Publications

Most Neogene reservoirs of western Indonesia have been exploited. Thus, deeper Paleogene systems become the next potential main exploration target. Since most of the Paleogene system consists of rift plays, then a good understanding of the rift related petroleum system and its pitfalls are required. The Ombilin basin might serve as good model, especially with all available outcrops.In a geographical sense, the Ombilin Basin is situated within the Barisan Mountains but structurally and in a plate tectonic setting, it displays a position in the region east of the present volcanic arc which indirectly highlights the controversial non-volcanic Barisan eastern range (Figures 1 and 2). The eastern margin of the Ombilin Basin is furthermore accentuated by a WNW-ESE trending major fault or fault system (Takung fault) which at the same time bounds the abovementioned non-volcanic Barisan eastern range on its western side. To the west, the Ombilin Basin is bounded by a NW-SE trending fault system presently known as the Barisan Fault System. Included in this system is the NW-SE trending Singkarak Lake.Oil exploration commenced in the basin in the early 1980s, started by surface geological mapping, radar survey, and a basin-wide geophysical survey. This effort led to the recognition of at least 5 leads. The Sinamar prospect was drilled in 1983 (Sinamar-1, Caltex) to a total depth 3020 m, the well proved hydrocarbon occurrence in the prospect. The South Sinamar prospect was tested eleven years later (South Sinamar-1, Apache), and resulted in hydrocarbon show on cuttings. Both prospects were related to inversion structures. Thus, the petroleum system of this basin is confirmed, and it potentially yields oil and gas.Stratigraphic studies confirmed abundant reservoir potential could be found in the basin, but their quality is in question. Consequently, position and location for porosity preserved reservoir, either by stratigraphic or by structural means, should be investigated for future exploration.