Oil recovery by waterflooding with thickened surfactant solutions

摘要

Waterflooding process for the recovery of oil for a subterranean formation in which at least a portion of the injected water is thickened by the addition of a sulfonated polyethoxylated aliphatic alcohol surfactant. The thickened water has a salinity within the range of 5-18 percent. The sulfonated polyethoxylated aliphatic alcohol has at least two ethylene oxide units to provide an HLB within the range of 10.0- 14.0 and the lipophilic base contains from 16 to 20 carbon atoms. The thickened surfactant slug may be preceded by the injection of a relatively low viscosity surfactant slug and viscosity gradation of the thickened surfactant slug may be accomplished by varying the salinity and/or the concentration of the sulfonated polyethoxylated aliphatic alcohol.