Alternatives to the salinity gradient for controlling the effects of dispersion in surfactant floods

Numerical simulation is used to review the effects of middle phase mobility on the efficiency of a threephase surfactant flood and the use of a salinity gradient to counter the adverse effects of dispersion (by producing 'self-sharpening' of the surfactent slug). Alternative means of producing self-sharpening behaviour are then investigated. Inclusion of an alcohol in the chemical slug is shown to be a viable alternative to a salinity gradient, provided that the phase behaviour properties of the alcohol are chosen correctly. However, under the assumptions that optimal salinity is independent of surfactant concentration and that surfactant partitions almost wholly into the middle phase when that phase exists, it is not possible to achieve self-sharpening behaviour merely by varying the formulation of the surfactant within the chemical slug.