Effect of Temperature on Waterflooding

This paper describes laboratory experiments involving waterflooding atelevated temperatures using two refined oils and two crudes. The test core andinjection water were both held at test temperatures for the duration of theflood, thus eliminating the problem of thermal fronts. The findings reportedhere apply to waterflooding in general and thermal recovery in particular, asmost thermal recovery methods include a phase where "hot" water displaces "hot"oil. Waterflood tests were conducted at 75°F, 100°F, 150° F, 200°F, 300°F, 400°Fand 500°F using two refined oils: No. 5 white oil and No. 15 white oil. Twocrude oils were used in waterflooding at 75°F, 150°F and 300°F. The results show that residual oil saturation decreases with increasing temperature. Consequently, ultimate oil recovery increases with increasingtemperature and the relative permeability ratio is different for differenttemperatures. The magnitude of the temperature effect varies, but in most casesit is appreciable, especially for the crude oils. Crude oil waterfloodbehaviour in the laboratory tests differs significantly from refined oilbehaviour, because in crude oil waterfloods water breakthrough is earlier andsubordinate production is much higher. Consequently, predictions of field hotwaterfloods require displacement data at the actual field flood temperature, using reservoir materials. Introduction There is a great deal of current interest in thermal methods for recoveringcrude oil, especially the heavy viscous crudes. Many forms of thermal recoveryinclude a phase where hot water displaces oil. In such a process, two frontswill form a leading cold-water front and a hot-water front. Oil and waterviscosities decrease and the liquids swell as the temperature increases. These effects may influence fluid flow in a way not described by simple relativepermeability concepts. However, all processes involved in hot waterfloodingoccur slowly, and thermal equilibrium may be considered to prevail at everyspace-time point during the flood. Consequently, the relative flow rates of oiland water are determined by relative permeability ratios and viscosities, despite the complicating thermal effects mentioned above.