overview of source rocks and oils in indonesia (robinson, 1987)

IPA 87-1 1 /06

PROCEEDINGS mDONESIAN PETROLEUM ASSOCIATION Sixteenth Annual Convention, October 1987

AN OVERVIEW OF SOURCE ROCKS AND OILS IN INDONESIA

Kevin M. Robinson *

ABSTRACT

Source rocks in the hydrocarbon productive basins in Indonesia can be classified as lacustrine, fluvio-deltaic and marine. Lacustrine source rocks are the most productive, and have sourced most of the oil in Central Sumatra, some of the oil in the Sunda Basin and also possibly oil in the West Natuna Basin. Fluvial-deltaic source rocks are the most common and widely dispersed and have sourced oil in the majority of foreland (back-arc) basins of Western Indonesia. Marine source rocks probably occur in Eastern Indonesia, but are poorly documented. However, they may have sourced oil in the Salawati Basin and eastern Sulawesi. Positively identified producing source rocks are all Tertiary in age, although PrsTertiary (Permian/Jurassic) rocks are suspected to source oil in the Bintuni and Bula (Seram) Basins and are also a possible source in eastern Sulawesi and the Banggai-Sula area east of Sulawesi.

Crude oils in Indonesia can also I be characterized as lacustrine, fluvio-deltaic and marine based on a range of geochemical parameters, including pyrolysis-gas chromatography on the oils asphaltene fraction and GC-MS biomarker data. Lacustrine oils sourced from non-marine algae are generally low-medium gravity, waxy, low sulfur oils and often contain'unusually high concentrations of C3O 4-methyl steranes. Marine oils derived from marine algae are low- medium gravity, low wax, medium-high sulfur oils and contain C27-C29 diasteranes and steranes in relatively high concentrations compared to other oil types. Fluvio-deltaic oils derived from higher plant, terrestrial organic matter are medium-high gravity, waxy, low sulfur oils. They contain abundant higher plant resin derived C30 alkanes and low concentrations of steranes which are dominated by C29 diasteranes and steranes.

INTRODUCTION Source rocks can be subdivided into different organic

facies type based on microscopic and geochemical techni- ques. The organic facies is dependent on the depositional environment of the rock. Similarly crude oils can be characterized into different genetic types, generally lacustrine, terrestrial and marine, based on detailed chemical composition. The genetic category to which a crude oil belongs is -----_________ *) PT. CORELAB INDONESIA

obviously dependent on the original organic facies of it's source rock.

The main objectives of this paper are to

1) Categorise the source rocks of the major hydrocarbon producing basins of Indonesia into lacustrine (non-marine algal), fluvio-deltaic (terrestrial) and marine (marine algal).

2) Describe the general geochemical characteristics of the different source rock types.

3) Develop a scheme to classify Indonesian oils into lacustrine, fluvio-deltaic and marine based on detailed geochemical analyses.

SCOPE

This paper attempts to cover all the major hydrocarbon producing basins of Indonesia (Fig. 1). Identification of source rocks within the basins is primarily based on previ- ously published data and on experience gained in the area. However, source rocks within some of the basins are unknown, postulated or unconfirmed by detailed oil/source rock correlation studies. The oil classification is based on detailed geochemical data on one .hundred selected oil samples covering all the major hydrocarbon producing basins of Indonesia (Fig. 1).

SOURCE ROCKS

The major source rocks or suspected source rocks of the hydrocarbon productive basins in Indonesia are given in Table 1 and discussed below by depositional environment.

Lam strine Deep lacustrine productive source rocks containing non-

marine algae have only been positively identified in Cen- tral Sumatra (Pematang Brown Shale) and the Sunda Basin (Banuwati Shale) as shown in Table 1 .These lacustrine shales were deposited in Eocene to Oligocene, isolated, half graben, rift basins (Fig. 2). Lacustrine shales may also be the source of oil in the West Natuna Basin (Oligocene Barat Shale, Pollock et aL, 1 %4), although crude oil data suggests a different lacustrine depositional environment than that envisioned for the Pematang Brown Shale of Cen- tral Sumatra. Lacustrine shale source rocks may exist else-

© IPA, 2006 - 16th Annual Convention Proceedings, 1987

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where in Indonesia, particularly in the foreland (back-arc) basins of Western Indonesia, where rifting occurred in the Early Tertiary behind a volcanic island arc system.

The deep lacustrine shales of Central Sumatra were deposited in subsiding basins, under tropical climatic conditions. The lake had no annual turnover, resulting in anoxic bottom waters, which favoured preservation of organic matter rich in non-marine algae (Fig. 3; Williams e ta l , 1985). In shallow rift basins, where subsidence was only equal to the rate of deposition, humic rich lacustrine shales and coals wiU have formed instead (Central Sumatra Coal zone, Table 1).

