Interfacial Properties, Wettability Alteration and Emulsification Properties of an Organic Alkali-Surface Active Ionic Liquid System: Implications for Enhanced Oil Recovery.

Combinatory flooding techniques evolved over the years to mitigate various limitations associated with unitary flooding techniques and to enhance their performance as well. This study investigates the potential of a combination of 1-hexadecyl-3-methyl imidazolium bromide (CmimBr) and monoethanolamine (ETA) as an alkali-surfactant (AS) formulation for enhanced oil recovery. The study is conducted comparative to a conventional combination of cetyltrimethylammonium bromide (CTAB) and sodium metaborate (NaBO). The study confirmed that CmimBr and CTAB have similar aggregation behaviors and surface activities. The ETA-CmimBr system proved to be compatible with brine containing an appreciable concentration of divalent cations. Studies on interfacial properties showed that the ETA-CmimBr system exhibited an improved IFT reduction capability better than the NaBO-CTAB system, attaining an ultra-low IFT of 7.6 × 10 mN/m. The IFT reduction performance of the ETA-CmimBr system was improved in the presence of salt, attaining an ultra-low IFT of 2.3 × 10 mN/m. The system also maintained an ultra-low IFT even in high salinity conditions of 15 wt% NaCl concentration. Synergism was evident for the ETA-CmimBr system also in altering the carbonate rock surface, while the wetting power of CTAB was not improved by the addition of NaBO. Both the ETA-CmimBr and NaBO-CTAB systems proved to form stable emulsions even at elevated temperatures. This study, therefore, reveals that a combination of surface-active ionic liquid and organic alkali has excellent potential in enhancing the oil recovery in carbonate reservoirs at high salinity, high-temperature conditions in carbonate formations.