DIAGENESIS AND DISTRIBUTION OF DIAGENETIC FACIES IN THE MISSISSIPPIAN OF SOUTH CENTRAL KANSAS

The Mississippian system in south central Kansas, a hydrocarbon prolific system of rocks, has very complex textures and petrophysical characteristics that resulted from passage through different diagenetic environments. Understanding how these textures formed is important because producing hydrocarbon units are tied to a specific set of diagenetic textures (e.g. neomorphic alterations, fracture development, generation of porosity and permeability, etc.) that gives it a favorable reservoir characteristic. Although several studies have been published with interpretations of diagenesis in the Mississippian, only a few of them present geochemical data that supports the interpretations of diagenetic environments. This is critical because similar textures and mineral assemblages can form by various diagenetic processes. Also, new petrophysical and core data from recent industry work provides a new opportunity to study diagenetic facies in the Mississippian. This research seeks to determine the origin and nature of diagenetic facies and understand their stratigraphic distribution in the Mississippian of south central Kansas.

The petrography of five cores is being interpreted to determine the different diagenetic facies. Diagenetic facies are defined by differing preservation of original rock textures. Although chertification is a pervasive process in the Mississippian, core interpretations show that some lithologies are less susceptible to chertification. Transmitted light microscopy, cathodoluminescence and scanning electron microscopy are used for thin section descriptions. Diagenetic interpretations will be supported with geochemical analysis (stable isotopes; Ca, Mg, Sr, Fe and Mn concentrations; TOC) and mineralogy and crystallinity via x-ray diffraction to determine the diagenetic environment at which minerals are precipitated and the source of the diagenetic fluids that altered the rock. The distribution of diagenetic facies will be determined by developing 3D static models from correlation of core descriptions and petrophysical interpretations of wire line logs. The completion of this research will enhance interpretations of stratigraphy, reservoir characteristics and paleotopographic reconstructions implied from diagenetic environments in the Mississippian system.