Surfactant Added Water Flood

Water Flood is commonly used as an economic and effective method in secondary recovery after primary methods have been exhausted. In general, the water flood can remove ~20-30% of the residue oil, however, it still leaves ~50-70% residual oil in the formation. After the water flood, the capillary number is ~ 10^-6 and the residual oil cannot be further removed without other chemical or mechanical means.

The capillary number, Nc, is a function of velocity, viscosity and interfacial tension: (Relationship between capillary number and residual oil recovery, Chatzis and Morrow, SPEJ,1994, P.561)

The velocity and the viscosity of the injection fluid cannot be increase by any appreciable amount because of mechanical constraints and the possibility of damaging the formation. However, the interfacial tension can be easily reduced 3 to 4 orders of magnitude to increase the capillary number to the 10^-3 range in order to remove the residual oil.

After water flood, water channels are formed and adding surfactant alone is generally not enough to remove any additional oil economically. However, by adding a low concentration of the surfactant from the beginning of the water flood the oil recovery may be increased over pure water flood alone. Oil Chem Technologies offers many surfactants that can be used to enhance the results of the water flood. Typical surfactant concentrations are in the 0.1% by weight range.