Scope of Work
James Fisher Decommissioning were contracted by our valued client Allseas, to support with subsea preparation, pile severance and drill-pin activities on the Gyda jacket decommissioning project in the Norwegian North Sea.
Initial scope of work included:
• Internal cutting equipment for the internal cut of the jacket foundation piles, template foundation piles and locating piles at 1m below mudline
• Dredging/pile cleaning equipment to clean piles internally before inserting the internal cutting tool for subsequent cutting of the piles
• Equipment to drill drain and vent holes in the flooded jacket legs at 200mm OD
• Internal dredging of piles with airlift tool for the subsea template scope.
Scope of Supply
In preparation for the jacket lift, James Fisher Decommissioning scope of supply included:
Subsea drilling to create drain and vent holes to allow the water to drain from the flooded jacket legs during recovery.
Internal dredging of piles with our bespoke airlift tool.
Jacket foundation pile severance utilising our abrasive water jet cutting technology and DCH IV cutting head.
Abrasive water jet cutting with cutting head DCH III for template support pile severance - 3 x 30” piles with 1” WT.
Orange peel grab for internal recovery of debris inside pile.
Diamond wire saw cut on riser connected to the jacket.
Drill, pin and lift of locating piles.
Over and above the original scope of work, additional work scopes were added by the client during the project:
Hydraulic shear and 16te twin grabs for pipeline cut and recovery.
Diamond Wire Saw for severance of multistring conductor.
Topside drill and pinning of platform conductors so they could be recovered prior to jacket lift.
Drill pin and lift tool for 2 pile head inserts
Results and Benefits
There were 20 internal cuts completed on the jacket in total:
8 off 84” OD straight x 100mm WT - average cut time 2 hours per cut
8 of 84” OD angled x 120mm WT - average cut time 2.5 hour per cut
4 off 84” OD x 120mm WT - average cut time 2.5 hours per cut
Subsea template cuts:
2 off 72” OD x 63.5mm WT locating piles - average cut time 2 hours per cut
3 off 30” OD x 25mm WT support piles - average 28 minutes per cut
A very obvious observation when involved with any decommissioning scope of work is the age and condition of subsea structures and the importance of being prepared, yet to expect the unexpected.
James Fisher Decommissioning’s dedicated team, both onshore and offshore have valuable knowledge and experience with engineering and operational delivery of complex work scopes, ensuring we are capable to face any challenges head on.
The scope of work was completed successfully, resulting in the seamless removal of the Gyda jacket by Allseas vessel Pioneering Spirit with jacket lift technology.
“ The James Fisher Decommissioning crew were very knowledgeable with the equipment and the communication between them and the vessel was excellent.”
“The team at James Fisher Decommissioning are very keen and excellent to work with.”
Project Manager, Allseas