Alkali-Surfactant-Polymer (ASP) flooding simply adds surfactant (0.05% to 0.5%) to an AP solution to broaden the range of reservoir environment for which the ASP process applies. Many light oils do not contain sufficient amounts of the components that react with alkali to reduce the oil-water interfacial tension sufficiently to overcome capillary forces trapping the oil. Blending surfactant with the alkali overcomes this barrier. As with Alkali-Polymer flooding, the water must have very low divalent ion content (hardness), often requiring softening.
One property of alkaline agents is that they change the reservoir rock chemistry in such a way as to significantly decrease adsorption. Therefore, ASP projects use lower concentrations of added surfactant than Surfactant-Polymer or Micellar-Polymer projects. ASP flooding is being applied in field projects around the world with incremental recoveries in some cases greater than 20% OOIP.
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