Allseas’ heavy lift vessel Pioneering Spirit has completed its first decommissioning job of this summer, the single-lift removal of Shell UK’s Brent Alpha platform from the North Sea. Removing the 17,000-tonne topsides took less than four hours. It was the first offshore lift to utilise specially developed “horseshoes”.

Several years of planning and fifteen months of offshore preparation, including strengthening and cutting the steel jacket’s six legs, culminated in the nine-second “fast lift” of the 17,000-tonne topsides in the evening of 21 June 2020. The Pioneering Spirit will now deliver the 44-year old structure to Able UK Limited’s Teesside decommissioning yard in North East England for dismantling and recycling.

Brent Alpha is the third of four platforms, after Delta (2017) and Bravo (2019), to be decommissioned and removed from the Brent oil and gas field. For all four jobs, Shell UK Limited selected the Pioneering Spirit. Production from the field continues through Brent Charlie, with Pioneering Spirit booked to remove the 34,000-tonne topsides when the platform finally ceases production.

Located 186 kilometres off the northeast coast of the Shetland Islands, Brent Alpha comprised a topsides structure supported by a steel six-legged jacket standing in 140 metres of water. Like Delta and Bravo, the Alpha topsides features multiple decks with living quarters, power generation, process systems, drilling derrick, flare stack and other platform facilities.

Horseshoes

The removal of Brent Alpha is the first offshore lift to utilise specially developed “horseshoes”. These are connection tools that clamp around pre-installed lift points called bearing brackets mounted on the upper sections of the steel jacket’s legs (see pictures of the horseshoes below).

The Brent Alpha topsides removal project involves engineering, preparation, removal and disposal of the 94 metres tall, 52 metres wide structure. As with the two previous Brent jobs, Pioneering Spirit will transport the Alpha topsides to a nearshore location off the Hartlepool coastline, where it will be transferred to Allseas’ cargo barge Iron Lady for the final leg of its journey by towage up the Seaton Channel and load-in to the quay at Able UK.

This summer, the Pioneering Spirit will remove and transport more than 55,000 tonnes of decommissioned platform infrastructure from UK and Danish fields to disposal/recycling yards around the North Sea.