Difference between revisions of "Hydrocarbon pressure gradient: plotting"
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==Plotting gradient== | ==Plotting gradient== | ||
− | The | + | 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]]. |
− | + | # Plot measured fluid pressure on a hydrostatic pressure–depth plot. | |
− | + | # Determine the hydrocarbon pressure gradient from one of two ways: | |
− | + | #* Measured hydrocarbon [[Wikipedia:Density|density]] | |
− | + | #* Estimates of hydrocarbon density | |
− | + | # Determine the [[buoyancy pressure]] gradient: [[Normal hydrostatic pressure gradients|static water pressure gradient]] minus hydrocarbon pressure gradient. | |
− | + | # 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]]? | |
− | * Measured hydrocarbon [[Wikipedia:Density|density]] | + | ##*'''Solution:''' |
− | * Estimates of hydrocarbon density | + | ##** 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]] | |
− | + | # 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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− | # 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. | ||
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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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− | '''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]] | ||
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==See also== | ==See also== |
Revision as of 15:18, 27 October 2014
Exploring for Oil and Gas Traps | |
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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.
- Plot measured fluid pressure on a hydrostatic pressure–depth plot.
- Determine the hydrocarbon pressure gradient from one of two ways:
- Measured hydrocarbon density
- Estimates of hydrocarbon density
- Determine the buoyancy pressure gradient: static water pressure gradient minus hydrocarbon pressure gradient.
- 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
- 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
- Static hydrocarbon pressure gradients
- Estimating static oil pressure gradients
- Estimating static gas pressure gradients
- Free water level determination using pressure