Reservoir EngineeringMaterial Balance
Modified Cole Plot for Water-Drive Gas Reservoirs Formula
Modified Cole Plot for Water-Drive Gas Reservoirs calculates fluid withdrawal divided by total expansion term for material balance workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (G, W_e, E_t) are known and the assumptions behind the cited material balance 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, F_over_Et equals 1,020,000,000 SCF.
GSCF
1000000000
W_ebbl
100000
E_tbbl/SCF
0.005
Inputs
G
SCFGas in Place
W_e
bblCumulative Water Influx
E_t
bbl/SCFTotal Expansion Term
Outputs
F_over_Et
SCF
Fluid Withdrawal Divided by Total Expansion Term
G
SCF
Gas in Place
W_e
bbl
Cumulative Water Influx
E_t
bbl/SCF
Total Expansion Term
Source and review
reviewedAhmed, T. and McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter 3, Page 212.
Source