Geoscience Reference
In-Depth Information
2
PROPERTIES OF RESERVOIR GASES
The reservoir gas properties of interest in petroleum engineering are
the following:
1. Gas z-factors
2. Gas densities
3. Gas formation volume factors
4. Gas viscosities
5. Coefficient of isothermal compressibility of gas
6. Real gas pseudopressures
Gas Correlations
There are only two correlations in this chapter: gas z-factor and gas
viscosity. All other gas properties are calculated from gas z-factors. In
fact, the value of gas density required in the gas viscosity correlation is
calculated using gas z-factor.
Two choices are available to describe a gas of interest: gas specific
gravity or gas composition. The assumption is that gas composition
is not available, i.e., results of a laboratory study are not available. The
accuracies of the predicted fluid properties are about the same regardless
of the choice between correlations based on gas specific gravity or
correlations based on gas composition. Gas specific gravity can readily
be calculated given gas composition.
The input data for the correlation equations in this chapter
will be reservoir gas specific gravities and the compositions of
nonhydrocarbons in mole fractions, along with reservoir temperatures
and selected pressures. If the reservoir gas is a dry gas, i.e., no petroleum
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