Reservoir EngineeringReservoir Volumetrics
Original Gas in Place - Volumetric Method Formula
Original Gas in Place - Volumetric Method calculates original gas in place for reservoir volumetrics workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (A, h, phi, S_wi, B_gi) are known and the assumptions behind the cited reservoir volumetrics 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, G equals 7,840,800,000 SCF.
Aacres
160
hft
50
phifraction
0.15
S_wifraction
0.25
B_gift³/SCF
0.005
Inputs
A
acresReservoir Area
h
ftAverage Reservoir Thickness
phi
fractionPorosity
S_wi
fractionInitial Water Saturation
B_gi
ft³/SCFInitial Gas Formation Volume Factor
Outputs
G
SCF
Original Gas in Place
A
acres
Reservoir Area
h
ft
Average Reservoir Thickness
phi
fraction
Porosity
S_wi
fraction
Initial Water Saturation
B_gi
ft³/SCF
Initial Gas Formation Volume Factor
Source and review
reviewedAhmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter 3, Page 202.
Source