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UNLOCKING HETEROGENETIC RESERVOIR BY USING SEQUENCE STRATIGRAPHY ON
SANDY FLUVIAL DEPOSITS OF THE MIDDLE BALIKPAPAN FORMATION OUTCROP,
SAMARINDA, KUTEI BASIN; IT’S IMPLICATION FOR RESERVOIR DISTRIBUTION
Rizki Putra Ptratama1
Diponegoro Ariwibowo2
Zakaria Yahya3
Geologiical Student of STT Migas Balikpapan, [email protected]
Geological Student of STT Migas Balikpapan, [email protected]
Geolgical Student f STT Migas Balikpapan, [email protected]
ABSTRACT
Basically, Sequence stratigraphic concept has used for analyses of seismic cross- sections, well logs and
outcrop studies of sedimentary rock are used to predict the thickness, extent of sediment lithology and
understanding sediment geometry changes with relative sea level and rates of sedimentation. The
sequence principles can be applied readily to outcrop sources. This paper will fully discuss the sequence
stratigraphic concept of heterogenetic facies on Gelingseh formation (Balikpapan Group). The data were
collected from the surface outcrops in Simpang pasir area, Samarinda through field geology mapping.
Then we continued to a laboratory analysis of said Miocene outcrops within study area. Several individual
facies, in terms of deposition events, were determined in the study area. There are 8 facies associations
from four stratigraphic logs: 1) Pebbly – Very Coarse Grain Sandstone (Gradding Oriented), 2) Fine
Grain Size – Medium Grain Size Massive Sandstone, 3) Massive Mudstone (Shale Clast), 4) Massive
Mudstone (Silt Clast), 5) Fine Grain – Coarse Grain through cross bedding Sandstone, 6) Fine Grain
– Medium Grain Mud Drapes Associate Cross Lamination Sandstone, 7) Fine Grain – Medium Grain
Laminae Sandstone, 8) Coal Seam. According to the integration of all the individual beds, an analysis of
the vertical stratum succession, with nearly complete sequences, are observed at the outcrops in the study
area. This study has interpreted comprehensive sand deposits in a fluvial deltaic, which will be useful to
encourage future exploration and development.
Keywords: Heterogenetic Reservoir, Sequence Stratigraphy, Fluvial Deposits,
Middle Balikpapan Formation, Kutei Basin
I. INTRODUCTION
Basically, Sequence stratigraphic concept
has used for analyses of seismic cross-sections,
well logs and outcrop studies of sedimentary
rock are used to predict the thickness, extent of
sediment lithology and understanding sediment
geometry changes with relative sea level and
rates of sedimentation. The sequence principles
can be applied readily to outcrop sources.
This study be located at simpang pasir area,
Samarinda, East Kalimantan. This area
includes the northen part of kutai basin (figure
1).
The Kutai Basin formed in the middle
Eocene as a result of extension linked to the
opening of the Makassar Straits and Philippine
Sea (I.R Cloke,et all,1998). Kutai basin is the
second largest Tertiary basin that produced oil
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and gas in Indonesia, with proven reserve
more than 11 BBOE (Corutney, et al., 1997).
More than 85% reserve is located in the Middle
Miocene sediment. Subsequent tectonic events
uplifted parts of the basin margin by the late
Oligocene. This uplift was associated with the
deposition of the Sembulu Volcanics in the
eastern part of the basin.
The second stratigraphic phase was
contemporaneous with basin uplift and
inversion, which started in Early Miocene time.
During that time, a vast series of alluvial and
deltaic deposits were deposited in the basin.
They comprise deltaic sediments of the
Pamaluan, Pulau balang, Balikpapan and
Kampung Baru Formations, prograding
eastwards, which range in age from the Early
Miocene to Pleistocene times . Deltaic
deposition continues to the present day, and
extends eastwards into onshore Kutei Basin
(figure 2).
II. REGIONAL GEOLOGY
The Kutai Basin is bounded by the
Paternoster platform, Barito Basin, and the
Meratus Mountains to the south, by Schwaner
Block to the southwest, the Mangkalihat high to
the north - northeast, and the Central Kalimantan
Mountains to the west and north (figure 3).
