Difference between revisions of "P/Z plot"
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Applying [[Real Gas]] [[EOS]] at reservoir conditions: | Applying [[Real Gas]] [[EOS]] at reservoir conditions: | ||
| − | :<math> PV_r=z\frac{m}{M} RT_r</math> (1) | + | :<math> PV_r=z\frac{m}{M} RT_r</math> (1) |
Applying [[Real Gas]] [[EOS]] at standard conditions: | Applying [[Real Gas]] [[EOS]] at standard conditions: | ||
| − | :<math> P_{SC}V_g=1\frac{m}{M} RT_{SC}</math> (2) | + | :<math> P_{SC}V_g=1\frac{m}{M} RT_{SC}</math> (2) |
Dividing eq. 2 by eq. 1 and rearranging: | Dividing eq. 2 by eq. 1 and rearranging: | ||
| − | :<math> V_g=\frac{P}{z} \frac{V_rT_{SC}}{P_{SC}T_{r}}</math>(3) | + | :<math> V_g=\frac{P}{z} \frac{V_rT_{SC}}{P_{SC}T_{r}}</math> (3) |
Applying eq. 3 for initial conditions and for any point in time: | Applying eq. 3 for initial conditions and for any point in time: | ||
Revision as of 09:16, 21 November 2017
Brief
The P/Z plot is a plot of P/z versus cumulative gas production, Gp.
The interpretation technique is fitting the data points with the straight line to estimate GIIP.
The P/Z plot is based on the Gas Material Balance equation.
Math & Physics
Applying Real Gas EOS at reservoir conditions:
(1)
Applying Real Gas EOS at standard conditions:
(2)
Dividing eq. 2 by eq. 1 and rearranging:
(3)
Applying eq. 3 for initial conditions and for any point in time:
Applying eq. 3 for any point in time:
Therefore at any time:
Or:
Thus a plot of P/z vs cumulative produced gas is a straight line intersecting X axis at GIIP.
Discussion
Griffith correlation adds a hook to the originally straight Hagedorn and Brown VLP curve.
Nomenclature
= gas initially in place, ft3
= reservoir pressure (changing), psia
= initial reservoir pressure (constant), psia
= pressure at standard conditions, psia
= initial reservoir pressure (constant), °R
= reservoir pressure (constant), °R
= temperature at standard conditions (constant), °R
= reservoir volume (constant), ft3
= volume of gas in reservoir converted to standard conditions (changing), ft3
= gas compressibility factor (changing), dimensionless
References
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