Geology and Geochemistry of Some Queensland Tertiary Oil Shales

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Geology a n d Geochemistry o f S o m e Q u e e n s l a n d T e r t i a r y Oil S h a l e s A. W. LINDNER

Downloaded by FUDAN UNIV on April 8, 2017 | http://pubs.acs.org Publication Date: August 1, 1983 | doi: 10.1021/bk-1983-0230.ch006

Southern Pacific Petroleum N.L., 143 Macquarie Street, Sydney 2000, Australia There are at least 13 Tertiary o i l shale deposits scattered along 900 km of coastal Queensland with an in situ shale oil resource totalling in excess of 25 billion barrels of shale o i l . The paper compares aspects of the geochemistry for five of these deposits, which contain about two thirds of the demonstrated resource. The o i l shales are moist, with a dominance of clay and silica minerals, a range of accessory minerals including siderite, feldspar and lesser amounts of gypsum, calcite, dolomite, pyrite and a number of phosphate minerals. Organic petrography and organic element analysis reveal that the source of the kerogen is algal (lamosites dominating) while other maceral forms dominate locally to form carbonaceous shale and humic coals. Oil shale was first discovered in Queensland almost a century ago when dredging The Narrows, a 30 km long, shallow passage of the sea separating Curtis Island from the mainland north of Gladstone (Figure 1). The flammable rock aroused some prospecting interest for a number of years but the first serious attempt to assess the resource within The Narrows Graben did not take place until half a century later, during World War II. By this time, several other occurrences of oil shale along the coastal strip of Queensland had been reported. Typically, the Queensland Tertiary o i l shales are sparsely exposed and deeply weathered. Because of this the extent of the deposits has only been determined by drilling. At the end of 1980, 38 exploration groups were involved in the search for o i l shale deposits in Queensland (JL) . Much of this effort has been directed towards Tertiary oil shale, now known to occur in at least 13 separate basinal areas (Figure 2). 0097-6156/ 83/0230-0097S06.50/0 © 1983 American Chemical Society Miknis and McKay; Geochemistry and Chemistry of Oil Shales ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

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

Figure 1. Location offour Tertiary basins in eastern Queensland.


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GEOCHEMISTRY AND CHEMISTRY OF OIL SHALES

This paper compares aspects of geology and geochemistry of the o i l shales contained i n 4 basins : The Narrows Graben c o n t a i n i n g Rundle and S t u a r t d e p o s i t s ; H i l l s b o r o u g h Basin c o n t a i n i n g the Condor d e p o s i t ; the Duaringa deposits of the Duaringa Basin and the B y f i e l d deposit i n the Water Park Creek Basin. Southern P a c i f i c Petroleum N.L. and C e n t r a l P a c i f i c M i n e r a l s N.L. (SPP/CPM) commenced e x p l o r a t i o n f o r o i l shale near The Narrows i n 1974, c o n c e n t r a t i n g on what was subsequently defined as the Rundle d e p o s i t . From 1977, the S t u a r t deposit was o u t l i n e d . During 1978, SPP/CPM began p r o s p e c t i n g i n s e v e r a l of the other basins which h e l d the a t t r a c t i o n of favourable l o c a t i o n , p r o x i m i t y to p o p u l a t i o n centres and i n f r a s t r u c t u r e f a c i l i t i e s . Very l i t t l e i n f o r m a t i o n was a v a i l a b l e on the t h i c k n e s s and d i s t r i b u t i o n of o i l shales i n these b a s i n s , although Duaringa and H i l l s b o r o u g h were known to be l a r g e i n a r e a l extent and to have a t o t a l s e c t i o n thickness comparable to that at The Narrows Graben. The Duaringa and H i l l s b o r o u g h Basins had p r e v i o u s l y been i n v e s t i g a t e d c u r s o r i l y f o r t h e i r petroleum p o t e n t i a l without success. In the f i v e d e p o s i t s under review the demonstrated in situ shale o i l resource exceeds 17 b i l l i o n b a r r e l s (at a c u t - o f f grade of 50 l i t r e s / t o n n e at 0% r e t o r t water (LTOW) over a 4 metre minimum mining t h i c k n e s s . This c u t - o f f grade i s used h e r e i n when resource dimensions are s p e c i f i e d ) . A l l e x p l o r a t i o n d r i l l i n g by SPP/CPM has had the o b j e c t i v e of complete core recovery. The d r i l l core i s logged f o r l i t h o l o g y and bulk d e n s i t y , then s p l i t and assayed on 2m i n t e r v a l s , w i t h one h a l f being assayed and the other h a l f r e t a i n e d i n t r a y s i n the Companies core storage f a c i l i t i e s . Except at Condor, the b u l k d e n s i t y has a d i r e c t p r o p o r t i o n a l r e l a t i o n s h i p to o i l y i e l d . The modified F i s c h e r Assay (USBM RI 6676 and more r e c e n t l y ASTM D.4904) has been used f o r determining grade of o i l s h a l e . From experience w i t h the Queensland s h a l e s , an 80 g charge i s used i n the F i s c h e r r e t o r t . The h a l f core 2 metre i n t e r v a l provides from 3 to 5 kg of sample and the assay r e j e c t s are r e t a i n e d and provide a sample bank f o r c h a r a c t e r i s a t i o n t e s t s c a r r i e d out on the o i l shale seams. 1

