Vanadyl Porphyrin Distribution in the Alberta Oil-Sand Bitumens

C h a p t e r 10 Vanadyl

Porphyrin

Distribution

in

the

Alberta

Oil-Sand Bitumens Despina Strong and Royston H. Filby

Downloaded by EAST CAROLINA UNIV on August 16, 2013 | http://pubs.acs.org Publication Date: July 6, 1987 | doi: 10.1021/bk-1987-0344.ch010

Department of Chemistry and Nuclear Radiation Center, Washington State University, Pullman, WA 99164-1300

The vanadyl etio, deoxophylloerythroetio (DPEP), tetrahydrobenzo-DPEP (THBD), benzo-etio, and benzo-DPEP porphyrins were determined by mass spectrometry in chromatographic fractions of Athabasca, Peace River, and Cold Lake o i l sand bitumens. The vanadyl porphyrin distributions were determined in the total bitumen, the maltenes, a n-pentane extract of asphaltenes, and a methanol-acetone extract of the asphaltenes. The vanadyl porphyrins distribute among the bitumen components on the basis of polarity as exhibited by the trend in etio/other porphyrin ratios which increase in the order: maltenes > n-pentane extract > methanol-acetone extract The oil-sand bitumens and components show a consistent increase in a l l etio/other porphyrin ratios in the sequence Athabasca < Peace River < Cold Lake This trend is consistent with the formation of conventional crude oils at depths in the same sequence with subsequent migration to existing reservoirs close to the surface. The etio/THBD and etio/benzo ratios show greater variation than the corresponding etio/DPEP ratios and may have potential use in correlation studies. The g e o c h e m i c a l e v o l u t i o n a n d h i s t o r y o f a n o i l o r s o u r c e r o c k i s r e f l e c t e d i n the composition o f the organic matter and i t s r e l a t i o n s h i p t o t h e o r i g i n a l b i o l o g i c a l p r e c u r s o r s . S e v e r a l compound c l a s s e s a r e known w h o s e b a s i c m o l e c u l a r s k e l e t o n s c a n b e r e l a t e d t o b i o l o g i c a l precursor molecules. Most o f these geochemical biomarkers are hydrocarbons, , isoprenoids, diterpanes, t r i c y c l i c terpanes, p e n t a c y c l i c t r i t e r p a n e s , and steranes (1), but other types i n c l u d i n g s u l f u r c o m p o u n d s (1) a n d t h e m e t a l l o p o r p h y r i n s (2) h a v e a l s o b e e n used i n o i l / o i l and o i l / s o u r c e r o c k c o r r e l a t i o n s , sediment m a t u r i t y s t u d i e s , and i n r e c o n s t r u c t i n g d e p o s i t i o n a l environments. M e t a l l o p o r p h y r i n s were t h e f i r s t biomarkers i d e n t i f i e d i n o i l s (3), b u tthe l a c k o f simple a n a l y t i c a l t e c h n i q u e s f o r t h e s e p a r a t i o n and c h a r a c t e r i z a t i o n o f t h e g e o p o r p h y r i n s a n d t h e u n c e r t a i n t y a b o u t t h e g e o c h e m i c a l o r i g i n a n d e v o l u t i o n o f t h e s e compounds h a s r e s u l t e d in t h e i r l i m i t e d use as biomarkers.

0097-6156/87/0344-0154$06.00/0 © 1987 American Chemical Society

In Metal Complexes in Fossil Fuels; Filby, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.


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Vanadyl Porphyrin Distribution in Alberta

