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VA – GP - OA: Numerical Multiphase PTA
p 19/29
Let us consider a slightly stronger depletion, such that gas appears in a wider zone, but with
low saturations, so that all the gas is still immobile. This is the case for R=10,000 ft, k=200
mD, as shown on Figure 26. In this case, while the regime becomes pseudo-permanent, the
flowing composition becomes representative of the “external” oil depleted at the current
external pressure. As a consequence, the produced GOR decreases.
Figure 26
: Evolution of the rates during production phase (R=10,000 ft, k=200mD)
For a stronger depletion (R=5,000 ft, k=100 mD), the GOR still exhibits a first decrease while
the flowing composition stabilizes. Then, the gas saturation increases everywhere, until the
gas becomes moveable and starts to be produced. As a consequence, the GOR starts to
increase (Figure 27).
Figure 27
: Evolution of the rates during production phase (R=5,000 ft, k=100 mD)
3200
4200
Pressure [psia]
0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000
Time [hr]
9700
10100
10500
Liquid rate [STB/D]
13900
14400
14900
15400
Gas rate [Mscf/D]
qo
qg
Simulated qo
Simulated qg
2000
3000
4000
Pressure [psia]
0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000
Time [hr]
9000
10000
11000
Liquid rate [STB/D]
12000
13000
14000
15000
16000
Gas rate [Mscf/D]
qo
qg
Simulated qo
Simulated qg