Hydrocarbons genesis of pre-Jurassic complex in Khanty-Mansiysk field (the zone of West Siberian plate local compression)

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This paper establishes the origin of hydrocarbons deposits in Jurassic and pre-Jurassic complexes in the territory of Khanty-Mansyisk field, which is associated with traps formed in the weathered Devonian carbonate sediments and in basement rocks, within the zone of compression (suture?) in the central part of the West Siberian platform. The study is relevant for substantiating oil deposits prospecting strategy considering material composition and basement tectonics of West Siberian plate.Data on core and oil from Jurassic and pre-Jurassic complexes, exposed by exploration and production wells of Khanty-Mansyisk field, which is related to Frolovsk petroleum region of the highest density of predicted resources within the Western Siberian province, is studied. Lithologic and petrophysical characteristics of rocks carried out by optical microscopy, is provided. Content and molecular weight distribution of aromatics including n-alkyl benzenes, naphthalenes and phenanthrenes are established in rock bitumoids and crude oil by chromatography-mass spectrometry.Geochemical model of hydrocarbon migration within Jurassic and pre-Jurassic oil and gas complexes is developed. The most probable hydrocarbon source in the Upper Jurassic section traditionally is organic matter containing in clay stones and siltstones of tutleymsk (bazhenov), abalaksk and, presumably, tyumen formations. A layer of coarse grained highly permeable sandstone of gorelaya formation, which comprises organic matter, probably, of major contribution to the Lower Jurassic and pre-Jurassic hydrocarbon deposits, is recorded in section of the Lower Jurassic. The unified genesis of hydrocarbons among gorelaya formation and the Paleozoic oil from Khanty-Mansyisk field is determined through molecular markers — n-alkyl benzenes С21, С23, С25. Hydrocarbon collection from dispersed organic matter of Paleozoic rocks at the great depth (not exposed by core drilling) is suggested as a probable «source» of Paleozoic oil. Oil accumulation, presumably, is concentrated in areas of tectonic block crushing of basement, oil carryover into overlying complexes is performed with thermal waters. Prediction of oil potential in traps of weathering crust and basement rocks within the compression zones of West Siberian platform is positive.