The price of North Sea Brent crude oil has fallen to around $91 per barrel, the lowest level in more than two years and about 21% lower than its year-to-date peak of $115 per barrel on June 19. Before its recent decline, average monthly Brent spot prices had traded within a narrow $5 per barrel range, from $107 to $112 per barrel, for 13 consecutive months through July 2014.