NEW YORK --- Reports of election-related violence in Nigeria spurred a round of volatile trading today, with oil prices climbing as high as $64.21 and falling as low as $62.55 a barrel. But by afternoon, the price of light, sweet crude for May delivery was flat at $63.63 on the New York Mercantile Exchange. Brent crude prices for June delivery, according to the Associated Press, fell $1.03 to $67.60 a barrel on London's ICE Futures Exchange. Nigeria is the eighth largest exporter of oil in the world.