Seismic Atlas of SE Asian Basins

North Sulawesi Basin

2011-11-03T06:01:00.000+01:00

Sulawesi Sea and its surrounding area is an active tectonic region. Many studies were done to understand the tectonics in this area. For this reason, several seismic vintages were acquired in the Sulawesi Sea (Celebes Sea) area. The seismic lines were published in: 1977 by Hinz: single multichannel reflection seismic (MRS) profile 1979 by Hamilton: single trace reflection seismic lines 1987 by Hinz and 1989 by Fechner: seismic data acquired by SONNE-cruise 49 in Mindanao area, at the eastern end of the Celebes Sea Basin. 1994 by Zen and Hinz: seismic data acquired by SONNE-cruise 94, sponsored by German institutions. 1997, by Beiersdorf et al.: seismic data acquired by SONNE-cruise 98 which also did geological and geochemical investigations.

This article shows the seismic expressions in the southern margin of the Sulawesi Sea, which is the subduction zone in the north of Sulawesi North arm and known as North Sulawesi Trench (Fig. 1)

Regional Tectonics

Regional cross section in Figure 2 shows the subduction of Sulawesi Sea oceanic late to the south and goes underneath the northern arm of Sulawesi which is dominated by calc-alkalic potassic (CAK) volcanic material. This section is constructed by Walpesdorf et al. (1998) based on seismic epicenters.

The seismicity of this area is very high and occurs in wide range of depth. Figure 3 shows the distribution of epicenters recorded by USGS. Close to the northern coast of Sulawesi, the seismicity is relatively shallow and it is getting deeper southwards. This evidence supports the regional cross section in Figure 2 is recorded by USGS in the seismicity map in Figure 3.

Fig. 3. USGS seismicity map of the study area

Seismic Sections

RV SONNE vessel cruises 98 acquired regional seismic sections across Sulawesi Sea Basin. One of the north-south sections displayed in Figure 4, shows general deepening of Sulawesi Sea basin to the south. The Miocene horizons clearly go beneath the thrusted zone or the accretionary complex in the north of Sulawesi.

From 2 November 1994 to 14 December 1994, RV SONNE vessel acquired seismic data in the north Sulawesi trench. The survey was chiefed by M. T. Zen (BPPT-Indonesia) and K. Hinz (Germany) who aimed to : Study the structure, the age and the geological evolution of Sulawesi Sea. Study the tectonic framework of the North Sulawesi and Mindanau continental margin which is still active. Understand the mechanism of the formation of the accretionary prism at the back zone of North Sulawesi and the west of Sangihe Island.

Two seismic sections were published as shown in Figure 5. These condensed sections shows relatively low angle of subduction beneath a 60 km accretionary complex. Overall the system has a steep dip subduction

zone. The structures formed part of the sea bottom, which indicates

Present day or recent tectonics activities. These evidences confirm USGS seismicity maps. Sediment supply from the onshore Sulawesi is also active. Line 28 shows an indication of recent sediment accumulation in the south of the section. Line 30 shows a steeper slope in the south of the section which may also caused by sediment supply from onshore Sulawesi.

A detail section of line SO98-28 displayed in Figure 6 shows the oceanic crust which is overlain by Middle Miocene turbidites and Latest-Miocene to Pliocene clastic interval go beneath the accretionary complex in the south. This complex composed of intense south dipping thrust faults. The faults are getting deeper from north to south and at the same time generating more complex features.

Conclusions

The studies in this area conclude that the structures are clearly shown in the front end of the accretionary zone because they are relatively young. Further south the structures are less pronounced as they have gone through more tectonic phases, the reflectors become too complex to be imaged by seismic. With limited and low data resolution, significant structure growth on seismic section which indicates fault timing is not well observed.

Some of the structures also offset the sea bottom, which indicates a relatively new fault or still on-going fault reactivation. This evidence support USGS seismicity map which show recent and active tectonic activities.

What is new

2011-02-22T21:19:00.003+01:00

Feb 2011: Sumatra Forearc and Andaman seismic
Jul 2011: Baram Basin seismic (Cullen, 2011)
Oct 2011: North Sulawesi Basin (Darman, 2011)

Introduction

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Proposal and invitation to potential contributors

BackgroundMany good quality seismic lines were acquired from Southeast Asia basins, showing world class geological features. Those data are scattered and / or not easily accessed by public users. This atlas open the opportunity for geoscientists to see interesting seismic features in this region in one integrated volume, with their geological backgrounds.

