Investigations Into Asphaltene Stability Using Capillary Deposition

Wednesday, November 10, 2010: 2:10 PM
Deer Valley I (Marriott Downtown)
Michael P. Hoepfner, Tabish Maqbool and H. Scott Fogler, Chemical Engineering, The University of Michigan, Ann Arbor, MI

Asphaltene deposition is a costly concern in flow assurance. Precipitation and deposition can occur in the porous rock formations, well-bore, production lines and in the refinery. Recent work in asphaltene aggregation at low precipitant concentrations has revealed that asphaltenes are less stable than previously thought [1]. These measurements employed optical microscopy to detect asphaltene instability in batch experiments. Detection of instability can take months with this setup when the precipitant concentration is low.

A capillary deposition apparatus has been developed that can test for asphaltene instability at low precipitant concentrations in short periods of time. This configuration is useful because it does not require asphaltene aggregates to grow to a size of ~0.5 microns before detection is possible. There is a continuous supply of unstable asphaltenes that are able to form a deposit on the capillary wall. The asphaltene deposit causes an increase in the differential pressure across the capillary test section. In addition to the detection of instability, capillary deposition can provide insight into the deposition/stability mechanism for asphaltenes. The aggregation and deposition of asphaltenes at low precipitant concentrations questions the applicability of previous experiments and thermodynamic models to predict asphaltene stability.

[1] T. Maqbool, A.T. Balgoa, and H.S. Fogler, “Revisiting Asphaltene Precipitation from Crude Oils: A Case of Neglected Kinetic Effects,” Energy & Fuels, vol. 23, Jul. 2009, pp. 3681-3686.

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