Hidden in Plain Sight: The Bamaga Basin

The Gulf of Carpentaria was extensively explored in the 1970s and 1980s targeting the Carpentaria (JurassicCretaceous) and Karumba (Tertiary) sag basins, the sediments of which show little or no structuring. This activity failed to recognise the presence of the deeper and older Bamaga Basin and in 1984 Duyken-1, the only well so far in the Gulf of Carpentaria, tested the Carpentaria and Karumba sediments without success, but missed the unrecognised Bamaga Basin 120 km to the northeast. Poor quality seismic data and preconceived ideas `masked' the Bamaga Basin and it was only in 2012 that modern 2D regional seismic data followed by an infill seismic survey in 2014, revealed the presence of a sedimentary succession in the Bamaga, probably of early-middle/late Paleozoic age. The carefully processed new seismic data uncovers an intriguing, complex structural history, and large potential petroleum traps. Basin modelling in the centre of the Bamaga Basin where the sedimentary section is deepest shows that the sediments are mature for petroleum generation with the hydrocarbon phase being either oil or gas, although gas is more likely, especially below 2,000m. Analysis of the available data indicates that in the oil generation zone there are many targets each of which has the potential to hold Prospective Resources of more than 250 MMstb of oil, the largest of which could hold 660 MMstb oil. In the gas generation zone, there are also numerous targets, each with the potential to hold Prospective Resources of 1 Tcf or more gas, the largest of which could hold as much as 2.5 Tcf gas. The water depth (60m), closeness to shore (150km) and reasonable target depths means exploring the Bamaga Basin is operationally and commercially attractive.