13. Dynamics of Saltwater–Freshwater Interface

The displacement of a fluid by another one of different density and viscosity represents a problem of fundamental interest. It finds applications in situations ranging from enhanced oil recovery and the spreading of pollutants in groundwater reservoirs, to processes accompanying CO₂ sequestration in the deep geological formations. In the first part of this chapter (Sect. 13.1) the linear (unidirectional in the horizontal plane) and radial movement of the interface between displacing and displaced fluids in a confined homogeneous aquifer is analyzed. In the second part of the chapter (Sect. 13.2) we will examine how some ideas of the two-phase flow theory can be used to model the migration of brine in fresh water aquifer systems.