Difference between revisions of "Hydrocarbon pressure gradient: plotting"

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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
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  | frompg  = 5-1
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  | frompg  = 5-26
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  | 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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  | isbn    = 0-89181-602-X
 
  | isbn    = 0-89181-602-X
 
}}
 
}}
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We can estimate the [[Dip|downdip]] [[Free water level|free-water level]] from a valid [[Normal_hydrostatic_pressure#Fluid_pressurefluid pressure]] measured within a reservoir.
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We can estimate the [[Dip|downdip]] [[Free water level|free-water level]] from a valid [[Normal hydrostatic pressure#Fluid_pressure|fluid pressure]] measured within a reservoir.
  
 
==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]].
  
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{| class = "wikitable"
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# Plot measured fluid pressure on a hydrostatic pressure–depth plot.
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|-
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# Determine the hydrocarbon pressure gradient from one of two ways:
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! Step
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#*  Measured hydrocarbon [[Wikipedia:Density|density]]
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! Action
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#*  Estimates of hydrocarbon density
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|-
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# Determine the [[buoyancy pressure]] gradient: [[Normal hydrostatic pressure gradients|static water pressure gradient]] minus hydrocarbon pressure gradient.
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| 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.
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| 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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|-
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## Multiply the difference in depth by the buoyancy pressure gradient.  
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| 2
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## Add the number from step 2 to the measured pressure if the depth is deeper; subtract if shallower.
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| 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]]?
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*  Measured hydrocarbon density  
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##*'''Solution:'''
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*  Estimates of hydrocarbon density
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##** <math>7607 \text{ ft} - 7507 \text{ ft} = 100 \text{ ft} </math>
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|-
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##** <math>100 \text{ ft} \times 0.076 \text{ psi/ft} = 7.6 \text{ psi} </math>
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| 3
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##** <math>\text{Hydrocarbon pressure at 7507 ft } = 3530 \text{ psi} - 7.6 \text{ psi} = 3522.4 \text{ psi} </math>
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| Determine the buoyancy pressure gradient: 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.
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|-
 
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| 4
 
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| Determine a pressure above or below the measured depth point. The table below lists the steps for determining this number.
 
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# 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]]?
 
−
 
 
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'''Solution:'''
 
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* 7607 ft – 7507 ft = 100 ft
 
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* 100 ft × 0.076 psi/ft = 7.6 psi
 
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* Hydrocarbon pressure at [[depth::7507 ft]] = [[pressure::3530 psi]] – [[pressure::7.6 psi]] = [[pressure::3522.4 psi]]
 
−
|-
 
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| 5
 
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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.
 
−
|}
 
  
 
==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]]
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* [[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]]

Latest revision as of 17:54, 17 February 2022

Exploring for Oil and Gas Traps
Series Treatise in Petroleum Geology
Part Critical elements of the petroleum system
Chapter Formation fluid pressure and its application
Author Edward A. Beaumont, Forrest Fiedler
Link Web page
Store AAPG Store

We can estimate the downdip free-water level from a valid fluid pressure measured within a reservoir.

Plotting gradient

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.

  1. Plot measured fluid pressure on a hydrostatic pressure–depth plot.
  2. Determine the hydrocarbon pressure gradient from one of two ways:
    • Measured hydrocarbon density
    • Estimates of hydrocarbon density
  3. Determine the buoyancy pressure gradient: static water pressure gradient minus hydrocarbon pressure gradient.
  4. Determine a pressure above or below the measured depth point. The table below lists the steps for determining this number.
    1. Pick a depth above or below the measured point.
    2. Multiply the difference in depth by the buoyancy pressure gradient.
    3. 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:
  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

External links

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