Rheological properties of nanofiltered athabasca bitumen and maya crude oil

Complex viscosities of Athabasca bitumen (Alberta, Canada) and Maya crude oil (Mexico) samples, along with their permeates and retentates obtained by nanofiltration at 473 K through 5-, 10-, 20-, 50-, and 200-nm ceramic membranes, were investigated over the temperature interval of 298-373 K. The pentaneasphaltene content of the samples varied from 1.5 wt% to 57.2 wt %, whereas the asphaltene-free composition of the samples did not vary from the feed composition (within experimental error). At temperatures of <323 K, part of the maltenes of both of these hydrocarbon resources is solid. The solid maltene fraction is a function of temperature. If this additional solid is taken into account, the experimental relative viscosities for both Athabasca bitumen- and Maya crude-related samples fall on a single master curve, over the entire temperature interval, irrespective of the asphaltene content. The rheological behavior of all feed, permeate, and retentate samples is consistent with that of a slurry that is comprised of a Newtonian liquid plus a dispersed solid that is comprised of noninteracting hard spheres, where the solids fraction is the sum of the solid maltene plus asphaltene mass fractions. Failure to account for solid maltenes in the interpretation of rheological data for these hydrocarbon resources leads to misattributions related to the nature and importance of the role that asphaltenes play in the determination of the complex viscosity of these hydrocarbon resources. copyright