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Abstract

UDC (552.578.2.061.3:551.24):551.72(571.5)

EVOLUTION OF OIL AND GAS ACCUMULATION ZONES IN THE NEPA-BOTUOBA ANTECLISE DURING THE PHANEROZOIC

A. V. Migursky, P. N. Sobolev

Since the sedimentary cover of the Nepa-Botuoba anteclise began to deposit, the anteclise underwent several structural alterations that were crucial for naphtide genesis. During the Riphean and Early Vendian, the contrast Patom-Vilyuy and Irkineeva-Chadobets depressions were formed at the Nepa-Botuoba anteclise margins, where many kilometres thick sedimentary strata were accumulated with the formation of primary oil and gas accumulation zones therein. In the Late Vendian and Early Paleozoic, the territory under study was drastically but stably downwarped, which was accompanied by accumulation of more than 2.5 km of sediments prevailed by salt beds, which were sustainable seal for hydrocarbons. The adjoining oil and gas accumulation zones extended to the marginal parts of the Nepa-Botuoba anteclise. The formation of the Fore-Patom fold and thrust belt at the turn of the Silurian and Devonian caused drastic changes in the structure of the Patom-Vilyuy oil and gas accumulation zone by destroying major paleoaccumulations of oil and gas in its central part. A portion of hydrocarbons was displaced toward the Nepa-Botuoba anteclise to its Middle Paleozoic axis, with formation of oil and gas accumulation zones in the autochthon and allochthon. The Early Hercynian tectogenesis resulted in fracturing of the eastern periphery of the anteclise into small blocks accompanied by the formation of numerous hydrocarbon traps. The Late Hercynian structural alteration resulted in the completion of the Nepa-Botuoba anteclise structure, eastward displacement of its axis (up to 200 km), and formation of the major near-axis oil and gas accumulation zone.

Key words: Riphean-Phanerozoic geodynamic activation, structural alteration, naphtide genesis, oil and gas content.

DOI 10.20403/2078-0575-2016-2-27-40

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