Geology of the Deposits During the P a l e o z o i c and e a r l y Mesozoic, the r e g i o n now represented by eastern c o a s t a l Queensland developed by c o n t i n e n t a l a c c r e t i o n to the A u s t r a l i a n S h i e l d . Sedimentary basins w i t h marine and d e l t a i c sequence and c o n t a i n i n g v o l c a n i c deposits have undergone periods of compressive deformation accompanied by igneous i n t r u s i o n s . The t e c t o n i c g r a i n superimposed on the basins of t h i s r e g i o n s t r i k e s northwest (Figure 2 ) .


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Towards the end o f the Mesozoic, a new c o n t i n e n t a l margin developed and oceanic c r u s t i n i t i a l l y appeared i n the Tasman Sea r e g i o n , extending l a t e r ( i n e a r l y T e r t i a r y ) t o the C o r a l Sea r e g i o n ( 2 ) . A s s o c i a t e d w i t h t h i s new c o n t i n e n t a l margin, a number of grabens developed w i t h i n the continent along the o l d e r t e c t o n i c g r a i n , during the Eocene. This appears to be the framework i n which the t h i c k , e s s e n t i a l l y l a c u s t r i n e sequences c o n t a i n i n g o i l shales accumulated i n narrow, l i n e a r , f a u l t bounded basins ( 3 ) , i n some cases w i t h accompanying igneous activity. The Narrows Graben. From bore data the Rundle and S t u a r t deposits comprise a composite t h i c k n e s s i n excess of 990 metres, as the basement f l o o r of the graben was not reached (Figure 3 ) . The sequence and extent of the resource i n the Rundle and S t u a r t d e p o s i t s i s discussed f u l l y by Henstridge and Missen ( 4 ) . The b a s a l u n i t (Worthington beds) i n c l u d e s agglomerate sourced from adjacent P a l e o z o i c basement passing upwards i n t o a sequence of colour-laminated red and green incompetent, s o f t , moist claystones and sandy c l a y s t o n e s . The o i l shale resource i s confined t o the conformably o v e r l y i n g Rundle Formation (580m) and comprises s i x seams (Teningie Creek, Ramsay C r o s s i n g , B r i c k K i l n , Humpy Creek, Munduran Creek, Kerosene Creek). As the organic content i n c r e a s e s , the claystones become l u s t r o u s and develop a waxy s t r e a k . Brown t o grey- brown colours predominate. The h i g h moisture content o f the rock p e r s i s t s . Kerogen adds t o the toughness o r cohesiveness of the rock; the p a r t i n g o r bedding planes add t o the appearance of a s h a l e . O x i d a t i o n c o l o u r s a r e absent i n the Rundle Formation except i n some b a s i n margin areas. With experience and a t t e n t i o n t o the c o l o u r v a r i a t i o n s , the s i t e g e o l o g i s t becomes adept a t a s s e s s i n g the grade o r o i l y i e l d of the o i l shale beds. Barren green c l a y s t o n e s , ranging i n t h i c k n e s s from a few m i l l i m e t r e s t o s e v e r a l metres i n the o i l shale seams, reach a notable t h i c k n e s s i n the Telegraph Creek u n i t l o c a t e d towards the top of the Rundle Formation. Nevertheless the formation c o n s i s t s predominantly of o i l shale and the h i g h e s t grade seams are contained i n the upper 320m of the formation. The shale o i l average y i e l d f o r the Rundle o i l shales i s 99 LTOW and 94 LTOW f o r those i n the S t u a r t d e p o s i t . Average moisture i n t h i s formation i s 20% by weight and in situ b u l k d e n s i t y 1.^5 g/cc. The measured in situ resource i n the graben i s 5.16x10 b a r r e l s of shale o i l . F o s s i l remains are widespread i n the formation; most common are ostracods which add a d i s t i n c t l y calcareous content t o some beds. A t h i n - s h e l l e d , l o w - h e l i c a l gastropod i s a l s o common, o c c u r r i n g both i n o i l shales and barren beds. I n



