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  | 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
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  | frompg  = 5-26
  | topg    = 5-64
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  | topg    = 5-26
 
  | 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
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==Plotting gradient==
 
==Plotting gradient==
The table below outlines the procedure for plotting a hydrocarbon pressure gradient on a hydrostatic pressure plot when a measured pressure is available from the [[reservoir]].
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The list below outlines the procedure for plotting a hydrocarbon pressure gradient on a hydrostatic pressure plot when a measured pressure is available from the [[reservoir]].
   −
{| class = "wikitable"
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# Plot measured fluid pressure on a hydrostatic pressure–depth plot.
|-
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# Determine the hydrocarbon pressure gradient from one of two ways:
! Step
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#*  Measured hydrocarbon [[Wikipedia:Density|density]]  
! Action
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#*  Estimates of hydrocarbon density
|-
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# Determine the [[buoyancy pressure]] gradient: [[Normal hydrostatic pressure gradients|static water pressure gradient]] minus hydrocarbon pressure gradient.
| 1
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# Determine a pressure above or below the measured depth point. The table below lists the steps for determining this number.
| Plot measured fluid pressure on a hydrostatic pressure–depth plot.
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## Pick a depth above or below the measured point.  
|-
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## Multiply the difference in depth by the buoyancy pressure gradient.  
| 2
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## Add the number from step 2 to the measured pressure if the depth is deeper; subtract if shallower.
| Determine the hydrocarbon pressure gradient from one of two ways:
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##*'''Example:''' Measured pressure at [[depth::7607 ft]] is [[pressure::3530 psi]] and buoyancy pressure gradient is 0.076 psi/ft. What is the hydrocarbon pressure at [[depth::7507 ft]]?
*  Measured hydrocarbon [[density]]  
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##*'''Solution:'''
*  Estimates of hydrocarbon density
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##** <math>7607 \text{ ft} - 7507 \text{ ft} = 100 \text{ ft} </math>
|-
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##** <math>100 \text{ ft} \times 0.076 \text{ psi/ft} = 7.6 \text{ psi} </math>
| 3
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##** <math>\text{Hydrocarbon pressure at 7507 ft } = 3530 \text{ psi} - 7.6 \text{ psi} = 3522.4 \text{ psi} </math>
| Determine the [[buoyancy pressure]] gradient: [[Normal hydrostatic pressure gradients|static water pressure gradient]] minus hydrocarbon pressure gradient.
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# Plot the pressure number from step 4 on the pressure–depth plot and draw a line between this point and the measured pressure point. This line is the hydrocarbon pressure gradient.
|-
  −
| 4
  −
| Determine a pressure above or below the measured depth point. The table below lists the steps for determining this number.
  −
# Pick a depth above or below the measured point.  
  −
# Multiply the difference in depth by the buoyancy pressure gradient.  
  −
# Add the number from step 2 to the measured pressure if the depth is deeper; subtract if shallower.
  −
 
  −
'''Example:''' Measured pressure at [[depth::7607 ft]] is [[pressure::3530 psi]] and buoyancy pressure gradient is 0.076 psi/ft. What is the hydrocarbon pressure at [[depth::7507 ft]]?
  −
 
  −
'''Solution:'''
  −
* 7607 ft 7507 ft = 100 ft
  −
* 100 ft × 0.076 psi/ft = 7.6 psi
  −
* Hydrocarbon pressure at [[depth::7507 ft]] = [[pressure::3530 psi]] – [[pressure::7.6 psi]] = [[pressure::3522.4 psi]]
  −
|-
  −
| 5
  −
| Plot the pressure number from step 4 on the pressure–depth plot and draw a line between this point and the measured pressure point. This line is the hydrocarbon pressure gradient.
  −
|}
      
==See also==
 
==See also==
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* [[Estimating static oil pressure gradients]]
 
* [[Estimating static oil pressure gradients]]
 
* [[Estimating static gas pressure gradients]]
 
* [[Estimating static gas pressure gradients]]
* [[Finding free-water level using pressure]]
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* [[Free water level determination using pressure]]
    
==External links==
 
==External links==
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[[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]]
 +
[[Category:Treatise Handbook 3]]

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