IPA, 2006 - 18th Annual Convention Proceedings, 1989

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PROCEEDINGS INDONESIAN PETROLEUM ASSOCIATION

Eighteenth Annual Convention, October 1989

THE HYDROCARBON POTENTIAL OF THE LOWER TANJUNG FORMATION,

BARITO BASIN, S.E. KALIMANTAN

Indra Kusuma *
Thomas Darin **

ABSTRACT The Barito Basin is located along the south-eastern

edge of the continental Sunda Shield. It is separated from
Early exploration efforts in the Barito Basin focused
the Asem-Asem and Pasir Basins to the east by the recent-
on the large surface defined thrust structures in the ly uplifted Meratus Mountains. To the north it is dis-
northern areas. Despite the large initial discoveries in the tinguished from the Kutei basin by the Adang Fault/
Lower Tanjung Formation of the Tanjung Oil Field in
Flexure system or Barito-Kutei Cross High (Fig. 1).
1939, no sustained exploration program has focused on Within its internal framework, the Barito Basin contains
this known prolific sedimentary section, and the poor the present day NE-SW trending Barito Foredeep, which
understanding of its stratigraphy has produced only is flanked to the west by the Barito Platform or Shelf
limited successes since. and t o the east by the Meratus Mountains. The Buntok
Recent exploration efforts have defined a period of Basin is situated 60 km north-west of the Barito Foredeep,
early Tertiary rifting giving rise to a series of northwest and is an extension of the main basin which is now
to southeast trending horsts and grabens across the basin. separated from it by the south-westerly plunging Kesale-
These early Tertiary structural elements have been over- Sihung High.
printed by a Neogene compressional regime which con-
Early Tertiary tensile stress produced a rifted series
tinues to the present day. This more recent compression
of NW-SE horst and graben structures. The exact age of
has produced a left-lateral reactivation of the earlier
normal faults, giving rise to the recent structural confi- this rifting is not known, but the Late Cretaceous age of
guration of the basin. the underlying basement and Middle Eocene age of
overlying sediments places it within the Paleocene to Early
Major thickness and facies changes with four distinct Eocene (Fig. 2). While the bounding normal faults of
stages of deposition can be recognized and correlated these rifts extended longitudinally for more than 50 km,
across the basin in the Tanjung Formation. These varia- their vertical expression was probably no more than 500-
tions result primarily from the topography produced by 1000 meters.
the early Tertiary rifting.
The Lower Tanjung Formation (Stages 1 to 3) was
The terrestrial coals and organically rich shales of the deposited in these rifts as a transgressive sequence of
Lower Tanjung Formation are prolific hydrocarbon alluvial facies in the lower part, to shallow marine de-
source rocks, and have produced the oil emplaced in the posits in the uppermost part. The Upper Tanjung marine
Tanjung Field. These source facies are at optimum
shales and mark (or Stage 4)were deposited across most
maturity IeveIs over large areas of the basin. of the present day basin as this transgression eventually
At least five of these early Tertiary rifts have been submerged the topographic remnants of the horsts and
identified. In terms of migration and entrapment, each grabens. Relatively stable marine conditions with
must be considered a separate self-contained basinal numerous minor cyclic eustatic fluctuations prevailed
depocenter. Only the Tanjung Field graben, with over 600 throughout Upper Tanjung times until a major regressive
MMBOOIP, has been adequately tested. event in the Middle Oligocene exposed most of the basin
for a prolonged period.
BASINAL GEOLOGIC OVERVIEW
Following this erosional phase the shallow marine
Although the focus of this paper is the Lower Tanjung Berai carbonates were deposited in the Late Oligocene.
formation, a brief discussion of the Tertiary basin evo-
Carbonate deposition continued into the Early Miocene,
lution is presented here to place it in the proper context. but was increasingly interrupted by the influx of fine
grained clastics which may have prevented any large scale
PERTAMINA BKKA biohermal build-ups. Carbonate development ceased in
** Trend Energy Kalirnantan Ltd. the Early Miocene with the beginning of significant
108

prodeltaic clastic input from the west. Miocene deposition Warukin and Paringin structures to the east failed to
was dominated by an easterly prograding regressive encounter any significant hydrocarbon shows. Just prior
deltaic sequence. to the war seven delineation wells were drilled in the
This deltaic deposition was punctuated by a number Tanjung field, and extensive geological and photogeo-
of abrupt regressive events, and can regionally be divided logical surveys of the surface anticlines abutting the
into five stages comprising the Upper and Lower Warukin Kesale Range were undertaken.
Formations. The Lower Warukin grades from the pro- After the war, B.P.M. concentrated on development
deltaic Berai Marl at the base through delta front to lower of the Tanjung field and the construction of a pipeline
delta plain facies at the top. to Balikpapan, and by 1965 had drilled 89 wells in the
It is separated from the Upper Warukin by a sharp field. Four additional wells were drilled in the Kambitin
break in formation water salinities and an abrupt change structure from 1959 - 1964 to follow-up the small
to upper delta plain facies. Compressional wrench forces Kambitin-1 discovery, but these also yielded only small
were initiated in the Late Miocene with t.he emergence amounts of oil. The Menunggul and Hayup surface
of the Meratus Mountains to the east, the Adang Flexure structures were also unsuccessfully tested to the Lower
to the north, and rapid loading and subsidence across the Tanjung.
present depocenter. In 1965, an offset to the earlier well in the Warukin
The Dahor Formation was deposited in the rapidly structure discovered commercial oil in Miocene Lower
subsiding depocenter as deltaics from the north and west Warukin sediments. At the end of 1965, PERTAMINA
inter-fingered with thick clastic wedges being shed off the assumed responsibility for exploration and development
mountains to the east. This depositional regime continues in the Barito Basin from SHELL.
to the present day, with the Dahor thickness exceeding
PERTAMINA continued with the development of the
3000 meters near the mountain front.
Tanjung and Warukin fields, and completed the first
regionally extensive seismic reflection program (Fig. 4).
EXPLORATION HISTORY Further Miocene tests were drilled along the thrusted
anticlinal trend of the Warukin field, leading to the
The first geological reconnaissance of the Barito Basin
discovery of the Tapian Timur Field in 1967. The Lower
was conducted in 1854. In the late 19th century, B.P.M.
(the forerunner of Royal Dutch Shell), conducted the first Tanjung was also tested at the Bonkang structure without
systematic exploration in the Barito Basin. Small amounts encountering any significant hydrocarbons. A test at
of oil were recovered from shallow boreholes around Dahor Selatan-I, which at the time was believed to be
the southern extension of the Tanjung Field structure,
seeps on the Warukin surface structures, but none were
commercial. B.P.M. began an extensive reconnaissance was abandoned after an oil blow-out from the Lower
of the basin in the 1930s which included detailed surface Warukin, but an offset well failed to encounter the oil
mapping, surface pit excavation, shallow hand auger bearing reservoir. By 1972 most of the easily recognized
drilling, and gravimetric surveying (Fig. 3). surface structures had been drilled, and PERTAMINA
began a detailed seismic program to better define the sub-
Despite the occurrence of numerous seeps and surface surface structures. Numerous wells were drilled on these
structures in the Tanjung Raya, B.P.M. initially focused structures with limited success. In many cases the Lower
its efforts on the western parts of the basin where a Tanjung Formation was poorly developed and/or largely
number of gravity anomalies had been recognized, but absent. Tanta-1 drilled a basement high on an apparent
only one out of over forty wells tested a small amount southerly extension of the Tanjung Anticline, and
of gas. In 1937, NKPM (the forerunner of STANVAC) although the Lower Tanjung was thin and poorly de-
also drilled a number of shallow wells in the western area veloped, modest amounts of oil were tested from fractured
around the Kahajan River without encountering any Oligocene Berai limestone. A shallow Lower Warukin
hydrocarbons. sand in Bongkang-2 (which had targeted the Lower
B.P.M shifted its exploration focus back to the Tanjung) tested a moderate amount of dry gas. Two of
surface structures in the Tanjung Raya area in the late the three further tests of the Kambitin structure flowed
1930s with an extensive surface geological survey. small quantities of oil. In 1986, Bagok-1 was drilled on
Numerous shallow stratigraphic holes were drilled across the southerly plunging nose of the Kambitin structure,
the thrust faulted Tanjung Anticline, a number of which and although the Lower Tanjung sands were poorly
encountered significant oil shows. The deeper Tanjung-1 developed they tested in excess of lo00 BOPD. The
well was completed as an oiI discovery in Lower Tanjung appraisal well Bagok-2 was drilled in an up-dip position
Formation sandstones in 1938. Minor amounts of Lower 1.5 km to the north, but tested onIy water from these
Tanjung oil were also found in the Kambitin structure sands. The structural configuration of the Bagok/
to the west. Tests of the Miocene deltaics in both the Kambitin accumulations provided a strong indication of
 109

