Chitosan derivatives as surfactant carriers for enhanced oil recovery - Experimental and molecular dynamic evaluations of polymer-surfactant interactions

Surfactant injections in enhanced oil recovery (EOR) are very efficient, lowering the oil-water interfacial tension (IFT) and altering rocks wettability. Although efficient, surfactant injection during EOR process is economically unfeasible due to the high-cost caused by surfactant losses due to adsorption or precipitation on the rock surface. One strategy to reduce these losses during the flooding process is using surfactant carriers such as nanoparticles, emulsions, and polymers. Polymers are good candidates because they can act in transportation, alter rock wettability, and improve sweeping efficiency. Recently, the potential of chitosan derivatives as wettability modifiers of carbonate rocks was demonstrated. This way, using chitosan derivatives as surfactant carriers is an interesting strategy due to its high storage capacity and environment-friendly product. In this study, cationized (TMC) and hydrophobized (TMC-C14) chitosan derivatives were synthesized, characterized, and evaluated as OADA (oleic acid diethanolamide) surfactant carriers for EOR. Interfacial tension tests evaluated the potential of OADA in low and high salinity medium. Particle size measurements, done by dynamic light scattering, and molecular dynamics simulations (MD), allowed the understanding of the interaction between TMC or TMC-C14 and the surfactant. The controlled surfactant release at the water/oil interface by chitosan derivatives was evaluated by IFT measurements and MD simulations. The results showed that OADA is an excellent surfactant whose IFT reaches 10-2 mN/m, and chitosan derivatives were able to carry the surfactant to the site containing the oil. Thus, chitosan derivatives are an efficient supramolecular surfactant carrier system that can minimize surfactant losses by adsorption on the rock surface, being an interesting alternative for EOR application.