Team (Contributors and Reviewers)
Anantasena - BPPT - Indonesia
Andrew Cullen - Chesapeake Energy, Oklahoma City, OK, USAAwang Satyana - BPMIGAS - Indonesia
Dieter Franke - BGR - Germany
Duddy Ranawijaya - Geo Marine Survey - Indonesia
Harry Doust - Amsterdam Univ. - Netherland
Henry Posamentier - CHEVRON - USA
Herman Darman - SHELL - Netherland (chief editor)
Kjell Johansen - PGS - Singapore
Minarwan - REPSOL - Spain (co editor)
Owen Dyer - FUGRO - Australia
Peter Baillie -TGS NOPEC - Australia
Ridwan Djamaluddin - BPPT - Indonesia

Roberto Fainstein - WesternGeco - India
Robert Hall - Royal Halloway - UK
Sigit Sukmono -ITB - Indonesia
Simon Irwin - PGS - Indonesia
Steve Toothill - CGGVeritas - Indonesia
Wietze Van Der Werff - Shell Brunei
Yusuf Djajadihardja - BPPT - Indonesia

Note: The name list above is on alphabetical order by first name. If you prefer us not to display your name, please contact the coordinator: Herman Darman

Publication
In the first phase, the seismic sections will be displayed in this website. The team will contribute their interpretations and comments on the sections compiled.

Once significant quality and quantity images compiled, the committee aimed to publish A3 size hard copies with colors and/or in CD format. Each basin will be covered in atlas chapters with minimum 2 pages and maximum of 6 pages of A3 paper (landscape orientation), see below the template and example of this potential publication. Contributors are expected to send seismic sections, location map of the sections, related well information if available, regional geological map and cartoon cross section, 3D model etc.

Currently the team is investigating potential publisher for the atlas.

Template

For proposed template for the A3 publication, click here

For example of the atlas, click here

Data Provider

The data published in this website came from different sources, mainly published literature. Some data provider provide published seismic images, and the web editor would like to thank the following companies:

Philippines Basin

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Luconia Basin

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Luconia Basin is located offshore Sarawak, Malaysia

NW-SE seismic profile across Luconia Platform and Mid. Miocene Balingian Delta and rift in deewater. Rectangle shows location of the following seismic line (Source: Thies et al., 2006)

Detail of part of seismic line above, showing listric fault bounding half graben, with rift and post-rift deposit (Source: Thies et al., 2006)

Seismic line showing rift cycles in half graben.

Seismic line CD89-110 (Mulu-1 Tie Line) showing log of Mulu-1 and rift cycles 1 and 2 on horst.

Reference: Structural and Stratigraphic Development of Extensional Basins: A Case Study Offshore Deepwater Sarawak and Northwest Sabah, Malaysia, By: Kenneth Thies, Mansor Ahmad, Hamdan Mohamad, Richard Bischke, Jeffrey Boyer, and Daniel
Tearpock, Search and Discovery Article #10103 (2006)

Vietnam Basins

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Two example of seismic sections of Vietnam Basins: Song Hong, Phu Khanh, and Cuu Long Basins (source AAPG).

A seismic from Vietnam shallow water to deeper offshore showing relatively steep slope.

Gorontalo Basin

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Image courtesy: Fugro

Gorontalo Basin is located under the Tomini Bay and is limited by the neck and the north and east arms of Sulawesi Island. The basin opens to the east towards the Molucca Sea. Water depth in the basin ranges from XXXx to XXXX m and sediment thickness is up to about 7 km. The basin still lacks hydrocarbon exploration activities at the moment, therefore there is no accurate information about the ages of basin-fills.

Regional tectonic reconstruction of Hall (2002) shows that part of the proto-Gorontalo Basin was most likely located in a fore-arc setting since Middle Eocene to Early Miocene, with the arc being the north arm of Sulawesi.

More to be added...

SW West Java Basin

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The western Indonesian fore-arc basins extend more than 1800 km from northwest of Aceh to southwest Java. The width of the basins varies from less than 70 km south of the Sunda Strait to about 120 km in the west off northern Sumatra. The basins form a strongly subsiding belt between the elevated Sumatra Paleozoic–Mesozoic arc massif cropping out along Sumatra and Java, and the rising outer arc high.

(Contributor: Dieter Franke, BGR)

Seismic Sections:
Figure 1. Location map of line ABB-SO-137-31, south of Banten, West Java.

