Difference between revisions of "P/Z plot"
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Therefore at any time: | Therefore at any time: | ||
| − | :<math> \frac{G_p}{GIIP}=1-\frac{P}{z} \frac{z_i}{P_i}</math> | + | :<math> \frac{G_p}{GIIP}=1-\frac{P}{z} \frac{z_i}{P_i}</math>, or <math> \frac{P}{z}=\frac{P_i}{z_i} \left (1- \frac{G_p}{GIIP}\right )</math> |
| − | + | Thus a the plot of P/z vs cumulative produced gas is a straight line intersecting X axis at GIIP. | |
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== Discussion == | == Discussion == | ||
Revision as of 09:03, 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.
Math & Physics
The P/Z plot is based on the Gas Material Balance equation.
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 the 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
= pipe diameter, ft
= gas holdup factor, dimensionless
= bubble-slug boundary, dimensionless
= gas velocity, ft/sec
= liquid velocity, ft/sec
= 0.8, slip velocity (difference between average gas and liquid velocities), ft/sec
References
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