Geochemistry of Oil Shales in Eastern Kentucky

9

G e o c h e m i s t r y o f Oil S h a l e s i n E a s t e r n K e n t u c k y T. L. ROBL, A. E. BLAND, D. W. KOPPENAAL, and L. S. BARRON

Downloaded by TUFTS UNIV on June 12, 2018 | https://pubs.acs.org Publication Date: August 1, 1983 | doi: 10.1021/bk-1983-0230.ch009

University of Kentucky, Institute for Mining and Minerals Research, Lexington, ΚY 40512

Recent resource assessment studies of eastern Kentucky oil shales have established that this resource is a potentially eco nomic synthetic fuel feedstock (1). Extensive geochemical char acterization of this resource has been carried out by the Insti tute for Mining and Minerals Research (University of Kentucky) with support from the Commonwealth of Kentucky Energy Cabinet, the U. S. Department of Energy, and private industry. This ef fort will eventually culminate in the characterization of the entire oil shale resource within the Commonwealth; this particu lar study addresses the results gained from the first two d r i l ling and sampling phases of the overall effort. The sampling and analysis program was initiated in Lewis and Fleming Counties, Kentucky, resulting in 10 cores being drilled with those core samples being designated as the "K-series" samples in this report. The second phase of the program produced an 11 additional cores in Rowan, Bath, Montgomery, Powell, and Estill Counties; these samples are given the "D-series" designation. The location of these core sites as well as current drilling sites are depicted in Figure 1. This paper summarizes the geochemistry of the De vonian and Mississippian age oil shales of the K- and D-series study areas. General Geology and Stratigraphy In Kentucky, black oil shales rich in organic matter (OM) in the Devonian and Mississippian systems crop out in a roughly semi-circular pattern on the flanks of the Lexington Dome. The dome is a structural high on the northern end of the Cincinnati Arch, which stretches between Nashville, Tennessee, and southern Ohio. The black-shale outcrops occur in the Knobs and low hills which border the Bluegrass region from Bullitt County on the west to Lewis and Fleming Counties on the east as shown in Figure 1. From the southern end of the semi-circle south into Tennessee, 0097-6156/83/0230-0159$06.50/0 © 1983 American Chemical Society

Miknis and McKay; Geochemistry and Chemistry of Oil Shales ACS Symposium Series; American Chemical Society: Washington, DC, 1983.


Figure 1. Oil shale resource exploration core sites in Kentucky. Devonian and Mississippian oil shales outcrop in the counties indicated. Drill cores designated as Κ and D series are the subject of this report. Key to drill cores: ο, Λ series; *, Τ series; •, L series; A, D series; and ·, Κ series.


00

> r m

SC

00

r

ο

τι

? Ο

οο Η

g

η χ m

α

>

Η

GO

g

m Ο ο χ m

ο

8

9.

ROBL ET AL.

Oil Shales in Eastern Kentucky

the b l a c k s h a l e c r o p s is r e l a t i v e l y shallow between the L e x i n g t o n

161

o u t i n r i v e r v a l l e y s where t h e o v e r b u r d e n i n t h e C u m b e r l a n d s a d d l e , a s t r u c t u r a l low and N a s h v i l l e domes on t h e C i n c i n n a t i a r c h .


