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1

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

mailto:[email protected]:[email protected]:[email protected]



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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



5

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



6

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



8

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

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