Phase Behavior and ThermodynamicsGas Properties

Papay Gas Z-Factor Correlation Formula

z=1-\frac{3.53P_{pr}}{10^{0.9813T_{pr}}}+\frac{0.274P_{pr}^2}{10^{0.8157T_{pr}}}

Papay Gas Z-Factor Correlation calculates gas compressibility factor for gas properties workflows in phase behavior and thermodynamics.

Calculate

How engineers use this formula

Use this formula when the listed inputs (P_pr, T_pr) are known and the assumptions behind the cited gas properties relationship match the engineering case being checked.

Assumptions

Input values are representative for the well, reservoir, fluid, or equipment case being evaluated.
The declared units match the field-unit constants used in the formula.
The cited formula applies to the selected petroleum engineering workflow.

Limitations

The calculation does not replace a full engineering model or operating procedure.
Accuracy depends on the source correlation, assumptions, input quality, and unit consistency.

Common mistakes

Mixing unit systems without converting the inputs.
Using default example values as field recommendations.
Applying the formula outside the source assumptions.

Default example

Using the default inputs, z equals 0.942199 dimensionless.

P_prdimensionless

T_prdimensionless

Inputs

P_pr

dimensionless

Pseudo-Reduced Pressure

T_pr

dimensionless

Pseudo-Reduced Temperature

Outputs

z

dimensionless

Gas Compressibility Factor

Source and review

reviewed

Papay, J. 1968. A termelestechnologiai parameterek valtozasa a gaztelepek muvelese soran; formula summarized in Bello and Musa 2020 comparative gas z-factor study.

Source