The P/Z plot is a plot of P/z versus Reservoir 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
Dividing eq. 2 by eq. 1 and rearranging:
Applying eq. 3 for initial conditions and for any point in time:
Applying eq. 3 for any point in time:
Therefore at any time:
Thus a plot of P/z vs cumulative produced gas is a straight line intersecting X axis at GIIP.
Example 1. Multiple Reservoirs on the same P/Z plot in the E&P Portal
- Upload the data required
- Go to the Reservoir Management -> Performance Plots
- Select the Reservoirs you want to see and the Data range and click "Search"
- Scroll down the Performance Plots to see the P/Z plot
- Create Field here
- Upload Wells
- Upload Monthly Measures here
- Create or Upload Reservoirs here
- Input the Reservoirs GIIP here
- Create or Upload PVT (SG, Pi, Ti) here
- = gas initially in place, scf
- = cumulative gas produced, scf
- = reservoir pressure (changing), psia
- = initial reservoir pressure (constant), psia
- = pressure at standard conditions, psia
- = initial reservoir temperature (constant), °R
- = reservoir temperature (constant), °R
- = temperature at standard conditions (constant), °R
- = volume of gas in reservoir converted to standard conditions (changing), scf
- = reservoir volume (constant), ft3
- = gas compressibility factor (changing), dimensionless
- = initial gas compressibility factor (constant), dimensionless