Benefits of offshore infrastructure for marine ecosystems

Lara Alvarez, Managing Consultant, and Samantha Deacon, Senior Managing Consultant

The marine environment is facing intensifying pressures from climate change, waste and resource management, and habitat destruction. And the debate on the drivers of the OSPAR Convention is being reignited for the protection of the North Sea. So – is it time to take a more holistic approach and assess the sustainability of offshore infrastructure decommissioning? Governments should evaluate the range of options that address environmental responsibility, deliver best value for money, and consider how other countries, such as Malaysia, the US and Mexico successfully use decommissioned platforms for enhancing fish stocks.

Measuring the costs

The UK is one of the largest and fastest growing markets by value in offshore decommissioning, with almost one million tonnes of oil and gas installations, pipelines and underwater assets to be removed within the next seven years. As it currently stands, EU nations are implementing a policy of complete removal of all structural elements of offshore oil and gas platforms. However, scientific evidence suggests that the total removal of such structures can in fact have negative consequences to valuable marine ecosystems.

Not only does it pose a huge technical challenge, but the financial upshots of these plans are equally astounding, with the Oil & Gas Authority and HM Revenue and Customs approximating costs of £61 billion for operations. As for taxpayers, an additional sum of £24 billion has been estimated, owing to high tax-deductible expenditures.

In addition to costs and technical barriers, the physical scale of the decommissioning process demands trade-offs between a range of other factors, including engineer safety, disturbing or removing habitats and the marine life they support, reducing biological connectivity between platforms, re-opening areas for bottom fishing, mobilising buried contamination, and the carbon footprint of air emissions associated with the removal of piled structures.

Scientific research

Such a vast array of considerations has meant that the number of scientific publications aimed at improving the understanding of the impact of removing these man-made structures in the North Sea has grown at pace, supported by research programmes such as INSITE.

Initial results are in line with the findings from more extensive research conducted in other seas such as the Gulf of Mexico and there now seems to be a wider understanding that failure to consider the negative impacts associated with offshore decommissioning in the North Sea could have extremely damaging effects on marine ecosystems. Many of these North Sea installations have been in place for over 30 years and have established communities, including protected cold-water coral species attached to structures and mobile organisms such as crustaceans and fish that utilise the different ecological niches provided by these structurally complex habitats for feeding or reproduction. The increase in seafloor heterogeneity and the provision of a safe zone, which attracts fish and supports the recruitment and growth of larvae and pelagic juveniles, ultimately enhances fisheries.

Underwater structures as Marine Protected Areas

Scientific literature shows that owing to their exclusion zones that bar fishing and other activities from around platforms, their age and isolated locations mean platforms have the same attributes as Marine Protected Areas. Exclusion zones serve to support the conservation of the benthos and reduce fish over-exploitation.

The loss of access and displaced fishing effort for fishermen can be partially compensated by the increased fish production rate when overspill effects occur outside of the exclusion zones, reducing the catch per unit effort associated with the harvest of commercial fish species. Some governments and researchers are therefore promoting the use of exclusion zones as a tool to assist the management of marine resources, together with ‘total allowable catches’ or fishing closures.

The Malaysia Ministry of Fisheries even has a policy of relocating platforms to established fishing grounds for the conservation of fish stocks and reduce over-exploitation. Evidence also indicates that some installations constitute a network of artificial reefs, and are biologically connected, placing the aggregate habitat value and associated productivity of the network higher than that of its individual components.

The wrong assumptions of current policy

Despite this evidence, the UK government and its North Sea neighbours continue to enforce a clean seabed policy in OSPAR Decision 98/3, which prohibits leaving the installation partially or entirely on the seabed and demands a return to its “natural state” upon decommissioning. This policy fails to acknowledge that soft-sediment ecosystems altered by human activity may have evolved over time into an artificial reef habitat and, as a result, full removal of the platform would result in the loss of this enhanced ecosystem – forever.

The policy wrongly assumes that all man-made structures have lower ecological value than the pre-installation seafloor habitat, and lacks flexibility in decommissioning strategies that appear contrary to the precautionary principle. Derogation from full removal is solely based on technical criteria and, as such, may not be granted.

Much-needed debate

The increasing scientific evidence on the unintended consequences of offshore decommissioning, coupled with the growing intensity of decommissioning efforts and large investment programmes, should position the UK as the global leader in sustainable decommissioning.

R&D focused on transforming the conventional approach to decommissioning, plus cost reduction for taxpayers and the oil and gas industry, should trigger much-needed debate on decommissioning approaches across the North Sea. There is an opportunity to examine of the impact of large-scale decommissioning on the long-term sustainability of marine ecosystems.

Tailored solutions avoid unintended consequences

If we are to truly protect the environment, the complexity and variety in designs, installations and operations of individual oil and gas structures must be reflected in a flexible policy that allows for tailored solutions for each platform and seeks a wider understanding of the unintended consequences of full removal.

A holistic approach should balance out the anticipated loss in value of the artificial reef ecosystem services along with the benefits of managing the ecosystem in its current state or partial state, against the impacts of full removal.

Identify and minimise unintended consequences

Importantly, this flexible approach in no way constitutes a license to pollute as measures aimed at ensuring the safe abandonment of the installation, such as flushing of pipelines, would be incorporated in a viable decommissioning option.

In fact, a well-designed decommissioning strategy would identify and minimise unintended consequences to the environment – particularly important given the extensive pressures on marine ecosystems at present, including depletion of fish stocks on the seafloor, loss of habitat and further ecosystem components under conventional fishery management, and changes to ocean circulation and stratification induced by climate change.

Scientific analysis of alternatives

The analysis of decommissioning alternatives for each individual structure should be based on a transparent assessment, utilising 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.

Critically, the range of costs, benefits and wider impacts of the various decommissioning options should be identified and the trade-off should be clearly presented. This will ensure that the net environmental and socio-economic impacts are analysed alongside technical, cost and safety criteria, facilitating a well-balanced decision for an individual platform as part of a wider collection of biologically connected offshore installations.

Decommissioning into the future

Ultimately, how the government decides to approach the decommissioning of oil and gas platforms will set an example for a range of newer offshore infrastructures such as wind turbines, which will require decommissioning in the near future. Keeping tabs on circularity, design, installation and end-of-life considerations of new infrastructure will ensure we have learnt from the oil and gas industry, and fully incorporating them into the early project planning phases will hopefully enhance the habitat value of the structures in the marine environment, minimising disturbance to the ecosystem.

FURTHER INFORMATION

Ramboll uses a net environmental benefit analysis (NEBA) framework to value the environment. NEBA is a cost-benefit analysis tool that considers environmental, societal, economic, energy, safety and technical feasibility trade-offs between decommissioning options. Criteria can be integrated, but the primary focus is biodiversity and the services ecosystems provide. Decisions may then be taken with greater transparency and with known consequences. It is likely that decisions taken to optimise a service, such as retaining the structure for spawning habitat and nurseries, will benefit related services like food production through seafood fisheries. These decisions may be especially important when taken in a wider context, such as reports of over-fishing leading to the depletion of fish stocks in the region.