155

B a k e r a n d c o - w o r k e r s (4,J>) f i r s t d o c u m e n t e d t h e d i s t r i b u t i o n o f h o m o l o g o u s members o f t h e t w o m a j o r p o r p h y r i n s t y p e s (DPEP, e t i o ) found i n c r u d e o i l s a n d r e l a t e d m a t e r i a l s . The r e l a t i v e abundances, expressed a s DPEP/etio r a t i o s , provided the f i r s t evidence o f t h e d i f f e r e n c e i n d i s t r i b u t i o n s b e t w e e n t h e two m a j o r t y p e s o f p o r p h y r i n s i n d i f f e r e n t o i l samples. The d i s t r i b u t i o n o f DPEP r e l a t i v e t o e t i o p o r p h y r i n s i n c r u d e o i l s has b e e n shown t o b e a n e x c e l l e n t i n d i c a t o r o f s e d i m e n t m a t u r i t y (2,6»). T h e D P E P / e t i o r a t i o d e c r e a s e s w i t h d e p t h o r i n c r e a s e d t h e r m a l m a t u r a t i o n , a n d i t was p r o p o s e d o r i g i n a l l y (6) t h a t the d e c r e a s e i n t h e r a t i o r e s u l t e d f r o m c o n v e r s i o n o f DPEP t o e t i o m e t a l l o p o r p h y r i n s v i a thermal s c i s s i o n o f the i s o c y c l i c r i n g . T h e c h a n g e i n t h e DPEP/e t i o r a t i o t h r o u g h t h e r m a l c o n v e r s i o n o f DPEP t o e t i o p o r p h y r i n s h a s been q u e s t i o n e d , however, a n d a l t e r n a t i v e mechanisms have been proposed. The f o l l o w i n g mechanisms have been advanced t o e x p l a i n the DPEP/etio r a t i o change i n sediments o r crude o i l s : a ) T h e r m a l c o n v e r s i o n o f DPEP t o e t i o m e t a l l o p o r p h y r i n s ( 6 ) . b ) C o n v e r s i o n o f DPEP p r e c u r s o r s (e.£., p h o r b i d e s ) t o e t i o p r e c u r s o r s (e.£. , c h l o r i n s ) v i a l o w t e m p e r a t u r e o x i d a t i v e o p e n i n g o f t h e 5-membered i s o c y c l i c r i n g d u r i n g d i a g e n e s i s ( 8 ) . c) C a t a g e n e s i s o f k e r o g e n i n the " o i l window" temperature r e g i o n (9) w h i c h r e l e a s e s p r i m a r i l y e t i o p o r p h y r i n s , t h u s d e c r e a s i n g the DPEP/etio r a t i o . T h i s mechanism i s not w e l l understood and h a s not been c o n f i r m e d e x p e r i m e n t a l l y . There i s no obvious c h e m i c a l r e a s o n why e t i o p o r p h y r i n s s h o u l d b e p r e f e r e n t i a l l y a s s o c i a t e d w i t h t h e k e r o g e n compared t o DPEP, a n d r e c e n t e x p e r i m e n t a l w o r k shows t h a t , i n f a c t , both types o f vanadyl porphyrins are s t r o n g l y a s s o c i a t e d with o i l shale kerogens (10). d) D i f f e r e n t r a t e s o f d e g r a d a t i o n ( d e m e t a l l a t i o n , m a c r o c y c l e c l e a v a g e , e t c . ) o f DPEP a n d e t i o p o r p h y r i n s o v e r a g e o l o g i c a l t i m e frame. T h i s h a s been p r o p o s e d b y B a r w i s e (6) a n d c o u l d r e s u l t f r o m a s l i g h t l y higher a c t i v a t i o n energy f o r the degradation o f the e t i o p o r p h y r i n s r e l a t i v e t o DPEP. I t i s important t o recognize the d i f f e r e n c e s i n the four mechanisms and t h e i r i n f l u e n c e on the use o f the DPEP/etio r a t i o i n o i l - o i l and o i l - s o u r c e rock c o r r e l a t i o n s . Mechanisms b) and c ) operate before and d u r i n g the formation o f the o i l from the source rock kerogen, andwould thus determine the DPEP/etio r a t i o i n the source rock and bitumen. Thermal m a t u r a t i o n that f o l l o w e d g e n e r a t i o n of the bitumen i n the source rock o r maturation o f the crude o i l i n the r e s e r v o i r would r e s u l t i n changes i n the DPEP/etio r a t i o o n l y v i a mechanisms a) a n d d ) . S i g n i f i c a n t changes i n the DPEP/etio r a t i o due to m a t u r a t i o n i n a r e s e r v o i r would l i m i t the use o f the r a t i o a s a c o r r e l a t i o n parameter f o r o i l s o r f o r o i l s and source rocks u n l e s s d i f f e r e n c e s i n m a t u r a t i o n among t h e o i l s a r e k n o w n . L i t t l e u s e h a s b e e n made i n c o r r e l a t i o n s t u d i e s o f t h e m o r e c o m p l e x m e t a l l o p o r p h y r i n s (THBD, b e n z o ) b e c a u s e o f t h e u n c e r t a i n t y regarding their origin. The e f f e c t s o f m i g r a t i o n a n d o f b i o d e g r a d a t i o n / w a t e r w a s h i n g i n t h e r e s e r v o i r o n m e t a l l o p o r p h y r i n d i s t r i b u t i o n s must a l s o b e known i n order t o assess the u s e f u l n e s s o f p o r p h y r i n d i s t r i b u t i o n s i n c o r r e l a t i o n s t u d i e s . The e f f e c t o f o i l m i g r a t i o n i s not w e l l u n d e r s t o o d , a l t h o u g h C h a k h m a c h k e v et_ a l . ( 1 1 ) h a v e shown t h a t c h a n g e s i n t h e D P E P / e t i o r a t i o s o f v a n a d y l p o r p h y r i n s o c c u r when o i l s a r e p a s s e d t h r o u g h l a b o r a t o r y columns o f sand and c l a y . There i s evidence t h a t



