Publications

The North East (NE) Bangkanai PSC is located in the onshore Kutai Basin, one of Indonesia’s prolific tertiary hydrocarbon basins. Integrated surface geological mapping, seismic interpretation, direct hydrocarbon indication analysis, palinspastic structural restoration, and petroleum system modelling have illuminated the hydrocarbon potential of both the Eocene syn-rift and Miocene post-rift play fairways in this PSC and led to a better understanding of the prospectivity and critical risks of reservoir quality and timing of trapping. The structural evolution of the NE Bangkanai area involved extensional tectonics, NW–SE strike-slip fault reactivation in the Mid to Late Eocene and subsequent Early Miocene contraction, which reactivated and inverted the Paleogene structures. The calculated strain during the early syn-rift phase ranges from 0.9–1.3% and during the maximum rifting period the strain is calculated at 2.3–4.5%, reflecting the peak of tectonic subsidence in the area. Low magnitude strain during the Oligocene period indicated a sag phase period and tectonic quiescence. Northwest Borneo’s continuous subduction and micro continent collision drove Early Miocene compression and formed NE–SW and N–S trending inversion structural traps, the age of which is clearly indicated by shortening strain calculations. The structural restoration suggests a strong E–W compressional direction with 3.3–7.2% strain value of shortening (e < 0). The latest tectonism in Borneo occurred during Pliocene to Recent and above this regional unconformity, non-marine mollasse deposition blanketed much of the area. In the NE Bangkanai PSC, the Paleogene Play Fairway is comprised of Mid to Late Eocene aged fluvial-deltaic clastic sandstones and Latest Eocene carbonate reservoirs. 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. Eocene coals and carbonaceous shales are a proven source for gas-condensate in the basin, as are Miocene terrestrial elements that generated the waxy and low maturity oils discovered in the Miocene sands. Two-dimensional seismic structural interpretation and reconstruction in NE Bangkanai have identified potential structural trap types along the NW–SE dextral strike-slip of Belayan fault zone, characterized by four-way hanging wall anticlines and three-way fault dependent closures, which are promising in their potential for hydrocarbon accumulations.