Gas Expansion Factor from Cumulative Gas Production Formula
Gas Expansion Factor from Cumulative Gas Production calculates current gas expansion factor for material balance workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (E_gi, A, h, phi, S_wi, G_p) 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, E_g equals 179.701083 SCF/ft^3.
180
640
50
0.16
0.25
50000000
Inputs
E_gi
SCF/ft^3Initial Gas Expansion Factor
A
acresDrainage Area
h
ftReservoir Thickness
phi
fractionPorosity
S_wi
fractionInitial Water Saturation
G_p
SCFCumulative Gas Production
Outputs
E_g
Current Gas Expansion Factor
E_gi
Initial Gas Expansion Factor
G_p
Cumulative Gas Production
Source and review
reviewedAdvanced Reservoir Engineering, Ahmed, T., McKinney, P. D. (2005)
Ahmed, T. and McKinney, P. D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter 3, Page 202.
Source