Conversion of High-Carbon Domanic Shale in Sub- and Supercritical Waters

Abstract

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.

Heavy Oil Hydrocarbons and Kerogen Destruction of Carbonate–Siliceous Domanic Shale Rock in Sub- and Supercritical Water

“…In contrast to the initial extract, the content of aromatic hydrocarbons and asphaltenes after the treatment at sub-CW condition was increased, while the atomic H/C org ratio decreased. In the previous studies [31,32], an influence of sub-CW on improving extraction of asphaltenes and high-molecular n-alkanes C 22 -C 30 from rock samples was shown. However, SCW effects decomposition of resins and asphaltenes with formation of low-molecular saturated hydrocarbons (33.91%wt.…”

“…The object of the study was the Domanic rock, which was taken from 1720 m depth of the Semiluki-Mendym horizon of the Chishminskaya area, which is located on the largest Romashkino field territory (Tatarstan, Russia). The given rocks are characterized by the following mineral composition: 43% quartz, 19% calcite, 19% microcline, 12% mica, and 6% dolomite [31]. According to the data obtained by using the Rock-Eval pyrolysis method, the total organic content (C org ) in the rock sample is 7.07%.…”

Sub- and supercritical water in the processes of conversion of Domanik rock organic matter

“…A sample of Domanik rock taken from a depth of 1,720 m of the Semilukian-Mendymian horizon is characterized by the following mineral composition: 43% quartz, 19% calcite, 19% microcline, 12% mica, and 6% dolomite [20]. According to the Rock-Eval pyrolytic method, the content of organic carbon (C org ) in the rock is 7.07%.…”

Composition of Oil after Hydrothermal Treatment of Cabonate-Siliceous and Carbonate Domanic Shale Rocks

“…Berezovskaya area (а) (b) It is important to note the presence of alkyl-trimethylbenzenes (m/z 133 + 134) or arylisoprenoids-aromatic compounds characterized by the presence of long alkyl chains of isoprenoid structure in saturated fractions of the studied oils [20]. Due to the presence of long alkyl substitutes in aromatic benzene rings, aryl isoprenoids may concentrate both in saturates and aromatic fractions during SARA analysis.…”

“…Thus, the thermal methods, which are applied for the development of Domanic deposits, provide catagenic transformation of organic matters in a certain degree [8]. Besides the in situ combustion, hydrofracturing and acidizing techniques, one of the promising ways of producing light hydrocarbons from kerogen is its transformation in aquatic medium in high-temperature or supercritical conditions [18][19][20]. Superheated water as well as supercritical water improve the transportation characteristics of heavy oil by increasing its solubility and decreasing its viscosity.…”