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a d d i t i o n , fragments of v e r t e b r a t e forms ( r e p t i l i a n and piscean) and Crustacea, have been logged i n d r i l l core. From the f a u n a l and f l o r a l assemblage the Rundle Formation i s e a r l y T e r t i a r y (mid to l a t e Eocene) i n age. Dark brown to b l a c k carbonaceous l a y e r s occur i n the B r i c k K i l n and Kerosene Creek seams and p e r s i s t over considerable d i s t a n c e s . One such u n i t i s so p e r s i s t e n t throughout the graben (and i n a p o r t i o n c o n t a i n i n g s e v e r a l metres of l i g n i t e ) as to merit a separate u n i t c l a s s i f i c a t i o n (Humpy Creek seam). Sedimentary s t r u c t u r e s ( b r e c c i a s , c o l o u r g r a d i n g , slumping) are p r e v a l e n t and repeated macro-scale; recent d e t a i l e d mapping i n a cut opened i n the Ramsay Crossing seam to provide b u l k samples has revealed c y c l i c sedimentation over a frequency of a few metres ( 5 ) . T h i n , d i s c o n t i n u o u s , dense d o l o m i t i c limestone beds and lenses are present throughout the sequence. Immediately o v e r l y i n g the Kerosene Creek seam at the top of the Rundle Formation, i s another t h i c k e r carbonaceous shale w i t h a s s o c i a t e d l i g n i t e , having a low o i l y i e l d . This passes upwards i n t o claystones and sandy claystones w i t h o x i d a t i o n c o l o u r s ; the whole i s named the Curlew Formation. The Narrows Graben has s t r u c t u r a l asymmetry w i t h a r e g i o n a l dip of the sequence from 4 to 10 degrees to the west. The youngest u n i t s are only present along the western margin of the b a s i n and p r o g r e s s i v e l y o l d e r beds subcrop beneath the s o i l cover and c o l l u v i a l outwash towards the east. While both margins of the graben are f a u l t d e f i n e d , the g r e a t e r movement has occurred along the western boundary f a u l t . Drag and s u b s i d i a r y f a u l t i n g i n t o the main western boundary f a u l t has a f f e c t e d the shale sequence f o r tens and hundreds of metres along t h i s f l a n k . Some f a u l t i n g transverse across the grabens has occurred; such f a u l t i n g a s s o c i a t e d w i t h a p o s s i b l e basement h i g h , b r i n g s the o l d e r , lower grade u n i t s to the s u r f a c e , and separates the Rundle and S t u a r t deposits i n t o two d i s t i n c t lobes. An a l k a l i n e d o l e r i t e has i n t r u d e d the lower p o r t i o n of the Rundle Formation at d i f f e r e n t s t r a t i g r a p h i e l e v e l s i n the S t u a r t Deposit, thermally metamorphosing the invaded sequence f o r an average of 46m over an area of 2.25 sq. km. The age of the d o l e r i t e i s set at 26.8m.y. using the K/Ar method ( 4 ) . A s i l l of about 4m t h i c k n e s s a l s o occurs i n the Rundle d e p o s i t . The thermal e f f e c t has been to form and r e l o c a t e v o l a t i l e hydrocarbons and leave a non-reactive aromatic residue on the o i l shale adjacent to the i n t r u s i v e ( 6 ) . H i l l s b o r o u g h B a s i n . The b a s i n , defined g e o p h y s i c a l l y during a phase of o i l e x p l o r a t i o n during the 1960 s, l i e s l a r g e l y o f f s h o r e from Mackay. I t trends northwest towards P r o s e r p i n e , inshore from Repulse Bay, and covers an area of about 75 χ f



