Petroleum heavy ends stability: Evolution of residues macrostructure by aging

Rheological and small-angle scattering techniques were used to investigate the evolution of the colloidal structure of the Safaniya vacuum residue during the age hardening process. Rheological measurements revealed an increase in the molecular weight of the vacuum residue and maltene fraction after the RTFO aging test. Even the molecular-weight distribution became slightly wider, the amount of this variation being greater for aged maltenes than for the whole aged vacuum residue. Small-angle scattering results confirmed the importance of maltene aging on the whole sample viscoelastic properties; the macrostructure of asphaltenes both in solution and in a vacuum residue did not appear to be representative of the age hardening process, in contrast to previous findings.