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UK Decommissioning Process

What is Decommissioning?

Decommissioning involves taking offshore oil and gas infrastructure out of service, securing the wells, dismantling the structures and either reusing, recycling or disposing of in accordance with legislation.

What is the decommissioning approval process?

The Department for Business, Energy and Industrial Strategy (BEIS) regulates decommissioning of offshore oil and gas installations in the UK sector of the North Sea, using a clearly defined process stipulated by the Petroleum Act (1998). Operators must submit a Decommissioning Programme to BEIS for review, followed by a public consultation period. The UK’s international obligations on decommissioning are governed principally by the 1992 Convention for the Protection of the Marine Environment of the North East Atlantic (OSPAR Convention).

What is a Decommissioning Programme?

A decommissioning programme sets out the measures to decommission installations and/or pipelines and wells. The scope is developed based on extensive and wide-reaching studies and assessments that are used to evaluate the appropriate options for dealing with the oil and gas infrastructure.

What is Derogation?

Derogation is an exemption from the OSPAR criteria to allow installation footings to be left in place. To determine if derogation is appropriate, a process of comparative assessment and comprehensive stakeholder engagement is conducted. Validated assessment techniques that capture safety, environmental, socio-economic, technical and economic factors are used to develop a balanced and appropriate decommissioning solution.

What is a Comparative Assessment?

A Comparative Assessment is used to evaluate one or more options against five principal criteria (safety, environment, technical, socio-economic and financial). A key element of Comparative Assessment is engagement with key stakeholders and subject matter experts, essential to formulate a robust comparison between options and ultimately a recommendation.

Which elements are determined by regulation?

All elements of a decommissioning project are governed by regulation, both in the planning (OSPAR, BEIS and OGA) and the safety of the activities themselves (HSE).

What are the challenges with Decommissioning?

In most cases, when offshore facilities were constructed decades ago, the technical method for removal of the facilities was outweighed by the simplification of the design and installation methods. This makes the removal of the assets much more onerous and technically challenging than the installation. However, innovative thinking and technology are leading to novel solutions to overcome the majority of these challenges.

Brae Area Asset Decommissioning

Why are you decommissioning the Brae Area Assets?

Decommissioning is a natural step in the life cycle of an oil and gas field once the source of hydrocarbon has been depleted and production is no longer economical. Marathon Oil has already extended the life of the Brae field beyond the initial projections and, after careful consideration, the only viable option is to decommission the facilities. Marathon Oil initiated planning for the decommissioning of the Brae field infrastructure in 2009.

What are your recommendations for the DPS?

The Decommissioning Programmes are available on this website and provide a summary of the recommendations for the Brae Area.

Did you consider alternatives to decommissioning?

The decision to cease production was made after other hydrocarbon producing opportunities were considered unviable. Alternatives for reuse of the facilities in-situ have been considered, but, given the age of the infrastructure and location in the North Sea, there were no economically viable options.

Is there a timescale for the decommissioning?

The scope of the Brae Area decommissioning is considerable, including three fixed steel jacket platforms, three Marathon Oil operated subsea tie-backs and numerous pipelines and subsea components. Before decommissioning work can proceed, the Decommissioning Programmes must be approved by the regulatory bodies, and stakeholders must be given an opportunity to comment. It is estimated that the entire decommissioning process could take up to 20 years to complete.

Are your Brae platforms still operational?

Yes. The Brae Area assets are all important elements of Marathon Oil’s production portfolio and continue to be utilised at optimum levels. Investment in these platforms continues to be made, both in line with Marathon Oil’s commitment to the highest standards of safety and also with a view to continue to extend the life of the field where possible as new technology and methods are developed.

Is decommissioning being led from the US or UK?

Based in Aberdeen, a specialist team, led by the Decommissioning Project Manager, is leading the Brae Area decommissioning. Their knowledge and expertise of the North Sea is vital to the success of the operation, with valuable support being provided by professionals in the US and worldwide.

Will this mark the end of your North Sea interest?

The Brae Area is Marathon Oil’s only remaining Company-operated asset in the North Sea, but the Company also holds non-operated working interests in the Foinaven area, west of the Shetland Islands and in the Scottish Area Gas Evacuation (SAGE) terminal at St. Fergus and associated North Sea gas gathering pipeline

What is the cost and who will be funding?

An accurate cost estimate cannot be quantified until decommissioning plans are finalised and the proposed Decommissioning Programmes are approved. Marathon Oil and its Partners are responsible for all costs associated with the decommissioning. UK Government tax relief is available for operators actively engaged in decommissioning.

What will be the economic impact to the UK?

The Brae Fields have been in production for the last 35 years and have now reached the end of their technical producing lives. During that time, the Brae Field infrastructure has created thousands of jobs, and Marathon Oil has contributed more than £1.3 billion in Corporation Tax, Supplementary Charge and Petroleum Revenue Tax

How many wells will you have to P&A?

There are approximately 100 wells to plug and abandon (P&A).

How will you seal the wells?

The wells will be plugged and abandoned in accordance with the offshore industry standard, Oil and Gas UK Guidelines for the Suspension and Abandonment of Wells.

What percent of the structure(s) will be recycled?

It is provisionally estimated that at least 85 percent will be recycled, 10 percent reused and less than 5 percent disposed of.


Are jobs at risk due to the decommissioning?

The scale and complexity of any Decommissioning Programme requires additional resources to be deployed, both offshore during removal and onshore during dismantling and disposal. Marathon Oil expects that specialist skills within the decommissioning sphere will be needed in both the short and long term. This will present opportunities for both existing employees and others with expertise in the sector. Inevitably, after decommissioning is completed, there will be a reduction in the Company’s North Sea workforce.

Which contractors are involved in the programmes?

Marathon Oil will be engaging extensively with the supply chain to select those contactors who share our safety values and can offer effective and cost efficient solutions.

Stakeholder Engagement

Can stakeholders have input in the process?

Yes, Marathon Oil is committed to working with stakeholders to deliver Decommissioning Programmes that take into account the views of groups and individuals with an interest in the North Sea and associated industries. Details of the consultation process are available online, with direct contact also made with many stakeholders to ensure comprehensive input. 

How have you engaged with external stakeholders?

Multiple face-to-face and workshop-based engagements have been made with stakeholders. In addition, this website was launched in 2015 and provides key information on the Brae Area and the Decommissioning Programmes. The website will continue to be updated to include pertinent developments. Marathon Oil is also committed to communicating to a wider audience during the process – through digital and traditional media – to ensure all those with an interest in the proposed Decommissioning Programmes have access to the latest information. Marathon Oil is committed to clear and open communication throughout the process.

How have you engaged with internal stakeholders?

Internal stakeholders have been provided regular updates on the decommissioning progress through weekly status reports, presentations and informational documents.


How did you assess potential safety impacts?

Marathon Oil considers safety to be the most important factor in any works that it undertakes. All decisions related to the selection of decommissioning options have included a review on the safety impacts. Details about the Decommissioning Programmes’ safety impacts are available on this website.

Environmental Considerations

What are the environmental impacts?

Marathon Oil regards environmental stewardship as a key element of corporate responsibility and has conducted studies and assessments beyond the minimum required by regulation to better understand the short-, medium- and long-term environmental impacts of the decommissioning proposals being put forward. The conclusions reinforce the proposals that Marathon Oil have put forward to the decommissioning plans. Full details are available within the Decommissioning Programmes and associated Environmental Statements which are available on this website.