A STRATIGRAPHIC DESCRIPTION OF CAMBRIAN-PENNSYLVANIAN DEPOSITS USING GEOPHYSICAL WELL LOGS – WELL CUTTING ANALYSIS

Drill cuttings were obtained from an oil producing well logged between the depths of 3150’ MD to 3875’ MD. The well was drilled as a Wildcat well in Section 28, Township 12S, Range 19W, in Ellis County, near the city of Hays, KS. The targeted producing unit was the Lansing Kansas City Group, mostly composed of carbonates and interbedded shales and silts. We analyzed the 725 feet of cuttings and associated well logs for this well in this study, to characterize the sedimentary, stratigraphic, and paleo-depositional characteristics of the interval. Petrophysical properties including porosity, permeability, and some mineralogical characteristics were also analyzed for the interval. Total porosity was computed from the density and neutron porosity logs, and porosity types were determined from well cutting analysis. Permeability and lithological properties were described using micro resistivity log, gamma ray analysis, lithology cross plots, bulk density curves, and cuttings. Results were used to interpret the environment of deposition and the paleo environmental conditions for the stratigraphic sequence. A disconformity identified between the Marmaton Group and underlying Arbuckle Group suggest sub aerial erosion of absent rock layers. The porosity ranges from less than 5% to 26% within the interval. The highest porosity values correlate with intervals with shaly silt units. These are interpreted to likely be due to shale effects and/or fracturing that may have resulted from tectonic forces during the Central Kansas Uplift. High porosity in silty shale units show low permeability with some exceptions. High gamma ray readings are associated with relatively thin intervals, including the Heebner Shale unit, that are interbedded in carbonate layers interpreted to indicate 5^th order cyclicity in the depositional sequence. Limestones and carbonate units mostly show secondary porosity from fracturing, dissolution, and intracrystalline porosity. Cutting observations show high amounts of pyritic and magnetic minerals associated with hydrocarbon zones.