Royal Dutch Shell Plc shut the Trans Niger oil pipeline after a fire, threatening to worsen a drop in Nigerian output due to unplanned disruptions. The line can transport about 180,000 barrels a day to the Bonny Export Terminal in the Niger Delta was halted Tuesday due to a blaze at Kpor in Ogoniland, Precious Okolobo, a company spokesman in Lagos, said Thursday by phone. Shell declined to comment on the impact on production. Nigeria’s daily output dropped by 200,000 barrels to 1.45 million in December, ending three months of gains as the African nation struggled to restore capacity after a year of militant attacks on oil infrastructure. Production fell to 1.39 million barrels in August, the lowest level since 1988, according to data compiled by Bloomberg.