RHEOLOGY OF HEAVY CRUDE OILS WITH ASPHALTENES

Nowadays the energy demand has increased dramatically and petrochemical companies are focusing on the so-called unconventional oils, that represent the 70% of the world available reserves. Unconventional oils are characterized by high viscosities, principally due to the macromolecules known as asphaltenes. Extracting and pumping unconventional oils with very high viscosity represent an economic and technical challenge because of, e.g., tube clogging induced by asphaltenes precipitation. The reduction of extra-heavy crude oil viscosity is a key goal of petrochemical companies. This reduction can be obtained with addition of solvents and/or additives to oil. We study three oils coming from the same well and taken from the very same tank in different moments. Therefore they are supposed to be the same. Despite this, their rheological response shows both quantitative and qualitative differences. We then looked for the possible origin of this different behavior by performing a detailed chemical-physical investigation of the three oils and of their asphaltenes fraction. The latters amount to the 19 % in weight in all the three cases. The oils show the same TGA, UV and Fluorescence spectra. Very similar HPLC chromatograms and ATR - FTIR spectra. The ICP - MS results are slightly different. The same holds for the asphaltenes fraction. The rheology is very sensitive to the microstructure and highlights differences not immediately revealed with the other techniques.