Oregon Basin, southeast of Cody in Park County, is the largest oil field in the Bighorn Basin and one of the largest in Wyoming — an eroded anticline fifteen miles long and six miles wide with two structural highs known as the north and south domes. Nine reservoir horizons have produced across two petroleum systems, and cumulative recovery is reported at roughly five hundred and four million barrels of oil together with hundreds of billions of cubic feet of gas. It is a field that has been managed, rather than merely produced, for a century.
The story begins with the surface. A mine inspector named T. L. Harrison recognized the oil potential of the Oregon Basin anticline in 1908 and left his post to pursue it, backed by French investors operating as Enalpac from 1910. Their wells found substantial gas in Lower Cretaceous sandstones around thirteen hundred feet — one encounter in August 1912 blew rock fifty feet into the air — but the technology of the day could not reach the deeper oil. The company lost its leases to inactivity and wartime financing restrictions.
The Ohio Oil Company, later Marathon, brought rotary equipment capable of drilling to three and four thousand feet and made the field a producer. Accounts differ on the decisive date: the company is credited with the first deep oil discovery in the Permian section in 1924, while the Wyoming State Historical Society dates the first major strike to February 1, 1927, when a well came in at eight hundred barrels a day. Both statements can be true of different wells, and the roster year of 1912 refers to the original drilling rather than to commercial oil.
What followed was ninety years of continuous development under a single company. Marathon operated Oregon Basin for ninety-two years, drilling the major reservoirs on ten to twenty acre spacing and, late in the field’s life, threading horizontal infill wells between the existing verticals. Production peaked above thirty-six thousand barrels of oil a day in 1968 and had eased to roughly forty-five hundred barrels a day by 2023. Merit, a private Texas company, acquired all interests in the field in 2016.
Oregon Basin is an eroded anticline fifteen miles long and six miles wide with about five thousand feet of structural relief, split into north and south domes and bounded by the Oregon Basin fault, a north-south structure with roughly twenty thousand feet of vertical displacement separating it from the central Bighorn Basin. Nine reservoir horizons produce across two petroleum systems: shallow, gas-prone Cretaceous and Triassic units including the Frontier, Cloverly, and Chugwater, and the deeper oil-prone Permian Phosphoria and Pennsylvanian Tensleep at three to four thousand feet, with the Madison beneath.
Oregon Basin is a mature waterflood at a scale that surprises people. The field circulates on the order of seven hundred thousand barrels of fluid per day, of which less than one percent is recoverable oil — a ratio that captures exactly what late-life secondary recovery looks like in a giant carbonate and sandstone field. Well counts published for the field include several hundred active producers alongside nearly two hundred water injectors. Horizontal infill drilling between existing vertical wells has been the most recent addition, aimed at parts of the reservoir the vertical pattern never drained.
Oregon Basin royalties are institutional-grade legacy interests: a century of continuous operation, a single operator for ninety-two of those years, and a decline curve so gentle that annual production changes are measured in percentage points. Value here turns on remaining flood life and on how a buyer models horizontal infill, not on a multiple of last year’s checks. Park County title frequently involves heirs several generations removed from the original lessor. We buy minerals and royalties in Park County and provide free written offers.
County-level well data, production charts, and selling guides for the counties this field spans:
It depends what you count. Drilling on the anticline found large shallow gas accumulations as early as 1912. Commercial oil came from the deeper Permian section under Ohio Oil, credited to 1924 in one account and to a major strike on February 1, 1927 in another.
Marathon operated the field for ninety-two years. Merit, a privately held Texas company, acquired all interests in Oregon Basin in 2016 and has run it since, continuing the waterflood and horizontal infill program.
Because it is a mature waterflood. Roughly seven hundred thousand barrels of fluid are cycled per day with less than one percent recoverable oil. High water cut is the normal condition of a field in this stage, not a sign that production is about to stop.