Proserv leased First Subsea’s Ballgrab gripping technology for a decommissioning project in Norwegian waters for the recovery of a caisson. The tool had to descend down within a foundation caisson of 30in to 20in to 13-3/8in to access the inner 9-7/8in API 5CT Q125 section.
At 30in-diameter, the foundation caisson protruded 8m vertically above the seabed in about 90m water depth and contained three inner caissons of reducing diameters.
Recovering the inner caisson required a simplified rigging methodology to overcome the shackle geometry constraints which prevented access to the inner 9-7/8in caisson. The shackle could only accommodate the 20in casing section and a 2.5m modular extension was added to the tool extending its reach to access the inner 9-7/8in (ID 8.625in) caisson.
The Ballgrab tool was lowered into the caisson and then remotely activated topside through a 120m twin Siamese hose on a reeler complete with HPU (hydraulic power unit).
“Ballgrab gripping technology is ideal for this kind of application where caisson and pipes have to be removed from often inaccessible locations,” says John Shaw, Managing Director, First Subsea.
The tool is part of the company’s rental fleet that covers over 300 stock tools for lifting / handling and recovery of API line pipes, deployment and handling of manifolds, monopiles, suction piles and flexible risers for both oil and gas and renewables sectors.