Ballgrab device assists caisson recovery offshore Norway

Proserv has leased First Subsea’s Ballgrab gripping technology for a decommissioning project offshore Norway for recovery of a caisson.

May 17th, 2016
First Subsea tool recovers difficult to reach caisson.
First Subsea tool recovers difficult to reach caisson.

Offshore staff

ABERDEEN, UKProserv has leased First Subsea’s Ballgrab gripping technology for a decommissioning project offshore Norway for recovery of a caisson.

For this application the tool needed to descend down within a foundation caisson of 30-in. to 20-in. to 13⅜-in. in order to access the inner 9⅞-in. API 5CT Q125 section.

At 30-in. diameter the foundation caisson protruded 8 m (26 ft) vertically above the seabed in a water depth of around 90 m (295 ft) and contained three inner caissons of reducing diameters.

Recovering the inner caisson required a simplified rigging methodology to overcome the shackle geometry constraints that prevented access to the inner 9⅞-in. caisson. The shackle could only accommodate the 20-in. casing section, so a 2.5-m (8.2-ft) modular extension was added to the tool extending its reach to access the inner 9⅞-in. (8.625-in. ID) caisson.

The Ballgrab tool was lowered into the caisson and then remotely activated topsides through a 120-m (393-ft) twin Siamese hose on a reeler, equipped with a hydraulic power unit.

05/17/2016

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