Figure 2. NW-SE oriented uninterpreted section of line ABB-SO-137-31. Data courtesy: BGR

Figure 3. Interpreted section of line ABB-SO-137-31. Data courtesy: BGR

Figure 4. Location of line ABB-SO-137-36

Figure 5. SW-NE orientation seismic line ABB-SO-137-36. Data courtesy: BGR

Figure 6. Interpreted seismic line ABB-SO-137-36. Data courtesy: BGR

Data Provider

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The main data provider for this online atlas are:

The committee are thankful for their contributions

Sabah Basin

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Sabah Basin is the northern extension of the Baram Basin in Northwest Borneo. Two seismic NW-SE orientation seismic sections are displayed in this chapter.

The Dudar seismic profile indicate a relatively smooth sea bottom. The upper sequence is getting thinner towards the basin. The shelfal part is not shown much on this section.

The shelfal part of the Sabah basin has a shallow and relatively flat sea bottom. On the slope there are several topographic highs and lows created by erosional processes and structures.

Major folds and faults developed at deeper level.

Sandakan Basin

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Sandakan Basin is located in the northern part of Borneo Island. Similar to other circum-Borneo basins, the Sandakan Basin is dominated by shallow to deep marine clastics sequences.

Foreset features of Sehabat Formation, indicating sediment transport from NW to SE. Source: Petronas 2000 in Tate, 2001.

A scetch of a seismic section across Manalunan-1 well which penetrated the Sehabat formation (Modified after Wong, 1993)

NW - SE orientation seismic section

shows Pad Basin which is bounded by 2 flower structure system (Source: Petronas 2000 in Tate, 2001)

Natuna Sea and Sarawak Basin

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The Natuna Sea area is the southern extension of the South China Sea, mainly in the Indonesian territory. This area is divided by two parts by Natuna Arch, namely West Natuna Basin which extend to Malay Basin in West Malaysia and East Natuna Basin which extend of Sarawak Basin in East Malaysia

The West Natuna Basin was formed as an intra-continental rift basin within the Sunda Platform, the southern margin or Eurasian Plate. The basin has undergone Eocene-Oligocene extension, followed by Miocene to present day contraction and inversion.

In Late Cretaceous-Early Eocene reconstruction, East Natuna Basin was part of a large fore-arc basin extending from offshore Veitnam, across Natuna Sea to Sarawak. The SW-NE trending structures in East Natuna Basin are controlled by extensional faults and half grabens similar to the ones found in West Natuna Basin, but the rift magnitude is generally less than the ones in the West Natuna Basin.

West Natuna Seismic Sections
Seismic reflection section over the Anambas graben. Tectonic inversion over the graben occurred during the Miocene. Brown marker is the top Oligocene, Gabu formaion wheras the blue marker represents the Pliocene unconformtiy after inversion. The bright spots near basement may represent lacustrine source rocks with high TOC. Source: Fenstein, 2000.

Play concepts for West Natuna basin (Netherwood,2000, after Fainstein and Meyer, 1988)

East Natuna Seismic Sections

Seismic reflection section of East Natuna. No inversion occurs in this area. Blu marker represents top of carbona te reservoirs. Bursa is an oil field and Alpha-D is teh giant Natuna gas field (source: Fainstein, 2000).

Play concepts for East Natuna basin (source: Netherwood, 2000, after Fainstein and Meyer, 1998)

Makassar Basin

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Geographic location: Makassar strait, between Borneo and Sulawesi Island.

Water depth: 200- 3000 m

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Southeastern part of Makassar Basin:
Deepwater fold belts
Source: Baillie et al, 2005

.

Central part of Makassar Basin:
This section shows the transition from the Kutei Basin at the shallower water to the Makassar Basin at the deeper basin.
Major growth fault is seen on the west. Young structural feature exposed to the sea bottom at the centre of this section.
Source: Baillie et al, 2005

Northern part of Makassar Basin
This seismic section goes through the Palu-Koro major strike slip fault, which generated significant sea bottom relief in this part of the basin.
Source: Baillie et al, 2005
.

Zoom in on the submarine Palu-Koro fault reliefs.

Source: Baillie et al, 2005

South Sumatra Basin

2008-11-13T21:12:00.006+01:00

The South Sumatra Basin is most southern back arc basin of Sumatra Island.

Two seismic sections of Kaji and Semoga Field are displayed here:

Section A went from West to East, crossing both Kaji and Semoga Field.

The lowest horizon in red is the top of the granitic basement. Both Kaji and Semoga Field are consist of carbonate reefs of Baturaja Formation, which built on top of basement high.

Section B is a North-South section across Kaji Field. Generally the basement is getting deeper southward in this part of the basin.

