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. |