Controls on reservoir character in carbonate-chert strata, Mississippian (Osagean-Meramecian), southeast Kansas

Abstract

Osagean-Meramecian strata in southeast Kansas were investigated to determine structural, relative sea level, diagenetic, and depositional controls on stratigraphy, lithofacies distribution, and reservoir character. Lithofacies include echinoderm-rich bioclastic wacke-packstone, sponge-spicule-rich packstone, dolomitic bioclastic wackestone, argillaceous dolomite, tripolitic chert, and chert breccia. Four cores are used to construct a ten-mile long southwest-northeast cross section, which assists in interpretation of three genetic units. Paragenesis reveals that early and late dissolution enhance porosity in chert. Fluid inclusion microthermometry from megaquartz and baroque dolomite reveals variable but increasing homogenization temperatures (70˚C-160˚C) that increase in salinity through time. Data indicate that reservoir character is an interplay of depositional through late diagenetic events. The best reservoirs may be controlled by depositional setting that led to large amounts of chert and carbonate grains in grain support, alteration associated with subaerial exposure, and a hydrologic and structural setting that led to enhanced hydrothermal fluid flow for later dissolution.