Non-hydrocarbon impurity pseudocritical properties

A3.4 Pseudocritical Pressure and Temperature of Non-Hydrocarbon Impurities#

Carr

The Carr correlation allows correction of the pseudocritical pressure and temperature of natural gas in the presence of non-hydrocarbon impurities. The method is especially useful for fields with high concentrations of acid gases, where standard methods produce significant errors. 
Recommended applicability range:

• Gas specific gravity (air = 1): 0.55 – 1.2
• CO ₂ content: < 20%
• H ₂ S content: < 25%
• N ₂ content: < 5%

Piper & McCain

The Piper & McCain correlation is an advanced method for determining pseudocritical properties of gas-condensate mixtures containing non-hydrocarbon components. It was developed based on an extensive database from North Sea fields. The model provides high accuracy for complex multicomponent systems. 
Recommended applicability range:

• Gas specific gravity (air = 1): 0.55 – 1.2
• CO ₂ content: < 20%
• H ₂ S content: < 30%
• N ₂ content: < 10%

Wichert & Aziz

The Wichert & Aziz correlation is a fundamental method for adjusting pseudocritical properties of natural gases with elevated levels of acid gases. The method accounts for the non-ideal behavior of such mixtures and ensures accuracy in the calculation of the gas compressibility factor. It is not applicable to gases with a high content of heavy hydrocarbons (C ₇⁺ > 5%). 
Recommended applicability range:

• Gas specific gravity (air = 1): 0.55 – 1.0
• CO ₂ content: < 40%
• H ₂ S content: < 40%