the stratigraphic trapping .component in the Lower in the Lower Warukin pro-deltaics. Semuda-1 was drilled
Tanjung sands. By 1983, declining production in the to test a seismically defined basement high, and en-
Tanjung Field had prompted two separate pilot water- countered only a thin veneer of shaley Lower Tanjung
flood projects, but a poor understanding of the complex sands with good live oil shows before penetrating
Lower Tanjung stratigraphy produced disappointing Paleocene andesitic volcanics where the well was sus-
results. pended.
In 1968, CONOCO obtained exploration rights to a TREND then entered into a 9 month joint technical
large part of the southern basin area and focused their study with PERTAMINA utilizing their combined data-
efforts on Berai reef plays. Five wells on the shallow shelf bases and further detailed field work in an attempt to
area failed to encounter any significant biohermal build- better define the development and distribution of the
ups or hydrocarbons. In 1972, CONOCO farmed out to Lower Tanjung Formation. The concept of Early Tertiary
PHILLIPS, who concentrated on Tanjung-type moun- rifting led to the further acquisition of 300 km of seismic
tain front thrust structures. A sub-thrust structural test by TREND in 1988.
(Martapura-lx) encountered only minor oil shows in the
poorly developed Lower Tanjung sands, and PHILLIPS STRUCTURE OF THE BARITO BASIN
PSC relinquished the acreage. The Barito Basin lies on the south-eastern edge of the
continental Sundaland plate fragment. Based on detailed
PEXAMIN acquired exploration rights to an area just
surface mapping in the Southern Meratus Mountains,
west of the Kambitin wells in 1970. Two wells tested
Sikurnbang (1986) developed the geological model
subtle anticlinal features, but development of the Lower
illustrated in Figure 5 for the Pre-Tertiary evolution of
Tanjung was poor and no hydrocarbon indications were
the area. His work provides the framework for a possible
encountered.
interpretation of the complex tectonic evolution of this
In 1981, AMOCO was awarded Block C encom- area since the Early Cretaceous. Based on fossil evidence
passing the western shelfal area of the basin where and radiometric dating, he postulated a mid-Cretaceous
CONOCO had worked earlier. Their 24-fold seismic period N-S subduction and volcanic arc formation along
coverage yielded far better results than CONOCOs the eastern margins of Sundaland. This was followed by
earlier 6-fold coverage. Their first well targeted the Lower a Late Cretaceous arc-continent collision with oblique
Tanjung across a seismically defined basement high, but subduction/obduction. This left-lateral wrenching along
the target sands were largely absent and the well was the Meratus suture produced a NW-SE Late Cretaceous
sidetracked to test an interpreted Berai reefal build-up pull-apart basin bounded by syn-depositional left-lateral
nearby. Some limited posr-Berai biohermal carbonates wrench faults (Fig. 9). By the Early Eocene a divergent
were encountered, but tested only water, and AMOCO \+rench stress regime dominated Southeast Kalimantan,
relinquished the block in 1984. possibly as the result of changes in the relative motion
Also in 1981, TREND was awaided Block l3 of the Australian plate. This tensional stress gave rise to
covering the southern and central portions of the basin. a series of NW-SE trending rift basins followed by a
TREND initially focused on the mountain front edge prolonged period of subsidence and sedimentation ex-
(where numerous oil seeps had been found) with 1196 km tending into the Late Miocene. Since then, the westward
of 24-fold seismic coverage. The first well, Miyawa-I, strike-slip propagation of the Pacific plate along the
tested the Lower Tanjung in a sub-thrusted fault trap, Sorong and Tarera Faults has re-activated the old
and encountered over 600of good oil shows. However, Meratus convergence zone.
the well had entered a complex fault zone and tests of Large variations in the pre-Tertiary basement topo-
this interval failed to recover any fluids. A second well, graphy and rapid lateral variations in the Lower Tanjung
Birik-1 was drilled to test a seismically defined deep sub- stratigraphy had been suggested by gravity data and
thrust roll-over in the Miocene Warukin formation. earlier well correlations (Fig. 12). The presence of NW-
Numerous oil shows were encountered, but reservoir SE aligned horsts and grabens was clearly demonstrated
quality was again poor. The results also showed that the with the integration of photogeology, radar imagery, field
interpreted structure was probably a velocity artifact of data, well data, gravity, and seismic mapping. The more
the thick overlying Dahor conglomerates. TREND then recent detailed field napping along the mountain front
focused on the central basin area with the acquisition of (Fig. 13) revealed thickness and facies variations very
a further 1687 km of seismic and 1900 km of gravity. similar to those observed in distant well correlations. The
Bangkau-1 tested a subtle fault closed roll-over in the seismic data also clearly showed the basement fault block
Warukin Formation and encountered numerous good oil structures (Fig. 6) and the pervasive NW-SE trend of
shows in poor quality reservoir sands. The well was normal faults bounding these fault blocks. Although it
suspended in severe over-pressures with large amounts is difficult to correlate deep events across the current
of free oil invading the borehole from thin silt laminae depocenter, these normal faults can be tied to those
 110

