PROPERTIES OF RESERVOIR GASES - Petroleum Reservoir Fluid Property Correlations - page 16

Recommended correlation equations/procedures for estimation of gas
z-factors based on gas specific gravities and nonhydrocarbon contents
The recommended equations for estimation of the pseudocritical
properties are given in equations (2.4)-(2.6). 16

(2.4)

(2.5)

(2.6)

where

i α i β i

0 1.1582E-01 3.8216E+00

1 -4.5820E-01 -6.5340E-02

2 -9.0348E-01 -4.2113E-01

3 -6.6026E-01 -9.1249E-01

4 7.0729E-01 1.7438E+01

5 -9.9397E-02 -3.2191E+00

The summations in each of equations (2.5) and (2.6) are hydrogen
sulfide, carbon dioxide, and nitrogen, in that order.
The recommended equations for representation of the Standing-Katz
graphical z-factor correlation are from DAK, shown in equation (2.7). 17

(2.7)

where

(2.8)