B41oa oil and Gas Processing Section a flow Assurance Heriot-Watt University

3.7.1 Mechanical Methods 
As the name implies, the wax deposits are removed by mechanical means. 
For example, if there are wax deposits inside the well tubing, various 
techniques such as gauge cutters or wireline bailers could be used for 
mechanical removal of wax deposits. 
In pipeline situations, the use of “pigs” to remove wax deposits is the most 
common method. In this scenario: 
•
A pig (simply a close fitted cylindrical plug which is designed to scrape 
off wax deposits) is placed inside the pig launcher (at one end of the 
pipeline). 
•
The pig is pushed along the pipeline by the application of fluid hydraulic 
pressure behind it. 
•
The pig, together with scraped off wax deposits, is finally recovered in 
the pig receiver (at the other end of the pipeline). 
•
Various types of pigs have been developed and are widely used 
throughout the Petroleum industry. 
3.7.2 Thermal Methods 
These methods are based on increasing the system temperature in order to 
dissolve or loosen the wax deposits. Hot oiling, or hot water injection, are 
among the available thermal methods. 

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TOPIC 3: Wax Deposition 
 
 
 
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NIVERSITY B41OA December 2018 v3 
In this case, hot fluid is injected inside the wellbore in order to dissolve the wax 
deposits. The treatment is relatively cheap, however, there is significant 
debate as to its effectiveness – this is because large amounts of thermal 
energy are wasted through heat transfer to the surrounding. 
There may be insufficient thermal energy to dislodge heavier wax deposits that 
tend to lodge at greater depths in the well – this is because a much higher 
temperature is needed when the melting point of the wax is higher (typically 
heavier waxed form deeper in the well and have higher melting points). 
Another argument against this method is that, if injection of waxy fluids into the 
reservoir occurs, then wax deposit might occur in the near-wellbore region; 
thus, reducing the well productivity. Some of these shortcomings could be 
resolved by using coiled tubing (for the placement of hot fluid), though this 
could significantly increase the costs. 
In order to reduce the heat loss to the surrounding, several methods have 
been devised to apply heat only at the point of wax deposits (these include, for 
instance, electrical heating). 
Another novel method uses a mixture of two chemicals which produce 
considerable exothermic heat of reaction. The reaction may be delayed by 
using appropriate retarder (to give adequate time for the reaction mixture to 
reach to the area of wax deposition). 
This method has successfully been used to remove wax deposits in both 
wellbore and pipelines. However, the cost of this operation is considerably 
higher than conventional hot oil treatment.