An historical achievement for offshore developments at Wheatstone

The topsides structure being installed offshore WA.

The topsides structure being installed offshore WA.

In what is one of the world’s largest ever offshore platform installations, in May this year Chevron Australia successfully installed the Wheatstone Project’s platform topsides approximately 225 km offshore the Pilbara Coast, Western Australia.

The 37,000 metric-ton topsides structure was built in a South Korean shipyard before being shipped on the Heerema 851 barge 6,546 km to Western Australia, where it was successfully floated over and set onto the steel gravity structure.

The topsides was transported at its full height across the open sea to Australia so that it could float above the legs of the steel gravity substructure (SGS) for installation.

In what is another first for Chevron, the platform uses a steel-based sub-structure to support the topsides facilities, which is a unique way of resolving technical foundation design challenges while providing cost savings over alternatives.

Upon arrival in Australia, mooring patterns were set up around the SGS for the topsides, with the barge then aligned and moved in on mooring lines between the SGS legs.

It was then lowered off by a ballasting of the barge into its final location, until the topsides load was fully taken by the SGS.

The full platform measures 225 m tall from the base of the steel gravity structure to the top of the flare boom, and is designed to withstand 12 storey-high waves.

A MAJOR UNDERTAKING

In order to be loaded onto the transport barge, the topsides were raised on four jacking towers to a height of 20 m, before being lowered onto the deck support frame, with the combined structure then shipped out on the Hereema 851 with a total weight of nearly 45,000 t.

“This is a significant achievement and milestone for the Wheatstone team,” said Roy Krzywosinski, Managing Director, Chevron Australia. “It is the culmination of years of planning and collaborative execution by Chevron and our various contractors.”

“We’re dealing with one of the biggest platforms in the world,” Wheatstone Project Platform Manager Mike Watkins said. “The engineering that goes into this has taken a couple of years, at least, to get all of these plans together.”

WHAT’S NEXT?

Following the installation of the topsides, commissioning is due to be undertaken on the hydrocarbon, support, and utility and habitation systems.

No hydrocarbon production systems will be operational during hook-up and commissioning (HUC) activities.

Temporary and permanent accommodation facilities on the topsides will be brought progressively online during HUC activities. An accommodation support vessel will provide temporary accommodation for up to 440 personnel for approximately six months during hook up of the topsides to the SGS.

Following this, the standby period will commence, and continue until operations begin, although the duration of the standby period is dependent on the readiness of both the offshore and onshore operations.

KEY PARTICIPANTS

Clough secured the contract to provide an independent commissioning team to assist with pre-commissioning and commissioning of the integrated float-over deck systems, offshore hook-up and start-up assistance.

Heerema Marine Contractors (HMC) was contracted by Daewoo Shipyard and Marine Engineering, who were contracted by Chevron for the engineering, fabrication, installation and transportation of the platform.

HRC also engaged Strategic Human Resources to provide industrial relations, immigration advice and support for the installation.

Bechtel is the engineering, procurement, construction and commissioning contractor for the downstream scope of the project.

FIRST GAS IN SIGHT

Over the next six months, Chevron Australia and its contractors will undertake hook-up and commissioning activities as the Wheatstone Project continues toward first gas in late 2016. At the time of writing, the project was around 60 per cent complete.

The Wheatstone Project will be one of Australia’s largest resources projects, located at Ashburton North Strategic Industrial Area, 12 km west of Onslow in Western Australia’s Pilbara region.

The foundation project includes two LNG trains with a combined capacity of 8.9 MMt/a, along with a domestic gas plant.

Joint venture participants in the project include the Australian subsidiaries of Chevron (64.14 per cent), Apache Energy (13 per cent), Kuwait Foreign Petroleum Exploration Company KUFPEC (13.4 per cent) and Kyushu Electric Power Company (1.46 per cent), together with PE Wheatstone Pty Ltd (part owned by Tokyo Electric Power Company, 8 per cent).

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