gas_viscosity
Calculate gas viscosity at reservoir conditions using the Lee-Gonzalez-Eakin correlation for accurate flow rate and pressure drop analysis in petroleum engineering.
Instructions
Calculate gas viscosity (μg).
CRITICAL GAS PVT PROPERTY - Computes gas viscosity at reservoir conditions using Lee, Gonzalez & Eakin (1966) correlation, industry standard for natural gas. Viscosity affects flow rates, pressure drops, and well performance. Gas viscosity increases with pressure and temperature, opposite to liquid behavior.
Parameters:
sg (float, required): Gas specific gravity (air=1.0). Valid: 0.55-3.0. Typical: 0.6-1.2. Example: 0.7.
degf (float, required): Reservoir temperature in °F. Valid: -460 to 1000. Typical: 100-400°F. Example: 180.0.
p (float or list, required): Pressure(s) in psia. Must be > 0. Can be scalar or array. Example: 3500.0 or [1000, 2000, 3000, 4000].
h2s (float, optional, default=0.0): H2S mole fraction (0-1). Typical: 0-0.05. Example: 0.02.
co2 (float, optional, default=0.0): CO2 mole fraction (0-1). Typical: 0-0.20. Example: 0.05.
n2 (float, optional, default=0.0): N2 mole fraction (0-1). Typical: 0-0.10. Example: 0.01.
zmethod (str, optional, default="DAK"): Z-factor method for viscosity calculation. Options: "DAK", "HY", "WYW", "BUR". DAK recommended.
Viscosity Behavior:
Increases with pressure (gas molecules closer together)
Increases with temperature (molecular motion increases)
Typical range: 0.01-0.05 cP at reservoir conditions
At standard conditions: ~0.01 cP
Lee-Gonzalez-Eakin Correlation: Uses Z-factor internally to account for real gas behavior. More accurate than ideal gas assumptions, especially at high pressures.
Returns: Dictionary with:
value (float or list): Viscosity in cP (matches input p shape)
method (str): "Lee-Gonzalez-Eakin"
units (str): "cP"
inputs (dict): Echo of input parameters
Common Mistakes:
Using separator temperature instead of reservoir temperature
Pressure in barg/psig instead of psia (must be absolute)
Not accounting for non-hydrocarbon fractions
Confusing gas viscosity (increases with P) with oil viscosity (decreases with P)
Temperature in Celsius instead of Fahrenheit
Example Usage:
{
"sg": 0.7,
"degf": 180.0,
"p": [1000, 2000, 3000, 4000],
"h2s": 0.0,
"co2": 0.05,
"n2": 0.01,
"zmethod": "DAK"
}Result: Viscosity increases from ~0.012 cP at 1000 psia to ~0.025 cP at 4000 psia.
Note: Gas viscosity is much lower than oil viscosity (typically 0.01-0.05 cP vs 0.5-10 cP). Always use reservoir conditions, not separator conditions. Account for all non-hydrocarbon components for accuracy.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| request | Yes |
Output Schema
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||