SABRE subsea abrasive jet cutting system used to abandon Camelot

The Claxton SABRE™ abrasive cutting system is capable of simultaneously severing all the casings in a well, regardless of casing loading, eccentricity or contents.

The Problem

There are serious doubts about whether King Arthur’s Camelot ever really existed. In contrast, the UK North Sea gas fields and production platform of the same legendary name certainly did, though the evidence is disappearing rapidly.

The complete decommissioning of the North Sea Camelot fields and the removal of Camelot Alpha platform began in earnest at the start of 2012 with the plugging and abandonment of the fields’ six platform wells. This was followed by the severance of the well casings some 5 m below the seabed, a task for which Claxton was ideally qualified, as the company’s project manager Bob Leggett explains.

We have established an enviable record in the North Sea for this kind of work using our SABRE™ internal abrasive cutting system, which enables us to sever all the casings within a well simultaneously, regardless of the loading on the casings or any eccentricity.

The system uses a mixture of air, water and abrasive garnet at up to 1000 bar to cut through the multiple steel casings and any cement within the various annuli. We generally then drill and pin the casings so they can be safely withdrawn in a single operation.

The Solution

“Part of the process is to prove that we have achieved complete severance within the well; for this, we use a Claxton-designed jacking system to temporarily raise the combined casings and then ease them back down for complete removal later.

This was the process Claxton followed with the Camelot wells, which contained casings ranging in diameter from 9in. to 30 in., during May and June 2012. The cutting process presented few challenges. In fact, the biggest headache for the team was working out how to accommodate the various components of the SABRE™ system in the limited deck space available on the small, normally unmanned Camelot platform. Support beams were used to spread the load of the high-pressure pumps, air compressor, supply tank, mixing system and umbilical required to run the SABRE™ system.

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