A holistic approach to decommissioning

Special from DOF Subsea

Construction support vessel ‘Skandi Constructor’ (photo: DOF Subsea)
Construction support vessel ‘Skandi Constructor’ (photo: DOF Subsea)

The decommissioning market is worth tens of billions of pounds in the UK alone, and spend on this activity is expected to ramp up to a peak of more than GBP 2.5 billion per year over the next two decades, according to the North Sea Transition Authority. This offers a long-term opportunity for the supply chain to develop a wider variety of cost-efficient services and work collaboratively to increase efficiencies.

Guidebase recovery (photo: DOF Subsea)
Guidebase recovery (photo: DOF Subsea)

Kinsale Gas fields
Earlier this year, Norwegian engineering and marine services player DOF Subsea was awarded a contract for multiple well severance and recovery works associated with the decommissioning of the Kinsale Gas fields. Located in the Celtic Sea, the wells are approximately 40 to 70 kilometres off the South coast of County Cork in Ireland.

Operated by PSE Kinsale Energy, the areas are being decommissioned due to declining gas reserves. This includes the Kinsale Head, Ballycotton, South-West Kinsale, and Seven Heads gas fields, which were developed between 1978 and 2003.

The offshore infrastructure of the Kinsale Area gas fields lies in approximately 90 metres deep water and comprises of two large steel-jacketed platforms, Kinsale Alpha and Kinsale Bravo.

The project, which saw DOF Subsea collaborate with Claxton Engineering, involved the engineering, preparation, and removal of the Kinsale area subsea wellheads in the Irish Sea between March and June 2022.

The scope of work included project management, engineering and marine works for the removal and recovery of subsea infrastructure from the gas fields, including severance and recovery of 10 subsea production wellheads, four exploration and appraisal wellheads, and two Xmas – tree support piles and recovery of 36 Xmas tree legs and three guide bases.

Skandi Constructor
The offshore work was performed by the DOF owned asset, Skandi Constructor vessel with project management and engineering support from the DOF Subsea office in Aberdeen, and Claxton Engineering providing the specialist tooling as a subcontractor.

Recovery of the Ballycotton wellhead (photo: DOF Subsea)
Recovery of the Ballycotton wellhead (photo: DOF Subsea)

The Skandi Constructor is an environmentally friendly vessel, designed for well intervention services; subsea construction and equipment installation; inspection, repair and maintenance; and remotely operated vehicle (ROV) services across a wide range of water depths and environmental conditions.

The recovered subsea infrastructure was offloaded to a local port in Cork to be either recycled or repurposed.

Stuart Nelson, DOF Subsea project manager, says, “The project was a massive undertaking, with 60 offshore and 15 onshore personnel being involved and a comprehensive project management, engineering, and marine works package ensuring seamless project delivery.”

Wellhead laydown frame (photo: DOF Subsea)
Wellhead laydown frame (photo: DOF Subsea)

“The decommissioning project was a great example of industry collaboration between DOF Subsea and Claxton Engineering as both companies used their respective experience and expertise to provide a safe, cost-efficient solution,” he adds.

“The feedback received from our client was excellent, both on our performance and the timely delivery. While we are a longstanding player in the decommissioning space, it is also an area that we would like to develop further. We are always looking for ways to increase our breadth of capabilities and explore novel approaches to support the industry, Nelson continues.

Subsea service specialist
DOF Subsea is a specialist subsea service business that provides subsea engineering and marine services in challenging environments, complemented by a team of experts with global experience in offshore operations, reducing project risk, increasing efficiency, and improving safety performance.  The company owns a large fleet of nearly 60 modern subsea construction, intervention, and survey vessels.

Earlier this year, Norway’s DOF Subsea has won multiple new project awards and contract extensions in the North Sea, Europe, and Africa, totalling more than 500 vessel days and a combined value of more than USD 80 million.

The DOF Subsea team will be attending the Offshore Decommissioning Conference, taking place in St Andrews on 21-23 November 2022.