Investigation of Crystallisation in Crude Oil with New Rheometer

Transportation of crude oils in pipelines can be challenging due to the high-molecular-weight paraffins and asphaltenes therein. With an MCR Rheometer, from Anton Paar (Austria), combined with a temperature device and a microscope the behavior of these paraffins at different temperatures can be investigated. At high temperatures, the paraffins are dissolved in the crude oil. During transportation through pipe lines, the temperature of the oil can drop. If the oil temperature decreases to below its wax-appearance temperature (cloud point), or even to below the pour point, the solubility of the paraffins decreases and they start to crystallize, or precipitate out of the crude oil. The percentage of paraffin inhibitors that need to be added to prevent wax precipitation at any given temperature depends on the crude-oil composition. Thus, it is essential to investigate the effectiveness of paraffin inhibitors for each particular composition.

Combining an MCR Rheometer with a microscope allows the crystallisation process to be observed during rheometry measurements as the crude oil is cooled. The size and growth rate of the paraffin crystals can be closely monitored. Furthermore, a pressure cell can be combined with the MCR Rheometer to additionally simulate the pressure that is applied during the pumping process of crude oil. This setup provides comprehensive results for crystallisation in crude oil. Particularly valuable are the viscosity values that can be achieved for crude oil at temperatures and pressures for which no test data is otherwise available.