Microelemental Composition of Petroleum Extracts and Asphaltenes from Rocks of High-Carbon Domanik Sediments of Tatarstan

A comparative study of the microelemental composition of extracts and asphaltenes from high-carbon carbonate–silica rocks of Domanik sediments of the Romashkino, Pervomaiskii, and Muslyumovo fields located in the central part, north, and east of Tatarstan was made. The rock samples studied differ from each other in the mineral composition and in the content and composition of the organic matter (OM). The composition and distribution of biogenic, rare earth, and radioactive microelements (MEs) in the extracts, asphaltenes, and carbene–carboids were studied by inductively coupled plasma mass spectrometry. With respect to the ME concentration, all the samples can be subdivided into two groups. The first group with high content of all ME groups includes samples from the Muslyumovo field and from the Sarmanovo and Berezovskaya areas of the Romashkino field, and the second group includes samples from the Pervomaiskii field and from the Chishma area of the Romashkino field. Similar subdivision of the samples into two groups is observed with respect to the content of kerogen and hydrocarbons in rocks, to the yield of extracts, and to the content of carbene–carboids in the extracts. Strong correlations were revealed between the concentration of biogenic MEs in the extracts and asphaltene content of the extracts ( R 2 = 0.70) and between the content of rare earth and radioactive MEs, on the one hand, and resin content of the extracts and calcite content of the rocks, on the other hand ( R 2 = 0.73). No correlation with the OM content was revealed. The extracts and asphaltenes significantly differ in the ME distribution. The Domanik rocks from the examined fields differ in the ME content, which may be due to different sources of the ME supply into these formations, including supply with fluids flowing up from the depth.