"If we have to take strike action, then I would expect this to have a major impact on production from the Ninian field," Unite representative John Boland told Reuters in an email.
The workers set to strike are employed on the Ninian Central, Ninian South and Tiffany platforms, the union said.
The Ninian crude stream feeds into the blend of Brent, Forties, Oseberg, Ekofisk and Troll (BFOET) North Sea crudes that underpins the Brent benchmark.
The BFOET grades are due to load 820,000 bpd in November. The Brent stream is due to load three cargoes in November, which translates into around 60,000 barrels per day (bpd). [O/LOAD]
The Ninian and Tiffany fields produce around 13,000 bpd, according to data from the Oil and Gas Authority.
(Reporting by Shadia Nasralla; editing by Edmund Blair and Jason Neely)