Influence of Supercritical Water on the Composition and Distribution of Microelements in Resins, Asphaltenes, Kerogens, and Rocks of Tatarstan Domanik Deposits of Different Lithological Types

Abstract

Abstract A comparative study of changes in the microelemental composition and distribution in resins, asphaltenes, and kerogens from Tatarstan Domanik rocks, occurring under the action of supercritical water (SCW) at 374°С and a pressure of 22–24 MPa, was made. The samples studied belong to different lithological types; they were taken from carbonate–siliceous deposits of the Romashkino and Tavel oilfields and from carbonate deposits of the Bavly oilfield. The specific features of distribution of different microelements (MEs) in rocks and rock organic matter (OM) components were revealed by inductively coupled plasma mass spectrometry (ICP-MS). The major MEs are Fe > Ti > Ni > Zn > V > Cr > Cu with the concentrations from 100 to 8600 ppm. The total ME content of rocks from these deposits is 1.14, 0.23, and 0.38%, respectively. The ME content of resins and asphaltenes does not exceed 0.3 and 2%, respectively. The highest ME content, 8%, is observed in kerogens. The carbonate–siliceous rocks from different deposits with Сorg 7.07 and 1.90% differ from the carbonate rock with low Сorg (0.33%) in that the ME concentration in them is maximal. On the other hand, the ME content of resins and asphaltenes from the carbonate rocks is higher compared to the carbonate–siliceous rock samples. The concentrations of Fe, Cu, As, Se, Pb, and Bi in kerogens of all the types decrease under the action of SCW. In the transformed resins and asphaltenes from carbonate–siliceous rocks, the V and Ni concentrations appreciably decrease, whereas in kerogens their concentrations do not change noticeably. The demetalation processes lead to the ME redistribution between the OM components and mineral surface of the rocks.