A 24-hour strike is taking place on a number of North Sea oil platforms in a row over rota changes.
Talks between the Unite union and Aker and Petrofac broke down on Monday without agreement.
A series of strikes was earlier announced after more than 200 oil workers voted for industrial action.
The 24-hour strike involving the union's members is taking place on the Elgin-Franklin, North Alwyn and Dunbar platforms.
Total, which operates the platforms, said: "We have carried out a full risk assessment to ensure our platforms remain a safe working environment for those who remain at their posts. Production from our platforms will continue."
The Unite union claims a move to a three weeks on, three weeks off rota pattern is a danger to health.
Aker said it was hopeful the situation could be brought to a conclusion in due course.