September 8 - Earlier this year, SAL Heavy Lift's vessel Svenja was chartered by Crowley for the installation of the development platform within the Kitchen Lights Unit #3 (KLU) - a petroleum exploitation area of Deutsche Oel & Gas, spanning 337 sq km, in
The development platform consists of three main parts: the monopod - a 45 m high steel base, which will ultimately bear the load of the whole construction; the king pile, which is driven into the seabed and works as a central pole to stabilise the load; and the topside, which also includes a helideck.
Svenja was mobilised in Singapore, before sailing to the Cook Inlet for a period of around five months. Extra living quarters were required to house the 60 supporting team members required to complete the complex project.
"The KLU project included several challenging tasks for our engineering department," said Karsten Behrens, general manager, engineering at SAL. "It was necessary to design and calculate a special mooring arrangement for Svenja to fully comply with the US Jones Act on the one hand and to guarantee the vessel maintained an accurate position, despite the extremely strong tidal currents and small tidal windows on the other."
The special mooring arrangement was exclusively designed for the vessel and comprised of ten pre-installed anchors strategically located on the seabed; while ten winches and wires that connected to the anchors were installed onboard the heavy lift ship. This configuration provided safe and secure mooring along with precise positioning of the vessel, explained SAL.
Once Svenja was secured within the mooring pattern, the vessel's first job was to drive the king pile to the required depth, which involved the use of a large hydro hammer.
With the king pile in place, the 1,100-tonne monopod was transported alongside Svenja by a barge and then lifted onto the deck for additional preparations, before being lowered onto the seabed using the vessel's two 1,000-tonne capacity cranes in a tandem lift.
Having securely installed the monopod, eight additional piles were driven through guides on the unit in order to fasten it to the seabed. On completion, the topside - which measured 33 m x 30 m x 27 m - was lifted onto the monopod in a single lift. SAL explained that the topside lift could only be carried out during high tide, with an installation window of around four hours.
The next step involved the lift and installation of the 40-tonne helideck, which had the dimensions 16 m x 15 m x 6 m. Although one of the simpler lifts of the project, SAL explained that the operation still required extensive planning due to the lifting height and centre of gravity (CoG) of the unit.
With all components in position, the first natural gas is scheduled for production from the KLU by the end of 2015.
HeavyLift@Sea was assigned by Deutsche Oel & Gas to handle the project management of planning and installing the new offshore natural gas production platform in Alaska's Cook Inlet.
In addition to the project management HeavyLift@Sea was involved in planning the modification of SAL's vessel Svenja, including living quarters, energy supply and mooring winches.
Detailed hydrodynamic investigations were also carried out to analyse the mooring loads and motion behaviour of the pipe lay barge using advanced CFD methods, as well as a number of other engineering solutions, said HeavyLift@Sea.