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Energy & Fuels 1994,8, 1469-1477
1469
Liptinite in Indonesian Tertiary Coals
Adrian Hutton,* Bukin Daulay, Herudiyanto, Chairul Nas, Agus Pujobroto, and
Hakim Sutarwan
Department of Geology, University of Wollongong, Northfields Avenue,
Wollongong, N S W , 2522, Australia
Received July 6, 1994. Revised Manuscript Received September 6, 1994@
A comparison of the petrographic data for coals from various Indonesian Tertiary basins shows
that the coals have similar compositions with vitrinite the dominant maceral group. A feature
common t o most of the coals is the abundance of secondary liptinite, especially exsudatinite but
also fluorinite. The association of exsudatinite with oil, adjacent to, or within liptinite and vitrinite
macerals, suggests that exsudatinite is an indicator of oil generation, but at an early stage.
Exsudatinite is probably an intermediate product in the pathway vitrinitehptinite oil. Organic
matter referable to exsudatinite andor bitumen is found in coals and clastic rocks from eastern
Kalimantan. The petrographic properties of both are the same. It is suggested that, for
consistency of terminology, where this material is found in coal it should be termed exsudatinite
whereas where it is found in other rocks it should be termed bitumen.
-
Introduction
The Indonesian Archipelago formed through the
evolution and convergence of the northward-moving
Indian-Australian Plate, the westward-moving Pacific
Plate and the relatively stationary Eurasian Plate.1-4
Subduction of the Indian-Australian Plate beneath the
Eurasian Plate lead to the development of a major
magmatic arc system which is divided into two segments, the Sunda Arc in the west, and the Banda Arc
in the east. These arcs are associated with a series of
subduction zones which migrated, with time, in response to changes in the tectonic setting of the Indonesian region, resulting in the formation of intramontane (Early Tertiary), foreland (Late Tertiary), and
interarc (Late Tertiary) basins. Deposition of peat
occurred during pretransgressive stages in the intramontane basins and during a late regressive stage in
the foreland and interarc basins.
The most significant coal deposits, in Sumatera and
eastern Kalimantan (Figure l), are a major part of
Indonesia’s energy resources. Indonesia is rapidly
developing policies that will ensure equitable domestic
use of energy resources but a t the same time provide
substantial income from export commodities such as
coal and petroleum. Utilization of the coal resources,
both on the domestic and export markets, depends on a
thorough knowledge of the properties of the coal.
Indonesia’s petroleum resources are large by AsianPacific standards but many companies are still actively
exploring for new resources to augment the existing
reserves. For both the coal and petroleum scenarios,
organic petrography will become an increasingly useful
technique because it is one of the few techniques that
quantitatively characterizes organic-rich rocks. Because of the relatively recent exploitation of Indonesian
~~
coals on the world markets, the traditional benefits of
organic petrography for coal quality determination are
yet to be fully utilized. Realization that coal-bearing
sequences are source rocks for petroleum generation has
placed an added incentive for using organic petrography.
Continued exploration for petroleum will utilize organic
petrography both for typing source rocks and geothermal modeling, where vitrinite reflectance is the most
commonly-used maturation parameter.
In this paper, data on the composition of coals and
associated organic-bearing clastic sedimentary rocks
from eastern Kalimantan are compared with data for
coals from Sumatera and several other Indonesian
basins. The abundance of secondary liptinite macerals
is a common feature of many Indonesian Tertiary coals,
and this begs a discussion of the implication of these
macerals as indicators of oil generation and/or as
intermediates in petroleum generation. It is now generally accepted that coals may serve as source rocks under
some circumstances but several problems have remained unresolved. Is there available porosity to allow
migration of oil through coal t o the reservoir rocks? Are
liptinite macerals, especially exsudatinite, indicators of
petroleum generation? If so, are they indicators of
limited early oil generation or oil generation on a much
larger scale, sufficient to permit migratable amounts of
oil.
Given the relative abundance of secondary liptinite
macerals, comment is made on the suitability of presently-accepted liptinite maceral terminology.
Eastern Kalimantan Coals
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@Abstractpublished in Advance ACS Abstracts, October 1, 1994.
(1)Hamilton, W. US.Geol. Sum., Profess. Pap. 1979,1078.
(2) Katili, J. A. Tectonophysics 1973,19, 195-212.
(3) Katili, J. A. Tectonophysics 1978,45, 2-14.
(4) CCOP-IOC. Studies in East Asian Tectonics and Resources
(SEATER), UNDPICCOP, Bangkok, 1980.
0887-0624/94/2508-1469$04.50/0
Economic coal deposits in eastern Kalimantan occur
in the Tertiary Tarakan, Kutei, Barito, and Asem Asem
Basins (Figure 2) which formed as a result of rifting
along, or close to, the eastern edge of the Kalimantan
continental block. Barito Basin and Asem Asem Basin
coals were deposited in retro-arc settings close to the
foreland whereas the Kutei Basin and Tarakan Basin
coals formed along the rifted border of eastern Kali-
0 1994 American Chemical Society
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1470 Energy & Fuels, Vol. 8, No. 6, 1994
Hutton et al.
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Figure 1. Coal basins in Indonesia.
mantan. The coal measures sequences of Eocene and
Miocene age were deposited in environments ranging
from fluvial to deltaic.
The thickness of the coal seams varies from a few
centimeters to 40 m with dips ranging between 5" and
25" near the surface. Typically the Miocene coals are
thicker than the Eocene coals. Variations in thickness
are associated with splitting (particularly in Eocene
coals), wash-outs and wedge-outs. Splitting was probably caused by channel activity at the time of peat
accumulation.
Organic Petrography
In hand specimen, coals from eastern Kalimantan are
composed dominantly of clarain and vitrain lithotypes.
Inertinite-rich dull layers are very rare but are more
common in Miocene coals, particularly those from Mahakam and Sangatta, than in the Eocene coals. The
vitrinite-rich bright layers were derived from peat that
accumulated under water, in more reducing conditions
than were present for the inertinite-rich, dull layers
which were probably derived from peat that was exposed to an oxidizing atmosphere above the water table.
Maceral terminology used in this paper is that of the
Australian Standard for Maceral A n a l y ~ i s . ~
Vitrinite Reflectance. The rank of coals from
eastern Kalimantan generally spans the range of 0.3
to 0.6% vitrinite reflectance (Table 11, that is, from soft
brown coal to high-volatile bituminous ranks, with
thermally-altered coals from Sangatta reaching semianthracite rank (up to 2.03% vitrinite R,max).
Four groups are recognized: (1)Miocene, soft brown
to subbituminous coals subjected to regional coalification in areas with geothermal gradients normal for the
Indonesian islands; mean maximum reflectance (R,max)
values of 0.30-0.55%; (2) Miocene, subbituminous to
low-volatile bituminous coals subjected to regional coali(5) Standards Association of Australia, Standard, AS 2856, 1986.
fication in areas (characterized by strongly folded strata)
where geothermal gradients were above those normally
expected for the Indonesian islands; Rvmax values are
0.48-0.71%; these coals are restricted to the Sangatta
area where there is a relatively high geothermal gradient, related to intrusions, that has not previously been
reported; (3) Miocene, semianthracitic coals affected by
contact thermal metamorphism; Rvmaxvalues of 1.602.03%; and (4)Eocene, brown to low-volatile bituminous
coals subjected to regional coalification in areas with
geothermal gradients normal for the Indonesian islands;
RvmaX values of 0.43-0.66%; these coals were buried
to greater depths than the Miocene coals.
Although vitrinite reflectance of coals increases with
depth in deep drill holes, no significant general trend
was found within any single coal seam, except in the
Berau and Senakin coals where vitrinite reflectance
exhibits an increase from the top to the bottom of the
seam. These changes are assumed to be related t o
differences in vitrinite type.
Maceral Composition. Vitrite and clarite are the
dominant microlithotypes, with subordinate vitrinertite
(both vitrinite- and inertinite-rich microlithotypes),
duroclarite, and inertite. In some of the Mahakam,
Tanjung, and Sangatta coals, vitrite and vitrinertite are
dominant.
Vitrinite. Petrographically, vitrinite is the dominant
maceral, both in Miocene and Eocene coals, with the
vitrinite content of Miocene coals (range of 63.5-98.0%,
average of 82.9%; Table 2) slightly higher than for
Eocene coals (range of 61.9-93.9%, average of 79.4%).
Vitrinite consists predominantly of telovitrinite and
detrovitrinite with gelovitrinite content invariably low.
Telovitrinite, ranging from 0.04 to 0.20 mm in thickness, consists predominantly of textinite, texto-ulminite,
eu-ulminite, and lesser telocollinite. Thin layers of
telovitrinite are generally surrounded by a thick detro-
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Energy & Fuels, Vol. 8, No. 6, 1994 1471
Liptinite in Indonesian Tertiary Coals
’-*
SANGATTA
\
T
v)
v)
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T
200KM
LEGEND
PLIOCENE COAL
MIOCENE COAL
EOCENE COAL
Figure 2. Coal basins in eastern Kalimantan with resources.
vitrinite groundmass but some telovitrinite bands are
interbedded with detrovitrinite.
Attrinite and densinite are the most common detrovitrinite macerals with desmocollinite a minor component. Sparse to abundant gelovitrinite is disseminated
throughout the telovitrinite and detrovitrinite with
porigelinite occurring as thin bands within telovitrinite.
Znertinite. Inertinite content is generally very low and
is more abundant in Miocene coals (average of 4.2%)
compared to Eocene coals (average of 2.2%). Dominant
macerals are semifusinite, sclerotinite, and inertodetrinite with minor fusinite, micrinite, and macrinite.
Semifusinite commonly occurs as layers (up to 1.0 mm
in length), lenses, or isolated fragments, generally
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1472 Energy & Fuels, Vol. 8, No. 6, 1994
Hutton et al.
