The men were working on a ship off the Nigerian coast for Norway's Petroleum Geo-Services (PGS) when they were abducted by armed men in speedboats.
The villagers who took the oil workers had demanded basic amenities and money for their release.
The men were released on Tuesday and transported by authorities to Yenagoa, capital of the southern Bayelsa State, said Ekiyor Welson, spokesman for the local state government.
Dozens of foreigners have been kidnapped in the oil-producing Niger delta. The high risk has caused hundreds of workers to pull out of the region and reduced Nigerian oil output by 500,000 barrels a day.
Niger Delta groups such as the Movement for the Emancipation for the Niger Delta (MEND) say they are fighting for a greater share of oil wealth from oil companies and the government.
Most hostage-takings have ended with the victims being released unharmed.