156

M E T A L C O M P L E X E S IN FOSSIL FUELS

biodégradation d o e s n o t a f f e c t t h e d i s t r i b u t i o n s o f v a n a d y l p o r p h y r i n s i n degraded o i l s (2,12) by d i r e c t b i o l o g i c a l a t t a c k , a l t h o u g h some e n r i c h m e n t o f v a n a d y l r e l a t i v e t o n i c k e l p o r p h y r i n s was o b s e r v e d i n t h e most degraded o i l s o f t h e s u i t e s t u d i e d by P a l m e r (12). In t h i s s t u d y , the v a n a d y l p o r p h y r i n d i s t r i b u t i o n s i n the A t h a b a s c a ( A ) , P e a c e R i v e r ( P R ) , and C o l d L a k e (CL) b i t u m e n s ( n o t e : the term "bitumen" i s used f o r the o i l sands; i t i s not used i n the same c o n t e x t a s s o u r c e r o c k b i t u m e n ) w e r e i n v e s t i g a t e d u s i n g t h e e t i o / D P E P r a t i o as w e l l a s t h e e t i o / T H B D and e t i o / b e n z o p o r p h y r i n ratios. In t h i s s u i t e of h i g h l y biodegraded o i l s , the e t i o / o t h e r p o r p h y r i n r a t i o s were used t o c o r r e l a t e the t h r e e A l b e r t a bitumens. The b i t u m e n s h a v e b e e n shown t o be h i g h l y d e g r a d e d c o n v e n t i o n a l o i l s which p r o b a b l y m i g r a t e d l o n g d i s t a n c e s from deeper source r o c k s w i t h i n t h e b a s i n a n d a r e e m p l a c e d i n t h e s h a l l o w r e s e r v o i r s ( THBD > b e n z o - e t i o > b e n z o - D P E P The c a r b o n n u m b e r s o f t h e v a n a d y l p o r p h y r i n s i n t h e A l b e r t a o i l s a n d b i t u m e n s a n d t h e i r c o m p o n e n t s e x t e n d f r o m C27 t o C 4 0 charac t e r i s t i c o f most g e o p o r p h y r i n s i s o l a t e d from m a t u r e s e d i m e n t s o r f r o m c r u d e o i l s ( 1 9 ) . T h e c a r b o n n u m b e r r a n g e s o f b o t h e t i o a n d DPEP s e r i e s decrease from t h e maltenes t o t h e n-pentane e x t r a c t o f t h e a s p h a l t e n e s and t h e range tends t o be narrowest i n t h e methanolacetone e x t r a c t s . I n t h e m a l t e n e s , t h e h o m o l o g o u s s e r i e s (DPEP, e t i o ) e x t e n d f r o m C27 t o C 4 0 w h e r e a s a r a n g e a s l o w a s C27 t o C34 i s found f o r t h e e t i o p o r p h y r i n s i n t h e Athabasca methanol-acetone extract. A s a r e s u l t , t h e p o r p h y r i n s w i t h c a r b o n n u m b e r >34 r e p r e sent a l a r g e r f r a c t i o n o f t h e t o t a l i n t e n s i t y i n t h e spectrum o f t h e maltenes than f o r the asphaltene. F o r the Athabasca maltenes, 74% of t h e t o t a l i o n i n t e n s i t y i n t h e e t i o s e r i e s can be a t t r i b u t e d t o t h e h o m o l o g u e s C28~C32* ^ contrast, i n the methanol-acetone e x t r a c t , t h e C28-C32 homologues account f o r 90% o f t h e t o t a l e t i o ion intensity. A s i m i l a r t r e n d i s n o t e d f o r t h e DPEP p o r p h y r i n s . The c a r b o n n u m b e r d i s t r i b u t i o n s o f p o r p h y r i n s f r o m P e a c e R i v e r a n d Cold Lake a r e s i m i l a r t o those observed f o r Athabasca. ?

n

Vanadyl P o r p h y r i n D i s t r i b u t i o n s A q u a l i t a t i v e i n t e r p r e t a t i o n o f t h e mass s p e c t r a i s t h a t f r a c t i o n a t i o n i s o c c u r r i n g b e t w e e n t h e e t i o a n d DPEP p o r p h y r i n s i n t h e o i l sand b i t u m e n components. T a b l e I shows t h e e t i o / D P E P , e t i o / T H B D ,



160


27

29

31 CARBON

33

35

37

39

NUMBER

F i g u r e 4. M o l e c u l a r i o n h i s t o g r a m s o f e t i o (....) a n d DPEP ( ) v a n a d y l p o r p h y r i n s i s o l a t e d from A t h a b a s c a a) m a l t e n e s , b) n - p e n t a n e e x t r a c t o f a s p h a l t e n e s , c ) m e t h a n o l - a c e t o n e e x t r a c t of asphaltenes.



STRONG A N D FILBY


1L

Â I rfl

27

\

TîTlYï

irfrm

iI 29

31 33 35 37 CARBON NUMBER

C

39

F i g u r e 5. m o l e c u l a r i o n h i s t o g r a m s o f e t i o (....) a n d DPEP ( ) vanadyl p o r p h y r i n s i s o l a t e d from Peace R i v e r a) maltenes, b) n - p e n t a n e e x t r a c t o f a s p h a l t e n e s , c ) m e t h a n o l - a c e t o n e e x t r a c t of a s p h a l t e n e s .


