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.
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