Abstract
Tectonical and development features of the central part of the Volga-Ural anteclise and the Sura-Kama (SK) shear zone are considered in connection with the distribution patterns of oil fields. Based on the geological and structural data, it is found that the SK zone is a deep fault of a heterogeneous structure, which has signs of the long-term multistage development. At the plate stage, the SK zone developed under kinematic inversion and subsequent transpression and transtension deformations. We propose a model showing that during the transtension stages, deformations in the SK zone contributed to the primary migration of hydrocarbons in the Devonian domanic formations and their secondary redistribution. Within the SK zone, permeability was increased, and the zone itself acted as a concentrator of these formations in local decompression structures. Fault structures in the SK zone closed during the transpression stages; their reservoir properties were decreased; and hydrocarbons were squeezed predominantly in the lateral direction along the reservoirs in the area of dynamic unloading. At the eastern termination of the SK zone, the unique Arlan oil field was formed, wherein hydrocarbons were accumulated in conditions of alternating stresses between the sectors compensating shear displacements at the flanks of the zone. The unique Romashkinsky oil field was formed in the apical part of the South Tatar arch during its long-term uplifting and decompression, which contributed to progressive migration and accumulation of hydrocarbons from the transpression sector of SK zone. The proposed structural-dynamic model and ideas about compression – decompression regularities of hydrocarbon redistribution in the shear zones can be used for prediction and detection of new deposits. In particular, the dynamic analogues of the Arlan oil field in the east part of the SK zone can be found within the poorly studied western flank of this zone.
Highlights
We propose a model showing that during the transtension stages, deformations in the SK zone contributed to the primary migration of hydrocarbons in the Devonian domanic formations and their secondary redistribution
Deep structure and oil and gas potential of the Volga-Ural region and adjacent territories
Summary
Факторы формирования месторождений нефти и газа принято рассматривать в едином ряду последова тельных процессов, связанных с генерацией, эмиграцией и миграцией, аккумуляцией и разрушением залежей углеводородов (УВ) [Bazhenova et al, 2004; Bakirov et al, 1982]. Вторичная вертикальная миграция УВ происходит при отсутствии экра- нирующих горизонтов или вдоль зон тектонических нарушений. Региональ ная миграция УВ проявляется при взаимодействии раз личных факторов, но особо важную роль в данном случае приобретают тектонические процессы. Что геодинамиче ские процессы, в том числе новейшие, оказывают не посредственное влияние на флюидодинамику и игра ют важнейшую роль при формировании и разрушении залежей нефти и газа [Bakirov et al, 1982; Burster, Bizya ev, 1969; Korzhov et al, 2011; Kazantsev, Kazantseva, 2008; Lastochkin, 1974; Mingazov et al, 2012; Morozov et al, 2012; Sidorov et al, 1989; Sitdikova, Izotov, 1999; Gavrilov, 2017]. Предполагается, что тектонические процессы, связанные с формированием этих зон, играли важную роль при пер ераспределении УВ в пределах самих нарушений и в областях их динамического влияния. При обработке кинематических данных использовалась про грамма FaultKin6 [Marrett, Allmendinger, 1990]
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