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Saphir Guided Session #4
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SapGS04 - 10/11
F01 • Material Balance
The material balance option is available in the Model dialog to model gas tests in a closed
system. It takes into account the changing fluid compressibility with respect to the depleting
average pressure.
Open the session with the file SapGS04_2.ks3 located in the Examples directory.
The pressure data have been generated with a numerical simulator and takes into account the
exact PVT at the actual pressure at any point of the reservoir.
Fig. F01.1 • Analytical model match closed square without material balance
The data clearly exhibits the pseudo-steady state behavior of a closed reservoir.
The match is made with an analytical model of a well in a 4000ft x 4000ft square closed
rectangle without the gas material balance option. The analytical model simulation exhibits a
constant linear pressure decline higher than the decline given by the numerical simulation.
This is due to the fact that the fluid compressibility increases when the pressure depletes. In
other words, the same amount of extracted fluid makes the pressure decline less. The match is
poor at late time in the loglog plot (production #1) and does not match the buildup at all in the
history plot.
Create a new analysis from the previous.
Click on the Model icon to call the Model dialog.
Check the 'material balance' option check box and Generate.