Page 78 - Fundamentals of Reservoir Engineering

SOME BASIC CONCEPTS IN RESERVOIR ENGINEERING 17

1.1
Pseudo reduced temperature
3.0
2.8 1.05
1.0 2.6
2.4
2.2 1.2
2.0 1.3
1.9 1.1
0.9 1.8
1.7
1.6
0.8
1.5
1.45
0.7 1.4
1.35
Z -factor 0.6 1.25
1.3

1.2
0.5

1.15

0.4
1.1

0.3
1.05

0.2

0.1

0
0 1 2 3 4 5 6 7 8
Pseudo reduced pressure
11
Fig. 1.6 The Z− −− −factor correlation chart of Standing and Katz (Reproduced by courtesy
of the SPE of the AIME)

If the gas composition is not available, the Standing-Katz correlation can still be used
provided the gas gravity, based on the scale air = 1, at atmospheric pressure and at
60°F, is known (refer sec. 1.6). In this case fig. 1.7, is used to obtain the pseudo critical
pressure and temperature; then equs. (1.18) and (1.19) can be applied to calculate the
pseudo reduced parameters required to obtain the Z−factor from fig. 1.6.