Last years, the structure of oil reserves both in the world and in Russia is constantly changes to increasing of hard-to-recover reserves share. A significant part of hard-to-recover reserves is represented by high-viscosity heavy oils. According to the classification of reserves and resources of oil and combustible gases of the Russian Federation, oil with a viscosity of more than 30 mPa·s is high-viscosity oils, their share is 55% of the total Russian oil reserves. During production of high-viscosity oil, especially by enhanced oil recovery methods, and during heavy hydrocarbons transportation and processing there is a high probability of changing of oil system phase state and precipitation of resin-asphaltene substances. Therefore, fluid colloidal stability has decisive importance. The study of oil system stability allows a more reasonable approach to the choice of solvents to improve the oil rheological properties and prevent the precipitation of resin -asphaltene substances.
The article is devoted to preliminary assessment of phase stability of high-viscosity oil by differential scanning calorimetry. The proposed calorimetric method is less laborious in comparison with existing methods for determining the group composition of oil and calculating the instability index based on SARA components. In general, the calorimetric method is more advanced method for assessing the oil phase stability and is of practical and scientific interest. Authors carried out studies of the physicochemical properties, kinetic parameters of the oxidation of oil with a viscosity in the range from 63 to 70035 mPa·s. A calorimetric method is proposed for estimating phase stability of oil with the value of the activation energy of oil oxidation in the high-temperature region.
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