What Makes an Oil Field a Supergiant

Geologists class fields by recoverable reserves: giants hold over 500 million barrels and supergiants over 5 billion. Only a few dozen supergiants have ever been found, yet they account for the large majority of all oil ever produced.

Ghawar alone once matched the output of whole provinces. Size alone does not guarantee fame: economics, politics and geology decide whether a supergiant becomes a Ghawar or stays stranded like parts of the Orinoco belt.

Most supergiants were found before 1970, a fact that worries forecasters..