The Aylesworth oil field in eastern Marshall County and western Bryan County, Oklahoma, is located south of the Arbuckle Mountains, approximately 30 miles east of Ardmore. The structure is a northwest-southeast trending, normally faulted anticline about 10 miles long and as much as ¾ mile wide, with about 1,600 feet of closure proven by drilling. It is of late Pennsylvanian, probably Virgilian age.
Cretaceous rocks of the Comanchean series, found at the surface and to a depth of approximately 650 feet, rest unconformably on Pennsylvanian rocks of the Springeran Series and do not accurately reflect the deeper structure. Pre-Pennsylvanian beds are essentially parallel and, except where missing because of faulting, are present over the entire structure.
Production is almost entirely from the 2d and 3d Bromide sands of the Simpson group of Ordovician age. The oil trap is structural rather than stratigraphic, although stratigraphic variations in thickness, and variations in the degree of cementation of the producing sands may determine the size of individual wells. The reservoir has a solution-gas/gas-expansion drive. There is no effective water drive. Cumulative oil production as of October 1, 1953, was 4,636,833 barrels.
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Because of the excellent pioneer work done by Eldridge in mapping occurrences of oil seeps, asphaltic sandstones, and showings in water wells, in southern Oklahoma, and by Taff and Gould on the structure and stratigraphy of the Arbuckle and Wichita mountain areas, there was ample evidence of the presence of petroleum to lure the prospector when Oklahoma and Indian Territories were opened for leasing just after the turn of the century.
About one-fourth the area covered by the oil fields of southern Oklahoma has Pennsylvanian rocks on the surface. This portion has been very well described in the literature. The remaining three-fourths is covered with Permian rocks, the oldest being the upper Pontotoc massive cherty brown sandstones. These are overlain by the Wichita formation consisting of 700 feet of alternating gray sandstones and interbedded purplish-maroon shales and barite beds, and bone beds with the remains of Permian reptiles, sharks, and amphibians. Next above is the basal asphaltic gray sandstone of the Garber formation resting unconformably on whatever may be below it, and carrying the huge “flying saucer” concretions; above which is the remaining 300-foot section of maroon conglomeratic sandstones and shales. The Garber crops out around and over more oil fields than any other formation in southern Oklahoma—like the Mesaverde of the Rockies. Next above is the 400-foot greenish-gray sandy shale section of the Hennessey, followed in turn by the 200-foot maroon sandstone section of the Duncan, the 4oo-foot “purple” shale of the Chickasha, and the 400-foot Whitehorse group. At the top are the Cloud Chief gypsum and the Quartermaster formation.
The conspicuous surface folds along the old lines of weakness prove that the folding at the close of Permian time and again after Cretaceous time was pronounced, supporting ideas of Bullard (1928) and Freie (1930).
From the discovery of the Granite field in 1901, Wheeler in 1905, Cruce in 1906, through Loco and Healdton in 1913, Fox in 1915, Wildcat Jim in 1916, and Velma in 1917, to Robberson in 1920, Sholom Alechem in 1923, and Apache in 1941, most of the fields of southern Oklahoma have been discovered by adhering strictly to common sense rules of oil finding by testing areas of favorable structure close to oil seeps, showings of oil and gas, and asphaltic sandstone occurrences.