Instantaneous Gas-Oil Ratio Formula
Instantaneous Gas-Oil Ratio calculates instantaneous gas-oil ratio for pvt properties workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (R_s, k_rg, k_ro, mu_o, mu_g, B_o, B_g) are known and the assumptions behind the cited pvt properties 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, GOR equals 3,600 SCF/STB.
600
0.05
0.4
2
0.02
1.2
0.005
Inputs
R_s
SCF/STBSolution Gas-Oil Ratio
k_rg
dimensionlessRelative Gas Permeability
k_ro
dimensionlessRelative Oil Permeability
mu_o
cPOil Viscosity
mu_g
cPGas Viscosity
B_o
bbl/STBOil Formation Volume Factor
B_g
bbl/SCFGas Formation Volume Factor
Outputs
GOR
Instantaneous Gas-Oil Ratio
R_s
Solution Gas-Oil Ratio
k_rg
Relative Gas Permeability
mu_o
Oil Viscosity
B_o
Oil Formation Volume Factor
k_ro
Relative Oil Permeability
mu_g
Gas Viscosity
B_g
Gas Formation Volume Factor
Source and review
reviewedAhmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter 1, Page 16.
Source