--> ABSTRACT: Tectonic Evolution and Its Influence to Gumai Formation as an Active Source Rock at Sopa Field, South Sumatra Basin, Indonesia, by Patra, Dimas H.; #90135 (2011)

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Tectonic Evolution and Its Influence to Gumai Formation as an Active Source Rock at Sopa Field, South Sumatra Basin, Indonesia

Patra, Dimas H.1
(1)Exploration (G&G South Sumatera), Pertamina-EP, Jakarta, Indonesia.

Shale from Lahat and Talang Akar Formations were widely accepted by many geoscientists as general source rocks in Palembang sub-Basin part of South Sumatra Basin. The oil from Sopa Field was considered as hydrocarbon accumulation that had been migrated from local and regional deeps around Sopa Field, where Lahat and Talang Akar Formations were deposited.

The result of comprehensive geochemical analysis shows that oils at Sopa wells migrated from source rock that had been deposited at transition environment. Oil from Sopa is correlated with bitumen that was extracted from sediment sample of Gumai. The sample of Gumai Formation was deposited at lagoon environment. On the other hand, extracted bitumen of Baturaja Formation sample was analyzed as non-indigenous or has been migrated from other sources. Therefore, the bitumen for sample of Baturaja Formation was not valid for further analysis.

Seismic data interpretation (including flattening methods) is transformed into a geology model that will give explanations of maturity and migration mechanism of shale in Gumai Formation. Tectonic evolution at South Sumatra Basin since Middle Miocene to recent time, had been forming a massive number of thrust faults that make some blocks becoming higher, while the other was buried deeper. Some part of Gumai Formation at fault’s foot wall was reached maturation zone. These tectonic evolutions was also made carbonate reservoir became tilted, therefore it helped hydrocarbon to move from the lower part to the shallower part. Hence, Gumai Formation is also acting as active source rock at Sopa Field.

Gumai Formation has been proved as active source rock at Sopa Field, and it may open the new vision of hydrocarbon exploration with the same play. The model that was resulted from this paper may be used as an analog to define a source rock that younger than its reservoir.

 

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.