Lipid nanostructures as surfactant carriers for enhanced oil recovery

The main challenge faced by enhanced oil recovery processes (EOR) is to further increase production of the residual oil trapped within the reservoir porous media beyond conventional recovery methods. Chemical EOR processes, such as surfactant flooding, could be employed to dislocate the residual oil to a production well through the reduction of the water/oil (w/o) interfacial tension. Surfactant Flooding is an efficient method, but a large part of the injected surfactant is lost by adsorption on the rock surface before reaching the oil site, turning it often economically unfeasible. This work aimed to evaluate the potential of lipid nanostructures as surfactant nanocarriers for the EOR process. In this new concept, nanocarriers formed by hydrophobic nanoparticles (NPs), should be able to store and carry the surfactant molecules through the reservoir porous media, releasing the surfactant only at the w/o interface, triggered by the nanocarriers solubilization. The released surfactant did lead to a w/o interfacial tension reduction, improving the recovery factor. Nanoparticles were produced through nano-emulsification techniques with beeswax (BW) as the lipid structure and nonylphenol ethoxylate (NPE10) as surfactant. The nanocarriers were characterized by dynamic light scattering (DLS), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and surfactant entrapment in the nanocarriers. Interfacial tension (IFT) measurements and Fourier transform infrared spectroscopy (FTIR) analysis were used to evaluate the surfactant release and unconsolidated sandpack column tests were conducted to evaluate the transport behavior of the NPs system. The results did demonstrate that the nanocarriers should be able to permeate through the porous media and release the surfactant at the w/o interface, reducing the IFT to values compatible with the ones obtained when employing solely the surfactant solution. The effect of the nanoparticles production process, temperature and salt concentration on the efficiency of the nanoparticles in the delivery of the surfactant at the oil/water interface was evaluated and the results showed the great potential of this type of system as surfactant nanocarrier for the EOR process.