Kutei Basin has a complex history (Moss et al.,
1997), and is one of the only Indonesian basins
to have evolved from a rifted internal
fracture/foreland basin into a marginal-sag.
Much of the early basin fill in the Kutei
Basin has been inverted and exposed (Satyana,
1999).
The basement uplift of Kuching High and
inversion from upper Kutai Basin contributes
erosional debris from previous sediment,
accumulating thick. progradational deltaic
system to east and south direction. Oligocene
subsidence and sag were followed by inversion
of the early Kutai Basin fill along its initial
boundary faults in the early Miocene, resulting
in the erosion of several thousand meters of the
synrift sequence.
The structural pattern of South Kutai
Basin is characterized by the presence of NW-
SE fault trends that are almost perpendicular to
the central Kutei Basin structural trend
.Three major faults (from SW to NE and from
the oldest to the youngest) are Maruat, Tunan,
Sesumpu - Jumelai and Sepinggan Faults
(Syarifuddin et al., 2008).
III. SAMPLE AND METHOD
This paper will fully discuss the sequence
stratigraphic concept of heterogenetic facies on
the Middle Balikpapan formation. The data
were collected from the surface outcrops in
Simpang pasir area, Samarinda through field
geology mapping. Then we continued to a
laboratory analysis of said Miocene outcrops
within study area.
The outcrop data will be used as an analog
to the subsurface data to understand the lateral
stratigraphy distribution and reservoir
characterization. The startigraphy succession
and stacking pattern in the subsurface has the
similarity to the outcrop sediments at the same
age in the Mahakam Delta. And a surface
geological map of Samarinda Area by S.
Supriatna, Sukardi dan E Rustandi was used to
identify formation outcrop location (figure 4)
IV. DATA AND ANALYSIS
Outcrop Data
Lithofacies analysis
A number of different depositional
environments exist in any sedimentary basin.
These environments represent local variation in
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physical, chemical and biological conditions as
well as distance and direction from depositional
agents entering basin (e.g. a river and its
delta). At any moment sediments being
deposited may be correlated with local
depositional environments. These lateral
variations are termed sedimentary facies.
Lithofacies is a body of rock characterized by
particular combination of lithology, physical and
biological structure that bestow an aspect
different from the body of rock above, below
and laterally adjacent.
Based on the outcrop studies, there are 8
lithofacies that represent particular characteristic
Facies association analysis Constitute several
facies that occur in combination, and typically
represent one depositional environment (tabel
1). The outcrops of the research area are
observed in four stratigraphy profile (Figure 5
and 6).
Outcrop I :
Description : We found this facies to have
several external characteristics. sub-facies of
massive coarse grain sandstone associated
monotoneous interbed of massive siltstone and
laminae of fine grain sandstone which had
brownish grey color, sharp and planar bed
contacts, coarsening upwards sandstone unit
averaging 4.95 m in thickness, and ranging up to
9,45 m It has rounded sub- rounded grains with,
medium sorting. These sub-facies were found at
identification point number 1 located in East of
the research area.
This sub facies is associated with other
indicators of structured sediment: Gradded
Bedding and coal lenses. The geometry
Characteristic of this subfacies shows a
monotoneous interbed of massive Siltstone and
sandstone with laminae sedimentary structure.
Anothers we found a sub-facies of monotoneous
interbedded mud drapes in laminae medium
grain sandstone which is associated with a thick
coal seam and shown by a dark color, Blocky
and planar bed contacts, a coarsening upwards
sandstone unit. This sub-facies are found in
observation point number 8 in the East research
area
Interpretation : Numerous grain classes in
the first association facies represent high-
energy deposition with traction of the
bedload (Scholle and Spearing, 1998).
The association facies indicates a braided
fluvial stream (Scholle and Spearing,
1998). Further indications are the clast size,
erosional contacts, the graded bedding
(inverse and normal). Both sandy and gravelly
rocks migrated laterally, leaving sheet-like
or wedge-shaped deposits of channel and bars
complexes, preserving a minor amount of
floodplain materials (Scholle and Spearing,
1998). The depositional environment of this
association facies is likely a channel in a
braided river.
