Changes

===Deltaic sandstones===

===Deltaic sandstones===

Principal reservoirs are in delta-front sands.<ref name=North /> These deltaic sandstones form as deltas build out over the deeper-water deposits, and are common in post-organic sedimentary basins from Devonian to Recent for example Clinton sandstone in Ohio (Silurian), Jurassic Brent deltaic sandstones in North Sea. Vertical stacking in deltaic sandstones is common, giving rise to multi- pay zones. This is mainly due to individual delta lobes typically building out over and beside earlier lobes as subsidence proceeds and basin fills. Deltaic sandstones typically have a coarsening upward sequence, with individual sand bodies often elongate, lobate,or parallel to the paleo- shoreline but discontinuous along strike. During diagenesis; deltaic sandstones, although coarser, may often be cemented by early-formed silica and are commonly less productive. The cementation may block migration of hydrocarbons from the deeper sources into beds such as onshore fluvial deposits higher up in the prograding delta-fill sequence.

Principal reservoirs are in delta-front sands.<ref name=North /> These deltaic sandstones form as deltas build out over the deeper-water deposits, and are common in post-organic sedimentary basins from Devonian to Recent for example Clinton sandstone in Ohio (Silurian), Jurassic Brent deltaic sandstones in North Sea. Vertical stacking in deltaic sandstones is common, giving rise to multi- pay zones. This is mainly due to individual delta lobes typically building out over and beside earlier lobes as subsidence proceeds and basin fills. Deltaic sandstones typically have a coarsening upward sequence, with individual sand bodies often elongate, lobate,or parallel to the paleo- shoreline but discontinuous along strike. During [[diagenesis]]; deltaic sandstones, although coarser, may often be cemented by early-formed silica and are commonly less productive. The cementation may block migration of hydrocarbons from the deeper sources into beds such as onshore fluvial deposits higher up in the prograding delta-fill sequence.

[[File:Sandstone-Fig-6.png|thumb|300px|Figure 6: Farson Sandstone Member deltaic sandstone in northern Green River Basin with associated clinoforms dipping to the left (southwest).(modified from North<ref name=North />).]]

[[File:Sandstone-Fig-6.png|thumb|300px|Figure 6: Farson Sandstone Member deltaic sandstone in northern Green River Basin with associated clinoforms dipping to the left (southwest).(modified from North<ref name=North />).]]

====Early diagenesis====

====Early diagenesis====

Early diagenesis was controlled by the depositional facies and detrital composition. Early diagenesis mainly includes mechanical compaction, early diagenetic carbonate cementation, dissolution of the detrital fragments, and the mechanical infiltration of grain coating smectitic clay, and precipitation of kaolinite. Mechanical compaction reduced porosity and permeability through increased grain packing and the bending and rupturing of mica and plastic [[deformation]] of ductile rock fragments and mud intraclasts. Interaction of meteoric water with sandstones resulted in the dissolution of detrital fragments (mainly feldspars) and the precipitation of kaolinite and smectite.  

Early [[diagenesis]] was controlled by the depositional facies and detrital composition. Early diagenesis mainly includes mechanical compaction, early diagenetic carbonate cementation, dissolution of the detrital fragments, and the mechanical infiltration of grain coating smectitic clay, and precipitation of kaolinite. Mechanical compaction reduced porosity and permeability through increased grain packing and the bending and rupturing of mica and plastic [[deformation]] of ductile rock fragments and mud intraclasts. Interaction of meteoric water with sandstones resulted in the dissolution of detrital fragments (mainly feldspars) and the precipitation of kaolinite and smectite.  

====Late diagenesis====

====Late diagenesis====