08. Sumatra Petroleum Of Geology

Physiography of Sumatra

Microplate boundaries

Pertamina and Beicip (1985)

Tectonic setting of Sumatra

Simandjuntak and Barber (1996) AWANG H. SATYANA - BPMIGAS

Katili (1975) AWANG H. SATYANA - BPMIGAS

Geodynamic framework of Sumatra subduction

Malod and Kemal (1996) AWANG H. SATYANA - BPMIGAS

Tectonic setting of Sumatra

Darman and Sidi (2000)

North Sumatra Basin

Central Sumatra Basin

South Sumatra Basin

Sedimentary basins of Sumatra

Stratigraphy of Sumatra back-arc basins

Samuel and Gultom (1986)

Murphy (2000)

North Sumatra Basin •

The basin is notable for the first commercial oil field- the Telaga Said field (discovered 1885) and the giant Arun gas field.

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The basin is extremely large and extends from just north of Medan northwards for several hundred kms into the Andaman Sea and across the ThailandIndonesia border.

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The Indonesian sector of the basin is bordered to the west by the Barisan Mountain thrust system and to the east by the stable Malacca platform.

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Onshore sector of the basin has been extensively explored, however, remaining potentials include : gas-filled Peutu carbonate buildups, Belumai buildups on the Malacca shelf, Baong and Keutapang stratigraphic play, lowstand turbidite-fan systems of middle Miocene (Tsukada et al., 1996; Nur’aini et al. 1999), latest Oligocene Bampo fan systems, syn-rift Parapat in graben deeps, Eocene Tampur carbonates (Ryacudu and Sjahbuddin, 1994).

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Relatively unexplored northern deepwater (> 1000 m water depth) sector of the basin merits further investigation.

Awang H. Satyana (2005)

Pertamina and BPPKA (1996)

North Sumatra Basin

Pertamina and Beicip (1985)

Generalized physiography and productive HC discoveries of the North Sumatra basin

Netherwood (2000)

Cross section across Barisan uplift and Southern NSB

Pertamina and BPPKA (1996)

Cross section across North Sumatra Basin Pertamina and BPPKA (1996)

Cross section across NE corner of Barisan uplift

Pertamina and BPPKA (1996)

Davies (1984)

Pertamina and Beicip (1985)

Pertamina and Beicip (1985)

Stratigraphic nomenclature of North Sumatra Basin

Caughey and Wahyudi (1993)

North Sumatra stratigraphy

Davies (1984)

Chronostratigraphic scheme for northern part of the North Sumatra Basin

Stratigraphy and Petroleum System of North Sumatra Basin

Petroleum system of North Sumatra basin

Pertamina and BPPKA (1996)

Pertamina and BPPKA (1996)

Pertamina and BPPKA (1996)

Pertamina and BPPKA (1996)

Pertamina and BPPKA (1996)

Pertamina and BPPKA (1996)

Deepwater North Sumatra Basin

Central Sumatra Basin • The Central Sumatra Basin is the most prolific oil basin in SE Asia. Reserves estimates for the basin of 13 BBOE ultimately recoverable, of which 2.5 BBO remain to be recovered (Sujanto, 1997). • The basin is mature with respect to HC exploration with a simple and essentially single petroleum system operating. • New ideas are required if further fields are to be discovered and trend of declining production to be halted. Awang H. Satyana (2005)

Basement tectonostratigraphic map

Pertamina and BPPKA (1996)

Basement tectonostratigraphic correlation chart

Pertamina and BPPKA (1996)

Central Sumatra Basin

Pertamina and Beicip (1985)

Top basement structure map

Pertamina and BPPKA (1996)

Mertosono and Nayoan (1974)

Katz and Dawson (1997)

Eocene – Oligocene F1 (45 Ma-26 Ma) regional structure map

Pertamina and BPPKA (1996)

Miocene – Recent F2-F3 (26 Ma-0 Ma) structure map

Pertamina and BPPKA (1996)

Pertamina and BPPKA (1996)

Pertamina and BPPKA (1996)

Mertosono and Nayoan (1974)

