'Attic' Oil Removed from Shell Bravo Concrete Storage Cell

Deepocean, with Enpro Subsea as a subcontractor, has recently completed the removal of "attic" oil from concrete storage cells at the base of Shell's Brent Bravo platform in 140 meters water depth in the UK North Sea.

A DeepOcean subsea construction vessel deployed Enpro Subsea's F-Decom system to remove ‘attic’ oil from concrete storage cells at the platform's base.

"The system, which on previous campaigns had been deployed directly from platform topsides, was this time deployed from a DeepOcean construction vessel, leading to a significant reduction in operating days per cell," DeepOcean said.

Worth noting, the Shell Bravo platform topsides was removed by the giant Pioneering Spirit vessel in June 2019. The Brent Bravo platform comprised a topsides structure supported by three 12-meter-diameter steel-reinforced concrete legs.

'Only' field-proven system

According to Enpro, its F-Decom system is the only field-proven system for securely accessing fluids within gravity-based structures (GBS) concrete cells "assisting operators to safely meet their decommissioning regulatory obligations to protect Europe’s marine environment."

The project involved Enpro’s offshore engineers and onshore support teams working alongside DeepOcean’s operations and subsea teams onboard the construction vessel, the Maersk Forza. 

Enpro Subsea’s solution centers around its patented 'anchor hub' technology which mechanically locks into the concrete cell cap and allows a suite of tooling (i.e. drilling, sampling, wireline, pumping) to be compact and lighter, enabling it to be easily installed and operated using work class ROVs and operate within a broad weather window.

This is the fourth such campaign the company has undertaken for Shell to support its ongoing decommissioning program in the Brent field, located north-east of the Shetland Islands.

Enpro Subsea engineering director Neil Rogerson said: “The system is well proven, and Shell has previously deployed our F-Decom technology on both their Brent Bravo and Brent Delta platforms. For the 2020 Bravo project, our collaboration with DeepOcean has allowed us to optimize this same low-risk system, specifically for working from a vessel, yielding significant operational efficiencies, and increasing value to our client. As a result, we now have extended the track record of the only field proven system, which can be configured to suit a variety AOR (Attic Oil Recovery) decommissioning programs.”

Roy Nilsen, DeepOcean project manager said. “The attic oil recovery project on Shell’s Brent Bravo platform was a great project for DeepOcean and its success comes from the combination of Enpro Subsea’s F-Decom system and DeepOcean’s expert subsea engineering and WROV capabilities as well as the good collaboration between all parties involved.”