Outcrop II :
Description : We found a sub-facies of
Crossbed, lamination, medium grain
sandstone, associated with alternate massive
mudstone and represented by a brownish light
color, sharp and planar bed contacts, and a
coarsening upwards sandstone unit. It has
rounded to sub-rounded grains, with medium
good sorting. Averaging 5 m in thickness and
ranging up to 7 m.
This sub-facies was found at identification
point number 2 located in the eastern research
area. This has a sedimentary structure of ripple
lamination with a geometry length of 5.2 cm,
mostly with medium-grain sandstone which
was continuous and sinuous. This sub facies is
associated with indicators of sedimentary
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structures such as symmetrical ripple and
crossbed structures.
The geometric characteristics of this sub-
facies show a channels in outcrop (Tucker,
2011) that is influenced from internal
(vertical load) and external forces (erosion
intense). Several beds have interbedded massive
siltstone and sandstone.
Interpretation : According to the properties of
the textural and structural sedimentary rock,
this sub-facies represents a medium energy
deposition of suspension with water (Scholle
and Spearing, 1998) as a sedimentation
mechanism. This sub-facies is in a difference
place than the first sub-facies, it is in the
transition zone of a tide estuary. (Scholle and
Spearing, 1998). Estuary sediment typically
consists of medium-sorted to well-sorted
medium-grain clast to fine-grain clast and
mudstone, two very different types of materials.
The sand may be introduced mostly from the
ocean, while the mud is contributed primarily
from river discharge. Commonly, the mud and
well-sorted sand are interlayered in sharply
contrasting stratum, although intense
bioturbatation may mix the components into a
muddy sand or sandy mud (Scholle and
Spearing, 1998). The depositional environment
of this sub-facies is influenced by the tidal
channel of estuary (Scholle and Spearing, 1998)
Outcrop III :
Description : We found a sub-facies of thick
Flasher lamination fine grain sandstone which is
associated with laminated fine grain sandstone
and thin coal seam and represented by a dark
color, sharp and planar bed contacts, coarsening
upwards to a sandstone unit averaging 13.38 m
in thickness and ranging up to 17.9 m. It has
rounded to sub-rounded clasts, with good
sorting. This sub-facies was found in
identification point number 3 and 4 be located in
the Middle part of the research area.
It shows sedimentary structures of wavy ripple
lamination with a geometric length 4.7 cm,
mostly with silt clast and very fine sand grain.
This sub facies is associated with an indicators
of sedimentary structures such as parallel
lamination with flat bedding, burrow and
muddier lenses.
Interpretation : Based on the textural and
structural sedimentary rock properties, this sub-
facies represents a medium energy deposition
with a traction bed load mechanism (Scholle
and Spearing, 1998) as a sedimentation
mechanism. This sub-facies is in a different
place from the previous sub- facies. The sub-
facies is in the transition zone (tide estuary,
Scholle and Spearing, 1998). The tide
shapes the interiors of most estuaries into a
series of tidal bars and channels. Tidal bars,
where the sediments are generally sands, may
form complicated and frequently shifting
networks. The structure within in this area
develops a wavy lamination structure, sinous
ripple lamination, and cross lamination (Scholle
and Spearing, 1998). The depositional
environment of this sub-facies is influenced by
the tidal bars of the estuary (Scholle and
Spearing, 1998).
Outcrop IV :
Description : We found a sub-facies of trough
crossbed sandstone, planar crossbed with or
without clay nodule at bottom to middle facies,
Laminated siltstone and claystone with or
without bioturbation , Interbedded sandstone
with Flasher bedding, and Intercalated sandstone
within claystone at top facies. Sedimentary
structures in the sandstone include ripple
lamination, wavy, lenticular, and thickening and
coarsening upwards succession unit averaging
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13.1 m in thickness and ranging up to 20.08 m.
