Hydrocarbon pressure gradient: plotting
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Exploring for Oil and Gas Traps | |
Series | Treatise in Petroleum Geology |
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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 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.
Step | Action |
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1 | Plot measured fluid pressure on a hydrostatic pressure–depth plot. |
2 | Determine the hydrocarbon pressure gradient from one of two ways:
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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.
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:
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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
- Static hydrocarbon pressure gradients
- Estimating static oil pressure gradients
- Estimating static gas pressure gradients
- Finding free-water level using pressure