Trapped solvent droplets within a water-filled column packing can be liberated by Injection of a partitionable solute which induces coalescence to form larger, easily-deformable droplets. This result, an outcome of the Marangoni effect, is normally much more marked when the solute transfers from solvent into aqueous phase; however, some solutes can be effective in both directions of transfer. A proposal is made for a novel method of utilising the Marangoni effect to achieve EOR by solute flooding, followed by a repeated water (or gas) drive; unlike a previously reported, unsuccessful study, this previously reported, unsuccessful study, this takes advantage of the non-equilibrium nature of the effect.
The Marangoni effect, in the form of the spreading of an oil or other immiscible solvent on water, was first reported in 1855 by Thompson, and later by Marangoni, after whom it was named. The spreading is due to a reduction in surface or interfacial tension at the point of contact, corresponding to an increase in surface pressure. It is responsible for the creeping of alcoholic liquors up the side of a wineglass (due to evaporation of alcohol with resulting increase in surface tension and hence decrease of surface pressure around the edge of the glass), and also for the motion of camphor "boats" on water. An important application is its use for breaking foams on liquid surfaces, by the dropwise addition of a higher alcohol, e.g., n-octanol.
In 1953, the writer and a colleague attempted to measure the interfacial tension of isolated drops while undergoing mass transfer, e.g., of acetone from a butyl acetate drop into water, using the pendant drop method. To their surprise, the drop was seen to undergo violent oscillations, which made the measurement impossible. This was thought at first to be thermally motivated; however, it was later found to result from the setting up of interfacial tension gradients (Marangoni effect) due to variations in mass transfer rate, and hence in interfacial concentration around the drop. Later work by the writer and colleagues showed that the performance of liquid-liquid extraction columns was influenced to a major degree by the Marangoni effect.