Royal Dutch Shell PLC has evacuated nonessential staff from one of its Nigerian oil fields amid mounting militancy in the country’s oil-rich Niger Delta region. The company has reduced staff levels at its Eja oil field about 15 kilometers (10 miles) off the coast of Nigeria, according to a person familiar with the situation. The move follows an attack on one of Chevron Corp. CVX -1.48 % ’s offshore facilities last week that knocked out 35,000 barrels a day of the company’s oil production. The attack was claimed by a militant group called the Niger Delta Avengers, which threatened further action against foreign oil companies operating in the country. “We continue to monitor the security situation in our operating areas in the Niger Delta and are taking all possible steps to ensure the […]