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  | isbn    = 0-89181-602-X

  | isbn    = 0-89181-602-X

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Diagenesis alters the original pore type and geometry of a sandstone and therefore controls its ultimate [[porosity]] and [[permeability]]. Early diagenetic patterns correlate with environment of deposition and sediment composition. Later diagenetic patterns cross facies boundaries and depend on regional fluid [[migration]] patterns (Stonecipher and May, 1992). Effectively predicting sandstone quality depends on predicting diagenetic history as a product of depositional environments, sediment composition, and fluid migration patterns.

[[Diagenesis]] alters the original pore type and geometry of a sandstone and therefore controls its ultimate [[porosity]] and [[permeability]]. Early diagenetic patterns correlate with environment of deposition and sediment composition. Later diagenetic patterns cross facies boundaries and depend on regional fluid [[migration]] patterns (Stonecipher and May, 1992). Effectively predicting sandstone quality depends on predicting diagenetic history as a product of depositional environments, sediment composition, and fluid migration patterns.

==Diagenetic processes==

==Diagenetic processes==

[[file:predicting-reservoir-system-quality-and-performance_fig9-46.png|300px|thumb|{{figure number|1}}Porosity–depth plot for sandstones from two wells with different geothermal gradients. Copyright: Wilson;<ref name=ch09r66 /> courtesy SEPM.]]

[[file:predicting-reservoir-system-quality-and-performance_fig9-46.png|300px|thumb|{{figure number|1}}Porosity–depth plot for sandstones from two wells with different geothermal gradients. Copyright: Wilson;<ref name=ch09r66 /> courtesy SEPM.]]

Depending on geothermal gradient, the effect of temperature on diagenesis can be significant. Many diagenetic reaction rates double with each [[temperature::10&deg;C]] increase (1000 times greater with each [[temperature::100&deg;C]]).<ref name=ch09r66>Wilson, M., D., 1994a, Non-compositional controls on diagenetic processes, in Wilson, M., D., ed., [[Reservoir quality]] Assessment and Prediction in Clastic Rocks: SEPM Short Course 30, p. 183–208. Discusses the effect that variables such as temperature and pressure have on diagenesis of sandstones. A good reference for predicting sandstone reservoir system quality.</ref> Increasing temperatures increase the solubility of many different minerals, so pore waters become saturated with more ionic species. Either (1) porosity–depth plots of sandstones of the target sandstone that are near the prospect area or (2) computer models that incorporate geothermal gradient are probably best for porosity predictions.

Depending on geothermal gradient, the effect of temperature on [[diagenesis]] can be significant. Many diagenetic reaction rates double with each [[temperature::10&deg;C]] increase (1000 times greater with each [[temperature::100&deg;C]]).<ref name=ch09r66>Wilson, M., D., 1994a, Non-compositional controls on diagenetic processes, in Wilson, M., D., ed., [[Reservoir quality]] Assessment and Prediction in Clastic Rocks: SEPM Short Course 30, p. 183–208. Discusses the effect that variables such as temperature and pressure have on diagenesis of sandstones. A good reference for predicting sandstone reservoir system quality.</ref> Increasing temperatures increase the solubility of many different minerals, so pore waters become saturated with more ionic species. Either (1) porosity–depth plots of sandstones of the target sandstone that are near the prospect area or (2) computer models that incorporate geothermal gradient are probably best for porosity predictions.

[[:file:predicting-reservoir-system-quality-and-performance_fig9-46.png|Figure 1]] is a porosity–depth plot for sandstones from two wells with different geothermal gradients. The well with the greater geothermal gradient has correspondingly lower porosities than the well with lower geothermal gradient. At a depth of [[depth::7000 ft]], there is a 10% porosity difference in the trend lines.

[[:file:predicting-reservoir-system-quality-and-performance_fig9-46.png|Figure 1]] is a porosity–depth plot for sandstones from two wells with different geothermal gradients. The well with the greater geothermal gradient has correspondingly lower porosities than the well with lower geothermal gradient. At a depth of [[depth::7000 ft]], there is a 10% porosity difference in the trend lines.