Central Sumatra Basin

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General Information

Water depth:

Area:

Age range:

Basement type:

Main tectonic events:

Petroleum system:

Source rock:
Reservoir:
Trap:
Hydrocarbon type:

Basin type:

Key references:

Geoseismic Sections:

Timor Sea

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Seram Trough

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Geographic location: between Banda arc and Papua Island, west of Misool-Onin Ridge.

Water depth:

Area:

Stratigraphy:

Basement type:

Image courtesy: Fugro

North East Java Basin

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NE Java Basin is a back arc basin offshore East Java.

Fold features in the south of Madura Island. The fold in the centre is not a simple anticline, as it may be cut by faults. (Source: Fugro)

Bright amplitude in the centre are related to topographical high, may indicate carbonate build-ups. The sequences are pinching out to the right, and truncated by a shallower unconformity. (Source: Fugro)

The centre part of the faulted anticline feature is slightly thicker compare to the flank, as several sedimentary packages developed towards the core of the anticline. This indicate that the central of the anticline was a sedimentary pocket, probably created by the fault on the left. At later stage these depocentres were uplifted. (Source: Fugro)

Carbonate features of Kujung Formation (Source: Fugro)

Slightly rotated faulted blocks at the basin margin (Source: Fugro)

Steep-dipping Kujung carbonate reef flanks, indicated by arrows. (Source: PGS)
Time slice at 0.15s TWT showing complex meandering channel system. Horizontal scale scale is about 15 km. (Long and Johansen, 2003; data source: PGS)

Time slice at 1.0 s TWT showing the carbonate features. The diameter of the karst feature is probably less than 1 km. (Long and Johansen, 2003; data source: PGS)

3D perspective of the Top Kujung surface about 1.0 s TWT, revelas the density and complex distribution of carbonates throughout the HDMC3D survey area. (Long and Johansen, 2003; data source: PGS)

Arafura Sea

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North West Java Basin

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Baram Basin

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Baram Basin is located in the northeast of Borneo, partly in Malaysia and the majority of Brunei offshore. Three major fields were discovered in the shallow water and onshore part of this basin called Champion, SW Ampa and Seria.

To southwest the Baram Basin is bounded by West Baram Line, to the north by Northwest Sabah Trough and to the east by the Sabah Inboard.

Regional seismic cross section in the western part of Baram Basin. SW Ampa Field is anticline is located in the east, shown on the seismic section as a large anticline. A large down-to-basin fault developed in the west of Gannet well. Merpati is a gas discovery in the deep water play of Baram Basin. Several other large anticlininal features developed in the slope of part of the Baram Basin, mainly consists of deep water deposits.

(Modified from Sandal, 1996 by Tromp).
Regional seismic section in the eastern part of Baram Basin. The Champion Field is located in the east, shown in the seismic section as a large structural high. Frigate counter regional fault developed almost at the center of the cross section. Large anticlinal features developed in the west at the slope part of the Baram Basin. The basinal part of the basin has less structure. See below a close-up section of the Champion Field section.
A close up seismic section of the east regional seismic section, showing some detail of the Champion Field. There are two down-to basin growth fault in this area, so called Sliver Fault and Champion Growth Fault. Poorer seismic image beneath the Champion structural high is interpreted as a shale diapir. Recent data, however, give better imaging on the deeper part of this section.

Detail seismic section of anticlinal features which formed by thrust faults (toe-thurst anticlines) in the deeper water part of Baram Basin. The structure on the left has a flat spot which indicate some hydrocarbon content.

The section also show a relatively shallow unconformity below the sea bottom. A shale dominated transparant zone draped over the two anticlines. Seismic courtersy: PGS
Time slice of the deeper water part of the Baram Basin. The anticlines are clearly shown as oval features. The transparant part are the shale dominated interval at the shallower section of the anticlines. (Image courtesy: PGS)

Another sample of time slice at shallower level (Image courtesy: PGS)

The transparant interval is a shale formation, often called the 'transparant shale' sequence.

Potential hydrocarbon indicator at the core of the anticline. (Seismic courtesy: PGS)

Cullen (2010) has devided the NW Borneo offshore basin into several structural segments. Segment A, B and C are parts of Baram basin and D is under Sabah basin.

The hinterland of the Baram Basin consists of two contrasting types of bedrock. The hinterland of the southwest part of the basin is dominated by the shales of the Setap and Temburong Formations; whereas the hinterland of the northeast part of the basin is dominated by sandstones of the Crocker Formation. These relationships suggest that the large drainage systems of the Baram and Padas Rivers represent mud-dominated vs. sand-dominated delivery systems to the basin.