Table 1. Reflectance Data for Eastern Kalimantan Coals
gelovitrinitel
detrovitrinite
R,max
range
telovitrinite
R,max
range
Miocene
Berau
Sangatta
a
Mahakam
Asem Asem
Tanjung
Eocene
Tanjung
Pasir
Satui
Senakin
mean
R,max
0.45
0.64
1.88
0.48
0.36
0.61
0.39-0.55
0.49-0.72
1.61-2.03
0.40-0.55
0.30-0.41
0.57-0.65
0.44
0.62
1.81
0.46
0.35
0.39
0.37-0.54
0.47-0.69
1.55-2.06
0.37-0.54
0.29-0.41
0.33-0.47
0.45
0.63
1.87
0.47
0.36
0.40
0.61
0.63
0.51
0.57
0.57-0.65
0.58-0.67
0.44-0.54
0.54-0.64
0.59
0.61
0.50
0.56
0.54-0.63
0.57-0.65
0.42-0.53
0.50-0.63
0.60
0.62
0.50
0.56
Thermally altered coals.
Table 2. Petrographic Data for Eastern Kalimantan
Coalsa
vitrinite
Miocene
Beru
Sangatta
Mahakam
Tanjung
Asem
Asem
Eocene
Pasir
Tanjung
Satui
Senakin
a
inertinite
liptinite
range
mean
range
mean
range
mean
73.2-95.1
63.7-95.8
64.3-98.0
77.2-87.4
63.5-94.2
82.0
85.9
82.1
82.5
82.0
0.6-13.7
0.2-12.1
0.6-31.3
2.8-6.4
0.2-9.9
3.6 1.7-18.4
4.8 0.2-11.2
9.1 0.2-25.9
4.5 6.2-13.2
3.4 0.8-30.9
10.2
5.6
9.1
9.3
10.7
75.3-86.1
79.3-85.9
61.9-90.7
69.6-93.9
80.8
78.3
77.3
81.3
0.6-3.7
0.9-4.2
0.5-5.7
0.2-6.1
2.0
2.5
2.3
2.1
3.3-15.5
5.6-19.3
4.8-33.3
1.4-18.0
9.4
13.2
15.5
8.3
Mineral matter not included in the table
Table 3. Petrographic Data for Other Indonesian Coals
(Data from Various References Cited in Text)
maceral composition
vitrinite inertinite liptinite
Sumatera
Perapnap
West Aceh
Pliocene
Miocene
Oligocene
Meulaboh
Neogene
Paleogene
Ombilin
Banko Barat
Bukit Assam
Java
Bayah
Bojongmanik
reflectance
(range)
90-92
1-2
6-7
44-94
60-98
64-92
0-11
0-22
0-24
7-50
2-29
6-26
50-95
70-90
83-94
80-90
70-95
0-7
1-5
0-4
1-5
0-7
10-50
8-20
1-14
3-20
2-15
0.20-0.40
0.45-0.70
0.70-0.80
0.30-0.55
0.30-0.50
71-93
81-91
0-3
0-3
2-15
2-18
0.53-0.83
0.30-0.40
associated with vitrinite (mainly telovitrinite); in some
cases, cell lumen of semifusinite are filled with either
resinite, fluorinite, or mineral matter.
Some of the Miocene Mahakam coals contain anomalously high percentages of inertinite (31.3 and 18.3%,
respectively). These coals probably formed in areas with
more oxidizing conditions, possibly caused by a lowering
of the water table during peat formation, resulting in
more frequent exposure to the atmosphere.
Inertodetrinite is commonly associated with vitrinite
and semifusinite. Sclerotinite, consisting of unilocular
and bilocular teleutospores and sclerotia, is generally
scattered throughout the samples.
Lzptinzte. Liptinite is abundant in all coals (Figure
3) with the exception of thermally-affected coals from
Sangatta. (In the Sangatta coals, liptinite is not easy
to recognize because of the high rank.) Liptinite
contents average 11.6% which is typically higher than
for the Miocene coals where the average of 9.0%. These
differences are thought to represent differences in the
floral assemblages at the time of peat formation of the
respective coals.
Resinite, suberinite, cutinite, sporinite, and liptodetrinite are the most abundant liptinite macerals, both
in Eocene and Miocene coals, constituting 7 0 4 0 % of
all liptinite in most samples. Resinite has bright
greenish-yellow to dull orange fluorescence. It occurs
as discrete bodies and lenses with some occurring as
diffuse cell fillings in telovitrinite.
Suberinite commonly occurs as distinct layers (0.050.40 mm thick) with greenish-yellow to orange fluorescence, although in some of the Sangatta coals the
fluorescence is very weak brown or absent. Cell walls
of weakly fluorescing suberinite are thinner than the
more strongly fluorescing suberinite. Suberinite commonly occurs in association with corpogelinite, rarely
with resinite and exsudatinite, and is more abundant
in Miocene coals, particularly in coals with lower
vitrinite reflectance.
Liptodetrinite is rare to abundant in most samples
and mainly occurs in clarite where it has greenishyellow to orange fluorescence. Large fragments of
liptinitic material (typically > 7 ,um diameter) in some
of the Berau and Asem Asem coals are included as
liptodetrinite maceral because they cannot be assigned
to any other maceral.
Rare t o abundant cutinite commonly occurs in association with vitrinite and resinite but in some cases
it is associated with suberinite and exsudatinite. It
generally has greenish-yellow to orange fluorescence,
although some has very weak brown or no fluorescence,
particularly in the Sangatta coals.
Sporinite (including crassispores, pollen, and sporangia) has greenish-yellow to orange fluorescence and is
less abundant in Miocene coals than in Eocene coals. It
commonly occurs in association with detrovitrinite,
resinite, and suberinite. The distinction between pieces
of thick suberinite and sporinite within a single sample
is difficult in some cases although the sporinite generally has yellow to orange fluorescence whereas suberinite fluoresces greenish-yellow to yellow.
Exsudatinite, the secondary liptinite maceral that is
derived from other liptinite and vitrinite and which
infills fractures and pores in coal, is abundant in many
samples and constitutes up to 10% of some samples. It
occurs in most coals and commonly has bright greenishyellow to orange fluorescence. It has various shapes and
occurrences including infillings in fractures, bedding
plane cavities, and cell lumens.
Fluorinite and Botryococcus-related telalginite are
minor components and rarely exceed 1%of the bulk
rock. Fluorinite is rare to abundant in some coals and
typically occurs as isolated bodies and lenses with bright
green to greenish-yellow fluorescence of very strong
intensity. Botryococcus-related telalginite with bright
yellow to orange fluorescence occurs in Miocene Satui,
Senakin, and Tanjung coals and in a few samples of the
Berau coal. Telalginite is commonly disseminated
throughout the samples although some concentrations
are present. Maximum percentages of the Botryococcus-
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Energy & Fuels, Vol. 8, No. 6, 1994 1473
Liptinite in Indonesian Tertiary Coals
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Figure 3. Fluorescence mode except where stated; field width = 0.34 mm. (1) Exsudatinite, infilling fracture, and sclerotinite in
coal composed of vitrinite (black), cutinite, and minor sporinite and liptodetrinite. (2) Same field as (l), reflected white light.
Nonfluorescing macerals are vitrinite and unilocular sclerotinite. Oil smear on vitrinite (right of field) escaping from fracture. (3)
Exsudatinite infilling fracture in vitrinite enclosed in cutinite; resin bodies also present; close association of exsudatinite with
cutinite suggests exsudatinite is derived from cutinite. (4)Exsudatinite infilling fracture between two layers of suberinite; clearly
exsudatinite is sourced from the suberinite. (5) Exsudatinite in vitrinite, with oil flowing from the exsudatinite, suggesting close
association between oil and exsudatinite. (6) Exsudatinite infilling fractures adjacent to resinite; exsudatinite unequivocally formed
from resinite.
related telalginite is 0.4%. Telalginite is also reported
in Eocene coals from Ombilin6y7and coals from Melawi
and Ketungau Basins8 and North Sumatera Basin.g
Mineral matter (mainly clay minerals, quartz, pyrite,
and carbonate) is sparse to common.
Oil and Oil-Related Substances. Coal is a sedimentary rock comprising organic matter, originally
deposited as plant fragments, which was converted by
biogenic and physicochemical alteration. This implies
that coal is solid in the same manner as other sedimentary rocks. However, coal bed methane desorption
experiments and organic petrography show that coal
contains components not regarded as macerals, inchd-
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(6) Daulay, B. Petrology of Some Indonesian and Australian Tertiary
Coals. M.Sc. (Hons) Thesis, The University of Wollongong, Wollongong,
1985 (unpublished).
(7) Daulay, B.; Cook, A. C. J. Southeast Asian Earth Sei. 1988, 5 ,
45-64.
(8) Sutjipto, R. H. Sedimentology of the Melawi and Ketungau
Basins, West Kalimantan, Indonesia. Ph.D. Thesis, The University of
Wollongong, Wollongong, 1991 (unpublished).
(9) Hadiyanto. Organic petrology and geochemistry of the Tertiary
formations at Meulaboh area, West Aceh Basin, Sumatera, Indonesia.
Ph.D. Thesis, The University of Wollongong, Wollongong, 1992 (unpublished).
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1474 Energy & Fuels, Vol. 8, No. 6, 1994
ing gases such as methane and carbon dioxide and liquid
components referred to by various names such as oil,
oil droplets, oil hazes, and oil smears. These “nonsolid
components may have been formed from the coal or have
migrated into the coal. Definitions of these and other
organic matter are as follows.
Hydrocarbons: used in a chemical sense in that the
material is composed of predominantly carbon and
hydrogen; oil and methane are examples.
Petroleum: naturally-formed liquid and gaseous hydrocarbons.
