Analysis of the asphaltene properties of heavy crude oil under ultrasonic and microwave irradiation

Abstract

Using new technologies are quite significant in the production and development of heavy oil reservoirs. In this study, the effects of microwave (MW) and ultrasonic (US) waves on the properties of Ellam heavy crude oil of the southwest oil reservoirs of Iran have been investigated. Experimental results show that different processes occur in samples under MW radiation for 5, 10, 15 and 20min. Under MW for 5 and 10min we have viscosity reductions from 15.836 mPa.s to 12.234 mPa.s and 11.122 mPa.s, respectively. This is due to volume expansion with decreasing viscosifying component and high absorption capacity of heavy molecules of oil toward MW that charges the cracking process. US waves increase the viscosity of oil for all time durations because the power from US waves causes the evaporation of light compounds. Next, the effect of MW and US radiation on the asphaltene clusters using microscopic images was investigated. Results of asphaltene particle size distribution show that increasing duration of wave radiation makes the particles smaller, and the size range of asphaltene particles in the samples under MW radiation is much smaller than for the samples under US wave radiation. Moreover, in samples under MW radiation, the large particles cannot be seen. Consequently, the average particle size of asphaltene is smaller in samples under US wave radiation. But the particle size range is high, and large-sized particles in different time intervals of US radiation are observed. The results of scanning electron microscopy show that microwaves make the asphaltene conglomerate forming particles smaller and more regular in shape than the primary state, whereas ultrasonic waves completely alter the structure of the asphaltene particles, creating asphaltene clusters with a different structure. Based on the Fourier transform infrared spectra, ultrasonic exposure increases the cracking rate of the weaker bands and the condensation of aliphatic bands more than does exposure to microwaves, due to an increase in the intensity of the spectra.