Oil traps in the Upper Minnelusa were examined for the area 50N to 54N and 67W to 70W. This includes approximately half of all Upper Minnelusa penetrations.

The 89 purely stratigraphic traps were classified according to their dominant trapping elements. A statistical analysis shows that 80–85% of the oil is found in the three trap types, with five other trap types accounting for the remainder.

Effective subsurface delineation of the traps requires mapping of four different trap elements. Updip loss of permeability within a sand zone is involved in 50% of the traps. Paleotopography is involved in 22% of the traps. Lateral change of porous dune sands to non-porous interdunal deposits is involved in 8% of the traps but is the principal trap element in the C Sand. Seven different subsurface maps are needed to do a reasonable job of locating traps in the various productive zones.