Optimising the decommissioning of concrete mattresses and support structures in the North Sea

Background
The cost-estimates associated with decommissioning oil and gas infrastructure in the North Sea vary widely (e.g. total £30 - £100 billion, with £17.6 billion spend projected for the next 9 years). Industry is obliged to make a ‘comparative assessment’ to evaluate options in relation to mattress decommissioning. Re-use of materials in coastal defence or around new technologies (offshore wind) is an intuitively better solution to mattress-disposal than alternatives such as onshore landfill. However, before offshore re-use can be considered, the environmental costs-and-benefits must be established. This PhD aims to support industry and decision-makers by providing them with the necessary evidence to identify the optimal decommissioning option. Re-use of materials has considerable potential to reduce costs to the O&G sector (and taxpayer), and bring cost-benefits to other industries such as offshore wind. This will increase the sustainability of both sectors and generate wealth and competitiveness through cost-reduction.

PhD Details
The North Sea has been the centre of the UK’s oil and gas (O&G) industry since the 1970s. Production for many assets is now declining and O&G-related structures are beginning to require decommissioning. There are 35,000 – 40,000 concrete mattresses in the North Sea, each consisting of a 2-dimensional layer of concrete blocks (joined on four sides) that are laid across subsea structures to afford them protection. The environmental implications of different decommissioning options, including re-use as scour protection material (de facto artificial reefs) or in the construction of de jure artificial reefs, are largely unknown. This PhD student will:
1. Quantify and characterise the current status of concrete mattresses (Note1) including location (depth, supporting substratum) and type
2. Quantify and characterise the likely challenges and issues for the re-use of decommissioned mattresses including potential uses in offshore renewables and coastal defence and the issues surrounding this e.g. cleaning/biofouling and interim storage
3. Review the legal and regulatory issues pertaining to the re-use/re-cycling of mattresses and their use in the creation of artificial reefs, including residual liability, non-indigenous species and material life-span
4. Qualify and quantify changes in ecosystem service provisioning occurring as a consequence of broad-scale reef-creation, particularly in relation to sector-specific fisheries (Note 2)
5. Consider potential changes in the relevant regulatory environment following ‘Brexit’.
6. Summarise findings and make recommendations to policy makers and industry

This PhD will build on an extensive, existing partnership between the Supervisors and the O&G industry and regulators. These contacts have been developed through the NERC Grants NE/N019369/1 (Note 3) and NE/PO16537/1 where we are actively collaborating with MSS, BEIS, Scottish Fishermen’s Federation, Oil and Gas UK, Shell, BP and SNH among others. We will also promote the PhD student’s research through our contacts in the MASTS Oil and Gas Forum (Wilding and Rouse as co-convenors).

Opportunities
The successful applicant will develop an extensive and diverse range of contacts within the regulatory communities and oil and gas industry. Using these contacts, and learning and applying the skills required to complete the PhD will give the successful applicant a broad perspective on the major issues related to oil and gas decommissioning in North Sea and beyond. The pressing political, regulatory and academic interest in addressing the challenges in relation to decommissioning is set to continue and expand. Following graduation, the candidate will be very well positioned to move into an exciting and remunerative career.

Supervisory team
The main supervisory team will consist of Tom Wilding and Sally Rouse. Tom and Sally will provide overall oversight and guidance and facilitate liaison with industry and regulators. Sally will oversee mapping and data collation aspects of the PhD. Additional supervisors will include Ian Davies (MSS) to provide further regulatory-context and Simone Martino (SAMS) to provide guidance in relation to ecosystem valuation. This PhD forms one of a pair of related PhDs. Close co-operation between the successful candidates is expected.

Notes:
1 - In this context ‘mattresses’ includes related support structures such as grout-bags
2 - Fisheries interactions will be sector specific, for example, artificial reefs are likely to benefit most the static gear-sector.
3 - http://gotw.nerc.ac.uk/list_full.asp?pcode=NE%2FN019369%2F1&cookieConsent=A

Informal project specific enquiries can be made to: [Email Address Removed]