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A&P Completes Mid Water Arch Subsea Structure

11 August 2011

A&P Tyne is building on its success in a new business sector with the completion of yet another subsea structure for an offshore oil and gas field.

The Mid Water Arch used to support control cables as they rise from the seabed to the surface left the ship repair and fabrication yard at Hebburn, bound for a North Sea oil field.

For the last six months, 50 men worked daily on the project to cut, shape and weld the shell-like structures wrapped around two pressurised buoyancy cylinders. The entire structure is built in steel and the yard also built the gravity base, clump weights and piles that will secure it to the seabed, weighing a massive 600 tonnes altogether.

The subsea arch is headed for the Athena Development in the Outer Moray Firth, which will be operated by Ithaca Energy. The field is expected to produce around 22,000 barrels of oil per day once production starts.

It is the second such order secured by A&P, earlier this year it completed two buoyant subsea structures for an African offshore oil field.

Project director Iain Campbell said: "This job was totally different in that the Athena arch is supported by pressurised steel cylinders as opposed to the polymer buoyancy units the earlier subsea arches were built around.

"The pressure vessel buoyancy tanks are a new design and required very high standards of welding and fabrication. In fact the project required us to meet extremely high standards in all aspects.

"As its suspended underwater the arch is painted to NORSOK coating standards so it will last for 25 years.

"It was very challenging but everything came together and the whole project went extremely well.

A 1000 ton crane was needed to lift the bright yellow subsea structure which is 17 metres long, 15 metres wide and 7 metres high onto a barge to sail up to a yard in Invergordon for final assembly. The base, clump weights and piles are to follow today on a coaster.

The Athena field is due to start production towards the end of this year and when it does the subsea arch will support control cables from the well-heads to the floating production, storage and off-loading vessel on the surface.

Mr Campbell added: "Towards the end of the project we were working on it around-the-clock to incorporate additional design changes and ensure it was ready in good time.

"The oil and gas sector is an expanding market for us and one we are handling very well, delivering quality products to a high-standard, within a tight timeframe.

A&P Tyne Sales & Marketing Manager Martin Robertson said: "Its the first Mid Water Arch of its type that weve built at the yard and its gone extremely well.

"Its another step into an important new market for us and the successful completion of each order helps grow our reputation.

"We are in discussions with a number of potential clients in the oil and gas sector and are looking forward to securing more work of this type.