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ABSTRACT: Depositional systems of the deep water Tarakan Basin, Indonesia

Hemmes, Kaj1, Herman Darman1, Leonardus Suffendy2, and Meizarwin Meizarwin2
(1) Shell E&P Companies in Indonesia, Jakarta, Indonesia 
(2) Atlantic Richfield Indonesia Inc, Jakarta, Indonesia

Exploration activity in the Tarakan Basin spans more than a century. Numerous oil and gas discoveries have been made onshore on the Tarakan and Bunyu structural highs. Offshore, only the shallow water deltaic sequence has been tested so far.

Recently, 2000 km of modern 2D seismic data were acquired over the deep-water area and used to develop reservoir depositional models for oil and gas exploration.

The Tarakan Basin constitutes a passive continental margin with Late Eocene-Recent sediments on continental to oceanic crust, created during the Middle-Late Eocene opening of the Celebes Sea. Rifting ceased during the early Oligocene with quiet marine conditions prevailing until the Middle Miocene uplift of the Borneo hinterland. The latter uplift triggered a massive influx of turbidites in the deep-water area, deposited as unconfined toe of slope fans ahead of the outbuilding Tarakan delta. During Plio-Pleistocene delta outbuilding, this sequence was buried by rapidly prograding slope deposits, which triggered gravity-driven toe thrusting. Small basins were formed between thrust ridges and filled by slope deposits. In the southern part of the delta, westward dipping normal faults limited progradation, resulting in excessive thickening of the Pliocene-Pleistocene deltaic sequence and limiting sediment influx into the deepwater area.

Several potential reservoir systems are recognised in the deepwater area. These include 1) unconfined toe of slope fans, 2) confined intra-slope fans, and 3) intra-slope channel (-levee) systems.

Further seismic and exploratory drilling will be required to confirm the lateral extent and sand proneness of the deepwater systems of the Tarakan delta.

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