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INPUT   DATA

♥ EXAMPLE Of Input/Output

Title

Gas Gravity

air = 1.0

Component	Mole Fraction
N2
CO2
H2S

Temperature		° C
Pressure		106N/m2

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OUTPUT   VARIABLES   &   GRAPH

Pressure		106N/m2
Z-factor
Viscosity		cp

Pressure	Z-factor	Viscosity
106N/m2		centipoise
0
10
...
40

Physical Properties Of Natural Gas - II

This calculator takes in the specific gravity of the natural gas (and molar fractions of gaseous impurities, if any) and outputs estimates of 2 physical properties of natural gas - Real gas deviation factor (Z) and Gas viscosity (μ). The 2 properties are listed and plotted for the specific temperature and pressure entered as well as for pressures in the range zero to 40 10⁶N/m² (=40MPa).

Z-factor is computed using the Hall-Yarborough direct method. This consists of 2 equations:

where:
    p_pr = pseudo-reduced pressure
    t = reciprocal of pseudo-reduced temperature
    y = "reduced" density (an unknown).

The specific gravity and gas composition values are first used to determine the constants in the equations (critical and pseudo-reduced pressures and temperatures). The second non-linear equation is solved for "y" using the Newton-Raphson iterative technique, and the result is plugged into the first equation.

Finally, Gas viscosity is computed from the correlations by Carr et al.

BIBLIOGRAPHY

• Sinha MK; Reservoir Engineering Techniques Using Fortran; IHRD Corp, Boston, 1985.
• Mian M.A.; Petroleum Engineering Handbook for the practicing Engineer; Penwell Publishing Co., Tulsa, Okl., 1992, vol 1, chap. 2.
• McCain Jr, W.D.; Properties Of Petroleum Fluids; Penwell Publishing Co., Tulsa, Oklahoma, 1990.