0il:liquid hydrocarbon derived from components of
the rock in which it occurs o r that has migrated into
one rock from another source rock; oil infills cavities in
coal as well other rocks; under the microscope oil may
occur as an (a) oil haze: fluorescing cloud emanating
from oil and dissolving in the immersion oil where this
is used; (b) oil smear, oil stain: fluorescing or nonfluorescing stain on the surface of the sample; commonly
brown in reflected white light; (c) oil drop, oil droplet,
free oil: oil occurring in fractures and cell cavities or
as drops on the surface or edges of grains.
Bitumen: solid hydrocarbon residues occupying fractures and other cavities; as will be discussed in detail
later, bitumen is equivalent to the maceral exsudatinite
and should be regarded as a secondary maceral; the
term bitumen is used in a petrographic sense not a
chemical sense.
Comparison with Other Coals. The maceral compositions and rank of coals from other Indonesian basins
are similar to those from eastern Kalimantan. Many
Indonesian coals, apart from being vitrinite-rich, have
low ash contents. These features of coals have been
interpreted as indicating a high moor origin.lOJ1
Coal type, or the petrographic composition of coal, is
related to paleoclimate, geological age, and tectonic
setting. The tectonic setting also plays an important
role in any subsequent burial metamorphism. As a
result of these factors, spatial and temporal variations
in paleoclimate, geological age, and tectonic setting can
cause variations in coal type or coal type provincialism.12
The range of plant components preserved in the peat
and the extent of alteration t o these components during
the diagenesis of the peat, and subsequent coalification,
determine coal type variations.13J4 Coals from eastern
Kalimantan are largely derived from ombrogenous peat
mires15J6which contained peats which were analogs of
the ombrotrophic peats described by C0u1ter.l~The
vegetation precursors of this type of peat is typically
tropical rainforest species dominated by angiosperms
(many of which were herbaceous), ferns and mosses that
developed in lowlands. Given the Indonesian coals are
Hutton et al.
all vitrinite-rich suggests that there is little coal type
provincialism in Indonesian coals.
Exsudatinite and Oil Generation
Is Coal a Source Rock? The role of coal as a source
rock for hydrocarbons has received increasing recognition over the past two decades. Numerous reservoirs
of significant size are associated with coal-bearing
sequences and in many instances, very few, if any,
clastic rocks with a marine origin are associated with
these sequences. The possibility of a marine source rock
for these sequences is unlikely unless the oil migrated
great distances. These types of reservoirs are found in
Australia, China, and Southeast Asia and this is now
taken t o be overwhelming evidence that hydrocarbons
are sourced from terrestrial matter in coal and that the
oil is expelled from the coal to reservoir rocks. Notwithstanding this, “The dispute such as it still exists
centers upon the question of expulsion, Le., whether the
oil, once formed, can escape from the coal into the
surrounding strata”.18
Hunt19stated that the high-wax, low-sulfur coals with
C29 steranes dominant and pristane to phytane ratios
usually above 5 indicated that the oils of the Gippsland
Basin of southeast Australia were derived from organic
matter deposited with terrigenous sediments. Hunt
argued that coal and terrestrial kerogen with either WC
ratios above 0.9, Rock-Eva1 hydrogen indices above
approximately 200 or liptinite contents of 15% or more,
have the potential to generate and release oil as well
as gas. Powell et a1.20confirmed that Australian coals
and terrestrial organic matter ranging in age from
Permian to Tertiary contain aliphatic structures capable
of producing paraffinic oils. These liptinite-poor coals
( < l o % liptinite) produced oil but of a type that has a
lower wax yield.
Of the three maceral groups, liptinite is considered
to have the greatest potential to produce hydrocarbons,
especially crude oi1.10~21~22
This concept was also suggested for a specific study on rocks thought to be the
source for the oils of the Ardjuna Basin, northwest Java.
In a study of the high-wax oils from that basin, Horsfield
et alSz3stated that the potential precursors were long
chain waxy paraffins in the coals of the Talang Akar
Formation. It was stated that the resinite and “related
macerals might play an especially important role in
petroleum expulsion”.
Large amounts of vitrinite, exsudatinite, and oil drops
and oil hazes in coal or carbonaceous shale are thought
to be indicators of hydrocarbon generation in these
rocks.24 If this hypothesis is accepted, Tertiary coals
from Indonesia are excellent source rocks providing the
oil is expelled to reservoirs.
Exsudatinite in Indonesian Coals. Exsudatinite
content of eastern Kalimantan coals ranges from (0.1
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(10) Smith, G. C; Cook, A.C. Fuel 1980,59,41-646.
(11)Titheridge, D. G. The geological and depositional setting of the
Brunner coal measures, New Zealand, and the influence of these factors
on seam thickness and petrological characteristics of Brunner coals.
Ph.D Thesis, The University of Wollongong, Wollongong, 1988 (unpublished).
(121 Cook, A. C. In Australian black coal - its occurrence, mining,
preparation and use; Cook, A. C., Ed.; Australasian Institute of Mining
and Metallurgy: Illawarra Branch, Australia 1975; pp 66-83.
(13) White, D. Bull. Acad. Sei. 1915,5,189-212.
(141 Smith, A. H. V. In Coal and coal-bearing strata; Murchison, D.
G., Westoll, T. S., Eds.; Oliver and Boyd: London, 1968; pp 31-40.
(151 Tennison-Woods, J. E. Nature 1885, 42, 113-116.
il6)Anderson, J. A. R. J . Trop. Geogr. 1964,18, 7-16.
(17)Coulter, J. K. Malay. Agric. J . 1957,40, 36-41.
(18) Levine, J. R. A m . Assoc. Pet. Geolog. Stud. Geol. Ser. 1993,3,
39-77.
(19) Hunt, J. Org. Geochem. 1991,17, 673-680.
(20) Powell, T. G.; Boreham, C. J.; Smyth, M.; Russell, N.; Cook, A.
C . Org. Geochem. 1991,17, 373-394.
(21) Snowdon, L. R.; Powell, T. G. Bull. Am. Assoc. Pet. Geol. 1982,
66,775-788.
(22)Tissot, B. P.; Welte D. H. Petroleum Formation and Occurrence;
Springer-Verlag: Berlin, 1984.
(23)Horsfield, B; Yordy, K. L; Crelling, J. C. Org. Geochem. 1987,
13, 121-129.
(24)Teichmuller, M.; Durand, B. Int. J . Coal Geol. 1983,2, 197230.
zy
zyxwvutsrqp
zyxwvutsrq
Energy & Fuels, Vol. 8, No. 6, 1994 1475
Liptinite in Indonesian Tertiary Coals
to 9.9% with an average of 0.8%;Miocene coals contain
relatively higher exsudatinite contents than Eocene
coals. In coals of both ages, exsudatinite normally
occurs adjacent to and within fractures in vitrinite and
liptinite (particularly resinite, cutinite, and suberinite,
Figure 3, parts 1-4, 6); by inference most, if not all, of
the exsudatinite originates from these macerals. Some
exsudatinite shows oil smearing and oil stains (Figure
3, part 5).
Exsudatinite in thermally-altered coal, referred to as
meta-exsudatinite to distinguish it from fluorescing
exsudatinite in lower rank coals, is present in some of
the Sangatta semianthracite which formed adjacent t o
an intrusion. In reflected white light, this metaexsudatinite has a higher reflectance than associated
macerals, including vitrinite, and does not fluoresce
which is assumed to indicate chemical alteration, specifically the loss of hydrogen. During coalification, the loss
of hydrogen is associated with the loss of volatile
hydrocarbons and water.
Reflectance of meta-exsudatinite is 2.70% whereas
that of the associated vitrinite is 1.74%,that of inertinite
1.58%, and that of liptinite 2.11%. Meta-exsudatinite
has also been recognized in anthracite found in Bukit
Asam, South Sumatera. In the anthracite, the reflectance of exsudatinite is also higher than that of the
associated vitrinite and inertinite. Meta-exsudatinite
in Bukit Asam is also formed during the thermal
alteration of high volatile bituminous brown coals
heated by intrusions.
In Indonesian coals, exsudatinite typically infills
veins, cell lumens, bedding planes and wedge-shaped
fractures, features also noted by M u r c h i ~ o nand
~ ~ Stach
et a1.26 It is also a binding agent for gelovitrinite in
some coals. From a review of early studies, Stach et
a1.Z6 noted that exsudatinite is mainly found in liptiniterich coals of subbituminous to high-volatile bituminous
rank. MurchisonZ5and ShibaokaZ7suggested that veinfilling secondary macerals (including exsudatinite) are
found in bituminous coals because they form as expulsions from other macerals, and subsequently migrate,
during the subbituminous stage. However, more recent
studies extended that range and exsudatinite now is
known to occur in coals of varying rank, ranging from
soft brown coal t o bituminous rank.
Earlier research shows exsudatinite may be directly
related to the formation of ~ i l . In~ low-rank
~ , ~ ~eastern
Kalimantan coals (for example, Asem Asem and Berau
coals) oil, oil hazes, and oil smears occur in many
samples; in some of these samples the oil is closely
associated with exsudatinite (Figure 3, part 5 ) suggesting that the oil is formed either from the exsudatinite
or, alternatively, the exsudatinite and oil formed at the
same time from the same or different precursors. In
clastic rocks associated with the coals, oil droplets and
oil hazes occur but these same rocks also contain the
same maceral assemblages as the coals, including
bitumen which has similar optical properties to the
exsudatinite in the coals. Thus the oil in these rocks
was probably generated in the rocks as is the oil
generated in the coal. The presence of the oil is not
indicative of migration of hydrocarbons through the
rocks.
Exsudatinite is found in eastern Kalimantan coals of
soft brown coal rank and is therefore presumed it can
be generated during the soft brown coal stage (approximately 0.35% R,max), that is, in the very early
stages of coalification. The repeated intimate occurrences of exsudatinite with resinite, suberinite, cutinite,
and vitrinite macerals indicate the exsudatinite is
derived from these macerals.
