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• The joint effects of ultrasound and solvation on oil viscosity were investigated. • The analysis of asphaltene structure by using FTIR and microscopy techniques. • The lowest viscosity was found for irradiation-then-dilution-treated crude oil. • Ultrasonic solvation reduced the ratio of aromatic rings to aliphatic chains. Production from heavy oil reservoirs faces challenges, such as accumulating heavy hydrocarbon materials like asphaltenes near the wellbore, resulting in low recovery rates. To enhance recovery and prevent formation damage, methods often focus on reducing oil viscosity. Solvents and ultrasonic waves have proven effective in this regard, though challenges related to asphaltene aggregation and structural changes persist. This study explores the impact of simultaneously applying ultrasonic radiation and solvents on crude oil's viscosity and asphaltene structure. Toluene and n-heptane, representing aromatic and paraffinic solvents, were employed. Viscosity measurements and Fourier transform infrared spectroscopy tests were conducted on sonicated crude oil diluted with solvents and solvent-diluted crude oil subjected to sonication. Results were compared to untreated and separately treated crude oil samples. The study found that the most effective viscosity reduction method involved blending sonicated oil with toluene under optimal radiation time and concentration conditions. Two primary mechanisms for viscosity reduction were identified. Firstly, there was the dissolution and aggregation of asphaltene clusters. Secondly, chemical changes in asphaltene molecular structure were observed, altering the ratio of aromatic rings to aliphatic chains. This research offers potential insights into how ultrasonication and solvation interact to modify crude oil structure. [Display omitted] [ABSTRACT FROM AUTHOR]

Production from heavy asphaltenic oil reservoirs poses several challenges that require new and innovative techniques for improved production and recovery. The main objective of this study is to experimentally investigate the influences of ultrasonic waves and solvent on oil viscosity, asphaltene precipitation behavior, and recovery of a heavy asphaltenic crude oil. This study is divided into two main parts. In the first part, crude oil samples were subjected to ultrasonic radiation with a frequency of 20 kHz and varying output powers (30, 60, and 100 W) for various durations. The viscosity of each oil sample was measured immediately after stopping ultrasonic radiation and also after 24 h of irradiation. An optimum time for ultrasound radiation was determined when the cooled-down radiated oil reached a minimum viscosity. We then measured the viscosity of the ultrasonically treated oil samples blended with a solvent (i.e., n-heptane) to assess the synergetic effect of ultrasonic radiation and solvation on the oil viscosity. In the second part, the application of ultrasonic radiation on the asphaltene aggregates and oil recovery was examined using solvent flooding in a transparent porous medium. Four sets of experiments were undertaken where the solvent was injected into the micromodel saturated with the untreated and ultrasonically treated oil free from or blended with the solvent. The results showed that ultrasonic treatment decreased the size of asphaltene aggregates and consequently reduced the viscosity of the crude oil. As a result, the suspension of asphaltene in the ultrasonically treated oil increased and reduced its tendency to precipitate at the optimum radiation time. Furthermore, the results indicated that the combined use of ultrasound and solvent had the greatest reduction in the oil viscosity compared to the untreated crude oil with ultrasonic waves or solvent. • The joint effect of ultrasonic radiation and solvent on viscosity and asphaltene aggregation of crude oil was investigated. • A synergy in viscosity reduction was found when the solvated crude oil was subjected to ultrasonic radiation. • The flooding tests showed that ultrasonic radiation locally decreased the size and precipitation of asphaltene aggregates. • The ultrasonicated oil was displaced more efficiently on the local pore space. • Considerably lower asphaltene precipitation was found when the radiated oil was displaced by the solvent. [ABSTRACT FROM AUTHOR]

In this work, the effects of four different chemical inhibitors, namely a polymeric surfactant, synthesized γ-Al2O3/NiO nanoparticles, epoxy resin, and canola oil to inhibit asphaltene precipitation in three different crude oils collected from various oil fields located in southern Iran. A high-pressure solid detection apparatus was employed to measure the onset point of asphaltene precipitation in crude oils with API ranging between 35 and 38 and various characteristics in the presence of the inhibitors in a wide range of concentrations ranging 0–20 wt. % at a high pressure of 2,000 psi and ambient temperature. The elemental composition of resin and asphaltene fractions in the crude oils was identified using a LEC elemental analyzer. The results showed that all fractions of precipitated asphaltenes were composed of low ratios of H (hydrogen)/C (carbon), which were an indication of large instability. Moreover, the screening experiments showed that the polymeric surfactant inhibitor with a base-nature was more efficacious with most oil samples due to the presence of high content (73%) of resin in this type of inhibitor. Besides, they can be used as a well-candidate for other oils not assessed in this work due to their high polarity and also compatibility with the structure of studied asphaltenes. It was found that the polymeric surfactant γ-Al2O3/NiO nanoparticles had the highest inhibition performance in comparison with the epoxy resin and canola oil. [ABSTRACT FROM AUTHOR]