Central Sumatra tectonostratigraphic chart

Pertamina and BPPKA (1996)

Stratigraphic nomenclature of Central Sumatra Basin

Wain and Jackson (1995)

Central Sumatra petroleum system events chart Pertamina and BPPKA (1996)

Cross plot of TOC and hydrogen index (HI) Pertamina and BPPKA (1996)

Kerogen assemblage dominated by fluorescent amorphinite (A) and degraded, freshwater Botryococcus (FWA) in Brown Shale formation, Central Sumatra basin. Netherwood (2000)

Brown shale isopach map in Pematang trough

Pertamina and BPPKA (1996)

Central Sumatra regional heat flow map Pertamina and BPPKA (1996)

Paleogene depocenters, generalized structure and oil field distribution for the Central Sumatra basin

Praptono et al. (1991)

Field distribution along regional, north-south trending dextral transcurrent faults in the coastal plains block of Central Sumatra

Heidrick and Aulia (1993)

Netherwood (2000)

Sihapas reservoir of Bekasap formation in Minas field

Pertamina and BPPKA (1996)

F2 – F3 Duri field and seismic profile Pertamina and BPPKA (1996)

F2 – F3 East Kayuara field and seismic profile

Pertamina and BPPKA (1996)

F2 – F3 Kotabatak field and seismic profile

Pertamina and BPPKA (1996)

F2 – F3 Lalang field and seismic profile Pertamina and BPPKA (1996)

F2 – F3 Libo SE field and seismic profile Pertamina and BPPKA (1996)

F2 – F3 Lirik field and seismic profile Pertamina and BPPKA (1996)

F2 – F3 Melibur field and seismic profile Pertamina and BPPKA (1996)

F2 – F3 Minas field and seismic profile

Pertamina and BPPKA (1996)

F2 – F3 Parum field and seismic profile Pertamina and BPPKA (1996)

F2 – F3 Petani field and seismic profile Pertamina and BPPKA (1996)

Stratigraphic Correlation of Central and South Sumatra Basins

South Sumatra Basin • The basin contains diverse petroleum systems, with both oil and gas being sourced from lacustrine and fluvio-deltaic terrestrial facies. • Limited potential still remains for the traditional Talang Akar and Batu Raja formation plays. • In contrast to the basin’s mature oil status, the South Sumatra Basin is under-explored for gas, and contains good remaining gas potential in both new and existing successful plays. A further 6 to 10 TCF gas could be discovered in the basement, Talang Akar, and Batu Raja.

Awang H. Satyana (2005)

South Sumatra Basin

Pertamina and Beicip (1985)

Yulihanto and Sosrowidjoyo (1996)

Generalized structural pattern of South Sumatra Basin

South Sumatra structural framework

Pertamina BPPKA (1996)

South Sumatra surface structures

Pertamina BPPKA (1996)

Ginger and Fielding (2005)

Pertamina and Beicip (1985)

Stratigraphy of Palembang and Musi areas, South Sumatra Basin

Hutapea (2002)

Chronostratigraphic scheme for the South Sumatra Basin Ginger and Fielding (2005)

Exploration history of the South Sumatra Basin Ginger and Fielding (2005)

Cummulative discovery curve for the South Sumatra Basin split by reservoirs Ginger and Fielding (2005)

Netherwood (2000)

Present day maturity map on top basement

Ginger and Fielding (2005)

Netherwood (2000)

Suban giant gas field : producing gas from multiple reservoirs (igneous-metamorphic rocks, siliciclastics and carbonates) Pujasmadi et al. (2002)

Depth structure map of top Baturaja Formation

Stratigraphy of South Sumatra Basin

Kaji-Semoga field : big discovery in an over 100 year explored-basin Hutapea (2002)

Leached skeletal packstone of Baturaja carbonate

Tectonic setting of Sumatra

OMBILIN

PASEMAH

Darman and Sidi (2000)

Stratigraphy of Ombilin Basin, West Sumatra

Noeradi et al. (2005)

Kamal (2000)

Tectonic setting of Pasemah Block, South Suamtra

Kamal (2000)