revealed by photo-geolqgy and radar imagery interpre- These synthetic faults are observed in outcrop in the
tation in the mountain from outcrops. Meratus Mountains and Kesale-Sihung High area, as well
as observed seismically. Older Cretaceous structural
Bouguer gravity data and subsequent gravity
elements bordering the Manunggul Basin have also
modeling also showed large gravity minimum trends
undergone re-activation as NE-SW left-lateral wrenches.
corresponding to the seismically interpreted grabens. The
In the Kesale-Sihung uplift, these faults grade laterally
alignment of the horsts and grabens is best revealed by
into first order thrust structures as their orientation
a time isopach map constructed from an intra-Tanjung
changes to N-S and horizontal compression is re-oriented
reflector to basement (Fig. 7).
to E-W.
Following the relatively rapid graben infilling, rates The arcuate form of these thrusted anticlines, and
of sedimentation from the Late Eocene to the Middle their oblique orientation relative to the main mountain
Miocene were reduced, but increased significantly with zone of deformation, are also characteristic of the overall
the Middle-Late Miocene advance of the Warukin
convergent wrench stress regime. The thrusted features
deltaics. The effect of the basement topography on
display a distinct en echelon arrangement which de-
deposition decreased with time, yet differential compac- teriorates away from the major Meratus Mountain Front
tion within the grabens continued to influence depo- zone of deformation. The structural cross-section in
sitional patterns. Even today, away from the rapid Figure 10 illustrates the en echelon (or imbricate) thrust
deposition near the mountain front, subtle geomorphic
faulted structures near the mountain front which give way
features across the large low lying southern swampy areas
northwest to thrust faulted anticlines and eventually to
of the basin reflect the underlying basement topography. gentle unfaulted anticlines. A true en echelon pattern
Beginning in the Mid-Late Miocene and extending to seems to require wrenching, or at least some component
the present day a major tectonic event began to affect of wrenching, and thus may be unique to the wrench
south-eastern Kalimantan. The large scale regional assemblage style (Lowell, 1985). The tectonic wrench
mechanics of this movement are not perfectly understood, model also accounts for the almost complete lack of
byi h e result has been a general north-south left-lateral recent compressive structural influence in the southern
convergent wrench reactivation of the Meratus suture portions of the basin where the model predicts a localized
zone. Further north the influence of the WNW-ESE left- tensile stress regime. However, seismic data indicate areas
lateral motion along the Adang Fault adds a third in the south along the current depocenter with anomalous
regional stress regime, and considerably complicates t!le thick Upper Warukin sections. This may reflect the tensile
structural configuration in that area. The Adang fault (or reactivation of underlying older Paleogene normal faults
flexure, as it is poorly defined at the surface) is probably in this area, although seismic quality at these deep
a manifestation of the westward movement of the Pacific basement levels is admittedly poor.
plate propagated along the Sorong and Tarera Faults. It In summary, the Tertiary structural development of
may also reflect a re-activated southern bounding normal the Barito Basin is the result of two separate stress
fault of a large Paleogene graben which underlies the regimes: a Paleogene period of divergent wrenching and
Kutei Basin to the north. This is evidenced by much rifting followed by a Neogene period of convergent
deeper marine Tanjung sedimentation to the north, wrenching and uplift. The consequence of this stress
and the occurrence of Quaternary volcanics in the Teweh rerersal has been a re-activation of the older structural
area. elements during the more recent compression, rather than
The idealized diagrams in Figures 8 and 9 best illus- the development of entirely new structures. The form of
trate the model for structural development of the area. the Early Tertiary Barito Basin is therefore quite different
Oblique convergent wrenching produced the primary from the present-day basin.
thrusts and folds observed along the mountain front
which are characteristic of a welt. Numerous antithetic STRATIGRAPHY OF THE LOWER TANJUNG
WSW-ENE right-lateral wrench faults are associated with FORMATION
the primary wrenching, and are will defined from the The Lower Tanjung Formation sediments represent
field, photo-geology and radar imagery. Other subsidiary a transgressive sequence of rift infill sediment (Fig. 11).
structural features along the primary wrench include The source of these clastics was the exposed Sunda Shield
pinnate tensional and shear fractures, and second order to the west and the intervening horst highs. The deposi-
left-lateral wrenches. The principal horizontal com- tion and thickness of these sediments was governed by
pressional stress is in a NW-SE direction, and the NW- the topographic relief of the Paleocene horsts and
SE Early Tertiary normal faults represent pre-existing grabens. Regional cross sections (Fig. 12) indicate four
lines of weakness which were subsequently re-activated distinct stages of deposition with unique lithostratigraphic
as synthetic left-lateral wrenches. characteristics.
 111

The gross properties of these Stages can also be readily from the bounding horsts.
identified in the Field (Fig. 13). The lowermost three Stages Continued rifting and block faulting occurred with
comprise the Lower Tanjung Formation, and primarily decreasing frequency and intensity throughout Stage 1
represent localized non-marine rift infilling sediments. deposition. This is indicated by field evidence of syn-
The uppermost Stage 4 (also termed the Upper Tanjung depositional normal faults, seismically defined post-
Formation) represents regional marine deposition. The depositional block faulting, and by the fault compart-
100 Tanjung Field wells provide additional detail on local ments within the Tanjung Field at this level which only
variations. rarely extend into the overlying stages.
The graben depositional setting provides a fair degree Stage 2
of stratigraphic complexity and rapid lateral facies A distinct change in sedimentary character occurs at
variations. Numerous faults have been invoked in the past
the Stage 1 and 2 boundary where shallow lacustrine
to explain the wide variability in observed oil-water
facies give way abruptly to fluvio-deltaics. This dis-
contacts in the Tanjung Field.Whi1e some of these faults cordance probably represents a minor uplift and erosional
are syn-depositional in nature, most variations within the hiatus which may be related to doming in the final phase
field are related t o stratigraphic changes. of vulcanism associated with the rifting cycle.
Stage 1 This uplift and erosion produced a lower relief
Stage 1 sediments represent localized supralittoral rift- topography across the remnant basement highs. As a
infilling. Three distinct units are recognizable within this result, the Stage 2 deltaics were not restricted to the
stage: a basal unit of continental red-bed facies, an inter- grabens as the Stage 1 sediments had been. Initial de-
mediate unit of lower fan to lacustrine clastics, and an position occurred as distributary channel sands incised
upper unit of lacustrine or estuarine fine clastics. into the underlying unconformity surface. These fining
upward sands are coarse, clean, well sorted, and massively
The lowermost red-bed unit consists of inner to bedded, and are a major producer designated as the 2-860
middle alluvial fan conglomerates which are typically in the Tanjung Field. They comprise a series of stacked,
poorly sorted and poorly bedded. The basal cong-
incised channels whose overall NW-SE orientation is well
lomerates contain an abundance of well rounded quartz
defined from dipmeter data. These sedimentary features
pebbles to cobbles, with associated silicified rhyolite
provide a fairly strong stratigraphic trapping component
and volcanic debris. The poorly sorted clay to sand matrix in the Tanjung Field. They comprise a series of stacked,
precludes them as potential reservoirs. The radial concave to the grabens, but later Stage 2 sediments progressively
upward profile of these fans can be recognized in the onlap the remnant horst highs. These later sediments
Tanjung Field.
consist of fine-grained shaly distributary and lenticular
The intermediate Stage 1 unit consists of middle to crevasse splay sands, and organic-rich interdistributary
lower alluvial fan coarse stream flow and stream flood shales and coals which become dominant in response to
deposits near the graben margins. These grzde into finer peneplanation and decreasing relief. Dipmeter data
and better sorted shallow lacustrine deltaic sands and clearly indicate the fan-like crevasse splay nature of the
eventually to prodeltaic muds toward the graben axis. The productive but shaly 2-825 sand in the Tanjung Field.
maximum thickness and lithofacies variations are The top of Stage 2 deposition is marked by a distinct thick
observed in this unit, and volurnetrically it represents the coal section which provides an easily mapable seismic
majority of graben infilling. Two sands, the Z-1015 and event, and can be regionally correlated from wells to
Z-950 (Fig. 12), produce from this interval in the Tanjung outcrop. The lower Stage 2 fluvio-deltaic sands are a
Field, and the rapid lateral facies variations provide a very primary exploration focus due to their more regionally
strong stratigraphic trapping component. The fair to good consistent reservoir quality. By the end of Stage 2, graben
reservoir quality of these sands make them attractive infilling was virtually complete. Most of the intervening
exploration targets. horst blocks had been onlapped and clastjc input from
The uppermost part of Stage 1 was deposited in a them had largely ceased.
much lower relief shallow lacustrine or possibly estuarine
(although marine indicators are lacking) environment Stage 3
following the initial rapid infilling. Stage 3 deposition marks the first appearance of
It consists of low energy shales, silts, and sandy silts marine influence in response to the continuing regional
with numerous thin coals of limited extent. These clastics subsidence. This interval contains the first datable (Mid-
display distinct fining upward cycles suggesting periodic Late Eocene) marine micro-lossils and glauconite. elastic
higher energy conditions followed by periods of fluid input and grain size rapidly diminish as the last of the
stagnation. This unit is fairly uniform in thickness and remnant horsts are onlapped. The clastic source recedes
gross lithologic composition across the grabens away to the distant west producing a mud-rich/sand-poor low
112