West o f t h e C i n c i n n a t i a r c h , t h e b l a c k s h a l e d i p s i n t o t h e s u b s u r f a c e o f t h e E a s t e r n I n t e r i o r B a s i n where i t becomes o v e r 450 f e e t t h i c k i n H a r d i n C o u n t y , I l l i n o i s , and U n i o n C o u n t y , K e n t u c k y (2). On t h e e a s t e r n f l a n k o f t h e C i n c i n n a t i a r c h , t h e b l a c k s h a l e d i p s e a s t w a r d i n t o t h e A p p a l a c h i a n B a s i n where i t b e comes o v e r 1700 f e e t t h i c k . To t h e s o u t h , t h e o v e r a l l s e c t i o n t h i n s t o 30 o r 40 f e e t a l o n g t h e c r e s t o f t h e a r c h . In each of the t h r e e areas d e s c r i b e d above, the b l a c k - s h a l e sequence d i f f e r s i n o v e r a l l a s p e c t from each of the o t h e r a r e a s when v i e w e d i n o u t c r o p s . T h i s d i f f e r e n c e has l e d t o t h r e e s e t s of s t r a t i g r a p h i e n o m e n c l a t u r e h a v i n g b e e n a p p l i e d t o t h e b l a c k Devonian-Mississippian shales. The g e n e r a l d i s t r i b u t i o n o f t h e u s a g e s o f s t r a t i g r a p h i e n o m e n c l a t u r e a r e shown i n F i g u r e 2. I n e a s t e r n K e n t u c k y t h e O h i o S h a l e t e r m i n o l o g y has b e e n u s e d where t h e M i s s i s s i p p i a n S u n b u r y S h a l e and t h e u n d e r l y i n g B e d f o r d S h a l e c a n s t i l l be r e c o g n i z e d . A typical stratigraphie section w i t h c a r b o n d i s t r i b u t i o n i s shown i n F i g u r e 3. T y p i c a l l y the o v e r b u r d e n i s a m i x t u r e o f c l a y s t o n e and s i l t s t o n e i n t h e B o r d e n Formation. T h i s u n i t d i r e c t l y o v e r l i e s the Sunbury Shale which is a black, laminated, s i l i c e o u s shale r i c h i n organic matter w i t h some p y r i t e . The S u n b u r y t h i n s t o t h e s o u t h f r o m 20-25 f e e t i n Lewis County to f o u r f e e t i n E s t i l l County. The M i s s i s s i p p i a n S u n b u r y S h a l e i s s e p a r a t e d f r o m t h e u n d e r l y i n g O M - r i c h D e v o n i a n O h i o S h a l e by t h e B e r e a S a n d s t o n e and B e d f o r d S h a l e i n L e w i s C o u n t y and by t h e B e d f o r d S h a l e i n t h e r e maining counties. T h i s i n t e r b u r d e n u n i t t h i n s to the south from o v e r 100 f e e t i n L e w i s C o u n t y t o o n l y a few i n c h e s i n E s t i l l County. The O h i o S h a l e i s d i v i d e d i n t o t h r e e u n i t s as shown i n F i g u r e 3. The C l e v e l a n d Member i s t h e u p p e r u n i t . I t s lower c o n t a c t i s marked a t t h e u p p e r g r e e n i s h - g r a y ( O M - d e f i c i e n t ) s h a l e of t h e T h r e e L i c k Bed. The l o w e r g r e e n i s h - g r a y s h a l e marks t h e t o p o f t h e H u r o n Member. D e p e n d i n g on t h e l o c a t i o n w i t h r e s p e c t t o t h e C i n c i n n a t i a r c h and the a n g u l a r u n c o n f o r m i t y a t t h e b a s e of t h e b l a c k s h a l e , t h e u n d e r l y i n g u n i t may be t h e M i d d l e D e v o n i a n B o y l e D o l o m i t e , the S i l u r i a n Crab O r c h a r d S h a l e , or the S i l u r i a n Bisher Limestone. The C l e v e l a n d Member c o n s i s t s p r i m a r i l y o f b l a c k t o b r o w n ish-black laminated s i l i c e o u s shale. I t c o n t a i n s m i n o r amounts of c a l c a r e o u s l a m i n a e and c o n e - i n - c o n e l i m e s t o n e . Pyrite i s pres e n t as n o d u l e s , f r a m b o i d s , and i r r e g u l a r f o r m s . Other primary m i n e r a l s i n c l u d e i l l i t e c l a y and c l a y - and s i l t - s i z e q u a r t z . The T h r e e L i c k Bed i s a r e g i o n a l s t r a t i g r a p h i e m a r k e r bed t r a c e a b l e t h r o u g h o u t e a s t e r n K e n t u c k y , O h i o , West V i r g i n i a , and Tennessee ( 3 ) . The bed c o n t a i n s t h r e e g r e e n i s h - g r a y s h a l e s d e f i c i e n t i n OM i n t e r b e d d e d w i t h two b r o w n i s h - b l a c k , OM-rich s h a l e s . The g r e e n i s h - g r a y s h a l e s c o n t a i n L i n g u l a , a b u n d a n t t r a c e f o s s i l s , and p y r i t i z e d m i c r o f o s s i l s ( 4 - 5 ) .


GEOCHEMISTRY AND CHEMISTRY OF OIL SHALES


162

Figure 3 explanation.

BORDEN FORMATION. Most important for study are the Nancy and Farmers Members and Henley Bed.Nancy Member i s a gray to greenish*gray clay shale. 100-200* thick. Underlying Farmers Member i s a light gray to yellow siltstone with interbeds of s i l t y shale 20-80* thick. The Henley Bed i s a greenish-gray to gray glauconitic shale T.5-26.8' i n thickness i n study cores. SUNBURY SHALE. Finely laminated black shale with small intervals of brownish-black 13.3-18.U* thick i n cores. Common pyrite bands and nodules, sparsely f o s s i l i f e r o u s . BEREA SANDSTONE. Light gray siltstones and sandy siltstones with interbedded medium to dark-gray shales, becoming more shaley toward the base. Contact with underlying Bedford chosen at the point where shale/siItstone content i s equal. 0-75' thick in study cores. Pyrite blebs and nodules common. BEDFORD SHALE. Medium to dark-gray shale interbedded with l i g h t gray siltstones. Unit i s generally s i l t y toward the top. Pyrite bands and nodules, common to abundant. Scattered siderite nodulea also present. Thickness ranged from 25-68* i n study cores. Decreasing i n thickness from north to south i n Lewis and Fleming counties. Sparsely f o s s i l i f e r o u s .



9. ROBL ET AL.


163

Figure 3. General stratigraphie column for the Devonian-Mississippian black shales in eastern Kentucky.

E x p l a n a t i o n continued OHIO SHALE. Cleveland Member. Black to brownish-black shale in upper part to olive-black to brownish-gray shale i n lower part. Pyrite blebs, stringers and bands, phosphate nodules and thin c a l c i s i l t i t e bands are common. Linguloid brachiopods and Tasmanites are common f o s s i l s . Thickness from 1*9.9-65.0' i n study cores. Three-Lick Bed. Unit consists of three greenish-gray bioturbated shales separated by two black shale beds. Pyrite, present as i n f i l l i n g i n burrows and c a l c i s i l t i t e bands are found. 19.6-11.6' thick i n study cores. Huron Member. Brownish-black to gray-black to brownish-gray shale, also containing intervals of burrowed and bioturbated greenishgray shales. These intervals are abundant toward base of the unit. V i t r a i n bands and a l l forms of pyrite are present, c a l c i s i l t i t e laminae and bands are abundant. Tasmanites, Foerstia, and linguloid and orbiculoid brachiopods are common f o s s i l s in this unit. Thickness i n cores ranged from 208.3-127.8', generally decreasing from north to south i n study area. A regional unconformity occurs at the base of the Huron. BISHER LIMESTONE. Sandy s t y o l i t i c gray to yellowish-gray dolomite. Commonly vuggy with petroleum stained or f i l l e d vugs. Highly variable i n thickness. Ranging from 0-100', generally thicker to north i n study area.