Deep lacustrine shales are some of the most oils'productive source rocks in the world. In Central Sumatra they account for over half of Indonesia's oil reserves (Woodside, 1984). Immature, lacustrine shales typically contain between 1.0 to 10.0% total organic carbon and 50 to 100% oil prone, fluorescent non-marine algal derived amorphous kerogen. The pyrofysis yield (Sl+S2) is variable ranging from 4.0 to 75.0 mg hydrocarbons/gm rock, but is often very high. Hydrogen indicies are typically in the 400 to 900 range, with elemental kerogen hydrogen/carbon ratios usually greater than 1.4 (Table 2). Specific non marine algae such as Botrycoccus braunii or the non-marine planktonic algae Pediastium spp can sometimes be identified in the samples, while input from Botryococcus and dinoflagellates, can be inferred from GC-MS biomarker data (Wolf et aL, 1986; Brassel et al., 1986, Seifert and Moldowan, 1980).

Fluvio-Deltaic Source Rocks Fluvio-deltaic source rocks containing terrestrial de-

rived kerogen are the major source rocks of medium gravity, waxy crude oils in many of the foreland basins of Indo- nesia. In South Sumatra and N.W. Java (Sunda, Ardjuna, Jatibarang) Basin, Oligocene Talang Akar coals and shales have been identified as a major source of the oil, while in the Malacca Straits of Central Sumatra, Sihapas coals have generated some of the oil (Table 1).

In the East Java sea, Oligocene Kudjung I11 coals and shales and in the Barito Basin, Eocene Tanjung coals and shales are speculated to be the source of the oil (Tabb 1). Although neither of these correlations are proved in the published literature. In the offshore basins of East Kali- mantan, thick Middle Miocene and possibly younger deltaic coals and shales are a proven source of the offshore Kutei Basin oils, while thick Middle Miocene to Pliocene deltaics are the likely source of Tarakan oils (Table 1).

The offshore deltaic sediments of the Kutei Basin are

well documented geochemically (Combaz and Matharel, 1978; Durand and Oudin, 1979; Hoffman etd., 1984; Oudin and Picard, 1982; Schoell et aL, 1983; Schoell et aL, 1985). The major source rocks belong to the Middle Miocene Balikpapan Group. It represents a phase of delta progradation which has continued, with transgressive interruptions, through to the present day (Oudin and Pi- card, 1982). The sediments were deposited by an eastward flowing river system into a subsiding basin with a north-south axis. A full suite of facies typical of deltaic sedimentation were deposited (Fig. 4). Organic carbon content is relatively high throughout the deltaic sediments (often >2.%), but the best source rocks occur in the delta plain where coals tend to be concentrated (Fig. 5, Thompson, 1985).

Generation of hydrocarbons within the Kutei Basin is largely controlled by maturity, as thick, extensive, organic rich source rocks are present throughout a large part of the basin. The top of the oil window in the basin is variable, depending on temperature gradient, but in general is at about 2800 - 3000 meters (Schoell et aL, 1983). Oudin and Picard (1 982) have demonstrated that overpressure may also be important in the hydrocarbon distribution and type (oil or gas) within the Kutei Basin. In areas where the oil window is completely within the overpressure zone, generated oil cannot be expelled and is transformed to in situ gas. The Kutei Basin hydrocarbon generation model may also be applicable in the Tarakan basin, where sedimentation occurred along similar lines.

Fluvio-deltaic coal and shale source rocks have generated large volumes of oil in Indonesia and account for the major production of hydrocarbons in the Ardjuna and Kutei Basins. Fluvio-deltaic shale source rocks typically contain 2.0-10.0% total organic carbon with a pyrolysis yield of 6.0 to 20.0 mg hydrocarbons/gm rock. Coals usually contain 40.0 to 80.0% total organic carbon with very high pyrolysis yields of 150-300 mg hydrocarbons/gm rock (Ta- ble 2).

Fluvio-deltaic coals and shales generally contain only higher plant terrestrially derived organic matter, consisting predominantly of vitrinite with secondary amounts of cutinite and resinite. The total amount of waxy, oil prone, exinitic kerogen is usually in the 10-30%0 range. A small percentage of the vitrinite may also have &me liquid hydrocarbon potential, based on its fluorescence under U.V.

light. This is probably due to impregnation of the vitrinite with, or inclusions of, submicroscopic exinite. This type of vitrinite, which is called desmocollinite (Stach, 1982), has a lower reflectance level than normal vitrinite. The shales and coals typically have pyrolysis hydrogen indicies in the 200-400 range and kerogen elemental hydrogen/carbon ratios of 0.8 to 1 .O.

Liquid hydrocarbon extracts from fluvio-deltaic source

99

rocks usually have high pristane/phytane. ratios e3 .0) due to deposition in an oxik environment. They also have relatively high concentrations of waxy n-paraffins and C30 cyclic alkanes (identifiable by GC-MS) derived from higher plants.