162


10 0-


it)

27

29

31

33

κ

35

Hi

37

39

CARBON NUMBER

F i g u r e 6. M o l e c u l a r i o n h i s t o g r a m s o f e t i o (....) a n d DPEP ( ) v a n a d y l p o r p h y r i n s i s o l a t e d from C o l d Lake a) m a l t e n e s , b) n - p e n t a n e e x t r a c t o f a s p h a l t e n e s , c ) m e t h a n o l - a c e t o n e e x t r a c t of asphaltenes.



STRONG A N D FILBY


F i g u r e 7. M o l e c u l a r i o n h i s t o g r a m s o f e t i o (....) a n d DPEP ( v a n a d y l p o r p h y r i n aggregates i s o l a t e d from the Athabasca, Peace R i v e r , and Cold Lake bitumens.


In Metal Complexes in Fossil Fuels; Filby, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987. 1.,28 1.,52 2. 58

M e t h a n o l - 0. 34 0.39 0.68 acetone extract of asphal tenes 1,,41 1.,74 3.25

3,.23 4,.81 5.22

6,.00 7..66 11.3

1,.99 3,.35 3.51

Etio/benzo-etio A PR CL 5.92

5.36

2,.45

2,.15

over

1.,51 1.,62 2.,23

1..47 1..40 1,.31

2,.06

1,.40 1,.74 1,.88

THBD/benzo-DPEP A PR CL

scans and c a l c u l a t e d

5.76

5.51

12.77 1 3 . 5

1. 94 2.47

3.,53

7. .73

2, .40 4.55

Etio/benzo-DPEP A PR CL

f r o m MS P a r e n t I o n (CL) O i l Sands

Whole bitumen

porphyrins extracted

i n porphyrin aggregate.

'ϋΡΕΡ i n t e n s i t i e s i n c l u d e n o t o n l y t r u e DPEP s p e c i e s ( i . e _ . , c y c l o e t h a n o ) b u t a l s o i d e n t i c a l mass s p e c i e s o f p o s s i b l e a l t e r n a t e c y c l o a l k a n o (CAP) p o r p h y r i n s ( 9 , 3 1 - 3 2 ) .

E t i o / o t h e r p o r p h y r i n r a t i o s c a l c u l a t e d f r o m a v e r a g e d MS e n t i r e c a r b o n number r a n g e o f e n v e l o p e .

2..40 3..82 4.,20

5..22 6..29

2,.62 3..14

n - P e n t a n e 0.,60 0.66 0.70 extract of asphal tenes

3..75

0..65

Maltenes

0.77 0.84

1,.71

0.56 0.61 0.72

Etio/THBD PR CL

Whole bitumen

b

A

A

Etio/DPEP PR CL

Component

Table I . E t i o / O t h e r R a t i o s f o r Vanadyl P o r p h y r i n s Determined I n t e n s i t i e s f o r A t h a b a s c a ( A ) , Peace R i v e r ( P R ) , and C o l d Lake



10.

