The Silurian "Clinton" sandstone of the Appalachian basin has long been a favored target for oil and gas exploration. Though most wells are of modest production, success ratios have been excellent. Porosities generally range from nil to as much as 10%, and permeabilities commonly range from less than 0.1 md to 1.0 md and more.

Detailed study of three cores from northeast Ohio by visual, petrographic, X-ray diffraction, cathodoluminescence, scanning electron microscopy, and electron microprobe analysis, shows that present porosity is essentially secondary in nature, and intergranular porosity shows significant modification and reduction by authigenic minerals. Pressure solution is suggested as moderate and fracture porosity is limited and, where present, is commonly healed by quartz and calcite overgrowths. Porosity appears to have developed and modified through successive stages. It appears to have progressed initially from dissolution of early calcite cement and local detrital clay matrix. Authigenic potassium feldspar rims formed on detrital potassium feldspar cores. Subsequently, ubiquitous quartz overgr wths, authigenic iron chlorite, and illite reduced porosity. Dissolution of the authigenic rims and detrital potassium feldspar cores also occurred. Some late-stage(?) calcite and phyllosilicate cements, and differential patches of anhydrite cement, further reduced porosity.

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