Abstract
The paper deals with a sol-forming system for oil recovery enhancement (EOR system) used to increase the rate of heavy oil displacement. The effect of sol-forming EOR system during the heavy oil displacement on the composition and stability of oil sampled from the Usinskoye oil field of Russia is investigated. The composition of a crude oil also plays an important role in changing its stability. The work is aimed to investigate stability of heavy crude oil in regards to asphaltene precipitation. For asphaltene toluene/n-heptane solutions, the aggregation stability of asphaltenes based on сhange in the optical density with time is investigated via spectrophotometry. SARA analysis is used to characterize the compositions of heavy oils. First, the content of asphaltenes precipitated from the oil samples is determined and then the samples of deasphalted crude oil (maltenes) are analyzed by the method of liquid adsorption chromatography for the purpose to study the composition of oil sampled from the wells before and after their treatment with the sol-forming EOR system. It is found out that the treatment of reservoir crude oil with the sol-forming EOR system results in changes in composition of saturated, aromatic hydrocarbons, resins, and asphaltenes (SARA components) and aggregative stability of produced oil. The results obtained showed that the aggregative stability of heavy oil depends not only on the content of SARA components in the dispersion medium but on the presence of metalloporphyrins in the oil. Metalloporphyrins could act as inhibitors of asphaltene precipitation, which is an additional factor responsible for the stabilization of the oil dispersed system
Highlights
The oil composition changes during production, transportation, and processing of crude oils [1, 2]
In [6, 15] was shown that the one of the main factors affecting the colloidal stability of crude oil is the high content of aromatic hydrocarbons and resins
The resistance of oils to asphaltene precipitation depends on the resin content and the steric position of resins relative to asphaltenes
Summary
The oil composition changes during production, transportation, and processing of crude oils [1, 2]. A literature review suggests that much attention is devoted to the study of the stability of oil dispersed systems, since it plays an important role in the processes of extraction, transport, processing, storage and use of hydrocarbon raw materials [4, 5]. A decrease in the stability of the oil dispersed system during the development of the oil field and the extraction of oil is accompanied by the deposition of asphaltene-resin-paraffin deposits, which result in the colmatation of rocks and contamination of downhole equipment. They hamper the technological processes of transportation of hydrocarbon raw materials. To prevent the deposition of asphaltenes, additives of aromatic hydrocarbons, deasphaltisate, resins and special inhibitory substances can be used
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