A triblock copolymer for polymer flood in porous media

• Aqueous P123 solutions are unstable at high temperatures and high salinity.
• P123 forms cylindrical micelles in brine resulting in increased viscosity.
• The viscosity of the aqueous P123 solution decreases when it is equilibrated with oil.
• In the secondary mode, P123 flood is more efficient than water in displacing viscous oils.
• Oil recovery for P123 is similar to HPAM, but with a lower pressure gradient.

High molecular weight polymers are used in petroleum reservoir polymer floods to enhance oil recovery. The objective of this work is to evaluate small polymeric surfactants for their viscosifying capacity in reservoir brines and oil displacement ability. The phase behavior and viscosity of a triblock copolymer (P123) are studied as a function of brine salinity and temperature. Its flow through a porous rock and oil displacement is evaluated and compared with that of a Newtonian fluid (glycerol) and a non-Newtonian fluid with a high molecular weight polymer (HPAM) of similar viscosity. P123 forms cylindrical micelles in brine to give high viscosity. The viscosity increases with salinity at a low salinity, but decreases at a higher salinity. In the secondary mode, both the polymers (P123 and HPAM) and glycerol solutions increase the oil recovery significantly over the water flood. The oil recovery is similar for the three viscous fluids. In the tertiary mode, none of the viscous fluids increased oil recovery over the waterflood at typical field rates. Pressure drop during P123 flood is significantly lower than the pressure drop during HPAM and glycerol floods of similar initial viscosity. Viscosity of the aqueous P123 solution decreases when it is equilibrated with oil. Some of the cylindrical micelles are converted to spherical micelles in the presence of solubilized oil. P123 is not as cost effective as HPAM because it is slightly more expensive and needs a higher concentration for a similar viscosity.