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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 | + | | frompg = 5-27 |
− | | topg = 5-64 | + | | topg = 5-28 |
| | 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 |
| }} | | }} |
− | 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 down[[dip]] 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 repeat formation tester (RFT) data== |
| [[file:formation-fluid-pressure-and-its-application_fig5-12.png|400px|thumb|{{figure number|1}}Easy method for determining free-water level (FWL) by projecting RFT pressure data downward from a reservoir to the aquifer.]] | | [[file:formation-fluid-pressure-and-its-application_fig5-12.png|400px|thumb|{{figure number|1}}Easy method for determining free-water level (FWL) by projecting RFT pressure data downward from a reservoir to the aquifer.]] |
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− | An easy method for determining free-water level (FWL) is projecting RFT pressure data downward from a reservoir to the aquifer. [[:file:formation-fluid-pressure-and-its-application_fig5-12.png|Figure 1]] illustrates the procedure. | + | An easy method for determining free water level (FWL) is projecting [[Wireline formation testers|RFT]] pressure data downward from a reservoir to the aquifer. [[:file:formation-fluid-pressure-and-its-application_fig5-12.png|Figure 1]] illustrates the procedure. |
| | | |
| ==Procedure using a single measurement== | | ==Procedure using a single measurement== |
− | The table below outlines the procedure for determining the free-water level using a single pressure buildup point in the reservoir. | + | The list below outlines the procedure for determining the free water level using a single [[Pressure_transient_testing#Pressure_drawdown_and_buildup_tests|pressure buildup]] point in the reservoir. |
| | | |
− | {| class = "wikitable"
| + | # Determine [[buoyancy pressure]] (''P''<sub>b</sub> ) at the depth of the measured pressure (P<sub>m</sub> ) from the measured pressure: |
− | |-
| + | #*:<math>P_{\rm b} = P_{\rm m} - P_{\rm hydrostatic}</math> |
− | ! Step
| + | # Determine buoyancy pressure gradient (''P''<sub>bg</sub> ): |
− | ! Action
| + | #*:<math>P_{\rm bg} = P_{\rm hydrostatic\ pressure\ gradient} - P_{\rm hydrocarbon\ pressure\ gradient}</math> |
− | |-
| + | # Calculate downdip length of [[hydrocarbon column]] (''h''): |
− | | 1
| + | #*:<math>h = \frac{P_{\rm b}}{P_{\rm bg}}</math> |
− | | Determine buoyancy pressure (''P''<sub>b</sub> ) at the depth of the measured pressure (P<sub>m</sub> ) from the measured pressure:
| |
− | | |
− | :<math>P_{\rm b} = P_{\rm m} - P_{\rm hydrostatic}</math> | |
− | | |
− | |-
| |
− | | 2
| |
− | | Determine buoyancy pressure gradient (''P''<sub>bg</sub> ):
| |
− | | |
− | :<math>P_{\rm bg} = P_{\rm hydrostatic\ pressure\ gradient} - P_{\rm hydrocarbon\ pressure\ gradient}</math> | |
− | | |
− | |-
| |
− | | 3
| |
− | | Calculate downdip length of hydrocarbon column (''h''):
| |
− | | |
− | :<math>h = \frac{P_{\rm b}}{P_{\rm bg}}</math> | |
− | | |
− | |}
| |
| | | |
| As an example, let's determine the downdip length of a 30°API oil column with the following givens: | | As an example, let's determine the downdip length of a 30°API oil column with the following givens: |
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| :<math>h = \frac{P_{\rm b}}{P_{\rm bg}} = 30 \mbox{ psi} \div 0.054 \mbox{ psi/ft} = 556 \mbox{ ft}</math> | | :<math>h = \frac{P_{\rm b}}{P_{\rm bg}} = 30 \mbox{ psi} \div 0.054 \mbox{ psi/ft} = 556 \mbox{ ft}</math> |
| | | |
− | Therefore, the free-water level is at [[depth::8167 ft]]. | + | Therefore, the free water level is at [[depth::8167 ft]]. |
| | | |
| ==See also== | | ==See also== |
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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]] |