An Investigation of the Effect of Asphaltene Polydispersity on Asphaltene Precipitation and Deposition Tendencies

It is well-known that asphaltenes are a polydisperse
fraction present
in crude oil with a broad distribution of sizes and molecular characteristics.
However, in practice, asphaltenes are often treated both in the laboratory
and in modeling work as a monodisperse fraction. In this work, asphaltene
deposition tests with two model oils with the same total amount of
asphaltenes but with different asphaltene polydispersity distributions
were conducted using a high-pressure, high-temperature packed-bed
deposition column. Although the asphaltenes used to prepare the two
oils were extracted from the same source, a drastic difference in
the amount of asphaltene deposited was observed, which is attributed
to the difference in the asphaltene polydispersity between the two
samples. Additionally, using UV–visible spectroscopy, it is
possible to observe some similarities between the aromaticity of asphaltene
subfractions obtained from different geographical locations. Modeling
results provide additional insights into the impact of asphaltene
polydispersity on the onset and the amount of asphaltene precipitation.
The results presented in this work suggest that asphaltene polydispersity
plays a major role in determining asphaltene precipitation and deposition
tendencies observed in different oils.