energy marine environment and stratigraphic patterns calcareous coarser grained clastics and detrital coals
which are regionally correlatable. The underlying deposited during the regressive peaks, and marine shales
basement topography continued to influence deposition and marls in the intervening transgressions. These small
through differential compaction in the grabens, resulting cyclic events can be correlated regionally on modern high-
in slightly shallower coarser grained facies around the resolution wireline logs. Despite numerous oil shows in
horsts. this interval and the testing of oil from a thin shaly sand
A final post-rift igneous event, which was probably at Bagok-1, poor reservoir quality severely limits its
associated with the earlier pre-Stage 2 uplift and possible prospectivity.
doming, occurred during early Stage 3 deposition. This
is evidenced by volcanics described as dolerite (this GEOCHEMISTRY
description relies on cores recovered during early An exhaustive and integrated geochemical evaluation
appraisal drilling) at this level in the Tanjung field, and of the Barito Basin has yielded very positive results in
by stratigraphically equivalent andesitic lavas at one terms of hydrocarbon potential, and has permitted a
outcrop locale and at TD in the Semuda-1 well. The limits fairly complete picture of the complex geochemistry of
of this volcanic body are well defined in the Tanjung the basin to emerge. Due to the mobile nature of hydro-
Field. Its geometry and the appearance of increased heavy carbons in the subsurface, the following discussion is
minerals in the overlying sands indicates an extrusive necessarily expanded beyond the bounds of the Lower
event. Tanjung Formation.
The lower part of the Stage 3 sequence is characterized
by nearshore facies. The productive 2-710 sand in the Heat flow modelling
Tanjung Field and at Bagok-1 is composed of a number A heat flow study of the basin was undertaken to gain
of thin to locally thick, fine-grained, clean to shaly sands. a better understanding of the large differences in geo-
Dipmeter characteristics, coarsening upward cycles, and thermal gradients observed in the well data, and to aid
the planar cross-stratification observed in outcrop in defining the various maturity levels in the basin. Heat
strongly suggest barrier or intertidal bar deposition. These flow calculations were performed utilizing specialized
sands become much cleaner and slightly coarser where software to tie previously measured thermal conductivities
they onlap the volcanic extrusives (which are up to 35 (Thamrin, 1987) to sonic logs in order to correct for the
meters thick) in the Tanjung field, indicating that the considerable effects of compaction throughout the stra-
lavas provided a shallower locus for sand deposition. tigraphic column. Reliable formation temperatures were
Sand distribution becomes more lenticular and obtained from wireline log and DST data to calibrate the
sporadic towards the top of Stage 3 with increasing water computer calculated thermal conductivity and tem-
depth, but again higher concentrations and improved perature profile models of the wells. The objective of this
reservoir qualities are present in the vicinity of the approach was to minimize the effects of the highly
underlying highs. The marginally productive 2-670 shaly variable thermal conductivities of the overlying sedi-
sands and silts in the Tanjung Field and Bagok-1 consist mentary column in order to discern whether the observed
of individual discontinuous lenticular bodies deposited geothermal gradient anomalies were related to actual
as distal bars or pro-deltaic facies. Stage 3 deposition is crustal heat flow anomalies.
terminated by the transition to deeper marine conditions Geothermal gradients around the Barito Basin are
above the regional MI log marker. quite variable (Fig.l4), ranging from a low of 1.OSF/lOO ft.
In general, the stratigraphic disposition of reservoir at Birik-1 to a high of 3.08"F/100ft.at Bagok-I. Due to
quality sands within Stage 3 renders them a difficult the low compaction and high percentages of coal in the
exploration obiective, but the testing of over 10oO BOPD Warukin and Dahor Formations, geothermal gradients
in Bagok-1 from these sands highlights their prospectivity. are usually lower where they have been removed by
erosion. Gradients generally decrease from the west
Stage 4 towards the Meratus Mountains in the east, and this
Stage 4 sediments were deposited following a minor eastwards cooling is due in part to the effect of meteoric
depositional hiatus at the MI log marker. Low energy flushing of the very permeable Warukin sands exposed
middle sublittoral marine conditions prevailed with in the mountain front (artesian flow was observed in an
sedimentation rates and subsidence in rough equilibrium. Upper Warukin sand tested at Bangkau-1) which effec-
This stable basinal configuration persisted well into mid- tively act as a huge radiator.
Oligocene when Stage 4 deposition was terminated by a The large mass of highly corlductive igneous rocks in
drastic eustatic sea level fall. Also termed the Upper the mountains also provide a ready conduit for heat
Tanjung Formation, Stage 4 deposition is characterized propagation. The most interesting thermal feature is the
by numerous small cyclic eustatic fIuctuations with thin high gradient anomaly in the BagokIKambitin area,
 113

