With power generated from offshore wind farms forecast to grow from 3GW to 75GW over the next decade, operators are looking to tried and true oil & gas practices to help reduce construction costs. Russell McCulley speaks to Canyon Offshore about how the company is adapting its trenching practices for the renewables market.
Early next year, Canyon Offshore will take delivery of the Grand Canyon, a newbuild offshore construction vessel that will host the new T1200 jet trencher and a pair of 200HP XLX ROV systems. The Grand Canyon, a 125m x 25m DP3 vessel designed by Skipsteknisk, will come equipped with a 250t crane, moonpool and helideck, accommodations for 108 and under-deck stiffening to support the weight of trenching system, reeled lay system and carousel to be mounted on deck.
If it sounds like a vessel more suited to heavy-duty oil & gas operations, that’s the point, says Canyon Offshore general manager for renewable energy Gary Aylmer. ‘We’d been looking at the renewable industry year on year for the last few years, and it’s never been mature enough to warrant the spread rates that we would charge,’ Aylmer points out.
But what’s happened over the last few years is, every single [offshore wind] project has overrun for a number of reasons.’ The chief cause of cost overruns is, paradoxically, the use of low-cost, low-specification equipment, he says: in particular, standard barges to conduct turbine and cable installations in shallow water, where DP vessels cannot navigate. ‘But what’s happened is, as those barges start to go further offshore, they get further affected by the weather. Obviously, they’re not as easy to manoeuver on anchors. The same is true for burial equipment. It used to be diver-operated, but now [the UK Health & Safety Executive] requires less use of divers.
‘With lessons learned after each project, the industry has asked: “OK, is there a better way to do this? Should we adopt more of the oil & gas approach? Who do we need to be speaking to?” So we find ourselves being approached more and more by people asking: “Would you be interested in bidding for this renewable job or helping us on an existing job?”’
‘With lessons learned after each project, the industry has asked: “OK, is there a better way to do this? Should we adopt more of the oil & gas approach? Who do we need to be speaking to?” So we find ourselves being approached more and more by people asking: “Would you be interested in bidding for this renewable job or helping us on an existing job?”’
Canyon’s most significant foray into the renewable energy market came in 2010, when the company worked with cable manufacturer and installer ABB during installation of the 260km BritNed high voltage subsea cable between converter stations on the UK’s Isle of Grain and the Maasvlakte near Rotterdam in the Netherlands. The job led to an agreement earlier this year between the two companies in which Canyon Offshore will provide trenching services to support ABB’s subsea high-voltage cable installation projects. The company recently deployed its T600 jet trencher to the Greater Gabbard project for Fluor, with the i-Trencher and T750 jet trencher scheduled to start work on the project in 4Q 2011. Work scope includes burial and survey of the interarray cables that compose the grid connecting offshore wind turbines to each other and to a transformer station.
‘Moving forward, we’re focused on the installation and burial of inter-array cables,’ Aylmer says. ‘These things can be anywhere from 500m to 1000m long – the distance between the turbine towers. We think that one vessel of suitable size can install the cables and also have the burial assets on board. Instead of having to use two vessels, you can have one.’
To that end, the Grand Canyon and sister vessel Deep Cygnus, both from Volstad Shipping Norway, will have on deck equipment long used in oil & gas trenching operations. The vessels will have options to host Canyon Offshore’s T750 and the i-Trencher for heavy soils, the new purposebuilt T1200 jet trencher and new 200HP Triton XLX work class ROVs for survey work and debris clearing. The i-Trencher is capable of cutting with digger chains, while the T1200 trenching system, from Perry Slingsby Systems, builds on the T750, which has been part of Canyon Offshore’s fleet since 2004. The burial assets will be able to monitor and log depth of burial during trenching, cutting costs by avoiding posttrench surveys.
‘Our objective when we designed T1200 with the manufacturer was to improve on T750.’ Aylmer says. ‘We couldn’t better a lot of the fundamental aspects of the design. The T750 and T1200 are much alike; however, the T1200 has significantly more jetting power – 1200HP – and is rated for 3000m. That may not be relevant in the renewable market, but we have an eye on some projects in the Gulf of Mexico.’
Like the T-750, the T-1200 incorporates a duplex stainless steel chassis and surface VSD transformers infinitely controlling the directly coupled water pumps and will operate up to 30% faster than the T-750 model, Aylmer says. ‘The driver on wind farm projects, as with any industry, is to keep the cost base as low as possible,’ he says. ‘One way to keep costs down is to trench faster and remove the need for post-trench survey.’
In addition to inter-array cables, the Grand Canyon and Deep Cygnus will be used to bury inter-country pow cables, Aylmer says. Having two trenchers onboard will enable teams to tackle almost any soil type encountered during long cable laying projects.
The Grand Canyon will differ from most DP3 vessels in that the thrusters are configured for use in shallower depths. ‘Grand Canyon has no azimuth thrusters forward,’ Aylmer says. ‘She’s got four tunnel thrusters’, allowing good DP capability in the relatively shallow depths where most wind farms are currently located. ‘By having four tunnel thrusters, we can quite happily sit in 10m, 11m and keep a very good DP footprint,’ he says.
‘It’s all about matching the right assets to the right projects,’ Aylmer continues. ‘What we’re seeing moving forward is that projects in 2013 and beyond are in water depths of 20m to 30m – ideal depths for a DP vessel, and where flat-bottom barges would be at a disadvantage.’
The under-deck stiffening on both Grand Canyon and Deep Cygnus speeds mobilization and demobilization by allowing Canyon Offshore to stock the deck with more equipment. ‘The aim will be to bolt as much as possible down to the vessel,’ Aylmer says. ‘We will avoid a lot of hot work, take away some safety issues and, more important, reduce the amount of time’ needed to complete jobs.
The company is in the early stages of negotiations that would add a third sister vessel to the fleet, also with under-deck stiffening, as early as 2013. In the meantime, the AMC Connector, another newbuild designed for both renewable energy and oil & gas subsea construction and installation, will come into service early next year. To be operated by Emas AMC, Connector will carry two turntables for high voltage power cables or subsea umbilicals and will be capable of operating in water depths of up to 3000m. ABB has secured the vessel for installation work in 2012 and 2013.
‘There’s massive growth in the amount of wind turbines that are going to be installed around Europe’ in coming years, Aylmer says. ‘The UK, Germany, Netherlands, France, and Belgium are all big growth areas for the foreseeable future.’
Canyon Offshore, with the financial backing of parent company Helix Energy Solutions Group, is planning to keep ahead of a potential choke point in the supply chain for renewable energy installation equipment, Aylmer says.
‘There are limited trenching assets out there’ for offshore wind energy installations, he says. ‘Most up and coming companies are venture capitalist-funded. To build a purpose-built trencher requires in the region of 15 to 20 million [dollars]. A lot of companies are reluctant to take that risk.’
Canyon is also betting that offshore renewable energy developers will continue to seek out the expertise, and assets, of companies with extensive oil & gas experience.
‘It’s about using the right vessel and trencher for the job,’ Aylmer says. ‘When you get into water where you can use a DP2/DP3 vessel, a high standard vessel that’s quiet clean and has great accommodations will greatly improve productivity.’ OE
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