(55j) Solvents Effects on the Structure of Asphaltene Aggregates

asphaltene aggregate behavior remains poorly understood even with an abundance of hypotheses

and speculations concerning this topic. Current research suggests classifying asphaltenes into 2

types: soluble and insoluble based on their fractal dimension when precipitated in the presence of

heptane. Under these conditions two general fractal dimensions have been observed: ~2.1 for

insoluble asphaltenes (those that grow to the micrometer scale and precipitate), and ~1.7 for

soluble asphaltenes (those that remain on the nanometer scale and stay suspended in solution)1

.

Rheological measurements made in the lab also show that the intrinsic viscosity of asphaltene

aggregates changes as a function of heptane concentration. This observation is in agreement with

prior research that examined the molecular weights and intrinsic viscosities of asphaltene

aggregates in the presence of heptane2

. Indeed aggregate structure is a function of the solvent

environment, and this structure determines the phase behavior which is a precursor to deposition.

This talk will present research showing the changes in intrinsic viscosity and fractal dimension as

a function of flocculent concentration, and address the competing causes including aggregation

and solvation effects. A better understanding of aggregate behavior on the nanoscale is critical to

developing a more inclusive predicative model. Improving the understanding of asphaltene

behavior will ultimately benefit the petroleum industry by helping to avoid costly shutdowns due

to clogging and equipment failure.