Cumulative Gas Production – Tarner’s Method Formula
Cumulative Gas Production – Tarner’s Method calculates cumulative gas production for material balance and production workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (N, Rsi, Rs, Boi, Bo, Bg, Np) 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, Gp equals 416,000,000 SCF.
1000000
800
400
1.2
1.1
0.005
200000
Inputs
N
STBInitial Oil-in-Place
Rsi
SCF/STBInitial Gas Solubility
Rs
SCF/STBGas Solubility at Current Conditions
Boi
bbl/STBOil FVF at Initial Reservoir Pressure
Bo
bbl/STBOil FVF at Current Reservoir Pressure
Bg
bbl/SCFGas Formation Volume Factor at Current Reservoir Pressure
Np
STBCumulative Oil Production
Outputs
Gp
Cumulative Gas Production
N
Initial Oil-in-Place (rearranged)
Rsi
Initial Gas Solubility (rearranged)
Rs
Gas Solubility at Current Conditions (rearranged)
Boi
Oil FVF at Initial Pressure (rearranged)
Bo
Oil FVF at Current Pressure (rearranged)
Bg
Gas Formation Volume Factor (rearranged)
Np
Cumulative Oil Production (rearranged)
Source and review
reviewedAhmed, T., McKinney, P.D. (2005). Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter: 5, Page: 340.
Source