Given the close association of liptinitehitrinite, exsudatinite, and oil, two probable pathways for the
involvement of exsudatinite in oil generation are suggested:
zyxwvuts
primary liptinite
vitrinite
-
-
exsudatinite
exsudatinite
-
oil
-.oil
Terminology
In previous literature a number of terms have been
used for organic matter referable to bitumen. The most
acceptable is that of Jacob,30who provided a classification of bitumen which showed that all types of bitumen
were derived from immature oils. The classification was
a tripartite classification as three types of oils could be
the starting material for bitumen formation-asphaltenerich, paraffin-rich, and naphthene-rich. The composition of the immature oil determined the chemistry of
the intermediate products and the end bitumen.
Optically, bitumen falls into two main groups:
(i) Nonfluorescing, vitrinite-like bitumen (spherical
thucholites are probably related to this form of bitumen); this bitumen represents coalified (or mature),
heavy fractions of “petroleum” derived from liptinite
and/or vitrinite during the normal oil generation processes.
(ii) Fluorescing bitumen: liptinite-like bitumen that
occurs as pods and cavity-fillings and in the groundmass
between clastic grains; this form is common in Green
River oil shale (Figure 4, part 4).
More recently, the term migrabitumen was introduced
by the ICCP, partly to indicate that bitumen is of
secondary origin rather than a primary maceral. Stach
et a1.26and ICCP (1990 Annual Meeting) defined migrabitumen as natural solid bitumen occurring in
sedimentary rocks, particularly in carbonates where it
infills intergranular porosity and fractures. Alpern et
~ 1 discussed
. ~ the
~ optical morphology of hydrocarbons
and oil progenitors in sedimentary rocks and divided
migrabitumen into three types using reflectance as the
discriminant, although the adjectives for the types were
colors. The plates given to illustrate the types of
migrabitumen, clearly showed all examples of bitumen
were in noncoal rocks.
With reference to other literature, many authors,
including S t r ~ c k m e y e r ,Panggabean,33
~~
and Sutrisman,34 described migrabitumen in dispersed organic
zyxwvu
zyxwvutsrq
( 2 5 ) Murchison, D. G. Fuel 1976,55,79-83.
(26) Stach, E.; Mackowsky, M.-Th.; Teichmuller, M.; Taylor, G. H.;
Chandra, G.; Teichmuller, R. Stach’s Textbook of Coal Petrology;
Gebruder Borntraeger: Berlin, 1982.
(27) Shibaoka, M. Fuel 1978,57, 73-77.
(28) Cook, A. C.; Struckmeyer, H. 2nd WA Oil Explor. Symp. 1415 Nov 1985, Melbourne 1986,419-432.
(29) Teichmuller, M. Int. J . Coal Geol. 1989,12, 1-87.
(30) Jacob, H. Int. J . Coal Geol. 1989,11, 65-79.
(31)Alpern, B.; Lemos de Sousa, M. J.; Pinheiro, H. J.;Zhu, X. Publi.
Museu Laboratorio Mineral. Geol. Faculd. Ciencas Porto 1992,3,53.
(32) Struckmeyer, H. I. M. Source rock and maturation characteristics ofthe sedimentary sequence of the Otway Basin, Australia. Ph.D.
Thesis, The University of Wollongong, Wollongong, 1988 (unpublished).
zyxwvutsrqp
zyxwvut
Hutton et al.
1476 Energy & Fuels, Vol. 8, No. 6, 1994
L
I
zyxwvutsrq
zyxwvutsrqpon
zyxw
Figure 4. Fluorescence mode unless otherwise stated; field width = 0.34 mn,. ,1)Bitumen in claystone underlying a coal seam;
bright yellow fluorescing organic matter mostly bitumen, orange-yellow fluorescing organic matter is bitumen mixed with mineral
matter. (2) Same field as 1; reflected white light. (3) Bitumen impregnating pods of mineral matter in a coal. (4) Green River
(USA) oil shale composed of alginite-rich layers (top and bottom) enclosing a pod of mineral matter impregnated with bitumen.
(5)Bitumen infilling cavity, containing pyrite, formed by intact ostracode shell; Stuart (Australia) oil shale. Bitumen formed by
thermal alteration (contact metamorphism) of oil shale when intruded by a dyke. (6) Large pod of bitumen with pyrite in Irati
(Brazil) oil shale. Note the two phases of bitumen as indicated by the different fluorescence colors.
matter (DOM) but stated that this organic matter is
referable to exsudatinite.
As all bitumen is of secondary origin and all bitumen
is likely to have migrated from the source, in some cases
this may be a great distance whereas, in other cases,
the migration may be out of fractures or porosity in the
(33) Panggabean, H. Tertiary source rocks, coals and reservoir
potential in the Asem Asem and Barito Basins, Southeastern Kalimantan, Indonesia. Ph.D. Thesis, The University of Wollongong,
Wollongong, 1991 (unpublished).
(34)Sutrisman, A. Source rock distribution and evaluation in the
Talang Akar Formation, Onshore Northwest Jawa Basin, Indonesia.
MSc. Thesis, The University of Wollongong, Wollongong, 1991 (unpublished).
source, the prefix “migra” is redundant and adds little
t o the name or understanding of bitumen. “Migra”
implies migration; it is likely that at least some bitumen
is formed in situ. It is difficult to justify the continued
use of the term migrabitumen.
In clastic rocks associated with Indonesian coals,
exsudatinite-like material is found. However, it is not
found as large-grained dispersed organic matter (DOM)
except where present in very large vitrinite phytoclasts;
it is mostly small interstitial organic matter referable
to bitumen and most of this material is probably better
termed bitumen.
Liptinite in Indonesian Tertiary Coals
The connotation of migration cannot be the reason for
assigning the term bitumen to organic matter. If this
was the case, some exsudatinite in Indonesian coals
would have t o be called bitumen. Some of the exsudatinite has strong fluorescence and this is probably a
function of its greater mobility relative to other types
of exsudatinite. A mobile origin is inferred as this type
of exsudatinite is found in cell lumens of semifusinite
and sclerotinite, macerals that could not themselves
generate or expel large amounts of secondary liptinite.
Thus some of the exsudatinite is not adjacent t o the
probable sources.
In carbonaceous shale or coal with pods of mineral
matter, exsudatinite-like organic matter is found both
as a cavity/fracture filling and in the mineral-rich pods
as well (Figure 4, parts 1 and 2). The fluorescence
properties are the same for both occurrences. Exsudatinite in the mineral-rich zones is identical to bitumen
in other rocks. The two are derived from the same
sources, primary liptinite, and by the same processes.
In most cases, if not all, exsudatinite is essentially
equivalent to bitumen. However, which is the best term
for it?
Much of the material reported to be bitumen or
migrabitumen is difficult to distinguish optically from
exsudatinite as both have similar properties (Figure 4,
parts 3, 4,and 6). Commonly it is only the association
with macerals or mineral matter that allows distinction
between bitumen and exsudatinite.
In contact metamorphic aureoles associated with
intrusions in at least two Tertiary oil shale in Australia,
Rundle-Stuart, and Nagoorin, mobile organic matter
formed by the pyrolysis of the alginite in the oil shales
migrated away from the source and condensed in pores
and cavities such as in osctracode shells (Figure 4,part
5). This mobile organic matter is optically similar to
bitumen andor exsudatinite, depending on the use of
the latter terms. Bitumen in Green River oil shale
(Figure 4, part 5) and bitumen in the Irati oil shale
(Brazil; Figure 4, part 6) also have properties the same
as exsudatinite.
Given the properties of both and the origin of both, it
would appear that the terms bitumen and exsudatinite
are interchangeable and in fact have been used variably
in the literature. Clearly there is a problem with
terminology-bitumen in one rock is exsudatinite in
another. Thus, as a means of simplification, the following terminology is suggested; the distinction between
the two is based on association rather than origin or
optical properties.
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zyx
Energy & Fuels, Vol. 8,No. 6, 1994 1477
1. Secondary, fluorescing liptinite found in fractures,
pores, and other cavities in coal, irrespective of optical
properties, should be assigned to the maceral term
exsudatinite.
2. Secondary, fluorescing liptinite found in clastic
rocks such as sandstone and shale, irrespective of optical
properties, should be assigned the name bitumen.
(Some of this bitumen may have been derived from a
source some distance from where it is observed.)
zyxwvuts
zyxwvuts
Conclusions
1. Indonesian Tertiary coals are vitrinite rich with
varying amounts of liptinite (0-25 vol %). Inertinite
is a minor component with sclerotinite the most abundant inertinite maceral.
2. Most coals are within the brown coal to highvolatile bituminous rank except those that are closely
associated with intrusions; the rank of these coals
commonly approaches semianthracite to anthracite close
to the intrusion.
3. An interesting feature of the Indonesian Tertiary
coals is the relative abundance of secondary liptinite,
especially exsudatinite and, to a lesser extent, fluorinite.
It is suggested that (i) the association of primary
liptinite with exsudatinite indicates exsudatinite is
derived from primary liptinite, particularly resinite,
suberinite, and cutinite. There is some evidence, although not convincing at this stage, that exsudatinite
is also derived from vitrinite. (ii) Indonesian Tertiary
coals with vitrinite reflectance 0.30-0.35% (which is
below the oil generation window of 0.5% vitrinite
reflectance postulated for Australian Tertiary terrestrial
source rocks) are probably at the low end of the oil
generation window.
4. Exsudatinite and bitumen (which has several
synonyms) are petrographically the same organic matter. For consistency of terminology, (a) secondary,
fluorescing liptinite found in fractures, pores, and other
cavities in coal, irrespective of optical properties, should
be called exsudatinite; (b) secondary, fluorescing liptinite found in clastic rocks such as sandstone and shale,
irrespective of optical properties, should be called bitumen.