164


The l o w e r u n i t o f t h e O h i o S h a l e w h i c h i s p r e s e n t i n t h e o u t c r o p a r e a o f e a s t e r n K e n t u c k y i s t h e H u r o n Member. Primarily, t h e H u r o n c o n s i s t s o f b l a c k t o b r o w n i s h - b l a c k t o g r a y - b l a c k , lami n a t e d , s i l i c e o u s , OM-rich s h a l e s . Calcareous laminae, c o n e - i n cone l i m e s t o n e , d o l o m i t i c g r a y s h a l e s , d o l o m i t e beds and b i o t u r b a t e d g r e e n i s h - g r a y s h a l e s o c c u r as i n t e r b e d s and l a m i n a e i n t h e l o w e r p a r t s o f t h e member. P y r i t e o c c u r s as f r a m b o i d s , n o d u l e s , and i r r e g u l a r f o r m s .


Definition

of Economic

Zones

F o r t h e r e s o u r c e a s s e s s m e n t s t u d i e s , i t was n e c e s s a r y t o d e f i n e p o t e n t i a l l y mineable o i l shale zones. The r e s u l t i n g nomenc l a t u r e has s u b s e q u e n t l y b e e n c a r r i e d o v e r i n t o t h e g e o c h e m i c a l studies. For the purposes of the r e s o u r c e assessment, o n l y minea b l e o i l s h a l e h a v i n g an o v e r b u r d e n p l u s i n t e r b u r d e n t o s h a l e r a t i o o f l e s s t h a n 2.5:1 was c o n s i d e r e d e c o n o m i c a l . Economic z o n e s were f u r t h e r d e f i n e d as t h o s e r e s o u r c e s w i t h g r e a t e r t h a n 8% c a r b o n (l). I n t h e s t u d y a r e a , t h i s i n c l u d e d a l l o f t h e Sunb u r y S h a l e and a h i g h g r a d e zone (HGZ) o f t h e u p p e r C l e v e l a n d Member o f t h e O h i o S h a l e . T h i s zone e x t e n d s f r o m t h e t o p o f t h e member t o a d e p t h where t h e c a r b o n c o n t e n t d r o p s b e l o w 8%. This 87o l e v e l a l s o c o r r e s p o n d s t o a p o i n t a t w h i c h t h e c a r b o n c o n c e n t r a t i o n i s r a p i d l y d e c r e a s i n g w i t h depth (see F i g u r e 3 ) . A zone o f +8% c a r b o n a l s o o c c u r s i n t h e l o w e r H u r o n , b u t t h i s o i l s h a l e i s a l s o h i g h i n s u l f u r , m i n e r a l c a r b o n , and i s s e p a r a t e d f r o m t h e o t h e r e c o n o m i c z o n e s by a t h i c k s e q u e n c e o f l e a n o i l s h a l e s . The two d e f i n e d e c o n o m i c z o n e s ( S u n b u r y S h a l e and t h e HGZ o f t h e C l e v e l a n d Member) a r e s e p a r a t e d by i n t e r b u r d e n u n i t s o f t h e B e d f o r d S h a l e t h r o u g h o u t t h e s t u d y a r e a and t h e B e r e a S a n d s t o n e i n Lewis County. T h i c k n e s s h i s t o g r a m s o f t h e e c o n o m i c z o n e s and t h e i r a s s o c i a t e d i n t e r b u r d e n u n i t s a r e p r e s e n t e d i n F i g u r e 4, w h i c h shows t h a t t h e S u n b u r y S h a l e d e c r e a s e s i n t h i c k n e s s t o t h e s o u t h w h i l e t h e C l e v e l a n d HGZ r e m a i n s f a i r l y c o n s t a n t a t 25-30' thick. The B e d f o r d and B e r e a d e c r e a s e i n t h i c k n e s s r a p i d l y t o ward t h e s o u t h w i t h l e s s t h a n a f o o t o f i n t e r b u r d e n s e p a r a t i n g t h e two e c o n o m i c z o n e s i n Montgomery C o u n t y . Organic

Geochemistry

General. The o r g a n i c g e o c h e m i s t r y o f t h e s t u d y s a m p l e s i s summ a r i z e d by t h e e l e m e n t a l a n a l y s i s d a t a i n T a b l e I . E x t e n s i v e det a i l e d d a t a on t h e s e s a m p l e s on a c o r e - b y - c o r e b a s i s a r e a v a i l able i n previous reports (1-6-7). C a r b o n d a t a p r e s e n t e d and d i s c u s s e d h e r e i n a r e g i v e n as t o t a l carbon unless s p e c i f i e d otherwise. M i n e r a l carbon c o n t r i b u t i o n s f r o m c a l c i t e and d o l o m i t e a r e t y p i c a l l y i n s i g n i f i c a n t i n comparison to t o t a l carbon v a l u e s . Average m i n e r a l carbon cont e n t s f o r t h e K - s e r i e s s t r a t i g r a p h i e u n i t s a r e as f o l l o w s : Sunb u r y , 0.01%; C l e v e l a n d , 0.06%; and H u r o n , 0.13%,. Comparative



165


ROBL ET AL.

Figure 4. Cross-section ofthe thicknesses ofthe stratigraphie units above the base ofthe Cleveland HGZ (top), and variation in hydrogen and carbon for the Sunbury shale and Cleveland HGZ in eastern Kentucky (bottom).



2.79(12)

3.70(12)

3.15(3)

2.51(8)

2.42(6)

2

numbers i n parentheses are c o e f f i c i e n t s of v a r i a t i o n χ 100

1 wt. % raw s h a l e ; H c o r r e c t e d f o r surface moisture

2.93(10) 3.61(7)

.23(16)

3.54(8)

S

.36(10)

.32(10)

.44(10)

.22(7)

.39(3)

.39(4)

.41(5)

Ν

.76(12) 1.25(5)

1.09(5)

1.47(14)

.66(6)

1.21(7)

.99(2)

1.20(4)

Η

6.57(15)

11.08(3)

9.61(4)

13.12(10)

11.42(3)

ci

5.61(3)

Huron Shale

D-Series Cleveland Shale HGZ Total

Sunbury Shale

Huron Shale

11.11(3)

2

K-Series Cleveland Shale HGZ Total

9.04(2)

Sunbury Shale

TABLE I . ORGANIC ELEMENTAL ANALYSIS DATA FOR K- AND D-SERIES OIL SHALES


C/3

r m

Χ >

Ο τι Ο r

> α ο χ m

Η

So

Ο m Ο Π χ m

9.