particularly in relation to the much lower temperatures cation.of the high heat flow anomaly and its likely hydro-
in the adjacent areas. thermal cause has important implications for maturation
The heat flow map (Fig. 14) shows the observed and hydrocarbon migration for the area to the south of
regional geothermal gradients generally reflect the Bagok-1.
ambient heat flow, and are not simply a function of
variable thermal conductivities. The hot spot in the Maturation
Bagok/Kambitin area remains intact and is all the more Lopatins Time-Temperature Index (TTI) has proven
puzzling considering that meteoric flushing of some of a popular analytical technique for maturity determination
the Tanjung sands appears to be occurring here via the because the required input data are simple, easy to obtain,
nearby outcrops to the north, which would presumably and seismic data can be utilized away from control points
have a cooling effect. The early Tertiary heat flows were where formation tops can be identified. The Lopatin
undoubtably much higher following initial rifting, but it method does underestimate maturity in the later stages
is unlikely that this initial high geothermal flux around of catagenesis, but this does not detract from its use-
the grabens (due to crustal thinning) has persisted to the fulness in identifying the areas within the current oil
present day. The more recent structural activity might window. The real catalyst for oil generation in the Barito
produce an increased crustal heat flow, but the localized Basin was the deposition of the Upper Warukin and
nature of this anomaly seems to preclude a tectonic cause. Dahor Formations which formed a thermal blanket over
Most plausibly, the Bagok/Kambitin anomaly probably the basin. As such, the higher rift phase temperatures of
reflects heat transfer via subsurface fluid movements the early basin are of minor importance in the TTI cal-
from deeper and hotter areas to the southeast. culations due to the shallow depths of burial, while the
Vitrinite reflectance (Ro) profiles can serve as a type recent Post-Warukin temperatures assume major im-
of paleothermometer to qualitatively give an idea of past portance. The results of the heat flow modelling provide
geothermal gradients. Higher heat flows that persist the required temperature input, and the TTI model can
through time ivould be expected to produce higher Ro be calibrated to existing well Ro data (Waples, 1985). This
gradients. Figure 15 compares all the available well Ro calibration procedure shows that the localized recent
data with the calculated heat flows in an attempt to cooling and warming events, highlighted by the Ro versus
quantify this relationship. Many of the wells are clustered heat flow plot, must be built into the TTI model to achieve
around the basin average, among them all of the wells at match with well Ro data in these areas. Away from
in the structurally undisturbed areas of Blocks B and these recent thermal anomalies, temperature histories
C supporting the essumption that the thermal regime taken as constant through time yield TTI values in
of the areas away from the Late Miocene tectonism have agreement with the well Ro data. Building these thermal
remained fairly constant through time. From the limited parameters into the TTI modelling yields a fairly reliable
data and the inherent weaknesses of this technique, it is indication of maturity in most wells in the basin. A
impossible to derive an empirical relationship between Ro number of horizons are well defined seismically and can
gradients and heat flow, but it does serve to highlight the be mapped with confidence, while other levels can be
deviations. estimated by interpolating thicknesses from surrounding
The wells located below an admittedly subjective wells for burial history reconstructions. A large number
expected normal trend would indicate higher relative of TTI models were thus constructed where seismic
Ro gradients than the current low heat flows would coverage exists using regional geothermal gradients and
warrant, while those above would indicate lower relative thermal history evidence obtained from the heat flow
Ro gradients than the current high heat flows would study.
suggest. Figure 16 shows the TTI maturation map at the top
Bagok-1 shows the largest deviation from the basin Stage 2 level where thick coals produce a strong seismic
average, suggesting that its high heat flow is indeed a reflector. The hydrocarbon deadlines on the maps are
relatively recent event. Conversely, the data from wells derived from empirical work and are expressed at the 80
along the mountain front and in uplifted areas suggest percent confidence level (Waples, 1985). Heavier hydro-
relatively higher heat flows in the past than at present. carbons could occur at higher TTI values, but their
This recent cooling is easier to explain in light of the uplift occurrences would be rather rare.
and removal of the insulating blanket of Miocene-Recent Due to the dominance of terrestrial kerogen, these
sediments, and the quenching effect of meteoric flushing deadlines probably extend to slightly higher TTI values,
through outcrops along the mountain front. with the bottom of the oil window in the TTI 180 to 200
This initial rudimentary understanding of the thermal range. The TTI map at this level reliably shows an area
regime of the basin has assisted in defining the mature in excess of 2500 km2 which has, or is currently going
source areas for hydrocarbon generation. The identifii- through the catagenic phase of hydrocarbon generation.
114

Large areas exist in the current depocenter where the and a minor resinite hump in the C15 range, which are
Lower Tanjung has already exhausted most of its all indicative of terrestrial kerogens. In fact, terrestrial
generative potential. The mature areas gradually diminish kerogens of a very similar composition predominate over
in areal extent at progressively shallower hoiizons. The the full Tertiary sedimentary sequence of the Barito
top of the oil window extends well into the Lower Basin. Even the marine facies contain an abundance of
Warukin Fornation, and over 2500m of mature Warukin terrestrial kerogen (although it is generally degraded as
is present in the current depocenter areas. Away from the a result of longer distance transport), indicating the
structural and thermal complexities in the north, the top proximity of the ancient shoreline throughout the basins
of the oil window is generally subparallel to the regional history.
structural dip, increasing from a high of about 8000 ft. in It has been shown that the Miocene coals of the
the Western limits to below 13000ft. in the much cooler nearby Mahakam Delta are related to the oils (Thompson
mountain front sub-thrust zone. eta!., 1985, Monthioux el al., 1983, and that potentially
The TTI models also illustrate the various maturity oil generative coals are common in many areas of
levels through time. The depocenter model in Fig. 16 Southeast Asia. The various source rock parameters show
shows that at the base Tanjung level, oil generation (TTI that the Lower Tanjung coals are typical of waxy oil
15) began about 20 million years ago during the initial prone organic matter and are very similar to the Warukin
stages of Early Miocene Warukin deposition. Oil ex- coals, which in turn are similar to those from the
pulsion at this level was well under way (TTI 40) by 15 Mahakam Delta (Curry, 1987). In order to determine if
million years ago, predating the Late Miocene Meratus these coals can in fact generate oil, artificial maturation
structural elements by a significant length of time. experiments were conducted on Lower Tanjung and
Lower Warukin coal samples. The coal was heated at
Source potential 325C for differing periods. The results in the following
Lower Tanjung Formation TOC analyses from wells table show that both the Tanjung and Warukin coals can
and outcrops show wide variations, from a low of under generate appreciable amount of liquid products. Analyses
0.50% to over 70% in Stage 1 and 2 coals. Overall, the of these artificially generated oils show that they closely
organic carbon content is greatest in the deltaics of Stage resemble the oils in the basin.
2, averaging between S-10% in the organically rich shales.
Sparse data also show similar concentrations in the Artificial Maturation Results
lacustrine upper Stage 1, indicating excellent source
potential for both these intervals. TOC decreases Yo coal converted
substantially in the marine Stage 3 and 4 sections, but to C15+ liauids
still averages 1.5070,resulting in poor to fair source
potential. Lower Taniune coal outcror,
The kerogen type of the drganic carbon determines 3 Days 6.7
the likely hydrocarbon products. Figure 17 illustrates the 6 Days 5.2
pyrolysis derived hydrocarbon index (HI) versus Tmax
plot. The best oil source potential (HI > 200) occurs in Bangkau-I Lower Iiarukin coal
the Stage I sediments, with Stages 2 and 3 apparently
3 Days 10.3
containing more gas prone Type 111 kerogen. The visual
6 Days 10.7
kerogen analyses summarized in Fig. 17, show an almost
complete dominance of terrestrial derived Type 111 Quantitatively, these results indicate that these Type
kerogen.
IIIH coals will generate approximately 0.02 to 0.04 barrels
The macerals are composed primarily of herbaceous of oil per cubic meter of sediment per one percent TOC. With
organic matter such as resinite, exinite, and cutinite an average hydrocarbon/carbon ratio of 0.95, approxi-
(resins, spores, and leaf cuticles), and are similar to gas mately 12 to 15 percent of the organic matter is assumed
prone Type III by elemental cornposition. to be converted to oil before gas generation becomes
However, it has become widely accepted that non- dominant at a H/C ratio of 0.80. This represents
sapropelic (humic) coals can act as oil sources, and that generated oil and does not take into account expulsion
Type I11 kerogen can generate waxy oil, probably from or migration efficiencies. Applying these quantities to
the cuticle and leaf coatings of higher plants. Horsfield rough volumetric calculations, p:oduces a figure of 2000-
(1984) has termed this kerogen Type 111 H. The source 4000 MMBO generated in the Stage 2 coals alone over
extract GC scan from the Lower Tanjung in Fig. 18 shows the mature areas of the Tanjung Field graben (using a
large peaks clustered around C29, a high odd n-alkane conservative average co21 thickness of 5 meters, mature
preference in this range, high pristane/phytane ratios, areal extent of 400 km2, and average TOC of 50%).
 115

