Oil production in the Orenburg region is declining. It is required to define new perspective exploration directions for oil reserves supplying to support stable level of oil production. In the 70-80s. exploratory drilling within the boundaries of the old oil-producing region - the South Tatar arch (STA) was reoriented from the terrigenous Devonian (D2-D3f1) to the Upper Devonian (D3f3-fm) reefs with oil deposits in the Upper Famenian – Tournaisian carbonate complex.
However, well drilling did not confirm the majority of supposed prospects because of an ambiguity of 2D seismic data.
In recent years, the prospecting of oil fields controlled by Upper Devonian reefs has been a highly effective area of exploration, developed by subsidiaries of PJSC NK Rosneft. Reefs development was favored by Orenburgneft’s purposeful acquisition of licensed areas and 3D seismic survey on a mostly perspective areas, which were recommended by the Tyumen Oil Research Center LLC. To substantiate perspective areas the Tyumen Oil Research Center LLC applied their method for reefs prospecting by series of Upper Devonian paleogeographic maps construction. As a result several groups of the Upper Devonian isolated reefs have been revealed in the south and in the north of the Orenburg region.
In the south, over conjunction zone between the Rubezhin Trough and the Orenburg Swell high-output oil deposits were discovered in the Upper Frasnian reefs and put into development. In the north, within the South-Tatar Arch, the Upper Frasnian – Lower Famenian reefs control abovereef oil deposits in the Famenian, Tourneisifn and Lower Visean reservoirs. Based on the mass analysis of 2D seismic patterns performed at the Tyumen Oil Research Center LLC on profiles acquired in the South Tatar arch in 1978-2008, about 100 anomalies were additionally identified, similar to Upper Devonian isolated reef images. Perspective areas were recommended for licensing and 3D seismic surveys.
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