They stated that the a d s o r p t i o n of d e t e r g e n t s of l o w c o n c e n t r a t i o n by oily sand is less than a d s o r p t i o n o n c l e a n sando
No l i t e r a t u r e was found w h i c h stated the f u n c t i o n of temp e r a t u r e or c o n c e n t r a t i o n on a d s o r p t i o n of a q u e o u s r a d i o a c t i v e tracers by c l e a n r e s e r v o i r sands.
In the last t w e n t y years interest has i n c r e a s e d in a d s o r p t i o n a s s o c i a t e d with the industrial use of selective a d s o r p t i o n schemes for d i f f i c u l t s e p a r a t i o n a n d for c a t a l y t i c reactors. This p r o b l e m has a l s o been of interest to c h e m i s t s in the t h e o r y of chro m a t o g r a p h y . It has b e e n stated that
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the r a t e - d e t e r m i n i n g step in these p rocesses is the rate of mass or heat t r a n s f e r (heat of adsorption) from the fluid to the solid surface of the r e a c t o r p a cked bed. In c h r o m a t o graphy, it has b e e n assu m e d that the flow of fluid through the bed is so slow there is a n e q u i l i b r i u m e s t a b l i s h e d between
the f l uid and the solid at e a c h p o int of the bed. These s t u d
ies all have a c o m m o n defect of n e g l e c t i n g the effe c t of d i f f u s i o n or conduction. This negl i g e n c e is p r o b a b l y v a lid for very small p a r t i c l e s but the e x p e r imental results are i n c o n clusive • One p u b l i s h e d study by F o s t e r a n d Daniels (1951» P° 986), shows that in a d s o r p t i o n of n i t r o g e n dioxide by silica gel a n d of w a t e r by a c t i v a t e d alumina, the d i f f u s i o n of ad- sorbate on a p article may be the factor to d e t e r m i n e a d s o r p tion. It is clear that d i f f u s i o n of a n a d s o r b a t e flow through a c o l u m n will tend to smear out sharp a d s o r p t i o n due to d i l u
tion at the f low front. This brings up, however, a rather
i n t e r e s t i n g confl i c t on the basic c h a r a c t e r of c h r o m a t o g r a p h i c a n a l y s i s .
The e a r l y t h eory of c h r o m a t o g r a p h y a s s u m e d that e q u i l i b r i u m b e t w e e n a d s o r b e n t and a d s o r b a t e solution was immed i a t e l y
establishedo In this r e s e a r c h it was shown that this e q u i l i b
ri u m v a r i e s with temperature a n d c o n c e n t r a t i o n changes of the adsorbate. This e q u i l i b r i u m w o u l d a l s o vary w i t h f low rate t h r o u g h the core. At low f l o w rates the d i f f u s i o n becomes more pronounced, a l l o w i n g a d s o r p t i o n to a p p r o a c h e q u i l i b r i u m faster.
On the other hand, if f l o w rates are h igh the e q u i l i b r i u m theory b e c o m e s questionable.
With these facts in mind, e quations have been d e r ived by L a p i d u s a n d A d m u n s o n (1952» P» 98^), w h i c h w o uld describe the p h e n o m e n o n of heat and mass t r a n s f e r f r o m a flowing fluid st r e a m to a f ixed solid bed. The d i s c u s s i o n is c onfined to a d s o r p t i o n a l t h o u g h it showed the m o d i f i c a t i o n s needed for
heat transfer. In the d e v e l o p m e n t of the equations, it is
a s s u m e d that the p a c k e d solid bed w o u l d c o n s i s t of porous sphere of u n i f o r m diameter. The solid has a d s o r b e n t p r o p e r ties, a n d ther e f o r e a d s o r b s solute f r o m the a q u e o u s s o l u
tion. The solute m u s t be transferred from the b ulk of the
fl uid a m o n g the p a r t i c l e s to the b o u n d i n g film of fluid s u r
ro u n d i n g a sphereo The solute diffu s e s through the film
a r o u n d the parti c l e a n d is then a d s o r b e d on the surface of
the adsorbent. Hence it is obvious that there are many rate
p r o c e s s e s o c c u r r i n g and that these o ccur in series® The p r o b l e m is to d e t e r m i n e w h i c h one, or ones, control the *
overall rate. It may d e p e n d on the s y s t e m b eing investigated,
a n d it w o u l d be more than coinc i d e n c e if d i f f u s i o n n ever p l a y s a role.
