Mineralogical, Geochemical, and Isotopic Evidence of Diagenetic Alteration, Attributable to Hydrocarbon Migration, Raven Creek and Reel Fields, Wyoming

Hydrocarbon migration exerted a limited influence on diagenetic mineralization in the upper Minnelusa sandstones of the Raven Creek and Reel oil fields in northeastern Wyoming. Alteration of sandstones by hydrogen sulfide gas associated with petroleum resulted in the formation of disseminated euhedral pyrite crystals. Cernentation by anhydrite, dolomite, and authigenic clays reduced reservoir potential. Secondary porosity resulted from the dissolution of anhydrite cement. The results of this study were obtained through detailed examination and description of cores, petrographic studies, scanning electron microscopy, sulfur, carbon, and oxygen isotopic analysis, x-ray diffraction, and formation water analysis.Geolog