Oklahoma City Oil Field

The Oklahoma City Field is one of the giant oil fields of the world, producing more than 735 million barrels of oil and more than 2 trillion cubic feet of gas from 26 producing zones through 1969, with ultimate recovery estimated at 770 million barrels. Geologists recognized a structure favorable for oil accumulation near Oklahoma City in 1917, but more than 10 years passed before the Indian Territory Illuminating Oil Company, later Cities Service, drilled the discovery well. In December 1928, the Itio No. 1 Oklahoma City blew in while drilling cement at 6,402 feet, and its initial gauge from the Arbuckle dolomite was 6,565 barrels of oil per day. The field’s reservoirs lie in porous sedimentary rock layers formed over eons as sediments accumulated in seas that once covered this part of Oklahoma. Deposition on the Precambrian granite basement began about 600 million years ago and continued, with a few interruptions, for nearly 300 million years, when a mountain range formed through upward arching and faulting of the granite. Growth of the range deformed and faulted the overlying rocks, raising those on the west side of the fault above those on the east and lifting the rock layers above sea level, after which the exposed rocks were eroded to a relatively flat unconformity surface. About 320 million years ago this surface showed the area’s rock distribution before the sea returned and buried it beneath several thousand feet of Pennsylvanian and Permian sediments. Later upward movement of the buried mountain range and renewed fault movement arched and disrupted these younger layers, though less than the older rocks below the unconformity, and together these events created especially favorable conditions for trapping oil and gas. A pumping well nearby was directionally drilled to produce oil from directly beneath the Capitol building.

Oklahoma City, Oklahoma · United States