If the initial c o n d i t i o n s of the system, w h i c h include p a r t i c l e s i z e , m e t h o d of packing, a d s o r b e n t p r o p e r t i e s of the solid, c o n c e n t r a t i o n and t e m p erature of the solution, were known,
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it w o u l d be benef i c i a l to have formulas which w ould predict the c o n c e n t r a t i o n of the e f f l u e n t at a n y p oint of the core at a n y time. If the a d s o r b a t e c o n c e n t r a t i o n on a sphere at a g i v e n p oint a n d time is required, the radius of the sphere mu s t be s p ecified since each sphere is in a tran s i e n t state, This resu l t s in c o n c e n t r a t i o n g r a d i e n t s existing on each
particle. Thus it is c lear that once all phys i c a l conditions
are specified, this is a m a t h e m a t i c a l p r o b l e m of four i n d e p e n d e n t v a r i a b l e s if l o n g i t u d i n a l d i f f u s i o n is considered. P h y s i c a l prob l e m s of four inde p e n d e n t v a r i a b l e s are c o m p l i c a ted a n d It is to be expected that the s o l u t i o n of such a s y stem is extre m e l y complicated. Due to the u n c e r t a i n t y of the p h y s i c a l p r o p e r t i e s of the a d s o r b a t e u s e d in this r e search, a m e a n i n g f u l m a t h e m a t i c a l r e l a t i o n s h i p cannot be d etermined.
D e t e r m i n a t i o n of R a d i o a c t i v i t y
In this r e s e a r c h a s c i n t i l l a t i o n a n d decimal scaler
count i n g system was used, Figure 1 (Chase, 1962), shows a
d i a g r a m of a basic s c i n t i l l a t i o n c o u n t i n g system. When a s y s tem like this is used, the a c t i v i t y of the sample Indicated by o b s e r v e d count on the scaler depe n d s on on a n u mber of v a r i a b l e s Including the f o l l o w i n g (Chase, 1 9 6 2 )
lo- N u mber of s c i n t i l l a t i o n s occuring in the phosphor
3. Source intensity C, Geometry
2,~ D i s t r i b u t i o n of intensities of s c i ntillations lA, Source type
B 9 Crystal or p h o s p h o r size and effi c i e n c y 3®~ P h ototube and optical system
A* E f f i c i e n c y of light t r a n s m i s s i o n to cathode of p h ototube
*B. A m p l i f i c a t i o n by p h ototube
(1) Type of tube (Efficiency of light c o n v e r s i o n to e l e ctrical e n e r g y 9 )
•*(2) Poten t i a l a p p l i e d (Controls a m p l i c a t i o n of electrical energy w i t h i n phototube,)
A s s o c i a t e d elect r i c a l circuits
A, P r e a m p l i f i e r b e t w e e n photo t u b e a n d scaler B® D i s c r i m i n a t o r setting on scaler input
These two poin t s will also change w ith changes in v o l tage a p p l i e d to the circuit
C« Coincidence
For a p a r t i c u l a r s c i n t i l l a t o r a n d scaler combination, all of these va.riabl.es (with the e x c e p t i o n of those m a r k e d w i t h a n asterisk) can be kept constant*
Since this r e s e a r c h deals with a c o n t r o l l e d system all of these v a r i a b l e s were kept constant, w i t h the
excep-T-1189
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t ion of the source intensity, The c o m p a r i s o n of the a c t i v i t y of the d i f f e r e n t samples is consi d e r e d h i g h l y accurate, as shown in figure 2 3 *
Two m a i n factors should be consi d e r e d in a c c u r a t e l y m e a s u r i n g the a c tual a c t i v i t y of a c e r t a i n s a m p l e 9 They are the i n s trument e f f i c i e n c y a n d the e f f i c i e n c y d i s t r i b u t i o n of
count i n g time® Instrument effic i e n c y introduces no e r ror if
it can be c o n s i d e r e d c o n s t a n t for a p a r t i c u l a r set of m e a s urements* E f f i c i e n c y of a p a r t i c u l a r c o u nter may be a f f e c t e d by change in r o o m temperature, atmo s p h e r i c pressure, volt a g e
supply, and e rror in r e s e t t i n g the h i g h voltage. Some of
these changes are d i f f i c u l t to control, and were consi d e r e d n e g l i g i b l e in c o u n t i n g the d i f f e r e n t samples. The e f ficient d i s t r i b u t i o n of count i n g time was c a l c u l a t e d for each r u n in o rder to obta i n a h i g h a n d p r actical efficiency.
