--> The Palaeogene Rifts of Western Indonesia, by S. Courteney and H. H. Williams; #90986 (1994).

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Abstract: The Palaeogene Rifts of Western Indonesia

Steven Courteney, Harold H. Williams

During the Palaeogene two, perhaps three, phases of rifting occurred in Western Indonesia. The resulting rift systems are of major economic importance since the syn-rift middle Eocene through early Oligocene sediments contain almost all the effective hydrocarbon source rocks of Western Indonesia. In a few basins sediments related to a possible earlier phase may be the source of the remaining hydrocarbons. The post-rift Late Oligocene and younger fluvio-deltaic source rocks, so often cited in the literature, have not contributed significantly to the hydrocarbon reserves of Western Indonesia.

Conversely, syn-rift reservoirs contain only some 8.1% of the estimated proven oil reserves and 2.0% of the estimated proven gas reserves of Western Indonesia as opposed to 91.7% and 97.9%, respectively, for the post-rift reservoirs. Pre-Tertiary reservoirs account for the remainder. With few exceptions the fields that produce from syn-rift reservoirs also produce from the overlying post-rift reservoirs, which were the target of the discovery well.

Previously the importance of the Palaeogene rifts has been underestimated for various reasons. These include: misinterpretation of the top source rock seismic reflector as the `Top of Basement' and the common misconception that rifts contain only deep lacustrine source rocks. The latter has caused considerable confusion since only oils with the `classic' deep lacustrine source signature tend to be attributed to rift sequences. In fact rift sediments range from fluvial through shallow and deep lacustrine to open marine.

This paper further investigates the hydrocarbon prospectivity of syn-rift sequences and traps in the Palaeogene Rifts of Western Indonesia.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994