Factoring in expulsion and migration efficiencies of 10 to severe overpressures. This oil is 5 to 7 per mil more
percent yields a range of 200 to 400 MMBO available for negative (isotopically lighter) than the other oils, and is
entrapment in the Tanjpng graben from this single coal. one of the most negative del 13C values published for
These figures do not take into account the varying oil anywhere (Curry, 1987). It is consistently anomalous
maturity levels of this coal across the graben to account in most other respects, and emerges as the one exception
for oil versus gas generation, but they are in the range to the clear groupings of the other oils. As such, this oil
of the amount of oil found in the area to date. may represent the only example of a previously unknown
third distinct group.
Characterization of oils Problems in correlating the oils with potential sources
All the oils recovered from wells and surface seeps arise due to the significant differences in the maturity
display very 'similar attributes. The terrestrial nature of levels of the oils and the source extracts. Since none of
the oils is clearly illustrated by their high wax content, the wells penetrated very far into the oil window, no data
high pristane/phytane ratios, high pristane/nC17 ratios, was available from source intervals with maturity levels
high resin content shown by anomalous peaks in the C13 comparable to the oils. These differences in concentration
to C16 range, and the dominance of C29 isomers in the between extracts and oils have been observed in the
sterane component of the G U M S data (Fig. 19, peaks Mahakam Delta fields and are also probably related to
7-9). The oils display a fairly narrow range of low to maturity (Schoell el al. 1983).
moderate maturity levels. Subtle variations, such as the However, enough data does exist to provide for
depletion of light end alkanes in the C8 to C13 range of reasonable correlations. The G U M S and carbon isotope
the Warukin oils, can be attributed to possible water distributions (Figs. 20 and 21) show that the best source
washing effects in the hydrodynamically active Warukin match for the Warukin group of oils are the Lower
Formation. Other variations result from biodegradation, Warukin Formation coals in the Bangkau-1. These coals
varying source maturities, and subtle differences in source are marginally mature, and along with the Birik-1 coal
organic facies. GC in Figure 18 are the most mature Warukin Formation
samples available. The best match for tlhe Tanjung oils
0il:Oil and 0il:Source Correlations are Stage 2 coals from outcrop and from the Tanjung-15
The similarity in the organic source facies of the well. These samples are likewise marginally mature, but
Tanjung and Warukin Formations leads to difficulties again are the most mature Lower 'Tanjung samples
in determining the origin of the oils. Differences in the available. Although this data is not entirely definitive,
relative distributions of GC measured compounds, as when taken in the context of the separate stratigraphic
illustrated by the scans and ternary diagram in Figures distributions of the two oil groups, it demonstrates that
18 and 20, may simply be the result of different maturity the coals and organically rich shales of the Lower
levels of the source or varying degrees of biodegradation Warukin and Lower Tanjung Formations are the primary
and/or water washing of the oils. GC/MS biomarker source facies for oil generation in the basin. At much
distributions (Figs. 19 and 20), which are in some cases higher maturity levels other organically leaner facies are
independent of maturity and/or biodegradation, likewise probably also significant hydrocarbon sources, as
show similar distributions with subtle but distinct demonstrated by the anomalous Bangkau-1 oil.
differences in the oils,
By far the most useful property for differentiating the EXPLORATION IMPLICATIONS
two groups has been carbon isotope data (Fig. 21), which
clearly defines a distinct separation and shows that the A number of Early Tertiary grabens have been defined
Warukin Formation oils are about 2 per mil more within the Barito Basin. These rifted basins provided
depleted in 13C (isotopically lighter) than the Tanjung the locus for deposition of the highly variable non-marine
Formation oils. This difference can not be accounted for facies of the Lower Tanjung Formation. The occurrence
solely on the basis of the slightly different maturity levels and quality of suitable Lower Tanjung reservoirs is thus
of the two groups. The combination of GC, G U M S , and dependent on their overall position within these individual
carbon isotope data clearly define two separate oil groups localized basins. From a n exploration viewpoint, the
within the basin. The separtion of these groups is in most locations of these rift basins are quite independent of the
cases coincident with the stratigraphic occurrence of the current structural configuration of the Barito Basin.
oils. An exception is the oil recovered from fractured Berai Geochemical analyses have clearly demonstrated
Limestone in the Tanta-1 well which shows a strong major oil source potential within the organically rich
affinity with the Warukin Formation oils. Another facies of the Lower Tanjung Formatio:i, and large areas
interesting anomaly is the Bangkau-1 oil recovered from of thermal maturity dictate large scale hydrocarbon
a Berai Marl sand at 10,200 feet within the transition zone generation and expulsion. Of particular interest is the fact
116

that oil generated within the Lower Tanjung Formation REFERENCES

is always observed to be restricted to reservoirs within
the Lower Tanjung, even in the presence of large thrust Bishop, W. 1980. Structure, stratigraphy and hydro-
faults as in the Tanjung Raya area. Also significant is the carbons offshore Southern Kalimantan, Indonesia.
lack of any known oil seepages or occurrences updip Bulletin of the American Association of Petroleum
on the Barito Shelf to the west of the mature areas or Geologists 64, 37-58.
the Tanjung Formation pinch-out edge. These observed
features imply that in terms of generation and migration, Curry, D.J. 1987. Geochemical evaluation of the Barito
each rift basin can be considered as a separate self- Basin, onshore Kalimantan, Indonesia. Sun Oil E&P
contained sealed system. Geochemical Services Group Report No. T071-1-87.

