INTERFACIAL TENSION BEHAVIOR IN OIL-WATER SYSTEMS RELATED TO CRUDE OIL RECOVERY
Advancing the chemical engineering fundamentals
Interfacial & Colloidal Phenomena - I (T2-6a)
Keywords: Interfacial tension. Oil-water systems. Oil recovery.
Interfacial tension is an important property of systems consisting of two phases. In immiscible liquid-liquid systems, such as that composed of pure octane and pure water, the interfacial tension between the two components is essentially constant. However, most real life oil-water systems found in nature or in industrial processes do not fall into that category. Often, surface-active substances are present. These may be a part of the original system, or they may have been added to the system for a specific purpose. Surface-active substances may also enter the system through interaction with its surroundings. For example, in the process of enhanced oil recovery by injection of aqueous fluids, surface-active substances may be extracted from the surrounding rock or soil, or they may be produced through oxidation of reactive oil components by oxygen dissolved in water. Of particular interest in oil recovery is the case in which a surfactant is produced in-situ via a chemical reaction occurring at the interface. This situation is encountered when an injected alkaline solution reacts chemically with naturally occurring oil-borne acids. Such systems rarely attain a true equilibrium, and the oil-water tension at the interface is thus dependent on time (i.e., transient). When the reacting interfaces are continuously moving and changing, as it is the case when an acidic crude oil is being displaced by an alkaline solution inside a porous rock, the interfacial tension becomes also location dependent and it acquires a truly dynamic character. Resulting interfacial tension gradients give rise to Marangoni flows. The exact behavior of a chemically reacting, flowing two-phase system (for example, in terms of displacement instabilities and oil recovery) then becomes very difficult to predict and simulate. In addition to that, both added and in-situ generated surface-active substances may undergo adsorption on solid surfaces, thus altering surface wettability. This also has a strong effect on the flow patterns observed and, ultimately, on the recovery of oil. The above mentioned phenomena will be discussed with reference to experimental results obtained in the authors’ laboratory.
Presented Wednesday 19, 15:40 to 16:00, in session Interfacial & Colloidal Phenomena - I (T2-6a).
