Formation Volume Factor (FVF) for gas:
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B_g(p,T) = \frac{\rho_g^mathring{\circrho}_g}{\rho_g} = \frac{V_g}{\mathring{V}_g^{\circGg}} = \frac{q_g}{q_{Gg}} |
where
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| body | --uriencoded--\rho_g%5e%7B\circ%7D |
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| fluid density at surface reference conditions | | LaTeX Math Inline |
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| body | --uriencoded--V_m%5e%7B\circ%7D |
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| molar volume at surface at reference conditions |
| fluid density at reservoir conditions | | molar volume at reservoir conditions |
The reference conditions may vary from case to case but most popular choice are: Separator, Stock Tank and SPE STP.
It can be expressed through the Z-factor as:
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| anchor | XALSKBgRef |
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| alignment | left |
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B_g(p,T) = \frac{Z(p, T)}{Z^{\circ}} \cdot \frac{T/T_T^{\rm refcirc}}{p/p_p^{\rm refcirc}} |
where
p_%7B\rm ref%7D | reference pressure |
| reservoir temperature | | LaTeX Math Inline |
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| body | --uriencoded--T%5e%7B\circ%7D |
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| reference temperature |
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| body | --uriencoded--Z%5e%7B\circ%7D = Z(T%5e%7B\circ%7D, \, p%5e%7B\circ%7D) |
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| Z-factor at reference conditions |
If reference conditions are set at SPE STP then reference Z-factor
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| body | --uriencoded--Z%5e%7B\circ%7D = 1 |
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is close to 1 for all natural gases and equation | LaTeX Math Block Reference |
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takes explicit form as:| LaTeX Math Block |
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B_g(p,T) = 0.3470 \cdot Z(p, T) \cdot \frac{T}{p} |
where
_%7B\rm ref%7Dreference temperature
See Also
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Petroleum Industry / Upstream / Subsurface E&P Disciplines / Fluid (PVT) Analysis / Dynamic fluid properties
[ Formation Volume Factor (FVF) ][ Oil formation volume factor (Bo) ][ Water formation volume factor (Bw) ]