STRONG A N D FILBY


165

e t i o / b e n z o - e t i o a n d e t i o / b e n z o - D P E P r a t i o s e x p r e s s e d a s t h e sum o f i o n i n t e n s i t i e s o v e r t h e t o t a l c a r b o n number r a n g e . P o r p h y r i n abundances are expressed r e l a t i v e t o e t i o , the l e a s t p o l a r o f the porphyr i n s s t u d i e d . The e t i o / D P E P o r e t i o / o t h e r r a t i o s i n i n d i v i d u a l components (maltenes, a s p h a l t e n e s , e t c . ) o f the A l b e r t a o i l - s a n d bitumens, o r o f o t h e r c o n v e n t i o n a l crude o i l s , have not been r e p o r t e d , a l t h o u g h B a k e r a n d P a l m e r ( 1 9 ) h a v e shown t h a t t h e DPEP/etio r a t i o o f vanadyl porphyrins i n Boscan maltenes i s d i f f e r e n t t o that of the d e m e t a l l a t e d p o r p h y r i n s e x t r a c t e d from the whole o i l . The d a t a p r e s e n t e d i n T a b l e I i n d i c a t e t h a t p o r p h y r i n a n a l y s e s must be performed on the whole o i l o r bitumen, p a r t i c u l a r l y i f i n t e r - s a m p l e c o m p a r i s o n s a r e t o b e made. For each o i l sand, the etio/DPEP r a t i o o f the vanadyl p o r p h y r i n s decreases i n the order: maltenes > n-pentane e x t r a c t > methanol-acetone e x t r a c t T h i s t r e n d s h o w s c l e a r l y t h a t t h e v a n a d y l e t i o a n d DPEP p o r p h y r i n s d i s t r i b u t e d i f f e r e n t l y between t h e l e s s p o l a r m a l t e n e s a n d t h e more p o l a r f r a c t i o n s o f t h e b i t u m e n , i_.e_. , t h e n - p e n t a n e a n d m e t h a n o l acetone e x t r a c t s o f the asphaltenes. The f a c t o r s w h i c h c o n t r o l t h e d i s t r i b u t i o n o f o r g a n i c c o n s t i t u ents i n the m i c e l l a r s t r u c t u r e o f the bitumen are not w e l l understood, but p r o b a b l y the most i m p o r t a n t a r e p o l a r i t y ( d e t e r m i n e d l a r g e l y b y f u n c t i o n a l i t y ) and m o l e c u l a r w e i g h t ( 1 , 2 0 ) . The m e t a l l o p o r p h y r i n s i n a n o i l - s a n d b i t u m e n w i l l b e d i s t r i b u t e d among c o m p o n e n t s o f t h e m i c r o s t r u c t u r e and thus the d i f f e r e n c e s i n the a s s o c i a t i o n between t h e DPEP a n d e t i o s e r i e s i n t h e m a l t e n e s a n d i n t h e a s p h a l t e n e e x t r a c t s may b e e x p l a i n e d i n t e r m s o f d i f f e r e n c e s i n p o r p h y r i n polarity. I n g e n e r a l , the p o l a r i t y o f each vanadyl p o r p h y r i n c l a s s ( D P E P , e t i o , b e n z o - e t i o , b e n z o - D P E P , THBD) i s i n v e r s e l y p r o p o r t i o n a l to c a r b o n number a s has been o b s e r v e d d u r i n g chromatographic s e p a r a t i o n o f p o r p h y r i n mixtures (21,22). Thus, the h i g h e r carbon n u m b e r h o m o l o g u e s o f b o t h t h e e t i o a n d t h e DPEP a r e r e l a t i v e l y m o r e abundant i n t h e mass s p e c t r a o f t h e l e s s p o l a r m a l t e n e s compared t o the methanol-acetone e x t r a c t s o f the asphaltenes. I n the Athabasca m a l t e n e s , t h e DPEP p o r p h y r i n s w i t h c a r b o n n u m b e r g r e a t e r t h a n 32 c o m p r i s e 3 0 % o f t h e t o t a l i n t e n s i t y o f t h e DPEP s e r i e s , w h e r e a s i n the m e t h a n o l - a c e t o n e e x t r a c t they account f o r o n l y 12% o f the t o t a l DPEP i n t e n s i t y . Porphyrins with i s o c y c l i c rings, i n general,a r e a l s o more p o l a r t h a n p o r p h y r i n s w i t h o u t i s o c y c l i c r i n g s o f s i m i l a r c a r b o n number. H e n c e , t h e D P E P , t h e THBD, a n d t h e b e n z o p o r p h y r i n s o f t h e same c a r b o n n u m b e r a r e m o r e p o l a r t h a n t h e c o r r e s p o n d i n g e t i o porphyrins. Thus, the r a t i o o f etio/DPEP which decreases from maltenes t omethanol-acetone e x t r a c t (Table I ) i s c o n s i s t e n t w i t h an a s s o c i a t i o n o f the m e t a l l o p o r p h y r i n s w i t h the asphaltenes and other bitumen components based on p o l a r i t y . The etio/THBD, e t i o / b e n z o e t i o andetio/benzo-DPEP porphyrin r a t i o s are highest i n the maltenes of each o i l sand bitumen, and a l s o decrease i n the o r d e r : maltenes > n-pentane e x t r a c t > methanol-acetone e x t r a c t T h u s t h i s t r e n d i s a l s o c o n s i s t e n t w i t h p o l a r i t y d i f f e r e n c e s among these porphyrins. The d i s t r i b u t i o n o f t h e v a n a d y l p o r p h y r i n s among b i t u m e n compon e n t s i s i n a g r e e m e n t w i t h p r e v i o u s w o r k ( 1 7 ) i n w h i c h i t w a s shown the p o r p h y r i n s are a c t u a l l y d i s t r i b u t e d between the maltenes and t h e a s p h a l t e n e s i n t h e b i t u m e n a n d do n o t f r a c t i o n a t e d u r i n g a s p h a l t e n e


