11. natuna petroleum geology

Netherwood (2000)

Stratigraphy of West and East Natunabasins

West Natuna Basin• The West Natuna basin forms the eastern part of the largest basin system

within the Sunda shelf, including the Malay basin and the basins in the Gulf of Tailand.

• The principle tectonic elements include three sub-basinal provinces : NW-SE oriented extension of the Malay basin, NE-SW oriented Anambas graben, east-west oriented Penyu graben. These sub-basins were initiated as early Tertiary rifts and are separated by major structural highs such as Renggol arch and Cumi-Cumi high that were inverted in the mid-late Miocene.

• The majority of discoveries have been made in the post-rift to syn-inversion seuences (Gabus/udang to Arang formations). Significant discoveries have also been made in the syn-rift pre-Gabus sequence. To date, approximately 500 MMBO and 2.5 TCFG have been discovered in the basin (Netherwood, 2000).

• The West Natuna basin is still considered to be prospective with many areas relatively under-explored. There is good potential within the deeper syn-rift sediment package where thick reservoirs are adjacent to generating source rocks and may be sealed by lacustrine and peri-lacustrine shales. Shallow gas in the Muda formation is also a promising new play concept.

Awang H. Satyana (2005)

Pertamina BPPKA (1996)West Natuna Basin

Michael and Bond (1997)

Pertamina BPPKA (1996)West Natuna chronostratigraphy

Play concepts for West Natuna basin Fainstein and Meyer (1998)

Michael and Bond (1997)

West Natuna Block B

Pertamina BPPKA (1996)West Natuna structural setting

West Natuna geologic sections (1)

Pertamina BPPKA (1996)

Section across West Natuna basin



West Natuna synrift organic facies distribution

Pertamina BPPKA (1996)West Natuna source kitchen

Pertamina BPPKA (1996)West Natuna gradient geothermal

Pertamina BPPKA (1996)West Natuna Lower Gabus paleogeography

Pertamina BPPKA (1996)West Natuna inversion structure (1)

Pertamina BPPKA (1996)West Natuna inversion structure (2)

Pertamina BPPKA (1996)West Natuna oil grouping

Pertamina BPPKA (1996)West Natuna South Kakap play concepts

East Natuna Basin• The basin extends to the east into the Sarawak basin off western

Borneo. • Unlike the West Natuna basin, it was not subjected to a major phase of

Miocene inversion and is, therefore, structurally quite different. • The East Natuna basin is divided into a number of discrete structural

elements defined by depressions and highs in the Cretaceous graniticand metasediment basements.

• The Sokang trough in the SW of the basin contains over 6000 m of Tertiary sediments and is separated from the main basin by a structural high called the Paus ridge. To the north of the ridge, is the north-south Komodo graben containing 5000 m of Miocene clastics.

• The Terumbu shelf in the north has developed between 2500 and 4000 m of neogene cover that includes up to 1500 m of Miocene to Pliocene Terumbu carbonates.


East Natuna Basin

• The East Natuna basin is well known as being the host for the largest gas field in SE Asia, the Natuna D-Alpha gas field, with 210 TCFG in an isolated buildup in the upper part of the thick, middle miocene to late Pliocene Terumbu carbonates. The buildup of the carbonate is over 1500 m, with episodic exposures leading to average porosity of 15 %. The main part of the gas (71 %, dunn et al., 1996) is CO2, reduces the HC gas into 45 TCFG.

• The East Natuna basin is relatively under-explored but the potential for further large gas discoveries in the Terumbu carbonates is low because most buildups have been drilled. The earlier syn-rift clasticplays, however, require more serious consideration, with proven HC generating capabilities and thick, high-quality sands.


Play concepts for East Natuna basin

Fainstein and Meyer (1998)

11. natuna petroleum geology

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