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Line 50: − + − + − + − + − Step 1:+ − + − Step 2:+ − − :<math>\mbox{P}_{\rm hydrostatic\ pressure\ gradient} - \mbox{P}_{\rm hydrocarbon\ pressure\ gradient} = 0.465 - 0.38 = 0.085 \mbox{ psi/ft}</math> − − Step 3: − −
Free water level determination using pressure (view source)
Revision as of 15:59, 30 January 2014
, 15:59, 30 January 2014formatting
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| Determine buoyancy pressure (P<sub>b</sub> ) at the depth of the measured pressure (P<sub>m</sub> ) from the measured pressure:
| Determine buoyancy pressure (''P''<sub>b</sub> ) at the depth of the measured pressure (P<sub>m</sub> ) from the measured pressure:
:<math>\mbox{P}_{\rm b} = \mbox{P}_{\rm m} - \mbox{P}_{\rm hydrostatic}</math>
:<math>P_{\rm b} = P_{\rm m} - P_{\rm hydrostatic}</math>
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| Determine buoyancy pressure gradient (P<sub>bg</sub> ):
| Determine buoyancy pressure gradient (''P''<sub>bg</sub> ):
:<math>\mbox{P}_{\rm bg} = \mbox{P}_{\rm hydrostatic\ pressure\ gradient} - \mbox{P}_{\rm hydrocarbon\ pressure\ gradient}</math>
:<math>P_{\rm bg} = P_{\rm hydrostatic\ pressure\ gradient} - P_{\rm hydrocarbon\ pressure\ gradient}</math>
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| Calculate downdip length of hydrocarbon column (h):
| Calculate downdip length of hydrocarbon column (''h''):
:<math>\mbox{h} = \frac{\mbox{P}_{\rm b}}{\mbox{P}_{\rm bg}}</math>
:<math>h = \frac{P_{\rm b}}{P_{\rm bg}}</math>
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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:
* P<sub>m</sub> = 3555 psi at 7611 ft
* ''P''<sub>m</sub> = [[pressure::3555 psi]] at [[depth::7611 ft]]
* P<sub>hydrostatic</sub> = 3525 psi
* ''P''<sub>hydrostatic</sub> = 3525 psi
* P<sub>hydrostatic pressure gradient</sub> = 0.465 psi/ft
* ''P''<sub>hydrostatic pressure gradient</sub> = 0.465 psi/ft
* P<sub>hydrocarbon pressure gradient</sub> = 0.38 psi/ft
* ''P''<sub>hydrocarbon pressure gradient</sub> = 0.38 psi/ft
'''Answer''' (tied back to steps above):
'''Answer''' (tied back to steps above):
:<math>P_{\rm b} = P_{m} - P_{\rm hydrostatic} = 3555 - 3525 = 30\ \mathrm{psi}</math>
:<math>\mbox{P}_{\rm b} = \mbox{P}_{m} - \mbox{P}_{\rm hydrostatic} = 3555 - 3525 = 30 psi</math>
:<math>P_{\rm hydrostatic\ pressure\ gradient} - P_{\rm hydrocarbon\ pressure\ gradient} = 0.465 - 0.38 = 0.085 \mbox{ psi/ft}</math>
:<math>h = \frac{P_{\rm b}}{P_{\rm bg}} = 30 \mbox{ psi} \div 0.054 \mbox{ psi/ft} = 556 \mbox{ ft}</math>
:<math>\mbox{h} = \frac{\mbox{P}_{\rm b}}{\mbox{P}_{\rm bg}} = \mbox{30 \mbox{ psi}}{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]].