Page 43 - Handbook of Natural Gas Transmission and Processing Principles and Practices
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(1.22)
If the relationship between the Z factor and pressure at a given temperature is known, we can
calculate the compressibility of gas. Since we already know the relationship between Z and P, we
can numerically calculate the derivative and, hence, the value of the compressibility.
1.6.1.6. Gas Viscosity
A number of methods have been developed to calculate gas viscosity. The method of Lee et al.
(1966) is a simple relation which gives quite accurate results for typical natural gas mixtures with
low nonhydrocarbon content. The Lee et al. (1966) correlation was evaluated by Jeje and Mattar
(2004) and has the following form:
(1.23)
where:
(1.24)
(1.25)
(1.26)
3
In this expression, temperature is given in (°R), the density of the gas in lbm/ft (calculated at the
pressure and temperature of the system), and the resulting viscosity is expressed in centipoises (c ).
p
The viscosity of gas mixtures at 1 atm and reservoir temperature can be determined from the
gas mixture composition:
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