The union umbrella group National Oil Workers Federation, FUP, said it was staging the protest – the second in less than three weeks – in protest against changes to overtime payments.
The 46 oil platforms in the Campos Basin are responsible for more than 85% of Brazil’s crude oil.
Petrobras declined to comment about the strike plans, according to Dow Jones Newswires.
On 25 July workers at 40 of the 46 Campos Basin platforms took part in the work stoppage, during which only essential services are maintained.
The FUP, which represents 15 oil unions, said it hoped to exceed this participation rate with the latest demonstration.
Such strikes generally have a limited effect on Petrobras output because of their short duration, but nonetheless the latest protest comes at a time when the oil major struggles to boost crude oil output amid ongoing maintenance.
The last major strike at Petrobras in July 2008 saw oil workers walked off the job for five days to protest work profit-sharing proposals and other issues, in an action that cost Petrobras about 63,000 barrels of crude oil production per day.