Publications

The KB Graben is a NE-SW trending basin lying on the eastern flank of Khorat Platform in the northern West Natuna Basin, Indonesia. Of the eight wells drilled to date in the graben, only two have tested Late Oligocene pre-inversion traps. The Biduk-01 and Biduk Baru-01ST wells, respectively, recorded an oil influx and oil shows from overpressured sands of the syn-rift sequence. The remaining wells tested younger Miocene inversion structures and were dry. Post-mortem evaluations of these wells suggest that Miocene trap formation post-dates the main phase of oil generation. Recent studies by Lundin, however, suggest the lack of oil in the younger structures may be due to the presence of late syn-rift overpresssured shales which provide a regional seal for hydrocarbons generated in the syn-rift kitchen. Regional mapping further highlights the absence of the Upper Oligocene Barat Shale regional seal over many of the Miocene inversion structures, which might also be a key factor in the lacking of hydrocarbon accumulations in the Gabus reservoirs in these traps. Detailed seismic interpretation of recently acquired 2D and 3D seismic data, a re-evaluation of well biostratigraphic data, structural reconstruction study and 3D basin modelling have led to a revised structural model for the KB Graben and West Natuna Basin and a new charge/migration model for the area. Hydrocarbon generation and expulsion from syn-rift lacustrine source rocks in the KB Graben started at 26 Ma and continues to present day. Late syn- rift overpressured shales inhibit vertical migration from the kitchen and east-dipping syn-rift carrier beds focus lateral migration westwards towards the basin margin. Lundin has identified a number of attractive prospects in both Lundin operated Baronang and Cakalang Blocks located, respectively, over the KB Graben and its hanging wall margin. Two exploration wells will be drilled in Baronang in 2013 to test the basin margin play.