Decommissioning Insight 2018
DECOMMISSIONING INSIGHT 2018
8.5 Topsides Preparation Once all sources of energy have been isolated, the topsides canbe prepared for removal. The 'topsides' refer to the facilities which sit on top of an installation, typically including drilling, processing and living quarters. Preparatory activities include the separation of process equipment from the wells and pipelines as well as module separation. Any activities to upgrade the facilities are also included in this part of the scope. This may include power upgrades to the installation to meet the decommissioning requirements. If a structure is to be left in place for any period of time, navigational aids may be installed during this phase.
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Topsides preparations accounts for £480 million (3.1 per cent) of the forecast decommissioning expenditure over the next ten years.
8.6 Topsides Removal
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.
The forecast expenditure for topsides removal is £1 billion, around 6.6 per cent of overall expenditure.
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