The Domanic pay zones can be compared with the shale plays in the USA. In the geologic section of the Volga-Ural oil-and-gas basin, they occur from the Sargaevskian through the Zavolzhskian age. The Domanic sediments are represented by siliceous-argillaceous-carbonate varieties enriched with organic matter and other dissipated oil components. These sediments with rather low-quality reservoir properties are the main source rock.
The Domanic sediments on the territory of the Republic of Tatarstan and the adjoining territories of the Volga-Ural oil-and-gas province were proved to be oil-bearing.
To-date (as of January 1, 2017), eight fields with pay zones confined to the Domanic sediments have been booked in the State Reserves Register of the Republic of Tatarstan. All these fields are found within the South-Tatarian Arch. Oil accumulations were found in the Domanic sediments of the Sargaevskian, Eletskian, Dankovo-Lebedyanskian, and Zavolzhskian formations.
Tatneft PJSC has been carrying out Domanic exploration projects in its license areas in the Republic of Tatarstan, Samara and Orenburg regions, the Nenets Autonomous Area, and the Republic of Kalmykia.
In Samara and Orenburg regions, oil accumulations in the Zavolzhskian and Dankovo-Lebedyanskian formations were found, also, core analyses revealed slight oil shows in the Dankovo-Lebedyanskian, Eletskian, Zadonskian, Evlanovskian-Livenskian, Voronezhskian, Mendymskian, Semilukskian, and Sargaevskian formations. However, conventional flow tests in the intervals of the Dankovo-Lebedyanskian, Eletskian Evlanovskian-Livenskian, and Voronezhskian formations produced water. Obviously, non-conventional novel approaches are needed to drill and test Domanic sediments, which can be rather costly.
High exploration potential is associated with the Republic of Udmurtia. At present, six fields with pay zones confined to the Domanic sediments in the Frasnian, Famennian, and Zavolzhskian formations have been booked in the State Reserves Register of the Republic of Udmurtia; besides, oil accumulations not yet booked have been found in the Zavolzhskian formations. In Udmurtia, conventional exploration methods were applied implying search for oil in the Domanic plays based on presence of bioherm buildups. However, our experience shows that the Domanic sediments are characterized by areal extent and are not controlled by structural factors. It should also be borne in mind that the Domanic pay zones are classified as nonconventional tight reservoirs with rather high TOC. Available data is not yet sufficient to assess hydrocarbon potential in the Republic of Udmurtia, however, consistent and detailed study of Domanic plays might make them a promising production target.
Generally, hydrocarbon potential of the Domanic sediments is rather high, and the territory of the Volga-Ural oil-and-gas province may serve as a unique testing site to study Domanic plays and to test novel production methods that are able to provide return on investments.
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