An unamed security sourse said two expatriates, an American and a Briton, working for Petroleum Geo-Services (PGS) had been been kidnapped on Thursday morning from aboard MV Commander.
An armed gang raided the ship and sped away in boats with the hostages, said the security official.
It was the latest in a wave of kidnappings against foreigners 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.
PGS is a Norwegian-based oil service company specialising in seismic studies.
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.
They say people in the area remain impoverished while oil is drawn from their land.
Dozens of foreigners have been kidnapped this year.
The hostage-takings have usually ended peacefully, with those seized being set free after negotiations.