GEOLOGICAL CHARACTERISTICS AND DISTRIBUTION PATTERN OF PETROLEUM IN WEST NATUNA BASIN, INDONESIA

The West Natuna Basin, an intracratonic rifted basin on the northern Sunda Shelf, is an important petroliferous basin in Indonesia. Following the principles of basin analysis and petroleum geology, taking the tectonic evolution and sedimentary filling history of the whole basin as the major theme, we studied in this paper the forming mechanism of petroleum accumulation, such as source rocks, reservoirs and seals, in the basin. The hydrocarbon distribution and accumulation patterns were systematically summarized. Through comparison, it is concluded that the difference of tectonic evolution and sedimentary filling is the controlling factor over the difference in source maturity, reservoirs and hydrocarbon accumulation characteristics in the basin. Regionally, the discovered oil and gas reserves are largely confined to the Anambas Graben and the Northeastern Penyu Sub-basin and trapped in compressional anticlines, draping structures and structure-stratigraphic traps. Stratigraphically, the oil and gas are mostly reserved in the Upper Oligocene and Lower Miocene. Future exploration potential may exist in the under explored stratigraphic traps in the coarse grained alluvial fan deposits of the Belut Formation and incised valley fills of the Gabus Formation and Lower Arang Formation.