When oil is brought to surface conditions it is usual for some gas to come out of solution. The ratio of a given volume of gas at standard pressure and temperature (STP) to a given volume of produced oil. Gas Oil Ratio is also known as the GOR and could have gas units of SCF, MSCF, or MMSCF and oil units of barrels.
It is used as a measure of the amount of gas that is produced per barrel of oil. For example, a well producing 25 bpd with a GOR of 108 would have a gas volume flow rate of 2,700 scfd.