The coarsening-upward and thickening upward
nature of the successions indicates an overall
upward increase in flow velocities. The Inclined
nature of the beds and decreasing flow strengths
both along strike and down depositional dip
indicate deposition from a point source in the up
dip direction. We found the other sub facies of
siderite nodule and very fine sand lamination,
carbonaceous, and bioturbated, massive
claystone.
Interpretation : Due the textural and structural
properties of this sedimentary rock, it
represents a high-energy deposition of
traction with a bedload mechanism (Scholle and
Spearing, 1998) with a sedimentation
mechanism in the lower flow regime. The
sedimentary structure formed by a migration
process of sand waves. This structure
was formed in high-energy regime with trough
crossbeds forms and ripples (Ethridge, within
Scholle and Spearing, 1998). The
interpretation is that tides shape the interiors of
most estuaries into a series of tidal bars and
tidal channels. The tidal bars, where the
sediments are generally sands, may form
complicated and frequently shifting networks.
The structure within in this area developed a
wavy lamination structure, sinous ripple
lamination, and cross lamination (Scholle and
Spearing, 1998). The depositional environment
of this sub- facies is influenced by the tidal bars
of the estuary (Scholle and Spearing, 1998.)
V. DISCUSSION
Sequence Stratigraphic Analyses
According to the unity among 8 facies
association through a correlation of
sequences stratigraphic succession, a nearly
complete sequence are identified on the
outcrops in Palaran Area. The sequences
segments are; Sequences Boundary (SB),
Lowstand System Tract (LST), Transgressive
System Tract (TST), Maximum Flooding
Surfaces (MFS) and Highstand System Tract
(HST) (figure 7).
1. Sequences Boundary (SB) Sequences
Boundary is a marker that function as a
type of SB while the first series of sequences
was occurred. This is the main marker
used in stratigraphic correlation and can be
correlated regionally. In the correlation of
stratigraphic succession, sequences boundary
was marks by red line. SB was created between
early lowstand deposit and lately of highstand
deposit.It was bounded by two difference types
of rock and shown an erosional surface in the
outcrop. Due to the outcrop view below the SB
was interpreted as the lowstand deposit of
distributary mouth bar and the upper of the SB
was interpretd as the lowstand deposit that is
distributary mouth bar (prodelta)
2. Lowstand System Tract (LST)
Lowstands System Tract show aggrading
parasequences set and bounded below by
Sequences Boundary (SB). This system tract
was formed while force regression occur or if
accommodation space less than sediment
supply, the deposit of each deposition zone in
the successive parasequences will built out
from the same lateral position as the previos
parasequences. In the sequences correlation
succession lowstands system tract. The system
tract was developed during a still stand phase of
relative sea level.
3. Transgressive System Tract (TST)
Transgressive System Tract show
retrograding of parasequences set that was
bounded at top by Maximum Flooding
Surfaces (MFS). This system tract formed if the
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increase in accommodation space is greater
than the constant rate of sediment supply, so
the deposit of each depositional zone in the
successive parasequences will shift landward
relative to those in the parasequences below
it. The transgressive system tract was deposited
after transgressive surface had been formed. In
the sequence correlation successive
transgressive system tract.
4. Highstand System Tract (HST)
This deposit from the outcrop could
recognize High Stand System Tract formed by
progradding system of parasequences set. This
system tract was bounded by SB at the top
surfaces. HST was formed if accommodation
space greater than sediment supply. This
deposit was interpreted as the latest cycle of
sequences and was known as the regressive unit.
5. Maximum Flooding Surfaces (MFS)
Maximum Flooding Surfaces is the one of
important markers of sequences
stratigraphy correlation although it can used the
sequence boundary as the main tool
parasequences. It had characteristics a periods of
maximum relative sea level rise and
maximum transgression and related closely to
condensed section. MFS can recognize from
thick mudstone.
