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.
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