166



precipitation. Thus t h e r e i s a decrease i n t h e p o l a r / l e s s p o l a r p o r p h y r i n r a t i o s from t h e p o l a r core o f t h e a s p h a l t e n e m i c e l l e through the intermediate p o l a r i t y r e s i n s that " p e p t i z e " t h e m i c e l l e s i n the maltenes t o the r e l a t i v e l y non-polar maltenes i n which the l e s s p o l a r porphyrins predominate. No e v i d e n c e h a s b e e n f o u n d f o r the u n u s u a l l y h i g h molecular weight p o r p h y r i n s i n t h e a s p h a l t e n e s , suggested by Blumer and Snyder (23), o r f o r t h e v e r y complex, a r o m a t i c t y p e p o r p h y r i n s ( a p a r t f r o m THBD a n d b e n z o ) a s s u g g e s t e d b y Y e n ( 2 4 ) o r J a c o b s ( 2 5 ) . H o w e v e r , s u c h p o r p h y r i n s may b e s t r o n g l y a s s o c i a t e d w i t h t h e a s p h a l t e n e s and a r e n o t e x t r a c t a b l e w i t h methanol-acetone, and thus a r e c l a s s i f i e d w i t h t h e "non-porphyrin" vanadium. The m e t h a n o l - a c e t o n e e x t r a c t o f t h e w h o l e b i t u m e n ( s i m i l a r t o the p o r p h y r i n aggregate o b t a i n e d from c o n v e n t i o n a l o i l s ) has v a l u e s f o r e t i o / o t h e r p o r p h y r i n r a t i o s t h a t a r e i n t e r m e d i a t e between t h e maltenes and t h e methanol-acetone e x t r a c t o f t h e asphaltenes. I t i s c l e a r , however, t h a t t h e p o r p h y r i n abundances i n t h e p o r p h y r i n aggreg a t e s o f o i l s o f s i m i l a r o r i g i n a n d t h e r m a l h i s t o r y may b e i n f l u e n c e d by t h e amount a n d p o l a r i t y o f t h e a s p h a l t e n e s ( o r p o l a r c o m p o n e n t s o f the r e s i n s ) . A l s o , t h e degree o f e x t r a c t i o n i s important because i t i s n o t known what f r a c t i o n o f t h e v a n a d i u m r e m a i n i n g i n t h e t e r t i a r y a s p h a l t e n e s (between 52.8-63.9% o f t o t a l ) (17) i s v a n a d y l p o r p h y r i n , a n d w h a t t h e n a t u r e o f t h e s e v a n a d y l p o r p h y r i n s m i g h t b e . T h e UV s p e c t r u m o f t h e e x t r a c t e d t e r t i a r y a s p h a l t e n e s t i l l shows a S o r e t a b s o r b a n c e a t 4 0 8 nm. Based on t h e e x t r a c t i o n d a t a , i t w o u l d be expected that the vanadyl porphyrins remaining i n t h e e x t r a c t e d a s p h a l t e n e s w o u l d c o n t a i n a h i g h e r p r o p o r t i o n o f THBD a n d b e n z o , a n d possibly other species. P o r p h y r i n R a t i o s as Geochemical

Correlation

Parameters

The s t r o n g a s s o c i a t i o n o f t h e p o r p h y r i n s w i t h t h e a s p h a l t e n e s i n t h e o i l - s a n d bitumens has i m p l i c a t i o n s regarding t h e i r f a t e during the m i g r a t i o n o f t h e o r i g i n a l o i l and subsequent a l t e r a t i o n processes i n the r e s e r v o i r . R u b i n s t e i n e t ad. ( 2 6 , 2 7 ) h a v e shown t h a t g e o c h e m i c a l b i o m a r k e r s c a n be l i b e r a t e d from t h e a s p h a l t e n e s d u r i n g p y r o l y s i s . T h i s i n v e s t i g a t i o n shows t h a t m e t a l l o p o r p h y r i n s c a n a l s o be i s o l a t e d from t h e a s p h a l t e n e s and t h a t t h e d i s t r i b u t i o n s o f p o r p h y r i n t y p e s a s s o c i a t e d w i t h t h e a s p h a l t e n e s a r e d i f f e r e n t from those i n t h e maltenes. I t h a s a l s o b e e n shown t h a t i t i s n o t n e c e s s a r y t o pyrolyze the asphaltenes t o extract a substantial f r a c t i o n ofthe vanadium a s vanadyl p o r p h y r i n s . The e t i o / o t h e r p o r p h y r i n r a t i o s o f t h e t h r e e o i l s a n d s a r e shown g r a p h i c a l l y i n F i g u r e 8 a n d g e o c h e m i c a l d a t a a r e g i v e n i n T a b l e I I . The e t i o / D P E P r a t i o i n c r e a s e s i n t h e o r d e r Athabasca < Peace R i v e r < Cold Lake T h i s t r e n d i s seen i n each o f t h e bitumen components. T h e same t r e n d i s e x h i b i t e d by t h e etio/THBD, and t h e e t i o / b e n z o p o r p h y r i n r a t i o s i n the bitumen components. T h e e t i o / D P E P r a t i o s may b e i n t e r p r e t e d t o r e p r e s e n t a m a t u r a t i o n s e q u e n c e among t h e t h r e e b i t u m e n s , although the A t h a b a s c a , Peace R i v e r , and C o l d Lake o i l sand samples were a l l r e s e r v o i r e d a t l e s s t h a n 3 0 0 m; t h u s , i n s i t u m a t u r a t i o n c a n n o t explain the porphyrin distributions. The o i l sands have been subj e c t e d a l s o t o extensive biodegradation/water washing (13,14), but



F i g u r e 8. Etio/DPEP ( # ) , etio/THBD ( Ο ) , e t i o / b e n z o - e t i o (·) and e t i o / b e n z o - D P E P ( e ) r a t i o s f o r b i t u m e n components o f A t h a b a s c a ( A ) , P e a c e R i v e r ( P R ) , and C o l d L a k e (CL) o i l s a n d s .


