Influences of Ultrasonic Radiation on Asphaltene Behavior With and Without Solvent Effects

Abstract

Abstract Asphaltic crude oils have caused serious problems in the oil industry all over the world. The major objectives of this experimental study are to investigate the influences of ultrasonic radiation on the behavior of asphaltene in the UAE crude oil, with considerations of temperature and solvent concentration effects. To achieve the goals of the study, two sets of experiments were undertaken. In the first experimental set, many identical crude oil samples having initial asphaltene content of 1.76 wt. % were subjected to different time intervals of ultrasonic radiation. Viscosity of these oil samples was measured under different temperatures. In addition, microscopic images of the centrifuged oil samples and Differential Thermal Analysis (DTA) of extracted asphaltene clusters were carried-out. In the second set of experiments, asphaltic oil samples of different solvent (toluene) concentrations were subjected to different intervals of ultrasonic radiation and under different conditions of temperature. Again, variation of oil viscosity with temperature was measured. The results showed that subjection of the crude oil to ultrasonic radiation decreases the size of asphaltene clusters. Consequently, this effect increases the suspension of asphaltene in the crude oil and reduces/prevents its tendency to precipitate at 10 minutes or more radiation time. Furthermore, the results indicated that the use of ultrasonic radiation with toluene solutions increases the solubility of asphaltene in the crude oil at 10 minutes or more ultrasonic radiation time, but with more reduction in oil viscosity than that one with non-solvated oil. The application of the obtained results of the study could have real impact on the future development of simulation models, prevention of asphaltene precipitation and elimination, or at least minimization of the expected problems of asphaltene deposition. Introduction and Review Asphaltene species is defined as the heavy fraction of the crude oil, which is insoluble in normal heptane, but soluble in an aromatic solvent. Aromatic solvents and oil-soluble amphiphiles are recognized as asphaltene precipitates inhibitors. Aromatic solvents, such as toluene and xylene, have been widely used to clean up near wellbore holes. Many other solvents were investigated as substitutes of these common solvents. Samuelson (1992) investigated many solvent alternates and proposed using combined non-aromatic solvents. The study suggested using co-solvents/solvent mixtures and indicated that the solvency of asphaltenes was enhanced by the addition of amines. The solubility parameter of asphaltene using heptane, cyclohexane, and toluene were 9.5, 7.5, 8.2, and 8.9 (cal/cm3)0.5, respectively (Speight, 1980).