A Multi-Component and Multi-Functional Synergistic System for Efficient Viscosity Reduction of Extra-Heavy Oil

The extra-heavy oil in the Tahe Oilfield of China has extremely high viscosity, as it is rich in the heavy components asphaltene and resin, creating significant difficulties in its exploitation and transportation. Therefore, it is important to effectively reduce the viscosity and improve the fluidity of this extra-heavy oil. The traditional viscosity reduction method suffers from a high blending ratio and a shortage of light crude oil resources for extra-heavy oil blending. In this study, coal tar and washing oil-widely available low-cost by-products of the coal chemical industry-are used for extra-heavy oil blending and viscosity reduction. Washing oil-containing light components distilled from coal tar-was highly effective in reducing the viscosity of extra-heavy oil. When the dilution ratio of washing oil is 0.25, the viscosity of extra-heavy oil is reduced to 1214 mPa·s, and the viscosity reduction rate is 99.8%, indicating that washing oil is an efficient viscosity-reducing agent in extra-heavy oil blending. GC-MS showed that the washing oil contained abundant aromatic hydrocarbons and aromatic heterocyclic rings. A multi-component viscosity reduction system using washing oil coupled with toluene, xylene, and surfactant achieved an even better viscosity reduction effect. In conclusion, we designed a low-cost, high-efficiency, multi-component, and multi-functional synergistic system for extra-heavy oil viscosity reduction in the Tahe Oilfield. In the proposed working mechanism, aromatic hydrocarbons and aromatic heterocyclic rings in washing oil can intercalate into the layered structure of dense asphaltene aggregates, thereby dispersing and dissociating them.