AUSTRALIA has secured a potential oil and gas "bonanza'' after netting an extra 2.5 million square kilometres of seabed.

Exploration has already taken place in some of the areas that could potentially deliver the nation billions of dollars worth of oil and gas reserves and help secure its energy future.

The extension to Australia's territorial jurisdiction stems from the findings of a United Nations commission on the limits of the continental shelf and the ratification of the 1982 Convention on the Law of the Sea.

Sudden growth ... Australia's territory has been extended by 2.5 million square kilometres - indicated by purple shading.

The decision gives Australia the rights to whatever exists on the seabed in the area, including oil and gas, and biological resources such as micro-organisms that could potentially be used to develop medicines.

"Major boost"

Resources Minister Martin Ferguson said he could not put a figure on the potential oil and gas reserves contained in the areas, but that it was a major boost to Australia's offshore resource potential.

"The truth of the matter is that they have been hardly explored,'' he said.

"This is potentially a bonanza. We have got unknown capacity up there.''

Mr Ferguson said the UN decision means Australia now has jurisdiction over an area of the continental shelf that is almost five times the size of France, 10 times the size of New Zealand and 20 times the size of the United Kingdom.

Energy future

He said the decision also improves Australia's chances of securing its energy future, and that of other nations.

"As you can appreciate when you sit down and talk to countries such as Japan, Korea, India and China the big issue they want from us is security of supply and that goes to the energy security debate,'' he said.

"We do need to find another Bass Strait or alternatively develop alternative fuels, such as gas-to-liquids and coal liquids, because the issue of energy security goes squarely to the question of transport fuels.''

But the government has again ruled out exploration of the Antarctic mainland and waters around it.

"We have always acknowledged the Antarctic treaty and already have locked in as a nation no minerals exploration in that Antarctic region,'' Mr Ferguson said.

He also ruled out exploration of McDonald Island, west of Antarctica.

"We've always as a nation basically treated that as off-limits.''

Exploration already started

Mr Ferguson was unable to put a timeline on when oil companies might begin mining the seabed for oil or gas deposits.

However, some "pre-competitive'' exploration has already taken place, revealing the areas included in the extended jurisdiction have the potential to yield some major gas and oil finds.

Mining potential

Geoscience Australia geologist Mark Alcock, who was the project leader for the Law of the Sea and Maritime Boundaries Project, said the Great Australian Bight, Lord Howe Rise, south west of Lord Howe Island, and the Wallaby and Exmouth Plateaus all had mining potential.

"Surveys are being undertaken in the Lord Howe Rise region ... looking at the petroleum prospectivity of the seabed in that area,'' he said.

"It's one of the areas Geoscience Australia has been looking at for this pre-competitive work ... (and) there are similarities with areas that oil has been found in closer to Australia.''

Mr Alcock said that of greenfield areas that had been explored, the Great Australian Bight was considered to be quite "prospective''.

"The Great Australian Bight has been looked at to some extent (and) is probably considered a little more prospective than Lord Howe Rise - it's a bit more conventional as a place to find oil,'' he said.

He said the Wallaby and Exmouth Plateaus in the west also had potential.

Mr Alcock said it was possible that some of the areas under pre-competitive exportation could go to tender within the next couple of years.

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