Usually produced from subsurface gas phase and oil phase.

It usually requires additional processing before taking commercial form of the Natural Gas.

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

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

where

$\begin{array}{l}B_o, B_g\end{array}$	oil formation volume factor between separator and sandface pressure/temperature conditions
$\begin{array}{l}R_s\end{array}$	Solution GOR at sandface pressure/temperature conditions

The gas surface flowrate $\begin{array}{l}q_G\end{array}$ relates to Surface Liquid production rate $\begin{array}{l}q_L\end{array}$ as:

(2)	$\begin{array}{l}\displaystyle q_G^{\uparrow} = Y_G \cdot (1-Y_w) \, q_L^{\uparrow}\end{array}$

The gas surface flowrate $\begin{array}{l}q_G^{\uparrow}\end{array}$ relates to Total sandface flowrate $\begin{array}{l}q_t\end{array}$ as:

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

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

(4)	$\begin{array}{l}\displaystyle q_G^{\uparrow} =\frac{q_g}{B_g} +\frac{R_s \, q_o}{B_o} = Y_G \cdot (1-Y_w) \, q_L = \frac{ Y_G \cdot (1-Y_W)}{B_w Y_W + \left[ (B_o - R_s B_g) + B_g \, Y_G \right] \cdot (1-Y_W)} \cdot q_t\end{array}$

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