Marine Source Rocks Marine algal rich source rocks are the major source of oil

in the world. But in Indonesia none have been positively identified in the literature. However, based on crude oil characterization a marine carbonate or calcareous shale source is suspected in the Salawati Basin of Irian Jaya (Phoa and Samuel, 1986; Hughes, 1984) and in eastern Sulawesi (Table 1). Deposition of the source rock would have occurred under anoxic conditions in a restricted marine basin. In Salawati a likely source is Early Miocene Klamo- gun carbonates and shales (Fig. 6), while in eastern Sula- wesi Early Miocene shales and carbonates are a possible source or alternatively Jurassic marine shales and carbonates.

Immature, marine source rocks capable of generating oils in the Salawati Basin and Sulawesi area would typically be expected to contain 0.5 to 5.0% TOC, moderate to high pyrolysis yields (2.0-30.0 mg hydrocarbons/gm rock) and an organic facies comprised mainly of oil prone, marine, algal derived amorphous kerogen. Pyrolysis hydrogen indicies should be in the 300-600 range and kerogen elemental hydrogenlcarbon ratios > 1.2 (Table 2). Re-Tertiav Source Rocks

All the Indonesian source rocks positively identified and correlated to oil accumulations in the published literature are Tertiaty in age. However, potential Pre-Tertiary source rocks have been identified in Eastern Indonesia (Chevallier and Bordenave, 1986) and are related to pre- break up of the Australian Plate in the Mid-Jurassic (Peck and Soulhol, 1986). In the Bintuni Basin of Irian Jaya two PrsTertiary sourced oil types possibly exist (Chev- allier and Bordenave, 1986) The major source of most of these oils is thought to be Late to Early Permian Aifat shales with Jurassic Tipuma shales or possibly Upper Permian Ainim coals acting as a source for the other oil type (Wiriagar oiI).All of the source rocks in theBintuni Basin are suspected to contain a predominantly terrestrial organic facies despite the marine setting of some of them.

In Seram (BuIa Basin) Early Jurassic-Late Triassic marine carbonates and shales are the suspected source of Pleisto- cene and Triassic reservoired oils (o’Sullivan et al., 1985). While marine potential Jurassic source rocks are also present in the Banggai-Sula area east of Sulawesi. OILS

The diagnostic characteristics of deep lacustrine, fluvio-deltaic and marine sourced Indonesian oils are outlined in Table 3. The oils are characterized based on bulk analy-

ses such as API Gravity, Weight % Sulphur and Gas Chromat- ography, plus, more detailed analyses such as Carbon Iso- topes, Pyrolysis-GC on the oils asphaltene fraction and Gas Chromatography-Mass Spectrometry (GC-MS) biomarker analysis on the saturate fraction of the oils. The characteristics listed are for oils generated at normal thermal maturity levels (Ro 0.5 - 1.0%) and unaltered by processes such as thermal or biological degradation or water washing. Bulk Data

Bulk Data such as API gravity, weight percent sulfur, gasoline range analysis and whole oil/saturate fraction gas chromatography give useful indicators as to the source of an oil, but are not detailed enough to positively identify its genetic origin.

Algal sourced oils, marine or non-marine, tend to have low-medium API gravities (20-35O) and pristanelphytane ratios less than 3.0. Initial differentiation of a non- marine algal oil from a marine algal oil can often be made based on sulphur content and wax content. Lacustrine oils are typically high wax (C31/C19 > 0.4), low sulphur (< 0.2 wt %); while marine oils are low wax ( < 0.4 C31/ C19), high sulphur ( > 0.2 wt %). Fluvio-deltaic sourced oils usually are medium-high API gravity (30-50’); low sulphur high wax crude oils (Table 3). They characterically have high pristanelphytane ratios 0 3.0) due to deposition of the source rock in an oxic environment (Powell and McKirdy, 1975).

The n-alkane distribution of oils (Fig. 7) can also be useful in distinguishing different oil types, although it is far from definitive. Lacustrine oils tend to have a bio- modal to broad n-alkane distribution due to input of C15- C19 and C23-C33 n-alkanes from non-marine algae (Gelpi etal,1970; Moldometal., 1985) and have low Pris- tanelnC17 ratios. Marine oils usually show a decreasing concentration of higher molecular weight n-alkanes (low wax content) and Pristane/nC17 ratios < 1.0. Fluvio-deltaic (terrestrial) oils usually show a broad n-alkane distribution or a predominance of waxy (C20+) n-alkanes and Pristane/nC17 ratios > 1.0. Carbon Isotopes

Carbon isotopes on whole oil, saturate, aromatic and other fractions of the crude oil have been used to differ- entiate marine oils from terrestrial oils. But, Sofer (1984) showed that this was invalid, based on a statistical analysis of a wide range of oils of known source. However, Sofer demonstrated that marine oils could be distinguished from terrestrial oils based on a Canonical value (G) calculated from the saturate and aromatic fraction carbon isotope values (Table 3). In fact the Cv value differentiates algal sourced oils, marine or nonmarine ((3 < 0.47), from terrestrial (fluvio-deltaic) sourced oils (Cv > 0.47).

