(181b) Chemical Control of Asphaltene Aggregation from Cohesive Force Measurements

Asphaltene solids may precipitate in subsea crude oil wellbores and flowlines, due to the rapid decrease in fluid pressure during flow. While the consequence of asphaltene deposition and build-up at the wall is well-understood, little is known about how precipitated asphaltene particles behave in flow. In this work, a micromechanical force apparatus was used to estimate the asphaltene particle surface free energy in a variety of continuous phases; the apparatus was further able to capture the adsorption behaviour of surfactants at the asphaltene particle surface. Pentane-, hexane-, and heptane-extracted asphaltenes were tested in duplicate; one set of each was further washed with hot heptane to purify the extracted asphaltenes. The data suggests that asphaltene cohesive force does not exhibit a significant dependence on the extraction method of the asphaltenes, and indicates that asphaltene cohesion does not depend strongly on the carbon number of the continuous phase. In addition, we present the first data demonstrating adsorption-type behaviour of surfactants on the asphaltene particle surface, which demonstrates the effectiveness of chemical control of the asphaltene aggregation potential.