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15km. I t i s estimated t o c o n t a i n up t o 3000m o f s e c t i o n o f f s h o r e , whereas onshore a s t r a t i g r a p h i e t e s t l o c a t e d a x i a l l y i n the b a s i n , found middle P a l e o z o i c basement a t 1280m below a sequence of T e r t i a r y s h a l e s , mudstones, s i l t y sandstones and b a s a l v o l c a n i c agglomerate. Prospecting f o r o i l shale has been confined t o the western f l a n k of the onshore p o r t i o n of the b a s i n where v o l c a n o l i t h i c quartz a r e n i t e s and p e l i t e s u n d e r l i e the o i l s h a l e sequence ( 7 ) . The main o i l shale u n i t of the Condor d e p o s i t i s a remarkably monotonous, massive ( t o s l i g h t l y laminated) brown, kerogenous mudstone (brown oil shale unit). The u n i t ranges from 300-400m i n t h i c k n e s s , p e r s i s t i n g f o r a t l e a s t 15 km. along s t r i k e . About h a l f of the u n i t has an average y i e l d of 63 LTOW and c o n s t i t u t e s the main p o t e n t i a l economic zone of the d e p o s i t . Towards i t s base, the brown oil shale g r a d u a l l y becomes darker i n c o l o u r (brown-black oil.shale unit). This u n i t ranges from 10 - 50m i n t h i c k n e s s and i t s base i s marked by a sharp c o n t r a s t w i t h a h i g h ash l i g n i t e - carbonaceous shale (carbonaceous unit), which i n t u r n grades down i n t o the b a s a l sandstone. The carbonaceous unit has a high v o l a t i l e s content and assays up t o 135 LTOW have been recorded. O v e r l y i n g the brown oil shale unit are t h i n l y interbedded and laminated o i l shales and s i l t s t o n e s , the transitional unit. Above i t i s the youngest h o r i z o n (upper unit) o c c u r r i n g along the western f l a n k . This u n i t c o n s i s t s of c y c l i c sequences of v o l c a n o l i t h i c sandstones and s i l t s t o n e s w i t h interbedded laminae of o i l shale and mudstone. With the uniform and r e g u l a r d i p t o the n o r t h e a s t , ranging from 10 t o 14 degrees, the upper unit of the succession exceeds 500m i n t h i c k n e s s a t the downdip l i m i t t o which p r o s p e c t i n g has been c a r r i e d (5 km downdip f o r 15 km along s t r i k e ) . The s t r u c t u r e of the d e p o s i t , w i t h homoclinal northeast d i p , i s uncomplicated, although f a u l t i n g occurs. This appears to be l i m i t e d t o a s e t of s t r i k e - n o r m a l f a u l t s , d i p p i n g t o the northwest. The western margin of the b a s i n i s f a u l t e d ; the displacement i s probably of c o n s i d e r a b l e magnitude. The T e r t i a r y beds are masked by up to 30m of a l l u v i a l g r a v e l s and sands. The o i l shale of the Condor deposit i s a tough, more competent rock than the other T e r t i a r y o i l shales of Queensland and a l s o possesses a lower moisture content (9% moisture by w e i g h t ) . The brown oil shale unit contains s c a t t e r e d collophane nodules, commonly enclosed by marcasite and an outer p a l e r c a r b o n a t e - r i c h h a l o . Buddingtonite occurs p e r s i s t e n t l y i n the brown oil shale and younger u n i t s , comprising up t o 10% of the rock ( 8 ) . F o s s i l s are extremely r a r e i n ^ t h e Condor d e p o s i t . The measured in situ resource i s 8.45 χ 10 b a r r e l s of shale o i l . Duaringa B a s i n . I n c o n t r a s t t o the other d e p o s i t s , the T e r t i a r y sequence i n the Duaringa B a s i n has p o s i t i v e r e l i e f ,


