This Saudi site lists reserves of 261 billion barrels.
http://www.saudinf.com/main/z002.htm Alaska's Prudhoe Bay oil field (original producible reserves of less than 10 billion barrels), the largest feld in North America, is dwarfed by the big Saudi oil fields like Ghawar (67 billion barrels of remaining reserves after over 50 years of production). For remaining reserves of some of the big Saudi fields, see:
http://www.energyforum.gov.sa/html/facts.html