Australia's shale gas potential is thought to be as large as that of the United States, where shale gas has transformed its energy sector.

But experts says Australia is at least 20 to 30 years behind the U.S in developing shale gas for export.

Shale gas is extracted through, sometimes controversial, chemical or hydraulic fracking, unlike CSG which taps coal seams.

Australia has already spent $200 billion developing CSG, and Professor Stefaan Simons, of the International Energy Policy Institute (University College London, Adelaide Campus), says shale gas could cost billions more.

"There's very little infrastructure, formations are very deep underground, four kilometres underground," Prof Simons said.

"We're talking about massive investment to be able to get at that gas.

"So I would guess at least double that figure."

The Queensland Energy Minister Mark McArdle told the Australian Domestic Gas Outlook Conference in Sydney, his state's investment in developing CSG was in the order of $60 billion, and nationally the figure was $200 billion.

He was excited by the opportunity for Queensland to supply 10 per cent of the global gas demand, and he disagreed with the calls to reserve gas for the domestic market.

He argued it should be sold for the best price, on the international market.