High-Flashpoint Solvent Treatment for Heavy Oil Viscosity Reduction: A Safer Alternative to Xylene-Based Systems

Abstract

Heavy and emulsified crude oils are frequently associated with high viscosity, elevated water cut, and strong emulsion stability, which restrict efficient production, stimulation, and transportation. Aromatic solvents such as xylene are commonly applied to reduce viscosity and dissolve organic deposits; however, their high volatility, flammability, and toxicity pose significant health, safety, and environmental (HSE) risks. This study presents the development and laboratory evaluation of a high-flashpoint, xylene-free organic solvent system designed to deliver equivalent or superior performance without the operational hazards associated with Benzene, Toluene, Ethylbenzene, and Xylene (BTEX) -containing formulations. Laboratory testing was conducted on an 18.5°API emulsified crude oil containing approximately 25% water under representative surface and near-wellbore conditions. The optimized xylene-free formulation reduced viscosity from 99 cP to as low as 19.5 cP, corresponding to an ~80% reduction, outperforming a conventional diesel–xylene–mutual solvent benchmark. Beyond viscosity reduction, the Xylene-free solvent (XFS) system demonstrated multifunctional performance, including effective emulsion breaking, achieving approximately 22.7% water separation from a stable crude oil emulsion, and enhanced asphaltene dispersion, exceeding 90% dispersion efficiency at moderate dosages. Organic-deposit dissolution testing showed >95% dissolution, exceeding xylene performance while requiring ~20% lower solvent volume, indicating improved chemical efficiency. Flash-point testing confirmed a substantial safety advantage, with XFS formulations exhibiting flash points above 50–64°C, compared with 18.3°C for xylene. Elastomer compatibility testing further demonstrated significantly reduced swelling of elastomers, supporting suitability for Electric Submersible Pump (ESP) and elastomer-sensitive applications. The proposed formulation represents a technically viable, safer, and more sustainable alternative for heavy-oil viscosity reduction, flow-assurance enhancement, and organic-deposit remediation.