Synthesis of branched geminal zwitterionic liquids as wettability modifiers in enhanced oil recovery processes

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A new class of branched geminal zwitterionic liquids (BGZLs) betaine base with a long alkyl chains with either 8 (BGZL-ZW8) or 12 (BGZL-ZW12) carbons was synthesized and characterized by nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopic techniques. The BGZLs molecules presents functionality as viscosity reducer and wettability modifier with application in enhanced oil recovery (EOR) processes with good oil recovery factors (ORF). The above is demonstrated by performing spontaneous imbibition tests on embedded limestone cores with light and heavy crude oils in Amott cells at high temperature (90 °C) and different concentrations of BGZLs in presence of connate water with high salinity and hardness (36,275 ppm as NaCl and 6700 ppm hardness as CaCO3). The rheological behavior of BGZLs was also determined as viscosity reducers in heavy crude oil at concentrations of 2000, 1000 and 500 ppm at temperatures of 25 and 40 °C, in the range of 36.11% to 25 °C and 43.31% to 40 °C. To explain the mechanism through BGZLs act as viscosity reducers, we realized theoretical studies using the density functional theory (DFT), also as wettability modifiers taking BGZL-ZW8 and BGZL-ZW12 behavior, observed in the experimental part. The interaction energies show that BGZLs can disaggregate asphaltene (Asph) dimmer (Asph:Asph) by the formation of supramolecular sandwich complex (Asph:BGZL:Asph) among BGZLs and Asph:Asph, modifying the properties of crude oil such as viscosity, is possible to support the fact of the BGZLs can desorbs Asph molecules of the rock surface, modifying the calcite surface (Cs) wettability of oil-wet to water-wet. The results of this research show that it is feasible the use of zwitterionic liquids as viscosity and wettability modifier in EOR process.