Publications

The Sanga Sanga PSC contains four large to giant hydrocarbon fields in Middle and Upper Miocene deltaic sandstone reservoirs. The fields are located in NNE-trending structures of the Mahakam fold belt. Section balancing of depth converted seismic lines and scaled physical modeling were conducted to determine a viable structural model for the evolution of the Mahakam fold belt. The scaled physical modeling involved testing five, previously proposed, tectonic models. A combined model of differential loading followed by contraction was also tested.The scaled physical modeling shows that gravity glide and strike-slip models do not simulate the observed structures. Contractional (thrust), inverted extensional faults and simple differential load models only partially simulate the structures. The combined tectonic model resulted in re-activation and inversion of delta growth faults to form inverted graben structures. It is the most successful model being geometrically, kinematically and mechanically viable for the evolution of the Mahakam fold belt. This is termed an inverted delta growth fault model.Section 'balancing indicated that the change from an overall extensional system to one of contraction started at 14.0 ma. The inversion is directionally controlled where the structures trending NNE are close to perpenQcular to the applied stress and become inverted. The paleo-reconstructions indicate that, at times, structural development controlled sedimentation patterns resulting in channel orientations parallel to, or deflected by, the developing structure.The timing of growth for each structure was combined with VICO geochemical models to determine the timing of hydrocarbon generation, migration and entrapment.