Difference between revisions of "Hydrocarbon column: calculation of maximum height"

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  | part    = Predicting the occurrence of oil and gas traps
 
  | part    = Predicting the occurrence of oil and gas traps
 
  | chapter = Evaluating top and fault seal
 
  | chapter = Evaluating top and fault seal
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  | frompg  = 10-1
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  | frompg  = 10-68
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  | topg    = 10-94
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  | topg    = 10-68
 
  | author  = Grant M. Skerlec
 
  | author  = Grant M. Skerlec
 
  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch10/ch10.htm
 
  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch10/ch10.htm
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}}
 
}}
 
==Calculation==
 
==Calculation==
−
The maximum [[Hydrocarbon column|column of hydrocarbons]] that can accumulate under a [[seal]] occurs when the [[Buoyant pressure|buoyancy pressure]],''P''<sub>b</sub>, equals the [[displacement pressure]], ''P''<sub>d</sub>. If ''P''<sub>b</sub> exceeds ''P''<sub>d</sub>, the hydrocarbons will leak through the seal. If ''P''<sub>b</sub> is less than ''P''<sub>d</sub>, it would be possible to seal a greater column of hydrocarbons.
+
The maximum [[Hydrocarbon column|column of hydrocarbons]] that can accumulate under a [[seal]] occurs when the [[buoyancy pressure]], ''P''<sub>b</sub>, equals the [[displacement pressure]], ''P''<sub>d</sub>. If ''P''<sub>b</sub> exceeds ''P''<sub>d</sub>, the hydrocarbons will leak through the seal. If ''P''<sub>b</sub> is less than ''P''<sub>d</sub>, it would be possible to seal a greater column of hydrocarbons.
  
 
Therefore, for the maximum hydrocarbon column
 
Therefore, for the maximum hydrocarbon column
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==Effect on seal capacity==
 
==Effect on seal capacity==
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The height of the [[hydrocarbon column]] (h) in the above equations is a theoretical maximum. The actual height is less because of the effect of the reservoir. If the reservoir itself had zero [[displacement pressure]], the height of the hydrocarbon column would attain the theoretical maximum and the oil=water contact would coincide with the [[free water level]]. If the reservoir has some displacement pressure greater than zero, then the height of the hydrocarbon column is less than the theoretical maximum, or
+
The height of the [[hydrocarbon column]] (h) in the above equations is a theoretical maximum. The actual height is less because of the effect of the reservoir. If the reservoir itself had zero [[displacement pressure]], the height of the hydrocarbon column would attain the theoretical maximum and the [http://www.glossary.oilfield.slb.com/en/Terms.aspx?LookIn=term%20name&filter=oil-water+contact oil-water contact] would coincide with the [[free water level]]. If the reservoir has some displacement pressure greater than zero, then the height of the hydrocarbon column is less than the theoretical maximum, or
  
 
:<math>\mbox{h} = \left(\frac{\mbox{P}_{\rm ds} - \mbox{P}_{\rm dr}}{\rho_{\rm w} - \rho_{\rm h}}\right) 0.433</math>
 
:<math>\mbox{h} = \left(\frac{\mbox{P}_{\rm ds} - \mbox{P}_{\rm dr}}{\rho_{\rm w} - \rho_{\rm h}}\right) 0.433</math>
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==See also==
 
==See also==
 
* [[How capillary properties control seal]]
 
* [[How capillary properties control seal]]
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* [[Buoyant pressure]]
+
* [[Buoyancy pressure]]
 
* [[Top seal displacement pressure]]
 
* [[Top seal displacement pressure]]
  
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[[Category:Predicting the occurrence of oil and gas traps]]  
 
[[Category:Predicting the occurrence of oil and gas traps]]  
 
[[Category:Evaluating top and fault seal]]
 
[[Category:Evaluating top and fault seal]]
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[[Category:Treatise Handbook 3]]

Latest revision as of 16:13, 31 March 2022

Exploring for Oil and Gas Traps
Series Treatise in Petroleum Geology
Part Predicting the occurrence of oil and gas traps
Chapter Evaluating top and fault seal
Author Grant M. Skerlec
Link Web page
Store AAPG Store

Calculation

The maximum column of hydrocarbons that can accumulate under a seal occurs when the buoyancy pressure, Pb, equals the displacement pressure, Pd. If Pb exceeds Pd, the hydrocarbons will leak through the seal. If Pb is less than Pd, it would be possible to seal a greater column of hydrocarbons.

Therefore, for the maximum hydrocarbon column

or, in mixed units,

where:

  • ρw = density of water, g/cm3
  • ρh = density of hydrocarbon, g/cm3
  • g = acceleration due to gravity, cm/sec2
  • h = thickness of the hydrocarbon column, ft or m
  • γ is the interfacial tension,
  • θ is the contact angle between the wetting fluid and the solid surface, and
  • R is the capillary (pore throat) radius (Vavra et al., 1992[citation needed]).

Effect on seal capacity

The height of the hydrocarbon column (h) in the above equations is a theoretical maximum. The actual height is less because of the effect of the reservoir. If the reservoir itself had zero displacement pressure, the height of the hydrocarbon column would attain the theoretical maximum and the oil-water contact would coincide with the free water level. If the reservoir has some displacement pressure greater than zero, then the height of the hydrocarbon column is less than the theoretical maximum, or

where:

  • Pds = displacement pressure of the seal
  • Pdr = displacement pressure of the reservoir

See also

External links

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