"The strike action will involve a series of 48-hour stoppages every second week for the first 8 weeks. The action will start on 20 and 21 October," the Unite trade union said.
Industrial action will continue through mid-December and may escalate to an all-out strike after that, the union warned. Employees may also refuse to work overtime from October 18.
Unite chief Sharon Graham said the pay offer on the table was a substantial real terms pay cut that came at a time of skyrocketing costs of living and record profits generated by oil and gas drilling.
"The oil and gas industry is swimming in record operator profits which is being fuelled by the consistently high price of oil and gas. Our offshore members have their union’s full support in fighting for better jobs, pay and conditions," she said.
Strike action will hamper work at BP’s Clair and Clair Ridge platforms as well as Equinor's Mariner platform, among dozens others. Unite said British energy giant BP reported its biggest profit for 14 years in August.