Metal Complexes in Fossil Fuels - ACS Publications - American

This result i s i n accor- dance with the presumed association of these elements with the original source material (biomass). However, overlapping ran...
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Chapter 9 Metals

in

Crude

Oils,

Asphaltenes,

Bitumen,

and

Kerogen in Molasse Basin, Southern Germany Alfred V. Hirner

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Mineralogisch-Petrographisches Institut der Universität, Theresienstrasse 41, D-8000 München 2, Federal Republic of Germany

In the course of organic geochemical investigations in the Southern German Molasse Basin, the use of trace element studies on maltene, asphaltene and kerogen fractions of crude oils, bitumens and potential source rocks for o i l - o i l and oil-source rock correlations has been tested. The Ni, V and Co contents of crude oil-maltenes and -asphaltenes enabled the differentiation of two o i l families to be made in conjunction with other geochemical analyses. Elemental concentrations in the asphaltene fraction of bitumen and in the kerogen of potential source rocks are similar to those in the corresponding crudes. However, these correlations are not true for Zn and I. It could be shown that Ni in kerogen is associated with the organic phase, whereas Ti is derived from the mineral matrix. Organic substances p l a y a dominant r o l e i n geochemical c y c l i n g , e s p e c i a l l y i nthe l o c a l c o n c e n t r a t i o n o f t r a c e metals (1-3). Metalo r g a n i c a n d o r g a n o m e t a l l i c s p e c i e s i n s e d i m e n t s may o r i g i n a t e f r o m t h e b i o m a s s w i t h o u t m a j o r c h e m i c a l c h a n g e s , o r t h e y may b e f o r m e d d u r i n g sedimentation and/or d i a g e n e s i s from o r g a n i c molecules and metal ions d e r i v e d from d i f f e r e n t b i o g e n i c (biomass) and a b i o g e n i c sources (weathering o f m i n e r a l s ) . T h u s , i n many o f t h e s e g e o chemical cycles i n o r g a n i c as w e l l as organic a s s o c i a t i o n s o f t h e metals are i n v o l v e d , and o f t e n they d i r e c t l y o r i n d i r e c t l y i n t e r a c t w i t h each o t h e r . Complex s i t u a t i o n s r e s u l t , and c o r r e l a t i o n s between metal c o n c e n t r a t i o n s and e i t h e r i n o r g a n i c o r o r g a n i c sediment f r a c t i o n s may n o t a l w a y s b e f o u n d . For example, i n A u s t r a l i a no i l s h a l e s n i c k e l i s a s s o c i a t e d w i t h the o r g a n i c as w e l l as t h e i n o r g a n i c f r a c t i o n s w i t h no a p p a r e n t p r e f e r e n c e ( 4 ) . In o r g a n i c geochemical e x p l o r a t i o n however, o n l y those metals a r e o f s i g n i f i c a n c e , whose c o n c e n t r a t i o n s a r e c l o s e l y a s s o c i a t e d w i t h the o r g a n i c matter. The c o o r d i n a t i o n c h e m i s t r y a n d abundance o f these metals i n crude o i l s p r o v i d e u s e f u l i n f o r m a t i o n on the o r i g i n , m i g r a t i o n , and m a t u r a t i o n o f p e t r o l e u m ( 5 ) .

0097-6156/87/0344-0146$06.00/0 © 1987 American Chemical Society

Filby and Branthaver; Metal Complexes in Fossil Fuels ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

9.

HIRNER

Metab in Mo fasse Basin, Southern

Germany

147

In t h i s s t u d y , f o r m e r i n v e s t i g a t i o n s (6) a r e e x t e n d e d t o t h e m a l t e n e a n d a s p h a l t e n e f r a c t i o n s o f S o u t h e r n German c r u d e o i l s a s w e l l as t h e b i t u m e n and k e r o g e n f r a c t i o n s o f p o t e n t i a l s o u r c e r o c k s of these crudes.

