Photos: Pioneering Spirit Hoists 11,000 Tonne Jacket in a Single Lift
Allseas' massive heavy-lift ship Pioneering Spirit has removed an 11,000-tonne platform jacket from Repsol's Gyda field, one of the heaviest jacket-lift jobs ever completed in one piece.
Pioneering Spirit, the world's largest vessel by displacement, was purpose-built for two specialized tasks - laying pipe and removing/installing platform topsides. She has a unique fast-lift hydraulic system on two forward pontoons, which she uses to rapidly lift and remove an entire topside module in a single evolution (up to 48,000 tonnes).
Until recently, however, she could not lift jackets. To solve that problem, Allseas commissioned two giant lifting beams to mount on Pioneering Spirit's stern, turning her into a 20,000-tonne floating sheerlegs when needed. Uniquely, the legs are hinged and equipped with a jacking system that lowers them back onto deck for transit. This will allow the vessel to pick up a jacket and lay it flat (or at an angle) before heading back to port. The beams give a new purpose to her expansive stern, which was previously set up for mega-scale pipelay operations.
At Gyda, Allseas' scope of work included removing both the 18,000 tonne platform and the 11,000 tonne jacket. In advance of the job, the team fabricated special bearing brackets and lift trunnions to take the load of the platform. Over the span of 12 days in May, Pioneering Spirit loaded out the platform and related equipment, then delivered it to the quay at Aker Solutions’ scrapyard in Stord, Norway.
To prepare for removal of the jacket, the structure’s 24 foundation piles were cut below seabed level. Hoist blocks connected to the lifting beams were hooked up to pre-installed rigging and the entire structure was pulled up and prepared for transport. The jacket could not sustain the load if laid down flat, so Pioneering Spirit carried it back into port in a near-vertical position. On Tuesday morning, the jacket was set down directly onto the quayside next to the topside module.
All images courtesy Allseas
Over the course of the year to date, Pioneering Spirit has lifted and transported more than 90,000 tonnes of decommissioned and new offshore facilities, including both jackets and topsides. Later this year, it will take on a job in the offshore wind sector, installing a jacket and a transmission platform for a wind farm in the German North Sea.