The wax appearance temperature (WAT), also known as the cloud point, is an important characteristic to evaluate the possible wax precipitation of a given fluid. It is defined as the temperature at which a crude oil first precipitates. In the petroleum industry, such wax depositions in pipelines and reservoirs can lead to many issues, including a reduced flow or even a blocked pipeline, with subsequent important production problems. Different techniques have been developed to measure the WAT of a crude oil but the method using DSC is commonly used for its rapidity, convenience and accuracy.
Approximately 600 mg of three different oils were introduced in µDSC7 Evo batch vessels. After a heating phase up to 80°C, the samples were cooled down from 80°C to 0°C at 1°C/min. To calculate the WAT, the onset temperature of the first peak has been considered (intersection of the baseline and the tangent at the first peak inflection point), see figure 2.
Providing the knowledge of the heat of crystallization of the “pure” waxes, CalistoTM data treatment software can determine the percentage of converted wax versus temperature.