Exxon Mobil and BHP Billiton have submitted to Australia's federal environment department plans for a $10 billion floating liquefied natural gas production facility for their proposed Scarborough joint venture.

The Scarborough gas field, located in 2,953 feet of water 186 miles off Western Australia in the Carnarvon Basin, is a 50-50 Exxon-BHP Billiton venture. It holds an estimated 8 trillion-10 trillion cubic feet of lean gas, Platts reports.

The documents say the floating platform, 1,624 feet long and 246 feet wide, would contain the necessary equipment for gas treatment, liquefaction and transfer into vessels that will ship the product to market, The Age newspaper reports.

Shell has started construction on what it has said is the world's first FLNG vessel to develop its Prelude field in the Browse Basin off Western Australia. The Exxon-BHP floating platform would be 23 feet longer than Shell's.

The documents say the FLNG facility would be capable of producing 6 million-7 million tons of LNG a year. Shell's Prelude FLNG facility will produce 3.6 million tons of LNG a year as well as valuable liquids.

Shell's Prelude was the world's first FLNG project to reach a final investment decision, in May 2011. It is under construction in South Korea.

The first wells at Scarborough are likely to be drilled in 2018 and 2019, with production beginning in 2020 at the earliest, Exxon and BHP said in the filing.

''The Scarborough gasfield has an expected producing life of approximately 25 to 35 years,'' the companies said.

During commissioning, up to 600 people would work on board the Scarborough FLNG vessel with an operational workforce of about 200 people.

A floating processing facility eliminates the need to build an onshore hub, thus avoiding a number of environmental and landowner issues facing rival LNG projects such as Woodside's Browse gas venture.

"Given the remote location of the Scarborough gas field and reservoir characteristics ... FLNG technology is currently deemed the most appropriate technology to develop the field," Exxon, the operator of the project, said in the approval documents.

Western Australian Premier Colin Barnett has pushed for onshore, rather than floating, processing of gas from the Browse LNG project, arguing that offshore would deprive the state of jobs and economic benefits. But he has previously cited Scarborough as an example of a project unlikely to be developed through onshore processing.