1998 Aizenshtat Etal 1998

8/12/2019 1998 Aizenshtat Etal 1998

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P e r g a m o nOrg . Ge oc he m. Vol. 29, No. 1-3, pp. 701-712, 1998 1998 Elsevier Science Ltd. A ll rights reservedPrinted in Great BritainP I I : S0 14 6-6 38 0(9 8)0 00 65 -5 0146-6380/98/$- see front mat ter

O i l - o i l c o r r e l a ti o n a n d p o t e n t i a l so u r c e r o c k s f o r o i l s i n P a l e o z o i cr e se r v oi r r o ck s i n t h e T a t a r i a a n d P e r m b a s i n s R u s s i a

Z E E V A I Z E N S H T A T ' * , S H I M O N F E I N S T E I N 2, I R E N A M I L O S L A V S K I ' ,Z O Y A Y A K U B S O N 3 a nd C H R I S T O F . I . Y A K U B S O N 3

' Orga n i c C he mi s t ry De pa r t me nt a nd C a sa l i Ins ti t u te , T he He bre w Uni ve r s i t y o f J e rusa le m, J e rusa l e m,91904, Israe l , 2Department of Geolo gy and Env i ronm enta l Sc iences , Ben Gurio n U nivers i ty of theNegev , Beer-Sheva , 84105, Israe l and 3W orld Lab ora to ry, In s t i tute of Oi l , Gas an d En ergy Econom ics ,Leninsky prosp. , 63. 117917 GSP-1 M oscow , RussiaA b s t r a c t W e pre se n t a s tudy o f 45 o i l s a mpl es f rom t he T a t a r i a a nd Pe rm ba s i ns in t he Vol g o-U ra lregion, Russia . Crude samples were obta ined from 30 oi l f i e lds across the two basins . Samples a re fromva r i a b l e c a rbona t e a nd s a nds t one r e se rvo i r roc ks r a ng i ng i n a ge be t we e n Gi ve t i a n (De voni a n) a ndKazanian (Permian) a t various present -day depths . Oi l -oi l corre la t ion suggest s tha t despi te the divers i tyof the reservoi r rocks and vast geographic di s t r ibut ion, a l l oi l s s tudied are c lass i f i ed, in genera l , into as ingular gene t ic oi l fami ly, wi th poss ible indica t ion for secondary subdivi s ion into two subgroups. Thema jor charac ter i s t i cs of the oi l s , i.e . low Pr/Ph ra t io, CP I ~ l , re la t ive ly high C27-s te rane, low p ro-port io ns o f rearranged s teranes, C29_>C30-hopane, low ra t io o f Ts to Tm h opan es , high su l fur contenta nd h i gh ra t i o o f V t o Ni , a l l sugges t a r e duc i ng a nd p roba b l y hype r sa l ine de pos i t i ona l e nv i ronme ntfor the source rock which was l ike ly carbonate-r ich. Thermal maturi ty indica ted for a l l the oi l s i s in theuppe r r a nge o f t he ma i n pha se o f o i l ge ne ra t i on . Fur t he rmore , t he c ha ra c t e r i s t i c s ob t a i ne d fo r t hel i gh t-e nd norma l a l ka ne s a nd m ono-a rom a t i c s i nd i c a te no s ign if ic a nt de gra da t i on fo r mo s t o f t hesamples . Hence , the re la t ive ly high speci f ic gravi ty of the oi l samples i s not a t t r ib uted to e i ther matu ri tyor degrada t ion effec t s . Di ffe rence recorded in Pr/Ph ra t io be tween samples from Perm basin a re t enta-t ive ly a t t r ibuted to spa t ia l varia t ions in deposi t ion a l envi ron men t condi t ions . Di ffe rences in t r ieyc lic t e r-panes content in samples from both basins poss ibly indica te some varia t ions in input of spec i f icT a s m a n i t e s ) a l ga e to t he i r sourc e roc k . P re l i m i na ry e xa mi na t i on o f a n e x t ra c t o f De von i a n Do ma n i cForm a t i on s a mpl e c or robora t e s t he pos s i b i li t y t ha t t h i s fo rma t i on i s a ma j or sourc e roc k fo r t he o i l s i nbo th the Tatar ia an d Pe rm basins . 1998 Elsevier Sc ience Ltd. Al l r ights reservedK e y w o r d s Oil o i l corre la t ion, Ta tar ia -P erm basins , Pa leozo ic reservoi rs , bio mark ers , T a s m e n i t e

INT R ODUC T IONT h e T a t a r i a a n d P e r m b a s i n s a r e t w o o f t h e p r o l i fi co i l p r o d u c i n g b a s in s i n th e V o l g o - U r a l r e g i o n( F i g . 1 ) , a m o n g t h e g r e a t e s t P a l e o z o i c o i l b a s in s i nt h e w o r l d . P a l e o z o i c c r u s t a l e p e i r o g e n y a n d t r a n s -g r e s s i o n - r e g r e s s i o n c y c le s r es u l t e d i n a r e g i o n a ls t r a t i g r a p h i c p a t t e r n o f c l a s t i c - c a r b o n a t e r o c k sa l t e r n a t i o n s ( F i g . 2 ) , w h e r e a s c o n t e m p o r a n e o u se x t e n s i v e f a u l t i n g a n d b l o c k r o t a t i o n d u r i n g s e d i -m e n t a t i o n r e s u l t e d i n r e la t i v e ly s h a r p l i t h o f a c i e sa n d i s o p a c h v a r ia t i o n s ( K r o p o t k i n , 1 97 1 ; G u t m a na n d O s i p o v a , 1 9 82 ; K o z l o v e t a l . , 1 9 95 ). T h i s c o m -b i n a t i o n o f r e g i o n a l t r a n s g r e s s i o n - r e g r e s s i o n c y c le sw i t h b l o c k f a u l t i n g a n d l i t h o f a c i es v a r i a t i o n f o r mo p t i m a l c o n d i t i o n s f o r d e v e l o p m e n t o f b o t h s o u r c ea n d r e s e r v o i r r o c k s a s w e l l a s t r a p p i n g c o n d i t i o n s .

P a y z o n e s i n t h e T a t a r i a a n d P e r m b a s i n s c o m -p r i s e a w i d e d i v e r s i ty o f c l a s ti c a n d c a r b o n a t eP a l e o z o i c r e s e r v o i r r o c k s r a n g i n g i n a g e b e t w e e n

*To who m correspon dence should be addressed. Te l :+ 972-2-65855 61; Fax : + 972-2-65282 50; e-mail :[email protected] i .ac . i l .

D e v o n i a n t o P e r m i a n ( F i g . 2 ) a n d a r e d i s t r i b u t e do v e r i m m e n s e t e r r a i n ( F i g . 1 ). I n t h e p r e s e n t s t u d yw e a n a l y z e d 4 5 o i l s a m p l e s f r o m 3 0 fi e ld s a c r o s s t h eT a t a r i a a n d P e r m b a s i n s ( T a b l e l ( a - b ) ) . W e p e r -f o r m e d d e t a i le d o r g a n i c a n d i n o r g a n i c c h e m i c a lc h a r a c t e r i z a t i o n o f t h e s a m p l e s s t u d i e d i n o r d e r t oe n a b l e c o m p r e h e n s i v e o i l - o i l c o r r e l a t i o n , c la s s if i -c a t i o n o f o i l s i n t o g e n e t i c f a m i l i e s , d e f i n e t h e i r t h e r -m a l m a t u r i t y a n d d i f f e r e n t i a t e p o s s i b l e s e c o n d a r ym o d i f i c a t i o n s .