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Samples and

Methods

S e v e r a l geochemical i n v e s t i g a t i o n s o f crude o i l s have r e v e a l e d the e x i s t e n c e o f o n l y two o i l f a m i l i e s i n t h e S o u t h German M o l a s s e B a s i n (6-8) . A l l c r u d e s f o u n d a t t h e s t r a t i g r a p h i e base o f t h e T e r t i a r y b e l o n g t o one g r o u p . The o i l s i n M e s o z o i c r e s e r v o i r s i n t h e w e s t e r n p a r t o f t h e b a s i n a r e s u p p o s e d t o be o f a d i f f e r e n t o r i g i n . Based on t h e s e r e s u l t s , r e p r e s e n t a t i v e samples f r o m each o i l f a m i l y have been s e l e c t e d : M e s o z o i c o i l s : F r o n h o f e n 12, P f u l l e n d o r f 6, O s t r a c h 8 T e r t i a r y b a s e o i l s : M o n c h s r o t , A r l e s r i e d , D a r c h i n g 1, H o h e n r a i n 4. C a r b o n i s o t o p i c s t u d i e s g a v e some e v i d e n c e f o r S a n n o i s i a n a n d R u p e l i a n s e d i m e n t s as p o t e n t i a l s o u r c e r o c k s f o r t h e T e r t i a r y base o i l s (9), a l t h o u g h the samples i n v e s t i g a t e d were s t i l l immature. T h e r e f o r e , t h e b o r e c o r e samples T e i s i n g 1 and H o h e n r a i n 2 have been included i n t h i s study. The c o n c e n t r a t i o n s o f V, C r , F e , Co, N i , Z n , S e , B r , A g a n d I were d e t e r m i n e d b y i n s t r u m e n t a l n e u t r o n a c t i v a t i o n a n a l y s i s as a l r e a d y d e s c r i b e d ( 6 ) ; T i i n k e r o g e n was d e t e r m i n e d b y X - r a y s p e c t r o metry. The a s p h a l t e n e s w e r e s e p a r a t e d b y p r e c i p i t a t i o n w i t h p e t r o l e u m e t h e r 40/60. Trace element c o n c e n t r a t i o n s o f the maltenes (= d e a s p h a l t e d o i l s ) w e r e c a l c u l a t e d b y d i f f e r e n c e , u s i n g t h e a n a l y t i c a l r e s u l t s o f t h e t o t a l o i l and t h e a s p h a l t e n e f r a c t i o n . The c o r e samples were e x t r a c t e d w i t h c h l o r o f o r m / m e t h a n o l (2:1 v/v) f o r t h r e e days. The m a l t e n e a n d t h e a s p h a l t e n e f r a c t i o n s o f t h e e x t r a c t s w e r e analysed separately. Trace element c o n c e n t r a t i o n s To i n d i c a t e t h e c o n c e n t r a t i o n r a n g e s o f t r a c e e l e m e n t s i n S o u t h e r n G e r m a n o i l s a n d k e r o g e n s , p r e v i o u s d a t a (6_, JLO) h a v e b e e n c o m p i l e d a s s h o w n i n F i g u r e 1. T r a c e e l e m e n t c o n c e n t r a t i o n s r a n g e o v e r more t h a n s i x o r d e r s o f magnitude, i . e . from s e v e r a l p a r t s per b i l l i o n to s e v e r a l weight percent. With the e x c e p t i o n o f I, the elements are e n r i c h e d i n the a s p h a l t e n e f r a c t i o n b y a b o u t one o r d e r o f m a g n i t u d e o n t h e a v e r a g e , i n d i c a t i n g an i n c r e a s e o f the m e t a l - b i n d i n g c a p a c i t y w i t h i n c r e a s i n g p o l a r i t y and m o l e c u l a r w e i g h t o f the o r g a n i c m o l e c u l e o r , a l t e r n a t i v e l y , an i n c r e a s e i n m e t a l - t r a p p i n g c a p a c i t y o f a s p h a l t e n e s . Se, Zn, Fe a n d C r a r e e n r i c h e d i n t h e k e r o g e n f r a c t i o n c o m p a r e d t o t h e asphaltenes. W i t h r e s p e c t t o N i , V a n d Co, h o w e v e r , t h e s e two f r a c t i o n s o v e r l a p , a r g u i n g f o r a common o r i g i n o f t h e s e e l e m e n t s i n both f r a c t i o n s . I t must be c o n s i d e r e d , h o w e v e r , t h a t t h e k e r o g e n f r a c t i o n c a n n e v e r be c o m p l e t e l y f r e e o f i n o r g a n i c c o n t r i b u t i o n s .

