During a decommissioning project, all topsides must be removed. There are three principal methods for achieving this:
• Single-lift – Using a large lift vessel to remove the topsides as a single unit and transport onshore
• Reverse installation – Separation of modules on the installation and removed by the lift vessel one by one
• Piece-small removal – Breaking the topsides into small pieces offshore and transporting the waste to shore for disposal
Operators will assess the suitability of each method to individual installations and confirm a methodology for removal. Once the methodology for removal is confirmed the topsides can be prepared for lifting. Specialist structural engineers and lift experts are required for this phase of the work scope. Their activities may entail lift-point installation or re-instatement and structural strengthening for transportation.