Gas Formation Volume Factor Calculator
Enter z-factor, reservoir temperature, and reservoir pressure. The calculator returns gas formation volume factor.
Calculation context and source notes
Gas formation volume factor converts gas volume between reservoir conditions and standard surface conditions using pressure, temperature, and gas z-factor.
Use it in PVT, material-balance, gas-in-place, and reservoir engineering calculations that convert gas between reservoir and standard conditions. Recalculate Bg at each pressure and temperature state used in the model.
Solves for
B_g (ft³/SCF)
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Formula, variables, and sourceRelated source-backed guides
Formula, variables, and default calculation
Reproducible default result
With the default values shown below, the calculation returns B_g = 0.004806 ft³/SCF. Defaults demonstrate the implementation; they are not recommended field values.
0.85
600
3000
Input definitions
z
dimensionlessGas Compressibility Factor
T
°RReservoir Temperature
P
psiaReservoir Pressure
Output definitions
B_g
Gas Formation Volume Factor
z
Gas Compressibility Factor
T
Reservoir Temperature
P
Reservoir Pressure
Engineering use, assumptions, and limits
Use it in PVT, material-balance, gas-in-place, and reservoir engineering calculations that convert gas between reservoir and standard conditions. Recalculate Bg at each pressure and temperature state used in the model.
Assumptions
- Gas z-factor is known or estimated separately.
- Pressure and temperature units match the equation form.
- Gas behavior is represented by the real-gas relationship used by the formula.
Limitations
- Does not calculate z-factor from gas composition.
- Does not handle condensate dropout or compositional phase behavior.
Common mistakes
- Using Fahrenheit instead of absolute temperature where required.
- Mixing psia and psig.
- Using an assumed z-factor outside its valid pressure-temperature range.
Source and record status
Source metadata identifies the relationship implemented by the calculator. Check the cited edition, unit basis, and scope against the engineering case before operational use.
Ahmed, T. 2007. Equations of State and PVT Analysis, Natural Gas Properties, Equation 3-52.
Open source reference