The nature of asplaltene

A number of crude producing regions notably in South America and Canada have problems with high concentrations of asphaltene substances. It is important to note that there is no such thing as a chemical defined asphaltene having a unique and specific chemical structure. What has been established is that asphaltenes have common properties and exhibit common chemical structures and molecular groups regardless of crude origin.

In comparison to paraffin, asphaltenes are generally a more defined component of crude oil, in that they are soluble in toluene but insoluble in lower n- alkanes such as pentane and hexane.

Asphaltene deposits as observed in the field can vary greatly in appearance. Sometimes they are shiny and black with graphite like appearance, on other occasions they form brown sticky soft deposits. It should be noted that asphaltenes often co-precipitate with wax and even scale. It is known that asphaltenes are dispersed as colloids in the crude and are stabilised by other components of the crude oil. This has led to a number of models for trying to understand how these colloidal particles are arranged.

Treatment and Prevention

The best option would be to design and/or control conditions so that asphaltenes could not form. Such conditions however would in general compromise normal production operating conditions and would not be economically viable. A number of chemical treatments have been developed, namely

Inhibitors and dispersants

Dissolvers

Batch and squeeze treatments

Evaluations of specific crudes by a number of test methodologies are essential in selecting and designing the correct treatment strategy.