‘Largest ever subsea structure’ at Ichthys

The INPEX-operated Ichthys LNG project in Australia today successfully installed its Riser Support Structure (RSS) tower at the Ichthys field.

The safe installation of the 6,500 tonne structure by the deepwater construction vessel Aegir marks the beginning of the project’s major installation campaign in the Browse Basin, offshore Western Australia.

Ichthys LNG project Managing Director Louis Bon said the RSS is the largest subsea structure ever laid on the seabed.

“The Riser Support Structure is the masterpiece of the project’s subsea facilities,” Mr Bon said. “It is also a serious physical foundation, because when its arch is placed, the structure will stand 110 metres off the seabed.

“Today’s milestone is significant for the project, because it marks our return to the Ichthys Field for the installation of our offshore facilities after years of intense engineering and fabrication work.”

The completed RSS will be a physical, fixed support for flexible risers and dynamic umbilicals that connect subsea gathering systems to the project’s semi-submersible central processing facility (CPF), currently under construction in Korea.

Exciting time

Ichthys LNG project Offshore Director Claude Cahuzac said it was an exciting time for the project as facilities and structures started to move from construction yards around the world to the Ichthys field.

“The RSS is an integral piece of the subsea field architecture, as all other subsea structures and the CPF mooring system will be installed and oriented relative to its location in the Ichthys gas-condensate field,” Cahuzac said.

“To give a sense of scale, that’s about 30,000 tonnes of subsea equipment that will be installed during the offshore installation campaign in water depths of around 250 metres.

“This campaign includes the installation of the RSS, subsea manifolds, about 41 kilometres of flexible risers and pipe, and about 141 kilometres of rigid flowlines.”

The Aegir arrived at the Ichthys Field in mid-October to begin the pipelay campaign and to perform the RSS installation. The overall offshore installation campaign is planned to be a continuous 12-month program of work.

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