The Obana, described as the world's largest self-elevating heavy-lift jack-up vessel, recently completed its first decommissioning contract in the UK North Sea, removing four jackets and topsides from the Amethyst and Galahad fields. The vessel features a massive 7,000-square-metre deck with a 5,500-tonne weight capacity and is equipped with a 2,000-tonne crane and significant lateral skidding capacity for heavy modules.

Petrodec's Integrated Decommissioning Strategy

Netherlands-headquartered Petrodec, part of the Perenco Group, offers an integrated, turnkey decommissioning service covering well abandonment, topsides and jacket removal, and recycling. The Obana is central to this strategy, operating alongside the jack-ups Erda and Haeva to provide a flexible, optimised campaign approach. By bringing these services in-house, Perenco aims to reduce UK decommissioning costs by up to 30%, streamline operations, and build internal competence for both its own assets and third-party operators.

Design and Economic Rationale for the Obana

The concept for the Obana emerged from modifying an existing Galaxy III rig design by adding a new mid-section to create ample deck space, a cost-effective solution that utilised an existing crane. Petrodec chose a jack-up design over floating heavy-lift vessels primarily for the interconnected, modular platforms common in the Southern North Sea. A jack-up provides a stable, long-term working platform for preparatory work and piece-by-piece removal at a cost four to five times lower than a floater, with lower emissions. Its large deck also allows for onboard waste segregation and partial demolition.

Operational Challenges and Lessons Learned

Decommissioning campaigns involve lengthy preparation, often taking nine to twelve months, and face challenges from outdated or inaccurate historical platform documentation, necessitating reverse engineering and pre-deployment ROV inspections. The Southern North Sea environment presents difficulties such as strong currents, low visibility limiting ROV operations to about four hours daily, and sandy seabeds that complicate pile cutting. The first campaign revealed that jacket drawings did not always match reality, underscoring the need to verify all data.

Market Outlook and Future Operations

The Obana is under contract for the next 18 months to remove assets from Perenco's Ravenspurn, Amethyst, and Pickerill fields and is being marketed for new contracts, with multiple inquiries from the UK and Dutch sectors following regulatory approval in the Netherlands. Petrodec aims to extend the rig's operational water depth from 65 to 122 metres to access more regions. While a significant decommissioning backlog exists—with 59% of operators failing to meet well abandonment obligations—the volume of ready infrastructure may be less than expected, as platforms can remain operational with few profitable wells. Operators seek economies of scale through larger contracts.

Infrastructure and Investment Needs

A key constraint is the lack of suitable UK decommissioning yards, particularly in East Anglia, where ports lack necessary equipment and have small entrances. In response, Dixstone, Petrodec, and Perenco are developing dedicated yards in Great Yarmouth and Lowestoft, with plans to transport smaller decommissioned blocks to Great Yarmouth from next year. Investment is critical, as decommissioning is a long-term industry spanning the next two decades, and without prepared infrastructure, the UK risks losing revenue and local jobs.