ANALYTICAL METHO DSO i l a n a l y s is w a s c o n d u c t e d a c c o r d i n g t o s t a n d a r d

m e t h o d s ( e .g . A i z e n s h t a t , 1 9 9 2 c . f. ). E l e m e n t a la n a l y s i s f o r C , H , N w a s c o n d u c t e d o n a P e r k i nE l m e r a n a l y z e r a n d s u l f u r w a s d e t e r m i n e d b y b o t hS h o n i g e r c o m b u s t i o n a n d W a g n e r t i t r a ti o nm e t h o d s . T h e a n a l y s is o f t h e g a s o l i n e f r a c t i o n

( l i g h t d i s t i l la t e ) w a s p e r f o r m e d o n a H P 5 8 8 0 g asc h r o m a t o g r a p h f it te d w i th a P O N A 5 0 m c a p i l la r yc o l u m n w i t h H e c a rr i e r g a s a n d p r o g r a m m e d h e a t -i n g f r o m 4 0 - 2 8 0 C a t a 2 C / m i n r a t e . T h e C 1 5 +s a t u r at e h y d r o c a r b o n s w e r e a n a ly z e d b y a T r a c o r

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Tataria-Perm (Russia) oils geochemical correlation 703

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F A S T U R S K Y ,_ . . .~ A K M A R I A N '; H I K H A N S K Y . . - . - . - . - .- _ . _ _ -A S S E L I A N - - - '- ' - -- _ - - - - .

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3 O B R I K O V S K YV I S E A N . . . . .

R A D A E V S K Y - ' - '- ~ - - - - i . . ' - -2~ . - . '~B L C H O V S K Y - ' - '- ' - -

F O U R N A I S I A N K I Z E L O V S K Y : . , .. , . , . . . . eF A M E N N I A N 0 A N K O V O - , . . . . .L E B E D J A N S K Y . . . .. .F R A S N I A N I O M A N I K~ I V E T I A N [U N E V S K Y i E I F E L I A N K O Y V E N S K Y

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Fig. 2. Summary of the Paleozoic stratigraphy and generalized lithology. Dots indicate reservoir rockintervals from which oil samples studied were obtained (Table 1).565 gas chromatograph fitted with 25 m DB-5 capil-lary columns with He carrier gas and 4C/min pro-grammed heating from 50-315C. Sterane andhopane mass chromatograms were obtained by GC /MS/C equipped with a HP 5790A gas chromato-graph directly coupled to the source of a ZAB-IIF(VG analytical) double-focusing mass spec-trometer. The GC operation conditions were similarto those employed for the GC C]5+ analysis. Themass spectrometer operating condi tions were: EImode, elec tron energy = 70 eV, source temperat ure:225C, acceleration volts = 8 kV, instru ment resol-ution > 2500 for SIR mode. The quantificat ion ofboth vanadium and nickel was determined by EPRand XR F (X-Ray Fluorescence, using Pu 238 sourceand s ilicon- lithium detector) methods which in ad-

dition to total concentration enable differentiationof the VO-porphyrin-complexed v r s u s the total va-nadium content. The results obtained for Ni andVO-porpyrins were further supported by UV-Visspectroscopy using selected wavelengths for quanti-fication of the por phyrin families.

R E S U L T S

The oils studied are heavy with specific gravityranging between 0.91 and 0.95 g/ml and viscosities(20C) between 70-102 CP. Their elemental compo-sition shows H/C ratios 1.7-1.9 and S/C 0.018-0.022 with one or two exceptions. Sulfur contentwas measured in 15 of the Tataria and 10 Permbasins oil samples and the concentration recorded


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7 0 4 Z . A i z e n s h t a tT a b l e 1 . D e t a i l s (f ie ld , f o r m a t i o n a n d d e p t h ) o f s a m p l e s s t u d i e d (a = T a t a r i a b a s i n , b = P e r m b a s i n )

T a t a r i a ( a ) P e r m ( b )S a m p l e f i el d a g e / f o r m a t i o n d e p t h ( m ) S a m p l e f i el d a g e / f o r m a t i o n d e p t h ( m )1 B u r e i k i n s k o e B o b r i k o v s k y 1 3 0 0 1 3 87 l K u l a s o v o2 B u r e i k i n sk o e B o b r i k o v s k y 2 K u d u m k a r3 B u r e i k i n s k o e V e r e i s k y 1 0 4 0 3 K a s i '4 B u r e i k i n sk o e V e r e i sk y 4 K o k u '5 I l m o v s k o e B o b r i k o v s k y 1 2 50 5 K r a s n o k a m s k a j a6 N u r l a t s k o e B a s h k i r s k y 6 T i c h o v s k a j a7 N u r l a t s k o e B o b r i k o v s k y 1 2 4 0 7 S h a t r a t s k a j a8 N u r l a ts k o e D o 8 K a m e n n u ' L o gB e s h n e v o9 P o l e n s k o e V e r e is k o e 9 5 9 - 1 0 2 6 9 K a m e n n u ' L o gB e s h n e v o -1 0 P o l e n s k o e B a s h k i r s k y 1 0 68 1 0 K a m e n n u ' L o gB e s h n e v o -1 1 P o l e n s k o e B o b r i k o v s k y 1 2 6 4 1 1 V s e v o l o d o - V i l v a1 2 N o v o e l c h e v s k o e B a s h k i r s k y 8 4 0 1 2 B a r d u m1 3 N o v o e l c h e v s k o e D 1 1 3 G e j s k o e1 4 N o v o e l c h e v s k o e T u r n e i s k y 1 0 41 1 4 B o r o v o1 5 S i r e n e v s k o e B o b r i k o v s k y 1 0 5 0 1 5 S t o l b o v s k iB e r k e t - S h a c h t a L i n i n a ,1 6 K l u c h e v s k o e T u r n e i s k y 1 6 K i z i lS t u d e n o -1 7 K l u c h e v s k o e U f i m s k y 1 7 P e s c h a n k a1 8 K a m e n s k o e U f i m s k y 1 8 T a n u n1 9 B a k s t r i ' s k o e B o b r i k o v s k y 1 9 N i k i n o2 0 O l i m p i a d o v s k o e U f i m s k y 2 0 T i c h o v s k a j a2 1 S o r a ' l in s k o e K u n e v s k y 2 1 B a t u r b a aN o v o2 2 K a d i e v s k o e K a z a n s k y 2 2 S a v i n s k a jaM o r d o v o2 3 K o r m a l s k o e U f i m s k y

B o b r i k o vK u n o v s k y 1 9 9 9 - 2 0 0 3T u r n e i s k y 1 7 87 1 7 9 5B o b r i k o v s k y 1 5 6 6 t 5 8 1

K u n - P a s h i 'A r t i n s k y 8 0 0 - 8 9 9B a s h k i r s k y 1 0 2 3 - 1 0 5 1B a s h k i r s k y 1 3 1 4 1 3 3 5Tu rn e i sk y 1 6 6 6 - -1 6 8 2

T u l s k y , B o b r i k o v s k 1 6 88 1 7 1 4O k s k o S e r p y c h o v . 1 3 7 6 1 4 35K u n . - S a r a ' - S e m i l u kF i m e n + T u m e 2 1 6 4 1 8 57

F i m e n + T u m e 1 8 99 2 0 0 3T u l s k y + B o b r o v s k y 2 1 0 0 - 2 1 8 2T u l s k y + B o b r o v s k y ~ 2 0 0

B a s h k i r s k y 1 5 8 4 - 1 5 9 5V s r e i s k y - K a s h i r s k yV i ze O k s k o - S e r p u c h o v . 1 6 26 1 6 76S a k m . 9 1 6 - 9 6 0T u r n m e J a s n o k o l .

