Rheological Study of Athabasca Bitumen and Maya

Rheological Study of Athabasca Bitumen and Maya
Crude Oil
MD. Anwarul Hasan1, Michal Fulem2,3 and John M. Shaw2
Department of Mechanical Engineering, University of Alberta, Edmonton,
Alberta, T6G 2G8, Canada
Department of Chemical and Materials Engineering, University of Alberta,
Edmonton, Alberta, T6G 2G6, Canada.
Institute of Physics, Academy of Sciences of the Czech Republic, v. v. i.,
Cukrovarnická 10, CZ-162 53 Prague 6, Czech Republic.
Heavy oil and bitumen are characterized by extremely high viscosity that
negatively affects their upstream recovery, downstream transportation and
refining processes. One of the key factors in facilitating the production and
transportation is thus a better understanding of the origination of their high
viscosity and the ability to reduce the viscosity to meet pipeline
specifications (usually 0.4 Pa.s at operating temperature). The viscosity of
heavy oil and bitumen and the structure of asphaltenes are linked to each
other. It is known for decades that asphaltene content plays an important
role in heavy oil and bitumen rheology with the general trend being that the
viscosity increases with increasing asphaltene content. However, the
influence of asphaltenes on viscosity has so far been studied on simplified
samples where chemically separated (solvent extracted) asphaltenes are
dissolved in some standard solvents or in the deasphalted oil (maltenes) to
obtain reconstituted samples with different asphaltene concentrations. The
question, how closely the nanostructures of such reconstituted samples
resemble those arising in the original material remains unanswered in the
literature. In this contribution, we report on the rheological properties of
Athabasca bitumen and Maya crude oil along with their nanofiltered
samples obtained by solvent-free nanofiltration (physical separation) and
reconstituted samples prepared by mixing precipitated asphaltenes
(chemical separation) and maltenes in different proportions. The rheological
properties were studied over wide temperature and frequency ranges. The
differences in rheological behaviour between nanofiltered and reconstituted
samples, and the origins of these differences are discussed.