KNOWLEDGE HUB
The Decommissioning Work Breakdown Structure
The Industry Standard Framework for Cost Classification and Benchmarking
The Offshore Energies UK (OEUK) decommissioning Work Breakdown Structure (WBS) serves as the primary framework for planning, reporting, and benchmarking decommissioning projects. It provides a standard structure used by operators and the supply chain globally to ensure commonality across the various elements of a decommissioning project.
The 11 Phases of Decommissioning
The WBS defines the decommissioning lifecycle through 11 distinct phases, which are typically used to report costs and manage schedules:
1. Project Management
This phase can begin up to 10 years before the cessation of production (COP) and involves the core team responsible for studies, decommissioning programmes and engineering.
2. Post-COP Running Costs
These are the operational costs for the offshore asset incurred between the end of production and the start of primary decommissioning execution.
3. Well Decommissioning
Historically accounting for approximately 50% of total decommissioning expenditure, this element covers the permanent well plug and abandonment (P&A), which provides a permanent isolation between the oil and gas reservoir and the surface.
4. Facilities and Pipelines Permanent Isolation and Cleaning
5. Topside Preparation
This phase prepares the topside structure for removal, including the installation of rigging points and the removal of obstructing infrastructure.
6. Topsides Removal
The physical recovery of the topside structure using either single-lift heavy vessels or smaller construction vessels for piece-small removal. Learn more about topside removal.
7. Substructure Removal
This involves the recovery of the jacket or the subsea part of the offshore processing facility that connects the topsides to the seabed. Read more about substructure removal.
8. Topsides and Substructure Onshore Disposal
Once recovered, structures are transported to onshore facilities for dismantling, recycling and waste processing.
9. Subsea Infrastructure Removal
This covers the removal of manifolds, pipelines, cables and other seabed infrastructure. Learn more about subsea infrastructure removal and site remediation.
10. Site Remediation
The final clean-up of the seabed to ensure it is clear of debris and returned to an acceptable condition.
11. Post-Decommissioning Monitoring
The ongoing monitoring cycles for any infrastructure left in situ, such as buried pipelines or abandoned wells, this monitoring activity will be agreed with the regulator.
Strategic Benchmarking and Cost Management
The WBS is an essential tool for cost estimation and performance improvement. Each year, OEUK releases a report providing a cost breakdown based on these 11 elements, allowing operators to benchmark their performance against industry averages.
For example:
- Well decommissioning represents approximately 50% of the total budget.
- Topside preparation and removal generally account for 10% to 12%.
- Subsea infrastructure removal typically ranges between 12% and 15%.
This structured visibility enables operators to identify cost drivers, challenge inefficiencies and improve future campaign planning.
Not a Project Delivery model
It is important to note that the work breakdown structure is not a project delivery model, meaning that OEUK WBS is how the costs are allocated and documented.
While the WBS provides clearly defined cost categories for reporting, the industrial reality is that many activities overlap across these cost groupings.
In one of the Lean Decom training course modules, you will gain a detailed understanding of the contractor’s perspective and how effective use of the WBS supports alignment between operators and the supply chain. For example, Engineering Down and Clean (WBS 4) often requires activities funded through other cost categories, such as temporary utilities in WBS 2 or well bay clearance in WBS 3.
Understanding these interfaces is critical for ensuring commercial clarity, avoiding scope ambiguity and aligning execution strategy with the operator’s cost model.
Through the Lean Decom training course, you will gain a comprehensive overview delivered by Ricky Thomson, Head of Decommissioning at OEUK, on how this framework is used to drive sector-wide performance.
Decommissioning Training
Learn more about how the OEUK WBS framework is applied in practice through the Lean Decom training course.