T u r n m e - J a s n o k o l . 1 4 67 1 4 72

i n m o s t s a m p l e s is h i g h , > 2 . 7 w t . V a n a d i u m a n dn i c k e l c o n t e n t w e r e m e a s u r e d i n t h e T a t a r ia o i l so n l y ( T a b l e 2 ) . T h e c o n c e n t r a t i o n o f b o t h e l e m e n t si s s u b s t a n t i a l l y g r e a t e r i n t h e a s p h a l t e n e f r a c t i o n( V : 7 70 1 7 4 0 m g / g ; N i : 1 4 0 - 6 7 0 m g / g ) , b u t i t i s s t i llq u i t e h i g h i n t h e a s p h a l t e n e - f r e e o i l a s w e l l ( V 6 4 -5 0 7 m g / g ; N i : 2 3 - 6 6 m g / g ) . I n b o t h a s p h a l t e n e a n da s p h a l t e n e - f r e e o i l fr a c t io n s v a n a d i u m d i s t in c t i v e lyd o m i n a t e s w i t h r e s p e c t t o n i c k e l ( V / N i > 4 ) .F u r t h e r m o r e , V T d o m i n a t e s t h e v a n a d i u m s p e c i e s

( v t V / v > 0 . 5 5 , T a b l e 2 ). A s p h a l t e n e c o n t en t i n t h eT a t a r i a o i l s a m p l e s r a ng e s b et w e e n 5 - 1 1 .

H y d r o c a r b o n s c h a r a c t e r i s t i c s i n t h e C 5 t o C 8r a n g e ( g a s o l i n e f r a c t i o n ) o b t a i n e d f o r o i l s f r o m t h eT a t a r i a a n d P e r m b a s i n s a r e s u m m a r i z e d i nT a b l e 3 ( a ) a n d ( b ) . T h e T a t a r i a o i l s a r e c h a r a c t e r -i z e d b y r e l a t i v e l y l o w iso t o n o r m a l a l k a n e s iCs /n C 5 0 . 2 - 2 . 7 ) a n d l o w m o n o a r o m a t i c s ( 3 M C s / B e n z1 2 - 1 4 9 ) . I n t h e P e r m b a s i n o i l s , t h e s e r a t i o s a r einver ted , i . e . iCs /nC5 1 3 - 5 . 5 ) a n d ( 3 M C s / B e n z 5 -1 7 ) . T h e r e d u c e d n - a l k a n e s i n t h e P e r m b a s i n o i l s

T a b l e 2 . D e t a i l e d a n a l y s i s o f a s p h a l t e n e s , v a n a d i u m a n d n i c k e l in o i l s a m p l e s f r o m t h e T a t a r i a b a s i n . N o t e : ( 1 ) m a r k e d l y g r e a t e r c o n c e n -t r a t io n o f v a n a d i u m t h a n n i c k e l, a n d ( 2 ) d o m i n a n c e o f p o r p h y r i n b o u n d v a n a d y l ( IV v a l e n t V O ) a m o n g t h e v a n a d i u m f o r m sO i l A s p h a l t e n e

S a m p l e a s p h a l t e n e V ( m g / g ) N i ( m g / g ) V / N i V ( I V ) ( m g / g ) V ( I V ) / V ( m g / g ) V ( m g / g ) N i ( m g / g )1 2 .9 207 15 13.8 147 0 .71 1215 1602 5 . 4 3 5 5 3 3 1 0 . 7 5 2 1 7 0 . 61 1 4 4 0 1 6 03 8 .5 242 33 7 .33 176 0 .73 1070 1604 1 1 .5 2 2 5 2 5 9 . 0 0 1 5 6 0 . 6 9 8 0 0 1 4 06 1 0 .9 3 9 0 4 6 8 . 4 8 2 4 6 0 . 6 3 1 2 6 0 1 6 07 1 3 .1 5 0 7 6 6 7 . 6 8 4 1 0 0 , 81 1 7 4 0 2 1 59 5 .6 180 16 11.25 101 0 .56 870 1501 0 8 . 8 3 9 4 4 8 8 . 21 2 7 6 0 . 7 1 4 1 0 1 5 51 1 1 0 . 6 3 9 6 4 4 9 1 8 5 0 . 4 7 1 3 3 0 1 5 01 2 7 . 6 1 7 6 3 0 5 . 8 7 1 2 3 0 . 7 7 5 0 1 4 01 4 3 . 7 2 3 0 4 2 5 . 4 8 1 3 5 0 . 5 9 9 6 0 2 1 01 5 4 . 2 1 9 4 2 5 7 . 7 6 1 2 3 0 . 6 3 1 0 8 5 1 7 01 6 6 . 4 1 9 9 2 3 8 . 6 5 1 1 1 0 . 5 6 9 7 0 1 4 51 7 4 . 8 1 5 2 5 0 3 . 0 4 1 1 6 0 . 7 6 1 5 0 6 4 2 31 8 6 . 5 1 6 2 4 8 3 . 3 7 1 2 0 0 . 7 4 t 4 0 2 4 0 719 1.2 64 30 2 .1 39 0 .61 905 3832 0 5 . 3 1 4 8 4 0 3 . 21 1 3 7 0 . 9 2 1 5 2 2 3 8 82 1 2 . 2 7 9 5 4 1 . 4 6 4 1 0 . 6 6 7 6 8 6 6 82 3 3 . 9 1 2 6 3 0 4 . 2 9 0 0 . 7 1 1 2 5 0 3 0 4


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Tatar ia-Perm Russia) oils geochemical correl ation 705Table 3. Significant ratios derived from hydrocarbons analysis of both light distillates gasoline C5 C7) and CLs+ fractions: a and b rep-resent, respectively, he Tatarian and Perm basins. Parameters PII and PI2 have been calculated according to Thompson 1983) andC21 + alkanes OEP according o Scalan and Smith 1970)

Gasoline fraction Normal and isoprenoid distributionSample iCs/nC5 3MCs/Benz. PI1 PI2 nC7 MCyC6 Pr Ph Pr nCi7 Ph /n Ci s OEP C21 +

