Changes

The upward-shoaling model is based on a depositional model of sediment [[Aggradation|aggrading]] to sea level. As the water shallows, the energy conditions increase, resulting in a vertically stacked sequence from [[mudstone]]s and [[wackestone]]s at the bottom to [[packstone]]s and [[grainstone]]s at the top ([[:file:carbonate-reservoir-models-facies-diagenesis-and-flow-characterization_fig3.png|Figure 3]]).

The upward-shoaling model is based on a depositional model of sediment [[Aggradation|aggrading]] to sea level. As the water shallows, the energy conditions increase, resulting in a vertically stacked sequence from [[mudstone]]s and [[wackestone]]s at the bottom to [[packstone]]s and [[grainstone]]s at the top ([[:file:carbonate-reservoir-models-facies-diagenesis-and-flow-characterization_fig3.png|Figure 3]]).

[[Postaccumulation cementation|Cementation]] and [[Reservoir quality#Compaction|compaction]] occur with burial, reducing the reservoir quality of the [[Mud-supported carbonate|mud-supported]] mudstones and wackestones more than the [[Grain-supported carbonate|grain-supported]] packestones and grainstones. The result is a vertical sequence of lower [[porosity]] and [[permeability]] mud-supported rocks at the base and higher porosity and permeability grain-supported rocks at the top. Consequently, the best quality [[Flow units for reservoir characterization|flow unit]] occurs at the top of the sequence . The permeable units are confined to the grainstone [[bar]]s.

[[Postaccumulation cementation|Cementation]] and [[Reservoir quality#Compaction|compaction]] occur with burial, reducing the reservoir quality of the [[Mud-supported carbonate|mud-supported]] mudstones and wackestones more than the [[Grain-supported carbonate|grain-supported]] packestones and grainstones. The result is a vertical sequence of lower [[porosity]] and [[permeability]] mud-supported rocks at the base and higher porosity and permeability grain-supported rocks at the top. Consequently, the best quality [[Flow units for reservoir characterization|flow unit]] occurs at the top of the sequence. The permeable units are confined to the grainstone [[bar]]s.

If the grainstone bars are exposed to [[meteoric diagenesis]], significant separate vug porosity can develop, causing a loss of permeability while retaining porosity. In the dolomite environment, grainstone bars are commonly cemented with [[anhydrite]], and [[intercrystalline porosity]] in mud-supported sediments forms the permeable facies.

If the grainstone bars are exposed to [[meteoric diagenesis]], significant separate vug porosity can develop, causing a loss of permeability while retaining porosity. In the dolomite environment, grainstone bars are commonly cemented with [[anhydrite]], and [[intercrystalline porosity]] in mud-supported sediments forms the permeable facies.