Comprehensive аnalysis of вitumen composition alterations after thermal recovery processes

This paper presents the results of a comprehensive study of changes in the composition of residual bituminoids in core samples following various thermal treatment regimes. Oil-saturated core samples subjected to hot water, steam, superheated steam, and regimes with increased heat transfer fluid injection rates were used as test specimens. A suite of methods, including pyrolysis, SARA analysis and gas chromatography-mass spectrometry, was employed to assess changes in organic matter. It was established that all the exposure regimes studied lead to a reduction in the total hydrocarbon content of the core; however, the composition of the residual bituminoid varies depending on the initial properties of the oil. It has been shown that, for materials with a lighter and less transformed initial composition, the primary process is the selective removal of light and medium-molecular-weight components, resulting in the residual oil becoming heavier and enriched with resinous and asphaltene compounds. For samples with a higher-molecular-weight or biodegraded composition, the changes are significantly less pronounced, even under high-energy treatment conditions. A comprehensive interpretation of the results of pyrolysis, SARA analysis and gas chromatography-mass spectrometry has shown that identical thermal treatment regimes can lead to the formation of fundamentally different compositions of the residual bituminoid. The results obtained indicate the need to take into account the initial molecular-group composition of the oil when selecting thermal treatment regimes and predicting the properties of residual oil following thermal treatment of the reservoir.

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