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===Framework grains===

===Framework grains===

Framework grain compositions commonly influence the diagenetic history and reservoir quality of a sandstone by controlling compaction and chemical interaction with pore fluids. Sandstones that contain ductile lithic fragments such as shale or slate compact at shallower depths than sandstones composed mostly of brittle grains such as quartz and feldspar. Therefore, the preservation of primary intergranular porosity may be dependent upon original framework grain composition and the compactional history of the sandstone.

Framework grain compositions commonly influence the diagenetic history and reservoir quality of a sandstone by controlling compaction and chemical interaction with pore fluids. Sandstones that contain [[Ductility|ductile]] lithic fragments such as shale or slate compact at shallower depths than sandstones composed mostly of brittle grains such as quartz and feldspar. Therefore, the preservation of primary intergranular porosity may be dependent upon original framework grain composition and the compactional history of the sandstone.

Chemical interaction between framework grains and pore fluids can either reduce or enhance porosity. Certain grains provide preferential nucleation sites for common cements. For example, the presence or absence of nucleation sites on detrital quartz grains influences the volume of quartz overgrowths precipitated and therefore the amount of porosity preserved in some sandstones. Chemical interaction of framework grains with some pore fluids can enhance porosity by grain dissolution. For example, a sandstone facies containing chemically unstable grains (commonly feldspar or various lithic fragments) might undergo porosity enhancement by dissolution of those grains. In the same formation, less porosity enhancement would occur in a quartz-rich facies containing fewer chemically unstable grains.

Chemical interaction between framework grains and pore fluids can either reduce or enhance porosity. Certain grains provide preferential nucleation sites for common cements. For example, the presence or absence of nucleation sites on detrital quartz grains influences the volume of quartz overgrowths precipitated and therefore the amount of porosity preserved in some sandstones. Chemical interaction of framework grains with some pore fluids can enhance porosity by grain dissolution. For example, a sandstone facies containing chemically unstable grains (commonly feldspar or various lithic fragments) might undergo porosity enhancement by dissolution of those grains. In the same formation, less porosity enhancement would occur in a quartz-rich facies containing fewer chemically unstable grains.