Abstract

The Asri Basin in the Maxus Southeast Sumatra PSC, has proven recoverable oil reserves of approximately a half-billion barrels from nine fields including the major Widuri and Intan oil fields. The majority of the fields were discovered prior to the confirmation of an oil source rock in the basin. The penetration of an organic-rich, mature source rock by the Hariet-2 well in 1995 has helped define the primary petroleum system with a high degree of confidence. There is an excellent geochemical match between produced oils and the lacustrine, black shales of the Banuwati Formation. Both source beds and the Talang Akar (TAF) reservoir beds can be mapped seismically on an existing grid of 2D and 3D seismic data over the field areas. The primary carrier beds cannot be imaged but the migration route can be deduced from the spatial distribution of oil shows in wells updip of the Hariet-2 well. A series of basin maps, combined with geochemical analyses of rock and oil samples, define the Banuwati - TAF petroleum system in the Asri Basin.

A secondary petroleum system was also discovered by the Hariet-2 well when Banuwati shale-sourced oil in an early basin, coarse clastic interval was encountered beneath the shale. Elements of this Banuwati-Early Basin Fill petroleum system are also described in this paper. The implications of these petroleum systems will direct future exploration efforts within the Asri Basin.