ROBL ET AL.



data from t h e D - s e r i e s a r e : S u n b u r y , 0.14%; C l e v e l a n d , 0 . 1 0 7 » ; and H u r o n , 0 . 4 4 7 , . A g e n e r a l t r e n d toward i n c r e a s i n g m i n e r a l c a r bon i n t h e s o u t h e r l y s a m p l e s o f t h e s t u d y a r e a i s e v i d e n t . Dis t i n c t c a l c i t i c b a n d s i n t h e c o r e s do o c c u r b u t were removed a n d a n a l y z e d s e p a r a t e l y and t h u s a r e n o t a c c o u n t e d f o r i n t h e above data. Hydrogen i s p r e s e n t i n these s h a l e s as s u r f a c e m o i s t u r e , m i n e r a l - b o u n d h y d r a t i o n water, and o r g a n i c a l l y - b o u n d h y d r o g e n . S u r f a c e m o i s t u r e was d e t e r m i n e d f o r e a c h s a m p l e ; c o n s e q u e n t l y , t h i s hydrogen c o n t r i b u t i o n i s c o r r e c t e d f o r i n the presented data. Mineral-bound hydrogen, being d i f f i c u l t t o determine d i r e c t l y , i s i n c l u d e d i n the hydrogen data presented. However, p o s i t i v e i n t e r c e p t s o f H v s . C p l o t s i n d i c a t e a p p r o x i m a t e l y 0 . 2 wt. hydrogen from m i n e r a l o r i g i n s . The c o n s i s t e n c y o f t h i s d a t a f o r g e n e r a l assignment t o mineral-bound hydrogen c o n t r i b u t i o n s i s under c u r r e n t i n v e s t i g a t i o n . N i t r o g e n o c c u r s a l m o s t e x c l u s i v e l y as o r g a n i c n i t r o g e n a n d Ν v s . C p l o t s a r e l i n e a r and p o s s e s s r e l a t i v e l y c o n s t a n t s l o p e v a l u e s i n d i c a t i n g a uniform geochemical presence o f t h i s element i n these s h a l e s . S u l f u r o c c u r r e n c e i n t h e s e s h a l e s i s composed o f o r g a n i c , s u l f i d e , and s u l f a t e c o n t r i b u t i o n s . Our d a t a i n d i c a t e t h a t >80%, o f t h e s u l f u r o c c u r s i n s u l f i d e m i n e r a l s , predom i n a n t l y as p y r i t e ( F e S 2 ) . C u r r e n t r e s e a r c h i s aimed a t r e f i n e ment o f t h e s u l f u r - f o r m s d a t a , p r i m a r i l y t o a s s e s s t h e o r g a n i c s u l f u r content of these s h a l e s . B a s e d on p r e s e n t d a t a , t h e o v e r a l l s t o i c h i o m e t r y o f t h e raw o i l s h a l e o r g a n i c m a t e r i a l i s g i v e n by t h e e m p i r i c a l f o r m u l a CH]_ 3N Q31» T h i s c a n be compared t o f o r m u l a s g i v e n f o r w e s t e r n o i l s h a l e s , e . g . C H i 5 N o . 0 3 2 ( 8 ) a n d C H x N 2 7 (£)· T h e s e d a t a i n d i c a t e t h a t t h e e a s t e r n o i l s h a l e s o f K e n t u c k y a r e more aroma t i c i n c h a r a c t e r than the western o i l s h a l e s . This characteris t i c manifests i t s e l f i n a s l i g h t hydrogen d e f i c i e n c y which u l t i mately l i m i t s o i l y i e l d . The r e m a r k a b l y s i m i l a r N/C r a t i o s b e tween t h e two o i l s h a l e s i s a l s o n o t a b l e . e

e

#

e 7

e 0

S t r a t i g r a p h i e and R e g i o n a l T r e n d s . Strong s t r a t i g r a p h i e trends are e v i d e n t i n t h e d i s t r i b u t i o n o f carbon i n t h e study c o r e s , as Figure 3 i l l u s t r a t e s . In g e n e r a l , the carbon content i n c r e a s e s from t o p t o bottom i n t h e Sunbury S h a l e , w i t h c a r b o n v a l u e s o f a p p r o x i m a t e l y 9-107, a t t h e t o p t o 157, a t t h e b a s e . This pattern i s r e v e r s e d i n t h e u n d e r l y i n g C l e v e l a n d Member o f t h e O h i o S h a l e The t o p o f t h e C l e v e l a n d h a s a c a r b o n c o n t e n t s i m i l a r t o t h e b a s o f t h e S u n b u r y , w i t h v a l u e s d e c r e a s i n g t o 4-67, t o w a r d i t s b a s e . The T h r e e L i c k Bed o f t h e O h i o S h a l e shows h i g h l y v a r i a b l e d i s t r i b u t i o n o f carbon, which i s as e x p e c t e d , as t h i s u n i t i s de f i n e d on t h e b a s i s o f 3 O M - d e f i c i e n t , b i o t u r b a t e d g r e e n s h a l e s . The p a t t e r n o f c a r b o n d i s t r i b u t i o n i n t h e H u r o n Member o f t h e Ohio Shale i s the i n v e r s e o f the C l e v e l a n d ; the carbon content i n c r e a s e s t o w a r d t h e base o f t h i s u n i t , r e a c h i n g v a l u e s o f 9-107, T h i s p a t t e r n i s somewhat b r o k e n up by t h e p r e s e n c e o f b u r r o w e d


