Oil Material Balance Drive Index Closure Formula
Oil Material Balance Drive Index Closure calculates drive index sum for material balance and production workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (N, E_o, m, E_g, W_e, E_fw, F) 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, DI_sum equals 1 fraction.
400000
1.15
0.2
0.8
96440
0.0264
631000
Inputs
N
STBOriginal Oil in Place
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
W_e
RBCumulative Water Influx
E_fw
RB/STBConnate Water and Rock Expansion Term
F
RBUnderground Withdrawal
Outputs
DI_sum
Drive Index Sum
DDI
Depletion Drive Index
GDI
Gas Cap Drive Index
WDI
Water Drive Index
CDI
Compaction Drive Index
Source and review
reviewedPetroleum Office. Material Balance Overview; drive mechanism identification and drive indices.
Source