Tataria a)l 0.9 100 2.3 29 29 0.42 0.25 0.6 0.982 I. l 114 2.3 30 30 0.4 0.2 0.62 0.993 1.1 149 2 31 31 0.51 0.43 0.81 0.994 2.7 108 1.8 25 25 0.5 0.41 0.81 0.985 0.7 66.5 2 32 32 0.45 0.41 0.86 0.966 0.6 100 2.2 30 30 0.56 0.39 0.77 0.967 0.9 15.4 2.2 27 27 0.41 0.35 0.77 0.968 0.8 12 3.6 23 23 0.51 0.51 0.95 0.999 1 90 1.8 24 1.7 0.5 0.5 0.97 0.9710 t.6 90 2.2 26 1.9 0.54 0.45 0.83 0.9711 1.1 28 1.7 25 2.1 0.48 0.72 0.72 0.9812 0.2 46 1.8 32 2.1 0.5 0.41 0.81 0.98Perm b)1 1.5 5 1 15 0.3 0.6 0.8 0.75 1.12 5.5 6 0.7 15 0.3 1.65 0.6 0.4 1.053 4.1 t0 1 15 0.4 1.4 0.4 0.6 14 3 13 0.5 22 0.5 1.6 0.6 0.4 0.875 2.2 17 0.5 22 0.5 0.9 0.5 0.3 16 3.6 7 2.3 21.5 0.5 1.5 0.3 0.3 0.97 2 3 2.2 30 0.5 1.5 0.6 0.4 18 2.9 10 1 28 0.8 1.6 0.5 0.5 19 - 3 - 16 0.2 0.8 0.3 0.6 1.0210 11 6 0 .5 10 0.2 1 0.6 0.4 111 2 5 0.8 12 0.3 0.8 0.7 0.7 112 3.5 7 0.7 15 0.4 1 0.5 0.9 0.9

are Further substantiated by the suppressed riG7/MCyC6 ratio 0.2-0.8) and Paraffin indexes PI10.5 2.3 and PI2 10-30) compared to the Tatariaoils where the nCy/MCyC6 ratio ranges between 1.7to 32, PI1 between 1.7-3.6, and PI2 23-32Table 3 a) and b), Fig. 3). Paraffi n index 2 in the

Perm basin oils is also somewhat rediaced comparedto the Tatari a oils Table 3 a) and b)).Characteristics of normal and i s o - a l ka n es distri-bution in the Tataria and Perm oils obtained byC15+ gas chrom ato gra phy are s hown in Fig. 4 a)and d) and summ arize d in Table 3 a) and b).Most samples in both basins are characterized bycomplete n-alkanes envelopes, although depletion ofvariable degrees in n-alkanes is observed in 2-3samples in each of the basins cf. Figure 4 a, b).The n-alkane envelope at the C21 + range is charac -terized in the Tataria oil by slight even carbon num-bers OEP 0.96-0.99) and in the Perm oils it isabout unity OEP 0.87-1.1). The pristane to phy-tane isoprenoids ratio in the Tatarian oils is lowPr/Ph 0.4-0.56 - - Fig. 4 a, b), Table 3a). The ratioof Pr to Ph is generally low in the Perrn basin oils

as well, but it has bi-modal distribution, in onegroup phytane dominates Pr/ Ph< 1) and in theother pristane Pr/Ph 1.4-1.65) cf. Fig. 4 c) andd), Table 2 b).

Steranes mass chromatograms m / z 217 and 218)for oils from both basins are characterized by pre-dominance of C29 relative to C28 and C27 /3/3-ster-anes, although with relatively high proportions ofC27 Table 4 a) and b)) and little appea rance of

diasteranes. Ratios of 2 0 S / 2 0 R + 20S andf lf l/ O ~ O ~ q tiff-C29 steranes are relatively consistent forall samples studied from both basins, rangingbetween 0.45-0.6 and 0.4-0.7, respectivelyTable 4 a) and b)). Terpanes mass chroma togram sm / z 191) for both basins, oils are characterized by

relatively high C29 relative to C30 hopa nes in mostsamples C29/C30 hopan es > 1) and very low18~ H)-t ris norh opan e Ts) rel ative to 17c~ H)-tris-norh opa ne Tin) Fig. 5 a-d), Table 4 a) and b)).In most samples, the abundance of C31+ homoho-panes is moderate and their ratio of 2 2 S /22R + 22S ep imeriz ation is a t maxi mum level,

. . . 5~ 4

Z 2. 1 i n f e w o f

T A T A R I A

a

P E R M

c

b P h d

T I M E r a i n )Fig. 4. C15 gas chrom atog raph ic profiles of the hexane fraction: a, b and c, d represent, respectivelyoil samples from the T atarian a nd Perm basins. Note: 1) depletion of n-alkanes in b relative to a , and2) inversion of Pr/Ph ratio between c and d.


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Tatar ia -Perm (Russ ia) oi ls geochemical correlat ion 707Table 4. Relative distributions of 'bioma rkers" characteristics of both Tataria (a) and Pe rm (b) oil samples. Data were obtained by SIR(single ion recording) m / z 217. 1956 and 218. 2030 mass spec tra for steranes an d 191. 1800 for trit erpane s (resolution < 2500)

Steranes Terp anes 22S/22S = RSample 27:28:29(%) 2 0 S / 2 0 S R ~ / 0 ~ 4 t if f T / S C29 C30 T s / T s Tm TTC23/Hop. C3t +

T a t a r l a a )1 31 0.5 0.6 8.1 1.3 0.3 0 . 1 0.52 40 0.54 0.6 3.4 1.1 0.16 0.58 0.63 40 0.55 0.6 3.3 1.03 0.16 0.58 0.54 40 0.5 0.6 4.4 1.2 0.1 0.3 0.65 38 0.6 0.7 1.4 1.1 0.2 1.6 0.66 37 0.6 0.7 3.8 1.2 0.2 1.5 0.67 42 0.6 0.7 4.5 1.3 0.2 0.85 0.68 36 0.54 0.7 1.2 1.1 0.i 0.1 0.69 34 0.54 0.6 4.7 1.3 0.1 0.2 0.610 41 0.53 0.6 3 1.05 0.15 0.35 0.711 37 0.54 0.7 4.1 1.1 0.14 1.04 0.612 41 0.57 0.44 4.5 1.1 0.16 2.8 0.613 46 0.56 0.65 5.8 1.05 0.16 0.15 0.614 42 0.55 0.6 6.8 1.3 0.25 0.25 0.615 35 0.5 0.6 13.5 1.4 0.16 0.6 0.616 34 0.45 0.65 13.4 1.4 0.16 0.34 0.5717 40 0.5 0.67 8.7 1 0.1 0.4 0.5718 45 0.52 0.7 7.8 1.6 0.26 1.6 0.4519 38 0.5 0.7 6.8 0.8 0.17 0.1 0.620 40 0.43 0.66 16 1.5 0.12 0.4 0.621 39 0.5 0.6 10 4.4 0.2 1.07 0.6

erm b )1 38 0.52 0.6 5.2 5.2 0.2 0.5 0.532 30 0.47 0.6 6.2 6.2 0.15 0.2 0.63 37 0.53 0.6 3.9 1 0.4 0.2 0.54 37 0.5 0.62 5.7 1.5 0.1 0.5 0.55 42 0.53 0.62 3.2 1.4 0.24 1.2 0.66 32 0.5 0.6 8 0.62 0.1 0.14 0.577 36 0.53 0.6 7.2 1.1 0.2 0.7 0.68 32 0.53 0.6 2.1 0.9 0.25 0.5 0.559 33 0.6 0.6 1.7 0.8 0.26 0.5 6210 33 0.57 0.56 3 3 0.3 0.6 0.611 37 0.55 0.4 1.6 n.i.c, n.i.c, n.i.c, n.i.c.12 39 0.5 0.6 4.2 0.93 0.14 0.57 0.613 38 0.53 0.6 2.l 0.9 0.2 3 n.i.c.14 34 0.52 0.5 0.9 0.9 0.2 2.1 n.i.c.15 31 0.52 0.65 n.i.c. 0.7 n.i.c. 1.1 n.i.c.17 32 0.54 0.6 n.i.c. 0.7 n.i.c. 2.1 n.i.c.18 42 0.48 0.6 8.2 1.1 0.2 0.9 0.620 30 0.55 0.7 3.8 0.8 0.1 0.55 0.621 40 0.5 0.7 5.2 1.1 0.15 0.96 0.5722 42 0.45 0.62 4.6 0.7 0.1 0.6 6n.i.c.-not identified cle arly.

