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:
- Calculation of viscosity at atmospheric pressure.
- 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