Detailed seismic coverage and extensive surface Harding, T.P. 1974. Petroleum traps associated with
geological investigations up to 1970 had revealed and wrench faults. Bulletin of the American Association
tested most or all of the prominent dip closed thrust of Petroleum Geologists 58, 1290-1304.
structures in the basin. The more recent exploration Horsfield, B. 1984. Pyrolysis studies and petroleum
activities have continued to focus only on these structural exploration. Advances in Petroleum Geochemistry,
aspects, and have been largely unsuccessful. 247-298.
The tests of the northernmost Bonkang and Hayup Lowel, J.D. 1985. Structural Styles in Petroleum Explo-
structures were probably geochemical failures due to the ration. Oil and Gas Consultants International Publi-
lack of mature source within this graben. The Neogene cations 49.
structures within the Tanjung Graben have proven in
excess of 600 MMBOOIP, although outside of the Monthiousm, M., Landais P. and Monin J.C. 1985.
Tanjung Field hydrocarbon occurrences have been Comparison between natural and artificial maturation
irregular. Recent studies show that trapping within these series of humic coals from the Mahakam Delta, Indo-
large dip closed structures contains a strong stratigraphic nesia. Organic Geochemistry 8, 275-292.
component, as might be expected within the highly
variable Lower Tanjung facies. At least three other PERTAMINA/TREND ENERGY 1987. The hydro-
seismically defined grabens exist to the south of the carbon potential of the Lower Tanjung Formation,
Tanjung graben at much higher levels of thermal Barito Basin, S.E. Kalimantan, Indonesia. Internal
maturity. The Neogene tectonism which gave rise to the report on the results of a joint technical study between
prominent structures in the Tanjung Raya area has had PERTAMINA and TREND ENERGY KALI-
little effect on these areas to the south except in the MANTAN LTD./PARTNERS.
complex thrusted structures along the mountain front.
Schoell, M., Teschner M., Wehner H., Durand B., Oudin
The concepts which have emerged in recent years provide J.L. 1981. Maturity related biomarker and stable
an exploration framework for exploiting the prolific isotope variations and their application to oil/source
potential of these untested grabens, and future explo- rock correlation in the Mahakam Delta, Kalimantan.
ration efforts will therefore have to focus on the stra- Advances in Organic Geochemistry, 156-163.
tigraphy of the Lower Tanjung Formation to define Sikumbang, N. 1986. Geology and tectonics of Pre-
stratigraphic or combined StructuraVstratigraphic Tertiary Rocks in the Meratus Mountains, South-East
trapping mechanisms in order to benefit from these Kalimantan, Indonesia. Unpublished doctoral thesis
concepts. submitted to University of London.
Thamrin M., 1987. Terrestrial heat flow map of Indone-
ACKNOWLEDGMENTS sian basins. Indonesian Petroleum Association pu-
The author wishes to thank the managements of blication.
PERTAMINA and TREND ENERGY KALIMANTAN Thompson, S., Morley R.J., Barnard P.C. and Cooper
LIMITED for permission to publish this paper. Many of B.S. 1985. Facies recognition of some Tertiary coals
the concepts outlined here were developed or refined applied to prediction of oil source rock occurrence.
within the PERTAMINA/TREND Barito Basin joint Marine and Petroleum Geology 2, 288-297.
study, and many thanks are due to the creative efforts
of the technical staff of that joint study under the Van de Weerd, A., Armin R.A., Mahadi S. and Ware
supervision of P.R. Davies (who was instrumental in P.L.B. 1987. Geologic setting of the Kerendan Gas
developing portions of the concepts outlined here), and and Condensate discovery, Tertiary sedimentation
to N.M. Henry. and paleogeography of the northwestern part of the
 117

Kutei Basin, Kalimantan, Indonesia. Proceedings of Ieum exploration. Bulletin of the American Associa-
the Sixteenth Annual Convention of the Indonesian tion of Petroleum Geologists 64, 9 16-926.
Petroleum Association 1, 317-338.
Waples, D.W. 1985. Geochemistry in Petroleum Expio-
Waples, D. w. 1980. Time and temperature in petroleum ration. Boston International Human Resources De-
formation: application of Lopatins method to petro- velopment Corporation 125-138 and 198-202.
 ~.
IlO*
LEGEND :

"
\
S E A

0.

-- -

FIGURE 1 - Tectonic Elements of Kalimantan

 119

LITHOSTRATIGRAPHY 2ZEO-
2 VOLCANIC
c FACES
0 EVENTS
sw NE (L

j\

LOWER
- R E 6 IOHAl
DELTA 3 UPLl F T
PLAIN
-
n
I-

-I
DELTA u
FRONT I

-
z
n

STABLE

YARIN E
RLCIONAL
UBSIDERCE

THOSPHERE
STRETCMNG

DELTA FRONT XKERITE

ZEl
F LU.V I 0-
0 ELTAlC S IFT BOMINC
+
UPLIFT

LACUSTRINE LCaLfZEO
OR UBSOENCE
ESTUARINE
f A N DELTAIC1

ALLUVIAL f A N
RlfTlltC
UPLIFT
rn
MDEUTE

FIGURE 2 - Barito Basin: Generalized Tertiary geologic framework.

120

m
FIGURE 4 - Barito Basin Exploration History,1965-Present.
 ROCK UNIT SEDIMENTARY AND VOLCANIC
ILD(I(*TY. 1"D
"OLCI"1C I "C#A"O(I..IC
I C * 0"s I W O LITHOLOGY
I I

TANJUNG
LUTETIAN FORMATION
50.!
YPRESIAN
- 542
THANETI AN
60:
DANIAN H O R N B E N D - P H I R l C ANOESITE W I T H MINOR VTUIH
BRECCIAS, AGGLOMERATES AND ASSOCIATED F I N E -
65 G R A I N E D PYROCLASTICS I S U B A E R I A L 1
MAASTRCH- ESTHERID-BEARING BLACK SHALE
TlAN
~ 73 POLY MI C T IC CONGLOME R A T E S , PEBBLY S A N D S T W E
rabatan F m t i o n AND LOCALLY MUDSTONES
CAMPANIAN
83 PYROXFNE-RASALTIC. ANOESITIC VOLCANICLASTICS
W I T H MINOR LAVAS, PYROXENEPHYRC ANDESlTES,
SANTONIAN RHYOClTlC LAVA FLOWS, IGNIMLRITE,TUFF BRECCIA.
AND CRYSTAL TUFF
.a?.:
CONlAClAN BEARING -TONES) TERRIGENOUSLIUST~(I
SOUE ARE @XITIC) ST'RATIFIEDCCRGLOUERATE )IN0
88.': MVOSTOHES B I V A L V ~ SAND GASTROPODS ARE CWND
IN S U I O S T P ( E S AND MUOSiaVES
INTERBEDOED G R A D E D C W S T P I
TlJRONlAN AND M u o w o w CONGLOMERATE ANDSANDSTD~E.ANI
GPADED TERR~ENCWJS LIWESTONES
91 AYYGa4LOICdL ~ L A G I O C L A S E - P H I R CANOESITES, AN!
VOLCANICLASTICS I N P-ACE
CENOMANIAN
INTERBEDDED GRADED VOLCANOCLASTIC SANDSTONES
97.C AND M U D S T a C S WSSING HTOREODISH-BROWN CHER
WITH W W l T W ' T RADIOCARIANS 3
ALBIAN VCLCANIC AND CHAOTIC F A W I C CCNGt.OMERAX A N D
POLYMlCTlC CONU.OI*ERATFS W I T H INTERBEDS C% G W
ED VOLCANOCLASTIC SbNOSTONES AND(RADI0LbRIAN
113 MUDSTONES VARIOUS TIPFS of L W S ~ s ( EMlWUl 2
G4L FORMATKIN1 OCCUR ASCCASTS OR BLOCKS
APTIAN
119
BARREMIAN
.
. - ____ . 125 C A l C A H l 0115, fERHIGrNOIIC, M I I I I ' I ~ I I N F ' BN " "
I N l F H L A l A l l O N OF r A l C A i 4 f C l ' I ? C A N 1 '.rJ'4FC
HAUTERlVlAN ANC LIMESTONES NOOULIS , l r i C U N C H E T 1 0 1 5 1
I N S C V E R A l PLACFS
--___ 131
VALANGNIAN
138
EERRlASlAN
144

FlGUm 5 - Summary of the Prc -Tertiary stratigraphic framcwork and gcological cvaluation of the Meratus Mountains,
Southeast Kalimantan.
 123

-
m

I
m
m

h
m
m
h
0
m

.-
h

h
(0
?-

h
N
h

h
W
W

h
O
W

h
t
I0

CI
a3
0

h
N
t

h
Q
m

&
0
ea

h
0
el

tr
Q
F

Q
01
c

n
-
rn
 000'000'1 : ! 3 l V 3 S
09 0
n
I
FIGURE 8 - Simplified structural and tectonic elements of the Barito Basin
176

NEOGENE STRESSES

FIGURE 9 - Neogene structure elements and model for convergent left lateral wrenching
 NW SE

DAW+l DIDI+ 1
4 0.
t

KEY
-
@ WARUKIN FM.

