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VA – GP - OA: Numerical Multiphase PTA
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Figure 34: Influence of grid refinement on oscillations (R=50,000 ft, k=10 mD)
4.2. Analysis of multiphase processes during drawdown and build up
Drawdown analysis
Figure 35 shows the evolution of the pressure derivative during the production phase when
R=50,000 ft, for three different permeability values. Although oscillations are present, we can
observe a global increase of the derivative for each case. This corresponds to a decrease of the
total mobility while oil saturation appears and increases in the reservoir.
Figure 35: Evolution of the pressure derivative for various values of permeability (R=50,000 ft)
This is explained by the non-linearity of the total mobility curve, as previously explained in
section 1.2. When oil appears in the medium, the total mobility decreases as long as the oil
saturation is not too high (Figure 36).
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Pressure [psi]
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K=10mD refined
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K=20mD
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K=8mD