Pioneering Spirit repeats fast lift with 25,000-tonne Brent Bravo platform
With another nine-second fast lift, Allseas’ heavy lift and pipelay vessel Pioneering Spirit has removed the 25,000-tonne Brent Bravo topsides from the North Sea. The move took place last week at the Brent oil and gas field located 186 kilometres off the northeast coast of the Shetland Islands.
The full removal of the Brent Bravo platform took four hours to complete, from positioning the vessel around the platform to the moment of the lift. Yet, as with the removal of the much smaller Valhall platform (3800 tonnes), which the Pioneering Spirit removed from the Norwegian North Sea a week before the Brent Bravo, the actual “fast lift” of the topsides took only nine seconds.
The Brent Bravo platform comprised a topsides structure supported by three 12-metre diameter steel-reinforced concrete legs, which stand in 140 metres of water. Cuts between the topsides and supporting legs were made during the final months of platform preparations. Until the lift, the structure was held in place by purpose-built shear restraints that prevented lateral movement. The concrete legs remain in situ, capped with concrete covers fitted by one of the vessel’s cranes. A solar-powered navigational aid has also been installed on top of one of the capped legs.
Transported to England
The 125 metres tall, 70 metres wide topsides were sea-fastened on board the Pioneering Spirit and subsequently transported to the Able UK decommissioning yard in Teesside, North East England. At a nearshore location off the coast of Hartlepool, the topsides were transferred to Allseas’ cargo barge Iron Lady for the final leg of its journey: towage up the Seaton Channel and load-in to the quay at Able UK’s yard for dismantling.
Brent Bravo is the second of four platforms, after Brent Delta in 2017, to be decommissioned and removed from the Brent oil and gas field. On both occasions, Shell U.K. Limited has utilised Pioneering Spirit’s single lift, motion-compensated technology. The lift concluded two years of intense planning and offshore engineering works.
Since becoming operational in 2016, the Pioneering Spirit has lifted more than 130,000 tonnes of topsides weight and installed over 1500 kilometres of subsea pipeline. The single-lift removal of the 24,200-tonne Brent Delta topsides in April 2017 set a new record for a lift undertaken at sea, until Pioneering Spirit’s installation of the 26,000-tonne production platform for the Johan Sverdrup development offshore Norway, earlier this year.