M A T E R I A L ’A N D A P P A R A T U S
A d s o r b a t e m e d i u m
The a d s o r b a t e used in this r e s e a r c h was a n a q u e o u s s o l u t i o n of s o d i u m i o d i d e-131 a n d s o dium p hophate at d i f f e r ent concentr a t i o n s .
Table No® 2 gives the original c o n c e n t r a t i o n in counts p e r m i n u t e per cubic c e n t i m e t e r for each one of the s o l u tions® P l a i n tap w a t e r was u s e d to prepare the d i f f e r e n t samples (The a m o u n t of m a t e r i a l s p r e s e n t in the w ater is less t han one tenth of one ppm, therefore, any secon d a r y effects that these i m purities could cause on a d s o r p t i o n are c o n s i d e r e d n e g l i g i b l e u n d e r the c o n d i t i o n s studied).
A d s o r b e n t m e d i u m
C l e a n D o w Chemical 175 m e s h sand was the solid a d s o r b ent 0 The sand was c o n d i t i o n e d b y b o i l i n g it in a 6n HC1 s o l u t i o n for a b o u t two hours, and then w a s h e d several times w i t h d i s t i l l e d water* This process was r e p e a t e d until the p H d r o p p e d to seven. The c l e a n sand was then t h o r o u g h l y dried in a n electric o v e n for two days.
T-118.9
17
A p p a r a t u s
Fo u r P r e c i s i o n S c i e n t i f i c Co# c o n s t a n t temperature baths were u s e d to keep the samples at the p r e d e t e r m i n e d t e m p e r a
tures# A S a u t e r e l e ctronic balance was u s e d to w e i g h the e xact a m o u n t of a d s o r b e n t n e c e s s a r y for each run. The a c t i v ity of each sample was m e a s u r e d by a s c i n t i l l a t o r and decimal
scal e r combination# Two Cra-Lab timers w ere u s e d to time
E X P E R I M E N T A L P R O C E D U R E
The c a l c u l a t e d average p o r o s i t y o btained for the ,sand
was 33,37 percent. The resu l t s are tabu l a t e d in Table 1
It was a s s u m e d that the p o r o s i t y r e m a i n e d constant for all the tests.
E a c h c o n c e n t r a t i o n was d i v i d e d into four d i f f e r e n t samples, c o r r e s p o n d i n g to the t e m p e r a t u r e s investigated. Fo r e ach of the samples 200 g r a m s of sand was w e i g h e d and p l a c e d in a f l ask a n d s aturated w ith ?5cc of the aqueous s o l u t i o n of sodium i o d i d e -131 of p r e d e t e r m i n e d activity.
The flasks were i m m e d i a t e l y p l a c e d in the d i f f e r e n t c onstant t e m p erature baths. C o n d e n s e r s were c o n n e c t e d to each f l a s k to elimi n a t e e v a p o r a t i o n of the a q u eous solution.
E v e r y two hours a sample c o n s i s t i n g of one cubic c e n t i m e t e r was e x t r a c t e d from each f lask by means of m i c r o p i
pettes a n d p l aced in d i f f e r e n t test tubes. These test tubes
were u s e d d u r i n g the complete exper i m e n t to m a i n t a i n the g e o m e t r y of the s y s t e m as const a n t as p o s s i b l e 0 The samples
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RESULTS
The r e s ults of this e x p e r i m e n t are s u mmarized in 20 tables a n d p r e s e n t e d g r a p h i c a l l y in 23 figures.
Figure 1 shows a d i a g r a m of the s c i n t i l l a t i o n and d e c i m a l scaler combination.
