289131 Properties Controlling Aggregation and Precipitation Rates of Asphaltenes

Monday, October 29, 2012: 10:30 AM
301 (Convention Center )
Nasim Haji Akbari Balou and H. Scott Fogler, Chemical Engineering, The University of Michigan, Ann Arbor, MI

Properties Controlling Aggregation and Precipitation Rate of Asphaltenes

Nasim Haji Akbari Balou1 and H. Scott Fogler1

1The University of Michigan, Department of Chemical Engineering, Ann Arbor, MI

Asphaltenes are the heaviest and most polar fraction of crude oil and can precipitate due to change in temperature, pressure and composition. Their precipitation and deposition can lead to serious economical impacts in the oil industry. For years it was believed that instability of asphaltenes can be detected shortly after changing the operational conditions. However, recent studies in our group demonstrated that asphaltene-precipitant mixtures can be unstable even at very low precipitant concentrations and it can take weeks and sometimes even months to detect such instabilities [1, 2]. We have observed that this kinetic behavior is universal among different crude oils. However, the precipitation rates strongly depend on the properties of the crude oil. Our goal in this study is to identify the properties that are responsible for differing aggregation and precipitation kinetics. Due to the complexity of crude oil, model mixtures are used as alternatives to measure the precipitation rates for different solvents and asphaltenes.

A new analysis approach has been developed to estimate the precipitation rates by accounting for the properties governing the aggregation kinetics such as viscosity and solubility parameter. The results show that precipitation rates strongly depend on the solvent used for asphaltenes stabilization. However, we show that under certain assumptions all the differences for different types of asphaltenes and solvents can be well explained, and their precipitation rates collapse onto a single curve. The results also demonstrate that not only the solvent, but also the asphaltene content of the solution can play an important role in controlling the aggregation rate. We have observed that solutions with lower asphaltene content show a higher tendency for destabilization and eventual precipitation. These findings will lead to a better understanding of the properties that govern the destabilization and growth processes of asphaltenes.

[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, no. 7 , pp. 3681-3686, Jul. 2009.

[2] M.Hoepfner, C.V.B Favero and H. S. Fogler, Understanding the Instability of Asphaltenes, Oral at Petrophase 2011, London.

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