Pyrolysis-GC Pyrolysis-GC on the oils asphaltenes is a relatively new,

100

and to some extent experimental technique. The idea behind the analysis, is that asphaltene molecules are small kerogen molecules and representative of the original kerogen in the source rock (Pelet et aL, 1986). Pyrolysis-GC of the asphaltenes can then be used to identify the original kerogen type of the oil’s source rock, based on the general distribution of hydrocarbons on the pyrogram. This can then be used to characterize the oils into different oil types (Fig. 8). Also the relative n-octene, m+p xylene and phenol content of the oil’s asphaltenes can be quantified and plotted on a Ternary diagram. (Fig. 9, modified after Larter, 1985) to determine oil type and the kerogen type of the source rock. The pyrolysis-GC on the oil’s asphal- tenis is performed at 550OC.

A typical lacustrine oil pyrogram (Fig. 8) shows well developed alkenes/alkanes doublets from C5-C35,with particularly high concentrations of C15-C30 n-alkenes/n-alkenes derived from non-marine algae. Characteristicly aromatics and phenolic compounds are virtually absent from the pyrogram. A typical marine oil asphaltene fraction pyrogram shows a decreasing concentration of n-al- keneln-alkane doublets with higher molecular weight and moderate concentrations of aromatics and phenols. A fluvio-deltatic oil shows a broad n-alkene/n-alkane distribution and contains the highest concentration of aromatics and phenols out of all the oils. Prist-l-ene also tends to be high in fluvio-deltaic oils.

A plot of the oil’s n-octene, m+p xylene and phenol content (Fig. 9) can clearly distinguish lacustrine oils from fluvio-deltaic oils. But marine oils, probably due to lack of data, cannot be distinguished from lacustrine oils. Oils pre- sumed to be from lacustrine sources in the West Natuna Basin and some of the oils in the Sunda Basin plot away from the deep lacustrine oils of Central Sumatra. This may be due to deposition of the oils’ source rock in a different lacustrine depositonal environment than that proposed for Central Sumatra. Possibly it was shallower and/or more saline?

GC-MS Biornurker Data

Lacustrine, marine and fluvio-deltaic oils in Indonesia can be distinguished based on Triterpane (m/z 191) and Sterane content (m/z 217). Other biomarkers can also be used such as Bicyclics (m/z 123), Isoprenoids (m/z 183), and Mono and Tri-aromatic Steranes (m/z 253, 231) but are not discussed here. Although it should be noted that the aromatic biomarkers are normally used as a maturity parameter, rather than as a correlation/depositional environment tool.

mterpanes mfz 191 Triterpanes (m/z 191) are broadly similar for all oil

types as bacterially derived 17d hopanes and moretanes are always present in oils (Fig. 10). Deep lacustrine sourced

oils in Indonesia tend to have simple Triterpane distributions containing only pentacyclic 17d hopkes from C27- C35 plus moretanes and little else. The Tm/Ts ratio, which is maturity and organic facies influenced, is usually less than 1.5 and Tricyclic Terpanes (not shown) are in low concentrations or absent.

Marine oils also have relatively simple hopane and mo- retane distributions, but in Indonesia tend to have high concentrations of C3 1 -C35 hopanes.. This is possibly due to deposition of the source rock in an anoxic calcareous environment, with high bacterial activity. Tm/Ts values tend to range from 3.0 to 1.0. In Indonesia 18doleanane is often in relatively high concentrations in these marine derived oils (Phoa and Samuel, 1986). This is thought to be due to transportation of resistant higher plant resins into the marine basin and not indicative of a terrestrial source for the oil. Noticeable other C30 resin derived compounds, commonly found in association with la oleanane, are absent or in very low concentrations. Marine oils also tend to have relatively high concentrations of tricyclic terpanes. Fluvio-deltaic oils have very characteristic Triterpane distributions with high concentrations of C30 higher plant resin derived cyclic alkanes and the C30 compound 18d oleanane. This is in addition to the normal range of hopanes and moretanes. The C30 derived compounds show characteristic peaks on the m/z 191, 163, 177,217,259 and 412 mass ion scans (Fig. 11). Tm/Ts ratios in terrestrially derived lndonesian oils tend to be relatively high and range from 6.0 to 1 .O.