Figures 2 t h r o u g h 22 show the r e s u l t s obtained from the i n dividual runs (five runs) made at v a r y i n g a c t i v i t i e s of from. 691 cpm/cc to 21,123 cpm/cc. The a d s o r p t i o n b e h a v i o r for each a c t i v i t y was studied u n der t e m p e r a t u r e s of 77° F, 100° F,
150° F, a n d 190° F, The m a x i m u m a d s o r p t i o n r e s u l t e d from this study was 58*93 p e r c e n t at a c o n c e n t r a t i o n of 21,123 cpm/cc at r o o m t e m perature (77° F ) 0 The m i n i m u m a d s o r p t i o n obtained was 0,0^ p e r c e n t at a n a c t i v i t y of 691 cpm/cc at 190° F,
R u n n u m b e r five was made "to examine the effect of t e m p e r ature 011 desorption. The f l a s k c o n t a i n i n g the sand a n d the ra d i o a c t i v e m a t e r i a l at r o o m t e m p erature (77° F) a f t e r e q u i l i b r i u m was r e a ched in run n u m b e r two, was trans f e r r e d to the
190° F c o n s t a n t temperature bath, S a m p l e s were taken every
h i g h t emperature a d s o r p t i o n show a n early p e a k a n d then a
n e g a t i v e slope, until a stabi l i z e d value was reached# The
p r e s e n c e of this p e a k is b elieved to occur beca u s e the sand a n d the source were m i x e d at room temperature (except for r u n number, one), a n d since a d s o r p t i o n happens a l m o s t i n s t a n taneously, it tends to r e a c h a point of h i g h e r a d s o r p t i o n c o r r e s p o n d i n g to a lower temperature# A f t e r 23»5 hours, e q u i l i b r i u m was r e a ched in the d e s o r p t i o n run, showing a m a x i m u m a d s o r p t i o n of 1 0# 7 7 percent, compared to 10,62 p e r
cent o b t a i n e d at 190° F d u r i n g run n u mber two# This shows that the early peaks do not influence the the r e s ults in r e a c h i n g equilibrium,
Calcula.tions were made to evaluate the d e c a y c a l c u l a t e d m a t h e m a t i c a l l y and. the actu a l d e c a y of a sample saved duri n g
run n u m b e r three# Figure 23 shows that b oth the d e cay c a l c u
lated m a t h e m a t i c a l l y a n d the a c tual decay are c o m p a r a b l e 0 Data u t i l i z e d to c onstruct the figures is g i v e n in
tables 3 "fro 20# Least square fits were used to plot the
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21
D I S C U S S I O N
F i g u r e s 2 thro u g h 6 show the curves c o r r e s p o n d i n g to the
f irst run. Figures 3 k show some scatt e r e d p o ints b e l i e v e d
to be c a u s e d by a n e r ror in p i p e t t i n g a n d t ransferance of s a m
ples. It was n o t e d that in the first two hours most of the
total a d s o r p t i o n occurs a n d the a d s o r p t i o n curves a p p e a r l i near
w i t h time r a t h e r than exponential as expected. In order to
m o r e a c c u r a t e l y d e t e r m i n e the early shape of the curves, s a m p les were taken every thirty m i n u t e s for the first two hours
d u r i n g r u n n u m b e r two. Figures 8 to 11, showing the results
of this r u n indicate that at least 30 p e r c e n t of the total
a d s o r p t i o n occurs in the first 30 minutes. Figures 2, ?, 12,
1 7 9 a n d 22 show that a d s o r p t i o n is d e f i n i t e l y a f u n c t i o n of
t e m p e r a t u r e a n d c o n c e n t r a t i o n of sodium.
