oil_viscosity
Calculate oil viscosity at reservoir conditions using the Beggs-Robinson correlation to analyze flow rates, pressure drops, and recovery efficiency in petroleum engineering.
Instructions
Calculate oil viscosity (μo).
CRITICAL PVT PROPERTY - Computes oil viscosity at reservoir conditions. Viscosity affects flow rates, pressure drops, and recovery efficiency. Uses Beggs-Robinson (1975) correlation, industry standard for oil viscosity.
Parameters:
api (float, required): Oil API gravity in degrees. Valid: 0-100. Example: 35.0. Higher API = lighter oil = lower viscosity.
degf (float, required): Reservoir temperature in °F. Valid: -460 to 1000. Example: 180.0. Higher temperature = lower viscosity.
p (float or list, required): Pressure(s) in psia. Must be > 0. Can be scalar or array. Example: 3000.0 or [2000, 3000, 4000].
pb (float, optional, default=0.0): Bubble point pressure in psia. Required for accurate calculation. Example: 3500.0.
rs (float or list, optional, default=0.0): Solution GOR at pressure p in scf/stb. If 0, will be calculated. Must match p shape. Example: 600.0.
rsb (float, optional, default=0.0): Solution GOR at bubble point in scf/stb. Required if pb provided. Example: 800.0.
method (str, optional, default="BR"): Correlation method. Only "BR" available.
Viscosity Behavior:
p < pb: Viscosity decreases with pressure (more gas dissolves, oil thins)
p = pb: Viscosity reaches minimum (μob, typically 0.5-5 cP)
p > pb: Viscosity increases with pressure (oil compression)
Typical Ranges:
Light oils (API > 35): 0.5-2 cP at bubble point
Medium oils (API 25-35): 1-10 cP at bubble point
Heavy oils (API < 25): 10-1000+ cP at bubble point
Returns: Dictionary with:
value (float or list): Viscosity in cP (matches input p shape)
method (str): "BR" (Beggs-Robinson)
units (str): "cP"
inputs (dict): Echo of input parameters
Common Mistakes:
Not providing rs when p < pb (will calculate incorrectly)
Using dead oil viscosity instead of live oil viscosity
Temperature in Celsius instead of Fahrenheit
Pressure in barg/psig instead of psia
Example Usage:
{
"api": 35.0,
"degf": 180.0,
"p": [2000, 3000, 4000],
"pb": 3500.0,
"rs": [400, 600, 800],
"rsb": 800.0,
"method": "BR"
}Result: Viscosity decreases from ~1.2 cP at 2000 psia to ~0.8 cP at 3500 psia, then increases to ~0.85 cP at 4000 psia (above bubble point).
Note: Viscosity is highly sensitive to temperature and dissolved gas content. Always use reservoir temperature, not separator temperature.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| request | Yes |
Output Schema
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||