Paraffin waxes contaminate tight oils and remain on the walls of railcars, crude oil tank walls, and piping. They are also known to foul the preheat sections of crude heat exchangers (before they are removed in the crude desalter). Paraffin waxes that stick to piping and vessel walls can trap amines against the walls, which can create localized corrosion.

The severe fouling in heat exchangers upstream of the desalter was initially a surprise to many refiners - fouling is typically worse in the hotter exchangers that are downstream of the desalter. Refiners now monitor the crude preheat exchangers more closely, and are working with both automation and chemical companies to counter this fouling and corrosion potential.

With the ongoing trend in deep water developments where the temperature (at the sea-base wellhead) is lower than the cloud point of most crude oils and cold, flow assurance is a major issue. In fact, the increasing exploitation of deepwater fields makes essential to understand the mechanism of wax deposition and the methods available to prevent and remediate wax deposits in both production and export systems. This often involves a combination of chemical treatments, pigging and insulation to deliver a wax control and management strategy suitable for a particular development. The avoidance of wax fouling (or remediation of wax deposition) is one of the key aspect of flow assurance and in order to develop solutions to the wax deposition problem is necessary to get a deep understanding of the crystallization phenomena in which the crude oil composition, particularly the content of high-molecular-weight paraffins and asphaltene constituents have a significant impact.

Further to the chemical composition and behavior of wax, in a typical wax phase various types of compounds are present—n-paraffins constituents are large percentage (90-95% w/w) of the wax phase and the iso-paraffins account for the remainder. While the n-paraffins are generally expected to be able to form the wax phase independent of the molecular weight (as long as the n-paraffins are solid), this is not the case with the iso-paraffins. The reduced melting temperatures of any of the constituents lower the tendency or ability of those constituents to form a wax phase. Alkanes show regular increase in melting point as the molecular weight increases.

Nonpolar chemical species, such as alkanes are weakly attracted to each other by intermolecular Van der Waal’s forces, which are effective over very small distances result from induced polarization of the electron clouds in molecules. The Van der Waal’s forces increase with an increase in molecular size, but other factors are also involved—the effect of branching on melting point can be explained by invoking Van der Waal’s forces. Branched alkanes are more spherical than the straight-chain alkanes and, as a result, have smaller surface areas, decreased Van der Waal’s forces, and consequently a lower melting point. The intermolecular or Van der Waal’s are overcome at a lower temperature for iso-paraffins.