Oil and Dissolved Gas Expansion Term Formula
Oil and Dissolved Gas Expansion Term calculates oil and dissolved gas expansion term for material balance and production workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (B_o, B_oi, R_si, R_s, B_g) 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, E_o equals 1.15 RB/STB.
1.15
1.25
800
550
0.005
Inputs
B_o
RB/STBOil Formation Volume Factor at Current Pressure
B_oi
RB/STBInitial Oil Formation Volume Factor
R_si
scf/STBInitial Solution Gas-Oil Ratio
R_s
scf/STBSolution Gas-Oil Ratio at Current Pressure
B_g
RB/scfGas Formation Volume Factor
Outputs
E_o
Oil and Dissolved Gas Expansion Term
B_o
Oil Formation Volume Factor at Current Pressure
B_oi
Initial Oil Formation Volume Factor
R_si
Initial Solution Gas-Oil Ratio
R_s
Solution Gas-Oil Ratio at Current Pressure
B_g
Gas Formation Volume Factor
Source and review
reviewedPetroleum Office. Underground Withdrawal and Expansion Terms; oil and dissolved gas expansion.
Source