Effect of Aromatic Ring, Cation, and Anion Types of Ionic Liquids on Heavy Oil Recovery

Abstract

Surfactant/alkali flooding is one of the best chemical flooding methods to enhance the oil Recovery Factor (RF). In this research, Ionic Liquid/Alkali (ILA) mixtures were chosen to represent a form of chemical flooding experiments. The selected Ionic Liquids (ILs), {[EMIM][Cl], [THTDPH][Cl], [EMIM][Ac], [BzMIM][Cl], [DMIM][Cl], [BzMIM][TOS], [dMIM][TOS] and [MPyr][TOS]}, were introduced to investigate their efficiency in improving heavy oil (14o API) RF from the sand packs. Besides, the use of mixtures of the same ionic liquids and brine (3.37 wt. % salts) with an alkali (Sodium Bicarbonate [NaHCO3]) were also investigated. In this experimental study, the flooding process started with injecting about 3.2 Pore Volumes (PVs) of only brine, followed by one PV of the chemical composites, and flushed with two PVs of formation brine. The study discussed the influence of cation type, anion type, the structure of the ILs, and the effect of combining ILs/alkali on the RF. The results revealed that the proposed chemical mixtures are effective in enhancing the recovery factor. ILs with shorter alkyl chain and more aromatic rings are noticeably more efficient in enhancing the RF. Finding the optimum composition of ([DMIM][Cl] + NaHCO3) the chemical slug increased the additional RF up to 31.55 (% OOIP). Also, increasing the slug size to two PVs improved the RF to 42.13 (% OOIP). The recovery factor mechanism was explained and supported by measuring the effect of IL types on the viscosity, Surface Tension (SFT), and Zeta Potential (ZP) of the mixture.