Along strike (SW to NE) differences in the structural style of both the shelf and deepwater areas of NW Borneo define four transverse structural domains in the Baram Basin. The B-C and C-D domain boundaries appear to be basement controlled, whereas the A-B boundary is interpreted to reflect differences between the Baram and the Padas- Champion depositional systems (Cullen, 2010). The deepwater structures in Domain A are characterized by high amplitude, symmetric, detached folds (Figure A). The deepwater parts of Domains B and C are dominated by asymmetric fault-propagation folds that ultimately root into a common detachment level (Figure B). The structural style of Domain A likely reflects the presence of low strength, possibly overpressured, mud-rich rocks that deform by penetrative bed-parallel slip (Erslev and Hennings, 2003), which is consistent with a provenance of the shale-prone hinterland for the Baram Delta.

The deepwater sediments in Domains B and C are derived primarily from the Padas River catchment where the bedrock geology is dominated by sandy turbidites of the Crocker Formation. The fault propagation folds in the deepwater area of Domains B and C suggest a stronger mechanical stratigraphy than in the detached folds of Domain A, which is consistent with a higher percentage of sandstones in Domains B and C owing to a provenance in the Padas River catchment. Although differences in the total amount of strain in different domains of the NW Borneo fold and thrust belt may account for some of the differences in the structural styles between domains, lithology and layering represent more fundamental controls on such interrelated variables such as the strength of basal detachment, the coefficient of internal friction and the critical taper angle.

Thus, differences in the sand to shale ratios in the hinterland of the NW Borneo fold and thrust belt fold thrust belt potentially offers an example of hinterland control on the structural style of deepwater fold and thrust belts.

Seismic lines from structural Domains A and B illustrating the different structural styles in the deepwater fold and thrust belts of those domains. MMU is a Middle Miocene unconformity above which a regional detachment level appears to represent a mechanically weak decollement (Cullen, 2011).

Andrew Cullen's full article has been published in Berita Sedimentologi #22, 2011:
http://www.iagi.or.id/fosi/files/2011/06/FOSI_BeritaSedimentologi_BS-21_June2011_Final.pdf

Tarakan Basin

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Geographic Location: Northeast of Borneo Island

Water depth: Partly onshore, down to more than 3000 m

Hydrocarbon potential: Gas and Oil

Main reservoir target: Tarakan and Bunyu Formation (Pliocene and Upper Miocene interval)Main reservoir facies: Deltaic setting

Main source rock: Type III source rock in the Miocene and older interval

Significant geological features in the basin:

1. Tarakan Arches
2. Paleo Tarakan Delta Foresets

1. The Tarakan arches

The Tarakan arches are the most outstanding structural features in the western part of Tarakan Basin. Petroleum accumulations occur in these arches.

Each of the arches are named after the islands formed on the surface: Tarakan, Bunyu and Ahus anticlines. Sebatik anticline in the north is not covered by this seismic section. Oil and gas accumulation occur in the Tarakan and Bunyu Island

A quick look at these arches on seismic will give the impression that these arches are a series of simple anticlines and synclines. Detail evaluation indicate strong strike-slip components in these structural features.

Source: Lentini, M. & Darman, H., 1997; Wight, A., 1995

2. Paleo Tarakan Delta Foresets

Foresets are clearly seen on seismic section for Pleistocene to Upper Miocene sections. In some sections there are carbonate layers close to the top of the sand sequence, indicating the end of sand supply on that interval.

This seismic section is about WE orientation in the southern part of Tarakan Basin shelf. The yellow units are sand dominated sequence and the blue units are carbonate layers.

The faults are dipping towards the west and the fault system on the right are counter regional faults.

Source: Lentini, M. & Darman, H., 1997

Kutei Basin

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Geographic Location: East of Borneo Island

Water depth: Partly onshore, down to more than 3000 m. The deeper water part is also known as the Makassar Strait basin.

Hydrocarbon potential: Gas and Oil

Main reservoir target: Balikpapan Formation (Pliocene and Upper Miocene interval)

Main reservoir facies: Deltaic setting

Main source rock: Type III source rock in the Miocene and older interval

Significant geological features in the basin:
1. Samarinda Anticlinorium onshore
2. Paleo Mahakam Delta Foresets offshore.

Samarinda anticlinorium map, showing the NNE-SSW trend anticlines and structures in dashed red line. The location of the seismic line across this area is shown in black line.

A highly squeezed regional seismic line (40 km long), crossing four major aniclines within the Samarinda Anticlinoium. In the absence of palaeontlogical data correlation across these anticlines is very difficult (dips vary from 0-75 degrees). Cores of anticlines appear to be chaotic on seismic (1) and bounding faults (2) are difficult to pick. Also visible are down-to-basin syn-depositional faults (3), west-to-east progradational downlaps (4) and evidence of syn-depositional structuring (5) indicating that uplift was occuring at the end of the Early Miocene (from Carter and Morley, 1996).

