Difference between revisions of "Free water level determination using pressure"
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− | The free-water level occurs where buoyancy pressure is zero in the reservoir-aquifer system. It defines the downdip limits of an accumulation. Pressure data reliability affects the resolution; however, resolution improves when it is supplemented with other petrophysical information. | + | The free-water level occurs where buoyancy pressure is zero in the reservoir-aquifer system. It defines the downdip limits of an [[accumulation]]. Pressure data reliability affects the resolution; however, resolution improves when it is supplemented with other petrophysical information. |
==Procedure: using RFT data== | ==Procedure: using RFT data== |
Revision as of 21:07, 22 July 2014
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 |
The free-water level occurs where buoyancy pressure is zero in the reservoir-aquifer system. It defines the downdip limits of an accumulation. Pressure data reliability affects the resolution; however, resolution improves when it is supplemented with other petrophysical information.
Procedure: using RFT data[edit]
An easy method for determining free-water level (FWL) is projecting RFT pressure data downward from a reservoir to the aquifer. Figure 1 illustrates the procedure.
Procedure using a single measurement[edit]
The table below outlines the procedure for determining the free-water level using a single pressure buildup point in the reservoir.
Step | Action |
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1 | Determine buoyancy pressure (Pb ) at the depth of the measured pressure (Pm ) from the measured pressure:
|
2 | Determine buoyancy pressure gradient (Pbg ):
|
3 | Calculate downdip length of hydrocarbon column (h):
|
As an example, let's determine the downdip length of a 30°API oil column with the following givens:
- Pm = pressure::3555 psi at depth::7611 ft
- Phydrostatic = 3525 psi
- Phydrostatic pressure gradient = 0.465 psi/ft
- Phydrocarbon pressure gradient = 0.38 psi/ft
Answer (tied back to steps above):
Therefore, the free-water level is at depth::8167 ft.
See also[edit]
- Static hydrocarbon pressure gradients
- Estimating static oil pressure gradients
- Estimating static gas pressure gradients
- Plotting the hydrocarbon pressure gradient