Hydrocarbon gas pseudocritical pressure and temperature

A3.3 Pseudocritical Pressure and Temperature of Pure Hydrocarbon Gas#

A3.3.1 Dry Gas#

Brown

The Brown correlation is a classical method for estimating pseudocritical pressure and temperature. The model is widely used in the oil and gas industry due to its simplicity and acceptable accuracy under standard conditions. The correlation is applicable only for calculating properties of dry gas. 
Recommended applicability range:

• Gas specific gravity (air = 1): 0.55 – 1
• C ₇⁺ content: < 1%

Dùn & Oriji

The Dùn & Oriji correlation was developed for more accurate calculation of the pseudocritical pressure of dry natural gases, based on modern datasets. The method is derived from statistical analysis of an extensive PVT database from African and Middle Eastern fields. The correlation does not account for the influence of heavy hydrocarbons. 
Recommended applicability range:

• Gas specific gravity (air = 1): 0.55 – 0.8

Golan & Whitson

The Golan & Whitson method offers an improved approach for determining the pseudocritical pressure and temperature of dry natural gases. The correlation is based on a modification of the classic Standing-Katz method, incorporating the molecular weight of the gas. It shows better accuracy compared to traditional methods when applied to gases containing minor non-hydrocarbon impurities. 
Recommended applicability range:

• Gas specific gravity (air = 1): 0.55 – 0.8

Thomas, Hankinson & Phillips 

The Thomas, Hankinson & Phillips correlation estimates pseudocritical pressure and temperature values for dry natural gases. It is suitable for typical natural gases without significant concentrations of non-hydrocarbon components. It is not applicable to gases with a specific gravity (air = 1) greater than 0.8. 
Recommended applicability range:

• Gas specific gravity (air = 1): 0.55 – 0.8
• C ₄ + content: > 90%

Joshi

The Joshi correlation offers a modernized approach to calculating pseudocritical pressure and temperature for dry and slightly sour gases. The method is based on a comprehensive global dataset. Its key advantage is high accuracy for gases with atypical compositions, without requiring complex corrections. 
Recommended applicability range:

• Gas specific gravity (air = 1): 0.55 – 0.8

Lee & Wattenbarger

The Lee & Wattenbarger correlation was developed for accurate calculation of pseudocritical pressure and temperature for dry natural gases. The method is a modification of classical approaches, incorporating gas thermodynamics. It is based on research from reservoirs around the world. A key feature is the use of separate calculation formulas for different gas specific gravity ranges. 
Recommended applicability range:

• Gas specific gravity (air = 1): 0.55 – 1.1

Golan & Whitson

The Golan & Whitson correlation is designed to calculate the pseudocritical pressure and temperature of wet hydrocarbon gases containing significant amounts of heavy fractions. The method is based on gas mixing rules, accounting for the influence of molecular weight and gas composition, which ensures high accuracy for gas-condensate systems. 
Recommended applicability range:

• Gas specific gravity (air = 1): 0.6 – 1.2
• C ₇⁺ content: 1 – 20%