5. Probable pathways for the formation of some of
the oil derived from Indonesian coals are
zyxwvutsr
primary liptinite
vitrinite
-
-
exsudatinite
exsudatinite
-
-
oil
oil
(1)
(2)
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zyxwvu
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zyxwvut
Energy & Fuels 1994,8, 1469-1477
1469
Liptinite in Indonesian Tertiary Coals
Adrian Hutton,* Bukin Daulay, Herudiyanto, Chairul Nas, Agus Pujobroto, and
Hakim Sutarwan
Department of Geology, University of Wollongong, Northfields Avenue,
Wollongong, N S W , 2522, Australia
Received July 6, 1994. Revised Manuscript Received September 6, 1994@
A comparison of the petrographic data for coals from various Indonesian Tertiary basins shows
that the coals have similar compositions with vitrinite the dominant maceral group. A feature
common t o most of the coals is the abundance of secondary liptinite, especially exsudatinite but
also fluorinite. The association of exsudatinite with oil, adjacent to, or within liptinite and vitrinite
macerals, suggests that exsudatinite is an indicator of oil generation, but at an early stage.
Exsudatinite is probably an intermediate product in the pathway vitrinitehptinite oil. Organic
matter referable to exsudatinite andor bitumen is found in coals and clastic rocks from eastern
Kalimantan. The petrographic properties of both are the same. It is suggested that, for
consistency of terminology, where this material is found in coal it should be termed exsudatinite
whereas where it is found in other rocks it should be termed bitumen.
-
Introduction
The Indonesian Archipelago formed through the
evolution and convergence of the northward-moving
Indian-Australian Plate, the westward-moving Pacific
Plate and the relatively stationary Eurasian Plate.1-4
Subduction of the Indian-Australian Plate beneath the
Eurasian Plate lead to the development of a major
magmatic arc system which is divided into two segments, the Sunda Arc in the west, and the Banda Arc
in the east. These arcs are associated with a series of
subduction zones which migrated, with time, in response to changes in the tectonic setting of the Indonesian region, resulting in the formation of intramontane (Early Tertiary), foreland (Late Tertiary), and
interarc (Late Tertiary) basins. Deposition of peat
occurred during pretransgressive stages in the intramontane basins and during a late regressive stage in
the foreland and interarc basins.
The most significant coal deposits, in Sumatera and
eastern Kalimantan (Figure l), are a major part of
Indonesia’s energy resources. Indonesia is rapidly
developing policies that will ensure equitable domestic
use of energy resources but a t the same time provide
substantial income from export commodities such as
coal and petroleum. Utilization of the coal resources,
both on the domestic and export markets, depends on a
thorough knowledge of the properties of the coal.
Indonesia’s petroleum resources are large by AsianPacific standards but many companies are still actively
exploring for new resources to augment the existing
reserves. For both the coal and petroleum scenarios,
organic petrography will become an increasingly useful
technique because it is one of the few techniques that
quantitatively characterizes organic-rich rocks. Because of the relatively recent exploitation of Indonesian
~~
coals on the world markets, the traditional benefits of
organic petrography for coal quality determination are
yet to be fully utilized. Realization that coal-bearing
sequences are source rocks for petroleum generation has
placed an added incentive for using organic petrography.
Continued exploration for petroleum will utilize organic
petrography both for typing source rocks and geothermal modeling, where vitrinite reflectance is the most
commonly-used maturation parameter.
In this paper, data on the composition of coals and
associated organic-bearing clastic sedimentary rocks
from eastern Kalimantan are compared with data for
coals from Sumatera and several other Indonesian
basins. The abundance of secondary liptinite macerals
is a common feature of many Indonesian Tertiary coals,
and this begs a discussion of the implication of these
macerals as indicators of oil generation and/or as
intermediates in petroleum generation. It is now generally accepted that coals may serve as source rocks under
some circumstances but several problems have remained unresolved. Is there available porosity to allow
migration of oil through coal t o the reservoir rocks? Are
liptinite macerals, especially exsudatinite, indicators of
petroleum generation? If so, are they indicators of
limited early oil generation or oil generation on a much
larger scale, sufficient to permit migratable amounts of
oil.
Given the relative abundance of secondary liptinite
macerals, comment is made on the suitability of presently-accepted liptinite maceral terminology.
Eastern Kalimantan Coals
zyxwvut
zyxwvutsrqp
~
@Abstractpublished in Advance ACS Abstracts, October 1, 1994.
(1)Hamilton, W. US.Geol. Sum., Profess. Pap. 1979,1078.
(2) Katili, J. A. Tectonophysics 1973,19, 195-212.
(3) Katili, J. A. Tectonophysics 1978,45, 2-14.
(4) CCOP-IOC. Studies in East Asian Tectonics and Resources
(SEATER), UNDPICCOP, Bangkok, 1980.
0887-0624/94/2508-1469$04.50/0
Economic coal deposits in eastern Kalimantan occur
in the Tertiary Tarakan, Kutei, Barito, and Asem Asem
Basins (Figure 2) which formed as a result of rifting
along, or close to, the eastern edge of the Kalimantan
continental block. Barito Basin and Asem Asem Basin
coals were deposited in retro-arc settings close to the
foreland whereas the Kutei Basin and Tarakan Basin
coals formed along the rifted border of eastern Kali-
0 1994 American Chemical Society
zyxwvutsrqp
zyxwvutsrq
1470 Energy & Fuels, Vol. 8, No. 6, 1994
Hutton et al.
zyxwvutsrqpo
Figure 1. Coal basins in Indonesia.
mantan. The coal measures sequences of Eocene and
Miocene age were deposited in environments ranging
from fluvial to deltaic.
The thickness of the coal seams varies from a few
centimeters to 40 m with dips ranging between 5" and
25" near the surface. Typically the Miocene coals are
thicker than the Eocene coals. Variations in thickness
are associated with splitting (particularly in Eocene
coals), wash-outs and wedge-outs. Splitting was probably caused by channel activity at the time of peat
accumulation.
Organic Petrography
In hand specimen, coals from eastern Kalimantan are
composed dominantly of clarain and vitrain lithotypes.
Inertinite-rich dull layers are very rare but are more
common in Miocene coals, particularly those from Mahakam and Sangatta, than in the Eocene coals. The
vitrinite-rich bright layers were derived from peat that
accumulated under water, in more reducing conditions
than were present for the inertinite-rich, dull layers
which were probably derived from peat that was exposed to an oxidizing atmosphere above the water table.
Maceral terminology used in this paper is that of the
Australian Standard for Maceral A n a l y ~ i s . ~
Vitrinite Reflectance. The rank of coals from
eastern Kalimantan generally spans the range of 0.3
to 0.6% vitrinite reflectance (Table 11, that is, from soft
brown coal to high-volatile bituminous ranks, with
thermally-altered coals from Sangatta reaching semianthracite rank (up to 2.03% vitrinite R,max).
Four groups are recognized: (1)Miocene, soft brown
to subbituminous coals subjected to regional coalification in areas with geothermal gradients normal for the
Indonesian islands; mean maximum reflectance (R,max)
values of 0.30-0.55%; (2) Miocene, subbituminous to
low-volatile bituminous coals subjected to regional coali(5) Standards Association of Australia, Standard, AS 2856, 1986.
fication in areas (characterized by strongly folded strata)
where geothermal gradients were above those normally
expected for the Indonesian islands; Rvmax values are
0.48-0.71%; these coals are restricted to the Sangatta
area where there is a relatively high geothermal gradient, related to intrusions, that has not previously been
reported; (3) Miocene, semianthracitic coals affected by
contact thermal metamorphism; Rvmaxvalues of 1.602.03%; and (4)Eocene, brown to low-volatile bituminous
coals subjected to regional coalification in areas with
geothermal gradients normal for the Indonesian islands;
RvmaX values of 0.43-0.66%; these coals were buried
to greater depths than the Miocene coals.
Although vitrinite reflectance of coals increases with
depth in deep drill holes, no significant general trend
was found within any single coal seam, except in the
Berau and Senakin coals where vitrinite reflectance
exhibits an increase from the top to the bottom of the
seam. These changes are assumed to be related t o
differences in vitrinite type.
Maceral Composition. Vitrite and clarite are the
dominant microlithotypes, with subordinate vitrinertite
(both vitrinite- and inertinite-rich microlithotypes),
duroclarite, and inertite. In some of the Mahakam,
Tanjung, and Sangatta coals, vitrite and vitrinertite are
dominant.
Vitrinite. Petrographically, vitrinite is the dominant
maceral, both in Miocene and Eocene coals, with the
vitrinite content of Miocene coals (range of 63.5-98.0%,
average of 82.9%; Table 2) slightly higher than for
Eocene coals (range of 61.9-93.9%, average of 79.4%).
Vitrinite consists predominantly of telovitrinite and
detrovitrinite with gelovitrinite content invariably low.
Telovitrinite, ranging from 0.04 to 0.20 mm in thickness, consists predominantly of textinite, texto-ulminite,
eu-ulminite, and lesser telocollinite. Thin layers of
telovitrinite are generally surrounded by a thick detro-
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Energy & Fuels, Vol. 8, No. 6, 1994 1471
Liptinite in Indonesian Tertiary Coals
’-*
SANGATTA
\
T
v)
v)
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*
T
200KM
LEGEND
PLIOCENE COAL
MIOCENE COAL
EOCENE COAL
Figure 2. Coal basins in eastern Kalimantan with resources.
vitrinite groundmass but some telovitrinite bands are
interbedded with detrovitrinite.
Attrinite and densinite are the most common detrovitrinite macerals with desmocollinite a minor component. Sparse to abundant gelovitrinite is disseminated
throughout the telovitrinite and detrovitrinite with
porigelinite occurring as thin bands within telovitrinite.
Znertinite. Inertinite content is generally very low and
is more abundant in Miocene coals (average of 4.2%)
compared to Eocene coals (average of 2.2%). Dominant
macerals are semifusinite, sclerotinite, and inertodetrinite with minor fusinite, micrinite, and macrinite.
Semifusinite commonly occurs as layers (up to 1.0 mm
in length), lenses, or isolated fragments, generally
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1472 Energy & Fuels, Vol. 8, No. 6, 1994
Hutton et al.