168



and b i o t u r b a t e d g r e e n - s h a l e Huron.

intervals

toward

the base of the

When t h e d a t a o f T a b l e I a r e compared, t h e i n t e r - c o r e o r g a n i c geochemistry of the i n d i v i d u a l shale u n i t s i s r e l a t i v e l y cons i s t e n t c o n s i d e r i n g t h e v a r i a n c e among t h e u n i t s . A s l i g h t average d e c r e a s e t o w a r d t h e l o w e r u n i t s i s e v i d e n t , h o w e v e r . Interc o r e H/C r a t i o s f o r t h e s e d a t a a r e e s s e n t i a l l y c o n s t a n t , b u t s l i g h t l y h i g h e r H/C r a t i o s i n t h e u p p e r C l e v e l a n d s h a l e s r e l a t i v e t o t h e S u n b u r y have b e e n o b s e r v e d . I n t e r - c o r e N/C r a t i o s a r e g e n e r a l l y h i g h e r f o r the l e a n e r Huron s h a l e s ; t h i s correspondence has a l s o been n o t e d f o r W e s t e r n o i l s h a l e s ( 8 - 9 ) . R e g i o n a l t r e n d s i n t h e study a r e a a r e i l l u s t r a t e d f o r carbon, h y d r o g e n , a n d s u l f u r i n F i g u r e U. T h e c a r b o n - h y d r o g e n c o n t e n t s o f t h e S u n b u r y S h a l e a r e 11 and 1.1% r e s p e c t i v e l y , i n t h e n o r t h ern ( L e w i s C o u n t y ) c o r e s a n d p e a k a t 15 a n d 1.8%, i n t h e P o w e l l County core s i t e s b e f o r e d e c r e a s i n g s l i g h t l y a g a i n toward t h e south of the study a r e a . The most r a p i d i n c r e a s e i n c a r b o n and h y d r o g e n o c c u r s a s t h i s u n i t t h i n s and may be r e f l e c t i v e o f s l o w er d e p o s i t i o n a l r a t e s . R e g i o n a l C-H t r e n d s f o r t h e C l e v e l a n d HGZ a r e a l s o i l l u s t r a t e d b u t a r e n o t as d i s t i n c t a s t h o s e o f S u n b u r y Shale. S h a l e v a r i a b i l i t y a s d e t e r m i n e d by t h e c o e f f i c i e n t s o f v a r i a t i o n i n T a b l e I i s g e n e r a l l y 2-3 t i m e s g r e a t e r f o r t h e Ds e r i e s as compared t o t h e K - s e r i e s s a m p l e s . T h i s i s accounted f o r by t h e g r e a t e r r e g i o n a l change w i t h i n t h e D - s e r i e s a r e a . Regional trends f o r s u l f u r g e n e r a l l y f o l l o w carbon f o r both u n i t s , but l e v e l s o f the element a r e n o t i c e a b l y lower i n the C l e v e l a n d r e l a t i v e t o the Sunbury. Organic Geochemistry - F i s c h e r Assay R e l a t i o n s h i p s . Conventional and m o d i f i e d F i s c h e r a s s a y a n a l y s e s h a v e b e e n p e r f o r m e d on many S u n b u r y and C l e v e l a n d HGZ o i l s h a l e s a m p l e s . The m e a n i n g o f F i s c h e r a s s a y r e s u l t s when a p p l i e d t o E a s t e r n U. S. o i l s h a l e s i s somewhat a m b i g u o u s . Such r e s u l t s do p r o v i d e a b a s i s f o r c o m p a r i son among t h e s t u d y s a m p l e s b u t p r o b a b l y u n d e r e s t i m a t e t h e amount o f e x t r a c t a b l e o i l f r o m t h e s h a l e a n d , c o n s e q u e n t l y , do n o t p r o v i d e an a c c u r a t e method f o r a s s e s s i n g t h e t o t a l r e c o v e r a b l e e n e r gy f r o m t h e s e s h a l e s . Comments c o n c e r n i n g t h e a p p l i c a b i l i t y o f t h e F i s c h e r a s s a y t e s t t o e a s t e r n s h a l e s have b e e n made i n p r e v i o u s r e p o r t s by o u r c o l l e a g u e s ( 1 1 - 1 2 ) and g e n e r a l l y i n d i c a t e t h a t t h e s e o i l s h a l e s a r e much more s e n s i t i v e t o h e a t i n g r a t e , p r o d u c t r e m o v a l , and r e t o r t a t m o s p h e r e v a r i a b l e s . The d a t a a l s o i n d i c a t e t h a t F i s c h e r a s s a y d a t a f o r t h e same s a m p l e s among d i f f e r e n t p e r f o r m i n g l a b o r a t o r i e s a r e q u i t e v a r i a b l e and a r e p r o b a b l y i n d i c a t i v e o f b o t h l a b o r a t o r y and o i l s h a l e c h a r a c t e r i s t i c s . When t h e body o f F i s c h e r a s s a y d a t a on t h e K - s e r i e s s a m p l e s i s e v a l u a t e d , mean v a l u e s f o r t h e w e i g h t e d a v e r a g e s o f t h e s e c o r e s a r e 10.3 and 11.9 g a l / t o n f o r S u n b u r y a n d C l e v e l a n d HGZ, respectively. C o e f f i c i e n t s o f v a r i a t i o n o f 8.2%, ( S u n b u r y ) and 6.9%, ( C l e v e l a n d HGZ) were o b s e r v e d w i t h a t o t a l r a n g e o f a s s a y v a l u e s r a n g i n g f r o m 5.4 t o 18.4 g a l / t o n . C u r r e n t d a t a f o r some


9.

