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Eldorado Oil and Gas Field

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The Eldorado district, as treated in this report, is an irregularly rectangular area embracing about 137 square miles in Butler county, Kansas (see plate III), and includes not only the main Eldorado oil-field development and its two subsidiaries on the Wilson and Robinson domes to the north, but also the smaller Smock and Sluss pools lying to the southeast. (These subdivisions are differentiated on plate I.) It is traversed from north to south by the Florence branch of the Atchison, Topeka & Santa Fe, and from east to west by the Missouri Pacific railway. The Missouri Pacific also has a branch line running northwest from Eldorado to Newton.

Eldorado is the county seat of Butler county and its principal town. Previous to the development of the oil field Eldorado was a town typical of an agricultural district and possessed a population of about 3,000. With the development of the oil field the town boomed, and within one and a half years grew to a city with a population of 10,000 to 15,000. The streets are well paved and the town has tried to keep its civic improvements abreast of its growth. Towanda lies six miles west of Eldorado on the Missouri Pacific, and is a thriving small town of about 1,000 inhabitants, also enjoying the oil boom. Oil Hill, one and one-half miles northwest of Eldorado, is a busy oil-field settlement built by the Empire Gas and Fuel Company for its employees. Vanora and Ramsey are siding stations on the Atchison, Topeka & Santa Fe.

The public highways are clay roads which suffer the same vicissitudes as clay roads in other regions, only more so, because of the heavy oil-field traffic. The established roads follow the land lines, with but small modifications caused by grading difficulties presented by local surface features. It is believed that every permanent road or street which was established by the spring of 1918 is correctly shown on the map (plate I). Temporary field roads and short cuts are not represented.


The Eldorado district ranges in altitude from 1,225 to 1,450 feet above mean sea level, and lies principally on the prairie upland between the Walnut river, which crosses its southeastern part, and Whitewater river, which forms part of its western boundary. Since the district is located thus on the divide, it may be noted that the topography conforms rather closely to the anticlinal structure of the rocks. The ground surface is diverse in character; in some places it is rolling, in other places marked by long, gentle slopes (dip slopes), and in still other places is broken by low escarpments. The rolling portion is on the truncated axis of the anticline, while the long dip slopes developed on the top of the Fort Riley limestone lie principally on the west flank of the anticline and in the Smock pool and the Sluss pool localities. The principal escarpment, which starts on the northeast side and runs around the field to the north, northwest, west and southwest, is caused by the Winfield limestone. The Herington (?) and Towanda limestones also form, here and there, low and less pronounced escarpments. If the Fort Riley, and Florence limestones were so exposed that a soft formation outcropped below them, they would also form an escarpment, but in the Eldorado district they are the lowermost rocks present, and therefore have no opportunity to form escarpments. However, where dissected by streams they form rock-walled valleys, as along Turkey creek and several other tributaries of Walnut river. The major valleys have pronounced alluvial plains, in which the streams have developed meandering courses. The alluvial flats range in general between ten and forty times the width of the streams.

The width of the alluvial plains varies quite notably, and, contrary to the general rule, the narrower constrictions are downstream and the wide portions upstream. In the vicinity of Eldorado the plain of the Walnut river is nearly a mile wide, and at two points—four and seven miles, respectively, downstream—it is less than one-fourth mile wide. Similarly the plain of the West branch is in general between one-fourth and three-eighths mile wide, but in the vicinity of its mouth, at the town of Eldorado, it narrows to about one-sixteenth of a mile in width. No satisfactory explanation of these constrictions can be offered. There is no apparent greater resistance to erosion of the bedrock at these points, and a recent local differential deformation at these places can hardly be called into account. The only factor which can be suggested is that at these places there was a possible greater underground drainage, which lessened the eroding power of the surface streams and thereby prevented the development of as wide a valley as at other points.


The Walnut and Whitewater rivers are intermittent streams, flowing only during rainy periods. They both, however, have a considerable subsurface flow, especially the main Walnut river and in its west branch, in which the ground water is sufficiently high to maintain large ponds of water in the deeper depressions throughout the year.

Throughout much of the area, and outside of the stream valleys where the Fort Riley limestone and Florence flint form the surface rock, there is a great deal of subsurface drainage, and consequently surface drainage in such places has been eliminated. These places are usually marked by the presence of a great many sink holes. The subsurface drainage is probably the source of the ponded water in the deeper depressions of Walnut river. It also is the factor controlling most of the large springs, of which there are several in the river valleys. One of the peculiar results of this subsurface drainage is that many shallow-water wells and several of the springs which obtain their water from these rocks have turned to salt-water wells and salt-water springs since the development of the oil field higher on the anticline, the salt water being the waste material from the oil wells which is permitted to enter the underground drainage. At least one such well, located in Towanda, not only turned to salt water, but was reported in the daily press to have later turned into an oil well, the oil being waste material which escaped and entered the subsurface drainage in the Fort Riley limestone and Florence flint.

Water Supply

Previous to the discovery of the oil field the municipal water supply of Eldorado was obtained from the natural and artificial ponding of the Walnut river within the confines of the city. Most of the drinking and much of the domestic supply, however, was obtained from shallow driven wells which tapped the water-bearing Fort Riley limestone and Florence flint. With the development of the oil field and its attendant influx of people, not only was the demand for water for boiler and domestic use increased, but the waste salt water obtained from the oil wells entered the underground drainage from which much of the domestic and most of the drinking supply was obtained, and polluted it. One interesting feature with respect to this pollution is to be noted in the position of Eldorado with respect to the rock structure and the location of Walnut river. To the east of Eldorado the underground drainage in the Fort Riley limestone and Florence flint is westward, but Walnut river has cut through these rocks, except to the northeast, and hence little or none of the water in the Fort Riley and Florence limestones in Eldorado is obtained from the drainage to the east, but rather from the oil-field region on the anticline to the west. The supply of drinking water was alleviated by boiling and by importing bottled water, and the increased demand for oil-field developments was in part supplied by making use of the naturally ponded water for many miles along the stream courses. Many times even this ponded water was inadequate, and drilling operations were greatly curtailed and at times almost suspended. To relieve their own deficiency of water the Empire Gas and Fuel Company made use of their twelve-inch gas pipe line to Wichita by pumping through it water obtained from Arkansas river near Valley Center, thirty-five miles away.

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Kansas Geological Survey, Geology
Placed on web July 28, 2017; originally published 1921.
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