With the discovery of stratigraphically trapped oil in Washington County, Colorado, in 1952, interest in the south-central part of the Denver basin greatly increased, resulting in the discovery of the Adena field in 1953, the largest reserve developed to date.

The Dakota "J" reservoir embraces approximately 12,000 acres and contains substantially more than 40 million barrels and 32 billion cubic feet of recoverable oil and gas. During the first year of production, more than 3 million barrels of oil were produced, resulting in a pressure decline of 92 pounds.

Oil is produced predominantly from the Dakota "J" sandstone and secondarily from the Muddy "D" sandstone of Cretaceous age. Structurally the field is characterized by relatively uniform northwest dip of approximately 50 feet per mile, though local terracing and nosing exist. Accumulation is controlled by stratigraphic variation within and below the producing zones. Locally, a permeability barrier is present on the eastern side of the field, while a basal seal below the pay zone prevents migration into the main sand body.

Most of the oil now produced in the Muddy "D" sandstone is found in the northwestern extremity of the field and is associated with those areas where the formation has its best development of porosity, permeability, and thickness.

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