A detail seismic section across Separi anticline with detail seismis character of the structure. Note the higher topographical relief at the core of the anticline, indicating the location of outcrops. The outcrops are dominated by deltaic sandstone-shale facies and limestones beds.

North Sumatra Basin

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Figure 1.

Location of offshore North Sumatra Basin and seismic lines shown on this page (after Tsukada et al 1996).

General information:

Geographic location: North of Sumatra Island
Water depth: 20 to 500 meters
Hydrocarbon potential: proven oil and gas basin with predominantly gas.
Largest field in the basin: Arun Field (Discovery: 197?)
Main reservoir target: Peutu, Baong and Keutapang Formations
Main reservoir facies: Miocene carbonate reef / build up.
Main source rock: Bampo Formation

Figure 2.

Geoseismic Line BLD-JAU showing northwesterly dipping half grabens filled by the Late Oligocene sediments that underlie the P22 SB. The P22 SB represents a boundary of major shift in depositional environments from a fluvial setting below the SB to a bathyal setting above the SB (Tsukada et al. 1996).

Figure 3.

Geoseismic Line ITU-BLD showing a young overthrust front (see annotation) located in the deepwater offshore North Sumatra. The syn-rift megasequence was deposited above half grabens and tilted fault blocks as shown below approximately 4 s (overlain by the P22 SB). Evidence of tectonic inversion is shown by the folding of the P22 SB, N14 SB and other younger reflectors that was controlled by the half graben (after Tsukada et al. 1996).

Figure 4.

Geoseismic Line ITU-JAU shows Jambu Aye Utara Ridge (JAU Ridge) located on the northeastern side and the NW extension of the North Lho Shukon Deep (Tsukada et al. 1996). The Lho Shukon Deep is the main source rock kitchen that supplies gas to the surrounding major fields such as the Arun Field.

Sumatra Fore-arc Basins

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The western Indonesian fore-arc basins extend more than 1800 km from northwest of Aceh to southwest Java. The width of the basins varies from less than 70 km south of the Sunda Strait to about 120 km in the west off northern Sumatra. The basins form a strongly subsiding belt between the elevated Sumatra Paleozoic–Mesozoic arc massif cropping out along Sumatra and Java, and the rising outer arc high.
Description of the data examples from SW Sumatra is found in Susilohadi, S., C. Gaedicke and A. Ehrhardt, 2005. "Neogene structures and sedimentation history along the Sunda forearc basins off southwest Sumatra and southwest Java." Marine Geology 219(2-3): 133-154.
Schlüter, H.U.,Gaedicke, C., Roeser, H.A., Schreckenberger, B., Meyer, H., Reichert, C., Djajadihardja, Y., Prexl, A., 2002. „Tectonic features of the southern Sumatra–western Java forearc of Indonesia." Tectonics 21 (1047), 11-1–11-15.
Description of the data examples from NW Sumatra is found in
Berglar, K., C. Gaedicke, R. Lutz, D. Franke and Y. S. Djajadihardja, 2008. "Neogene subsidence and stratigraphy of the Simeulue forearc basin, Northwest Sumatra." Marine Geology 253(1-2): 1-13.

Contributor: Dieter Franke (BGR)

Fig. 1. Location map of BGR seismic line: bgr06-105 and bgr06-135 in the west of Sumatra Island.

Fig. 2. Uninterpreted SW-NE seismic line: bgr06-105. Data courtesy: BGR

Fig. 3. Interpreted SW-NE seismic line: bgr06-105. Data courtesy: BGR

Fig. 4. Uninterpreted SW-NE seismic line: bgr06-135. This line is situated in the south of Simelue Island. Data courtesy: BGR

Fig. 5. Interpreted SW-NE seismic line: bgr06-135. Data courtesy: BGR

The Great Sumatra Earthquake three years on: results from the Tsunami deep seismic survey using advanced seismic technology
by Gordon Brown, WesternGeco

Petroleum Exploration Society of Great Britain (PESGB Newletter), June 2008

On December 26, 2004, the Sumatra ¬Andaman earthquake, with an estimated magnitude of 9.3 on the Richter scale, was one of the largest ever recorded using mod¬ern seismographic equipment. As it shook the west coast of Sumatra, Indonesia, and proceeded along a fault line at the eastern edge of the Indian Ocean, the earthquake generated a tsunami that focused the world's attention on the devastating power of this natural phenomenon. With estimates of more than 232,000 deaths and 2,000,000 people displaced in 12 countries in South Asia and East Africa, the impact of th

e tsunami was truly global.In contrast to the devastation inflicted by the tsunami when it reached land, the passage of the tsunami in the Indian Ocean would have gone unnoticed by vessels at sea. One such vessel in the path of the tsunami wave was the WesternGeco survey vessel Geco Topaz. Although not apparent to the ship's crew, the effect of the tsunami was recorded as inter¬ference noise on the recordings made by the seismic crew. Figure 1. shows the effect this noise had on the online brute stack processed onboard Geco Topaz.