t h e s a m p l e s p o s s i b l y in d i c a t e s m o d e r a t e b i o d e g r a d a -t i o n . H o w e v e r , t h e P I 1 t o P I 2 r a t i o o b t a i n e d f o r a l lT a t a r i a o i l s a m p l e s ( T a b l e 3 ( a )) a p p e a r s t o p r e c l u d em a j o r b i o d e g r a d a t i o n e ff e ct s. T h e C l s + g a s c h ro -m a t o g r a m s o b t a i n e d f o r s a m p l e s 1 9 , 2 0 a n d 2 1( T a b l e l ( a ) ) s h o w s o m e d i f f e r e n c e s i n n - a l k a n e d i s -t r i b u t i o n c o m p a r e d t o t h e o t h e r T a t a r i a o i l s ( c f .F i g . 4 ( a ) a n d ( b ) . H o w e v e r , t h e f a c t t h a t t h e d i f f e r -e n c e s o b s e r v e d i n t h e s e s a m p l e s a r e r e s t r i c t e d t o t h ef r a c t i o n w h i c h i s m o r e r e a d i l y s u s c e p ti b l e to d e g r a -d a t i o n w h e r e a s t h e r e l a t i v e l y s t a b l e b i o m a r k e r ss p e c t r a s h o w g o o d c o r r e l a t i o n t o a l l o t h e r s a m p l e s( T a b l e 4 ( a ) ) i n d i c a t e s t h a t t h e d i f f e r e n c e s o b s e r v e dd o n o t s t e m f r o m d i f f er e n t ia l o r i g i n b u t r a t h e rr e fl e c t s e c o n d a r y m o d i f i c a t i o n .

T a t a r i a o i l s a m p l e s a r e a l l r i c h i n v a n a d i u m a n dn i c k e l w i t h a d i s t in c t i v e v a n a d i u m d o m i n a n c e ( V /N i > 4 ) ( T a b le 2 ). T h e v J V / v > 5 0 ( T a b le 2 )s u g g e st s t h a t m a j o r i t y o f t h e v a n a d i u m i n t h e o i l s i sc o m p l e x e d a s m e t a l l o - p o r p h y r i n s . T h i s , a l o n g w i t h

t h e r e l a ti v e ly h ig h a b u n d a n c e o f S ( > 3 f o r m o s ts a m p l e s s t u d i e d ) a n d t h e l o w P r / P h r a t i o ( < 0 . 6 , s e eF i g . 4 ( a ) a n d ( b ) a n d T a b l e 3 ( a ) s u g g e s t t h a t t h eT a t a r i a o i l s s t u d i e d o r i g i n a t e d f r o m a s o u r c e r o c kd e p o s i t e d i n a n e n v i r o n m e n t w i t h a r e l a t i v e l y s t r o n gr e d u c i n g r e d o x p o t e n t i a l a n d p r o b a b l y s o m e w h a th y p e r s a l in e r e s tr ic te d m a r i n e c o n d i t i o n s ( D i d y k e ta l . 1 9 7 8 ; L e wa n, 1 9 8 4 ; Hug he s , 1 9 8 4 ; Pa l a c a s ,1 9 8 4 ; M o l d o w a n e t a l . 1985; Lipiner e t a l . 1988;A i z e n s h t a t a n d S u n d a r a m a n , 1 9 8 9 ) . P r e v a l e n c e o fn - a l k a n e m o l e c u l e s w i t h e v e n c a r b o n n u m b e r s a tt h e C 21 + r a n g e ( O E P < 1 ) h a s b e e n o f t e n f o u n d i na s s o c i a t i o n w i t h r e d u c i n g , m a i n l y c a r b o n a t e d e p o s i -t i o n a l e n v i r o n m e n t ( S c a l a n a n d S m i t h , 1 9 7 0 ; T i s s o te t a l . 1 9 7 7 ; Pa l a c a s , 1 9 8 4 ) . Ho we v e r , the se a utho r ss u g g e s t t h a t t h e O E P r a t i o i s t h e r m a l l y u n s t a b l ea n d i s m o d i f i e d t o w a r d s u n i t y a s t h e r m a l m a t u r i t ya p p r o a c h e s t h e m a i n p h a s e o f o i l g e n e r a t i o n . T h ec l o s e t o u n i t y O E P r a t i o s o b t a i n e d f o r t h e T a t a r i ao i l s (0 .9 6 -0 .9 9 ) a r e c o ns i s te nt wi th the r e la t i v e l y


8/12


9/12

Tataria-Perm (Russia) oils geochemical correlation 709T h e T a t a r i a o i ls s t u d i e d a r e r e l a t i v e ly h e a v y w i t h

s o m e v a r i a b l e v i sc o s i t ie s . T h e r e a p p e a r s t o b e n os y s t e m a t i c v a r i a t i o n o f o i l d e n s i t y w i t h r e s p e c t t oe i t h e r r e s e r v o i r d e p t h , a g e o r l i t h o l o g y . T h u s t h er e l a t i v e l y h i g h d e n s i t y o f t h e o i l a p p e a r s t o b e ag e n e t i c c h a r a c t e r i s t i c s t e m m i n g f r o m t h e n a t u r e o fi t s s o u r c e r o c k a n d d e p o s i t i o n a l e n v i r o n m e n t . T h ep o s s i b i l i t y t h a t t h e r e l a t i v e l y h i g h o i l d e n s i t y i s re -l a t e d t o t h e n a t u r e o f t h e s o u rc e r o c k a n d d e p o s i -t i o n a l e n v i r o n m e n t i s c o n s i s t e n t w i th t h e a b u n d a n c eo f a s p h a l te n e s , s u l fu r a n d v a n a d i u m i n t h e o i l(Bask in and Pe te rs , 1992) .Oils f ro m the Perm basin

