Oil fields that contain at least five billion barrels of recoverable oil ​ — called supergiants — ​ are the largest in the classification, while the second largest (from five hundred million to five billion barrels) are called world - class giants.
Pie pirmās kategorijas pieder tādas iegulas, no kurām var iegūt vismaz 5 miljardus barelu naftas, bet pie otrās kategorijas — tādas, no kurām var iegūt no 500 miljoniem līdz 5 miljardiem barelu naftas.