The Effect of Temperature on Caustic Displacement of Crude Oil

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Abstract Laboratory studies were carried out to determine the effect that temperature has on the waterflood recovery of oil from a consolidated core with the use of a weak sodium hydroxide solution as the flooding agent. The reduction in interfacial tension of several crude oil - caustic systems was investigated to determine a caustic solution that would reduce the interfacial tension to a minimal value. The resulting 0.20 weight percent sodium hydroxide solution was thereby determined and used as the caustic waterflooding agent throughout the displacement tests. Displacement tests were conducted at temperatures of 130 degrees, 160 degrees and 190 degrees F with both distilled water and the weak sodium hydroxide solution as the flooding agent. The tests indicated that the addition of the sodium hydroxide to the displacing fluid increased the waterflood recovery over that obtained with water at all temperatures investigated. Introduction Improved recovery of oil by secondary recovery techniques is becoming most important as the cost of finding new reserves has continued to increase. The low gravity, viscous crude oil reservoirs typically exhibit low recoveries and offer potential for new methods of secondary recovery. Waterflooding of viscous oil reservoirs has been avoided in the past as the displacement mechanism under such reservoir conditions has rarely been economically successful. Cyclic steam stimulation has proven to be successful in some areas; however, the ultimate recovery anticipated is commonly 10 to 25 percent of the original oil in place which leaves considerable potential for other recovery methods. The addition of sodium hydroxide in small amounts to the water used in waterflood operations has been proposed as a potential process for improving recovery in secondary process for improving recovery in secondary recovery operations. The effect of reducing oil - water interfacial tension has been indicated to improve recovery from waterflood operations. Laboratory work by Emery, Mungan and Nicholson illustrated that additional oil could be recovered from natural cores after reaching a water-oil ratio of 100 to 1 with the addition of sodium hydroxide. The greatest effect on recovery was noted to occur when the caustic solution was used from the beginning of the flood.