Abstract

A general Paleogene basin study of Western Indonesia is presented primarily based on review of publications and some supporting seismic and well data. The study attempts to review tectonic and stratigraphic evolution, petroleum systems distribution and generalised paleogeography of the Paleogene basins in Western Indonesia.

Paleogene basins are identified along the margin of Sundaland. The basins were developed in association with subduction of the Indian Ocean crust beneath Sundaland originating in the late Cretaceous during collision of India and Eurasia.

The stratigraphic evolution of the Paleogene basins was in an overall transgressive setting that changed from continental to marine conditions. Initial development of the Paleogene basins by basement rifting was normally associated with a syn-rift sedimentary package of continental deposits. Gradual marine incursion occurred by late stage of rifting and during the post-rift episode the depositional environment was fully marine. In some areas of Sundaland, marine conditions probably prevailed throughout Tertiary time.

These Paleogene basins commonly are complete petroleum systems, except for maturity, as they contain source rocks, reservoirs and seals, but maturity of source rocks normally was reached after the deposition of Neogene sediments overlying the Paleogene basins. There are a wide variety of Paleogene source rock facies including lacustrine, fluvio-deltaic, and paralic to marginal marine. The lacustrine source rocks were deposited during the rifting episode while marine organic-rich carbonaceous shales and coals developed during the late stage of rifting to post-rift episode. Hydrocarbon productive Paleogene reservoirs most commonly are in the upper part of the syn-rift sediments or in some cases in the post-rift sediments which generally are a sealing facies.