The Kiowa Formation as an Aquitard Between the Dakota Formation and the Cedar Hills Sandstone in Rooks, Ellis, and Russell Counties of North- Central Kansas

The Kiowa Formation is part of a transgressive sequence, deposited during Albian time, consisting of interbedded shales, siltstone, and sandstone. The formation crops out in south and north-central Kansas. In both of these geographically separated areas it is predominately thick-bedded, dense shale. A shale body within the Kiowa Formation in the western half of the study area, functions as an aquitard between the highly saline waters of the Cedar Hills Sandstone of the Permian System and the fresh and usable water of the Dakota Formation of the Cretaceous System. The Cedar Hills Sandstone has been used since the 1940s as a disposal zone for brine produced during oil production and is essential to the continued operation of marginal producing leases in north-central Kansas. The Kansas Corporation Commission is charged with the protection of all fresh and usable waters, including those in the Dakota Formation from oil field contamination. Earlier studies conducted by the Kansas Geological Survey indicated that the shale beds in the Kiowa Formation are neither laterally consistent nor thick enough to act as an aquitard between the fresh and usable water of the Dakota Formation and the Cedar Hills Sandstone. The findings of the Kansas Geological Survey’s study would indicate that there are some areas within the three countries where disposal into the Cedar Hills Sandstone would be problematic. Geophysical logs were used to determine the thickness, lateral extent, and nature of the uppermost shale layer in the Kiowa Formation. Isopach maps of this shale bed show that the thickest uppermost shales are located in the western one-fifth of the study area. Three-dimensional maps show the paleosurface of the Cedar Hills Sandstone and furnish concrete evidence for the difference in thickness of the aquitard in the western and eastern portions of this three county area