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Asphaltene precipitation and deposition is a serious issue in all facets of petroleum production and processing. Despite the numerous experimental efforts concerning asphaltenes, the effect of temperature on asphaltene precipitation and aggregation in live oils remains still an elusive and controversial subject in the available literature. In this work, a series of high pressure-high temperature depressurization experiments were designed to assess the effect of temperature on asphaltene precipitation and aggregation in light live oils. Asphaltene related experiments were performed using high pressure microscope and high pressure-high temperature filtration setup on a light live oil with low asphaltene content and a high potential of asphaltene formation. The results of the experiments were interpreted in terms of asphaltene onset pressure, size distribution and average diameter of the aggregates, fractal dimension of the asphaltene aggregates, and the amount of precipitated asphaltene. It was found that depressurization process at higher temperatures results in higher asphaltene onset pressure or earlier formation of the asphaltenes. Visualization experiments showed that asphaltene aggregates in light live oil are pressure-temperature fractal structures. Depressurization process at lower temperatures led to the formation of highly porous and loose aggregate structures with relatively low fractal dimensions. As the temperature of the depressurization process decreases the mechanism of asphaltene aggregation changes gradually from reaction limited aggregation to diffusion limited aggregation. This research reveals that temperature has crucial effects on asphaltene aggregation process in light live oils at elevated pressures which is of great importance for asphaltene handling and separation. This article is protected by copyright. All rights reserved

Despite the numerous experimental studies concerning asphaltene, the extent of reversibility of asphaltene aggregation at reservoir conditions remains still an elusive and controversial issue in the available literature. In this work, a series of depressurization and repressurization experiments were performed on three different live oils for qualitative and quantitative evaluation of the reversibility of asphaltene aggregation under typical pressure and temperature conditions of oil fields. The obtained results reveal that the kinetics and the extent of reversibility of asphaltene aggregation at elevated pressure and temperature are majorly controlled by the characteristics of the reservoir fluid and asphaltene formation driving forces induced by change in pressure and temperature. It is observed that asphaltene aggregation in problematic/unstable live oils tends to be a reversible process upon pressure change with subtle to intense hysteresis dependent on the temperature of the system. Furthermore, temperature reversibility experiments show severe hysteresis in precipitation and redissolution of asphaltene which is intensified by temperature decrement. In addition, at lower temperatures the kinetics of asphaltene redissolution is slower than the kinetics of aggregation. For the case of unproblematic/stable live oil, although asphaltene particles are formed by change in pressure and temperature, the particles do not severely grow and the aggregation process exhibits complete reversibility with no apparent hysteresis. The major interest of presented results is their important implications for better understanding and formulation of asphaltene phase behavior at reservoir conditions.