Abstract

Previous exploration and production efforts in the Kutai Basin have focussed on the Miocene deltaic play. An additional play and hydrocarbon system within the Palaeogene has been proven recently by LASMO and its partners during exploration in the North Runtu PSC, onshore East Kalimantan. However, to date no presently economic hydrocarbon accumulation has been discovered.

Although the Palaeogene play has long been recognised within the Kutai Basin by analogy to the Tanjung Field in the Barito Basin to the south, previous efforts within the Kutai Basin had resulted in intersection of overmature, extensively uplifted section. Techniques developed by LASMO have demonstrated that prospective areas exist within the potential Palaeogene play fairway that have not suffered extensive uplift. This has been confirmed by three exploration wells in the North Runtu Block.

Play elements of the North Runtu PSC consist of upper Eocene Beriun Formation deltaic reservoir sands, with associated coals and coaly shales that make in places excellent source rocks. Structural closures exist, and in some places have suffered only small amounts of uplift and are covered by the Upper Eocene to Oligocene regional seal.

Although the essential ingredients for a working petroleum play are present in the North Runtu PSC, the system appears to be limited by the reservoir quality within the Eocene. The interpretation of the syn-rift section in this area relies on an understanding of the original depositional topography, sediment source provenance, basin geometry and subsidence rates. The challenge for this play in any future exploration is to identify regions where excessive burial has not removed porosity, and where original mineralogy and depositional environments were suitable for creating good quality reservoir.