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standing as three remnant, steep-sided t a b l e l a n d s separated by water gaps. The t a b l e l a n d s are up t o 100m above surrounding l o w - l y i n g country which i s u n d e r l a i n by Permian sedimentary rocks o f the Bowen B a s i n . Although some i n d i c a t i o n s of o i l shale had been reported many years ago, nothing was known o f i t s extent across the expanse of the b a s i n , 180 km χ 25 km. Geophysical surveys i n the I 9 6 0 s i n d i c a t e d the p o s s i b i l i t y o f 1200 metres o f T e r t i a r y rocks. "Fence l i n e " d r i l l holes across the b a s i n i n 1978-79 revealed that o i l shale occurs above the base o f the t a b l e l a n d s and although s t r u c t u r a l l y uncomplicated and continuous, i s r e l a t i v e l y t h i n . There are two seams, an upper about 15m t h i c k , unit Ό, separated from the lower 25m seam, unit B, by a 20m barren zone. Beds of o i l shale a l s o occur deeper (at about 250m below the surface) i n the b a s i n . Subsequent s t r a t i g r a p h i e core holes d r i l l e d by the G e o l o g i c a l Survey of Queensland (Duaringa 1-2R and 3/3A), proved presence o f more than 1200m of sedimentary rocks. Most o f t h i s i s b i o t u r b a t e d s i l t y and sandy o x i d i s e d claystones w i t h some o i l shale below 600m u n d e r l a i n by more than 80m of b a s a l t (Noon, pers. comm.). B a s a l t i c l a v a s a l s o occur interbedded w i t h the shallow o i l shale l a y e r s i n the southern end of the b a s i n . A d i s t i n c t i v e and u b i q u i t o u s marker bed of centimetres t h i c k n e s s c h a r a c t e r i s e d by abundant g r a i n s of s a n i d i n e has been found a t the base of u n i t Β o i l s h a l e . Diatomite and b a r i t e are a s s o c i a t e d w i t h the o i l shale a t the northern end of the b a s i n . Phosphate m i n e r a l s , i n c l u d i n g blue v i v i a n i t e i n s m a l l amounts a r e present i n u n i t Β. The Duaringa t a b l e l a n d s have a deep s o i l and weathering p r o f i l e ranging from 40 t o 60m, which has a f f e c t e d much of u n i t D as w e l l as unit Β where topographic r e l i e f i s not so ^ pronounced. Units Β and D are estimated t o c o n t a i n 3.72 χ 10 b a r r e l s of shale o i l .


1

B y f i e l d . A t B y f i e l d o i l shale i s contained i n a s m a l l graben 2km wide f o r about 5km along the western f l a n k of the Water Park Creek B a s i n . Two o i l shale u n i t s (TW2, TW4) o v e r l i e carbonaceous and pale coloured claystones and sandstones ( u n i t TW1). Units TW2, TW4 are separated by about 120m of kerogen-bearing mudstone (unit TW3). Unit TW2 i s 120m t h i c k of which 50m has an average grade o f 58 LTOW w i t h a low (9.5%) moisture and has s u p e r f i c i a l s i m i l a r i t i e s t o the brown oil shale a t Condor. A t the top of sequence u n i t TW4 (up t o 110m) c o n s i s t s of dark brown t o b l a c k carbonaceous shale - l i g n i t i c c o a l , w i t h interbedded sandstone and s i l t s t o n e . The shale o i l y i e l d i s r e l a t i v e l y high (up t o 100 LTOW) but averages 77 LTOW for a net 50m. Some of the assay-produced o i l s c o n t a i n a t a r r y f r a c t i o n , w i t h a r e l a t i v e d e n s i t y > 1 . 0 a t 15.6/15.6 C. There i s i n s u f f i c i e n t d r i l l hole c o n t r o l t o c a l c u l a t e the o i l shale resource a t B y f i e l d ; i t i s probably s m a l l , w i t h not more than 250x106 b a r r e l s of shale o i l . Q


