Changes

==Effect of authigenic clays==

==Effect of authigenic clays==

[[file:predicting-reservoir-system-quality-and-performance_fig9-61.png|300px|thumb|{{figure number|2}}. Copyright: F. K. North;<ref name=North_1985>North, F. K., 1985, Petroleum Geology: London, Allen & Unwin, 607 p.</ref> courtesy Allen & Unwin.]]

[[file:predicting-reservoir-system-quality-and-performance_fig9-61.png|300px|thumb|{{figure number|2}}Comparison of porosity-permeability relationships for kaolinite-, chlorite-, and illite-cemented sandstones. Copyright: F. K. North;<ref name=North_1985>North, F. K., 1985, Petroleum Geology: London, Allen & Unwin, 607 p.</ref> courtesy Allen & Unwin.]]

Pore-bridging clays, like [[illite]], decrease porosity slightly but can destroy sandstone [[permeability]]. Discrete particle clay, like [[kaolinite]], lowers [[porosity]] and permeability only slightly. [[:file:predicting-reservoir-system-quality-and-performance_fig9-61.png|Figure 2]] compares porosity-permeability relationships for kaolinite-, [[chlorite]]-, and illite-cemented sandstones. Note there is no significant change in porosities, but permeabilities range over four orders of magnitude.

Pore-bridging clays, like [[illite]], decrease porosity slightly but can destroy sandstone [[permeability]]. Discrete particle clay, like [[kaolinite]], lowers [[porosity]] and permeability only slightly. [[:file:predicting-reservoir-system-quality-and-performance_fig9-61.png|Figure 2]] compares porosity-permeability relationships for kaolinite-, [[chlorite]]-, and illite-cemented sandstones. Note there is no significant change in porosities, but permeabilities range over four orders of magnitude.