Paraffin and Wax in Crude Oils
The waxes present in most crude oils include n-alkanes, iso-alkanes, alkyl cyclic compounds and alkyl aromatics. In most crude n-Alkanes are the predominant species. The amount and distribution of these n- Alkanes is crude specific. Short-branched chains are the next most common. These have a significant impact on wax deposition characteristics.
There is no standard definition for wax content but it is generally accepted that n-alkanes from C18 to C40 represent waxy material. Paraffin solubility not only depends on the composition of the crude but also the temperature and pressure.
The wax appearance temperature (WAT) is the temperature at which, on a cooling cycle, the crude oil first precipitates solid wax. This is arguably the single most important characteristic in examining wax deposition potential in crude oil. The deposition of wax leads to several problems in reduced production and impaired flow assurance. Severe deposition can lead to loss of production and pipeline blockage etc.
Deposit Control
The main options for removing deposits are as listed below:
- Pigging – A cleaning pig launched into a pipe to mechanically scrape wax from the pipe-wall and distribute it within the crude in front of the pig.
- Thermal Treatment – if the temperature of the oil can be maintained or increased above the WAT e.g. by increasing the flow rate the wax deposits will either not be laid down or will be softened and removed.
- Chemical Treatment – a wide range of solvents are available, the most popular being substituted aromatics (HAN etc) blended with gas oil. Chlorinated solvents are now precluded from use due to environmental concerns.
- Wax Inhibitors – there are four main categories of such chemical additives:
o Crystal Modifiers
o Pour Point Depressants
o Dispersants
o Surfactants
RAKHARA’s Paraffin / Wax treatment Range – RCT 5400 Series
RAKHARA’s Paraffins / Wax Treatment Chemicals RCT 5400 Series – is a complete range of Wax Inhibition / Pour Point Depressant chemicals, successfully developed by RAKHARA have been proven to be effective in reducing the pour points of many crudes found in Indonesia.