106


Composition of the O i l Shales Maceral terminology f o r o i l shales was modified by Hutton e t a i . (9) when t h e i r study of these rocks pointed out a d i s t i n c t i o n between h i g h grade o i l shales (such as t o r b a n i t e and k u k e r s i t e both of which are t y p i f i e d by accumulations of d i s c r e t e rounded a l g a l bodies) and Queensland T e r t i a r y o i l shales ( t y p i f i e d by f i n e l y banded l a m e l l a r a l g i n i t e i n i n t i m a t e a s s o c i a t i o n w i t h m i n e r a l m a t t e r ) . They termed the d i s c r e t e rounded a l g i n i t e ' A l g i n i t e A' and the l a m e l l a r alginite 'Alginite B . Green algae were b e l i e v e d to be precursors of a l g i n i t e A and both green and blue-green algae to be precursors of a l g i n i t e B, w i t h both forms producing Type I kerogen (10). For o i l shales i n which l a m e l l a r a l g i n i t e i s the dominant organic e n t i t y , Hutton e t a i . proposed the term l a m o s i t e . Using the form of organic matter as a b a s i s f o r c a t e g o r i s i n g types of o i l s h a l e , Cook e t a i . (11) concluded that lamosites are of lacustrine origin. The Queensland T e r t i a r y lamosites are h i g h i n moisture w i t h an organic carbon content r a r e l y exceeding 20% by weight. P y r i t e i s u s u a l l y present i n t r a c e q u a n t i t i e s . An a s s o c i a t i o n of s i l t - a n d c l a y - s i z e d s i l i c a and s i l i c a t e - r i c h minerals dominates the i n o r g a n i c c o n s t i t u e n t s . However, g e n e r a l i s a t i o n s have to be kept i n p e r s p e c t i v e . For example, assaying of the o i l shales has been c o n s i s t e n t l y c a r r i e d out over two metre i n t e r v a l s . Over t h i s i n t e r v a l , the organic carbon content r a r e l y exceeds 20%, but over centimetres w i t h i n t h i s i n t e r v a l , the range may vary enormously. (A. Hutton, pers. comm., has recorded a 20 cm i n t e r v a l from a core through the Kerosene Creek seam at S t u a r t w i t h 85% a l g i n i t e c o n t e n t ) . Thus, d i s t i n c t i v e grade p a t t e r n s over m u l t i p l e s of the two metre assay i n t e r v a l commonly p e r s i s t throughout the preserved a r e a l dimension of a d e p o s i t , c o i n c i d e n t w i t h other l i t h o l o g i e characters of the rock. The seam c l a s s i f i c a t i o n at Rundle a p p l i e s a l s o at S t u a r t , throughout the 28 km l e n g t h of The Narrows Graben (Figure 4 ) . L i k e w i s e the 10 and 20m t h i c k seams (units D and B) at Duaringa p e r s i s t over a d i s t a n c e of 130 km i n the e r o s i o n a l remnants i n t h a t b a s i n ; and v e r t i c a l grade changes through the 300m t h i c k brown oil shale unit a t Condor p e r s i s t f o r at l e a s t 15 km along s t r i k e .


1

Mineralogy. The d i s t r i b u t i o n of the major elements (expressed as oxides) i n the main o i l shale seams i n three b a s i n s (The Narrows Graben, Duaringa and H i l l s b o r o u g h Basins) are l i s t e d i n Table I . The most apparent v a r i a t i o n s are i n the i n o r g a n i c components of the carbonaceous u n i t s (Humpy Creek seam i n the Narrows Graben; brown-black oil shale and



Figure 4. Oil yield histogram correlation of The Narrows Graben. (Reproduced with permission from Ref. 4. Copyright 1982, American Association of Petroleum Geologists.)


