Inpex completed the offshore pre-lay of the 77km chain and cable mooring system for its Ichthys LNG project in the Browse Basin, located off the northern coast of Western Australia.
As part of the mooring system, 49 chains were laid on the seabed in water depths of up to 250m and anchored to foundation piles—5.5m in diameter and 63m long.
The mooring system will secure the project’s two massive offshore facilities—the central processing facility (CPF) and floating production, storage and offloading (FPSO) facility—in the Ichthys Field seabed for at least 40 years of continuous operation.
Once located in the field, the CPF will deliver natural gas and some condensate through an 890km subsea gas export pipeline to onshore processing facilities in the Northern Territory. Most condensate will be processed through the FPSO and shipped directly to market from the field.
Supplying more than 40,000-tonne of large-scale anchor chains for the project represented nearly 18 months of worldwide chain production. Each chain link weighs more than 700kg.
The 28 CPF mooring chains required more than 25,000 tonnes of mainly 178mm diameter chain, while the 21 FPSO mooring chains needed more than 15,000-tonne of mainly 161mm diameter chain.
The mooring system is part of the complex network of subsea infrastructure and equipment across the Ichthys Field.
Ichthys Project Managing Director Louis Bon said the mooring system pre-lay was a significant undertaking with challenging soil conditions for the piling scope of work.
“Despite the difficulty of the task, I’m proud to say that it was successfully completed without a single lost time injury or any harm to the environment,” Bon said. “For example, because the Ichthys field is located just 120km from the main hump back whale migratory routes and calving grounds of North West Australia, an early decision was made to avoid pile driving during the whale calving period where associated underwater noise may have created a disturbance.”
Bon said the successful completion of the mooring chains pre-lay marked another major step ahead of the arrival of the CPF and FPSO currently under construction in ship yards in South Korea and, once completed, will be towed 5600km to the Ichthys Field.
"The offshore facilities will operate for decades and the mooring system plays a key role in ensuring their integrity,” he said.
In addition to the mooring system, more than 16,000-tonne of subsea structures and 140km of rigid flowlines have been installed across the Ichthys field to safely and efficiently extract gas and condensate.
Image from Inpex.
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