Changes

===Matrix===

===Matrix===

Clay minerals commonly occur as both matrix and cement in reservoir sandstones.<ref name=pt05r71>Hagoort, J., 1984, Measurement of [[relative permeability]] for computer modeling/reservoir simulation: Oil and Gas Journal, Feb. 20, p. 62–68.</ref> Detrital matrix can be introduced into sand during or immediately following sedimentation by depositional processes, infiltration, and bioturbation. It can occur as grain coatings, dispersed matrix, laminae, or discrete grains. Authigenic clay cements commonly precipitate as grain coatings, pore fillings, and grain replacements. Virtually any clay mineral can occur in any of these modes, with kaolinite, chlorite, smectite, mixed layer illite-smectite, and illite occurring as common constituents of reservoir sandstones.

Clay minerals commonly occur as both matrix and cement in reservoir sandstones.<ref name=pt05r71>Hagoort, J., 1984, Measurement of relative permeability for computer modeling/reservoir simulation: Oil and Gas Journal, Feb. 20, p. 62–68.</ref> Detrital matrix can be introduced into sand during or immediately following sedimentation by depositional processes, infiltration, and bioturbation. It can occur as grain coatings, dispersed matrix, laminae, or discrete grains. Authigenic clay cements commonly precipitate as grain coatings, pore fillings, and grain replacements. Virtually any clay mineral can occur in any of these modes, with kaolinite, chlorite, smectite, mixed layer illite-smectite, and illite occurring as common constituents of reservoir sandstones.

The presence of clay minerals of any origin has both direct and indirect effects on reservoir quality. Directly, clay minerals commonly result in lowered permeability because they constrict pore throats and promote higher irreducible water saturation. Indirectly, clay minerals commonly influence diagenetic processes that impact reservoir quality. For example, clay grain coatings in some sandstones have inhibited the nucleation of quartz overgrowths and thereby contributed to porosity preservation. However, clay grain coatings in other sandstones have promoted intergranular pressure solution and have thereby contributed to porosity destruction.

The presence of clay minerals of any origin has both direct and indirect effects on reservoir quality. Directly, clay minerals commonly result in lowered permeability because they constrict pore throats and promote higher irreducible water saturation. Indirectly, clay minerals commonly influence diagenetic processes that impact reservoir quality. For example, clay grain coatings in some sandstones have inhibited the nucleation of quartz overgrowths and thereby contributed to porosity preservation. However, clay grain coatings in other sandstones have promoted intergranular pressure solution and have thereby contributed to porosity destruction.