Oil-Displacing Formulation Based on a Deep Eutectic Solvent: Effect on the Composition and Properties of Heavy Crude Oil from the Usinskoye Field

Abstract This study investigates the effect of treating heavy, high-viscosity crude oil from the Usinskoye field with a formulation comprising a ternary deep eutectic solvent—pentaerythritol, urea, and choline chloride—and a surfactant. The study was performed by physical simulation of oil displacement from a heterogeneous reservoir model, followed by chromatographic analysis and physicochemical characterization of crude oil samples. The key mechanism of action of the formulation involves degradation of resins via their acid groups. This leads to the transition of saturated hydrocarbons (alkanes) into the light petroleum fraction and the overall redistribution of the crude oil components. The altered component composition of the crude oil improved its physicochemical properties, significantly reducing viscosity and density and, thus, improving the filtration characteristics and increasing the oil displacement efficiency up to 20.2%.