Table 1. Reflectance Data for Eastern Kalimantan Coals
gelovitrinitel
detrovitrinite
R,max
range
telovitrinite
R,max
range
Miocene
Berau
Sangatta
a
Mahakam
Asem Asem
Tanjung
Eocene
Tanjung
Pasir
Satui
Senakin
mean
R,max
0.45
0.64
1.88
0.48
0.36
0.61
0.39-0.55
0.49-0.72
1.61-2.03
0.40-0.55
0.30-0.41
0.57-0.65
0.44
0.62
1.81
0.46
0.35
0.39
0.37-0.54
0.47-0.69
1.55-2.06
0.37-0.54
0.29-0.41
0.33-0.47
0.45
0.63
1.87
0.47
0.36
0.40
0.61
0.63
0.51
0.57
0.57-0.65
0.58-0.67
0.44-0.54
0.54-0.64
0.59
0.61
0.50
0.56
0.54-0.63
0.57-0.65
0.42-0.53
0.50-0.63
0.60
0.62
0.50
0.56
Thermally altered coals.
Table 2. Petrographic Data for Eastern Kalimantan
Coalsa
vitrinite
Miocene
Beru
Sangatta
Mahakam
Tanjung
Asem
Asem
Eocene
Pasir
Tanjung
Satui
Senakin
a
inertinite
liptinite
range
mean
range
mean
range
mean
73.2-95.1
63.7-95.8
64.3-98.0
77.2-87.4
63.5-94.2
82.0
85.9
82.1
82.5
82.0
0.6-13.7
0.2-12.1
0.6-31.3
2.8-6.4
0.2-9.9
3.6 1.7-18.4
4.8 0.2-11.2
9.1 0.2-25.9
4.5 6.2-13.2
3.4 0.8-30.9
10.2
5.6
9.1
9.3
10.7
75.3-86.1
79.3-85.9
61.9-90.7
69.6-93.9
80.8
78.3
77.3
81.3
0.6-3.7
0.9-4.2
0.5-5.7
0.2-6.1
2.0
2.5
2.3
2.1
3.3-15.5
5.6-19.3
4.8-33.3
1.4-18.0
9.4
13.2
15.5
8.3
Mineral matter not included in the table
Table 3. Petrographic Data for Other Indonesian Coals
(Data from Various References Cited in Text)
maceral composition
vitrinite inertinite liptinite
Sumatera
Perapnap
West Aceh
Pliocene
Miocene
Oligocene
Meulaboh
Neogene
Paleogene
Ombilin
Banko Barat
Bukit Assam
Java
Bayah
Bojongmanik
reflectance
(range)
90-92
1-2
6-7
44-94
60-98
64-92
0-11
0-22
0-24
7-50
2-29
6-26
50-95
70-90
83-94
80-90
70-95
0-7
1-5
0-4
1-5
0-7
10-50
8-20
1-14
3-20
2-15
0.20-0.40
0.45-0.70
0.70-0.80
0.30-0.55
0.30-0.50
71-93
81-91
0-3
0-3
2-15
2-18
0.53-0.83
0.30-0.40
associated with vitrinite (mainly telovitrinite); in some
cases, cell lumen of semifusinite are filled with either
resinite, fluorinite, or mineral matter.
Some of the Miocene Mahakam coals contain anomalously high percentages of inertinite (31.3 and 18.3%,
respectively). These coals probably formed in areas with
more oxidizing conditions, possibly caused by a lowering
of the water table during peat formation, resulting in
more frequent exposure to the atmosphere.
Inertodetrinite is commonly associated with vitrinite
and semifusinite. Sclerotinite, consisting of unilocular
and bilocular teleutospores and sclerotia, is generally
scattered throughout the samples.
Lzptinzte. Liptinite is abundant in all coals (Figure
3) with the exception of thermally-affected coals from
Sangatta. (In the Sangatta coals, liptinite is not easy
to recognize because of the high rank.) Liptinite
contents average 11.6% which is typically higher than
for the Miocene coals where the average of 9.0%. These
differences are thought to represent differences in the
floral assemblages at the time of peat formation of the
respective coals.
Resinite, suberinite, cutinite, sporinite, and liptodetrinite are the most abundant liptinite macerals, both
in Eocene and Miocene coals, constituting 7 0 4 0 % of
all liptinite in most samples. Resinite has bright
greenish-yellow to dull orange fluorescence. It occurs
as discrete bodies and lenses with some occurring as
diffuse cell fillings in telovitrinite.
Suberinite commonly occurs as distinct layers (0.050.40 mm thick) with greenish-yellow to orange fluorescence, although in some of the Sangatta coals the
fluorescence is very weak brown or absent. Cell walls
of weakly fluorescing suberinite are thinner than the
more strongly fluorescing suberinite. Suberinite commonly occurs in association with corpogelinite, rarely
with resinite and exsudatinite, and is more abundant
in Miocene coals, particularly in coals with lower
vitrinite reflectance.
Liptodetrinite is rare to abundant in most samples
and mainly occurs in clarite where it has greenishyellow to orange fluorescence. Large fragments of
liptinitic material (typically > 7 ,um diameter) in some
of the Berau and Asem Asem coals are included as
liptodetrinite maceral because they cannot be assigned
to any other maceral.
Rare t o abundant cutinite commonly occurs in association with vitrinite and resinite but in some cases
it is associated with suberinite and exsudatinite. It
generally has greenish-yellow to orange fluorescence,
although some has very weak brown or no fluorescence,
particularly in the Sangatta coals.
Sporinite (including crassispores, pollen, and sporangia) has greenish-yellow to orange fluorescence and is
less abundant in Miocene coals than in Eocene coals. It
commonly occurs in association with detrovitrinite,
resinite, and suberinite. The distinction between pieces
of thick suberinite and sporinite within a single sample
is difficult in some cases although the sporinite generally has yellow to orange fluorescence whereas suberinite fluoresces greenish-yellow to yellow.
Exsudatinite, the secondary liptinite maceral that is
derived from other liptinite and vitrinite and which
infills fractures and pores in coal, is abundant in many
samples and constitutes up to 10% of some samples. It
occurs in most coals and commonly has bright greenishyellow to orange fluorescence. It has various shapes and
occurrences including infillings in fractures, bedding
plane cavities, and cell lumens.
Fluorinite and Botryococcus-related telalginite are
minor components and rarely exceed 1%of the bulk
rock. Fluorinite is rare to abundant in some coals and
typically occurs as isolated bodies and lenses with bright
green to greenish-yellow fluorescence of very strong
intensity. Botryococcus-related telalginite with bright
yellow to orange fluorescence occurs in Miocene Satui,
Senakin, and Tanjung coals and in a few samples of the
Berau coal. Telalginite is commonly disseminated
throughout the samples although some concentrations
are present. Maximum percentages of the Botryococcus-
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Energy & Fuels, Vol. 8, No. 6, 1994 1473
Liptinite in Indonesian Tertiary Coals
zyxwvutsr
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Figure 3. Fluorescence mode except where stated; field width = 0.34 mm. (1) Exsudatinite, infilling fracture, and sclerotinite in
coal composed of vitrinite (black), cutinite, and minor sporinite and liptodetrinite. (2) Same field as (l), reflected white light.
Nonfluorescing macerals are vitrinite and unilocular sclerotinite. Oil smear on vitrinite (right of field) escaping from fracture. (3)
Exsudatinite infilling fracture in vitrinite enclosed in cutinite; resin bodies also present; close association of exsudatinite with
cutinite suggests exsudatinite is derived from cutinite. (4)Exsudatinite infilling fracture between two layers of suberinite; clearly
exsudatinite is sourced from the suberinite. (5) Exsudatinite in vitrinite, with oil flowing from the exsudatinite, suggesting close
association between oil and exsudatinite. (6) Exsudatinite infilling fractures adjacent to resinite; exsudatinite unequivocally formed
from resinite.
related telalginite is 0.4%. Telalginite is also reported
in Eocene coals from Ombilin6y7and coals from Melawi
and Ketungau Basins8 and North Sumatera Basin.g
Mineral matter (mainly clay minerals, quartz, pyrite,
and carbonate) is sparse to common.
Oil and Oil-Related Substances. Coal is a sedimentary rock comprising organic matter, originally
deposited as plant fragments, which was converted by
biogenic and physicochemical alteration. This implies
that coal is solid in the same manner as other sedimentary rocks. However, coal bed methane desorption
experiments and organic petrography show that coal
contains components not regarded as macerals, inchd-
zyxwvutsrqp
(6) Daulay, B. Petrology of Some Indonesian and Australian Tertiary
Coals. M.Sc. (Hons) Thesis, The University of Wollongong, Wollongong,
1985 (unpublished).
(7) Daulay, B.; Cook, A. C. J. Southeast Asian Earth Sei. 1988, 5 ,
45-64.
(8) Sutjipto, R. H. Sedimentology of the Melawi and Ketungau
Basins, West Kalimantan, Indonesia. Ph.D. Thesis, The University of
Wollongong, Wollongong, 1991 (unpublished).
(9) Hadiyanto. Organic petrology and geochemistry of the Tertiary
formations at Meulaboh area, West Aceh Basin, Sumatera, Indonesia.
Ph.D. Thesis, The University of Wollongong, Wollongong, 1992 (unpublished).
zyxwvutsrqpo
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1474 Energy & Fuels, Vol. 8, No. 6, 1994
ing gases such as methane and carbon dioxide and liquid
components referred to by various names such as oil,
oil droplets, oil hazes, and oil smears. These “nonsolid
components may have been formed from the coal or have
migrated into the coal. Definitions of these and other
organic matter are as follows.
Hydrocarbons: used in a chemical sense in that the
material is composed of predominantly carbon and
hydrogen; oil and methane are examples.
Petroleum: naturally-formed liquid and gaseous hydrocarbons.
