Abstract

The exploration success achieved with the discovery of the Merah Besar and West Seno fields was ground breaking because it demonstrated for the first time that a petroleum system was present in the deep-water acreage of the Kutei Basin. Intensive exploration activity in the Ganal and Rapak blocks by the Unocal-Eni partnership has since constrained many of the factors affecting this Miocene-Pliocene, palaeo-deep-water play. Whilst papers have been published on various elements of the play in recent years, the objective of this paper is to synthesize the key elements into a single description of the entire play.

The dominant structures in the present-day deep-water portion of the Kutei Basin are toe-thrust anticlines. Differences in the timing, style and intensity of these structures enables a sub-division of the region into three structural provinces (Northern, Central and Southern).

The development of these toe-thrust anticlines has influenced to varying degrees the development of this Miocene-Pliocene, palaeo-deep-water play. This influence ranges from the deposition of reservoir, source, to subsidence history and thereby source rock maturity, migration routes and, ultimately, many of the fields are in traps generated by these toe-thrust structures.

Consequently, the distribution and type of hydrocarbons encountered within this play reflects the structural variation across the toe-thrust province.

For instance, the mildly structured Upper Miocene section in the Central Province is gas prone whist in the Northern Province it contains material volumes of both oil and gas.