Synthesis and characterization of surface-active ionic liquids for their potential application in enhanced oil recovery

In enhanced oil recovery, most widely used combinations of chemical formulations incorporate surfactants, polymers and alkalis, however, it is important to investigate alternate options which could offer improved performance and superior operational flexibility in comparison to conventional technologies. Surface active ionic liquids (SAILs) are novel functional ionic liquids with amalgamated properties of surfactant and ionic liquid, which represent an interesting alternative especially in harsh reservoir conditions for enhanced oil recovery processes. The present study illustrates a methodological laboratory assessment of synthesised SAILs to investigate their applicability for enhanced oil recovery based on their physicochemical evaluation. FT-IR, H-1 NMR and TGA confirmed the chemical structure and thermal stability of the synthesised C(12)mimBr and C(16)mimBr. SAILs in aqueous solution were studied to determine their surface and interfacial behaviour under reservoir conditions. The synthesised SAILs showed lower critical micellar concentration similar to 200 ppm (C(16)mimBr) and good surface-active properties and high efficiency on the interface adsorption. The interfacial tension was reduced to ultra-low values (range of 10(-)(13) to 10(-14)) in wide ranges of salinity, concentration, and temperature, thus provide valuable evidence for its application as surfactants in EOR. The phase behaviour studies further suggested the formation of WINSOR-III micro-emulsion, thus making it a robust performance formulation. (C) 2021 Elsevier B.V. All rights reserved.