SEDIMENTARY EVOLUTION OF RIFT BASINS IN SULAWESI ISLAND REGION, INDONESIA AND ITS CONTROLS ON HYDROCARBON GEOLOGICAL CONDITIONS

Sedimentary evolution characteristics of the rift basins in the Sulawesi Island Region and their effects on source rocks and reservoir-cap associations are studied comprehensively by this paper, in order to reveal the hydrocarbon accumulation conditions. The results suggest that the sedimentary facies of the Paleocene to Eocene controlled the lithology and distribution pattern of effective hydrocarbon source rocks. The source rocks are dominated by mudstone and coal of lacustrine to swamp facies with tidal flat and lagoon facies found in sags. There are two kinds of reservoir-cap associations. The Paleocene and Eocene river-delta facies in the west part of Sulawesi formed the clastic rock association with good petrophysical properties, while the Late Miocene to Pliocene shelf platform facies formed the most important carbonate rock association. Especially, the reef reservoirs with excellent properties occur on the platform or the border of platform. So far important discoveries have been made in the rift basins which has become the most important target for oil and gas exploration.