Workers at three of Total’s North Sea oil and gas platforms began a 12-hour strike at 11:00 GMT Aug. 13, as planned, after talks with the company failed last week, a union official said.

The affected platforms are Alwyn, Elgin and Dunbar.

More discussions could be held this week although nothing had been fixed, Wullie Wallace, regional officer for the Unite union, told Reuters. The workers are striking over proposed changes to their working rotas and pay.

Total confirmed the strike would go ahead and that it was “continuing to engage with its offshore workforce about changing working patterns to three weeks on/three weeks off.”

A separate dispute had ended after workers at its Shetland Gas Plant agreed to “a new three weeks on/three weeks off working pattern,” the company added.

The next, and last, planned strike by the rig workers will be on Aug. 20 and will last 24 hours.

About 45 out of 60 Total workers were set to strike at the three platforms. Outside contractors also work at the fields but they are not involved.

The strike means that production at the fields will be shut down for that period. The three fields' oil production contributes about 45,000 to 50,000 barrels per day (bbl/d) to the Forties and Brent Blend crude streams.

Forties and Brent Blend are key oil grades used to set the dated Brent benchmark that prices more than half of the world’s oil trades. However, oil futures were relatively steady with Brent oil futures up 2 cents at 1251 GMT at $72.83 a barrel.

The fields also contribute about 10% of Britain's total natural gas output.

Prompt British wholesale gas prices were up around 4 percent on Monday with the strike action curbing domestic gas supply.

In a market message, Total said output from Elgin-Franklin, via the Bacton SEAL terminal, would be cut by 10 million cubic meters a day (MMcm/d) from 20:00 GMT Aug. 13 until 05:00 Aug. 15.

Output from Alwyn was also expected to fall by 1.6 MMcm to 0.2 MMcm from 04:00 GMT Aug. 13 until 04:00 GMT on Aug. 14.

Production at the sites will need to be ramped up and ramped down so the overall disruption to normal production is likely to last longer than the 12-hour strike, Oliver Sanderson, lead gas analyst at Thomson Reuters, said.

Employees of oil services company Aker Solutions working on Equinor's Mariner oil platform have called off a planned strike after accepting an improved pay offer from Aker Solutions, GMB Union said on Monday.

Unite the Union that also represented the Aker Solutions workers later issued a similar statement.

Possible wider industrial action by 2,500 workers at the Offshore Contractors Association was still looming. Another union spokesman said that a ballot on whether to take industrial action was still planned but had not yet been sent out.

Total shares were trading 0.65% higher at 12:51 GMT.

Offshore