Updated from 12:04 p.m. ESTOil prices soared above $64 a barrel Friday, continuing a weeklong bull run that has added 6% to the front-month contract. Light, sweet crude increased 35 cents to settle at $64.26 a barrel thanks to ongoing refinery maintenance, lower domestic crude inventories and supply problems in Iran and Nigeria. "Supplies seems absolutely adequate, but political problems are not," said Eric Bolling, an independent oil trader in New York. "As you get closer to the weekend, people are more concerned about geopolitical issues." An Energy Department report Wednesday showed that domestic oil stockpiles dropped for the first time in six weeks. Analysts had been expecting an increase. Supplies decreased 1.3 million barrels to 338.6 million barrels thanks to increasing refining capacity and lower imports. Still, crude stocks remain 9% above last year. In February and March, refiners typically shut some units down for seasonal maintenance as they retool to make cleaner, summer-blended gasoline. Their maintenance schedule this year has been longer than usual because refiners have to produce gasoline that can be blended with ethanol by May 31. Crude, which is processed into heating oil and gasoline, builds up because refiners are operating at lower capacity. Prices could rise even further as refineries undergo routine maintenance. Exxon Mobil ( XOM) has closed some units at its Baton Rouge, La., refinery, which processes 488,000 barrels a day, and will shut down others at its Baytown, Texas, operation in May. The Texas refinery processes 564,000 barrels a day, making it the largest in the U.S. Attacks on Nigerian pipelines and an ongoing standoff with Iran over its nuclear ambitions have kept oil prices high and offset large inventories. Daily oil production in Nigeria is down 26% to 1.6 million barrels per day thanks to rebel attacks. On Thursday, Italian oil company Eni ( E) said it could not honor its commitments from its Brass River terminal, which loads 200,000 barrels a day, because of a pipeline attack last week. The pipeline carries 75,000 barrels a day.