Forty-five oil fields with recognized ultimate recoveries larger than 500 million bbl have been found in seven provinces in North America. The earliest find was in 1865 and the latest in 1962. Recognition of more recent discoveries as giants will probably increase the population to 51 fields. Examination of reservoir age, lithology, trap and depositional environment leads to the conclusion that there are no diagnostic characteristics common to all of the giants; however, Paleozoic age, shallow-marine environment, sandstone lithology, and structural traps which have surface expression are the preferred modes. Uncommonly thick reservoir rock or unusual development of porosity and permeability are not required.

Twenty-five to twenty-eight more giant oil fields remain to be found, based upon current projections. Under present, or slightly improved, exploration economics the twenty-fifth future giant may not be found until 2060.