The best way to visualize ASP flooding is to imagine washing a greasy dish with water versus with soap and water. Washing with water only is the equivalent of a basic waterflood whereas washing with soap is the equivalent of ASP flooding where the alkaline and surfactant components act as the soap to free the oil from the surface. 

The polymer mixes with the two surfactants to increase viscosity in order to maintain a strong front and is also injected afterward with water as a gel to push the ASP-oil mixture towards the well.


http://zargon.ca/operations/oil-exploitation/tertiary-recovery/

The main purpose of ASP is to reduce the interfacial tension (IFT) between the oil and the ASP mixture so that the oil can be mobilized, just as the soap would do for the grease on a dish.