Steam oil ratio:  Parameter used to monitor the efficiency of oil production processes based on steam injection. Commonly abbreviated as SOR, it measures the volume of steam required to produce one unit volume of oil. Typical values of SOR for cyclic steam stimulation are in the range of three to eight, while typical SOR values for steam assisted gravity drainage are in the range of two to five. The lower the SOR, the more efficiently the steam is utilized and the lower the associated fuel costs.