Meet Allseas’ Pioneering Spirit, the largest offshore construction vessel in the world, and the key to Esso’s plans to decommission several oil rigs in the Gippsland Basin.
After delivering energy to Australia for over 50 years, many of the Bass Strait oil fields are reaching the end of their productive life. That’s why Esso and parent company ExxonMobil have launched the first Gippsland Basin decommissioning campaign to lay these retired assets to rest.
The project entails the removal of the topsides of 12 facilities, the removal of two monotowers, and the removal of the upper jacket sections of 10 steel piled jacket facilities. All in all, that equates to around 60,000 tonnes (t) of steel.
Work will be conducted up to 77km offshore, in depths ranging from 38m–94m, with the enormous structures to be offloaded to Barry Beach Terminal in southern Victoria, where they will be segregated and dismantled for recycling and disposal.
Esso has contracted Allseas Marine Contractors Australia for removal and transportation works, with preparation activities slated to commence in late 2026.
But how do you go about dismantling these massive structures in one of the world’s most notoriously rough stretches of ocean?
You call in the big guns.
Allseas’ Pioneering Spirit is the largest offshore construction vessel in the world.
Capable of lifting topsides of up to 48,000t in a single lift, she makes offshore installation and decommissioning easy, allowing the work to be moved onshore where it is safer and more cost-effective.
The gargantuan ship is 382m long and 124m wide. At the bow is a slot, 122m long and 59m wide, that enables Pioneering Spirit to manoeuvre around a platform for lifting and transportation, using eight sets of horizontal lifting beams.
Two additional lifting beams at the vessel’s stern enable the removal and installation of jackets up to 20,000t.
Complementing these lifting systems is a special-purpose crane with a lifting capacity of 5000t for lighter loads.
Pioneering Spirit has lifted well over 330,000t of lifted platforms since its launch in 2016, including the single-lift removal of Shell’s 24,000t Brent Delta platform in the North Sea, and the set down of Equinor’s 22,000t Johan Sverdup topsides in Norway.
And in 2027, she’s Australia-bound. The vessel is expected to be in the field for roughly four months, operating on a 24-hours-per-day basis.
But she won’t be coming alone. Pioneering Spirit will be preceded by a number of Allseas’ construction support vessels. While perhaps less glamourous than the record-breaking Pioneering Spirit, these ships are no less critical to the Gippsland decommissioning project. They will arrive in the field in 2026 to commence preparatory works.
Once removed and transported closer to shore, topsides and steel substructures will be carried by barge and tugboats to Barry Beach Marine Terminal, where the structures will be offloaded, segregated and dismantled for recycling and disposal.
“Esso will utilise its existing port facility at Barry Beach Marine Terminal, which has been part of South Gippsland’s industrial precinct for over six decades,” an Esso spokesperson told The Australian Pipeliner.
“The terminal was where the majority of our offshore platforms were constructed and significantly, this is where they will return to be recycled as a brand-new decommissioning industry is born in South Gippsland.
“Esso is excited by this opportunity to continue working with the Gippsland community and workforce. We are committed to developing the skills required for this decommissioning project, which will be the first of many similar projects to be completed across Australia.”
Detractors have voiced concerns around the project’s proximity to a Ramsar-protected wetland, but Esso maintains that it is taking great care to minimise the risks.
“Following a thorough assessment of responsible decommissioning options and stakeholder engagement, our plan delivers an equal or better environmental outcome and will see the vast majority of each of the steel platforms removed from Bass Strait,” Esso said.
“The platform structures … are over 95 per cent steel, all of which is planned to be recycled.
“All dismantling activities will be completed responsibly in full compliance with environmental regulations and in a timely manner.
“We have already safely completed over $1 billion of decommissioning work across our offshore operations, including the plug and abandonment of over 100 wells.”
As legacy oil and gas assets reach the end of their lifespans, industry will need to collaborate with regulators and other stakeholders to ensure decommissioning takes place in a timely and cost-effective manner with minimal impact on the environment.
And while the curtain closes on these Bass Strait rigs, the comeuppance of Gippsland’s decommissioning industry is proof that the close of one chapter is merely the beginning of another.
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