As decommissioning gathers pace around the world, Gary McKenzie, Marine Projects Manager with Seacroft Marine Consultants, recently completed a task as marine representative for a senior international operating company overseeing the safe removal and reactivation of an FPSO off West Africa.

The project – following safe disconnection of the production risers – was to disconnect the FPSO from the 16 anchor chains holding her on station, and then to tow her clear of the field location.

Gary McKenzie worked with the client’s management team, contributing to major risk assessment sessions during the project plan’s development and assurance processes. On board the FPSO, Gary’s role was to represent the client, liaising between the Master/Offshore Installation Manager, project management and third-party tugs.

“Seacroft Marine Consultants has significant experience both of FPSO hook-up/tie-in and of removal – but every project presents different challenges,” says Gary McKenzie. “For example, unlike most FPSO’s which are turret-moored and weathervane, this vessel was anchored on a fixed heading. Also the project provided for the FPSO – a converted Suezmax tanker – to be reactivated as a vessel capable of making way under her own power initially to a nearby port and then onward to an international port for refit.”

The 16 anchor chains – 4 at each quarter of the vessel – were secured under tension in ‘stoppers’ before being cut. Oxy-acetylene burners on long lances were to be used, with the operators being further protected behind structural steelwork.

Vessel assurance was completed on the five tugs before these first four tugs took up position at the four quarters of the FPSO to hold her on station during the disconnection operation.

One by one, the chains were disconnected as planned, at which point the tugs towed the FPSO clear of the exclusion zone where it was anchored to allow divers to clean the propeller, rudder and sea chests before the unit sailed away under her own power.

“The project plan was meticulous and the assurance tight, which went a long way toward ensuring no surprises during implementation. The contractors, tow-master and vessels communicated effectively throughout and the result was an on-time completion with zero incidents to report. A great result for the team as a whole, and one which adds to the experience-base Seacroft can bring to bear on other FPSO removal projects around the world” says Gary McKenzie.