Giant oil fields are the world’s largest. There are two ways to define a giant oil field. One is based on ultimately recoverable resources (URR), and the second is based on maximum oil production level. The URR definition considers giants to have more than 0.5 Gb of ultimately recoverable resources. The production definition assumes a production of more than 100,000 barrels per day (b/d) for more than one year. IEA classify super-giants as fields with more than 5 Gb of initial 2P reserves. Giants contain more than 500 million barrels of initial 2P reserves, and large fields contain initial reserves of more than 100 million barrels. The most important contributors to the world’s total oil production are the giant oil fields. Their contribution to world oil production was over 60% in 2005, with the 20 largest fields alone responsible for nearly 25% . Giant fields represent roughly 65% of the global ultimate recoverable conventional oil resources. The overall production from giant fields is declining, because a majority of the largest giant fields are over 50 years old, and fewer new giants have been discovered since the decade of the 1960s. About 500 or about 1% of the total number of world oil fields are classified as giants. Thus, with few exceptions, e.g., Ghawar, the contribution from a single field is generally small compared to the total.