Gas Cap Shrinkage from Gas Cap Production Formula
Gas Cap Shrinkage from Gas Cap Production calculates gas cap shrinkage for material balance and production workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (G_pc, B_g, m, N, B_oi, B_gi) 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, G_s equals 60,000 bbl.
30000000
0.006
0.2
1000000
1.2
0.004
Inputs
G_pc
SCFCumulative Gas Production from Gas Cap
B_g
bbl/SCFCurrent Gas Formation Volume Factor
m
fractionGas Cap Ratio
N
STBOil in Place
B_oi
bbl/STBInitial Oil Formation Volume Factor
B_gi
bbl/SCFInitial Gas Formation Volume Factor
Outputs
G_s
Gas Cap Shrinkage
G_pc
Cumulative Gas Production from Gas Cap
B_g
Current Gas Formation Volume Factor
m
Gas Cap Ratio
N
Oil in Place
B_oi
Initial Oil Formation Volume Factor
B_gi
Initial Gas Formation Volume Factor
Source and review
reviewedAdvanced Reservoir Engineering, Ahmed, T., McKinney, P. D. (2005)
Ahmed, T. and McKinney, P. D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter 5, Page 333.
Source