The 1st AAPG/EAGE PNG Geosciences Conference, PNG’s Oil and Gas Industry:
Maturing Through Exploration and Production

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New Insights into the Hydrocarbon System of the Eastern and Papuan Plateaus, offshore PNG

Abstract

The Eastern and Papuan Plateaus are located off the south coast of Papua New Guinea (PNG) adjacent to the Papuan Peninsula. The combined area of the plateaus is approximately 75,000 km2 with a present-day water depth range from 1,000 m to 3,500 m. From a hydrocarbon exploration perspective, this area is considered to be frontier acreage. Previous exploration within the Gulf of Papua has been focused to the northwest, shallow water (<1000 m) area. The most successful play is the Miocene isolated carbonate platforms and build-ups as demonstrated by the Uramu, Pasca and Pandora discoveries. Deeper tests of Mesozoic clastics are, to date, unsuccessful. The most recent clastic discoveries are Flinders-1 and Hagana-1, in the Fly River Delta, Pliocene deepwater clastic strata. No wells have been drilled on the deepwater (>1000 m) Eastern or Papuan Plateaus, with Pandora being the nearest offshore penetration. Data collected over the past 3 to 4 years, including multi-client 2D seismic datasets, potential-fields data and a drop-core survey have enabled regional mapping and basin analyses with improved confidence. These results provide insight for future exploration activities. Regional maps constructed from the interpretation of key stratigraphic markers on the 2D seismic grid provide an early insight to the structural and stratigraphic evolution of the Eastern and Papuan Plateaus. Integrating this interpretation with gravity and magnetic data, plate tectonic models, geologic analogues and basin modelling helps define the key risks and uncertainty. Quantified results can then be summarized in a series of play element maps. Depth-to-basement mapping and the associated total-sediment-fill isochore are key to identifying prospective regions. Areas with the thickest overburden, as identified on the interpreted isochore, indicate more favorable source rock maturation conditions. These maps also define structural fabric, enabling the identification of traps and potential closures, such as large structural highs adjacent to grabens of variable size and sediment fill. Within these grabens, the presence/absence and thermal maturity of source rocks, are key regional play elements. Source maturation analysis indicates that the largest mapped half grabens may be mature for hydrocarbon generation, provided a viable source rock is present. Because of the multiple phases of sedimentary fill in the grabens, timing of hydrocarbon generation is uncertain, however the hydrocarbon system is deemed patchy, yet plausible across the Eastern and Papuan Plateaus. The Eastern and Papuan Plateaus represent a large region of underexplored, high-risk, frontier acreage. Recent multi-client 2D seismic and drop core surveys were instrumental in advancing our understanding of the area and have enabled identification of prospective areas and key risks.