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Line 167: − − [[file:fluid-contacts_fig4.png|thumb|{{figure number|4}}Effect of reservoir heterogeneity on fluid contacts. (a) [[Capillary pressure]] curves for facies A and B within the reservoir. The dashed line corresponds to the saturation trend of the well In part (b). Sharp changes in saturation correspond to elevations of facies changes. (b) Oil-water contact corresponding to capillary pressure curves. The free water surface (''f''<sub>w</sub>) is the same for all facies, but the different displacement pressure results in different oil-water contact elevations (thick arrows). The transition zones will also have different thicknesses due to different [[relative permeability]] characteristics not shown here. The vertical line is the well position corresponding to the saturation profile shown in part (a).]]
→Hydrodynamic gradients
===Hydrodynamic gradients===
===Hydrodynamic gradients===
[[file:fluid-contacts_fig3.png|left|thumb|{{figure number|3}}Example of calculating hydrodynamic fluid contacts from pressure data. Pressure elevations are shown by arrows. Calculated fluid contacts are shown by thin lines.]]
[[file:fluid-contacts_fig3.png|thumb|{{figure number|3}}Example of calculating hydrodynamic fluid contacts from pressure data. Pressure elevations are shown by arrows. Calculated fluid contacts are shown by thin lines.]]
A common type of nonhorizontal oil-water contact is tilting in response to hydrodynamics, the movement of water in the reservoir interval. Hydrodynamic conditions that affect fluid contacts are usually associated with active [[meteoric aquifer]]s at relatively shallow depths. Indications of active [[meteoric flow]] include low salinity water, high topographic relief, and proximity to [[recharge]] areas.
A common type of nonhorizontal oil-water contact is tilting in response to hydrodynamics, the movement of water in the reservoir interval. Hydrodynamic conditions that affect fluid contacts are usually associated with active [[meteoric aquifer]]s at relatively shallow depths. Indications of active [[meteoric flow]] include low salinity water, high topographic relief, and proximity to [[recharge]] areas.
Potentiometric elevations are mapped and contoured to determine the change in potentiometric elevation per unit distance, called the ''potentiometric gradient''. The hydrodynamic tilt of a fluid contact can be estimated from the potentiometric gradient and fluid densities by the following relationship:<ref name=pt06r56>Hubbert, M. K., 1953, [http://archives.datapages.com/data/bulletns/1953-56/data/pg/0037/0008/1950/1954.htm Entrapment of petroleum under hydrodynamic conditions]: AAPG Bulletin, v. 37, p. 1954–2026.</ref><ref name=pt06r21>Dahlberg, E. C., 1982, Applied Hydrodynamics in Petroleum Exploration: New York, Springer Verlag, 161 p.</ref>
Potentiometric elevations are mapped and contoured to determine the change in potentiometric elevation per unit distance, called the ''potentiometric gradient''. The hydrodynamic tilt of a fluid contact can be estimated from the potentiometric gradient and fluid densities by the following relationship:<ref name=pt06r56>Hubbert, M. K., 1953, [http://archives.datapages.com/data/bulletns/1953-56/data/pg/0037/0008/1950/1954.htm Entrapment of petroleum under hydrodynamic conditions]: AAPG Bulletin, v. 37, p. 1954–2026.</ref><ref name=pt06r21>Dahlberg, E. C., 1982, Applied Hydrodynamics in Petroleum Exploration: New York, Springer Verlag, 161 p.</ref>
:<math>h_{\rm A} = 2369/0.433 - 5160 = 311 \mbox{ ft}</math>
:<math>h_{\rm A} = 2369/0.433 - 5160 = 311 \mbox{ ft}</math>