Gas expansion factor, abbreviated as \( E_g \), is a term used to describe how much a gas expands when it’s brought from reservoir conditions (high pressure and temperature) to surface conditions (typically lower pressure and temperature). It’s essentially a measure of the volume change of natural gas as it moves from the subsurface reservoir to the surface production facilities. It is particularly relevant when dealing with compressible fluids, where changes in pressure and temperature significantly affect the volume of the gas.
Gas Expansion Factor Formula |
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| \( E_g \;=\; E_{gi} - \dfrac{ 1 }{ 43560 \cdot A \cdot h \cdot n \cdot ( 1 - w_{is} ) } \cdot G_p \) | ||
| Symbol | English | Metric |
| \( E_g \) = Gas Expansion Factor | \(SCF \;/\; bbl\) | - |
| \( E_{gi} \) = Initial Gas Expansion Factor | \(SCF \;/\; bbl\) | - |
| \( A \) = Drainage Area | \(acres\) | - |
| \( h \) = Thickness | \(ft\) | - |
| \( n \) = Porosity | \(dimensionless\) | - |
| \( w_{is} \) = Initial Water Saturation | \(dimensionless\) | - |
| \( G_p \) = Gas Produced | \(SCF\) | - |
