(181c) Understanding the Role of Iron Tosylate on Heavy Oil Viscosity Reduction

Heavy oil is an abundant energy resource, but its recovery remains challenging primarily due to its high viscosity. Thermally enhanced oil recovery in the presence of metal-ligand compounds (MLCs) has been studied as a promising method for in situ viscosity reduction and oil quality upgrading. In spite of its importance, the interactions between MLCs and crude oil components at the molecular-level are poorly understood, as well as, the mechanistic details for viscosity reduction are unknown. Here, we studied viscosity changes of real crude oil in the range of 80 - 295 °C with or without iron para-toluenesulfonate (tosylate) MLC, and analyzed reaction products via viscometry, TGA-MS, NIR spectroscopy, GC-MS, SARA analysis, XRF, and XPS. Thermal treatment lowered viscosity at all temperatures, whereas thermal treatment in the presence of this MLC decreased viscosity at temperatures above 230 °C. The MLC effect was strongest at 280 °C, at which thermal treatment without and with the iron tosylate decreased viscosity by 39% and 58%, respectively. 4-methylbenzenethiol was detected in the oil, corresponding to the loss of one of the three para-toluenesulfonate ligands. The MLC also lowered asphaltene fractions more than thermal-only. We propose the MLC lowers oil viscosity by releasing a ligand to form a compound that interferes with asphaltene interactions, and by catalytically reacting with the asphaltene which decreased the asphaltene fraction. This understanding of MLC-induced deviscosification provides better rationale for the selection of metal and ligand to improve thermally enhanced oil recovery.