Hydrothermal transformation of kerogen and oil in Low-permeability rocks of the domanic deposits in carbon dioxide media

Using a rock sample as an example Mendym deposits Upper Devonian of the Tavel oil field (Tatarstan) a study was conducted to determine whether temperature influences the nature of organic matter transformation into low-permeable rock. The initial rock is characterized by its mineral composition as carbonate-siliceous with the OM content is 4.6 wt%, more than 70% of which is kerogen and high-molecular bituminous components. Experiments were conducted at 250 °C, 300 °C, and 350 °C in a carbon dioxide environment with a 1:1 water to rock ratio and an exposure time of 24 h. The degree of kerogen conversion in the rock was determined, changes in the composition of the formed gases, group and hydrocarbon composition were assessed extracts. The most complete conversion of solid organic matter into extractable liquid and gaseous products is observed at 350 °C, as evidenced by the Rock-Eval results, namely a decrease in the S2 indicator from 5.06 mg/g in the original rock after extraction to 0.63 mg/g in the rock after the experiment at 350 C and extraction, the greatest decrease in the TOC indicator to 0.29% of sample mass, as well as a decrease in HI to 218 mg HC/g Corg. An increase in the extract yield with an increase in the exposure temperature from 1.05 wt% in the initial rock by 63% in the rock after the maximum experimental temperature of 350 °C was established, in accordance with which the content of saturated hydrocarbons increased from 14.5 to 35.3 wt%. According to the molecular weight distribution of aromatic hydrocarbons, it was established that polycondensation structures in the composition of kerogen are predominantly transformed into di-, tri- and heterocyclic sulfur-containing aromatic fragments.