New study reveals potential of Domanik formation in Russia's Volga-Ural basin

A joint research by KFU and Saudi Arabian (King Saud University) and Malaysian (University of Malaya) scientists saw light in Journal of Petroleum Science and Engineering.

As demonstrated by recent studies by the Laboratory of Enhanced Oil Recovery, most of the studied Domanic carbonate samples with depths ranging from 1726.5 meters to 1784.9 meters have now reached only low stages of thermal maturity.

This suggests that hydrocarbons can be extracted from this type of rock using special extraction methods and technologies, including hydraulic fracturing, thermal extraction methods, etc. In order to assess the generative potential of unconventional tight oil reservoirs, the scientific team considered several aspects such as lithology, mineralogy, brittleness, physical properties and characteristics of oil parent rocks, as well as the composition and properties of organic matter.

"To date, there is still a lack of scientific knowledge of oil-bearing rocks and reservoir rocks of the Domanik formation. Previous studies do not allow us to objectively study the potential of these rocks as unconventional tight reservoirs. The results of our studies will allow us to fill this gap and utilize these rock types in further development using certain production methods," says Junior Research Associate Shadi A. Saeed.

Until recently, the Volga-Ural Basin, known as Russia's oldest oil producing region, was depleted literally to the last drop. The Kazanites attributed the recorded increase in reserves to the small accumulations of hydrocarbons that were discovered and brought into production. The organic-rich carbonate rocks of the Domanik formation are an important potential strategic target for exploration, development and production in the Volga-Ural Basin. The Domanik formation contains mainly siliceous carbonate rocks enriched with sapropelic organic matter, which determines the high generational potential of the sediments.

The scientists explained the possibility of generating light hydrocarbons by the fact that carbonates enriched with organics, containing mainly type II and type I kerogen, were deposited in oxygen-free conditions. This indicates that these sediments are probably oil-bearing rocks. In addition, according to petrographic studies, limestone and dolomitic limestone lithofacies have a large number of cavernous and fractured secondary pores formed as a result of tectonic and diagenetic events, which represent a favorable environment for organic matter incorporation.

"A total of 18 core samples were collected from different depths of the field. These samples were comprehensively analyzed using several advanced techniques, including volumetric geochemical methods coupled with a volumetric kinetic model, X-ray computed tomography, scanning electron microscopy and X-ray structural analysis, as well as petrographic studies," adds Shadi A. Saeed.

As for overseas colleagues, they carried out experiments and necessary analyses, processed the obtained results and interpreted them.

"We sent part of the samples to Malaysia in order to conduct a detailed study of core microphotographs. Our colleagues from Saudi Arabia, in turn, conducted a thorough study and prediction of the maturity of the organic material in the shale core. This will allow us to subsequently determine its maturity and develop volumetric kinetic modeling. The main part of the experiments, including sample preparation and study of the key indicators of hydrocarbon potential determination, was carried out in the laboratories and research centers of Kazan Federal University," shares Junior Research Associate Ameen A. Al-Muntaser.

The results of the study demonstrate that the carbonate-rich samples of the Domanik formation are characterized by high total organic matter content up to 13.31 % and contain mainly type II kerogen with a small proportion of type II/III kerogen, achieving very good to excellent oil generation potential. According to the results, the Domanik formation has a high potential for commercial oil production, which usually requires hydraulic fracturing followed by thermal methods such as in-situ burning. In this case, the status of the Domanik Formation is confirmed not only as a reservoir rock, but also as an oil-bearing rock that is capable of independently generating hydrocarbons.

More information:
Geochemical, mineralogical and petrographical characteristics of the domanik formation from north samara region in the volga-ural basin, Russia: Implication for unconventional tight oil reservoir potential
www.sciencedirect.com/science/ … ii/S0920410522010920

Provided by Kazan Federal University