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So far, Statoil’s conclusion is that the not been ready for this. It needs to has based a potential design (able to type of vessel it needs to remove and move more from a greenfeld industry handle modules on the project) on redeploy modules on sgard, particu- to a maintenance industry, and that the Subsea 7 vessel Seven Atlantic.

Å larly the compressor modules, is not requires quite a different mindset.” It would be 133.4m long, 28m wide, currently available. An “interim solution” will be used able to carry up to six modules on

Statoil is not alone. As part of for the installation of the compressor deck, and incorporating a moonpool

Intervention its own assessment of the potential train modules on sgard next year, that could take 12m by 6m by 12m

Å future use of subsea compression on Bjordal says. Technip, the installation modules.

the Ormen Lange feld, which came contractor, will use the DP3 North Sea Statoil has done a similar exercise. on stream in 900m (2853ft) water off Giant, built in 2011 with 2900sq m It says the vessel it requires, described

Norway in 2007, Shell Norske also of deck space, a 400-ton crane and as a subsea processing intervention concluded current IMR (intervention, an over-the-side, subsea handling (SPI) vessel, would need to be able to maintenance and repair) vessels would system designed specifcally for the work year round, in up to 4.5m waves, not meet requirements. sgard project. and lift modules of up to 400-ton and

Å

Speaking at Underwater Technology For future intervention work—lifting 15m-long by 12m-wide by 12m high.

Conference 2013 (UTC) in Bergen in and replacing modules—both Statoil It would also need to be able to exe-

June, Raimund Bjordal, technical lead, and Shell have looked at the use of a cute subsea processing-related activi- subsea processing intervention, at monohull vessel, with a focus on deck ties, including handling hydrocarbons,

Statoil, says: “We are moving towards space and a large moonpool. nitrogen gas, and MEG. This would a complete subsea factory and we Shell has looked at existing con- require MEG and nitrogen pumping need to take the next step, we need struction and IMR vessels and their spreads, a reclaimed oil sump, and a an intervention vessel that can handle capacities, including the Skandi cold fare system. what is needed for the subsea compres- Achiever, the Island Constructor and Potential options assessed by sion plant and also for future subsea the Viking Poseidon. Statoil include a construction vessel templates.” Mathias Owe, Ormen Lange subsea with over-the-side handling system

Jarand Rystad, managing partner, compression project manager, says the or a newbuild vessel with a large

Rystad Energy, says that the time has options are to agree to a contract for moonpool. already come, however. use of a newbuild, or conversion, with However, Statoil, which has plans “Now [existing] subsea installa- a vessel operator such as Subsea 7, or to have a complete subsea factory by tions are starting to mature, we are to build a new ship, potentially coop- 2020, says that any new vessel would starting to see all of the problems we erating, or sharing it, with Statoil. still work in tandem with a standard have already seen on the topsides for a In case it decides to use subsea IMR vessel to ensure fast turnaround of number of years,” he told UTC attenees compression on Ormen Lange, Shell a module replacement. in Bergen. First, an IMR vessel would mobilize “To be honest, the [subsea] to the feld to perform preparatory industry has work, including displacing with MEG, any hydrocarbons within the module that needed to be removed.

During this time, the SPI ves- sel would mobilize from a base at Kristiansund, on the coast of

Norway, with a replacement module.

Upon arrival in feld, the SPI vessel will lift out the discon- nected module and place it on a subsea “parking frame,” outside the compression station. The replace- ment module would then be installed into its slot in the com-

The Åsgard subsea pression station and compression frame commissioned. with its modules

Each module will be ftted using installed, illustration. vertical connections to a cassette base

Credit: Statoil.

frame within the subsea compression station and interconnected to other modules using sliding spools.

OE | August 2013 oedigital.com 56 054_OE0813_Intervention-Asgard.indd 56 7/22/13 5:22 PM