BP puts UK field in rearview mirror as DeepOcean’s vessel pulls largest SSIV out of North Sea (Gallery)

Norway-based ocean services provider DeepOcean has tucked a new decommissioning milestone under its belt by removing what has been deemed to be the largest subsea isolation valve (SSIV) in the North Sea, as part of the decommissioning campaign for underwater infrastructure that made up the facilities at a field that used to produce hydrocarbons for the UK-headquartered energy heavyweight BP.

Over 1,200 tons of subsea equipment at BP’s Miller field was put on DeepOcean’s removal list due to a deal, described as ‘the first of its type’ in the North Sea. After the field, located around 150 miles northeast of Aberdeen, ceased production in 2007, all wells were plugged and abandoned in 2008. While the topsides and jacket remained at the site for years, they were taken for recycling and disposal in 2017 and 2018, when more than 40,000 tons of equipment were transported to Norway for onshore demolition and recycling.

When the UK-based oil major notified the North Sea Transition Authority (NSTA) about the sale and purchase agreement (SPA) it arranged with DeepOcean in the fourth quarter of 2022, the company underlined that the contracting solution would allow it to transfer title to “a competent contractor” as part of a decommissioning solution for the removal and recycling of infrastructure, providing the contractor with more schedule and execution flexibility.

Thanks to the deal with the Norwegian firm, the next Miller decommissioning phase was expected to result in the removal and recycling of subsea equipment, encompassing a pair of subsea isolation valves (SSIVs), umbilicals, and concrete mattresses. While the SSIVs and hydrocarbon-free connecting spools were calculated to weigh about 720 tons, stabilizing materials, including concrete mattresses and grout bags amounted to around 576 tons.

The offshore scope of work was anticipated to be wrapped up before the end of 2024. However, the pipeline decommissioning work -which would cover a 30″ gas export line that transported processed gas from the Miller platform to the St. Fergus Gas Terminal, an 18″ oil export pipeline linking the field with the Brae Alpha platform, and a 16″ gas linkline connecting the Miller platform to Brae Bravo – was subject to a future program.

According to Joe Leask, BP’s Decommissioning Compliance and Strategy Manager, the removal of the largest SSIV, weighing almost 400 tons, in the North Sea last week was part of BP’s final commitment, representing the end of the Miller decommissioning project. DeepOcean’s Edda Freya construction support vessel (CSV) lifted the structure out of the North Sea.

Originally intended to be installed by CSV, the Miller SSIV was installed by the DB102, now known as Heerema’s Thialf. In Leask’s view, this demonstrates the size and scale of the structure removed by a CSV, thanks to what BP’s Decommissioning Compliance and Strategy Manager has described as “DeepOcean’s innovative engineering and fleet capability.”

Leask highlighted: “The workscope was completed as part of the wider Miller and Don subsea scope which enabled economies of scale. The contract was awarded to DeepOcean in a first of its kind contracting methodology in the North Sea. The contract was a sale and purchase agreement (SPA) which effectively sold the subsea infrastructure to DeepOcean on the seabed, rather than transferring ownership on the quayside.

“This allowed BP’s oversight of this project to take place at a higher level and placed trust in the UK’s competent decommissioning supply chain. All in, the Miller and Don subsea scope utilised 4 different vessels from DeepOcean’s fleet on 11 offshore campaigns, with over 100 days offshore in the last 2 years.”

The Miller field, situated 270 km northeast of Aberdeen in Blocks 16/7b and 16/8b in the Central North Sea, was operated by BP with ConocoPhillips and Shell, as partners. On the other hand, the Don field, located approximately 230 km northeast of the Shetland Islands in the UK sector of the Northern North Sea in 160 m of water, was also operated by BP with ConocoPhillips as its only partner.