Effect of oil potential and deep tectonics on the trace element composition of soils: An example of the Tatarstan Republic

Published seismic data were considered in combination with the results of lithogeochemical and electrochemical data on soils above oil reservoirs and subvertical dynamic anomalies at the territory of Tatarstan. The effect of oil potential and deep-seated tectonics on the trace element composition of soils was exemplified along several seismic profiles across the Southern Tatar and Northern Tatar arches. Elevated contents of Li, B, Al, and As were recorded above dynamic anomalies, while oil accumulations are marked by high contents of V, Ni, Cu, Mo, and Ag.     

Prediction of the phase state of hydrocarbon accumulations in the Mesozoic deposits of northwestern Siberia

The phase state of hydrocarbon accumulations was predicted using recent drilling data for three oil and gas complexes of the northern regions of the West Siberian petroliferous basin: Lower and Middle Jurassic, Upper Jurassic, and Berriasian-lower Valanginian (Achimov member); these results were compiled in simplified maps presented in the paper. In order to develop a plausible model and distinguish the zones of hydrocarbon accumulation of various phase states, we analyzed and systematized the existing concepts on the distribution of oil, oil-gas condensate, and gas condensate pools in the Mesozoic sequences of this region, types of organic matter in rocks, and stages of catagenetic alterations. Based on the data of the Tyumen SG-6 superdeep well, the oil-generating capacity of source deposits was assessed. Three zones differing in the phase state of hydrocarbons, oil, gas condensate-oil (transitional), and gas condensate, were distinguished in the map of the distribution of hydrocarbon accumulations in the Early-Middle Jurassic petroliferous complex of northwestern Siberia. Only two zones of hydrocarbon accumulations, oil and transitional, were detected in the Late Jurassic complex of the Nadym-Taz and Ust’-Yenisei regions. The same zones but within different boundaries were distinguished in the Achimov sequence. In contrast to the Jurassic beds, the zone of occurrence of oil accumulations in the Achimov member occupies a larger area and extends further north. In terms of density, the oils of the Achimov deposits were subdivided into three types: ultralight, light, and medium. The zones of their occurrence are shown in the map. Original Russian Text ? S.A. Punanova, T.L. Vinogradova, 2006, published in Geokhimiya, 2006, No. 9, pp. 983–995.