Regional criteria have been defined on the basis of world exploration experience analysis to substantiate by reef controlled oil-bearing zones. Presence of deep-water paleobasin with carbonate sedimentation and favorable paleoecology for reef development are main criteria to begin exploration for rich reef hydrocarbon deposits. The postdepositional inversional regional slope is an important criterion to look for large hydrocarbon deposits are controlled by barrier reefs.
Application of the defined criteria to substantiate exploration development around the Orenburg region has resulted in confirmation of earlier forecasted new exploration play had to be controlled by the Upper Devonian reefs. 705 square kilometres of 3D seismic acquisition within the forecasted perspective zone were resulted in mapping of big groop of the Upper Frasnian isolated basinal reefs. Reef highs – 200-250 m, acreages – 0,7-1,7 km2. Due to drilling of successful exploration wells the rich oil-bearing zone has been revealed on reefs: oil deposits were discovered in reef bodies, in the Lower Famenian and Carboniferous layers in the above-reef compaction closures too.
As a result of the regional criteria application new exploration play of Lower Famenian barrier reef has been revealed. The last was first delineated around the south-east of Volga-Ural Province. Together with Zavolzhian barrier reef the Lower Famenian barrier reef formed the Bobrov-Pokrov Swell of the Mukhano-Erokhov Trough’s southern margin in the Orenburg Oblast. Postdepositional inversional regional slope of the trough’s margin has provided a creation of above-reef closures, which are controlled large oil-bearing zone in the Carboniferous, Mid-Famenian and Upper Famenian layers. Oil deposits in the Famenian were placed along the Lower Famenian barrier reef and are the present-day perspective exploration play.
References
1. Dentskevich I.A., Oshchepkov V.A., Regularities in the location of oil deposits in the side zones of the Mukhanovo-Erokhivsky trough (In Russ.), Geologiya nefti i gaza, 1989, no. 5, pp. 21–23.
2. Dentskevich I.A., Khomentovskaya O.A., Vozmozhnosti seysmofatsial'nogo analiza pri poiskakh lovushek nefti v karbonatnom razreze franko-turneyskogo kompleksa (Capabilities of seismic facies analysis in the search for oil traps in the carbonate section of the Franco-Tournaisian complex), Collected papers “Geologiya i razvedka mestorozhdeniy nefti i gaza yugo-vostoka Russkoy plity” (Geology and exploration of oil and gas deposits of the southeast of the Russian plate), Moscow: Publ. of VNIGNI, 1990, pp. 34–39.
3. Kuznetsov V.G., Geologiya rifov i ikh neftegazonosnost' (Geology of reefs and its oil and gas potential), Moscow: Nedra Publ., 1978, 304 p.
4. Mirchink M.F., Mkrtchyan O.M., Khat'yanov F.I. et al., Rify Uralo-Povolzh'ya, ikh rol' v razmeshchenii zalezhey nefti i gaza i metodika poiska (Reefs of the Ural-Volga region, its role in the location of oil and gas deposits and search methods), Moscow: Nedra Publ., 1974, 152 p.
5. Nikitin Yu.I., Ostapenko S.V., Shcheglov V.B., New branch of activities pertaining to geological prospecting in Orenburg region (In Russ.), Geologiya, geofizika i razrabotka neftyanykh i gazovykh mestorozhdeniy, 2011, no. 11, pp. 13–18.
6. Hriskevich M.E., Middle Devonian reef production, Rainbow area, Alberta, Canada, AAPG Bulletin, 1970, V. 52, no. 12, pp. 2260–2281.
7. Mesolella K.J., Robinson J.D., McCormick L.M., Ormiston A.R., Cyclic Deposition of silurian carbonates and evaporites in Michigan Basin, AAPG Bulletin, 1974, V. 58, no. 1, pp. 34–62.
8. Malek-Aslani M., Lower Wolfcampian reef in Kemnitz field, Lea County, New Mexico, Bulletin of Amer. Assoc. Petrol. Geol., 1970, V. 54, no. 12, pp. 2317–2335.
9. Sams R.H., Gulf Coast stratigraphic traps in the Lower Cretaceous carbonates, Oil and Gas Journal, 1982, V. 80, no. 8, pp. 177–182, 185–188.
10. Wright W.E., Abo reef: prime West Texas target: Part II, Oil and Gas Journal, 1962, V. 60, no. 32, pp. 187–194.
11. Hemphill C.R., Smith R.I., Szabo F., Geology of Beaverhill Lake Reefs, Swan Hills Area, Alberta, In: Geology of Giant Petroleum Fields: edited by Halbouty M.T., AAPG Memoir 14, Tulsa: American Association of Petroleum Geologists, 1970, pp. 50-90.
12. Neuman A.C., Macinture I., Reef response to see level rise: keep-up, catch-up or give-up, Proceedings of Fifth International Coral Reef Congress, Tahiti, 1985, pp. P. 105–110.
13. Nikitin Yu.I., Ostapenko S.V., Interrelationship between oil-bearing capacity of Volga-Uralian Province and plate tectonics of the Urals (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2008, no. 12, pp. 14–17.
14. Vilesov A.P., Boyarshinova M.G., Vinokurova E.E., Znachenie stromatolitov v formirovanii karkasa famenskikh rifov Volgo-Ural'skoy neftegazonosnoy provintsii (Role of stromatolites in Famenian reef framework formation of Volga-Ural oil-and-gas-bearing Province), Collected papers “Geologiya rifov” (Geology of reefs), Proceedings of Vserossiyskogo litologicheskogo soveshchaniya, Syktyvkar: Publ. of Institute of Geology of the Komi Science Center of the Ural Branch of the Russian Academy of Sciences, 2015, pp. 27–29.
15. Shakirov V.A., Nikitin Yu.I., Vilesov A.P. et al., A new direction of exploration of oil deposits on the Bobrovsko-Pokrovsky arch (Orenburg region) (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2016, no. 12, pp. 90–94.
