Physicochemical eor techniques
Polymer flooding is the injection of water with polymer additives into an oil reservoir in order to improve the sweep of the reservoir by the displacement process. High viscosity improves the mobility ratio of the injected fluid and hydrocarbons in the formation.
The technology has a positive effect on sweep efficiency, allows to increase the productivity of wells, reduce water cut and increase the oil recovery factor.
The most common polymer flooding agents are acrylamide-based high molecular weight polymers (partially hydrolyzed polyacrylamides), used primarily in powder and emulsion form.
SP (surfactant-polymer) flooding involves injection of polymer and surfactant into the reservoir. While the main objective of polymer injection is mobility control by reducing the mobility ratio between water and oil, surfactants are injected to mobilize residual oil by lowering the interfacial tension between oil and water and/or by the reservoir wettability alteration from oil-wet to water-wet.
In ASP (alkali-surfactant-polymer) flooding the main function of the alkali is to prevent the expensive surfactant from retention in the formation rock and thereby reduce its losses. Alkali reacts with the natural organic acids presented in the crude oil, forming a new in-situ surfactant at the oil-water interface which also reduces the interfacial tension.