A unique project between Western Australia : Energy Research Alliance (WA:ERA), Woodside Energy and the Australian Maritime College (AMC) is investigating joining together two 330 metre oil tankers into a catamaran configuration to act as a floating gas processing facility. At around 640,000 tonnes, it would be the largest operational vessel in the world and could lead to huge changes in the way massive remote offshore gas fields are developed.

Work began in January 2008, with initial testing in July and, most recently, testing of a fully-painted four metre visualisation model was undertaken at AMC’s model basin in November.

Stemming from an idea by WA: ERA Chief Executive Dr Ian Finnie, the project was initially sponsored by Woodside with the aim of engaging students in some industry-related engineering problems. That objective has already been achieved, with a team of academics and students combining to develop the concept. However, initial successes have meant that the project has taken on a life of its own.

Dr Finnie says that the idea of a floating LNG facility is nothing new with mono-hull research underway, but the concept of an LNG or gas-to-liquids catamaran, with its inherent stability and greater storage capacity, is something entirely fresh.

“Currently, there’s a lot of infrastructure between the reservoir and the export facility,” says Dr Finnie. “So what this floating concept provides is all the aspects in one facility. You don’t need a pipeline and what would otherwise be an onshore facility is floating at the site."

Dr Finnie acknowledges the challenges of the project and says that while the reality of a gas catamaran is some way off, the potential development of floating LNG in the next few years means that it is worthwhile investigating all offshore gas development options.

“The reason, I think, why these obvious ideas don't exist in reality is because people reach the too hard basket and it doesn't go further. But what we're doing is just proving the fundamentals there and just doing some reality checks to establish the viability in this particular case.”

A fundamental component of the gas catamaran project is working out the vessel’s ability to withstand certain weather conditions. Models have been tested at the model test basin with very pleasing results, according to AMC lecturer and researcher Dr Giles Thomas. Dr Thomas, naval architecture student Alexandra Ford, and ocean engineering student Landon Kibby have been looking at the motions and loads the gas catamaran would face in waters off Western Australia’s coast.

“It’s a very innovative concept using two large crude carriers, retro fitting them into a catamaran configuration, but the big question marks have been a) how good are the motions and b) what the loads can be on the structure from the waves,” Dr Thomas said. “They are the two main things we’ve been looking at, but in order to do that we’ve had to develop the concept design to a reasonable level of detail to ensure it’s the correct size for storage and displacement in terms of dead weight it would have to carry.”

He said conditions simulating 20 metre waves and 100 knot winds had been produced in testing the gas catamaran.

“You never really know the exact weather conditions so that’s why, when designing offshore structures, there is a tendency to work to what is called return period storms. These are worked out statistically as to what would be the worst storm experienced once every 100 years. From there, the worst possible storm once in 1,000 years or once in every 10,000 years can be worked out. Storms are getting progressively worse, but you never actually know when they are going to occur. We’ve done testing of the gas catamaran up to the one in 10,000 year storm. That’s really the kind of level you’d be looking to design this structure to withstand.”

Dr Thomas says that because the project is an entirely new concept many complications have arisen. All aspects of the project are covering new ground and any data collected has unique value. Given the strong results in the test basin, the next stage will involve Prof. Andrew Deeks from the University of Western Australia (UWA), who will look into the structural engineering side of the project.

“The next stage we’re looking at involves developing a long term research project in collaboration with UWA, and obviously with Woodside, to provide a more detailed look into loads and structural configurations that would work. That’s probably the biggest thing – coming up with something that’s actually going to be able to withstand the severe weather conditions that a structure like this might be exposed to,” Dr Thomas says.

He adds “It’s the first time that this type of work has been done on a big catamaran hull form so in order for us to actually do it and measure the loads and achieve good results has been a very nice development. The data that we’ve got is incredibly valuable. Now, knowing what those loads are we can extrapolate those up to full scale and help with the structural design process.

“Although construction of the final facility will be a challenge, Dr Finnie is convinced that it is entirely achievable using existing infrastructure. There are some issues to work through in that regard but the main thing is to demonstrate in simple terms that it will prove to be a concept that can be made to work.”