Steranes mfz 21 7 Steranes relative to hopanes tend to be in low concen-

trations in non-marine oils, whether they are lacustrine or fluvial-deltaic in origin (Table 3). Typically sterane/l7d hopane ratios are <0.2 in non-marine oils and X . 2 in marine oils (Moldowan etal., 1985). Due to the low concentration of steranes, it can be difficult to obtain good sterane (m/z 217) scans in non-marine oils unless the GC column of the GC-MS is overloaded.

Deep lacustrine oils usually contain the full range of C27-C29 steranes and diasteranes (Fig. 12), albeit in very low concentrations, and usually have a roughly equal concentration of C27 and C29 steranes (Table 3). However, a characteristic of deep lacustrine oils in Indonesia is the unusually high concentration of C30 4-methyl steranes in many of the oils. These can be identified from m/z 231, 414 scans and are also present on the m/z 217 scan (Fig. 13). These compounds are believed to be derived from dinoflagellates (Wolf et al., 1986; Brassel et al., 1986) but are also probably derived from non-marine planktonic algae.

Marine oils contain a full range of C27-C29 steranes and diasteranes (Fig. 12), which are usually seen in marine

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oils around the world. The Salawati Basin oils show similar Triterpane and Sterane distributions to oils in the Mara- caibo Basin of Venezuela (Fig. 14). These oils are sourced from the Cretaceous La Luna Formation which is an organic rich carbonate (Talukdar etal., 1986). This would suggest a similar type of source rock may have generated at least some, of the Salawati Basin oils (klamogun carbonates and shale?).

Fluvio-deltaic oils have a very characteristic m/z 217 Scan usually containing only C29 steranes and diasteranes (Fig. 12). The dominant compounds on the scan are C30 resin derived cyclic alkanes, which are also present on the m/z 191 triterpane scan. A comparison of triterpane and sterane distributions (Figs. 15 and 16) of fluvio-deltaic oils from South Sumatra, Kutei and Tarakan Basins shows little variation between them, suggesting the organic facies and original higher plant input is similar in all these basins. A plot of C27-C29 sterane composition (Fig. 17) can dif- ferentiate lacustrine/marine oils from fluvio-deltaic oils, but cannot seperate lacustrine and marine oils from each other.

CONCLUSIONS

1) The source rocks of Indonesia can broadly be classified into lacustrine (non-marine algal), marine (marine algal) and fluvio-deltaic (terrestrial). Although signifi- cantly more oil/source rock correlation work needs to be done or published to confirm the source rocks of many Indonesian oils.

2) The identified source rocks are of Tertiary age, although Pre-Tertiary source rocks are probably generating oil in some parts of Eastern Icdonesia.

3) Crude oils can be characterized as lacustrine, marine or fluvio-deltaic sourced oils based on a combination of geochemical data. This includes standard bulk data, Carbon Isotopes, Pyrolysis-GC of Asphaltenes and GC- MS biomarker analysis. Lacustrine oils need further work to subdivide deep, fresh water lacustrine oils from shallowlsaline lacustrine oils.

4) Suspected Pre-Tertiary sourced oils should be analysed and classified to see what type of oils they are and if they show any differences, (particularly in biomarker distribution) from their environmentally equivalent Tertiary oils.

ACKNOWLEDGEMENTS

The author wishes to thank the management of P.T. Corelab Indonesia for permission to publish this paper and Mr. Kamaludin who performed the Pyrolysis-GC Analyses on the oils.

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TABLE 1 SOURCE ROCKS OF INDONESIA

HYDROCARBON BASIN* MAJOR SOURCE AGE DEPOSITIONAL ORGANIC GENERAL SOURCE ROCK PRODUCTIVE TYPE ENVIRONMENT FACIES OIL TYPE REFERENCE BASINS OF SOURCE ROCK

North Sumatra Foreland

Foreland

Foreland

Foreland

Foreland

Foreland

Foreland

Cratonic

Foreland

Foreland

Foreland

Inner Arc

Inner Arc

Foreland

Foreland

Baong shales? M-L.Miccene

Bampo? ) ) - Oligocene-

Bruksah?? ) E.Miocene

Marine

Marine Marine Deltaic

Marine algal/ Terrestrial. Marine algal/ Terrestrial Terrestrial/Non marine algal

Non-marine algal

Gas/Lght 01 Situmeang and DavIes, 1986 Soeparjadi 1983 Kingston, 1978

Central Sumatra Pematang Eocene- Brown shale Oligocene (major) Coal zone (minor) Sihapas coal E.Miocene and coal shale

Pematang brown Eocene- shale? Oligocene

Talang Akar Late Oligo- coals/coaly cene-Early shales Miocene

Deep Lacustrine GM. Gravity, Williams et al., waxy, L. 1985 Sulphur Condensatel light oil M. Gravity, Macgregor and McKen-

zie 1986 sulphur L-M. Gravity, Lee, 1982 waxy, L.sulphur M-H Gravity oil, L-Mod. waxy, L. sulphur/ condensate M. Gravity Mob, 1'"s waxy, L. s,ulphur