American Chemical Society,

Library 1155 16th St., N.W. Filby and Branthaver; Metal Complexes in Fossil Fuels Washington, O.C. 2003S

ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

148

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

001 -τη

0-1 ,

I

ppm 10

1 ' • • • • mi

I

100 ι

ι • ι Mii|

1000 1

Ni

I

10000 1

I

ι — ι crude oils ββιββ^ΕΕΕίίΕΕΕΕ^Ηΐί^ββ

V

Downloaded by RUTGERS UNIV on March 8, 2016 | http://pubs.acs.org Publication Date: July 6, 1987 | doi: 10.1021/bk-1987-0344.ch009

• r-

Ni

W^*M»»»»»»»»,A

CO

Se

~^/////////m

CO

^^^^^^^^^^^^^^^^

Se

""WMMM

W/

1

Zn Fe

Zn Fe

w////Aàw//AwmmM»A

Cr

'

0 01

"

0-1

.

Cr

v^>^ i^^^^ ^ mm

(n = 49)

m& asphaltenes ( n = 19 ) • • kerogens ( n = 23 )

V

m

I • I I I I I ll 10 100 ppm

.

I

1000

.

10000

I

F i g u r e 1. Ranges o f t r a c e e l e m e n t c o n c e n t r a t i o n s i n c r u d e a s p h a l t e n e s a n d k e r o g e n f r o m S o u t h e r n G e r m a n y (6_, ICQ .

Filby and Branthaver; Metal Complexes in Fossil Fuels ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

oils,

9.

HIRNER

Meîab

in Molasse Basin, Southern

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Results o f correlation

Germany

149

studies

C o m p a r e d t o t h e T e r t i a r y - b a s e o i l s , t h e M e s o z o i c c r u d e o i l s show s i g n i f i c a n t l y l o w e r c o n t e n t s o f N i , V a n d Co i n t h e m a l t e n e a s w e l l as i n t h e a s p h a l t e n e f r a c t i o n ( F i g u r e 2 ) . This r e s u l t i s i n accordance w i t h t h e presumed a s s o c i a t i o n o f these elements w i t h t h e o r i g i n a l source m a t e r i a l (biomass). However, o v e r l a p p i n g ranges a r e o b s e r v e d i n t h e c a s e o f Zn a n d I , i n d i c a t i n g a n u n k n o w n a s s o c i a t i o n b e t w e e n compounds o f t h e s e e l e m e n t s o r j u s t a c o n t r i b u t i o n f r o m i n o r g a n i c matter ( m i n e r a l s ) . Other arguments f o r t h e l a t t e r h y p o t h e s i s a r e t h e s t r o n g e n r i c h m e n t ( 7 - t o 1 5 - f o l d ) o f Zn i n t h e m a l t e n e s a n d a s p h a l t e n e s o f t h e e x t r a c t e d b i t u m e n , w h e r e a s N i a n d Co i n t h e a s p h a l t e n e f r a c t i o n o f t h e b i t u m e n show s i m i l a r a b u n d a n c e s a s i n t h e crude o i l asphaltenes. B e c a u s e o f t h e e n r i c h m e n t o f t h e p o l a r compounds i n t h e n o n - m i g r a t e d bitumen compared t o t h e m i g r a t e d c r u d e s , a n d b e c a u s e N i a n d Co a r e c o n c e n t r a t e d i n t h e p e t r o l e u m h e a v y e n d s , the observed enrichment (2- t o 6-fold) o f these elements i n t h e bitumen maltenes compared t o t h e o i l maltenes i s u n d e r s t a n d a b l e . I n F i g u r e 2, d a t a f o r Co a n d Zn o b t a i n e d f r o m p r e v i o u s s t u d i e s are i n c l u d e d f o r comparison. T h i s c o u l d n o t be done f o r N i a n d V i n the f i g u r e s used because t h e u s u a l low c o n c e n t r a t i o n s o f these e l e m e n t s i n S o u t h e r n German c r u d e o i l s p r e c l u d e d s h o w i n g b o t h d a t a s e t s o n t h e same g r a p h . Concerning Cr c o n c e n t r a t i o n s , a l l bitumen f r a c t i o n s (1.2 t o 11.1 ppm) l i e w i t h i n t h e r a n g e o f o i l a s p h a l t e n e s ( 0 . 9 t o 2 2 . 7 p p m ) . A l s o , t h e Ag contents o f bitumen maltenes a r e w i t h i n t h e crude o i l r a n g e ( 0 . 0 2 t o 0.32 ppm). Whereas Fe i n b i t u m e n m a l t e n e s (35 t o 38 ppm) i s a s a b u n d a n t as i n crudes, t h e bitumen a s p h a l t e n e s (700 t o 2100 ppm) a r e e n r i c h e d c o m p a r e d t o t h e o i l a s p h a l t e n e s (