Description Of Wax

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2.12.1 Wax Description: Wax is composed of high molecular weight paraffins and asphaltenes. At reservoir temperature (70 – 150oC and pressure (50 – 100MPa), wax molecules are dissolved in the crude oil. However, as the crude oil flows through a subsea pipeline the temperature resting on the ocean floor at a temperature of 4oC, the temperature of the oil eventually decreases below its cloud point temperature (or wax appearance temperature, WAT) because of the heat losses to the environment. The solubility of wax decreases remarkably as the temperature decreases. At this particular condition wax molecules start to precipitate out of the crude oil (Lee, 2008). Wax is mostly found as a white, odourless, tasteless, waxy solid with a typical melting point between about 47oC and 64oC (116.6oF to 147.2oF), and having a density of around 0.856g/cm3 (Kaye and Laby, 2010). They are mainly long-chain alkanes with 20 to 50 carbon atoms, but also contain minor quantities of branched and…show more content…
The fact that solubility of high molecular weight paraffins decreases drastically with decreasing temperature, leads to the formation of stable wax crystals at low temperatures. The wax particles start appearing in the crude oil, when the oil temperature drop below its solubility limit (Kelechukwu and Md Yassin, 2008) that is the wax appearance temperature (cloud point temperature). A typical wax precipitation curve shows the amount of paraffin wax precipitated from condensate, as illustrated in Figure 2.22. It depends on the extent to which the paraffin wax mixture is cooled down below the WAT. In crude oil and condensates, wax precipitation depends on its solubility. The heaviest waxes are least soluble and they precipitate first and upon further cooling, the lighter ones
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