ON -J

168


T a b l e I I . G e o c h e m i c a l , V, N i a n d V a n a d y l P o r p h y r i n D a t a A t h a b a s c a , Peace R i v e r and C o l d Lake O i l Sands

f o r the

Property

Lake

Athabasca


Present depth reservoir

of

0

D e g r e e o f biodégradation V

Very

concentration

(us/e) Ni

V/Ni VOP

Cold

444

169

high

196 +

Very

3

high

180 ±

High

3

191 ±

3

74.8

±

2.6

±

3

62.4

±

2.9

±

1

62.6+5

a

a

(yg

V/g)

Extractable

b

V0P

b , C

DPEP/(DPEP +

etio)

0.1

0.2

47.2%

51.1%

40.1%

1.80

1.64

1.39

0.64

0.62

0.58

Taken from S t r o n g

(17); V/Ni r a t i o contents

m u l t i p l i e d by Roberts (9).

±

76.8

d

"Expressed as p e r c e n t

3.1

92.0

Vanadyl

porphyrin

0.1

92.5

DPEP/etio

Wen and

River

a

concentration

(yg/g)

Peace

of t o t a l

100,

i s demetal weight

estimated

ratio.

t o have r e l a t i v e

V i n bitumen

e r r o r ^10-15%.

(17).

e q u i v a l e n t t o %DPEP c a l c u l a t e d

by

Barwise



10.

STRONG A N D FILBY


169

p r e v i o u s w o r k b y P a l m e r ( 1 2 ) a n d B a r w i s e ( 2 ) h a s shown t h a t biodégradation has l i t t l e e f f e c t on the vanadyl p o r p h y r i n d i s t r i b u t i o n s o f heavy o i l s . The t o t a l v a n a d y l p o r p h y r i n c o n t e n t s o f t h e o i l - s a n d b i t u m e n s ( A : 9 2 . 5 y g V / g ; PR: 9 2 . 0 y g V / g ; C L : 7 6 . 8 y g V / g ) a r e h i g h a n d n o t s t a t i s t i c a l l y d i f f e r e n t among t h e t h r e e s a m p l e s , c o n firming the r e l a t i v e l y l i t t l e , i f any, e f f e c t o f biodegradation/water washing. The e t i o / D P E P a n d e t i o / o t h e r p o r p h y r i n r a t i o s thus p r o b a b l y r e f l e c t the depth (temperature) o f formation o f t h e o r i g i n a l crude o i l s p r i o r t o m i g r a t i o n t o t h e present r e s e r v o i r s , because i n r e s e r v o i r m a t u r a t i o n h a s been s m a l l (assuming s i m i l a r m i g r a t i o n pathways). The o r i g i n o f t h e b i t u m e n i n t h e o i l sands h a s been d e b a t e d , b u t most t h e o r i e s i n v o l v e l o n g - r a n g e m i g r a t i o n o f c o n v e n t i o n a l o i l s from down-dip Lower Cretaceous source r o c k s (13,14,28), a l t h o u g h r e c e n t r e s e a r c h (16,29) i n d i c a t e s p o s s i b l e Devonian c o n t r i butions. Thus i f t h e t h e o r e t i c a l DPEP/(DPEP + e t i o ) v e r s u s e x p u l s i o n t e m p e r a t u r e c u r v e o f B a r w i s e (8) i s u s e d (assumes 10 KJ/mole d i f f e r e n c e s i n a c t i v a t i o n e n e r g y f o r e t i o a n d DPEP d e g r a d a t i o n ) , e x p u l s i o n t e m p e r a t u r e s o f 145-150 C a r e computed. Although these t e m p e r a t u r e s a r e p r o b a b l y t o o h i g h , t h e y do c o n f i r m t h e f o r m a t i o n , or e x p u l s i o n , o f t h e o r i g i n a l crude o i l s a t depths g r e a t e r than t h e present r e s e r v o i r s and i n d i c a t e a depth o f o r i g i n a l o i l formation i n the sequence Athabasca < Peace R i v e r < Cold Lake. The e f f e c t o f l o n g r a n g e m i g r a t i o n o f c r u d e o i l s o n t h e v a n a d y l p o r p h y r i n d i s t r i b u t i o n s h a s n o t b e e n a s s e s s e d b u t may b e o f s i g n i ficance given the d i f f e r e n t p o l a r i t i e s o f d i f f e r e n t porphyrin types. Burkova e t a l . (30) examined t h e v a n a d y l p o r p h y r i n s from t h e Surgut, W. S i b e r i a n o i l f i e l d a n d c o n c l u d e d t h a t t h e p r o p o r t i o n o f n o n - p o l a r v a n a d y l p o r p h y r i n s ( d e f i n e d b y TLC Rf v a l u e s ) i n c r e a s e d w i t h i n c r e a s e d migration distance. I ft h e o r i g i n a l o i l migrated from deeper source rocks a s a s i n g l e phase, t h e d i f f e r e n t a s s o c i a t i o n o f m e t a l l o p o r p h y r i n s i n t h e b u l k hydrocarbon phase (maltenes) and i n t h e a s p h a l t e n e s may h a v e a f f e c t e d t h e e t i o / D P E P , e t i o / T H B D , a n d e t i o / b e n z o d i s t r i b u t i o n s d u r i n g t h e m i g r a t i o n from t h e source rock t o r e s e r v o i r . The " f r e e " p o r p h y r i n s w h i c h a r e p r e s e n t i n t h e h y d r o c a r b o n o r m a l t e n e s f r a c t i o n o f t h e o i l may h a v e b e e n m o r e s u b j e c t t o d i f f e r e n t i a l chromatographic r e t e n t i o n o f the rock matrix than the porphyrins present w i t h i n t h e a s p h a l t e n e m i c e l l e s . These a s p h a l t e n e - a s s o c i a t e d p o r p h y r i n s were p r o b a b l y p r o t e c t e d d u r i n g m i g r a t i o n much l i k e b i o s e n s i t i v e m a r k e r compounds a r e p r o t e c t e d w i t h i n t h e a s p h a l t e n e d u r i n g biodégradation ( 2 6 , 2 7 ) . The e t i o / o t h e r p o r p h y r i n r a t i o s f o r t h e m e t h a n o l - a c e t o n e e x t r a c t o f t h e a s p h a l t e n e s ( F i g u r e 8 ) show s i m i l a r t r e n d s among t h e t h r e e o i l s a n d s , b u t t h e r e a r e q u a l i t a t i v e d i f f e r e n c e s i n t h e m e t h a n o l - a c e t o n e e x t r a c t s compared t o t h e r a t i o s f o r t h e o t h e r bitumen components. T h e s e d i f f e r e n c e s may r e f l e c t the e f f e c t s o f m i g r a t i o n , w h i c h need t o be f u r t h e r e v a l u a t e d . The e t i o / o t h e r p o r p h y r i n r a t i o s f o r c o m p o n e n t s o f t h e t h r e e o i l s a n d b i t u m e n s s h o w n i n F i g u r e 8 show t h a t t h e t r e n d s f o r t h e e t i o / THBD a n d e t i o / b e n z o p o r p h y r i n r a t i o s a r e s i m i l a r t o t h a t o b s e r v e d for t h e etio/DPEP r a t i o . H o w e v e r , d i f f e r e n c e s among t h e e t i o / T H B D a n d e t i o / b e n z o r a t i o s f o r t h e t h r e e o i l s a n d s a r e g r e a t e r t h a n among the etio/DPEP r a t i o s , p a r t i c u l a r l y f o r t h e p o r p h y r i n aggregate and the methanol e x t r a c t o f t h e asphaltenes. I f t h e d i f f e r e n c e s among the etio/THBD a n d e t i o / b e n z o r a t i o s a r e due t o m a t u r a t i o n e f f e c t s , t h e n t h e s e p o r p h y r i n r a t i o s may b e m o r e s e n s i t i v e i n d i c a t o r s o f