M o l e c u l a r c h a r a c t e r is t i c s s p e ct r a o b t a i n e d f o r t h eo i l s a m p l e s f r o m t h e P e r m b a s i n s h o w g e n e r a l l yg o o d c o r r e l a t i o n w i t h m o d e r a t e d i v e r s i t y i n s o m e o ft h e p a r a m e t e r s ( F i g s 4 ( c ) a n d ( d ) a n d 5 ( c ) a n d ( d ) ,T a b l e s 3 ( b ) a n d 4 ( b) ) . C o n t r a r y t o t h e T a t a r i a b a s i no i l s , g a s o l i n e f r a c t i o n i n t h e s a m p l e s f r o m P e r mb a s i n s h o w n o m a j o r d e p l e t i o n i n t h e s o lu b l e m o n o -a r o m a t i c m o l e c u l e s w h e r e a s t h e i r n - a l k a n e s a p p e a rt o b e a t t e n u a t e d . T h e m i t i g a t i o n o f l i g h t -e n d n -a l k a n e s i s d e m o n s t r a t e d , f o r e x a m p l e , b y t h e r e l a -t i v e l y h i g h r a t i o o f iso- a n d cyclo- t o n o r m a l -a l k a n e s ( r e s p e c t i v e l y , iCs/nC5 a n d n C T / M C y C 6 ) a n dl o w P I 1 i n d e x ( T a b l e 3 ( b ) , F i g . 3 ) a n d p r o b a b l yr e fl e ct s b i o d e g r a d a t i o n . T h u s , i t a p p e a r s f r o m d a t ai n T a b l e 3 ( b ) t h a t t h e m a j o r i t y o f t h e o i l s a m p l e ss t u d i e d f r o m t h e P e r m b a s i n w e r e e x p o s e d t o s o m ed e g r e e o f b i o d e g r a d a t i o n . H o w e v e r , e x c e p t f o r t h r e es a m p l e s , n o d i s t i n c t i v e e f f ec t o f d e g r a d a t i o n i s in d i -c a t e d i n t h e i r C 1 5 + g a s c h r o m a t o g r a m s ( c f . F i g .4 ( c ) a n d ( d ) . H e n c e , d e s p i t e th e c o n s i d e r a b l y g r e a t e rp r o p o r t i o n o f s a m p l e s a f f e c t e d a n d r e g i o n a l d i s t r i -b u t i o n o f t h e d e g r a d a t i o n c o m p a r e d t o t h e T a t a r i ao i l s , t h e e f f e c t o b s e r v e d i s r e s t r i c t e d m a i n l y t o d e -p l e t i o n o f l i g h t - e n d n o r m a l a l k a n e s w i t h n o s i g n i f i -c a n t i m p r i n t i n t h e h i g h e r m o l e c u l a r - w e i g h t ra n g e ,s u g g e s t i n g t h a t t h e d e g r a d a t i o n r e c o r d e d w a s r e l a -t i v el y m o d e r a t e .

P l o t s o f P I r a t i o s o b t a i n e d f o r t h e P e r m b a s i no i l s a r e s c a t t e r e d ( F i g . 4 ). T h e s e d i s c r e p a n c i e s h o w -e v e r , r e f le c t t h e e f f e ct o f b i o d e g r a d a t i o n a n d t h e r e -f o r e d o n o t i n d i c a t e t h e r m a l m a t u r i t y o f t h e o i l s .O n t h e o t h e r h a n d , 2 2 S / 2 2 R C 3 1 + h o m o h o p a n e sa n d 2 0 S / 2 0 R and /~ /? /ee + /~ / C29 s te ra ne ra t i os( T a b l e 4 ( b ) ) i n d i c a t e a s i m i l a r m a t u r i t y l e v e l f o r a l ls a m p l e s s t u d i ed , w i t h i n a n a d v a n c e d s t a g e o f t h e o i lg e n e r a t i o n r a n g e ( M a c k e n z i e a n d M a x w e l l , 1 9 8 1 ;C u r i a l e et al. 1 9 8 9 ; P e t e r s a n d M o l d o w a n , 1 9 9 3 ) .

T h e r e l a t iv e l y g o o d c o r r e l a t i o n o f a c y c li c a n dp o l y c y c l ic a l k a n e c h a r a c t e r i s ti c s o b t a i n e d f o r t h e o i ls a m p l e s f r o m t h e P e r m b a s i n s u g g e s t s t h e i r c l a s s i f i -c a t i o n i n t o o n e g e n e t i c f a m i l y . T h e m o s t p r o -n o u n c e d i n t e r r u p t i o n i n t h e v a r i o u s m o l e c u l a rc o r r e l a t i o n s b e t w e e n t h e s e s a m p l e s i s i n t h e P r / P hr a t i o s . P r / P h r a t i o s o b t a i n e d f o r a l l s a m p l e s a r eg e n e r a l ly l o w , b u t s h o w a n a p p a r e n t b i - m o d a l d i s -

t r i b u t i o n ; i n o n e g r o u p P h i s > P r ( P r / P h 0 . 6 1 ,F i g . 4 ( d ) ) w h e r e a s i n s o m e s a m p l e s P r d o m i n a t e( P r / P h 1 . 4 - 1 . 6 5 , F i g . 4 (c ) ). T h e r a t i o o f P r t o P h i no i l s h a s b e e n a s s u m e d t o i n d i c a t e m a i n l y t h e r e d o xp o t e n t i a l o f t h e d e p o s i t i o n a l e n v i r o n m e n t f o r t h es o u r c e r o c k , a s s u m i n g t h e y a r e p r i m a r i l y d e ri v e df r o m p h y t y l s i d e c h a i n s o f c h l o r o p h y l l ( D i d y k e tal. 1 9 78 ). I n c o n t r a s t , i t h a d b e e n s h o w n t h a t t h eP r / P h r a t i o c a n b e a f f e c t e d a s w e l l b y e i t h e r o r i g i nf r o m o t h e r o r g a n i s m s o r b y t h e r m a l m a t u r i t y ( e . g .C h a p p e et al. 1 9 8 2 ; G o o s e n s et al. 1984; tenH a v e n et al. 1 9 8 7 ) . H o w e v e r , i n t h e s t u d y c a s e ,s i m i l a r i ty o f b i o m a r k e r s d i s t r i b u t i o n a n d t h e r m a lm a t u r i t y i n d i c a t o r s b e t w e e n s a m p l e s w i t h P r /P h > 1 .4 a n d s a m p l es w i t h P r / P h < 1 e n c u m b e ra t t r i b u t i o n o f t h e s e d i f f e r e n c e s t o e i t h e r o r i g i n f r o md i f fe r e n t o r g a n i s m s a n d o r d i f f e r e n t ia l m a t u r i t y .H e n c e , w e i n f e r t h a t t h e d i f f e r e n c e s r e c o r d e d i n P r /P h r a t i o s i n s o m e P e r m b a s i n o i l s m a i n l y r e f l e c ts o m e s p a t i a l v a r i a t i o n s i n t h e r e d o x p o t e n t i a l o f t h es o u r c e r o c k d e p o s i t i o n a l e n v i r o n m e n t d u r i n g e a r l yd i a g e n e s i s a n d d o n o t i n d i c a t e m a j o r d i f f e r e n c e s i ns o u r c e b i o t a .Correlat ion of oi ls fro m the Tataria an d Perm basins

C o r r e l a t i o n b e t w e e n t h e T a t a r i a a n d P e r m b a s i n so i ls i s s o m e w h a t e q u i v o c a l. M a j o r c h a r a c t e r is t i c s o fb o t h s t e r a n e s a n d t e r p a n e s b i o m a r k e r m a s s c h r o m a -t o g r a m s s h o w i n g e n e r a l g o o d c o r r e l a t i o n . B o t h o i lsa r e c h a r a c t e r i z e d b y l o w d i a s t e r a n e s , s i m i l a r r a t i o sof C 7:C 8:C 9 /~ /~-s te ranes wi th modera te ly h ighC 2 7 s t e r a n e , h i g h t o d o m i n a n c e o f C 9 r e l a t i v e t oC 3 0 - h o p a n e s a n d v e r y l o w T s / T m r a t i o s ( c f . F i g u r e5 ( a - d ) , T a b l e 4 ( a ) a n d ( b ) ) a n d t h e y a p p e a r t o h a v eb e e n d e r i v e d f r o m a s i m i l a r s o u r c e r o c k . M o r e o v e r ,2 2 S / 2 2 R C 3 1 + h o m o h o p a n e s a n d 2 0 S / 2 0 R and /~///e e + / ?/ ~- C2 9 s t e r a n e s r a t i o s i n d i c a t e s i m i l a r t h e r m a lm a t u r i t y f o r t h e o i l s f ro m b o t h b a s i n s ( cf . T a b l e 4 ( a )and (b ) ) .

