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The presence of paramagnetic species such as vanadyl complexes (VO2+) and free carbon radicals in petroleum disperse systems (PDSs) such as crude oil, bitumen, or kerogen causes significant interest of studying the structure of PDS, high-molecular weight components, and their effects on the physical and chemical properties of PDS products by magnetic resonance techniques. However, the lack of detailed studies keeps the exact structure, aggregation mechanism, and interaction with complex composites of the PDS still disputable. In this contribution, detailed electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) investigations, including advanced fast field cycling dynamic nuclear polarization, of heavy crude oil focused on vanadyl complexes are presented. A perceptible room-temperature 1H dynamic nuclear polarization (DNP) solid effect at the X-band (magnetic field of 300–400 mT corresponding to the EPR frequency of 9.5 GHz and NMR frequency of 14.6 MHz), with enhancement ±5, is observed at moderate microwave irradiation power in crude oil with a high concentration of VO2+, while no Overhauser DNP contribution is found. Using NMR T 2-encoding, DNP spectra and molecular dynamics, two components are distinguished, from which the one with slower dynamics exhibits higher DNP enhancement via VO2+ complexes. The observed difference is discussed in terms of electron–nuclear interaction and relative parts of hyperpolarized nuclear spins using an advanced model for DNP data simulation.

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The model experiments regarding the conversion of organic matters from carbonate rock samples of Dankov-Lebedyan deposits of Zelenogorskaya area and siliceous-carbonate rocks of Semiluki-Mendym deposits of Berezovskaya area of Domanic formations of Romashkino oil field were carried out. Two types of experiments were carried out: (1) the hydrothermal treatment of rocks at a temperature of 350°C in the presence of carbonic acid and a water content of 30%; (2) pyrolysis at temperatures of 350 and 600°C in the presence of hydrogen. The yield and quality of extracted hydrocarbons from the rocks depending on the mineral composition of rocks, content and composition of organic matter, and thermal stability of kerogen under hydrothermal influences were evaluated. Application of electron paramagnetic resonance in pyrolysis processes revealed the difference in mineral content of rocks (Mn2+, SO3−, and SO2− ions) and free radicals R∗, as well as in vanadyl ion (VO2+) concentration. It is established that an increasing temperature of pyrolysis promotes the formation of new free organic radicals in rock samples: in Domanic rocks of Semiluki-Mendym deposits at 350°С and in carbonate rocks of Dankov-Lebedyan horizon at 600°С. This indicates different ability of oil-generating potential of rocks with hydrothermal and pyrolysis technologies.

This paper presents the results of the conversion of high-carbon Domanic rock from sediments of the Semiluki-Mendym horizon of the Volga-Ural petroleum Basin in sub-and supercritical waters at temperatures of 320, 374, and 420 °C in a neutral nitrogen environment for 1 h. The initial sample is a siliceous-clay carbonate rock with an organic matter content of 10.6 wt %, the largest part of which is insoluble kerogen. The end products of all experiments are characterized by an increase in the content of saturated hydrocarbons with a noticeable decrease in the content of resins and asphaltenes. The highest yield of the extract (3.98 against 3.12 wt %) compared with the initial rock is observed in the experiment in subcritical water at 320 °C as a result of the preferred degradation of resins and more complete extraction of asphaltenes from the rock. With an increase in temperature to supercritical water conditions at 374 °C and pressure up to 24.6 MPa, kerogen transformation processes are observed due to the C−C, C−N, and C−O bonds destruction with the formation of low-boiling saturated hydrocarbons and high-carbon components such as carbene−carboids in the products of the experiments. The highest yield of saturated hydrocarbons occurs at the experiment of Domanic rock in supercritical water at 420 °C and 24.4 MPa. Under these conditions, in comparison with lower temperatures, the yield of the extract from the rock decreases due to intense gas formation. In the composition of the gases formed in the experiments, there are hydrocarbons: CH 4 , C 2 H 6 , C 3 H 8 , and i-C 4 H 10 , indicating the destruction of C−C bonds. Dehydrogenation processes in supercritical water at 420 °C are noted by the presence of H 2 in the reaction system. Structural and phase changes in the mineral composition of Domanic rock were discovered as a result of supercritical water exposure at 374 and 420 °C. In particular, the structure of mica was changed due to the isolation of a separate phase of montmorillonite from it.

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