Chemical flooding processes can be devided into three main categories: 1. Surfactant flooding; 2. Polymer flooding; 3. Caustic flooding. In surfactant/ polymer flooding process, the primary displacing fluids slug is a surfactant, next a polymer slug, and followed bu a buffer. This process can improve both sweep efficiency and displacement efficiency for water drive reservoirs.
The mechanism of oil displacement by surfactant and caustic flooding is based on the formation of ultra-low interfacial tension, whereas polymer flooding alone, or injection of surfactant followed by polymer flooding, results in controlling the mobility which in turn enhances oil recovery. Caustic injected into the petroleum reservoir reacts chemically with the fatty acids present in the petroleum derivatives and forms in situ sodium salts of fatty acids. The formation of these surfactants results in ultra-low interfacial tension.