Fig. 1 Online Brute Stack

Within days following the earthquake, humanitarian relief poured into the region surrounding the Indian

Ocean. Individuals and organizations around the world offered help in the form of donations and services. On the technology front, Schlumberger offered to support a deep seismic survey around the fault line to improve the under¬standing of the complex tectonics in the region of the earthquake. This survey became known as the Sumatra Earthquake Deep Seismic Reflection survey, or the "tsunami survey". The vessel Geco Searcher, equipped with Q-Marine technology, was used for the acquisition of seismic data in conjunction with Schlumberger Cambridge Research in England and the Institut de Physique du Globe de Paris in France.

In July 2006, the Geco Searcher acq

uired three seismic lines, totaling 926 km of deep seismic profiling. The main objectives of the survey were to image faults along the subduction zone and provide information to optimize the location of a fut

ure borehole for the Integrated Ocean Drilling Programme. Figure 2 shows the survey area and the loca¬tion of the three seismic lines recorded along with bathymetry data. Prior to the acquisition of the seismic data the survey parameters had to be designed to accommodate the depth of the required image. At more than 30km these depths are far in excess of those commonly associated with oil exploration. Major acqui¬sition parameter modifica

tions were required to the offsets (streamer length), recording time and strength of the energy source.

The talk will review the survey design, acquisition and processing of the data along with some suggested interpretations of

the deep crustal profiles. An example of the data is shown in Figure 3.

Fig. 3. Line WG1

Seismic Expression of Some Geological Features of Andaman-Offshore West Sumatra Subduction zone

Herman Darman (Shell International E&P) - Berita Sedimentologi #20, February 2011

A sub

duction zone developed in the south of Myanmar, continue to the Andaman Sea (India), west of Sumatra and south of Java (Indonesia). Two major fault system developed parallel to the subduction zone, so called the Mentawai Fault System and Sumatra Fault system. To the north, where the subduction zone changes its orientation from NNW-SSE to NS, a spreading zone developed towards the east of Andaman Sea (Figure 1). This zone is a complex and active geological system. The 2004 Aceh Tsunami was a major disaster which was triggered in this subduction zone.

The Andaman - Offshore West Sumatra subduction system is where part of the Indo-Australian oceanic plate moving northwards and going b

eneath the southern tip of Eurasian continental plate. Sumatra Island, which is part of Indonesian volcanic island arc, occurs parallel to and inland from the boundary between these two plates. An accretionary prism or wedge has formed from sediments that accreted onto the non-subducting plate. Most of the material in this wedge consists of marine sediments scraped off from the downgoing slab of Indian oceanic plate with some erosional products of Sumatra volcanics. Fore-arc ridge in this system is a chain of islands (e.g. Andaman, Simeulue, Nias, Mentawai, and Enggano), formed by the accretionary wedge. A series of fore-arc basins developed between the accretionary ridge and the volcanic arc (Figure 2).

This region is also an active p

etroleum exploration area. Recently, there are a number of companies (e.g. Spectrum, TGS and Geco) provide new and reprocessed seismic lines to the market. These seismic lines show the geological features in this subduction system.

1. Andaman Section

2010 articles in Geo-ExPro and AAPG Explorer displayed seismic sections of Andaman Sea. These sections were recently reprocessed by Spectrum in 2010 to support exploration licenses by the

Indian authority. The regional seismic section shows a submarine volcanic arc, which separates the back-arc basin from the fore-arc basin. East Andaman fault system developed bathymetric high called ‘invisible bank’ in the middle of the fore arc basin. Part of the fore-arc is shown on the west of the section. Further west of this section the fore arc ridge appear to the sea surface as Andaman Island (Figure 3).

The interpretation suggest Pliocene-Recent stratigraphic interval at the shallowest section. This unit thins in parts due to volcanic activity and fault movement. Neogene units are thicker in the back arc basin compare to the fore-arc basin. The majority of the back-arc basin is deeper than 3000 MSec. TWT.

