Abstract

Sixty-three basins have been classified on a genetic basis, according to plate tectonic histories and oil reserves estimated using a probability/analogue methodology. Over thirty-five billion barrels of produced and producible oil have been found to date; we forecast that another thirty-five billion barrels of producible oil remains to be found. So far, two and one-half times as much oil has been found onshore as offshore. For the future, we forecast that there are one and a half times as much oil to be found offshore as onshore. Four of eleven recognized basin-families probably contain some 84% or so of all SE Asian oil. These four, representing preferred habitats, include: oceanic-margin, back-arc, wrench, and suture-related basin-families; only the first, oceanic-margin basin types, overlies ocenic-crust. Distribution of these basins closely follows the tectonic evolution of the SE Asian region. Sundaland has been the core for accreting subduction margins since at lest late Paleozoic time. Significant reorganization occurred in mid-Tertiary time when extension tectonics became dominant in the South China Sea, and when subduction migrated from eastern Kalimantan to the present position south of Java. The Sunda Basin, orientated normal to and coincident with the southern accretionary margin, apparently overlies a discontinuity of the subducting Indian Ocean Plate occasioned by a sharp change in strike at the frontal trench system, rather than follow accretionary basement grain, as appears to be the normal control in basins in SE Asia.

There are striking differences in history and style between Sundaland and New Guinea. Subduction/suture/transform processes along the northern margin of the Australian Plate have created large structural prospects in Mesozoic as well as Tertiary reservoirs.

A general inadequacy of reservoir section in the intra-oceanic-arc style basins, typical of the Philippine Archipelago, leads to this being the lest important group in our classification of SE Asia Basins, at least as regards oil potential.