In regions with high depletion of hydrocarbon reserves, where the main (conventional) exploration targets have been largely exploited, the importance of replenishing the hydrocarbon resource base and, consequently, of exploring non-anticlinal traps in potentially productive sedimentary deposits of brown oil and gas provinces increases. Based on the analysis of data obtained from geological exploration at three different sites of the Upper Devonian–Tournaisian paleoshelf in the Udmurt Republic, located within various elements of the paleoshelf (the relatively shallow paleoshelf of the Kama–Volga system, the barrier reef zone, and the paleoplateau of deep-water depressions of the Kama–Kinel’ system) and differing in the completeness of the Visean stratigraphic section, non-anticlinal structures were identified in the basal interval of the terrigenous lower Carboniferous sequence. These structures are associated with erosional-karst processes in the underlying Late Frasnian–Tournaisian carbonate deposits. The study determined differences in morphology, age (Radaevsky, Bobrikovsky) of erosional features, and predominant composition of host sediments (coal, claystone and siltstone, sandstone) typical of the identified areas. The diversity and lateral variability of the infilling deposits are favourable factors for the formation of shaleout traps. The materials presented in this study demonstrate that the development of incised features and their sedimentary infill occurred throughout the Early and Middle Visean, and the areas of formation of these objects and, consequently, the associated non-anticlinal traps moved gradually northward within the Udmurt Republic.

Natal’ya G. Istomina ORCiD 
Assistant professor
Institute of Oil and Gas named after M.S. Gutseriev, Udmurt State
University,
1/7, ul. Universitetskaya, Izhevsk, 426056, Russia
e-mail: Istomina.N.G@gmail.com
SPIN 7141-2906

Dmitrii N. Novokshonov  ORCiD 
Lead Engineer
Izhevsk branch of the All-Russian Scientific-Research Geological Oil
Institute (VNIGNI),
270, Pushkinskaya, Izhevsk, 426004, Russia
e-mail: novokshonov@vnigni.ru
SPIN 2887-6968

1. Ermolova T.E., Mushin I.A., Stupak A.A., Frolov B.K., Oksman G.A., Kholmyanskaya N.Yu. Opportunities for new oil and gas bearing objects prospecting in the Upper Tournaisian-Visean terrigenous formations of eastern part of Volga-Urals Petroleum Province on the basis of integrated sedimentological and geoseismic studies. Geologiya nefti i gaza. 2019;(3):67-85. DOI: 10.31087/0016-7894-2019-3-67-85.
2. Larochkina I.A., Ganiev R.R., Novikov I.P. Erosion-karst partial barrier influence on placing of deposits of oil in radaevsko-bobrikovsky adjournment. Georesursy [Georesources].2010;35(3):38–41.
3. Pavlova T.Yu., Korkin K.M., Purtova T.N. et al. Sovremennye predstavleniya o geologii i neftenosnosti Udmurtii [Modern ideas about the geology and oil content of Udmurtia]. Izhevsk: Rosgeolfond, 2002. pp. 83–88.
4. Savel’ev V.A. Neftegazonosnost’ i perspektivy osvoeniya resursov nefti Udmurtskoi Respubliki [Oil and gas potential and prospects of oil resources development in the Udmurt Republic]. Moskva-Izhevsk: Institut komp’yuternykh issledovanii, 2003. 287 p.
5. Furman N.F, Shpilevaya I.K., Oshchepkova L.V., Trofimova E.V. Erosive incisions effect on formation of oil pools by the example of the Central deposit. Neftyanoe khozyaistvo. 2004;(12):20–24.
6. Shpilevaya I.K., Trofimova E.V., Furman V.F., Istomin A.G. Some features of Visean incisions structure in Udmurtia. Geologiya nefti i gaza. 2001;(06):40–43.