Bushnell and Atmawan 1986

M. Gravity, Gordon, 1985 waxy, low Wahab and Martono, sulphur 1985 M. Gravity, Soeparjadi et all973 mod waxy, low Russel, 1976 sulphur Bishop, 1980 M-H Gravity, low-mod waxy, low sulphur

M. Gravity, Siegar and Sunaryo, waxy, low sulphur 1980

M. Gravity, Dunand and Oudin waxy, low 1979 sulphur Thompson et al,

1985 M. Gravity, Samuel, 1980 waxy, low sulphur

Pollock et al. 1984

Shallow lacustrine/marsh-bog Fluviodeltaic

Terrestrial

Terrestrial Central Sumatra (Malacca Straits)

Deep lacustrine

Fluviodeltaic

Non-marlnc algal

Terrestrial South Sumatra

N.W. Java (Sunda)

N.W. Java (Ardjuna Jatibarang) E. Java Sea

Banuwati shales Early Oli-

Talang Akar Oligocene coals/shales -E. Miocene TalangAkar Oligocene- coals/coal y E. Miocene shales Kudjung Oligocene Unit 111 shales and coals?

Barat shales? Late Oligo-

gocene

cene

Deep lacustrhc

Fluvio-Deltaic

Non marlne algal

Terrestrial

FluvIo-Deltaic Terrestrial

Fluviatile Terrestrial

West Natuna

Barito

Kutei

Non-marine algal/ bacterial/terrestrial Terrestrial

Lacustrine

Tanjung coals?/ Eocene shales? Balikpapan Middle coals and Miocene and shales and Younger Younger Deltaics Latin coals and M. Miocene shales? Tarakan and Bu- Pliocene nyu coals and shales?

Fluvio-Deltaic

Deltaic Terrestrial

Deltaic Terrestrial

L-M. Gravity - Low wax, mod- high sulphur

E. Sulawesi (Banggai/Sula)

E. Miocene shales and car- nonates? Jurassic shales and carbonates? Manusela carbonateslcalc shales? Klamogun carbonates1 shales?

Siga shales carbonates?

Tipuma shales? (minor) Ainim coals? (minor) M a t shales? (mdor)

Early Miocene Marine Marine algal

Jurassic Marine

Marine

Marine algal

Marine Akgal? Bula (Seram)

Salawati

Early Jurassic

Late Triassic Early Miocene

Low-M. Gravity O'Sullivan et al., low wax, mod- 1985 high sulphur L-M. Gravity, Phoa and Samuel, low wax, mod- 1986 high sulphur Hughes, 1986

Marine algal/ minor terrestrlal

Oligocene Marine Marine algal/ Minor terrestrial

Terrestrial Bintuni M. Jurassic

Late Permian

LateEarl y Permian

Shallow marine

Fluvial-Deltaic

Shallow Marine

Chevallier and Bor- denave, 1986.

H. Gravity, LOW wax, Low sulphur

Terrestrial

Terrestrial

~~

* Based on Fletcher and Soeprrjadi 1976 ?? Uncertain

Tabl

e 2

CH

AR

AC

TER

ISTI

CS OF

TYPI

CA

L IN

DO

NES

IAN

IMM

ATU

RE S

OU

RCE

ROCK

S

Type

Li

thol

ogy

TOC

Pyro

lysi

s Yie

ld

Ker

ogen

%Oil

Hyd

roge

n K

erog

en

Pris

tane

/ W

t%

SltS2

Type

Pr

one

Inde

x El

emen

tal

Phyt

ane

mg

HC

/p ro

ck

Ker

ogen

H

/C R

atio

of

Ext

ract

Dee

p La

cust

rine

Fluv

io

Del

taic

Mar

ine

Shal

es

Shal

es

and

Coal

s

Shal

es

and

Car

bona

tes

1 .o-10.0

4.0-75.0

Am

orph

ous/

50-100

400-900

Alg

inite

2-1096 (Sh)

6.0-20.0

Vitr

inite

/ 10-30

200-400

40-80%

(Cl)

150.0-300.0

min

or

cutin

ite, r

esin

ite

0.5-5.00

2.0-30.0

Am

orph

ous/

70-100

300-600

Alg

inite

>1.4

1 .O t

o 2.5

0.8-1.0

>3.0

1.2-1.4

<2.5

Tabl

e 3

GEN

ERA

L CH

ARAC

TERI

STIC

S O

F M

AJO

R O

IL T

YPE

S IN

IND

ON

ESIA

API

W

t%

-

Pris -

nC31

6

13C

Cv

Ster

anes

Tm

/Ts

C30

ST

ERA

NES

C

30

Gra

vity

Su

lfur

BY

nC

19

17a H

opan

es

Res

ins

% C

2920

R

4-M

ethy

l C

2920

R+C

2720

R

Ster

anes

Dee

p La

cust

rine

20-3

5 43

.2

3.0-

1.5

>0.4

<0

.47

~ <O

.2 1.