Subsurface stratigraphy of Pasemah Block, South Suamtra

Fore-arc Basins •

Fore-arc basins have traditionally prospective for hydrocarbons due to :

been

considered

poorly

– source-rock facies were unlikely to develop in these essentialy shallow, oxygenated, open-marine basins, – Reservoir quality was assumed to be problem because nearby volcananic arcs and melange complex have supplied a predominance of poor-quality reservoirs, – Geothermal gradients are relatively low. •

Six fore-arc basins of Western Indonesia have been drilled : Banyumas, South Central Java, Southwest Java, Bengkulu, Mentawai, Sibolga. The results, in some way, fuel optimism for the existence of economic petroleum reserves in the Western Indonesia fore-arcs. Awang H. Satyana (2005)

Simplified map of structural elements and HC occurrence in the Sumatra forearc

Yulihanto et al. (1995)

Bengkulu-Mentawai-Sibolga Basins (1) •

The Bengkulu basin is the mostwidely explored fore-arc basin in Indonesia. All Bengkulu basin carbonate targets proved to be water-filled. Arwana-1 (Fina, 1992) encountered good oil shows and penetrated good marine sources of Oligo-Miocene shales which are within the oil window with GG of 4.5-5°C/100 m (this is significantly higher than normal fore-arc setting). The origin of the Bengkulu basin is not strictly fore-arc, may originally have been in back-arc setting (Howles, 1986; Mulhadiono and Asikin, 1989; Hall et al., 1993; Yulihanto et al., 1995).

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The Bengkulu basin has a proven petroleum system for oil generation. It demonstrates a similar geology to the South Sumatra basin, with an undrilled Paleogene rift system that could feasibly contain lacustrine source rocks, and proven post-rift reservoir facies. Post-rift Miocene shales and some coals are proven source facies.

Awang H. Satyana (2005)

Bengkulu-Mentawai-Sibolga Basins (2) •

Fieldwork in the Mentawai Islands shows that the marine Oligocene graben fill in the Mentawai basin has source potential. Basin modelling suggests that these sediments may have entered oil window as early as the middle Miocene. Early Miocene buildups are considereda potential reservoir target. Some wells contain biogenic methane shows (Yulihanto and Wiyanto, 1999).

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Suma-1, Singkel-1 (Union Oil), and Ibu Suma-1 (Caltex) wells of Sibolga basin encountered sub-economic quantities of biogenic gas (Dobson et al., 1998) middle Miocene carbonate build ups. The traps have sealing problem. Interbedded sands may show better biogenic gas prospects.

Awang H. Satyana (2005)

Yulihanto et al (1995)

Tectonic setting of Bengkulu fore-arc basin

Yulihanto et al (1995)

Stratigraphy of Bengkulu fore-arc basin

Yulihanto (2000)

Stratigraphy of Mentawai fore-arc basin

Yulihanto (2000)

Subsurface stratigraphy of Mentawai fore-arc basin

Stratigraphy of Nias, Sibolga fore-arc basin

vide Murphy (2000)

Seismic section and interpretation of the middle Miocene Ibu Suma buildup, Sibolga basin, north Sumatra fore-arc Dobson et al. (1998)

Fore-Arc Basins : Conclusions •

Fore-arc basins of Western Indonesia are poorly understood but their hydrocarbon potential is considered to be moderate to high (Netherwood, 2000).

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The Bengkulu basin experienced a history similar to that of the backarc basins : Paleogene rifting, Miocene structural modification, inversion and raised heat flow in Pliocene-Pleistocene times. The Bengkulu basin demonstrates mature source potential, sufficient heat flow for oil generation, and convincing oils shows in wells.

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Presence of biogenic gas and low geothermal gradient in Sibolga Basin are promising for future biogenic gas exploration. Interbedded sands within early Miocene reefs will be better sealed than reefs.

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Numerous oil and gas seepages in Bayah and Banyumas areas demonstrate the presence of active petroleum system. The presence of excellent Eocene reservoirs is promising. The areas are worth for further exploration. Awang H. Satyana (2005)