The effect of supercritical water on conversion of resins, asphaltenes and kerogens in rocks of different lithofacies of Domanic deposits of Tatarstan

In this paper the effect of supercritical water (SCW) at 374 degrees C and 22.4-24.6 MPa on the conversion of resins, asphaltenes, and kerogens in rocks of different lithofacies of Domanic deposits of Romashkino, Tavely and Bavly oilfields of Tatarstan was discussed. A feature of the rocks is the different content of organic carbon (7.07, 1.90 and 0.33 %, respectively), the high content of resins and asphaltenes (over 60 % in total) and the presence of type II kerogen with a high oil generation potential. The SCW treatment of the rocks leads to the decomposition of kerogens and the destruction of resins and asphaltenes with the formation of petroleum hydrocarbons. The conversion of resins, asphaltenes, and kerogens is accompanied by the alkyl substituents detachment, which leads to a decrease in the length and degree of aliphatic fragments branching and an increase in the aromatic carbon content. The oxygen-containing groups decrease in kerogens and asphaltenes and increase in resins, indicating the occurrence of degradation and oxidation processes. Destructive processes lead to an increase in the degree of catagenic maturation of kerogens, which is accompanied by partial desulfurization and demetalization of their structure, as well as of asphaltenes and resins. In kerogens, asphaltenes and resins of carbonate-siliceous rocks of the Romashkino and Tavely oilfields the concentration of biogenic microelements (ME) decreases with their subsequent adsorption on the mineral surface of the rocks, in this case, the content of radioactive ME noticeably increases, especially in resins. Under similar conditions of SCW exposure on carbonate rock of the Bavly oilfield as well as high-carbon rocks in kerogen, the concentration of biogenic ME decreases and the concentration of radioactive ME increases, but unlike them, the concentrations of biogenic, radioactive and rareearth ME increase in asphaltenes and resins, with a decrease in their content in rocks. The identified distinctive features of the conversion of resins, asphaltenes and kerogens of Domanic rocks of different lithofacies, which affect the quality of oil extracted from these rocks, must be taken into account when developing deposits using SCW technologies.

Automated summary

This paper discusses the effect of supercritical water on the conversion of resins, asphaltenes, and kerogens in rocks from different oilfields. The treatment leads to the decomposition of kerogens and the destruction of resins and asphaltenes, forming petroleum hydrocarbons. The conversion process involves detachment of alkyl substituents and changes in carbon chain structure.