Volumetric flowrate of mostly degasified oil normally measured at separator or at processing plant.

Usually produced from subsurface oil phase and gas phase.

It usually requires additional processing before taking commercial form of the Crude Oil.

For volatile oil fluid model the oil surface flowrate $\begin{array}{l}q_O\end{array}$ is related to oil sandface flowrate $\begin{array}{l}q_o\end{array}$ and gas sandface flowrate $\begin{array}{l}q_g\end{array}$ as (see derivation):

(1)	$\begin{array}{l}\displaystyle q_O =(1-R_v \, R_s)^{-1} \left( \frac{q_o}{B_o} +\frac{R_v \, q_g}{B_g} \right)\end{array}$

where

$\begin{array}{l}B_o, B_g\end{array}$	oil formation volume factor between separator and sandface pressure/temperature conditions
$\begin{array}{l}R_v\end{array}$	Vaporized Oil Ratio at sandface pressure/temperature conditions

It relates to Surface Liquid production rate $\begin{array}{l}q_L\end{array}$ and Total sandface flowrate $\begin{array}{l}q_t\end{array}$ as:

(2)	$\begin{array}{l}\displaystyle q_O = (1-Y_W) \cdot q_L\end{array}$

(3)	$\begin{array}{l}\displaystyle q_O = \frac{(1-Y_W)}{B_w Y_W + \left[ (B_o - R_s B_g) + (B_g - R_v B_o) \, Y_G \right] \cdot (1-Y_W)} \cdot q_t\end{array}$

It simplifies for the Black Oil model ( $\begin{array}{l}R_v = 0\end{array}$ ) to:

(4)	$\begin{array}{l}\displaystyle q_O = \frac{q_o}{B_o}\end{array}$

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