Reservoir EngineeringPermeability and Flow
Torcaso-Wyllie Relative Permeability Ratio Prediction Formula
Torcaso-Wyllie Relative Permeability Ratio Prediction calculates oil relative permeability ratio prediction for permeability and flow workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (S_o, S_wi, k_rg) are known and the assumptions behind the cited permeability and flow relationship match the engineering case being checked.
Assumptions
- Input values are representative for the well, reservoir, fluid, or equipment case being evaluated.
- The declared units match the field-unit constants used in the formula.
- The cited formula applies to the selected petroleum engineering workflow.
Limitations
- The calculation does not replace a full engineering model or operating procedure.
- Accuracy depends on the source correlation, assumptions, input quality, and unit consistency.
Common mistakes
- Mixing unit systems without converting the inputs.
- Using default example values as field recommendations.
- Applying the formula outside the source assumptions.
Default example
Using the default inputs, k_og equals 0.015625 dimensionless.
S_ofraction
0.5
S_wifraction
0.25
k_rgdimensionless
0.05
Inputs
S_o
fractionOil Saturation
S_wi
fractionInitial Water Saturation
k_rg
dimensionlessGas Relative Permeability
Outputs
k_og
dimensionless
Oil Relative Permeability Ratio Prediction
S_tw
fraction
Torcaso-Wyllie Normalized Oil Saturation
S_o
fraction
Oil Saturation
S_wi
fraction
Initial Water Saturation
k_rg
dimensionless
Gas Relative Permeability
Source and review
reviewedAhmed, T. and McKinney, P.D. Advanced Reservoir Engineering, Gulf Publishing House, 2015.
Source