The Nature of Asphaltenes
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.
Roemex are able to provide a comprehensive
analysis of any asphaltene problem both from the prevention
viewpoint and after any asphaltene has flocculated. Roemex’s
product RX 33/1 is unique in the market place as a specialist
dissolver giving complete dissolution of both the resin structure
and the core component of the asphaltene particle. Thus ensure
complete removal (unlike general aromatic solvents such as
Xylene) of asphaltene deposits
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Asphaltene