50-0

.20

LOW

<6

5%

LOW

-Hig

h

Fluv

io-

Del

taic

30

-50

<9.2

>3

.O

X.4

>0

.47

<0.2

6.

0-1.

0 V

.hig

h 10

0%

Low

-Abs

ent

Mar

ine

20-3

0 >0

.2

2.5-

1 .O

<0.4

<0

.47

>0.2

3.

0-1.

0 Lo

w-A

bsen

t <5

0%

Low

-Abs

ent

Pris

=

Pris

tane

Ph

Y =

Phyt

ane

6 13C

C,

= So

fers

(198

4) C

anon

ical

varia

ble

Tm =

C27

17a

Tris

norh

opan

e Ts

=

C27

18aT

risno

rhop

ane

cv

= -2

.53

6 13

Csa

t+ 2

.22 6 1

3Ch0

- 1

1.65

106,

a m o m ~a * w a - >

a z ~

0 m a a 0 0 cr c3 >. I w I l-

Y . 0 2 0

0 - - a J

W w w

3-

0 t

107

CENTRAL SUMATRA LACUSTRINE SOURCE ROCK DEPOSITED IN HALF GRABEN RIFT BASIN

, . .. . +, .. . ,-

EN ECHELON , G R A B E N S

B A L A M AND RANGAU B A S I N S

C E N T R A L S U M A T R A

+ + f t

+ + +

t + + + + c + +

n- GRABEN (MIDDLE EOCENE): RAPID BLOCK- ROTATION, D E V E L O P M E N T O F D E E P ANOXIC L A K E WITH SLOW DEPOSITION O F PEMATANG BROWN S H A L E F O R M A T I O N .

A f t e r Williams e t .al 1985

FIGURE 2

W

”

0

M

109

RELATIONSHIP O F O I L P R O N E SOURCE R O C K T O MODERN D E L T A I C ENVIRONMENT

FIGURE 4

110

I I

l l7OE \ 118OE I

119 O E

+ 2.s

0 a5 6 0 K m

+

HANDIL F I E L D -ssw

119.E L...

I I SCALE Il’lOE I l 8 O E

I

LEGEND

mi BACK DELTA PLAIN PRODELTA W I T H FAIR SOURCE ROCKS

MARINE SHELF DELTA PLAIN WITH VERY GOOD SOURCE ROCKS

DELTA FRONT After Thomron a t 01 1985. ond Moanior at 01 19T5)

FIGURE6 - D E L T A I C MIOCENE SOURCE ROCKS - K U T E I BASIN

'.

GE

NE

RA

LIZ

ED

M

I o c

E N E

P

AL

E'O

G E

O G

R A

P H

IC M

AP

--

a

10

20 Km

OF

f

14

Mo

dif

ied

fro

m G

ibso

n - R

ob

inso

n 1

98

6 1

k--

.-..

S

AL

AW

AT

I B

AS

IN '

SU

GG

ES

TE

D

DE

PO

SIT

ION

OF

MA

RIN

E S

OU

RC

E

RO

CK

SA

LA

WA

TI

BA

SIN

F

lGU

RE

6

c

c

c

112

z 0

0 n

n c)

z m

0

0 m

113

P Y R O L Y S I S - G C O F C R U D E OIL A S P H A L T E N E S

In I

L A C U S T R I N E OIL TYPE I KEROGEN

M A R I N E O I L T Y P E 11 KEROGEN

I0 = n C 10 ALK ENE /ALKANE T = TOLUENE X = m t p XYLENE Pf = P R l S T - I - ENE

P H E N O L S / A L K Y L B E N Z E N E S T 8 X I \ FLUVIO - DELTAIC OIL

TYPE 1II KEROGEN

FIGURE 8

114

P Y R O L Y S I S - G C C L A S S I F I C A T I O N O F CRUDE OIL ASPHALTENES USING D I S T R I B U T I O N O F N - O C T E N E m + p XYLENE A N D

PHENOL

T Y P E III = KEROGEN T Y P E

*. MAR INE OILS (SALAWAT1,SULAWESI)

N OCTENE 100 Y o

Deep Lacustine Oils

Sunda Basin 1

Shallow Lacustine Oils (W.Natuna /Sunda Basin)

Fluvio - Deltaic Oils [N .W. Java ,East Java, Kutei ,Tarakan ,

T Y P E 111

100 ./a PHENOL too O/O

M.P. XYLENE

FIGURE 9

L L - 0

115

w w k!

