Approximately 19.4 billion bbl of oil and 119 tcf of nonassociated gas have been discovered in the Mid-Continent as of January 1, 1978. Although these volumes of hydrocarbons were trapped in thousands of fields throughout the Mid-Continent, the bulk of these resources were emplaced in a relatively few fields: about 14.2 billion bbl of oil have been found in 111 significant and giant oil fields, and 103 tcf of nonassociated gas have been discovered in 57 significant and giant gas fields. Permo-Carboniferous reservoirs are important in 101 of the large oil fields and 55 of the large gas fields; these fields contained 9.5 billion bbl of oil and 99 tcf of gas, respectively. Our calculations of the total oil and gas accumulations in Permo-Carboniferous reservoirs are extrapola ed from these data.

About 2.1 billion bbl of oil and 5.1 tcf of nonassociated gas accumulated in Lower Carboniferous (Mississippian) reservoirs. Most of this oil and gas was stratigraphically trapped in Upper Mississippian sandstones and carbonates which are truncated at the pre-Pennsylvanian unconformity surface.

Approximately 8.8 billion bbl of oil and about 31.9 tcf of nonassociated gas have been found in Upper Carboniferous (Pennsylvanian) reservoirs in the Mid-Continent. Most of these oil and gas accumulations were stratigraphically trapped in lenticular sandstone bodies; the environments in which the majority of these sandstones were deposited range from fluvial-deltaic to shallow marine.

About 2 billion bbl of oil and 77.7 tcf of nonassociated gas accumulated in Permian reservoirs. Most of these hydrocarbons accumulated in rocks of Lower Permian age in the Hugoton-Panhandle-Panoma fields. The oil and gas in these fields were trapped by regional changes in lithofacies with associated hydrodynamic gradients.

Significant stratigraphic accumulations of oil and gas will continue to be discovered in the Mid-Continent even though much of this region is now in a late mature stage of exploration and development.