Modern proprietary and regional multi-client 2D seismic data uncovered the reservoir potential of extensive turbidite fairways and submarine fan complexes, deposited during the Mid-Miocene. New multi-client 3D (MC3D) high-resolution, broadband, Q-PSDM FWI data acquired offshore Papua New Guinea in 2023 by Larus Energy and Searcher has illuminated the interaction and subsequent reworking of these turbidite systems by bottom currents.

The Nanamarope MC3D seismic dataset contains a wide spectrum of contourite features and shows that contourite processes have been active from at least the Early Miocene to the present day. The Mid-Miocene is marked by a major depositional event, linked to active tectonism and the formation of the proto–Owen Stanley Range, which resulted in a high influx of sediment supply to the basin floor, via slope canyon systems. Seismic facies analysis has revealed that during the Mid-Miocene, strong predominantly downslope contour currents interacted with turbidite depositional processes and intensively reworked the reservoir interval into smoothed and sculpted contourite sand sheets.

Features such as scours, mega-furrows, sub-circular eddy current cuts, sand furrows and sandy sediment waves are observed, illustrating the alternation of both erosional and depositional current related processes in time and space, operating in tandem with gravitationally driven sediment supply. The bathymetric expression of the basin floor in the Mid-Miocene was influenced by the southward propagation of the deep-water Aure Moresby fold and thrust belt and by the prominent underlying rift structure, exacerbated by the underfilled nature of the basin at this time. Topographical variations of the sea floor, locally exhibited a control on the path and velocity of the contour currents, further defining the spatial distribution of erosional and constructive reworking features. It is also observed that bottom currents provide a mechanism to redistribute fine-coarse grained material beyond the limits of the traditional turbidite fairway.

In the last decade there has been an acceleration in research of contourites and hybrid / mixed turbidite contourite systems, partly driven by giant hydrocarbon discoveries such as the Coral (80 TCF) and Mamba fields in East Africa. It has been recognised in hybrid (synchronous) and mixed (asynchronous) reservoir systems that the action of bottom currents can vastly improve reservoir properties such as net to gross ratio. This is achieved by the presence of a moderate - high energy environment on the slope and/or basin floor driven by semi-permanent currents. The interaction of the contour current flow with turbidity currents and their deposits, results in the stripping and off axis redeposition of the fine-grained material and the concentration and sorting of reservoir sands.

Despite the focus for hydrocarbon exploration and vast improvements in seismic acquisition and processing, there are very few published seismic examples of significant ‘sandy’ mixed turbidite contourite systems. The aim of this presentation is to show groundbreaking data from the Nanamarope MC3D, present new analysis of ‘sandy’ mixed systems and illustrate how gravitational and bottom current processes have combined to shape the southeastern margin of Papua New Guinea.