Oil Reservoir Underground Withdrawal Formula
Oil Reservoir Underground Withdrawal calculates underground withdrawal for material balance and production workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (N_p, B_o, R_p, R_s, B_g, W_p, B_w) 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, F equals 631,000 RB.
200000
1.15
900
550
0.005
50000
1.02
Inputs
N_p
STBCumulative Oil Production
B_o
RB/STBOil Formation Volume Factor
R_p
scf/STBCumulative Producing Gas-Oil Ratio
R_s
scf/STBSolution Gas-Oil Ratio at Current Pressure
B_g
RB/scfGas Formation Volume Factor
W_p
STBCumulative Water Production
B_w
RB/STBWater Formation Volume Factor
Outputs
F
Underground Withdrawal
N_p
Cumulative Oil Production
B_o
Oil Formation Volume Factor
R_p
Cumulative Producing Gas-Oil Ratio
R_s
Solution Gas-Oil Ratio at Current Pressure
B_g
Gas Formation Volume Factor
W_p
Cumulative Water Production
B_w
Water Formation Volume Factor
Source and review
reviewedPetroleum Office. Underground Withdrawal and Expansion Terms; Havlena and Odeh material balance notation.
Source