170


maturation effects. However, u n t i l t h e o r i g i n o f t h e s e s p e c i e s h a s been determined and t h e e f f e c t s o f m i g r a t i o n a s s e s s e d , u s e o f these r a t i o s i sunwarranted. The p o r p h y r i n f r a c t i o n a t i o n d a t a a l s o i n d i c a t e t h a t t h e change i n etio/DPEP r a t i o i n t h e o i l sand bitumens i s n o t a r e s u l t o f a DPEP t o e t i o c o n v e r s i o n d u r i n g b i t u m e n m a t u r a t i o n . T h e r e i s n o o b v i o u s g e n e t i c r e l a t i o n s h i p among t h e e t i o a n d t h e TH3D a n d b e n z o p o r p h y r i n s , b u t t h e same t r e n d i n t h e e t i o / o t h e r p o r p h y r i n r a t i o s as f o r the etio/DPEP r a t i o s i s observed. R e c e n t l y K a u r e t a l . ( 3 1 ) h a v e shown t h a t t h e b e n z o - D P E P p o r p h y r i n s c o n t a i n t h e a r o m a t i c r i n g o n t h e C-7 a n d C-8 p o s i t i o n s (B r i n g ) r a t h e r t h a n t h e C-17 a n d C-18 p o s i t i o n s (D r i n g ) p r o p o s e d b y B a r w i s e a n d R o b e r t s (9) who a l s o p r o p o s e d t h a t t h e 6-membered r i n g i n THBD w a s o n t h e D r i n g . T h i s would i m p l y no g e n e t i c r e l a t i o n s h i p b e t w e e n b e n z o - D P E P a n d THBD p o r p h y r i n s u n l e s s t h e s t r u c t u r e o f THBD p r o p o s e d b y B a r w i s e a n d R o b e r t s (9) i s i n c o r r e c t . I f , however, t h e 6-membered r i n g i n THBD a n d b e n z o - D P E P p o r p h y r i n s a r e b o t h o n t h e Β r i n g , t h e n t h e b e n z o - D P E P may a r i s e b y d e h y d r o g e n a t i o n o f THBD during maturation. I f t h i s i s t h e c a s e , t h e THBD/benzo-DPEP r a t i o should decrease during maturation. The THBD/benzo-DPEP r a t i o s shown i n T a b l e I show no o b v i o u s p a t t e r n ; f o r t h e p o r p h y r i n a g g r e g a t e , t h e r e v e r s e o r d e r i s s e e n , jL.

Vanadyl Porphyrin Distribution in the Alberta Oil-Sand Bitumens

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