The Effect of Temperature on the Size and the Deposition of Asphaltene Particles

Abstract

Summary The deposition of asphaltene as a main component of crude oil is considerably affected by temperature. Despite the studies on influencing factors on deposition and size of asphaltene particles, no experimental research was previously conducted on the simultaneous impact of temperature on asphaltene particle size and deposition. In this study, the asphaltene deposit mass was measured within a Couette device at various temperatures ranging between 20 and 65°C under a constant angular velocity. Furthermore, the asphaltene particle size was simultaneously measured to investigate the relationship between deposition mass and asphaltene particle size and also to validate the concept of critical particle size. A digital microscope was used to measure the size of unstable asphaltene particles in oil. Asphaltene solubility and oil viscosity were measured to understand the deposition mechanisms. The analysis of microscopic images indicated that larger asphaltene particles are produced at higher temperatures. Although the total mass of the deposit was decreased with temperature, the deposition fraction, defined as mass fraction of total unstable asphaltene particles that deposit, was increased. Higher fraction of deposition was found for larger particles that is in contradiction to the previously introduced critical particle size concept. Additionally, the effect of solubility was found to be dominant in comparison with viscosity from the point of view of the total mass of the deposit. For the oil sample investigated in this study, a 45°C increase in temperature reduced the total mass of the deposit by 46.84%.