OST-6-1 (Gennaker)

Scope of work

• Project management, engineering and preparation for transport, offshore transfer and installation operations
• Transport of the Gennaker west (Darß) and east (Zingst) suction jackets and offshore substations (OSS) on separate asset barges
• Installation of both suction bucket jackets and OSS with the jacket lift system (JLS) 
• Post-installation survey, structural completion and associated specialist suction-bucket, grouting and marine activities

Project specials

• First installation of topsides using the JLS
• First commercial Allseas installation of jackets founded on suction buckets
• Rostock selected as a Baltic buffer port to separate North Sea transport from installation sequence
• Buffer-port preparation and staged call-off of the four assets to installation sites
• Offshore transfers from the asset barges to Pioneering Spirit using spacer barges and tugs
• BIAS dynamic-positioning mode to mitigate scour risk at shallow water installation sites

Project challenges

• Shallow-water installation with Pioneering Spirit at 13.5 m draught (minimal under-keel clearance prevented use of topsides lift system)
• Complex offshore transfers in an exposed offshore environment, requiring coordinated positioning of asset barges, unmanned spacer barges, tugs and support vessels
• Tightly constrained transfer and installation areas influenced by existing and future turbines, the Baltic Cable, a Natura 2000 area and prepared seabed excavations
• Scour and sedimentation risk from Pioneering Spirit’s thrusters, requiring controlled vessel orientation, low-thrust movements and BIAS DP operation
• Boulders and silt at Gennaker East with potential to obstruct / limit suction-bucket penetration
• Autumn Baltic Sea weather conditions 

Photo credits: Tom Schünemann & DanPilot/Chris Hansen