T h e r e a r e s o m e d i f f e r e n c e s , h o w e v e r , b e t w e e n t h eT a t a r i a a n d P e r m o i ls , m a i n l y i n t h e i r P r / P h a n dO E P r a t i o s ( c f . T a b l e 3 ( a ) a n d ( b ) ) . M e a n O E P f o rt h e P e r m o i l s i s u n i t y , i n a c c o r d a n c e w i t h t h e l e v e lo f th e r m a l m a t u r i t y , a n d a n a p p a r e n t d i s c r e p a n c yi n t h e o r d e r o f 0 . 02 r e l a t i v e t o m e a n O E P i n t h eT a t a r i a o i l s m a y b e i n s i g n i fi c a n t a n d i s p r o b a b l yw i t h i n t h e e r r o r r a n g e f o r t h e m e a s u r e m e n t s . P r t oP h r a t i o i n t h e P e r m o i ls h a s a b i - m o d a l d i s t r i -b u t i o n a n d i s g e n e r a l l y h i g h e r t h a n f o r t h e T a t a r i ao i l s ( c f . T a b l e 3 ( a ) a n d ( b ) ) . H o w e v e r , s i n c e m o s tb i o m a r k e r s s h o w g o o d c o r r e l a t i o n b e t w e e n t h e t w ob a s i n s ' o i l s w e i n f e r t h a t t h e d i f f e r e n c e s d o n o tr e f l e c t v a r i a t i o n i n o r g a n i c s o u r c e b u t r a t h e r r e f l e c ts p a t i a l d e c l i n e i n r e d o x / r e d u c t i v e p o t e n t i a l o f t h ed e p o s i t i o n a l e n v i r o n m e n t i n P e r m d u r i n g e a r l y d i a -genes is .

A l b e i t t h e r e l a t i v e l y g o o d c o r r e l a t i o n o f m o s tc h a r a c t e r i s ti c s o f t e rp a n e s m a s s c h r o m a t o g r a m s o fs a m p l e s s t u d i e d f r o m b o t h t h e P e r m a n d T a t a r i a


10/12

710 Z. Aizenshtatb a s i n s , t h e r e i s a d i s t i n c t i v e d i s c r e p a n c y i n t h e i r t r i -c y c l i c t e r p a n e s c o n t e n t . T h i s d i s c r e p a n c y i s c h a r a c -t e r i s t i c f o r b o t h b a s i n s a n d i s m a i n l y p o r t r a y e d b yt h e p r o m i n e n t C 23 t r i c y c l i c t e r p a n e s i n a b o u t h a l ft h e s a m p l e s ( c f . F i g . 5 ( a - d ) , T a b l e 4 ( a ) a n d ( b ) ) .A q u i n o N e t o e t a l . (1983 , 1989) and Vo lkm an e t a l .( 9 8 3 ) s u g g e s t t h a t a b u n d a n c e o f t r i c y cl i c t e r p a n e sp o s s i b l y r e p r e se n t s p r e s e n c e o f T a s m a n i t e s a l g a e i nt h e s o u r c e r o c k . S i m i l a r r e l a t i o n s b et w e e n a b u n -d a n c e o f t r i c y c li c t e r p a n e s a n d T a s m a n i t e s a l g a ew e r e o b s e r v e d e l s e w h e r e , e . g . i n m i d l a t e D e v o n i a nb i t u m i n o u s r o c k s f r o m t h e N o r t h w e s t T e r r i t o r i e s ,C a n a d a ( F e i n s t e i n e t a l . , 1991) . Thus , the d i f fe rencei n t r i c y c l ic t e r p a n e s m i g h t i n d i c a t e s o m e d i f f e r e n c e si n t h e o r g a n i c i n p u t t o t h e s o u r c e r o c k o f t h e o i L sa n d p o s s i b l y c a n b e u s e d f o r a s e c o n d a r y s u b d i v i -s i o n b e t w e e n t h e o i l s s t u d i e d . H o w e v e r , w e o b s e r v en o c o r r e l a t i o n b e t w e e n t r i c y c l i c t e r p a n e s d i s t r i -b u t i o n a n d P r / P h r a t i o n o r w i t h t h e v a r i a t i o n i nr e s e r v o i r a g e , l i t h o l o g y o r s p a t i a l d i s t r i b u t i o n .F u r t h e r m o r e , t e r p a n e s in o i l a r e o f t e n a s s u m e d t oo r i g i n a t e fr o m b a c t e r i a l m e m b r a n e s ( O u r i s s o n e ta l . , 1 9 82 ), w h e r e a s h i g h p r o p o r t i o n s o f s t e r a n e s a r et h o u g h t t o i n d i c a t e c o n t r i b u t i o n o f m a r i n e p l a n k -t o n i c o r b e n t h i c a l g a e ( c . f . P e t e r s a n d M o l d o w a n ,1 9 9 3 ) . I n t h i s r e g a r d , i t i s p e r t i n e n t t o n o t e t h a tt h e r e a p p e a r s t o b e n o c o r r e l a t i o n b e t w e e n a b u n -d a n c e o f tr i c y c l i c t e r p a n e s a n d t h e v a r i a t i o n i n t o t a lt e r p a n e s t o s t e r a n e s r a t i o i n t h e o i l s a m p l e s .

I n l i g h t o f t h e a f o r e m e n t i o n e d , w e a s s u m e t h a td e s p i t e t h e i m m e n s e r e g i o n a n d d i v e r s i t y o f r e s e r -v o i r r o c k s c o v e r e d b y t h e s a m p l e s s t u d i e d t h e o i l sf r o m b o t h t h e T a t a r i a a n d P e r m b a s i n s c o u l d h a v eb e e n d e r i v e d fr o m a m u t u a l s o u r c e r o ck . W e i n f ert h a t t h e d i f f e r e n c e s r e c o r d e d i n t r i c y c l ic t e r p a n e s i nb o t h b a s i n s a n d P r / P h r a t i o s i n s o m e P e r m o i l s ,p o s s i b l y r e f l e c t s o m e s p a t i a l v a r i a t i o n s i n o r g a n i ci n p u t a n d / o r i n r e d o x p o t e n t i a l o f t h e d e p o s i t i o n a le n v i r o n m e n t . C o n s i d e r i n g t h e d i m e n s i o n s o f t h es t u d y r e g i o n a n d t h e d i v e r s i t y o f t h e r e s e r v o i r r o c k sf r o m w h i c h s a m p l e s w e r e o b t a i n e d s u c h v a r i a t i o n sa r e a n t i c i p a t e d a n d i n f a c t t h e y a r e s u r p r i s i n g l y l i t-t le . M o r e o v e r , o u r c o l l e a g u e s w h o s t u d i e d t h eT a t a r i a v a s t p r o d u c t i o n o f p e t r o l e u m r e p o r t f o r t h eb a s i c p a r a m e t e r s v e r y g o o d r e s e m b l a n c e t o t h o s eg i v e n i n t h e p r e s e n t s t u d y ( Y a k u b s o n , 1 99 7 , p e r s .c o m m . ) .P o t e n t i a l s o u r c e r o c k

T h e o c c u r r e n c e o f t r e m e n d o u s q u a n t i t i e s o f r e l a -t i v e ly h o m o g e n o u s p e t r o l e u m d i s t r i b u t e d o v e r a ne n o r m o u s t e r r a i n d e m a n d s a n a p p r o p r i a t e s o u r c er o c k . T h i s r e q u i r e m e n t h a s u n i q u e g e o l o g i c a l i m p l i -c a t i o n s . I t r e q u i re s a d e p o s i t i o n a l e n v i r o n m e n t w i t ha r e l a t i v e l y s t r o n g r e d u c i n g p o t e n t i a l w h i c h s h o u l dh a v e p r e v a i l e d o v e r a h u g e t e r r i t o r y a n d d e s p i t e t hec o l o s s a l t e r r a i n a n d c o m p l e x g e o l o g y i n v o l v e d , t h es o u r c e r o c k s h o u l d h a v e b e e n s u b j e c t e d t o a s i m i l a rt h e r m a l h i s t o r y .

