Changes

{{publication  

{{publication  

  | image  = exploring-for-oil-and-gas-traps.png

  | image  = exploring-for-oil-and-gas-traps.png

  | part    = Critical elements of the petroleum system

  | part    = Critical elements of the petroleum system

  | chapter = Formation fluid pressure and its application

  | chapter = Formation fluid pressure and its application

  | frompg  = 5-1

  | frompg  = 5-9

  | topg    = 5-64

  | topg    = 5-9

  | author  = Edward A. Beaumont, Forrest Fiedler

  | author  = Edward A. Beaumont, Forrest Fiedler

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch05/ch05.htm

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch05/ch05.htm

  | isbn    = 0-89181-602-X

  | isbn    = 0-89181-602-X

}}

}}

When a [[fluid pressure]] is higher than estimated from the [[Normal hydrostatic pressure gradients|normal hydrostatic fluid gradient]] for a given depth, it is called overpressure. For this situation to occur, the fluid must first be trapped within a rock unit (pressure compartment).

When a [[Normal hydrostatic pressure#Fluid pressure|fluid pressure]] is higher than estimated from the [[Normal hydrostatic pressure gradients|normal hydrostatic fluid gradient]] for a given depth, it is called overpressure. For this situation to occur, the fluid must first be trapped within a rock unit (pressure compartment).

Overpressure can be caused by [[uplift]], increased [[heat]], [[compaction]], [[Hydrocarbon generation|generation of hydrocarbons]], or a combination of these factors.

Overpressure can be caused by [[uplift]], increased [[heat]], [[compaction]], [[Petroleum generation|generation of hydrocarbons]], or a combination of these factors.

==Uplift==

==Uplift==

[[file:formation-fluid-pressure-and-its-application_fig5-2.png|300px|thumb|{{figure number|1}}Encapsulated fluid in an uplifted unit.]]

[[file:formation-fluid-pressure-and-its-application_fig5-2.png|500px|thumb|{{figure number|1}}Encapsulated fluid in an uplifted unit.]]

A unit can be uplifted into a regime of lower [[Normal hydrostatic pressure|normal pressure]]. The encapsulated fluid then is at a pressure higher than that found at the new depth in surrounding formations where the fluid is under normal constraints.

A unit can be uplifted into a regime of lower [[Normal hydrostatic pressure|normal pressure]]. The encapsulated fluid then is at a pressure higher than that found at the new depth in surrounding [[formation]]s where the fluid is under normal constraints.

The diagrams in [[:file:formation-fluid-pressure-and-its-application_fig5-2.png|Figure 1]] illustrate this situation.

The diagrams in [[:file:formation-fluid-pressure-and-its-application_fig5-2.png|Figure 1]] illustrate this situation.

==Compaction==

==Compaction==

As an encapsulated rock mass is buried, it tends to compact. Under normal conditions, as the [[porosity]] is reduced, the interstitial fluid is expelled. When the fluid cannot escape, the pressure within the encapsulated rock mass rises. This higher fluid pressure takes on some of the overburden load, limiting the amount of compaction. In such cases, the fluid is overpressured and the rock matrix is undercompacted.

As an encapsulated rock mass is buried, it tends to compact. Under normal conditions, as the [[porosity]] is reduced, the [[interstitial fluid]] is expelled. When the fluid cannot escape, the pressure within the encapsulated rock mass rises. This higher fluid pressure takes on some of the [[overburden]] load, limiting the amount of compaction. In such cases, the fluid is overpressured and the rock [[matrix]] is undercompacted.

==See also==

==See also==

[[Category:Critical elements of the petroleum system]]  

[[Category:Critical elements of the petroleum system]]  

[[Category:Formation fluid pressure and its application]]

[[Category:Formation fluid pressure and its application]]