A seismic section published in AAPG Explorer show a Miocene Limestone unit which this towards the deeper water. The interpretation also indicates a shelf deposit, shelf edge and an isolated shoal (Figure 4). The shelf unit is about 3-4 Msec. TWT deep.

The Neogene unit is underlain by

Pre-Neogene sediments which is thins towards the volcanic arc. In parts the pre-Neogene sequence has been completely eroded away. This unit seems thicken to the west of the section in the fore-arc ridge zone. It is believed that the deeper stratigraphic unit has limited data control.

2. West Aceh Section (Profile Sumenta 32)
A seismic section published by Malod et al is a result of Baruna Jaya shallow seismic survey in 1991. The survey is part of collaboration between Indonesian and France government.

This short section shows a reverse fault which bound the west part of the fore-arc basin (Figure 5). The fault goes all the way to the sea floor at about 3.5 sec. TWT, separating the accretionary prism from the fore-arc basin. The accretionary prism in the SW of this section is clearly shown as a bathymetric high and the fore-arc basin appear as a flat sea base.

The fore-arc basin was filled with Late Miocene and younger deposits. Flat reflectors shows that there were very little tectonic impact on this area despite the major earth quakes and tsunami developed in this region.

Unfortunately the seismic section is too short and too shallow to show the regional picture. The complex geology in the accretionary complex result in unclear seismic expression in this area.

3. Simeuleu Section
In July 2006, Geco acquired 3 deep seismic sections in offshore west Aceh. (Bunting et al, 2007) to image active faults along the subduction zone, quantify the volume of water that penetrated along these faults and provide information to optimize the location of future borehole location for the Integrated Ocean Drilling Program (IODP).

The seismic section is more than 16 sec. TWT deep and show the oceanic Moho on the SW of the section. An indication of continental Moho appears in the NE of the section. The section also shows the trench and the accretionary wedge of the West Sumatra subduction zone (Figure 6).

Slightly to the south of this line, TGS shot some seismic which was focused on the fore-arc basin. The seismic section clearly shows the fore-arc ridge and major regional NW trending fault zone in the SW of the section (Figure 7). In the NE, present day shelf deposit is well imaged. Meulaboh fore-arc basin has thick post late Miocene deposit adjacent to the NW trending fault zone as this fault generate an accommodation space fore about 2 sec. TWT deep.

Conclusion
Recent seismic sections published by Spectrum, Geco and TGS, shows different element of the Andaman-Offshore West Sumatra. Indonesian BPPT Baruna Jaya shallow seismic, acquired in 1991, shows sea bottom profiles which are controlled by tectonic features. These seismic lines clearly show the subsea volcanic arc, accretionary wedge, fore-arc basin, the trench, and boundaries of each element.

Both carbonate and clastic deposits are shown on the seismic sections with indication of potential hydrocarbon.

References
Bunting, T, Chapman, C; Christie, P., Singh, S., Sledzik, J., 2007, The Science of Tsunamis, Oil Field Review, Autumn 2007

Caife, S., Billings, A., 2010, Offshore Exploration of the Andaman Sea, GEO ExPro, vol 7, no. 5.

Durham, L. S., 2010, India Seismic Gets New View, AAPG Explorer, October.

Malod, J. A., Kemal, M., Beslier, M. O., Deplus, C., Diament, M., Karta, K., Mauffret, A., Patirat, Pl., Pubellier, M., Rgnauld, H., Aritonang, P., Zen, M. T., 1993, Deformation fo the Fore-arc Basin, NW of Sumatra, response to oblique subduction, Sumenta Cruiese – Baruna Jaya III – 1991.

Regional Geology

2008-11-11T22:12:00.004+01:00

The Southeast Asia region is situated on a crossroad between two oceans, the Pacific and Indian oceans, and bridges two continents, the Sundaland (Asian) and the Australian (Sahul Shelf). Physiographically, the islands of Sumatra, Java and Borneo are attached to the Sunda Shelf of the Asian continent. On this landmass the water depth does not exceed 200 meters. To the east, Papua Island and the Aru islands lie on the Sahul Shelf, which are parts of the Australian continent. Located between these two shelfal is the island grop of Sulawesi and Halmahera. These islands are encircled by deep seas which in many places reach 5,000 meters. About 70Tertiary sedimentary basins identified in this region, spread out from Myanmar in the west to West Papua in the east. So far about 50 basins have been explored and drilled for petroleum and 20 of the are now producing oil and gas. Seventy five percent of these basins are located offshore, about one third of them in the deeper sea, with water depth exceeding 200 m.