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.