Stratigraphy and Structure
Conditions along an east-west line through the southern part of Elk County are shown on Figure 8. Major rock units are differentiated.
Elk County lies on the Prairie Plains monocline, which constitutes the western flank of the Ozark uplift and involves extensive regions in western Missouri, eastern Kansas, and northeastern Oklahoma, where the strata dip at bow angle generally westward. Elk County also lies on the western flank of what is commonly known as the Cherokee basin.
The subsurface rocks of Elk County reflect a history of oscillation, repeated emergence being shown by numerous unconformities separating Paleozoic formations. Erosion seems to have been widespread from late Ordovician to early Mississippian time, from the close of Mississippian to early Pennsylvanian time, and since Permian time.
The most striking local feature in Elk County is the Longton ridge, which extends into Chautauqua County to the south and is about 25 miles long. The highest part of the ridge is found in sec. 33, T. 31 S., R. 12 E.
Generally, in the surface strata there is only slight evidence of various Mississippian folds. The folds of the surface strata seem to be reflections of subsurface structural features, but not all surface folds are located over or near subsurface structures.
On the Prairie Plains monocline the prevailing attitude of the strata is locally modified by departures from the westward dip. The differences range from steepening to reversal. Several of the more important oil fields have been developed on the structural features formed by these local variations upon the Prairie Plains monocline.
Thickness of the Council Grove group in Elk County is about 125 feet. The group consists principally of limestones and shales. Rocks of the Admire group consist of shales, thin beds of limestones, and some coal. They have a total thickness of about 90 feet in the county.
The Wabaunsee group consists of shale, sandstone, and thin beds of limestone. In Elk County it has a total thickness of about 300 feet. The Shawnee group here is about 425 feet thick, and it is characterized by thick limestone beds and distinctive cyclic sedimentation. The Douglas group has a total thickness of about 300 feet and consists chiefly of clastic rocks--shale and sandstone. The thickness of Douglas rocks differs in different parts of the county, as shown by Figure 8. The Lansing group in Elk County is about 225 feet thick. It consists principally of two limestones separated by a thin shale. The Kansas City group, consisting chiefly of limestones, is about 440 feet thick in the county. The underlying Pleasanton rocks consist chiefly of shale and sandy shale and are about 60 feet thick. Marinaton rocks, consisting of alternating beds of shale and limestone but including some sandstone and coal beds, are 250 feet thick. The Cherokee group is about 300 feet thick and consists mostly of shales but includes some thin limestones and sandstones.
Pre-Pennsylvanian rocks are in unconformable contact with the Cherokee group throughout Elk County. Undifferentiated Mississippian limestones in Elk County range from 150 to 300 feet in thickness (Lee, 1939, plate 1). The formations are the "Warsaw", Keokuk, Burlington, Reed Springs, and St. Joe limestones and Northview-Compton (undivided shale and limestone) (Lee, 1940). The Chattanooga shale in Elk County is about 50 feet thick.
The Cambro-Ordovician rocks in Elk County have not been completely subdivided. The Cotter dolomite unconformably underlying the Chattanooga shale is the youngest Ordovician rock in Elk County. The Cambro-Ordovician rocks range from about 750 to 1,165 feet in thickness and are principally cherty dolomites and limestones.
Data on oil and gas wells in Elk County were collected in the field during the summer of 1951 by Frank Moffitt. Compilation of information from the reference file of drillers logs and allied oil and gas information in the Oil and Gas Division of the State Geological Survey was completed by R. Kenneth Smith, Edwin D. Goebel, William R. Atkinson, and P. Lorenz Hilpman. Considerable data on Elk County wells were given to the authors by the following individuals and agencies: H.E. Redmon, C.W. Studt, E.P. Trout, Kansas Well Log Bureau, and the Conservation Division of the Kansas Corporation Commission.
The Geological Survey has no logs for many of the wells located on the oil and gas field map, Plate 2. Wherever substantial evidence existed that a well had been drilled, a well symbol has been put on the map, even though exact locations, records of stratigraphic zones, or drillers logs of many of the holes are not available. Probably a few of the wells drilled in Elk County are not represented on the map, but there has been reasonable diligence in the compilation.
Exploration and Production
Oil was first discovered in Elk County near Longton in 1902. The southwestern part of the county is the principal oil-producing area. Elk County's first reported gas well is the one completed in 1901 near Elk Falls. Gas production has been relatively important since about 1921, and the southern half of the country is the principal gas-producing area.
Producing formations--Oil and gas are produced from three sandstones in the Vilas shale in the Lansing group, which is Pennsylvanian in age (Jewett, 1954, p. 203). The uppermost of these sandstones is known as the "Bush-Denton" (or "Ferguson"), the middle is the "Longton" (or "Webb"), and the lowermost is the "Encill" sand. Production is also known from the "Stalnaker" in the Lansing group. The "Layton" sandstone in the upper part of the Kansas City group yields oil and gas. Oil and gas in the Marmaton group come from the "Old Red" or "Wayside" sand in the Nowata shale, the "Weiser" sand in the Bandera shale, the "Peru" sand in the Labette shale, and the Little Osage shale of the Fort Scott formation. Oil and gas sands of the Cherokee group include the "Bartlesville" about 180 feet below the top and the "Burgess" near the base. The productive part of the Mississippian rocks is a weathered zone in the upper part. The Cotter dolomite of the Arbuckle group, Ordovician, produces oil from a porous zone in the upper part. Goebel and others (1957, page 170) report the depths to the tops of the various producing rocks in Elk County.
The peak year for oil production in Elk County was 1927, when more than 895,000 barrels was reported. Production during 1955 amounted to more than 304,000 barrels from approximately 281 wells. Cumulative reported oil production from the county amounts to approximately 14.5 million barrels, as of 1956.
The earliest secondary recovery project in Elk County was in the New Albany field. In 1927 air under pressure was applied to the oil reservoir. The oil-producing formation in the field was the "Wayside" sandstone encountered at a depth of about 560 feet. Air under pressure was applied until 1937; natural gas was then substituted for air as the driving medium (Grandone, 1944).
The Longton field is the only other major field in Elk County to which secondary recovery methods have been applied. Commencing in 1947, fresh water from shallow wells was injected into the "Longton" shallow sand at a depth of 570 feet. On several other smaller fields pilot water-flood studies have been made. As of January 1, 1956, no secondary recovery operations were reported in the county.
The calculated water-flood reserves as of January 1, 1948, were more than 1,860,000 barrels of oil (Sweeney, 1949, p. 11).
Kansas Geological Survey, Geology
Web version July 2002. Original publication date July 1958.
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