Run n u m b e r one c o nducted at a n a c t i v i t y of lk,129 cpm/cc shows less a d s o r p t i o n than that of run n u m b e r two cond u c t e d
at a n a c t i v i t y of 10,7^9 cpm/cc.- Initially this would a p p e a r
i m p o s s i b l e but can be expl a i n e d as follows: the c o n c e n t r a t i o n of iodine r e q u i r e d to obtain I k , 129 cpm/cc was m u c h less than
that r e q u i r e d to make a solut i o n six days later with a c o n c e n
t r a t i o n in a c t i v i t y of 10,769 cpm/cc® This shows that the
curves cannot be c o r r e l a t e d on the basis of c o n c e n t r a t i o n in
activity® The only way that a good c o r r e l a t i o n could be e s
tabl i s h e d w o u l d be by k n o w i n g the c o n c e n t r a t i o n of iodine or s o d i u m ions at any time® This a p p r o a c h was a t t e m p t e d during r u n n u m b e r two by the a d s o r p t i o n indicator m e t h o d (Pierce 1 9 6 1 ,
Po J Z k )® This m e t h o d consists of using d i c h l o r o f l u o r c e i n
indicator, d e x t r i n to keep the sample from, coagulating, and
silver nitrate as a t i t r a t i o n reagent. W h e n silver nitrate is
a d d e d to the sodium iodide s o l u t i o n a y e l l o w p r e c i p i t a t e of
silver iodide appears. The e q u i valence point is y e l l o w i s h
orange and v ery h a r d t o detect® The r e s ults so obta i n e d were
of little value b e c ause of the u n c e r t a i n t y of the equivalence point® The other m e t h o d s for d e t e r m i n i n g iodide ions are im p r actical due to the c o m p l e x i t y and the time involved.
The p robable e r r o r in c o u n t i n g a sample was c a l c u l a t e d from-the f o l l o w i n g e q u a t i o n (Chase 1 9 6 2 )j
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wheres
= Total count rate
t^ = Time for count i n g rate r^ = O b s e r v e d b a c k g r o u n d
t-^ = Time for obse r v e d b a c k g r o u n d
The c o r r e c t i o n for h a lf-life was c a l c u l a t e d u s i n g the f o l l o w i n g equations A = w h e r e : A = C o r r e c t e d a c t i v i t y for to, in cpm/cc 2 Aq =s Orig i n a l a c t i v i t y in cpm/cc
ti s= H alf-life of radio a c t i v e mater i a l in hours 2
t = Time in hours
The final e q u a t i o n for iodine-131 having a half life of 193®2 h o urs is,
~ 0 900358t
A = Aq e
E x a m p l e s of these calcu l a t i o n s are prese n t e d in the appendix.
CONCLUSIONS
The c o n c l u s i o n s of the p r e s e n t i n v e s t i g a t i o n are as f o l l o w s :
1# It was f o und that there is a signi f i c a n t d i f f e r e n c e in total a d s o r p t i o n as a f u n c t i o n of temperature; up to 2 k - p e r c e n t d i f f e r e n c e f r o m r o o m temperature
(77° F) to 190° F, as shown d u r i n g r u n n u m b e r four. 2 0 D e s o r p t i o n of the r a d i o a c t i v e m a t e r i a l was found to
be 100 p e r c e n t r e v e r s i b l e w i t h temperature, as shown d u r i n g r u n n u m b e r five#
3o It was found that there is a d e f i n i t e d i f f e r e n c e in total a d s o r p t i o n as a f u n c t i o n of c o n c e n t r a t i o n 0
% The a d s o r p t i o n of sodium iodide-131 increases l i n early w i t h time® It was e x p e c t e d that a d s o r p t i o n w o u l d increase e x p o n e n t i a l l y , w h i c h p r o b a b l y w o u l d be the ca.se if read i n g s were taken at v ery short intervals d u r i n g the first thirty minutes®
5® In r u n n u m b e r four where a c o n c e n t r a t i o n in a c t i v i t y of 691 cpm/cc was used, sodium iodide p r e s e n t e d
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little a d s o r p t i o n in the m a g n i t u d e of 20*53 perc e n t for r oom t e m p erature (77° F) and 0.0^ p e r cent at
190° F. This shows that sodium iodide-131 p r e s e n t s
little a d s o r p t i o n at low c o n c e n t r a t i o n s , and h igh
temperatures* Therefore, sodium iodide-131 w o u l d
be a n a c c e p t a b l e trac e r for w a t e r f l o o d s u n d e r r eser v o i r conditions*
A P P E N D I X T a b l e s : F i g u r e s : C a l c u l a t i o n s : pages 27 t h r o u g h k'} pages k k thro u g h 6 k pages 65 thro u g h 66
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