Peter Kilpatrick

Professor and Head of Chemical Engineering

North Carolina State University

Raleigh, North Carolina 27695-7905

(919) 515-7121; peter-k@eos.ncsu.edu

Asphaltenes are the toluene-soluble and heptane-insoluble fraction of petroleum. With hydrogen-to-carbon atomic ratios of 1.0-1.3, combined nitrogen and oxygen percentages of a few percent (w/w), and molar masses of around 1,000 daltons, asphaltenes tend to be large flat molecules with considerable fused ring aromaticity and polar functional groups. These molecules interact with each other to form aggregates of several nanometers dimension. Under appropriate solvent conditions, these aggregates can grow and deposit on reservoir rock surfaces or at oil-water interfaces. The resulting deposition and emulsion challenges which these sorptive events pose to the industry are substantial. In this talk, we relate the chemistry of asphaltenes from differing sources and by fractionation to their aggregate-forming and emulsion-stabilizing properties. We conclude that there is a balance of aromaticity and polarity which gives rise to aggregates of intermediate dimension which form the most stable water-in-oil emulsions. Results are presented from small angle neutron scattering, interfacial rheometry and classical bottle tests on emulsion stability.