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Line 14: − This section discusses the concept of dynamic fluid systems and how hydrodynamic aquifers affect the distribution and accumulation of hydrocarbons.+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + − * [[Basic hydrodynamics]]
moved content from "Basic" article
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Hydrodynamics describes lateral fluid movement through aquifers that have generally low dip. The fluids can have a vertical component to their movement but, on a basinwide scale, the lateral flow component is of major concern.
===Hydraulic head===
Hydraulic head (H<sub>w</sub>) is the height or elevation above a given subsurface point at which a column connected to a body of water will equilibrate. It reflects the level of the potential energy possessed by the water.<ref name=ch05r5>Dahlberg, E., C., 1994, Applied Hydrodynamics in Petroleum Exploration, 2nd ed.: New York, Springer-Verlag, 295 p. Excellent subsurface fluid pressure reference. Covers hydrodynamic and static fluids.</ref>
The equation for hydraulic head is
:<math>\mbox{H}_{\rm w} = \mbox{Z} + \frac{\mbox{P}}{\rho \mbox{g}}</math>
where:
* H<sub>w</sub> = height above P (ft or m)
* Z = height (elevation) of P above a datum (ft or m)
* P = measured pressure (lb/ft<sup>2</sup> or kg/cm<sup>2</sup>)
* ρ = density of fluid (lb/ft<sup>3</sup> or g/cm<sup>3</sup>)
* g = coefficient of gravity (lb force/lb mass or kg force/kg mass)
The figure below illustrates the relationship of the variables H<sub>w</sub> and Z used in the above equation.
[[file:formation-fluid-pressure-and-its-application_fig5-35.png|thumb|{{figure number|5-35}}.]]
===Potential energy of fluids===
Potential energy (Φ) is the driving force of fluid movement. Its magnitude depends on the hydraulic head (H<sub>w</sub>) with respect to sea level and is expressed as
:<math>\Phi = \mbox{gH}_{\rm w} = \mbox{gZ} + \frac{\mbox{P}}{\rho}</math>
According to Dahlberg<ref name=ch05r5 />), hydraulic head serves as a practical approximation of fluid potential, since the only difference is the coefficient of gravity (g), which is fairly constant.
===Potentiometric surface===
The Potentiometric surface is the surface defined by the hydraulic head (elevation) from a rock unit from several different wells. If the Potentiometrie surface for a given subsurface rock unit is horizontal, then the potential energy of the water in that formation is constant and the water is at rest (hydrostatic). If the Potentiometrie surface is sloping, then the water moves (hydrodynamic) in the direction of the greatest downward slope.<ref name=ch05r11>Hubbert, K., 1953, Entrapment of petroleum under hydrodynamic conditions: AAPG Bulletin, vol. 37, no. 8, p. 1954–2026. The original paper that proposed hydrodynamics as an important trapping mechanism.</ref>
The figure below shows the Potentiometrie surface for hydrodynamic updip and downdip flow and hydrostatic no flow. The pressure-depth plot shows hypothetical pressure gradients for each condition.
[[file:formation-fluid-pressure-and-its-application_fig5-36.png|thumb|{{figure number|5-36}}.]]
===See also===
===See also===
* [[Hydrodynamic influence on trapping]]
* [[Hydrodynamic influence on trapping]]
* [[Mapping hydrodynamic traps]]
* [[Mapping hydrodynamic traps]]