This frontier area is easily accessible about 150km from shore in water depths of no more than 70m. More to the point, it is directly in the path of the Weipa-to-Gove spur of the proposed PNG-Australia gas pipeline.
Gulf Energy has a 100% interest in the whole basin which is enclosed in Queensland permit Q23P extending from a point about 120km west of Weipa on Cape York as far north as the international sea boundary with Papua New Guinea.
So far work has focused on seismic reprocessing, but the company is now preparing a program of new seismic acquisition for the first half of 2006 to advance several potential leads to drilling stage. It is looking for a farminee to help continue this exploration and has already attracted interest locally, and from the UK and Asia.
Gulf Energy is also deciding whether to go to a float and public ASX listing next year or whether to stay a private entity.
The Bamaga Basin story began in the early 1990s when a joint effort from Geoscience Australia and the Queensland Department of Resource Industries reprocessed and re-interpreted 1980s seismic data as part of a study of the hydrocarbon potential of the Mesozoic-age Carpentaria Basin.
The region has only one offshore well. Shell’s Duyken-1 in 1984 located almost dead-centre in the Gulf drilled into a basement high without even testing the Mesozoic. This seemed to confirm conventional wisdom that the Jurassic and Cretaceous sediments in the Carpentaria Basin were too thin and that they lay directly on basement rocks.
Most of the early seismic was aimed at the Mesozoic section, so the data that penetrated below this was hazy. But there were hints of underlying structure, particularly in the northern part of the region.
The resultant study delineated a new north-south trending feature bounded by faults under the Mesozoic unconformity which the Geoscience Australia/Department of Resource Industries team described as a sag basin and named Bamaga. Its Paleozoic age was inferred from sediments of similar age on and offshore in areas adjoining the Gulf.
These results were published in an APPEA Conference paper in 1993 where they caught the eye of former Esso exploration geologist Wolfgang Fischer.
He and others formed Gulf Energy to look at the new basin in more detail. The seismic lines were on public file and Gulf could discern the potential for big structures. But opinions about the sediments involved varied from metamorphosed material offering no petroleum potential to the possibility of a Permo-Devonian section with source and reservoir rocks.
Several onshore wells drilled in the Carpentaria region during the 1960s had recorded oil and gas shows. In addition, following the GA/DRI work Comalco had taken up an exploration permit in the Gulf in an attempt to find oil and/or gas to use as an energy source for its bauxite mining operations at nearby Weipa. Comalco carried out some maturation modeling in the region and found conditions favourable for petroleum generation.
With this potential in mind Gulf Energy applied for and received permit Q23P which covers about 1500 square kilometres – virtually the whole of the newly delineated Bamaga Basin. The work program terms were modest, requiring only seismic reprocessing and acquisition of some new data in the first three years.
Sydney-based International Geophysical Consultants (IGEC) was contracted to analyse Geoscience Australia’s magnetic and gravity data for the area and then reprocess the seismic data.
The gravity indicated the presence of intrusive granitic masses which suggests that there was heat flow in the region and the possibility of sustaining temperatures sufficient for petroleum maturation.
The magnetic data indicated structural anomalies that showed a close correlation to structures interpreted from the reprocessed seismic lines. It seems probable that the basin has basement-related structuring.
This work was followed by depth-to-basement calculations that suggested the Bamaga Basin could contain sediments between 1000m and 3500m thick.
The seismic reprocessing has taken longer than expected due to some poor quality sections, but overall, it too has painted a positive picture with discernable structures present.
Wolfgang Fischer and his colleagues in Gulf Energy are fully away that the Bamaga Basin is far from proven in petroleum terms and the area represents a very high risk. But it also offers explorers the potential for high reward without the need to outlay the huge sums that are needed in ultra-deep water offshore plays.
The water is shallow and the permit is not far offshore, hence exploration costs will be moderate. The discovery of oil or gas will be marketable given the mining, fishing and agricultural industries already located in the Carpentaria region and the probability of the PNG-Queensland gas pipeline being laid through the area.
Ideally Gulf Energy would like to have a farminee or the float option in train to move into the next phase of Bamaga Basin exploration by the end of the first quarter of 2006.
