"We dislodged them (the hostage takers) on Thursday, flushed them out of the platforms which we have taken over and we have arrested about 30 of them," navy Captain Sinefi Hungiapuko said on Friday.
"All those who were arrested will be brought to Abuja for prosecution. We need to teach them a lesson," he added.
He said no one was killed in the rescue operation but confirmed that some people were injured when "they put up resistance". He did not give details.
The Lagos-based This Day newspaper reported that one kidnapper was shot dead in the operation.
Hungiapuko said that no ransom was paid to the hostage-takers "since we managed to overpower them."
All those held captive by the armed gang were Nigerian nationals who worked for US energy giant Chevron Texaco.
According to the oil firm, the hostage-takers are members of a security firm recruited from the local ethnic Ijaw community by Chevron Texaco to protect the oil wells and pipelines in the Foropa district of southern Bayelsa state, part of the oil-rich but socially troubled Niger Delta region.
Chevron and other oil majors operating in the region often pay local communities in the Niger Delta to provide security for their rigs.
"They are terrible people. We do not know where they get their hands on such weapons"
public affairs manager,
The security teams are not armed by the oil firms but the region is awash with illegal weaponry, paid for by the profits of piracy, smuggling and theft of crude oil from vandalised pipelines.
Chevron Nigeria's public affairs manager Sola Omole said in a statement on Thursday that the kidnappers were heavily armed and had demanded a large sum of money to release the workers and leave the rigs.
"They are terrible people. We do not know where they get their hands on such weapons," he said, confirming a press report that the group was equipped with AK-47 Kalashnikov assault rifles and grenades.
Nigeria is Africa's largest producer of crude oil, with a daily export quota from the OPEC oil cartel of more than two million barrels per day.
Nigerian and expatriate oil workers are often kidnapped by pirates and local tribes but - although the oil firms deny paying ransoms - they are usually released unharmed.