Characterization of wax appearance temperature of model oils using laser-induced voltage

Abstract

As a component of crude oils, wax plays an important part in the flowability of waxy oils. The deposition of waxes poses a significant challenge in petroleum production. This paper proposes laser-induced voltage (LIV) to measure the wax appearance temperature (WAT). With a decreased temperature, the peak of the LIV signal (VP) decreases with a greater slope until the inflection point (TLIV) after that wax precipitates from the oil. After which, VP changes more slowly. Thus, the TLIV is confirmed as the WAT. Furthermore, the WAT was measured using conventional differential scanning calorimetry, and the results of the two methods are consistent. When a laser irradiates the oil sample, plasma is generated in the liquid due to cascade ionization and multiphoton absorption. The plasma moves based on the effects of an external electric field and generates the LIV. However, temperature changes influence variations in the LIV for waxy oils. In addition, when paraffin precipitates from the oil, it exits as sediment at the bottom of a cuvette, which can impede plasma movement. Therefore, there will be significant differences in the trends before and after WAT. This study demonstrates that LIV offers a way to measure WAT in waxy oils.