Fracture Zones: Rare Oil Reservoirs in Central Kansas

Abstract

A 5-mi-long fracture zone in the Gorham oil field, Russell County, central Kansas, is defined by 30 oil wells. Fractured Topeka limestones (Pennsylvanian, Shawnee) at depths near 2,800 ft have produced an average of 217,000 bbl of oil per well. The discovery well, drilled with cable tools in 1935, flowed into a specially built 55,000-bbl tank which it filled in four days. A second giant oil well, still producing in 1991, has produced over 500,000 bbl of oil. The fracture zone was investigated because it underlies Interstate Highway 70 where subsidence has occurred since 1965. In the Rice County part of the extensive Chase-Silica oil field, a fracture zone was drilled in the early 1940s in the Lansing-Kansas City limestones (Pennsylvanian, Missourian), depth near 3,000 ft. The fracture zone was extended 3 mi southwest into Barton County in the 1950s by Sandy Holl's ruler geology, making a total length of 7 mi with 75 oil wells. Three of the most spectacular wells produced over 350,000 bbl of oil/well. A comparison is made with the upper Mississippi Valley lead-zinc mining district in Wisconsin where similar flat-lying carbonate rocks have high angle to vertical solution-slump fractures mineralized with lead and zinc oremore » with an average of 3.5 mines (fracture zones) per square mile in a 40-mi{sup 2} area. Why have we found so few fracture zones in the Arbuckle (Cambro-Ordovician), Kansas City, or Topeka carbonate rocks in the densely drilled central Kansas oil fields With current drilling methods, horizontally drilled holes would have a higher probability of drilling into oil-filled fracture zones in central Kansas.« less