^1

ο


Kerosene Ck. Munduran Ck. Humpy Ck. Brick Kiln Ramsay Crossing Teningie Ck. Unit Β Brown o i l shale Brown-black o i l shale Carbonaceous unit

Seam

No. of Analyses

*O.S. C/C.S L,M,H,O.S

4 O.S O.S 3 C/C.S 3 O.S. 14 O.S 9 L.O.S. 3 L,M,H,O.S 3 O.S 18 L.O.S 3 4 C/C.S

fN

CM

0.6 0.7 0.6 0.8 0.8 1.0 0.8 0.9 1.3 1.4

h>

•ri

Ο

CM

16.1 16.6 12.7 16.3 16.0 18.3 19.0 17.3 24.6 30.7

20%),



6. LINDNER

XX

XX

x/xx

X

XX

XX

XX

x/xx

XX

XX

x/xx

XX

X

XX

XX

X

x/xx

XX

x/xx

XX

xx/xxx

x/xx

xx/xxx

x/xx

x/xx

xx/xxx

XXX

X

X

XX

xxx/ xxxx

X

XX

XX

xx/xxx

X

x/xx

XX

xx/xxx

χ

χ/χχ

χ

X

χ

χ χ/χχ

χ/χχ

X

χ

X

κ

X

ω (Λ

ΑΝΑΤί

x/xx x/xx

w HALI*]

1

ALUN][TE

tu >· C5

X

X

;ΙΤΕ

PYRI1

ω Mg )

ο

CALCI:TE (SUBS•TITUTED

:TE

ω CALC] SIDEF

SI DEIUTE

BUDD]CNGTONITE

FELDSPAR

KAOL:[NITE

MICA,/ILLITE


THE STUART, DUARINGA, BYFIELD AND CONDOR DEPOSITS

χ

Χ

χ χ

X

XXX

χ

χ

X

XXX

xxxx

XX

XX

XX

xxxxx

X

xxxxx

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X

XX

X

XX XX

X?

X?

xx Accessory (5-20%), χ Trace (< 5%). uulk mineralogy determined by Amdel; except for Byfield, Duaringa A determined by Commonwealth and Industrial Research Organisation (CSIRO) Division of F o s s i l Fuels.