0il:liquid hydrocarbon derived from components of
the rock in which it occurs o r that has migrated into
one rock from another source rock; oil infills cavities in
coal as well other rocks; under the microscope oil may
occur as an (a) oil haze: fluorescing cloud emanating
from oil and dissolving in the immersion oil where this
is used; (b) oil smear, oil stain: fluorescing or nonfluorescing stain on the surface of the sample; commonly
brown in reflected white light; (c) oil drop, oil droplet,
free oil: oil occurring in fractures and cell cavities or
as drops on the surface or edges of grains.
Bitumen: solid hydrocarbon residues occupying fractures and other cavities; as will be discussed in detail
later, bitumen is equivalent to the maceral exsudatinite
and should be regarded as a secondary maceral; the
term bitumen is used in a petrographic sense not a
chemical sense.
Comparison with Other Coals. The maceral compositions and rank of coals from other Indonesian basins
are similar to those from eastern Kalimantan. Many
Indonesian coals, apart from being vitrinite-rich, have
low ash contents. These features of coals have been
interpreted as indicating a high moor origin.lOJ1
Coal type, or the petrographic composition of coal, is
related to paleoclimate, geological age, and tectonic
setting. The tectonic setting also plays an important
role in any subsequent burial metamorphism. As a
result of these factors, spatial and temporal variations
in paleoclimate, geological age, and tectonic setting can
cause variations in coal type or coal type provincialism.12
The range of plant components preserved in the peat
and the extent of alteration t o these components during
the diagenesis of the peat, and subsequent coalification,
determine coal type variations.13J4 Coals from eastern
Kalimantan are largely derived from ombrogenous peat
mires15J6which contained peats which were analogs of
the ombrotrophic peats described by C0u1ter.l~The
vegetation precursors of this type of peat is typically
tropical rainforest species dominated by angiosperms
(many of which were herbaceous), ferns and mosses that
developed in lowlands. Given the Indonesian coals are
Hutton et al.
all vitrinite-rich suggests that there is little coal type
provincialism in Indonesian coals.
Exsudatinite and Oil Generation
Is Coal a Source Rock? The role of coal as a source
rock for hydrocarbons has received increasing recognition over the past two decades. Numerous reservoirs
of significant size are associated with coal-bearing
sequences and in many instances, very few, if any,
clastic rocks with a marine origin are associated with
these sequences. The possibility of a marine source rock
for these sequences is unlikely unless the oil migrated
great distances. These types of reservoirs are found in
Australia, China, and Southeast Asia and this is now
taken t o be overwhelming evidence that hydrocarbons
are sourced from terrestrial matter in coal and that the
oil is expelled from the coal to reservoir rocks. Notwithstanding this, “The dispute such as it still exists
centers upon the question of expulsion, Le., whether the
oil, once formed, can escape from the coal into the
surrounding strata”.18
Hunt19stated that the high-wax, low-sulfur coals with
C29 steranes dominant and pristane to phytane ratios
usually above 5 indicated that the oils of the Gippsland
Basin of southeast Australia were derived from organic
matter deposited with terrigenous sediments. Hunt
argued that coal and terrestrial kerogen with either WC
ratios above 0.9, Rock-Eva1 hydrogen indices above
approximately 200 or liptinite contents of 15% or more,
have the potential to generate and release oil as well
as gas. Powell et a1.20confirmed that Australian coals
and terrestrial organic matter ranging in age from
Permian to Tertiary contain aliphatic structures capable
of producing paraffinic oils. These liptinite-poor coals
( < l o % liptinite) produced oil but of a type that has a
lower wax yield.
Of the three maceral groups, liptinite is considered
to have the greatest potential to produce hydrocarbons,
especially crude oi1.10~21~22
This concept was also suggested for a specific study on rocks thought to be the
source for the oils of the Ardjuna Basin, northwest Java.
In a study of the high-wax oils from that basin, Horsfield
et alSz3stated that the potential precursors were long
chain waxy paraffins in the coals of the Talang Akar
Formation. It was stated that the resinite and “related
macerals might play an especially important role in
petroleum expulsion”.
Large amounts of vitrinite, exsudatinite, and oil drops
and oil hazes in coal or carbonaceous shale are thought
to be indicators of hydrocarbon generation in these
rocks.24 If this hypothesis is accepted, Tertiary coals
from Indonesia are excellent source rocks providing the
oil is expelled to reservoirs.
Exsudatinite in Indonesian Coals. Exsudatinite
content of eastern Kalimantan coals ranges from (0.1
zyxwvutsrqpon
zyxwvutsrqp
(10) Smith, G. C; Cook, A.C. Fuel 1980,59,41-646.
(11)Titheridge, D. G. The geological and depositional setting of the
Brunner coal measures, New Zealand, and the influence of these factors
on seam thickness and petrological characteristics of Brunner coals.
Ph.D Thesis, The University of Wollongong, Wollongong, 1988 (unpublished).
(121 Cook, A. C. In Australian black coal - its occurrence, mining,
preparation and use; Cook, A. C., Ed.; Australasian Institute of Mining
and Metallurgy: Illawarra Branch, Australia 1975; pp 66-83.
(13) White, D. Bull. Acad. Sei. 1915,5,189-212.
(141 Smith, A. H. V. In Coal and coal-bearing strata; Murchison, D.
G., Westoll, T. S., Eds.; Oliver and Boyd: London, 1968; pp 31-40.
(151 Tennison-Woods, J. E. Nature 1885, 42, 113-116.
il6)Anderson, J. A. R. J . Trop. Geogr. 1964,18, 7-16.
(17)Coulter, J. K. Malay. Agric. J . 1957,40, 36-41.
(18) Levine, J. R. A m . Assoc. Pet. Geolog. Stud. Geol. Ser. 1993,3,
39-77.
(19) Hunt, J. Org. Geochem. 1991,17, 673-680.
(20) Powell, T. G.; Boreham, C. J.; Smyth, M.; Russell, N.; Cook, A.
C . Org. Geochem. 1991,17, 373-394.
(21) Snowdon, L. R.; Powell, T. G. Bull. Am. Assoc. Pet. Geol. 1982,
66,775-788.
(22)Tissot, B. P.; Welte D. H. Petroleum Formation and Occurrence;
Springer-Verlag: Berlin, 1984.
(23)Horsfield, B; Yordy, K. L; Crelling, J. C. Org. Geochem. 1987,
13, 121-129.
(24)Teichmuller, M.; Durand, B. Int. J . Coal Geol. 1983,2, 197230.
zy
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Energy & Fuels, Vol. 8, No. 6, 1994 1475
Liptinite in Indonesian Tertiary Coals
to 9.9% with an average of 0.8%;Miocene coals contain
relatively higher exsudatinite contents than Eocene
coals. In coals of both ages, exsudatinite normally
occurs adjacent to and within fractures in vitrinite and
liptinite (particularly resinite, cutinite, and suberinite,
Figure 3, parts 1-4, 6); by inference most, if not all, of
the exsudatinite originates from these macerals. Some
exsudatinite shows oil smearing and oil stains (Figure
3, part 5).
Exsudatinite in thermally-altered coal, referred to as
meta-exsudatinite to distinguish it from fluorescing
exsudatinite in lower rank coals, is present in some of
the Sangatta semianthracite which formed adjacent t o
an intrusion. In reflected white light, this metaexsudatinite has a higher reflectance than associated
macerals, including vitrinite, and does not fluoresce
which is assumed to indicate chemical alteration, specifically the loss of hydrogen. During coalification, the loss
of hydrogen is associated with the loss of volatile
hydrocarbons and water.
Reflectance of meta-exsudatinite is 2.70% whereas
that of the associated vitrinite is 1.74%,that of inertinite
1.58%, and that of liptinite 2.11%. Meta-exsudatinite
has also been recognized in anthracite found in Bukit
Asam, South Sumatera. In the anthracite, the reflectance of exsudatinite is also higher than that of the
associated vitrinite and inertinite. Meta-exsudatinite
in Bukit Asam is also formed during the thermal
alteration of high volatile bituminous brown coals
heated by intrusions.
In Indonesian coals, exsudatinite typically infills
veins, cell lumens, bedding planes and wedge-shaped
fractures, features also noted by M u r c h i ~ o nand
~ ~ Stach
et a1.26 It is also a binding agent for gelovitrinite in
some coals. From a review of early studies, Stach et
a1.Z6 noted that exsudatinite is mainly found in liptiniterich coals of subbituminous to high-volatile bituminous
rank. MurchisonZ5and ShibaokaZ7suggested that veinfilling secondary macerals (including exsudatinite) are
found in bituminous coals because they form as expulsions from other macerals, and subsequently migrate,
during the subbituminous stage. However, more recent
studies extended that range and exsudatinite now is
known to occur in coals of varying rank, ranging from
soft brown coal t o bituminous rank.
Earlier research shows exsudatinite may be directly
related to the formation of ~ i l . In~ low-rank
~ , ~ ~eastern
Kalimantan coals (for example, Asem Asem and Berau
coals) oil, oil hazes, and oil smears occur in many
samples; in some of these samples the oil is closely
associated with exsudatinite (Figure 3, part 5 ) suggesting that the oil is formed either from the exsudatinite
or, alternatively, the exsudatinite and oil formed at the
same time from the same or different precursors. In
clastic rocks associated with the coals, oil droplets and
oil hazes occur but these same rocks also contain the
same maceral assemblages as the coals, including
bitumen which has similar optical properties to the
exsudatinite in the coals. Thus the oil in these rocks
was probably generated in the rocks as is the oil
generated in the coal. The presence of the oil is not
indicative of migration of hydrocarbons through the
rocks.
Exsudatinite is found in eastern Kalimantan coals of
soft brown coal rank and is therefore presumed it can
be generated during the soft brown coal stage (approximately 0.35% R,max), that is, in the very early
stages of coalification. The repeated intimate occurrences of exsudatinite with resinite, suberinite, cutinite,
and vitrinite macerals indicate the exsudatinite is
derived from these macerals.