ROBL ET AL.

169



D - s e r i e s s a m p l e s a r e g i v e n i n F i g u r e 5, w h i c h i l l u s t r a t e s t h e F i s c h e r assay-raw o i l s h a l e carbon c o n t e n t r e l a t i o n s h i p f o r the two o i l s h a l e u n i t s . I t i s e v i d e n t t h a t the C l e v e l a n d o i l s h a l e y i e l d s s l i g h t l y more o i l t h a n t h e S u n b u r y o i l s h a l e , i n s p i t e o f t h e f a c t t h a t t h e S u n b u r y S h a l e a v e r a g e s more c a r b o n p e r u n i t weight. T h i s same r e l a t i o n s h i p was o b s e r v e d f o r t h e two o i l s h a l e u n i t s f r o m t h e K - s e r i e s (6) and i s assumed t o be r e f l e c t i v e o f k e r o g e n d i f f e r e n c e s b e t w e e n t h e two o i l s h a l e s . Correlation of F i s c h e r assay w i t h hydrogen content y i e l d s s l i g h t l y b e t t e r c o r r e l a t i o n s i n d i c a t i n g a g a i n the c r i t i c a l i t y o f the hydrogen content of these s h a l e s . I l l u s t r a t i v e F i s c h e r a s s a y y i e l d s and a s s o c i a t e d o i l and gas c o m p o s i t i o n d a t a a r e p r e s e n t e d i n T a b l e 2 f o r b o t h e a s t e r n (10) and w e s t e r n ( 8 ) o i l s h a l e s o f n o m i n a l l y s i m i l a r o r g a n i c c a r b o n content. The e a s t e r n o i l s h a l e s y i e l d more gas and w a t e r and l e s s o i l than the w e s t e r n o i l s h a l e used f o r comparison. The major d i f f e r e n c e s i n the o i l c o m p o s i t i o n i n c l u d e c o m p a r a t i v e l y l o w e r n i t r o g e n and h i g h e r s u l f u r c o n t e n t s f o r t h e S u n b u r y and Cleveland shale o i l s . The l o w e r H/C r a t i o f o r t h e e a s t e r n o i l s i n d i c a t e a more a r o m a t i c o i l , as r e p o r t e d p r e v i o u s l y ( U_). Assay gas c o m p o s i t i o n f o r t h e e a s t e r n o i l s h a l e s i n d i c a t e h i g h e r H2, and contents with less and contents. The lower l e v e l s i n t h e c a s e o f t h e e a s t e r n o i l s h a l e s a r e due t o a more e f f i c i e n t c o n d e n s a t i o n o f t h o s e g a s e s t o t h e l i q u i d p r o d u c t i n our a s s a y p r o c e d u r e s ( 1 2 - 1 3 ) . Gas c l e a n u p w o u l d u l t i m a t e l y be e x p e c t e d t o y i e l d a h i g h e r B t u gas f o r t h e e a s t e r n o i l s h a l e - d e r i v e d gas t h a n a c o r r e s p o n d i n g w e s t e r n gas due t o e l i m i n a t i o n o f H2S i n t h e f o r m e r and h i g h CO2 l e v e l s and c o n d e n s a t i o n o f much o f t h e range i n the l a t t e r . F i n a l l y , i t s h o u l d be emphasized t h a t the c o m p o s i t i o n a l i n f o r m a t i o n p r e s e n t e d i s based on F i s c h e r a s s a y r e t o r t i n g p r o c e d u r e s and may n o t be e n t i r e l y r e p r e s e n t a t i v e of p r o d u c t s produced under commercial s c e n a r i o s .

CH4, H2S C3-C5

C3-C6

CO2

C4-C6

Inorganic

Geochemistry

Minéralogie Composition. The s u b j e c t s h a l e s a r e d e s i g n a t e d s i l t y s h a l e s due t o t h e i r h i g h q u a r t z c o n t e n t . The m i n é r a l o g i e compos i t i o n o f t h e s e s h a l e s has b e e n s t u d i e d ( 1 4 - 1 8 ) and i s summar i z e d i n T a b l e I I I . I l l i t e (2M), m u s c o v i t e a n d / o r i l l i t e / s m e c t i t e are the predominant c l a y s found i n these s h a l e s . S t r a t i g r a p h i e D i s t r i b u t i o n and R e g i o n a l T r e n d s . M a j o r and t r a c e e l e m e n t d e t e r m i n a t i o n s were p e r f o r m e d and a r e p r e s e n t e d as w e i g h t p e r c e n t o r ppm o f t h e 5 0 0 ° C a s h f r a c t i o n o f t h e s a m p l e s . This was done t o e l i m i n a t e t h e e f f e c t o f v a r i a t i o n i n o r g a n i c c o n t e n t and t o f a c i l i t a t e comparisons. When t h e m a j o r e l e m e n t c h e m i s t r y f o r t h e v a r i o u s s t r a t i g r a p h i e u n i t s a r e compared, no l a r g e d i f f e r e n c e s a r e f o u n d ( T a b l e 4), The c o n c e n t r a t i o n o f i n t h e s h a l e s i s l e s s t h a n what w o u l d be e x p e c t e d f r o m a c l a y s h a l e , w h i c h t o g e t h e r w i t h t h e S1O2 con-

AI2O3



170


Carbon, Weight % Figure 5. Plot of Fischer assay yields and carbon content for D series oil shales. Regression data are: Sunbury Shale, oil yield - 1.03 (%C) - 0.69 (r - .97): and Cleveland Shale, oil yield = 1.18 f%C) - 1.16 (r = .97).


9.

ROBL ET AL.

TABLE I I .

