Abstract

The ancient Talang Akar deepwater reservoir in South Sumatra Basin has never been intensively explored and distribution of the play is not fully understood. However, some indications of ancient deepwater sediments have been observed in the southern margin of Central Palembang Sub-basin. An integrated exploration technique involving analyses of wireline logs, biostratigraphy, petrography and outcrop, plus seismic and sequence stratigraphic interpretations has been applied to assess the possible presence of ancient Talang Akar deepwater deposits in the basin. However, the poor quality of the 2-D seismic vintages has limited direct observation of the reservoir distribution.

There are two potential areas where Talang Akar deepwater sediments could be present in the basin: Central Palembang Sub-basin in the west, and Benakat Gully in the east. Possible sediment provenance for the deepwater sediments is the Lemat Formation rocks and/or older rocks on the local paleo-basement highs. This is consistent with the paleogeographical reconstruction of the Central Palembang Sub-basin during the Early Miocene lowstand phase. However, this is still speculative and requires further geological and geophysical research. The expected reservoir is sandstone, with a possibly wide range of rock properties and compositions. The tuffaceous content observed in the Central Palembang Sub-basin could be derived from the litharenite of the volcaniclastic affinity in the Musi Platform and Mambang High. The sediment sources in the Benakat Gully could possibly be from the quartz-rich sediments of the Talang Akar active delta system to the southeast and other coastal plain deposits surrounding the basin centers.

The hydrocarbon potential of this Talang Akar deepwater play remains unknown. The source rocks are mature- to over-mature shales of Lemat and Talang Akar Formations. Results of basin modeling indicate that the sources entered oil window in the middle Lower Miocene and began generating gas in the Middle Miocene. The trap is mainly stratigraphic in combination with structure developed during the Late Miocene to Plio-Pleistocene orogeny. Intraformational deep marine shales provide the vertical seal. The structure is generally complex. Variation in fold and fault development is present as a result of Plio-Pleistocene regional compression tectonics.