Input Parameters
History
| # | Timestamp | System | P | T | z | Psc | Tsc | Bg ft³/scf | Bg rb/scf | Bg m³/Sm³ |
|---|---|---|---|---|---|---|---|---|---|---|
| No history yet. Calculate to populate. | ||||||||||
Example Data
| System | P | T | z | Psc | Tsc | Bg ft³/scf | Bg rb/scf | Bg m³/Sm³ |
|---|---|---|---|---|---|---|---|---|
| US | 3000 psia | 180 °F | 0.85 | 14.7 psia | 60 °F | 0.005127 | 0.000913 | 0.000145 |
| SI | 20000 kPa | 90 °C | 0.90 | 101.325 kPa | 15 °C | 0.005746 | 0.036141 | 0.005746 |
Formula Used
Definition The gas formation volume factor, Bg, is the ratio of a gas volume at reservoir conditions to its volume at standard conditions.
Equation: Bg = z × (T / Tsc) × (Psc / P), where P and T are absolute pressure and temperature at reservoir conditions, Psc, Tsc are absolute standard conditions, and z is the gas deviation factor.
Units: The equation is unitless if P and Psc share units and T and Tsc are absolute. Report as ft³/scf, rb/scf, or m³/Sm³ via conversion.
How to Use This Calculator
- Select the system matching your inputs: US or SI.
- Enter reservoir pressure and temperature. Use absolute values where applicable.
- Enter the gas deviation factor z from lab or correlations.
- Set standard conditions Psc and Tsc or use quick presets.
- Press Calculate Bg to compute and log results to history.
- Export the history using Download CSV or Download PDF.
Tip: For US inputs in °F, the calculator converts to °R internally. For SI in °C, it converts to Kelvin.
Bg vs Pressure (T and z constant)
Lower pressure increases Bg linearly via the Psc/P term, holding temperature and z constant.
| Pressure | Bg (ft³/scf) | Bg (rb/scf) |
|---|---|---|
| 1,000 psia | 0.015380 | 0.002739 |
| 2,000 psia | 0.007690 | 0.001370 |
| 3,000 psia | 0.005127 | 0.000913 |
| 4,000 psia | 0.003845 | 0.000685 |
| 5,000 psia | 0.003076 | 0.000548 |
Bg vs Temperature (P and z constant)
Higher temperature increases Bg linearly via the T/Tsc ratio when using absolute temperatures.
| Temperature | Bg (ft³/scf) | Bg (rb/scf) |
|---|---|---|
| 100 °F | 0.004486 | 0.000799 |
| 140 °F | 0.004806 | 0.000856 |
| 180 °F | 0.005127 | 0.000913 |
| 220 °F | 0.005447 | 0.000970 |
| 260 °F | 0.005768 | 0.001027 |
Bg vs z-Factor (P and T constant)
Bg scales directly with z. Real gas effects increase Bg compared to the ideal gas case.
| z | Bg (ft³/scf) | Bg (rb/scf) |
|---|---|---|
| 0.70 | 0.004222 | 0.000752 |
| 0.85 | 0.005127 | 0.000913 |
| 1.00 | 0.006031 | 0.001074 |