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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]

• Heavy oil_solvent mixtures can be assumed as a binary mixture in EOR processes. • New correlations were proposed for oil_solvent binary interaction coefficients. • Using correlations, we eliminate the need for time-consuming optimizations. • P_x phase diagrams can be estimated properly by using binary mixture assumption. Conventional production methods in heavy oil reservoirs are not efficient primarily due to the high viscosity of the oil. Several methods such as VAPEX and ES-SAGD have been developed to overcome production challenges from these reservoirs, which mainly rely on oil viscosity reduction. Solvent injection dilutes the oil and produces a complex asymmetric mixture. It is difficult to study the phase behavior of oil due to the diversity of its components, and it gets more complicated with the addition of solvent. One of the assumptions to simplify the problem is considering heavy oil as a single pseudo component and investigating the thermophysical properties of binary mixtures with diluents. This study collected and evaluated more than 1000 experimental data on various types of heavy oil/bitumen and several hydrocarbon and non-hydrocarbon solvents. The data were divided into two groups, below and above the critical temperature of the solvent, according to experimental temperatures. Modeling of mixture phase behavior as a binary mixture was performed using the advanced Peng-Robinson equation of state (APR-EoS). EoS tuning to match the experimental data was performed by optimizing the binary interaction coefficients (k ij). The results showed that the binary mixture assumption could be used as a practical approach to construct pressure-composition phase diagrams. Optimized values of k ij were proposed as two empirical correlations according to the dimensionless ratio T co / T cs (oil critical temperature to solvent critical temperature). The model constructed using these correlations showed an average deviation of about 16% compared to experimental data. It is necessary to note that the vapor-liquid-liquid three-phase regions may occur in a heavy oil/bitumen and solvent mixture. But according to the Gibbs phase rule, with two components and three phases in the system, the degree of freedom equals one. So, investigating the effects of pressure change on three-phase regions is not possible using this model. [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]

• Simultaneous Effects of ultrasonic irradiation and α-Fe 2 O 3 nanoparticles (NPs) on crude oil properties were investigated. • The viscosity of irradiated oil with NPs was found to be less than that of irradiated oil without NPs. • The post-pyrolysis mass loss of the irradiated NP-added oil was greater than that of non-irradiated oil with/without NPs. • Regarding the thermogravimetric tests, the addition of NPs and the ultrasonic irradiation work in the opposite direction. In this work, the effects of ultrasonic irradiation assisted by α-Fe 2 O 3 nanoparticles (NPs) on the evolution of viscosity and thermal properties of crude oil are evaluated. A viscous crude oil with a high amount of asphaltene (∼20% by mass) was used for ultrasonication over different exposure times and nanoparticle concentrations. The viscosity of the oil before and after ultrasonic irradiation was measured with and without nanoparticles. Experimental results indicated that the viscosity of irradiated oil containing nanoparticles at optimum conditions was lower than the viscosity of nanoparticle-free irradiated oil. The thermal behavior of the irradiated crude oil mixed with nanoparticles at optimum conditions was examined using the TGA/DTA methods. The results showed a non-complementary effect of ultrasonic irradiation and nanoparticles on the weight loss and the amount of residual oil at both the end of the pyrolysis and oxidation stages, representing that addition of the α-Fe 2 O 3 NPs to the crude oil and the ultrasonication of the crude oil work in the opposite direction. Based on the TG/DTA data, the kinetic parameters of the pyrolysis and oxidation reactions were estimated. It was found that the simultaneous use of ultrasonic irradiation and nanoparticles sharply decreased the activation energy of the oxidation reactions, but had almost no effect on the activation energy of the pyrolysis reactions. The results of this paper provide an insight into the effectiveness of in-situ combustion enhanced oil recovery, which depends on viscosity reduction and the rate at which heat is generated. [ABSTRACT FROM AUTHOR]

Highlights In this study, the influence of ultrasonic waves on the viscosity and thermal behaviour of a crude oil with high asphaltene content at different irradiation times and powers/frequencies was investigated. It was found that the ultrasonic radiation significantly reduced the oil viscosity before the oil cooled down. The viscosity was then remeasured after the irradiated oil cooled down to the ambient temperature to evaluate the reversibility in viscosity at various time intervals. For each ultrasonic frequency, an optimum irradiation time was found at which the cooled-down irradiated oil reached a minimum viscosity. For the ultrasonic radiation with a frequency of 46 kHz and an output power of 50 W, it was found that the permanent viscosity loss of the cooled-down oil irradiated for an optimum time of 8 min was 10 %. The effects of ultrasonic irradiation on thermal behaviour of the oil were analysed using thermogravimetric and differential thermal (TGA/DTA) methods to evaluate the relation between changes in viscosity and thermal properties of the oil. It was found that the weight loss of the irradiated-oil was more than that of the non-irradiated oil at the end of both the pyrolysis and oxidation stages. [ABSTRACT FROM AUTHOR]