Acidic Oil- Displacing System Based on Deep Eutectic Solvents and Surfactants: Development, Physical and Chemical Studies, Evaluation of Its Effect on the Composition and Properties of Oil

The paper presents the findings of a study of a ternary system of deep eutectic solvents (DES) 'boric aciD- glycerol - carbamide', whose combination with surfactants for enhanced oil recovery forms the basis of an acidic oil-displacing composition. The results of laboratory investigation of the effect of a DES and surfactants-based composition on the filtration characteristics of a heterogeneous formation of a terrigenous reservoir of the Russkoye field are also reported. An oil-displacing composition characterized by physicochemical parameters controlled in a wide range has been developed on the basis of experimental phase equilibrium data for the components of, DES systems. The method of physical modeling is used to evaluate the effectiveness of the system as applicable to oilfields at the early and late stages of development. It has been established that the treatment of a heterogeneous reservoir model with a composition results in a significant increment in the oil displacement efficiency both at low and high temperatures due to the smoothing of filtration flows. The increase in the reservoir coverage and restoration of the initial permeability are also observed. The study of the composition and properties of heavy high-viscosity oil before and after its treatment with the system show that the use of an acid oil-displacing system based on DES and surfactants causes no significant changes in the qualitative composition of the oil but generally leads to a redistribution of the content of low and higher molecular structures. Hence, light occluded hydrocarbons are preferably displaced, while heavy oil components are adsorbed on the reservoir.