Given the close association of liptinitehitrinite, exsudatinite, and oil, two probable pathways for the
involvement of exsudatinite in oil generation are suggested:
zyxwvuts
primary liptinite
vitrinite
-
-
exsudatinite
exsudatinite
-
oil
-.oil
Terminology
In previous literature a number of terms have been
used for organic matter referable to bitumen. The most
acceptable is that of Jacob,30who provided a classification of bitumen which showed that all types of bitumen
were derived from immature oils. The classification was
a tripartite classification as three types of oils could be
the starting material for bitumen formation-asphaltenerich, paraffin-rich, and naphthene-rich. The composition of the immature oil determined the chemistry of
the intermediate products and the end bitumen.
Optically, bitumen falls into two main groups:
(i) Nonfluorescing, vitrinite-like bitumen (spherical
thucholites are probably related to this form of bitumen); this bitumen represents coalified (or mature),
heavy fractions of “petroleum” derived from liptinite
and/or vitrinite during the normal oil generation processes.
(ii) Fluorescing bitumen: liptinite-like bitumen that
occurs as pods and cavity-fillings and in the groundmass
between clastic grains; this form is common in Green
River oil shale (Figure 4, part 4).
More recently, the term migrabitumen was introduced
by the ICCP, partly to indicate that bitumen is of
secondary origin rather than a primary maceral. Stach
et a1.26and ICCP (1990 Annual Meeting) defined migrabitumen as natural solid bitumen occurring in
sedimentary rocks, particularly in carbonates where it
infills intergranular porosity and fractures. Alpern et
~ 1 discussed
. ~ the
~ optical morphology of hydrocarbons
and oil progenitors in sedimentary rocks and divided
migrabitumen into three types using reflectance as the
discriminant, although the adjectives for the types were
colors. The plates given to illustrate the types of
migrabitumen, clearly showed all examples of bitumen
were in noncoal rocks.
With reference to other literature, many authors,
including S t r ~ c k m e y e r ,Panggabean,33
~~
and Sutrisman,34 described migrabitumen in dispersed organic
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zyxwvutsrq
( 2 5 ) Murchison, D. G. Fuel 1976,55,79-83.
(26) Stach, E.; Mackowsky, M.-Th.; Teichmuller, M.; Taylor, G. H.;
Chandra, G.; Teichmuller, R. Stach’s Textbook of Coal Petrology;
Gebruder Borntraeger: Berlin, 1982.
(27) Shibaoka, M. Fuel 1978,57, 73-77.
(28) Cook, A. C.; Struckmeyer, H. 2nd WA Oil Explor. Symp. 1415 Nov 1985, Melbourne 1986,419-432.
(29) Teichmuller, M. Int. J . Coal Geol. 1989,12, 1-87.
(30) Jacob, H. Int. J . Coal Geol. 1989,11, 65-79.
(31)Alpern, B.; Lemos de Sousa, M. J.; Pinheiro, H. J.;Zhu, X. Publi.
Museu Laboratorio Mineral. Geol. Faculd. Ciencas Porto 1992,3,53.
(32) Struckmeyer, H. I. M. Source rock and maturation characteristics ofthe sedimentary sequence of the Otway Basin, Australia. Ph.D.
Thesis, The University of Wollongong, Wollongong, 1988 (unpublished).
zyxwvutsrqp
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Hutton et al.
1476 Energy & Fuels, Vol. 8, No. 6, 1994
L
I
zyxwvutsrq
zyxwvutsrqpon
zyxw
Figure 4. Fluorescence mode unless otherwise stated; field width = 0.34 mn,. ,1)Bitumen in claystone underlying a coal seam;
bright yellow fluorescing organic matter mostly bitumen, orange-yellow fluorescing organic matter is bitumen mixed with mineral
matter. (2) Same field as 1; reflected white light. (3) Bitumen impregnating pods of mineral matter in a coal. (4) Green River
(USA) oil shale composed of alginite-rich layers (top and bottom) enclosing a pod of mineral matter impregnated with bitumen.
(5)Bitumen infilling cavity, containing pyrite, formed by intact ostracode shell; Stuart (Australia) oil shale. Bitumen formed by
thermal alteration (contact metamorphism) of oil shale when intruded by a dyke. (6) Large pod of bitumen with pyrite in Irati
(Brazil) oil shale. Note the two phases of bitumen as indicated by the different fluorescence colors.
matter (DOM) but stated that this organic matter is
referable to exsudatinite.
As all bitumen is of secondary origin and all bitumen
is likely to have migrated from the source, in some cases
this may be a great distance whereas, in other cases,
the migration may be out of fractures or porosity in the
(33) Panggabean, H. Tertiary source rocks, coals and reservoir
potential in the Asem Asem and Barito Basins, Southeastern Kalimantan, Indonesia. Ph.D. Thesis, The University of Wollongong,
Wollongong, 1991 (unpublished).
(34)Sutrisman, A. Source rock distribution and evaluation in the
Talang Akar Formation, Onshore Northwest Jawa Basin, Indonesia.
MSc. Thesis, The University of Wollongong, Wollongong, 1991 (unpublished).
source, the prefix “migra” is redundant and adds little
t o the name or understanding of bitumen. “Migra”
implies migration; it is likely that at least some bitumen
is formed in situ. It is difficult to justify the continued
use of the term migrabitumen.
In clastic rocks associated with Indonesian coals,
exsudatinite-like material is found. However, it is not
found as large-grained dispersed organic matter (DOM)
except where present in very large vitrinite phytoclasts;
it is mostly small interstitial organic matter referable
to bitumen and most of this material is probably better
termed bitumen.
Liptinite in Indonesian Tertiary Coals
The connotation of migration cannot be the reason for
assigning the term bitumen to organic matter. If this
was the case, some exsudatinite in Indonesian coals
would have t o be called bitumen. Some of the exsudatinite has strong fluorescence and this is probably a
function of its greater mobility relative to other types
of exsudatinite. A mobile origin is inferred as this type
of exsudatinite is found in cell lumens of semifusinite
and sclerotinite, macerals that could not themselves
generate or expel large amounts of secondary liptinite.
Thus some of the exsudatinite is not adjacent t o the
probable sources.
In carbonaceous shale or coal with pods of mineral
matter, exsudatinite-like organic matter is found both
as a cavity/fracture filling and in the mineral-rich pods
as well (Figure 4, parts 1 and 2). The fluorescence
properties are the same for both occurrences. Exsudatinite in the mineral-rich zones is identical to bitumen
in other rocks. The two are derived from the same
sources, primary liptinite, and by the same processes.
In most cases, if not all, exsudatinite is essentially
equivalent to bitumen. However, which is the best term
for it?
Much of the material reported to be bitumen or
migrabitumen is difficult to distinguish optically from
exsudatinite as both have similar properties (Figure 4,
parts 3, 4,and 6). Commonly it is only the association
with macerals or mineral matter that allows distinction
between bitumen and exsudatinite.
In contact metamorphic aureoles associated with
intrusions in at least two Tertiary oil shale in Australia,
Rundle-Stuart, and Nagoorin, mobile organic matter
formed by the pyrolysis of the alginite in the oil shales
migrated away from the source and condensed in pores
and cavities such as in osctracode shells (Figure 4,part
5). This mobile organic matter is optically similar to
bitumen andor exsudatinite, depending on the use of
the latter terms. Bitumen in Green River oil shale
(Figure 4, part 5) and bitumen in the Irati oil shale
(Brazil; Figure 4, part 6) also have properties the same
as exsudatinite.
Given the properties of both and the origin of both, it
would appear that the terms bitumen and exsudatinite
are interchangeable and in fact have been used variably
in the literature. Clearly there is a problem with
terminology-bitumen in one rock is exsudatinite in
another. Thus, as a means of simplification, the following terminology is suggested; the distinction between
the two is based on association rather than origin or
optical properties.
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Energy & Fuels, Vol. 8,No. 6, 1994 1477
1. Secondary, fluorescing liptinite found in fractures,
pores, and other cavities in coal, irrespective of optical
properties, should be assigned to the maceral term
exsudatinite.
2. Secondary, fluorescing liptinite found in clastic
rocks such as sandstone and shale, irrespective of optical
properties, should be assigned the name bitumen.
(Some of this bitumen may have been derived from a
source some distance from where it is observed.)
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Conclusions
1. Indonesian Tertiary coals are vitrinite rich with
varying amounts of liptinite (0-25 vol %). Inertinite
is a minor component with sclerotinite the most abundant inertinite maceral.
2. Most coals are within the brown coal to highvolatile bituminous rank except those that are closely
associated with intrusions; the rank of these coals
commonly approaches semianthracite to anthracite close
to the intrusion.
3. An interesting feature of the Indonesian Tertiary
coals is the relative abundance of secondary liptinite,
especially exsudatinite and, to a lesser extent, fluorinite.
It is suggested that (i) the association of primary
liptinite with exsudatinite indicates exsudatinite is
derived from primary liptinite, particularly resinite,
suberinite, and cutinite. There is some evidence, although not convincing at this stage, that exsudatinite
is also derived from vitrinite. (ii) Indonesian Tertiary
coals with vitrinite reflectance 0.30-0.35% (which is
below the oil generation window of 0.5% vitrinite
reflectance postulated for Australian Tertiary terrestrial
source rocks) are probably at the low end of the oil
generation window.
4. Exsudatinite and bitumen (which has several
synonyms) are petrographically the same organic matter. For consistency of terminology, (a) secondary,
fluorescing liptinite found in fractures, pores, and other
cavities in coal, irrespective of optical properties, should
be called exsudatinite; (b) secondary, fluorescing liptinite found in clastic rocks such as sandstone and shale,
irrespective of optical properties, should be called bitumen.
5. Probable pathways for the formation of some of
the oil derived from Indonesian coals are
zyxwvutsr
primary liptinite
vitrinite
-
-
exsudatinite
exsudatinite
-
-
oil
oil
(1)
(2)