Quantitative Analysis of Ultrasonic Wave Radiation on Reversibility and Kinetics of Asphaltene Flocculation

Recently, it was found that ultrasonic wave technology can be used as a method for asphaltene deposits removal from the near wellbore region. However, ultrasounds can affect asphaltene resolution.In this work, asphaltene resolution in several crude oil samples exposed to ultrasonic waves for different time intervals is studied by confocal microscopy. The colloidal structure of flocks is described by analysis of asphaltene particle size distribution to investigate ultrasonic application in solving asphaltene deposition problems.. The results show that for the first 90 minutes of flocculation time, the size of aggregates increases rapidly, and reaction limited aggregation model matches well with the experimental data for all samples. But, after 90 minutes, a reduction in aggregate size of sonicated samples is observed, meanwhile the aggregates size of non-sonicated oil sample increases in close agreement with the diffusion limited aggregation model. It has been found that asphaltene flocculation of sonicated samples can not obey classic DLVO theory of colloidal dispersions due to partial reversibility of flocculation. An optimum value for ultrasonic radiation time, at which the viscosity and flocculation rate of asphaltenic crude oils reduces to its minimum, is found to be close to 10 minute for Sarvak crude oil.