Enough concrete poured to fill three Olympic-sized swimming pools

June 2023 – The skyline in Placentia Bay, NL looks a little different these days. After 69 days, more than 8 million litres of concrete poured (or 8,000 m3 if you’re into construction) and gaining 92.35 metres in height, the concrete gravity structure (CGS) conical slip form operation on the West White Rose project is complete. This is the culmination of years of planning and hard work, and a milestone on the project’s critical path for success.

Slip forming is a method used to pour concrete with a continuously moving formwork system. It’s commonly used for tall structures, such as the CGS, and involves rebar and concrete being placed (by hand) into formworks that constantly move upwards. The continuous movement ensures there are no joints, as new concrete is constantly being poured and adhering to old concrete, leaving no leak paths for water and helping ensure the structure is strong. The unique and challenging part of slip forming is its continuous nature; it cannot stop. It can, however, be slowed down when necessary to overcome challenges. For example, there were occasions when weather impeded progress on the slip. Rebar is placed within the concrete forms and when winds were too high for cranes to move rebar onto the structure, the work had to slow.

“It’s really satisfying to see this particular part of the job completed, safely and to such high quality,” says Mike Rudofsky, Senior Manager, CGS Project at Cenovus Energy. “COVID-19 shut us down in 2020 just days before we were supposed to start the conical slip. We had to rebuild our teams and try to pick up that momentum again. It’s been a long journey, but the way we came together demonstrates our company values in action. We had success because we did it together and focused on doing it right.”

The CGS is being built in Argentia, NL and will support the topsides of the drilling platform. Risers will be extended from the topsides, down the centre of the CGS and integrated with the rest of the subsea infrastructure in the White Rose field. If the topsides could be considered the brain of the platform, where all the decision-making and processing takes place, the CGS is the body supporting the brain and housing the valuable components to facilitate production.

“It’s a deceptively simple looking structure, when you look at it from the outside but it’s very complex,” says Nicole Breau, CGS Site Health and Safety Lead at Cenovus. “Concrete and rebar are integrated seamlessly to create the structure, but what’s incredible is that someone’s hand touched every piece of rebar and every load of concrete. Everyone involved is really proud of the safety record and of the high quality of the job done.”

This is not the end of work in Argentia, with more to do before the CGS is ready to be installed in the White Rose field. The final six metres of concrete will be poured using a different form of concrete placement, to bring the structure to its full height of 146 metres. In parallel, the team will start installing all the interior mechanical outfitting, including decks that were placed inside the CGS in 2019. Panels are also being constructed and installed on the caisson roof of the structure, and there is a variety of mechanical work necessary to get the structure ready to float and tow offshore in 2025.