Expert advice on decommissioning

Jon Lawson

Assessing the options for oil platform decommissioning offers value, says Lara Alvarez

Energetic discussion continues over the fate of oil and gas installations facing decommissioning. As we consider environmental responsibility alongside the existing decommissioning drivers under the OSPAR Convention, is there value in retaining some elements of offshore infrastructure?

On one hand, EU nations have, for the most part, endorsed the total removal of offshore installations. Yet new evidence suggests removal can be detrimental to the environment where marine ecosystems have colonised infrastructure over many years. 

North Sea oil platforms present a monumental decommissioning challenge. By 2027, we should see the removal of almost a million tonnes of oil and gas installations, pipelines and underwater assets. The associated financial impact is huge, with the Oil & Gas Authority and HMRC estimating costs of £61bn for operators and £24bn for taxpayers. In addition, a balance must be struck between a variety of different factors including costs, engineer safety, disturbing marine life, reducing biological connectivity between platforms, the carbon footprint and the technical feasibility of removal. 

To enhance understanding of the implications for the North Sea ecosystem associated with removal of these man-made structures, research programmes, such as INSITE, are underway. Initial findings indicate that removing structures from the marine habitats has negative implications. 

These installations have been in place in the North Sea for over 30 years and harbour a bounty of established ecological communities including protected cold-water coral species attached to the structures, as well as mobile organisms, such as crustaceans and fish, that use the different ecological niches provided by these structurally complex habitats for feeding or reproduction. In addition to increasing seafloor diversity, these structures provide a safe zone for spawning and nurseries, thus boosting species populations. 

What’s more, offshore platforms can potentially aid the conservation and restoration of the underwater ecosystems and reduce overfishing through their exclusion zones, which close the area to fishing and other activities. The loss of access and displaced fishing effort can be (at least partially) offset by the higher rate of fish production when this leads to overspill effects outside of the no-catch zone. Evidence also suggests that some installations are biologically connected, constituting a network of artificial reefs, in which the overall value of the habitat and associated productivity of the ‘reef’ network is greater than that of each individual structure. 

The UK government currently enforces a clean seabed policy in line with OSPAR Decision 98/3, which requires the total removal of installations and the seabed returned to its ‘natural state’ upon decommissioning. This policy assumes man-made structures have lower ecological value than the original seafloor habitat. However, the emerging evidence on positive environmental benefits of installations coupled with concerns over the intensification of decommissioning efforts are sparking much-needed debate on decommissioning methods across the UK Continental Shelf – presenting a unique opportunity to carefully examine the impact of large-scale decommissioning on the long-term sustainability of the UK’s marine wildlife and ecosystems. 

A flexible legislative approach to decommissioning could allow for bespoke solutions that take into account the variety and complexity in design of individual oil and gas platforms and factor in the true impact of removing each platform on the environment. Furthermore, alignment with existing investment decision approaches pioneered by the UK government will increase credibility of strategy and approach. Removal options should be assessed by using credible and robust scientific approaches, such as resource or habitat equivalency analysis, the Green Book Value-for-Money framework, and net environmental benefit analysis (NEBA) underpinned by ecosystem services frameworks. Most important is identifying and assessing the costs and benefits (as well as the wider impacts) of the various decommissioning options. This will allow the net environmental and socioeconomic impacts to be carefully assessed, alongside the relevant technical, cost and safety criteria, and will allow for a balanced decision to be made for an individual platform as part of a collection of biologically-connected offshore installations. 

This approach would not grant a license to pollute, on the contrary, a well-designed decommissioning strategy would reduce any unintentional impact on the environment. This is particularly relevant given the various factors currently affecting marine ecosystems, such as a population decrease of fish on the seabed, loss of habitat and other ecosystem elements under conventional fishery management and climate-induced changes to the movement and composition of the ocean. 

Setting a precedent for a range of newer offshore infrastructures, such as wind turbines which will require decommissioning in the coming decades, the UK government’s decision on the North Sea oil platforms has huge implications and must be carefully considered. As environmental responsibility becomes a key concern, the need for bespoke decommissioning solutions that acknowledge all the trade-offs is key, discrediting the total removal of offshore installation as an inflexible and unsustainable policy.  

Lara Alvarez is Managing Consultant at Ramboll