112



s i n c e 1974 on composite samples of F i s c h e r assay spent shale through the o i l shale sequence i n the Queensland d e p o s i t s . Over s e l e c t e d i n t e r v a l s , s i m i l a r analyses have been made on f r e s h s h a l e . These have not revealed any c o n c e n t r a t i o n of metals i n anomalous amounts, even though the provenance f o r the d i f f e r e n t b a s i n s ranges from sedimentary through igneous and metamorphic sequences. L i m i t e d q u a n t i t a t i v e analyses on f r e s h s h a l e from Condor (brown oil shale), and S t u a r t ( B r i c k K i l n and Ramsay Crossing seams) confirm the e a r l i e r q u a l i t a t i v e assessment of d i s t r i b u t i o n . Kerogens. I n the course of c h a r a c t e r i s a t i o n work, a number of kerogen samples have been i s o l a t e d from d i f f e r e n t seams i n the v a r i o u s d e p o s i t s . T h e i r elemental composition (on a m i n e r a l f r e e b a s i s ) i s l i s t e d i n Table I I I and atomic r a t i o s p l o t t e d i n a Van K r e v e l e n diagram (Figure 5 ) . The diagram demonstrates the p e r s i s t e n c e of Type I kerogen i n the lamosites from the Queensland T e r t i a r y d e p o s i t s w i t h the suggestion that Condor kerogens may d i f f e r from t h i s g e n e r a l i s a t i o n . Two of the f i v e kerogens from the Condor brown oil shale show an u n u s u a l l y h i g h 0/C atomic r a t i o . The other kerogens from t h i s u n i t appear to be i n t e r m e d i a t e between the Type I and I I . The carbonaceous u n i t s (at Condor, B y f i e l d ; Humpy Creek seam at Rundle and S t u a r t ) c h a r a c t e r i s t i c a l l y f a l l i n t o Type I I I kerogens i m p l y i n g both a lower a l g a l content and the presence of h i g h e r p l a n t m a t e r i a l . Thermogravimetric a n a l y s i s confirms t h i s d i s t i n c t i o n i n kerogen composition. Type I m a t e r i a l r e l e a s e s most of i t s v o l a t i l e matter below 500°; Type I I I carbonaceous kerogens g i v e p r o p o r t i o n a l l y more above 500 C (Saxby p e r s . comm.). Higher maturation f o r the Condor Type I I I sample i s apparent, from r e f l e c t a n c e values obtained on v i t r i n i t e from t h i s u n i t (Hutton, pers. comm.). M a t u r a t i o n due to g r e a t e r b u r i a l might a l s o be assumed from the p o s i t i o n i n the diagram of Type I Condor and some o l d e r kerogens (Ramsay C r o s s i n g and B r i c k K i l n ) i n The Narrows Graben. Table I I I i n c l u d e s analyses of kerogen i s o l a t e s and d e r i v e d shale o i l . For the o i l s , the H/C atomic r a t i o s are h i g h e r than f o r the parent kerogens. This i s c o n s i s t e n t w i t h the o i l s being d e r i v e d p r i m a r i l y from the a l g a l component of the o i l s h a l e s . The o i l s d e r i v e d from the carbonaceous u n i t s d i f f e r from those d e r i v e d from l a m o s i t e s . The carbonaceous u n i t s y i e l d o i l w i t h a h i g h e r heteroatom c o n t e n t , i n d i c a t i n g presence of v i t r i n i t e or kerogen sourced from h i g h e r forms of p l a n t l i f e . A lower o i l y i e l d per u n i t kerogen content as observed by Eckstrom e t a l . (12) supports a h i g h l y condensed o r g a n i c r i n g s t r u c t u r e f o r the carbonaceous u n i t kerogen.



Ramsay Crossing

Brown Oil Shale

TW

TW

Unit

Unit

2

4

BYFIELD DEPOSIT

Unit A

Unit Β

DUARINGA DEPOSIT

Carbonaceous Oil Shale

Brownish-black Oil Shale

+

Χ

Ρ

STUART DEPOSIT

υ

ο

0&4

10+

154

0·Ι5

ΤΥΡΕΙ

0-20

Atomic Ratio 0/C

0·!θ

KEROGEN

0-25

Figure 5. Van Krevelen diagram of some Queensland Tertiary kerogens.

•

Brick Kiln

CONDOR DEPOSIT

•

Δ

Humpy Creek

Ο

ο

Mu η du ran Creek

Marker bed in Telegraph Creek unit

Kerosene Creek

RUNDLE DEPOSIT

THE NARROWS GRABEN

20


030


TABLE III. ELEMENTAL ANALYSES, KEROGENS

Deposit


RUNDLE

Unit

Kerosene Ck. O.S. Marker i n T e l e g r a p h Ck. Munduran Ck . Humpy Ck. Brick Kiln Brick K i l n Ramsay C r o s s i n g

STUART

Brick

BYFIELD

TW

TW

DUARINGA

CONDOR

STUART

DUARINGA CONDOR

Location

Kiln

2

Β

A Brown O i l Shale

Carbonaceous Brick Kiln

Β Brown O i l Shale Brown b l a c k Shale Carbonaceous

Auger sample 25m RDD31 RDD31 RDD43 RDD31 RDD25 RDD41 RDD41 RDD41 SDD51

110 .5m 80 . 5m 161 . Om 111 . Om 67 . 5m 85 . Om 99 .2m 50- 52m

Fischer

Assay

Yield

(LTOW)

High grade Low grade (

Geology and Geochemistry of Some Queensland Tertiary Oil Shales

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