Militant attacks have cut Nigerian oil output by half a million bpd

LONDON/LAGOS (Reuters) - Nigeria's oil production has fallen by at least half a million barrels per day (bpd), Reuters calculations show, because of militant attacks in the Niger Delta region, most claimed by a new group calling itself the Niger Delta Avengers.

The group has made multiple attacks on infrastructure belonging to oil majors Shell, ENI and Chevron, vowing to reduce output to zero in what is typically Africa's largest oil exporter.

President Muhammadu Buhari cancelled a planned visit to the region last week, which some observers said was a missed opportunity to calm tensions in a region that accounts for a large portion of Nigeria's oil production.

The attacks have forced companies to declare force majeure on Bonny Light, Brass River and Forcados crude oil, and in May helped to push Nigeria's oil production to 22-year lows.

ExxonMobil's force majeure on Qua Iboe -- declared after an accident -- was lifted on June 3.

State oil company NNPC's spokesman Garba Deen Muhammad said Nigeria's production had not dropped below 1 million bpd.

"Our position before the attacks was 2.2 million bpd, but the attacks have affected production to the tune of about 600,000 to 700,000 barrels, so our current production level is hovering around 1.6 million bpd," Muhammad said.

Below is a table listing all Nigerian grades and outlining those affected by pipeline disruption and militancy, based on information from the companies, oil traders, Nigeria's oil minister and Reuters estimates.

(Reporting by Libby George, Julia Payne and Alexis Akwagyiram; Editing by David Goodman)