sandstone petrography

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The study of and description of sandstones, including the mineral content. In matrix stimulation, only the mineral surfaces contacted by the stimulation fluid will be dissolved, so a petrographic study often helps anticipate the rocks response to fluid injection. Sandstone reservoirs are made of silicate grains such as quartz, feldspar, chert and mica, which are deposited as sand; secondary minerals may be deposited in the original pore spaces. Secondary quartz or carbonate minerals often bind sand grains together. Authigenic clays, mainly composed of silicon and aluminum, may also form in the pores. The reactivity of a given mineral depends on three factors: surface area, chemical composition and temperature. Clays have greater specific surface area compared with other matrix minerals, which makes them the most reactive components during well-stimulation operations.