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Аннотация
The Paleozoic oil-generating rocks are penetrated throughout entire West Siberia, however, they have been studied in detail only in the southeast, where most of oil pools have been discovered in the erosion-tectonic salients of the Paleozoic basement, which is the zone of contact of the Paleozoic (mainly D, less commonly O and C1) and Mesozoic (J1-2) deposits (Verkhtarskoye, Gerasimovskoye, Ostaninskoye, Urmanskoye, Yagyl-Yakhskoye, Kalinovoye fields and oth.) The oil inflows have been obtained in two prospects (Maloichskaya, Elley-Igayskaya), and oil shows have been identified in the core from the Paleozoic deposits occurring 200-300 m beneath their top in the Lemok-1 well. Solution of the problem of oil genesis in the erosion-tectonic salients of the Paleozoic basement is directly related to estimating the petroleum potential of the Paleozoic deposits. The up-to-date analytical methods (gas/liquid chromatography and mass spectrometry) of organic geochemistry provided opportunity to study the fractions of saturated hydrocarbons of oils and bitumens at molecular level. Using the method of cluster analysis, the studied oils have been separated into three families. Based on comparative analysis of biomarker parameters (ratios of n-C27/n-C17 <0.4, Pr/Ph <2, C29/C27 steranes <1, 2(C19+C20)/Ci tricyclane index, where i=23, 24, 25, 26), < 0.5, tricyclane content > 25% of total terpanes), it has been established that family-I oils are genetically related to organic matter (OM) of the Paleozoic plankton-derived and bacterial oil-generating rocks buried in the sea basins with normal aeration of bottom waters. The family-III oils (ratios of n-C27/n-C17 >0.5, Pr/Ph >3.5, C29/C27 steranes >2.5, 2(C19+C20)/Ci tricyclane index where i=23, 24, 25, 26) > 1, tricyclane content < 20 % of total terpanes), are originated from the organic matter of oil source rocks derived from lacustrine-marshy and marshy environments of the Togurskaya, Tyumenskaya, Salatskaya, and Urmanskaya Formations. The family-II oil (ratios of n-C27/n-C17 = 0.4, Pr/Ph =1.1, C29/C27 steranes =1.8, 2(C19+C20)/Ci tricyclane index, where i=23, 24, 25, 26 = 0.4, tricyclane content < 20% of total terpanes) is polygenic and have formed by mixing of oils of two genotypes (mainly Paleozoic and Lower-Middle Jurassic) at the stage of accumulating in traps.
