Petroleum potential of Orenburg segment of Urals frontal folds

The Urals frontal folds (West Urals fold zone) in the western part of the Orenburg Region are limited by the Syurensky oblique thrust. They conjugate with the Central Urals High through the West Ural Fault. These folds are studies by geological, gravity and magnetic, and regional seismic surveys (1526.3 km of seismic lines acquired). There is only one well drilled - Preduralsky-117. Two wells - Akberdinsky 53 and 63 - are drilled in the Bashkortostan territory in close vicinity to the boundary of the Orenburg Region. Devonian, Carboniferous, and Lower Permian carbonate-terrigenous deposits are folded here. There are three seismic stratigraphy sequences identified in the region. The lower (from the Basement surface to Devonian Bottom) is identified as an intermediate structural level. Riphean, Vendian, Ordovician, and Silurian deposits composing this level compensate the roughly NS trending trough in the Basement Top. It is expected that they are mainly represented by terrigenous deposits, although carbonate and terrigenous-carbonate series are possible here. Two plays are identified within the sedimentary structural level, they are: Lower Devonian-Frasnian (D1-D3f) and Upper Devonian-Lower Permian (D3-P1). The Zilairsky group Bottom (D3f2-fm) is a boundary between them. Both sequences are composed of carbonate-terrigenous deposits corresponding to the medium and Upper seismic stratigraphy sequences; they are considered to be the unconventional oil and reservoirs. There are five local oil and gas promising objects represented by anticline folds are found in the Orenburg segment of the Urals frontal folds. According to High Case, total gas resources in D1 Category make 395.8 BCM, oil in D1 Category - 668.7/100.3 mln tons (initial in-place/recoverable). According to Low Case, the resources make 62,5 % of the High-Case estimate. New focus area of oil and gas exploration is substantiated - Devonian-Early Permian carbonate-terrigenous deposits of the Urals frontal folds. And the priority for further development is drilling of 5400 m deep Novouralsky-1 structural well