Following on from our attendance at the Offshore Energies UK (OEUK) Decommissioning Conference in St Andrews at the end of 2024 and the release of the 2024 Offshore Decommissioning Report, we have taken a closer look at the role of decommissioning. With a forecasted expenditure of £24.6bn by 2033, offshore decommissioning is one of the key enablers of the energy transition and a global priority that everyone should be aware of to ensure the long-term protection of public safety and the environment.
What is Decommissioning?
Decommissioning refers to the process of taking something out of active use, often followed by its safe removal, dismantling, disposal or repurposing. It is typically applied in contexts such as infrastructure, equipment or facilities that have reached the end of their operational life or are no longer needed. While it is often associated with the oil and gas industry (e.g. the dismantling of offshore platforms or pipelines), the concept applies to many other sectors.
Examples of Decommissioning
Before looking at offshore decommissioning more closely, here are some of the other ways it is used around the globe:
Nuclear: Involves shutting down nuclear power plants by dismantling reactors, safely disposing of radioactive materials and restoring the site for other uses.
Renewable Energy: Involves removing wind turbines or solar panels, recycling components and restoring the land to its original state.
Military: Entails safely dismantling and disposing of old or obsolete weapons, bombs and ammunition to ensure they cannot be used again. Also includes the closing and repurposing of military bases.
Maritime and Shipping: Includes shipbreaking where old ships are dismantled, and parts are often recycled or sold. Outdated infrastructure within ports and docks is removed to make way for more modern facilities.
Aviation: Similar to ships, retired aeroplanes are dismantled for parts, with materials recycled where possible. Many old runways and terminals have also been repurposed, particularly into homes, commercial spaces, parks and museums.
Infrastructure: This includes the demolition of bridges and roads that are ageing or deemed to be unsafe and the closing and dismantling of old facilities or plants.
Space Exploration: Involves moving retired satellites to a "graveyard orbit" or safely deorbiting them. Also includes the controlled deorbiting of defunct spacecrafts to prevent space debris.
Energy Sector: Decommissioning outdated coal power plants includes dismantling infrastructure and mitigating environmental damage and removing dams that are no longer viable or have ecological consequences.
Offshore Decommissioning
Key Steps in Offshore Decommissioning
Planning and Regulatory Approvals
-
Feasibility Studies: Assess the condition of the platform, environmental risks, impact and logistical challenges.
-
Stakeholder Engagement: Consult with regulators, governments, local communities and environmental organisations.
-
Regulatory Approvals: Secure permits from relevant authorities to ensure compliance with national and international regulations (e.g., OSPAR Convention, International Maritime Organization (IMO) guidelines).
-
Cost and Schedule Estimates: Develop a detailed decommissioning plan, including budgets and timelines.
Plugging and Abandoning Wells
The main element of the decommissioning process and the costliest of the project. In the UK Continental Shelf alone, OEUK has forecast that a total of 2,074 wells will be decommissioned over the next decade.
-
Wellbore Preparation: All downhole equipment such as tubing, packers and production tools is removed. The wellbore is then flushed and filled with appropriate fluids to stabilise pressure and prevent contamination during the plugging process.
-
Plug Placement: Plugs are installed at key intervals within the wellbore to ensure the isolation of various formations:
-
-
Open Hole and Perforated Intervals: The bottom most section of the well is sealed first.
-
-
-
Casing Stubs and Annular Spaces: Mechanical or cement plugs are set in these sections to provide robust barriers.
-
-
-
Surface Plug: A plug is placed near the surface to prevent fluid migration or surface leaks.
-
Removal of Structures
-
Topsides (Platform Deck): Disassemble topsides modules and transport them to shore for reuse, recycling or disposal.
-
Substructure (Jackets): Cut jacket sections using specialised tools (e.g., diamond wire, shears). Remove jackets entirely or partially, depending on regulatory requirements and environmental considerations. In some cases, structures may be left in situ as they have formed artificial reefs.
Site Clearance
-
Debris Removal: Conduct surveys to ensure the seabed is cleared of debris and obstructions.
-
Environmental Restoration: Restore the site as close to its original state as possible, if required.
Post-Decommissioning Monitoring
-
Environmental Monitoring: Check for any long-term environmental impacts, such as sediment contamination or marine ecosystem changes.
-
Site Surveillance: Monitor abandoned wells and the cleared seabed to ensure compliance with regulations.
Offshore Decommissioning Challenges
From the surge of renewable projects competing for the UK supply chain's resources to the unpredictable political and fiscal environment that has dampened investment, serious challenges face the decommissioning community across the UK Continental Shelf (UKCS). Challenges also include:
Technical Complexity: Aging infrastructure, harsh North Sea conditions and advanced engineering needs for subsea removal.
Environmental Concerns: Minimising ecosystem disruption, managing hazardous waste and addressing carbon emissions from operations.
Economic Challenges: High costs, funding gaps and competition for resources with renewable energy projects.
Regulatory Compliance: Navigating complex laws, ensuring liability management and adapting to policy changes.
Skill and Knowledge Gaps: Shortages in specialised workforce and evolving technological solutions.
Reuse and Recycling: Limited opportunities for repurposing infrastructure and challenges in material recycling.
Stakeholder Coordination: Balancing interests among operators, regulators and communities while maintaining public trust.
Despite these challenges, they can be overcome. Decommissioning is becoming increasingly vital as a key step toward building a sustainable and innovative future. It goes beyond dismantling, it’s about transitioning to improved systems, promoting growth and advancing sustainability. This approach represents a shift in perspective: from responsibly addressing the past to actively shaping the future.
Is the National Subsea Centre Currently Involved in Any Decommissioning Projects?
As part of the SeaSense project, the NSC’s Transparent Ocean team is revolutionising subsea exploration with innovative haptic technology. Using this technology the team can extract precise information from geometric measurements and physical attributes to make subsea operations safer and more efficient, spanning inspection, maintenance and decommissioning. Discover more about the project here.
The NSC was recently awarded a decommissioning AI-demonstrator grant in partnership with PlanSea to develop a subsea decommissioning optimisation software demonstrator which will allow decision-makers to simulate with a high degree of accuracy the cause-effect relationship between different strategies and KPIs of interest. Discover more about the grant here.
To discover more about how the National Subsea Centre team is solving real-world problems, view our dedicated Projects page.