P r e v i o u s s t u d i e s s u g g e s t e d t h a t t h e D e v o n i a nD o m a n i k m a r l y s h a l e ( F i g . 2 ) i s t h e m a j o r s o u r c ef o r t h e o i l i n t h e V o l g o - U r a l b a s i n s . O n l y a s i n g l eo r g a n i c r ic h s a m p l e o f D o m a n i k m a r l w a s a v a i l a b l et o u s i n t h i s s t u d y . T h e g e o c h e m i c a l c h a r a c t e r i s t i c so b t a i n e d f o r t h e s o l v e n t e x t r a c t o f t h i s s a m p l e a r eg e n e r a l l y s i m i l a r t o t h o s e o f t h e o i l s w i t h t h e r e l a -t i v e l y l o w t r i c y c l i c t e r p a n e s . T h e s i m i l a r i t y o f t h eg e o c h e m i c a l c h a r a c t e r is t i c s f u r t h e r c o r r o b o r a t e s t h ep o s s i b i l i t y s u g g e s t e d b y M a y m i n ( 1 9 63 ) t h a t t h eD o m a n i k F o r m a t i o n c a n b e t h e m a j o r s o u r c e r o c kf o r t h e o i l i n b o t h t h e P e r m a n d T a t a r i a p r o l i fi cb a s i n s . H o w e v e r , t h i s i s a p r e l i m i n a r y g l a n c e o n l ya n d a r e l i a b l e a s s e s s m e n t o f t h e a c t u a l s o u r c e r o c kr e q u i r e s a s y s t e m a t i c s t u d y .

CONCLUSIONSD e t a i l e d g e o c h e m i c a l c h a r a c t e r i z a t i o n o f 4 5 o i l

s a m p l e s f r o m 3 0 o il f i e ld s a c r o s s t h e T a t a r i a n a n dP e r m p r o l i f i c o i l b a s i n s r e v e a l s : N o t w i t h s t a n d i n g t h e v a s t r e g i o n a n d d i v e r s it y o f

r e s e r v o i r r o c k s a n d g e o l o g i c a l s e t t in g r e p r e s e n t e d ,a l l th e o i l s a m p l e s s t u d i e d f r o m b o t h b a s i n s h a v eb e e n d e r i v e d f r o m a s i m i l a r , p r e s u m a b l y m u t u a l ,s o u r c e r o c k .

O r g a n i c ( e . g. b i o m a r k e r s d i s t r i b u t io n ) a n d i n o r -g a n i c ( e . g . N i / V r a t i o , s u l f u r c o n t e n t ) c h a r a c t e r -i s t i c s o f t h e o i l s s u g g e s t t h a t t h e y w e r e d e r i v e df r o m a c a r b o n a t e - r i c h a n d c l a y -d e f i ci e n t s o u r c er o c k w h i c h h a d b e e n d e p o s i t e d i n a r e d u c i n g a n dl i k e ly h y p e r s a l i n e e n v i r o n m e n t .

A l l o i ls s t u d i e d h a v e a s i m i l a r l e ve l o f t h e r m a lm a t u r i t i e s , c o n s i s t e n t w i t h a n a d v a n c e l e v e l o f t h em a i n l i q u i d g e n e r a t io n p h a s e .

M o s t s a m p l e s e x p e r i e n c e d s o m e w a t e r w a s h i n ga n d / o r b i o d e g r a d a t i o n . N e v e r t h e l e s s , d e g r a d a t i o nw a s m o d e r a t e a n d i t s e f f e c t i s r e f l e c t e d m a i n l y i nt h e l e a s t r e s i s t i v e f r a c t i o n .

V a r i a t i o n s i n P r / P h r a t i o s i n s o m e P e r m b a s i no i l s , p o s s i b l y r e f l e c t s o m e s p a t i a l v a r i a t i o n s i nr e d o x p o t e n t i a l o f t h e d e p o s i t i o n a l e n v i r o n m e n t .O n t h e o t h e r h a n d , v a r i a t i o n s i n t r i c y c li c t e r p a n e sc o n t e n t i n o i l s f r o m b o t h b a s i n s p o s s i b l y r e f l e c ts o m e z o n e s o f s o m e v a r i a t i o n s i n o r g a n i c i n p u ta n d e n r i c h m e n t i n s p e c i f i c T a s m a n i t e s ) a l g a e .

P r e l i m i n a r y e x a m i n a t i o n o f a n e x t r a c t o fD e v o m a n D o m a n i k F o r m a t i o n s am p l e c o r r o b o -r a t e s t h e p o s s i b i l i t y t h a t t h i s f o r m a t i o n i s a m a j o rs o u r c e r o c k f o r t h e o i l s i n b o t h t h e T a t a r i a a n dP e r m b a s i n s.

A c k n o w l e d g e m e n t s - - W e are indebted to Dr Benat Kh.Musl imov , Depu ty General D irec to r o f TA TN EFF fo r theoil samples studied and to Professor Antoly N.Dmitrievsky, Director of the Oil and Gas ResearchInstitute, A cade my of Science, Russia for his help.


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T a ta r i a - Pe r m R u ss i a ) o i l s g e o c h e m ic a l c o r r e l a t i o n 7 11L ik e wi se we a r e g r a t e f u l t o Dr U . G la sm a c h e r f o r h e lp f u lsu g g e s t i o n s a n d m a te r i a l s a n d D . Asc h e n g r a u f o r t e c h n i c a lsu p p o r t . T h i s s t u d y wa s su p p o r t e d b y a g r a n t f r o m th eBelfer Center fo r Energy Research , I srae l . Valuab le sug-g e s t i o n s b y D r I r . G . W . M . L i j m b a c h a n d a n a n o n y m o u sr e f e re e g r e a t l y im p r o v e d t h e m a n u sc r ip t .

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7 1 2 Z . A iz e n sh t a tp p . 1 1 7 - 1 5 4 . E m p r e ssa Na t io n a l Ad a r e d e I n v e s t i g a t i o nM i n e r s , M a d r i d .Vo lk m a n , J . K . , A le x a n d e r , R . , Ka g i , R . I . a n dR u l lk 6 t t e r , J . 1 9 83 ) G C - M S c h a r a c t e r i z a t i o n o f C 27a n d C 2 8 t r i t e r p a n e s i n se d im e n t s a n d p e t r o l e u m .Geochim. Cosmochim. Acta 47 , 1033-1040 .

Z u m b e r g e , J . E . 1 9 84 ) So u r c e r o c k s o f t h e L a L u n aUp p e r C r e t a c e o u s ) i n t h e Mid d le Ma g d a l e n a Va l l e y ,C o l o m b i a . I n Geochemistry and Source Rock Potentialof Carbonate Rocks ed . J . G. Palacas. AmericanAssociation of Petroleum Geologists Studies in Geology18 , 127-133 .

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