Transformation of the Organic Matter of Low-Permeability Domanik Rock in Supercritical Water and 1-Propanol (A Review)

The effect of 1-propanol on the transformation of the organic matter (OM) of the domanik rock of the Romashkino field with the С оrg content of 7.26% in supercritical water (SCW) at 374°С was studied. The OM undergoes essential changes in the course of these experiments. According to the Rock-Eval data, addition of 1-propanol to the SCW reaction medium increases the rock production index (PI) by a factor of almost 2, from 0.48 to 0.76, owing to high degree of degradation of the insoluble kerogen, from 22.17 to 0.30 mg g –1 rock (parameter S 2 ). A part of kerogen degradation fragments transforms into resins and aromatic compounds whose content in the extract increases by a factor of more than 2, whereas the content of saturated hydrocarbons (HCs) considerably decreases. As compared to the experiment in straight SCW, insoluble high-carbon substances of carbene/carboid type are absent. The gas phase contains 78.8 rel % СО 2 , which favors the recovery of high-molecular-mass oil components from the low-permeability domanik rock. The formation of HC gases is indicative of the occurrence of intense degradation processes involving homolytic cleavage of C–C bonds by the radical-chain mechanism. The content of high-molecular-mass n -alkanes C 17 –C 27 , phenanthrenes, and dibenzothiophenes in the transformed shale oil increases. The structure of aromatic HCs, resins, and asphaltenes after treatment in SCW with the addition of 1-propanol becomes more condensed, and the content of aliphatic fragments and sulfoxide S=O groups decreases, suggesting the occurrence of dehydrogenation with the elimination of long alkyl chains via cleavage of heteroatomic bonds. In the process, 1-propanol not only acts as a cosolvent but also prevents the recombination of radicals formed in the course of kerogen degradation, which is confirmed by a decrease in the concentration of free radicals in resins and asphaltenes. The structurization of resins and asphaltenes leads to the removal of metals from porphyrin molecules and to a decrease in the paramagnetic properties. After the treatment both with SCW and with SCW + 1-propanol, the resins are characterized by superhyperfine splitting of the line of the vanadyl complex, caused by interaction with the 14 N nuclei, which suggests transformations of alkylporphyrins into monocycloalkylporphyrins via dealkylation, demetalation, and hydrogenation. After the autoclave experiments, the structure of mica in the mineral matter of the domanike rock undergoes changes due to segregation of the separate montmorillonite phase.