Gas Cap Ratio Formula
Gas Cap Ratio calculates gas cap ratio for material balance and production workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (G, B_gi, N, B_oi) are known and the assumptions behind the cited material balance and production 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, m equals 2 dimensionless.
500000000
0.005
1000000
1.25
Inputs
G
SCFInitial Gas Cap Volume
B_gi
bbl/SCFInitial Gas Formation Volume Factor
N
STBInitial Oil in Place
B_oi
bbl/STBInitial Oil Formation Volume Factor
Outputs
m
Gas Cap Ratio
G
Initial Gas Cap Volume
B_gi
Initial Gas Formation Volume Factor
N
Initial Oil in Place
B_oi
Initial Oil Formation Volume Factor
Source and review
reviewedAdvanced Reservoir Engineering, Ahmed, T., McKinney, P. (2015)
Ahmed, T. and McKinney, P. Advanced Reservoir Engineering, Gulf Publishing House, Burlington, MA, 2015, Chapter 4, Page 317.
Source