Foam for Environmental Remediation: Generation and Blocking Effect

Foam injection is widely used in petroleum industry for enhanced oil recovery, but has received limited attention for the application of environmental remediation at the field scale. This study analyses the use of foam as a blocking agent, i.e. to confine a source zone of contaminant in groundwater. Laboratory experiments in 1D porous media with a commercially available biodegradable surfactant performed on columns using pre-generated foam show that the foam reduces the relative water permeability k_rw by a factor of 100–1000. k_rw was measured right after foam placement by injecting only water (drainage test) and corresponding to the relative permeability of water in presence of foam. A comparison to a theoretical two-phase flow in porous medium shows that the Van Genuchten equation can be used to estimate the k_rw value. In the field, experiments done on two different porous media and using three different injection techniques (co-injection, surfactant alternating gas, pre-generation) show a clear confining ability of the produced foam. A k_rw reduction by a factor of 1000 is observed very close to the well and close to 100 at 1 m of this well. These values were obtained with a much weaker foam than the laboratory one in order to allow the injection at shallow depth environmental compatible ssure ( ≤ 4 bar). The reduction in water relative permeability can occur in the presence of a foam that does not cause an extreme reduction of the mobility, indicating that this reduction does not depend on resistance factor (RF) values. There is potential for improvement of the foam as it loses its efficiency with increasing distance from the injection well.