Australia's petroleum potential in areas beyond an Exclusive Economic Zone

The United Nations Convention on the Law of the Sea gives Australia the option of proclaiming a Legal Continental Shelf around both the continent and its island territories, over which it would control exploration and exploitation of the natural resources of the seabed and subsoil. A Legal Continental Shelf is considered to extend throughout the natural prolongation of the land territory to the outer edge of the continental margin, which, where it extends beyond the 200 nautical mile limit (Exclusive Economic Zone - EEZ), is defined by a two-part formula based on measurements from foot of continental slope reference points. To fully use this formula, both bathymetric and sediment thickness information are required.  The area of a Legal Continental Shelf around Australia and its territories would be approximately 12 million km2 (about 1.5 times the area of the continent itself), which would be one of the largest Legal Continental Shelves in the world. Eight regions of this shelf, totalling more than 3 million km2, would extend beyond an EEZ.  Sediment thicknesses greater than 2000 m - sufficient to have generated hydrocarbons from any potential source rocks - occur in six of these regions: Lord Howe Rise / Norfolk Ridge, South Tasman Rise, Great Australian Bight, Naturaliste Plateau, Exmouth/ Wallaby Plateaus and Kerguelen Plateau. Most of the remote parts of the Australian margin with possible resource potential would lie within a Legal Continental Shelf.  Our relative rating of petroleum potential of regions beyond an EEZ is based on both a qualitative and quantitative assessment.  The potential petroleum recovery estimates are greatest for western Lord Howe Rise and the southern Kerguelen Plateau, but relatively high values were also obtained for the South Tasman Rise and the eastern flank of Lord Howe Rise. Of the deepwater ocean basin areas, the New Caledonia Basin has the greatest potential recovery, although the estimates are clearly unrealistically large. Small but potentially high-yielding basins, such as the Taranui Sea Valley on the Norfolk Ridge, are also of interest.  Over all, the assessment indicates that the western flank of Lord Howe Rise has the greatest petroleum potential, even though the relatively small size of some of its individual basins tends to downgrade the chance of finding giant and thus economically viable fields. However, this part of Lord Howe Rise appears more promising when the equivalent area and potential within an EEZ around Lord Howe Island are considered. The southern Kerguelen Plateau produced the largest potential petroleum recovery estimates of any of the moderate water depth regions; however, its real potential will remain unknown until its origin (continental or oceanic) and volcanic history are better understood.  Although the regions discussed are in relatively deep water (generally over 1000 m), they are not consistently any deeper than areas of plateaus and slopes within an EEZ, such as the Exmouth Plateau, which has been explored and drilled. Since areas with petroleum potential beyond an EEZ are remote, and in some cases in hostile environments, their exploration is unlikely to be economically viable in the near future; however, they may well provide Australia with a strategic resource into the next century. In the light of Australias dwindling petroleum resources, these regions should not be overlooked in long-term planning by government and industry.

Tags: Earth Sciences, GA Publication, Journal, Published_External
Organization: Geoscience Australia Data