Initial Gas In Place for Water-Drive Gas Reservoir Formula
Initial Gas In Place for Water-Drive Gas Reservoir calculates original gas in place for material balance workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (G_p, B_g, W_e, W_p, B_w, B_gi) 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, G equals 2,801,000,000 SCF.
1000000000
0.006
500000
100000
1.02
0.004
Inputs
G_p
SCFCumulative Gas Production
B_g
bbl/SCFGas Formation Volume Factor at Current Pressure
W_e
bblCumulative Water Influx
W_p
STBCumulative Water Production
B_w
bbl/STBWater Formation Volume Factor
B_gi
bbl/SCFInitial Gas Formation Volume Factor
Outputs
G
Original Gas In Place
G_p
Cumulative Gas Production
B_g
Gas Formation Volume Factor at Current Pressure
W_e
Cumulative Water Influx
W_p
Cumulative Water Production
B_w
Water Formation Volume Factor
B_gi
Initial Gas Formation Volume Factor
Source and review
reviewedAAPG Wiki. Reserves estimation, Material balance estimation for gas.
Source