Alkali Surfactant Polymer ASP flooding
is an alternative to surfactant flooding developed in the 1980’s. In ASP floods, lowcost alkaline chemicals (Na2CO3 or NaOH) are mixed in solution with a low dosage of more expensive surfactants and polymers for mobility control to reduce interfacial tension
. Currently ASP flooding is one of the most commercially applied onshore chemical EOR processes
. A key aspect is the ability of alkaline agents to change rock chemistry to significantly decrease chemical adsorption.
Application is primarily in reservoirs with low to medium gravity (18 to 25 degrees API) and moderate viscosity (2 to 100 cP).
The use of ASP Alkali Surfactant Polymer should be designed to reduce capillary-bound oil saturation in sufficient quantity to recover large volumes of oil
and thus to be economic. The process will require a good characterization of remaining, residual oil saturation in the aquifer flooded regions. Since water injection for secondary recovery has not been done, inactive production wells would need to be converted to injection.
The incremental oil recovery from ASP is estimated at 27% of OOIP. It is common to have production and operations issues with polymer and ASP flooding. The issues are related to the production of polymer and residual alkali-surfactants in creating emulsions, inducing microbial related corrosion, and increasing potential for bio-fouling of surface equipment.