Norway's petroleum output could be reduced by unspecified amount if workers go on strike at nine offshore fields on Sunday, the Norwegian Oil and Gas Association (NOG) said on Friday.
Some 845 workers out of roughly 7,500 employees on offshore platforms plan to strike from June 12 if annual pay negotiations with employers fail, trade unions Safe, Industri Energi and Lederne have said.
If Norway's state-appointed mediator is unable to broker a deal, union members will be eligible to go on strike and the dispute could escalate the following week as more workers may join the strike.
Unions leaders have said that while oil production would likely be hit by any strike action, workers would initially seek to protect gas output due to the tight supply and high prices in Europe.
Any decision on shutdowns is ultimately up to the companies operating each field, however.
"A potential strike could affect the output from affected fields," NOG said in a statement.
A strike would hit ten offshore production and drilling platforms, including Johan Sverdrup P2, Njord A, Valhall, Gudrun, Oseberg East and Oseberg South, as well as three floating accommodation units, the unions said.
A strike of Industri Energi members at Aker BP-operated Valhall would postpone its restart from ongoing maintenance, which is scheduled to end on June 24, NOG added.
Newly installed Johan Sverdrup P2 and renovated Njord A platforms are not producing yet.
All three unions are planning to take on strike their members working at Equinor-operated EQNR.OL Gudrun, Oseberg East and Oseberg South fields.
Gudrun produced 45,700 barrels of oil equivalent per day (boed) in 2021, Oseberg East 5,600 boed and Oseberg South 32,000 boed, official data shows, around 2% of Norway's overall daily oil and gas output.
Equinor declined to say whether these fields would have to shut. "We don't want to speculate about it," a spokesperson said.
Norway pumps just over 4 million barrels of oil equivalent per day (boepd), half in the form of crude and other liquids and half in natural gas, making it a major global energy supplier.
(Reporting by Nerijus Adomaitis, writing by Terje Solsvik, editing by Gwladys Fouche and David Evans)