Influence of thermal and chemical enhanced oil recovery methods on geochemical properties of residual bitumoid in a bituminous sandstone model

UDK: 622.276.6:552.578.2.061

DOI: 10.24887/0028-2448-2026-7-33-37

Key words: super-viscous oil, fractional composition, bituminous sandstone, SARA-analysis, gas chromatography-mass spectrometry, steam treatment, СО2, aquathermolysis catalyst

Authors: V.D. Storozhenko (TatNIPIneft, RF, Almetyevsk); V.N. Lebedev (TatNIPIneft, RF, Almetyevsk); I.F. Gareev (Almetyevsk State Technological University «Petroleum Higher School», RF, Almetyevsk); D.I. Ganiev (Almetyevsk State Technological University «Petroleum Higher School», RF, Almetyevsk); А.N. Мingazutdinov (TatNIPIneft, RF, Almetyevsk); R.М. Khabipov (TATNEFT PJSC, RF, Almetyevsk); М.I. Аmerkhanov (TATNEFT PJSC, RF, Almetyevsk)

Super-viscous oil and natural bitumen of the Permian formations in the Republic of Tatarstan represent a strategic resource of the Russian oil industry. However, their development is impossible without thermal and chemical enhanced oil recovery (EOR) methods. Typically, performance of EOR methods is assessed by displacement efficiency and dynamic viscosity of the produced fluid, but geochemical properties of the residual oil are studied rarely. The paper presents the results of a comparative study of residual bitumoid in the bituminous sandstone core samples after a set of 13 flow tests using a linear reservoir model, including treatment by saturated and superheated steam, steam in combination with hydrocarbon solvent, carbon dioxide under subcritical conditions, and an aquathermolysis catalyst. Bitumoid was extracted from core samples using organic solvents, and its geochemical properties were determined by SARA-analysis and gas chromatography-mass spectrometry. The majority of the considered EOR methods yielded a similar reduction in the bitumoid content of the rock, whereas some differences in the alteration of fractional composition were observed. For example, steam treatment results in a shift of the n-alkane series toward high-molecular-weight components, while its combination with the solvent enhances the resin-asphaltene fraction recovery efficiency. Under subcritical conditions, CO2 effectively interacts with cyclic and heteroatomic compounds. Catalytic aquathermolysis demonstrated the best performance and was additionally accompanied by degradation of asphaltenes. The obtained results showed notable differences in the mechanisms of EOR-bitumoid interaction, thus serving as a basis for the optimal selection of EOR technologies considering the initial fluid geochemical properties.

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