Changes

* The water–hydrocarbon saturation of a flow unit at different buoyancy pressures.

* The water–hydrocarbon saturation of a flow unit at different buoyancy pressures.

Placing flow units into structural cross sections shows their position with respect to the [[free water level]] and buoyancy pressure profile. Using the structure sections, saturation profiles can be made for each flow unit, their corresponding containers, and the reservoir as a whole.

Placing flow units into structural [[cross section]]s shows their position with respect to the [[free water level]] and buoyancy pressure profile. Using the structure sections, saturation profiles can be made for each flow unit, their corresponding containers, and the reservoir as a whole.

==Pore throat size and saturation profiles==

==Pore throat size and saturation profiles==

In rocks with microporosity, capillary forces hold water tightly to rock surfaces, decreasing the effective size of the already small pore throats. Therefore, a greater buoyancy pressure is required for oil or gas to migrate. Micropore reservoirs have longer saturation transition zones than macro- or mesoporous reservoirs; immobile water saturation is lower in macroporous rocks.

In rocks with microporosity, capillary forces hold water tightly to rock surfaces, decreasing the effective size of the already small pore throats. Therefore, a greater buoyancy pressure is required for oil or gas to migrate. Micropore reservoirs have longer saturation transition zones than macro- or mesoporous reservoirs; immobile water saturation is lower in macroporous rocks.

In the example reservoir cross section in [[:file:predicting-reservoir-system-quality-and-performance_fig9-22.png|Figure 1]], the rock in container 1 is mesoporous; the rock in container 2 is macroporous. Container 1 has a longer transition zone than container 2 because of this. Both containers have the same buoyancy pressure and free water level because the two containers are in pressure communication.

In the example reservoir [[cross section]] in [[:file:predicting-reservoir-system-quality-and-performance_fig9-22.png|Figure 1]], the rock in container 1 is mesoporous; the rock in container 2 is macroporous. Container 1 has a longer transition zone than container 2 because of this. Both containers have the same buoyancy pressure and free water level because the two containers are in pressure communication.

==Pore throat size sorting==

==Pore throat size sorting==