@ BERAl FM.
DAHAI T H R ~ S T
[;;;1 UPPER TANJUNG FM. 'ZONE AMBAKIANG
THRUST
@ LOWER TANJUNG FM.

BASEMENT

FIGURE 10 - Structural cross -section from Dayu - 1 to the Meratus Mountains.

128

I- uJ Z ~Q

I- < >

Z
(

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BOVI$ c~ ~ "T------- 3ewg

Utl
Z
wO 0

0
~E~E 0
"tO

~0 Z

C
~.~ > c~
E

w
w z
Z 0
0 ~
cO
~
Q
Z
E

B:

i
0 w co
<Z

0 D
 WNW ESE
DAYUal TANJUNG+l MARlDlllg 1
M 1 UNCONFORMITV

6 O0 -I

1aa-
1

160-

200

2 260
U
k-
W
z
- 300
u)
0)
w
2
Y
2 360
I
I-

400

460,

600
I 1

DAUOR SELATAN X I ' TAP'aN

660

600

FIGURE 12 - Lithostratigraphic ,well correlation, across Paleogene Graben.

130

w
z 0
0
0
0
0
0
0
0
Y)
0
0
0
0
n
0
0
0 Y) w c N N vl t

0
U
Ir
0

mi
131
0- F-3 'OIL wmoow'

I I
I
1.5
I NOTE : COMPILED FROM 14 WELL8
I CORRECTED TO MAXIMUM /
RECENT
I)URIAL DEPTH WHERE /
. I NECE88ARY.
7 . ALALAK4 1
WARMINO

I I SARITO4 1
MIYAWA41
I I MARIDU41
.o TANTWl
I I *.$ I)ONOKAI(Q*l
I I E M A 41
I 8ABW AVERAOES
:I; I I
.5 I I
I I
I I /
/
.**. \ I I I / m
I
!.O AVERAGE
I Ro GRADIENT 0.031/1000'
I (TO TOP OIL WINDOW)
I
r.e I /
I /
I
I
I
1.0
I I
i 0.02 0.03 0. 4 0.06 0.b 0

VlTRlNlTE I Ro GRADIENT1 1000'

I
32 I
V S DEPTH
I Vs. Ro GRADIENTS
I
I
J \ I
41 I I I I I l ~ l ' l ' l ' l ~ ~ m
0.2 o!a 014 016 0.0 0.r ole 0.0 1.0 1.2 1.4 1.0 1.8 2.0 2.6 3.0

PERCENTAQE REFLECTANCE (IN OIL)

 A G E ( M i l l i o n y e a r s B.P.)
-- _-
PALEOCENE EOCENE o L I G o c E N- E M to c
EIRLY;LATE IEARLT MIDDLE ]iATEiEARLif LATE 1 EARLY FIT LATE PLClST

60 50 40 30 20 10

DEPOCENTER

40-120 PEAK OIL G E N E R A T I O N

1 2 0 - i a o LATE M A T U R ~ T Y
180-600 4 0 0 ' L PRESERVATION
DEADLINE
600-1000 6 0 " O I L e n E S E R V A T l O N N O T E : SEE TTI MAP FOR DEPOCENTER MODEL LOCATION.
DEADLINE
t i 0 0 0 CONDENSATEIORY GAS

c
w
FIGURE 16 - Top lower Tanjung stage 2TTI map and depocenter burial history/TTI plot. w
134

c
a,
to
E
a,
Y

i
1
I
I
I

I I I I 1 ,
0
a
0
H ! 8 z
c
0
X3QNI N300tlOAH
135
136

H
[TRITERPANES
2
ISTERANES
( C 3 i ) HOPANE ( C 2 7 20SC20R)

WARUKIN OIL

I TANJUNG FIELD
LOWER TANJUNG OIL I
J

FIGURE 19 - Oil gas chromatograph/Mass spectrometer scans.

 137

G C DISTRIBUTIONS
fl-Cl7
WARUKRIO(L8 0
1 - SEEP. L - 3 1 3 8P.136
P * SEEP. L - a i s WELLHEAD
3
4 -.
TAPIAN TWUR-1S
I

TAPIAN TIMUR-14
6
E -- WARUKIN EELATAN-17
WARUUIN SELATAN-10
7
E -- RIRIK-1 . M U 0 EAMPLF A
BIRIU-1. Mu0 SAMPLE C
TANlA-l.BfRAl
10-
11 - SANOUAlbl
W A R W I N FIELD OLENO

0
11 -
T A K * M O ON8

IS- TA-IS.
UAMBKW-2.XEPE
282WZEW
14- TAW3-70. ZS6o~Z1016
16- BA00U-1. M 1 A
18.
17 - .Awl-1. 2 7 1 0
T A M N N O FIELD BLEND

PRISTANE n-C25

QC/MS STEZANE DISTRIBUTIONS

WARUKIN O I L 8 ( C 2 8 20S+20R) SOURCE R O C K S
1: W A W M $ELATAN-1 A n=WARUKIN

FIGURE 20 - Ternary diagram of oil and source extract GC and GC/MS compound distributions.
 TANJUNG OILS D
I = MIYAWA AREA S E E P # I
2 1 K A Y O I T I N - 2 , STAGE 2
3. TANJUNG-58, STAGE I
4 = TANJUNG-76. STAGE 2
5 1 MIYAWA AREA S E E P X P
6 . 8AGOK-I, S T A G E 4
-32 7. B A G O K - I , S T A G E 3

WARUKIN OIL8 0
8 s BIRIK A R E A S E E P
- 31 WARUKIN O I L S 9. B l R l K A R E A O L D W E L L
HEAD SEEP
10. T A P I A N TIMUR- 13
11. T A P I A N T I M U R - 1 4
12. W A R M I N S E L A T A N - 1 7
3 - WARUKIN S E L A T A N - 1 9
14- OANGKAU- 1
5 = T A N T A - I , OERAl L S T .
-30

EXTRACTS
]* TANJUNG F M T
WARUKIN FMT.

- 29 TANJUNG O I L S ,
A = E A R I T O - I . STAG 3
0 : DIDI-I, B T A G E 2
C: COAL OUTCROP, STAGE I/*
O r MARIOU- I,LOWER WARUKIN
E x EANGKAU -I, L O W E R
WARUKIN C O A L .

-28

-27

Key
- 26 0 O I L GROUPS

d' WHOLE OIL ANALYSIS

,
- - - Q - -S-A T U R A T E F R A C T I O N A N A L Y S I S
-25 ,
-25 -26 - 27 - 28 -29

S13C OF AROMATICS

-
FIGURE 21 Barito Basin carbon isotope distributions of oil and source extracts.