ROTTERDAM, the Netherlands — The 20,300-t Curlew FPSO has been delivered to the decommissioning and recycling facility in Vats, Norway, for dismantling.
The work was carried out by AF Offshore Decom in its entirety, including the float-on and load-in. Mammoet was a subcontractor delivering axles for the load-in by SPMT.
The program involved the use of 748 SPMT (special purpose mobile trailer) axle lines and 30 power packs.
Shell commissioned the 235-m long, 20,300-t Curlew FPSO, with the vessel producing gas for over 20 years.
AF Offshore Decom is the main contractor for the decommissioning project, with Mammoet appointed for the load-in and set-down operation.
Dorien Frequin, branch manager Norway for Mammoet, said the load-in to the decommissioning yard presented major challenges – not just the size and scale but also the nature of the structure which meant that it would deflect when moved around, potentially jeopardizing the transport operation.
The company started its involvement with AF Offshore Decom and COSCO SHIPPING Heavy Transport years before the actual project execution, with detailed planning for the engineering scope and operational challenges.
Ludo Mous, director Operations at Mammoet Europe, said: “Safety was our first priority and we identified that having a single professional operating all SPMTs would be the best method to use. This meant that risks from miscommunication between operators were removed but required a high level of expertise to ensure all electronics worked together and maintained accuracy –especially as performance of the SPMTs would need to be adapted during the move.
“We also had to adapt the SPMT technology to work in this way – it is a world first…Alongside the operator there were 13 other Mammoet professionals placed at specific points around the vessel to monitor progress and communicate with the operator when needed.”
Testing had to be performed prior to executing the move. This was done first onshore where the crew tested the full trailer arrangement, and then again onboard with the Curlew FPSO in situ.
Pre-engineered fillings were placed between the SPMTs and the FPSO to correct the deflection of the hull so that the trailers were at the same level to optimize their required stroke. This allowed Mammoet to make adjustments to keep the structure stable and in the correct shape, as well as accommodating the anticipated deflection of the hull.
The planning, engineering work and testing were successful, with the FPSO moved on schedule into position for AF Offshore Decom to start the dismantling process.