It II I t t i II

I

o a a > j i -

0

116

F L U V l O - DELTAIC OILS - IDENTIF ICATION O F RESIN C 3 0 CYCLIC A L K A N E S

R

B

1 IR

C 2 9

2 9 n

30

M / Z 191 TRITER PAN ES R = C 30 CYCLIC ALKANES

OL = l a d O L E A N A N E C 3 0 = H O P A N E S

Ts,Tm= C 2 7 H O P A N E S

M / Z 217 STERANES 2 9 - S T E R A N E S

M / Z 163

M / Z 412 C 3 Q PARENT IQN

,C30

DERIVED

FIGURE 11

LA

CU

ST

RIN

E O

IL

TY

PE

I K

ER

OG

EN

'N 2

17

.00

-C

29

M

/CB

OM

l I

-._

. .

. . .

. I-----,

B 4

1

42

4

3

44

4

5

46

4

?

48

4

9

50

MA

RIN

E

OIL

T

YP

E I1 K

ER

OG

EN

D

-.

. 27

2

8

2 9

30

3

1

32

33

34

3

5

36

3.'

CR

UD

E O

IL T

YP

ES

OF

IN

DO

NE

SIA

S

TE

RA

NE

S M

I2

217

LE

GE

ND

C2

7

RE

GU

LA

R S

TE

'RA

NE

S C

29

M/C

30

M-

4-M

ET

HY

L

ST

ER

AN

ES

R

::

C 3

0 R

ESI

N D

ER

IVE

D C

YC

LIC

AL

KA

NE

S

. C

27

I - DIAS

TE

RA

NE

S

FL

UV

lO -D

EL

TA

IC

OIL

T

YP

E 11

1 K

ER

OG

EN

R

rc

2

0 R

I

FIG

UR

E 1

2

118

LACUSTRINE OIL *IDENTIFICATION O F C 30 4-METHY L STERANES FROM M / Z 217,231 AND 414 IONS

ION 217.00

M E T H Y L ERANES

I ! O N 414.00 I l l I 4oJ

30-

ao-

119

4 m N

r- N

W z a

-I 0

v ) - W I -

-

J 0

r n d w o z a -

J 0

0 m

m

N

W

w H I-

t 0 t- z W t w

-

-

a

4 00-

38

8-

191.2

0

1

KU

TE

l B

AS

IN

OIL

600-

500-

400-

30

C3

I

30

0-

200-

100-

10

20

30

40

ION

1

91

.20

4 00

TA

RA

KA

N

BA

SIN

L

OIL

c2

9 t C

30

,CJI

0’ .

28

3e

48

50

6 0-

c

t4 0

CO

MP

AR

ISO

N O

F T

RIT

ER

PA

NE

S (

M/Z

191

1 IN

S

OU

TH S

UM

ATR

A , T

AR

AK

AN

A

ND

K

U T

E I

BA

SIN

F

LU

VIO

- D

EL

TA

IC

SO

UR

CE

D O

ILS

LE

GE

ND

C2

9

= H

OP

AN

E

Tm

/Ts

: C

27

HO

PA

NE

R

= C

30

RE

SIN

DE

RIV

ED

CY

CL

IC A

LK

AN

E

OL

: 1

8 O

LE

AN

AN

E

24

-4

=

C2

4 T

ET

RA

CY

CL

IC

TE

RP

AN

E

I IO

N 1

91

.20

SO

UT

H

SU

MA

TR

A

OIL

IR RllTn

C 30

FIG

UR

E 15

121

COMPARISON O F S T E R A N E S ( M / Z 217) IN SOUTH SUMATRA, T A R A K A N A N D KUTEI BASIN F L U V I O - DELTAIC SOURCED OILS

R

M / Z 217 T A R A K A N BASIN O I L

LEGEND C 29 = STERANES C 2 9 .I = DIASTERANES R = C 3 0 R E S I N DERIVED

CYCLIC ALKANES

bl/Z 217

R

P

R

c29

ljh

R

S O U T H SUMATRA O I L

bl/Z 217

R

c29 L

K U T E I BASIN O I L

c 2 9

m

FIGURE 10

C2

85

0c

20

R

ST

ER

AN

E C

OM

PO

SIT

ION

OF

IND

ON

ES

IAN

C

RU

DE

OIL

TY

PE

S

( A

C?

cr

Hu

ang

an

d M

ein

sch

ler,

19

79

1

Lac

ust

rin

e /M

arin

e oi

ls

luvl

o - D

el ta

ic o

ils

C2

g5

d2

0R

FIG

UR

E 1

7

overview of source rocks and oils in indonesia (robinson, 1987)

Documents

pematang brown shale

thick middle miocene

higher molecular weight

west natuna basin

sula area east

oils asphaltene fraction

low sulfur oils

pyrolysis hydrogen indicies