Caustic waterflooding process for heavy oils

This paper represents an analysis of a wide variety of laboratory experiments substantiating the fact that caustic waterflooding can significantly improve the waterflood recovery of certain low gravity viscous crude oils. Success of the process depends on the presence of naturally occurring organic acids in the oil which become surface active on contact with alkaline injection water. Caustic concentration, field water composition, extent of caustic reaction with reservoir rock, low caustic-oil interfacial tension, and water-oil mobility ratio are shown to be key factors in determining the success or failure of this process. Experiments show that caustic waterflooding can significantly increase the oil recovery obtained before water breakthrough. The mechanism involves in situ production of crude oil-in-water emulsions which tend to plug growing water fingers and channels, diverting flow to give better areal and vertical coverage. The laboratory experiments demonstrate the effects of the important process variables and support the emulsion plugging and diverting mechanism. (10 refs.)