171


FISCHER ASSAY YIELDS WITH OIL AND GAS COMPOSITION DATA FOR EASTERN VS. WESTERN OIL SHALES

O i l Shale Formation

Sunbury*

Cleveland

2

Green R i v e r ^

YIELDS : O i l , gal/ton Gas, f t / t o n Water, g a l / t o n Downloaded by TUFTS UNIV on June 12, 2018 | https://pubs.acs.org Publication Date: August 1, 1983 | doi: 10.1021/bk-1983-0230.ch009

3

13.4 740. 16.6

14.4 684. 9.8

29.8 461. 3.8

OIL COMPOSITION: C, wt.% H, wt.% N, wt.% S, wt.% Density Btu/lb.

82.41 10.11 0.77 2.75 0.9199 17,800

83.25 10.35 0.86 2.38 0.9197 17,800

84.80 11.60 1.96 0.60 0.9180 18,750

GAS COMPOSITION, V o l . %: H CH C H C H 2

4

2

4

2

6 c

C3" 6 C0 CO HS Btu/SCF 2

2

30.6 24.0 1.60 6.09 3.88 7.16 4.14 15.2 740

37.0 22.2 1.50 5.98 4.34 5.53 3.33 20.4 743

25.7 16.5 2.30 6.7 11.7 31.1 0.7 1.0 776 4

1

KY,

2

KY,

Data from reference 29, sample SUN-002, Lewis Co., organic carbon = 13.85% Data from reference 29, sample CLE-002, Lewis Co., organic carbon = 14.54% 3

1

f

Data from reference 8, sample 482B B , organic carbon = 13.61% ^ C a l c u l a t e d by authors

A n v i l P o i n t s , CO,


4

172


Table

III.

Modal Minéralogie C o m p o s i t i o n Cleveland(14)

Quartz Pyrite Illite 11lite/Muscovite ν


Illite/Smectite Mixed Layered Kaolinite Chlorite Carbonates Feldspar Organics

30 5 39 20

1 /

Trace 7 Minor Minor (on Ash B a s i s )

of Devonian O i l Shales. Chattanooga(15-16-17) 20-25 10-15

25-30

Minor Trace Variable 10 15-20

tent, substantiates i t s s i g n i f i c a n t quartz content. The l e v e l o f K 0 p r e s e n t ( a b o u t 4%) i n d i c a t e s t h a t t h e c l a y s a r e p r i m a r i l y i l l i t e or muscovite-mica which agrees w i t h minéralogie determinat i o n s made on t h e raw s h a l e s . The CaO c o n c e n t r a t i o n i n a l l o f t h e s t r a t i g r a p h i e u n i t s i s low ( g e n e r a l l y l e s s t h a n 1.0% ( T a b l e I V ) ) , a l s o i n a g r e e m e n t w i t h t h e p r e v i o u s o b s e r v a t i o n s made f o r mineral carbon. C a l c i u m c o n t e n t i s g e n e r a l l y h i g h e r i n t h e Huron, p a r t i c u l a r l y i n t h e D-5 t h r o u g h D-8 c o r e s where t h e D u f f i n and Ravenna l i t h o l o g i e s a r e p r e s e n t . There i s a l s o a s l i g h t geograp h i c t r e n d o f i n c r e a s i n g CaO c o n c e n t r a t i o n s f r o m n o r t h t o s o u t h in the study a r e a . 2

The c o e f f i c i e n t s o f v a r i a t i o n d e t e r m i n e d among t h e c o r e s f o r t h e m a j o r e l e m e n t o x i d e s a r e g e n e r a l l y v e r y low ( T a b l e I V ) a n d i n many c a s e s a l m o s t a t t h e l e v e l o f a n a l y t i c u n c e r t a i n t y . Two e x c e p t i o n s t o t h i s a r e CaO a n d P 0 5 w h i c h a r e a s s o c i a t e d w i t h c a r bonate m i n e r a l s and phosphate n o d u l e s . These a r e not p a r t o f the p r i m a r y l i t h o l o g i e s o f t h e s h a l e and a r e s u b j e c t t o b e i n g e i t h e r l o c a l l y abundant o r a b s e n t . U n l i k e the o r g a n i c elements, the major e l e m e n t a l c h e m i s t r y does n o t show l a r g e s t r a t i g r a p h i e z o n a t i o n compared t o i t s l a t e r al continuity. C o e f f i c i e n t s of v a r i a t i o n f o r the s t r a t i g r a p h i e i n t e r v a l s are only s l i g h t l y g r e a t e r than those c a l c u l a t e d f o r the average core d a t a . However, t h e c o n c e n t r a t i o n and d i s t r i b u t i o n of t h e d e t e r m i n e d t r a c e e l e m e n t s a r e s t r a t i g r a p h i c a l l y c o n t r o l l e d . H i g h e s t c o n c e n t r a t i o n s a r e f o u n d i n t h e S u n b u r y , f o l l o w e d by t h e C l e v e l a n d and t h e H u r o n . The e l e m e n t s w h i c h show t h e g r e a t e s t z o n a t i o n b a s e d on s t r a t i g r a p h i e u n i t i n c l u d e Mo, N i , V, and Z n . E a c h o f t h e s e e l e m e n t s i s f o u n d t o have c o n c e n t r a t i o n s i n t h e Sunb u r y a t l e v e l s o f 2-3 t i m e s t h o s e o f t h e o t h e r u n i t s ( T a b l e I V ) . As i n t h e c a s e o f t h e m a j o r e l e m e n t s , t h e c o e f f i c i e n t s o f v a r i a t i o n c a l c u l a t e d f o r t h e t r a c e e l e m e n t s among t h e c o r e s f o r t h e s t r a t i g r a p h i e i n t e r v a l s a r e v e r y low i n most c a s e s ( T a b l e I V ) . U n l i k e t h e m a j o r s , however, t h e s t r a t i g r a p h i e v a r i a t i o n s o f t r a c e 2


TABLE IV.

