Original Oil in Place from General Oil Material Balance Formula
Original Oil in Place from General Oil Material Balance calculates original oil in place for material balance and production workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (F, W_e, E_o, m, E_g, E_fw) 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, N equals 400,000 STB.
631000
96440
1.15
0.2
0.8
0.0264
Inputs
F
RBUnderground Withdrawal
W_e
RBCumulative Water Influx
E_o
RB/STBOil and Dissolved Gas Expansion Term
m
dimensionlessInitial Gas Cap to Oil Zone Reservoir Volume Ratio
E_g
RB/STBGas Cap Expansion Term
E_fw
RB/STBConnate Water and Rock Expansion Term
Outputs
N
Original Oil in Place
F
Underground Withdrawal
W_e
Cumulative Water Influx
E_o
Oil and Dissolved Gas Expansion Term
m
Initial Gas Cap to Oil Zone Reservoir Volume Ratio
E_g
Gas Cap Expansion Term
E_fw
Connate Water and Rock Expansion Term
Source and review
reviewedPetroleum Office. Oil Reservoir Material Balance; Havlena-Odeh general oil MBE.
Source