Abstract

The Tarakan Basin is one of three major Tertiary age deltaic depocentres located around the margin of Kalimantan. 14 oil and gas fields have been discovered, the largest of which were discovered before world war II. Almost all of the production has occurred on dip oriented arches in a very proximal (mostly non-marine) depositional environment. However, better seismic data suggests that forced regressions have caused deposition of deltaic reservoirs far downdip in present day deep water. This depositional model has resulted in a new exploration fairway for delta front sandstone reservoirs and has increased the hydrocarbon potential of a basin having a productive history dating from 1899. The application of deep water technology pioneered in the Gulf of Mexico will be essential in developing potential hydrocarbon accumulations in this fairway.

The Tarakan Basin was initiated simultaneously with the formation of the Sulawesi Sea by rifting of north and west Sulawesi from east Kalimantan between the Middle to Late Eocene and the end of the Early Miocene on east hading enechelon block faults. Accommodation space for an increased volume of deltaic sediments was created during the Middle Miocene to Pliocene period due to a combinatin of basin subsidence and gravity induced listric faulting. The productive dip oriented arches were formed during the uppermost Pliocene to recent period by transpression on wrench faults crossing the Makassar Strait.