INORGANIC COMPOSITION FOR K- AND D-SERIES OIL SHALES

K-Sertes Sunbury Shale S102


Ti0

1

2

A1 0 2

3

Fe2Û3T CaO

173


9. ROBL ET AL.

D-Series Cleveland Shale HGZ Total

Huron Shale

Cleveland Shale HGZ Total

Huron Shale

Sunbury Shale

66.6(1)

66.5(1)

64.4(1)

64.18(3)

65.78(1)

66.16(2)

61.93(2)

.8(5)

.9(1)

.8(1)

.9(1)

.76(6)

.85(3)

.82(2)

.85(4)

16.7(6)

16.4(1)

16.2(1)

16.6(1)

15.58(2)

15.57(3)

15.15(4)

16.12(4)

8.7(5)

6.8(2)

7.0(3)

7.9(3)

6.67(4)

6.83(6)

8.20(4)

63.7(3)

2

.4(28)

.6(21)

.6(20)

.9(29)

8.12(11) .88(114)

.90(36)

.84(43)

1.33(64)

MgO

1.5(6)

1.3(3)

1.4(2)

1.3(5)

1.43(4)

1.37(5)

1.36(5)

1.78(22)

K 0

4.4(7)

4.3(1)

4.2(2)

4.3(1)

4.11(3)

4.13(3)

4.08(3)

4.26(3)

2

Na 0

.4(20)

.5(13)

.5(13)

.5(8)

.38(19)

.50(15)

.47(18)

.54(11)

P 0

ND

ND

ND

ND

.29(77)

.22(44)

.28(48)

.12(23)

2

2

Ba3

5

645(4)

619(3)

607(3)

633(3)

622(7)

570(4)

568(4)

564(5)

Co

24(3)

21(2)

20(2)

25(2)

24(6)

19(3)

19(4)

27(3)

Cr

200(3)

159(2)

195(4)

90(1)

175(10)

151(19)

185(4)

93(4)

Cu

113(3)

91(3)

111(4)

57(3)

134(9)

97(6)

114(5)

74(20)

Mo

281(5)

94(3)

89(8)

66(5)

248(15)

104(4)

92(7)

Ni

272(3)

125(9)

141(2)

81(3)

288(14)

129(4)

139(3)

V

1533(5)

760(5)

1024(5)

209(3)

1155(24)

677(4)

796(6)

216(5)

Zn

1126(6)

444(5)

622(7)

144(8)

1202(15)

412(8)

510(7)

173(9)

37(5)

20(7)

20(7)

43(15)

21(4)

19(4)

22(6)

U

1

wt. 7. i n 500°C Ash

2

C o e f f i c i e n t s of v a r i a t i o n χ 100

3

ppm (wt.) i n 500°C Ash

ND


86(6) 96(13)


174

element

are

high.

This

concentration

reflects

the

differences


among t h e s t r a t i g r a p h i e u n i t s . The c o n c e n t r a t i o n s o f c e r t a i n t r a c e e l e m e n t s a l s o a p p e a r t o show r e g i o n a l t r e n d s . As an example o f t h e s e t r e n d s , F i g u r e 6 p r e s e n t s the r e g i o n a l d i s t r i b u t i o n o f Mo, N i , V, and Zn. Each of t h e s e e l e m e n t s shows a s l i g h t o v e r a l l d e c r e a s e i n c o n c e n t r a t i o n between L e w i s C o u n t y (K-9 o r 8) i n t h e n o r t h and E s t i l l C o u n t y (D-10) i n t h e s o u t h f o r b o t h t h e S u n b u r y and t h e C l e v e l a n d HGZ. However, the r e g i o n a l t r e n d s f o r t h e S u n b u r y a r e somewhat obs c u r e d by an i n c r e a s e i n c o n c e n t r a t i o n f o r Mo, N i , and Zn, and a d e c r e a s e i n c o n c e n t r a t i o n f o r V i n t h e r e g i o n b e t w e e n Montgomery and P o w e l l C o u n t i e s . The c a u s e f o r t h e s e r e g i o n a l a n o m a l i e s i s presently unclear. Table

V.

C o r r e l a t i o n C o e f f i c i e n t s f o r Metals Affinités Eastern

Element

Lithologie

Unit

K-Series Carbon

Data Sulfur

Co

Sunbury Cleveland Huron

-.38 .23 .67

.85 .76 .90


.17 .95 -.45

-.34

Cr

Cu


.81 .95 .54

-.12 .44 .49

Mo


.15 .11 .90

.08 -.12 .78

Sunbury

.40 .91 .40

.25 .37 .17

.07 .82

.15 .10 -.17

Ni

Cleveland Huron Sunbury Cleveland Huron

V

Underlined

of

Shales.

coefficients

.01 considered

.51 -.55

significant

Trace Metal Affinités. T r a c e - e l e m e n t and m a j o r - e l e m e n t a s s o c i a t i o n s i n t h e o i l s h a l e s h a v e b e e n a s u b j e c t o f two s t u d i e s ( 1 9 20). I n g e n e r a l , t h e t r a c e e l e m e n t s c a n be d i v i d e d i n t o t h r e e groups: t h o s e w h i c h have an a f f i n i t y f o r c a r b o n (Cu, C r , N i , V ) , t h o s e w h i c h h a v e an a f f i n i t y f o r s u l f u r (Co, Z n ) , and t h o s e w h i c h have an a f f i n i t y f o r t h e s i l i c a t e s and c a r b o n a t e s (Ba) ( n o t r e ported here). To some d e g r e e t h e a s s o c i a t i o n s a r e s t r a t i g r a p h -


9. ROBL ET AL.


175

|CI«v*l«nd High

~

1200

ι .

i I

I" I

J

ν//

I


-

Β

Geochemistry of Oil Shales in Eastern Kentucky

Recommend Documents