Hydrophilic–Lipophilic Balance (HLB) Correlation Method for the Selection of Ionic Liquid Surfactant Modifiers of the Viscosity and Emulsion Stability of Heavy Oils

The compatibility of heavy crude oils with ionic liquids (ILs) acting as surfactants was investigated through the hydrophilic-lipophilic balance (HLB) analysis, using independent methods for determining HLB's range of each species, including the partition function (<i>K</i>_HL), SARA analysis, and the Hildebrand's solubility parameter (δ) that were used for hydrocarbons, while the main parameters for ILs comprised the solubility parameter (δ) determined by the Davies and Lin's method, which was validated through experimental calorimetric differential scanning calorimetry (DSC) measurements. Additionally, a correlation was sought between HLB values of petroleum-heavy oils and their physical properties such as viscosity (μ) and interfacial tension (σ), from which the emulsion trends and rheological correlations were explored in a series of high-viscosity heavy crude oils whose API gravity values ranged from 9 to 13°. Their affinity with ILs was explored by the convergence of those parameters, that is, HLB, δ (Hildebrand), and IFT into a spherical locus, which gives the leading pairs of heavy oils and ILs that match together into the spherical space that defines affinity which effects interfacial tension and viscosity reduction of the heavy oils. Essentially, this method gives a systematic approach for selecting the optimal affinity between pairs of heavy oils and the chemical leads (ILs) that improve the mobility of the heavy oils and their wettability patterns. Conversely, the dispersion of points outside the Interaction Sphere defined by the HLB/δ (Hildebrand)/IFT spherical locus leads to partial emulsions and lower effects on the rheological properties of the heavy oils.