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

3.1 Introduction 
Wax may be of mineral, plant, or animal origin – they are solid at normal 
temperatures and insoluble in water. 
The term ‘wax’ is applied to a large number of chemically very different 
compounds with a range of properties (beeswax is an example). Commercially 
produced wax has been widely used – both domestically and industrially. 
In the oil industry, wax refers to solids deposited from reservoir hydrocarbon 
fluids. Wax consists of a homologous series of hydrocarbons, predominantly a 
mixture of linear (i.e. n-paraffins), branched (i.e. iso-paraffins) and cyclic (i.e. 
naphthenic) compounds. 
Paraffins form a large part of wax, hence the term “paraffin”, “paraffin wax”, 
and “paraffin deposition” is largely used in the oil industry. Paraffin wax 
commonly exhibits two types of crystalline structures – either macrocrystalline 
structure or microcrystalline structure. The macrocrystalline wax has well-
formed crystal shapes such as needle-like and plate-like, while the 
microcrystalline wax has poorly defined crystal shapes. 
In petroleum production (and transportation), the deposited wax crystals 
commonly entrap and/or combine with a variety of organic and inorganic 
materials (liquids and/or solids) that may be present in the system. 
This not only increases the bulk of wax deposits, but also leads to different 
deposit appearances – these waxes can vary from a “mushy” liquid to a firm 
hard solid and can have a variety of colours between white and dark. 
Wax deposits can be found in many places including the reservoir formation, 
producing wells, subsea and surface pipelines, separators and storage tanks. 
The deposition can cause a restriction in flow, a decrease in production rate, 
mechanical problems and a reduction in production efficiency. Thus, wax 
problems have been found in many oil-producing areas worldwide. 
Wax deposition has been a major economic and safety concern since the 
inception of petroleum production. Over the century, industry has directed 
significant efforts toward understanding the nature of wax deposition, 
predicting where problems might occur and alleviating and/or avoiding wax 
problems. 
The literature about wax deposition can be traced as far back as 1860’s (Bone 
et al., 1865). Between 1920’s and 1950’s, there were a few publications 
related to the mechanism of paraffin deposition and its control (Buchler et al., 
1927; Bennett et al., 1944; Schanen, 1945; Fontana, 1946; Horne et al., 1946; 
Nelson et al., 1949; Clark, 1951), while Shock et al. (1955) summarized the 
studies during that period of time. 

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TOPIC 3: Wax Deposition 
 
 
 
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NIVERSITY B41OA December 2018 v3 
The early studies did not clearly differentiate between wax deposition and the 
deposition of other organic species, such as asphalts and tars. Nevertheless 
paraffin deposition findings, from these earlier studies, are still relevant today, 
The major points of note are as follows: 
•
Wax deposits are largely paraffins, with smaller amounts of 
naphthenes and aromatics. 
•
It is generally believed that the n-paraffins are the principle constituents 
of the macrocrystalline wax. 
•
The iso-paraffins are the major constituents of microcrystalline wax. 
•
Naphthenes 
and 
aromatic 
compounds 
also 
contribute 
to 
microcrystalline wax, as well as having a marked effect on the crystal 
growth of macrocrystalline wax. 
•
Clark (1951) found that the wax crystal type depended also on 
crystallisation conditions.