The state's government moved quickly following Geoscience Australia's classification of a number of new outcrops on the Sreingapatam and North and South Scott reefs as islands, making them WA territory, prompting major changes to Commonwealth offshore coastal waters boundaries in May.

The new finding means WA owns the outcrops, which GA found were above the high water mark on North Scott Reef, a group of atoll-like reefs on the edge of the continental shelf in the Timor Sea.

WA was originally allocated just a 5% share in the Torosa gas field as it was so far off the coast, about 300km northwest of Cape Leveque; while the rest went to the Commonwealth.

WA Mines and Petroleum Minister Bill Marmion said his department worked with federal government agencies on the changes, which not only extend WA territorial waters but promise an increase in petroleum royalties for the state when the gas fields are eventually developed.

Estimates put WA's new share of royalties between 50-65%, whereas the original proportion within WA waters was between 5-15%.

Woodside is progressing floating LNG as the preferred development concept development to commercialise the Brecknock, Calliance and Torosa fields in Browse Basin that are estimated to collectively contain 2C resources of 14.9 trillion cubic feet of dry gas and 441.2 million barrels of condensate.

Marmion said that while the new territorial legislation promised good news in the future for WA taxpayers, it also helped the government's cause of minimising sovereign risk in the mining and petroleum sectors.

"We are now working with clearly defined boundaries in the Browse Basin," Marmion said.

The Torosa retention leases are due for renewal on December 24.

"I congratulate the Department of Mines and Petroleum on its work to expedite these changes, which involved extensive consultation across industry and government," Marmion said.

Woodside operates the three fields on behalf of its Browse LNG JV partners: Shell, BP, Japan Australia LNG (MIMI Browse) and PetroChina.

The project entered its second basis of design phase in September 2013, targeting final investment decision for the second half of next year.

An earlier plan to develop an onshore LNG hub at James Price Point was considered uneconomic.

Marmion added that while it was "too early to speculate" on the royalty potential of ConocoPhillips' nearby Kronos and Poseidon fields, he said it "could be significant".

The Greater Poseidon fields are expected to be developed via a longreach pipeline to provide gas to the Darwin LNG plant.