VI. CONCLUSION
Field observation suggest 8 facies association
from four stratigraphic Outcrop: 1) Pebbly –
Very Coarse Grain Sandstone (Gradding
Oriented), 2) Fine Grain Size – Medium Grain
Size Massive Sandstone, 3) Massive Mudstone
(Shale Clast), 4) Massive Mudstone (Silt Clast),
5) Fine Grain – Coarse Grain through cross
bedding Sandstone, 6) Fine Grain – Medium
Grain Mud Drapes Associate Cross Lamination
Sandstone, 7) Fine Grain – Medium Grain
Laminae Sandstone, 8) Coal Seam.
VII. ACKNOWLEDGEMENT
The Author would like thank to Geological
Department of Sekolah Tinggi Teknologi
Minyak dan Gas Bumi (STT Migas) Balikpapan
and SM IAGI STT Migas Balikpapan for their
support.
REFERENCES
Allen, G.P. dan Chambers, John L.C., 1998, “Sedimentation of The Modern and Miocene Mahakam
Delta”, Indonesian Petroleum Assosiation, Jakarta.
Emery, D. and Myers, K. J., 1996, “Sequence Stratigraphy: Blackwell Science” Ltd.
Mora, W., Gardini, M., Kusumanegara, Y., Wiweko, A., 2001, Modern, Ancient Deltaic
Deposits an Petroleum System of Mahakam Area: Indonesian Petroleum Association Field
Trip.
Payenberg T. dan Lang S., 2003, “Reservoir Geometry of Fluvial Distributary Channels-Implications
for Nortwest Shelf, Australia, Deltaic”.
Satyana, A.H., Nugroho, D., Surantoko, I., 1999, “Tectonic controls on the hydrocarbon habitats of
the Barito, Kutei, and Tarakan Basins, Eastern Kalimantan, Indonesia”, Journal of Asian Earth Science Special Issue, v.17.
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Tabel 1. : Lithofacies Identification From The Palaran Stadium Outcrop.
Lithofacies Number
Lithofacies Name
Grain Size
Characteristic of Lithofacies
1
Pebbly –Very Coarse Grain Sandstone
(Gradding Pattern)
Pebble – Very Coarse Size
This Lithofacies separate into 2 part and it’s alternate with the conglomerate. The thickness in lower bed
surface is around 28 cm and the upper bed surfaces is
around 39 cm . It’s show a coarsening upward bedding
structure in several surfaces beds, ungraded patern
2 Fine Grain Size – Medium Grain Size
Massive Sandstone
Fine – Medium Size 345 cm with burrowed fossil in the upper bed, cross bedding and flasher bedding in the lower bed
3 Massive Mudstone (Shale Clast) Mud Size (Shale) Thinly massive mudstone (shale clast) trough 15-25 cm
4 Massive Mudstone (Silt Clast) Mud Size (Silt) Thinly massive mudstone (silt clast) trough 18-29 cm
5
Fine Grain – Coarse Grain through
cross bedding Sandstone
Fine – Coarse Size
220 cm in thickness nodule and clay fragmen in lower bed surface, 520 cm in a middle of bed surface with
crossbedding structure, 123 cm with clay lamination
6 Grain – Medium Grain Mud Drapes
Associate Cross Lamination Sandstone
Fine – Medium Size 105 cm in thickness trough a mud drapes with a geometry irregular undulating mud laminae (tucker)
7
Fine Grain – Medium Grain Laminae
Sandstone,
Fine – Medium Size
24 – 65 cm in thickness trough of laminae structure. The intercalated with thin clay size and it’s has geometry
length 540 cm
8
Coal Seam 80-120 cm in thickness, dull to bright, brittle and non
banded
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Figure 1. Location of Study Area.
45 m
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Figure 2. Regional Stratigraphy of Kutai Basin (Satyana, 1999)
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Figure 3. Regional geology of Kutai Basin (Allen and Chambers, 1999)
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Figure 4. Geological map of Samarinda Area, focused area study is marked by red box (S. Supriatna, Sukardi dan E Rustandi, 1995).
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Figure 5. Stratigraphy profile on ountcrop 1 (left) and outcrop 2 (right)
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Figure 6. Stratigraphy profile on ountcrop 3 (left) and outcrop 4 (right)
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Figure 7. Composite stratigraphic coloum and sequence stratigraphy unit analysis.
45 m