$\begin{array}{l}T_{pc}\end{array}$	°R	pseudo-critical temperature of the fluid mixture
$\begin{array}{l}p_{pc}\end{array}$	psi	pseudo-critical pressure of the fluid mixture
$\begin{array}{l}\gamma_g\end{array}$	Dimensionless	Gas specific gravity (air = 1)

(1)	$\begin{array}{l}\displaystyle p_{pc} = 756.8 -131.07 \, \gamma_g - 3.6 \, \gamma_g^2\end{array}$

(2)	$\begin{array}{l}\displaystyle T_{pc} = 169.2 +349.5 \, \gamma_g - 74 \, \gamma_g^2\end{array}$

Sutton, 1985

$\begin{array}{l}0.57< \gamma_g < 1.68\end{array}$

H₂S = 0%

N₂ < 1%

CO₂ < 1%

High molecular weight gases, rich in heptanes

(3)	$\begin{array}{l}\displaystyle p_{pc} = 709.604 - 58.718 \, \gamma_g\end{array}$

(4)	$\begin{array}{l}\displaystyle T_{pc} = 170.491 +307.344 \, \gamma_g\end{array}$

Guo and Ghalambor (2005)

H₂S < 3%

N₂< 5%

Total inorganic compounds < 7%

(5)	$\begin{array}{l}\displaystyle p_{pc} = 667 - 15.0 \, \gamma_g - 37.5 \, \gamma_g^2\end{array}$

(6)	$\begin{array}{l}\displaystyle T_{pc} = 168 +325 \, \gamma_g - 12.5 \, \gamma_g^2\end{array}$

Standing, 1977

Total inorganic compounds = 0%

Low molecular weight California natural gases

(7)	$\begin{array}{l}\displaystyle p_{pc} = 706 - 51.7 \, \gamma_g - 11.1 \, \gamma_g^2\end{array}$

(8)	$\begin{array}{l}\displaystyle T_{pc} = 187 +330 \, \gamma_g - 71.5 \, \gamma_g^2\end{array}$

Standing, 1977

Total inorganic compounds = 0%

Low molecular weight California gas condensate

(9)	$\begin{array}{l}\displaystyle p_{pc} = 787.06 - 147.34 \, \gamma_g - 7.916 \, \gamma_g^2\end{array}$

(10)	$\begin{array}{l}\displaystyle T_{pc} = 149.18 +358.14 \, \gamma_g - 66.976 \, \gamma_g^2\end{array}$

Elsharkawy et al. (2000)

Retrograde gases and condensates

(11)	$\begin{array}{l}\displaystyle p_{pc} = 678 - 50\, (\gamma_g - 0.5) - 206.7 \, y_{N_2} + 440 \, y_{CO_2} + 606.7 \, y_{H_2S}\end{array}$

(12)	$\begin{array}{l}\displaystyle T_{pc} = 326 +315.7 \, (\gamma_g -0.5) - 240 \, y_{N_2} - 83.3 \, y_{CO_2} + 133.3 \, y_{H_2S}\end{array}$

Ahmed (1989)

Reference

Sutton, R.P. 1985. Compressibility Factors for High-Molecular-Weight Reservoir Gases. Presented at the SPE Annual Technical Conference and Exhibition, Las Vegas, Nevada, USA, 22-26 September. SPE-14265-MS. http://dx.doi.org/10.2118/14265-MS
Standing, M. B., Volumetric and Phase Behavior of Oil Field Hydrocarbon Systems, pp. 125–126. Dallas: Society of Petroleum Engineers, 1977.

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