Abstract Cross sections, seismic data and centrifuge analogue modelling reveal the structural styles in the oil-producing areas of the Papuan Fold Belt. They include inverted basement faults, detachment faults in the Jurassic section 1–2 km beneath the Neocomian Toro Sandstone reservoir, and tight, overturned folds in the reservoir sequence with stretched and boudinaged forelimbs, cut by break-thrusts. Additional features include highly variable thicknesses in the Cretaceous Ieru Formation, the regional seal sequence, including through-going detachments that isolate the overlying thick Miocene Darai Limestone. Centrifuge analogue modelling of intact, plane-layered strata determined that the mechanical stratigraphy and the thickness of weak beds above the lower décollement horizon exert the greatest control on the structural style. Large-offset thrust faults were only produced in models with pre-cut faults, generating early inversion and then large ramp anticlines, similar to those in the Kutubu Oilfield, which has reserves of >350 million barrels. It is suggested that the Kutubu Oilfield trend was underlain by a large normal fault and that, by analogy with the Vulcan Sub-basin, oil-rich source rocks may be confined to the hanging wall or north side of this fault. Oil would have been generated and expelled during thin-skinned deformation.

ABSTRACT The Papua New Guinea fold and thrust belt petroleum system is studied along a 200-km (124-mi)-long transect. The kinematic scenario includes the Jurassic rifting and passive margin, the erosion during the Upper Cretaceous related to the Coral Sea rifting and Pliocene–Pleistocene shortening, with an early growth of the Hedinia Anticline limiting lateral migration of oil in the adjacent Darai Plateau. Data from seven wells and two fields were used to calibrate section boundary conditions and properties. Apart from the high-pressure trend in the Kutubu/Moran structures, all data are well reproduced, and the modeled section appears quantitatively predictive. The modeling demonstrates three major pathways for water: (1) topographically driven flow from the onset of mountain building; (2) deep updip basinal flux, flowing along the tilted reservoirs; and (3) across fault escape from connected reservoir bodies. Type II or mixed type II/III is used to model the Triassic and Jurassic source rock. Maturation starts in the Middle Cretaceous and increases strongly during the late tectonic burial, with three main accumulations: (1) the deep part of the Mubi zone, with vertical migration along faults; (2) the Hedinia and Kutubu anticlines charged during Orubadi and Era deposition; and (3) the Darai Plateau.

Abstract We defined the folding sequence of the fold–thrust belt of the Western Papua New Guinea Highlands by analysing the surface expression of the structures and the response of the drainage system to the active fold–thrust belt. The interaction between structures is typically assessed by examining the syn-kinematic strata preserved; however, in our study area, this is problematic as these strata are poorly imaged on seismic lines. This study found common morphological features that allowed grouping and mapping of three different structural settings: group I, basement-involved tectonics; group II, thin-skinned anticlines which sole near the Koi–Iangi Sandstone; and group III, thin-skinned folds associated with the intra-Ieru Formation detachment. Fold Front Sinuosity analysis supports the idea that the fold–thrust belt propagates from the NW to the SE. Considering the detailed morphotectonics and drainage analyses, we interpret that the group II folds developed as out-of-sequence thrusting and folding, associated with buttressing against the group I larger structures.