Undersaturated oil formation volume factor	B_o	bbl/stb	p > p_b	$\begin{array}{l}\displaystyle B_o(p, T) = B_{ob} \cdot \exp \left[ A \cdot ( p_b^{c_6} -p^{c_6} ) \right]\end{array}$ $\begin{array}{l}A = с_1 \cdot R_{sb}^{c_2} \cdot \gamma_g^{c_3} \cdot \gamma_{API}^{c_4} \cdot T^{c_5}\end{array}$ $\begin{array}{l}c_1 = 4.16463 \cdot 10^{−7} \ , \ c_2 = 0.69357 \ , \ c_3 = 0.1885 \ , \ c_4 = 0.3272 \ , \ c_5 = 0.6729 \ , \ c_6 = 0.4094\end{array}$

where

$\begin{array}{l}B_{ob}\end{array}$	bbl/stb	Formation volume factor at bubble point pressure p_b
$\begin{array}{l}p\end{array}$	psia	Fluid pressure
$\begin{array}{l}T\end{array}$	°F	Initial formation temperature
$\begin{array}{l}\gamma_{API}\end{array}$	°API	Oil API gravity
$\begin{array}{l}\gamma_o\end{array}$	frac	Oil specific gravity
$\begin{array}{l}\gamma_g\end{array}$	frac	Gas specific gravity

References

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