Improving the efficiency of diluents for heavy oil pipeline transportation

Abstract

With the projected increase in the Canadian production of heavy oil and bitumen, the transportation issues are likely to come to the forefront. The occurrence of asphaltene association in heavy oil is a contributing factor in high viscosity of heavy oils. The asphaltene aggregates formed by asphaltene self-association can also precipitate by the variation of temperature, pressure or oil compositions. Precipitated asphaltenes can form deposits on the wall of pipelines so as to reduce the effective transportation volume. Therefore, if the asphaltene association can be inhibited, it will improve the efficiency of heavy oil transportation significantly. In this research, different solvents and their combinations were tested to evaluate their dilution effects on heavy oils and their abilities for inhibiting asphaltene association. Diluents were formulated by combining aromatic and polar solvents. Analysis of experimental results showed that polar solvents can be beneficial, when combined with non-polar diluents, in inhibiting asphaltenes association and reducing oil viscosity. The ability of a solvent for inhibiting asphaltene association improves mildly with increasing its aromaticity. Several surfactants were evaluated as additives to inhibit the asphaltenes' association. These surfactants were tested with heavy oil diluted with a common solvent by measuring their impact on the diluted oil viscosity. The surfactants were also tested on solution of asphaltenes in m-xylene to isolate their abilities for inhibiting asphaltene association. Our results suggested that generalization on optimal molecular structure of surfactants for inhibiting asphaltene association in heavy oil pipeline transportation has to account for the presence of resins and other oil constituents.