The Wind River basin contains more than 60 oil and gas fields, located chiefly on structural traps that developed during Laramide deformation in latest Cretaceous and early Tertiary times. Seventeen different sedimentary formations are petroleum bearing. Principal reservoirs are the Pennsylvanian Tensleep Sandstone, Permian Park City Formation, Cretaceous Cloverly, Thermopolis (Muddy Sandstone Member), Frontier, and Lance Formations, and Paleocene Fort Union Formation.

Until latest Cretaceous time central Wyoming was part of the stable shelf that sloped gently westward toward the Cordilleran geosyncline. Deposition occurred mainly in shallow seas, and slight changes in base level commonly resulted in widespread facies changes and unconformities within the Paleozoic and lower Mesozoic sedimentary sequences. Because (1) the regional dip of the strata was westward and (2) the overburden pressures were greater on the west during the pre-Laramide period, fluids generally migrated as far eastward into the present basin area as structure and individual reservoir conditions permitted. Regional stratigraphic and structural relations suggest that primary accumulation of hydrocarbons occurred in many reservoirs before folding began.

Pronounced subsidence of the central basin area during the Laramide induced a secondary migration of fluids updip toward structural traps that developed contemporaneously along the basin margins. However, facies changes, unconformities, and porosity and permeability barriers within many of the pre-latest Cretaceous reservoirs inhibited wholesale flushing of all the oil and gas formerly trapped in the central basin area. Untapped stratigraphic traps or combinations of stratigraphic and structural traps therefore still may be present downdip from the present margins of the basin.

Exploratory drilling has not tested the Frontier and older Mesozoic rocks in approximately 3,500 sq mi of the central, structurally deepest part of the Wind River basin; more than 4,500 sq mi of Paleozoic rocks is untested. The common reservoirs are less than 15,000 ft below the present ground surface in approximately 2,000 sq mi of the untested areas.