The pump size is determined by the total volumetric flow rate at the suction condition. To estimate this total flow rate one needs to determine the Gas Volume Fraction (GVF) or the Gas liquid Ratio (GLR) at suction conditions.

Terms in use are summarised here:

• GOR: measure of gas quantity in a well stream  expressed in standard cubic  feet of gas per barrel of oil, scf/bbl  (Sm3/m3). The standard conditions are generally a temperature of 60°F (15°C) and a pressure of 14.7 psia   (1 bar abs).
• GVF: ratio of volume of gas to that of the total volume of the effluent (oil, water and gas) at pump suction temperature and pressure, expressed in volume/volume (bbl/bbl or m3/m3).
• GLR: ratio of the volume of gas to the volume of total liquid (oil and water) only.
• WC: ratio of the volume of water to the volume of total liquid.
  

The following interrelationships can be used:

• rough approximation: GLR  @  GOR ´ (1-WC) ´ [(460 + temperature in °F) / 520] ´ (14.7 / absolute pressure in psia)/ (5.615   cft/bbl)
• exact:  GVF = GLR / (1+GLR)

Example:

GOR = 560 scf/bbl

WC = 0.50

Suction temperature = 100 °F

Suction pressure = 147 psia

The approximation  becomes:  GLR @ 5. 37 vol/vol,  hence: GVF @  84.30 %.

The approximation does not take into account the phase changes between the gas and the oil and therefore is inaccurate. Nevertheless it is a first evaluation when no other data (effluent composition) is available.