Nigeria has lost more than 130million barrels of crude oil since the beginning of this year after a spate of attacks by militants in the Niger Delta region.
Eni is the latest firm to be the fall victim militant attacks in Nigeria.
Seven contractors have been released after they were kidnapped by gunmen in Nigeria four days ago.
Nigerian militants have called for a referendum on breaking up the country's federation.
Nigerian militants whose attacks on oil infrastructure have sent output plunging to its lowest level in 27 years said for the first time that they are considering peace talks, even as they threatened to rethink their policy of avoiding bloodshed.
A group of former Nigerian militants has called on the Niger Delta Avengers to join in discussions with the country's government.
Islamic State militants have attacked a state-run natural gas plant outside Baghdad, killing at least 14 people, officials said.