Gas viscosity

A3.2 Viscosity#

Carr

The classical Carr correlation provides an estimate of natural gas viscosity at atmospheric and reservoir conditions. The method includes two steps:

1. Calculation of viscosity at atmospheric pressure.
2. Correction for reservoir pressure and temperature. 
   This approach is simple and reliable but may show deviations when hydrogen sulfide (H ₂ S) is present.

Recommended applicability range:

• Gas specific gravity (air = 1): 0.55 – 1.55
• Temperature: 100 – 400 °F
• Pressure: < 10,000 psi

Lee

The Lee correlation is one of the most widely used methods for calculating natural gas viscosity. It combines ease of use with good accuracy across a broad range of conditions. The formula accounts for the effects of temperature, gas density, and molecular weight through dimensionless parameters. It is well-suited for gases containing a low proportion of non-hydrocarbon components. 
Recommended applicability range:

• Gas specific gravity (air = 1): 0.55 – 1.5
• Temperature: 100 – 340 °F
• Methane content (CH ₄ ): > 70%
• Pressure: 100 – 8000 psi

Dean & Stiel

The Dean & Stiel method is designed for calculating gas viscosity using reduced parameters and is particularly accurate at high pressures and for non-standard gas compositions (e.g., gases containing H ₂ S and CO ₂ ). The method is based on the principle of corresponding states. 
Recommended applicability range:

• Reduced pressure: 0.1 – 15
• Reduced temperature: 1 – 3
• Gas specific gravity (air = 1): 0.5 – 2
• Gas composition: no limitations