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ABSTRACT: Kerendan: An Isolated Oligocene Carbonate Platform in the western Kutai Basin, Central Kalimantan, Indonesia

Saller, Arthur H.1 and Suta Vijaya2
(1) Unocal Corp, Sugar Land, TX 
(2) Unocal Indonesia, Balikpapan, Indonesia

The Kerendan platform is a latest Eocene and Oligocene limestone (Berai Formation) covering approximately 180 square kilometers (approximately 11 by 16 km) in the westernmost Kutai basin in Central Kalimantan. The Kerendan platform is approximately 30 km north of the Barito shelf margin, which was aggrading and backstepping during the Oligocene. The Kerendan platform is approximately 1000 m thick, and contains three seismic sequences. Carbonate deposition started in the late Eocene, and the upper limestone sequence drowned and was covered with shale at approximately 28.6 Ma. Three seismic facies tracts can be distinguished: (1) platform interior (lagoon), (2) very shallow platform rim and (3) basinward dipping shelf margin and slope. Seismic lines suggest that the outer 1-2 km of the Kerendan platform was a topographically elevated rim. The lagoonward margin of the platform rim was identified by an abrupt lagoonward dip in the top Berai reflector and thinning of the upper Berai. The platform interior (lagoon) consists of fossiliferous wackestones and packstones, and is generally not porous. The platform rim contains interbedded coralline algal-large foram wackestones, packstones, grainstones, and boundstones, with grainstones increasing toward the platform margin. Reservoir intervals of the platform rim have porosities of 5-11%, with porosity decreasing lagoonward as grainstones and boundstones decrease. The platform margin was not extensively penetrated by wells, though outcrop models suggest it is coral boundstone-rich and porous.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia