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Syncytial connections between neurites were found using electron microscopy in the nervous system of cats, young pigs, as well as in the culture of mollusk ganglia cells. The possibility of detecting neural syncytia using the method of the unmasking of digital images of arborizations of interneuronal connections in the nervous tissue of the brain was established, but this method was not used to study of the enteric nervous system. The aim of the study was to analyze the submucosal and intermuscular autonomic nerve plexuses of the intestine of the domestic cat (Felis catus) by method of the unmasking of digital images. The material for the study was preparations of the small and large intestines. All manipulations with animals were carried out in compliance with Directive 2010/63/EU of the European Parliament and of the Council of the European Union on the protection of animals used for scientific aims. The experiments were carried out on mature outbred cats (n=45). To obtain preparations, the intestinal vessels of experimental animals were sequentially perfused with solutions of barium hydroxide, then silver nitrate, and hydroquinone. After perfusion, intestinal preparations were taken and fixed. The obtained histological preparations (including ultramicroscopic ones) were studied by the method of unmasking of digital images (of the downscaling of the image resolution). As a result of the study, numerous distant syncytial anastomoses connecting the bodies of neurocytes of all types of Dogiel cells were revealed for the first time, and their properties were established. Widespread multiple morphological mono- and polyvalent ring syncytial structures were found. Their supposed function is the opposite direction of electric and axoplasmic flow. An in vivo feature of the reflex syncytial apparatus of the enteric nervous system is the formation of multi-tiered closed loop-like contacts of nerve fibers and type II Dogiel cells with pronounced local and diffuse receptor branches. Thus, a characteristic feature of the enteric nervous system is the presence of multicellular connections of neurocytes in the form of a network of distant syncytial anastomoses. These anastomoses are real proof of the reticular principle of the structural organization of the autonomic plexuses of the enteric nervous system and the reticular concept in general.

Core material taken over a section of the Bavly multipay field of Tatarstan (Russia), and extracts from it have been studied by thermal analysis, IR and EPR spectroscopy, and gas-liquid chromatography. The trends of changes in the amount and fractional and hydrocarbon-group compositions of residual oil and oil components irreversibly adsorbed on the rock depending on the age of deposition have been revealed. In rocks from the Trans-Volgian and Dankovian–Lebedyanian horizons attributed to domanik deposits, the organic matter content has been determined with an estimate of the proportion of bitumoid and kerogen in it, and the peculiarities of their fractional and hydrocarbon-group compositions have been revealed.

Hydrocarbon reserves in carbonate reservoirs account for 38% - 60% of total world reserves, according to different estimates. In Tatarstan, carbonate reservoirs are found, mostly, in the eastern slope of the Melekess Depression and the South-Tatarian Arch. The carbonate reservoirs are confined to the Middle and Lower Carboniferous sediments, the Upper Devonian (including the domanik sediments), and the Upper Permian (the Kazanian heavy oil accumulations). Considering an extensive geographic and stratigraphic range and differing tectonic and sedimentation environments, the carbonate rocks are characterized by a variety of reservoir properties. In contrast to terrigenous rocks, the carbonate void space is complicated by secondary processes that took place much later than the sedimentogenesis-lithogenesis stage. Numerous fissures, caves, sutures, and stylolites form the void space of the reservoir rock matrix containing commercial hydrocarbon reserves. In addition to fracturing and vugginess contributing to increase of void space of carbonate rocks, the secondary processes include sulphatisation and secondary dolomitization (in limestones), adding to deterioration of reservoir properties. The secondary processes impede understanding and evaluation of reservoir properties and saturation potential, in particular, determination of the oil and gas saturation factors (Dyakonova T.F. et al, 2019, Akhmetov R.T. et al, 2017)/ In the western slope of the South-Tatarian Arch, carbonate reservoirs are confined to the Middle and Lower Carboniferous sediments. Numerous RCAL and SCAL investigations provided valuable insight into these targets. In this paper, we used data from the laboratory experiments and studies of core and oil samples from the six neighbor fields on the western slope of the South-Tatarian Arch. Because of common sedimentological and tectonic sedimentation environments and lithological similarity of rocks within the stratigraphic referencing, the six fields under analysis were considered as analogous, and the results of the laboratory studies of the samples were reviewed collectively.

This paper presents the results of a comparative study of rock samples from depth intervals of 1705–1728 m of Semilukian–Mendymian (domanik) deposits of the Berezovskaya area and 1379–1394 m of carbonate (domanikoid) deposits of the Dankovian–Lebedyanian horizon of the Zelenogorskaya area of the Romashkino oilfield. It has been shown that rocks with different mineral compositions differ in the content and composition of organic matter (OM), including kerogen, and its resistance to thermal impacts. The yield of extracts from the rocks and the differences in their group, structural-group, and hydrocarbon-group compositions have been determined. According to the molecular-mass distribution of normal and isoprenoid alkanes, the extracts from the rocks are oils of types A1 and A2. Peculiarities in the distribution of higher biomarkers have been revealed, indicating that the hydrocarbons of the examined samples of domanik and domanikoid rocks are genetically uniform in nature, but differ in the geochemical environment of the transformation of the original OM and, possibly, in the effect of migration processes.

In the process of oil reserves’ development, the in-situ stresses change. Knowledge of rock failure constraints will allow prediction of behavior of rock when subject to subsurface stress change. In this study, we used the results of studies of the Pashiyan sandstone core samples recovered from the Tashliyarskaya area well No. 14403. Six sets of samples, each consisting of three samples taken from the homogeneous intervals at the same depth, were used to determine the ultimate tensile strength, uniaxial and triaxial compressive strength in the in-situ conditions. An analysis of the methods for constructing a rock strength certificate, and comparison of the strength criteria described in State Standard 21153.8-88, the Mohr-Coulomb linear strength criterion and the non-linear Hoek-Brown criterion are provided. The Hoek-Brown criterion has the advantage of describing a non-linear increase in strength with an increase in overburden pressure and more adequately reflects the properties of rock. For the first time, a comparison of applicability of strength criteria obtained by different methods and based on the laboratory core analysis was made to determine their practical applicability. Comprehensive studies of the strength characteristics have never been previously conducted, and the results obtained will serve as the basis for further analysis and application in order to improve the development of the terrigenous Devonian Romashkinskoe field.

The article presents the results of a comparative analysis of the composition and physicochemical properties of crude oils produced from different horizons of the Carboniferous and Devonian deposit...

The influence of various media on the degree of transformation of kerogen of Domanikovian rocks in hydrothermal processes was studied in model experiments. Autoclave experiments were conducted with debituminized rock in inert, hydrogen, and carbon dioxide media. A common mechanism was observed for all the reaction media under the influence of hydrothermal factors: the kerogen content in the rocks decreases and the yield of free hydrocarbons extractable from the rocks by organic solvents increases. The saturated hydrocarbon content is higher in the group composition of the experiment products compared to the original extract due to decrease in resin and aromatic hydrocarbon content. In the original extract from the Domanikovian rock, as well as in the experiment products, there are two solid dispersed phases, namely, asphaltenes soluble in aromatic solvents and their modified structures of the type of carbenes and carboids insoluble in toluene due to their more condensed structure with a smaller number of aliphatic substituents. The most pronounced decrease in resin content is observed in carbon dioxide medium with a marked increase in asphaltene content in the experiment products relative to the original extract. In hydrogen medium, on the other hand, asphaltene content decreases in the experiment products, but, in comparison with the carbon dioxide medium, carbenes and carboids are formed more intensely due to decomposition of the kerogen structure. Asphaltenes and carbenes-carboids were found to differ in structure and paramagnetic properties.

The oil generating potential of Domanic rocks from Dankov–Lebedyan horizon of the Zelenogorsk area of Romashkino oil field was evaluated by Rock-Eval pyrolysis technique. The result of given method...

The oil generation potential of low permeability carbonate reservoir rock from the Dankov-Lebedyan horizon of the Domanikovian deposits of the Upper Devonian of the Zelenogorsk area of the Romashkino field is evaluated as a function of content and composition of the organic matter in the reservoir rock and of the composition of the shale oil extracted from the rock by organic solvents. In comparison with the shale oil produced from the carbonate reservoir rock of coeval deposits by hydrofracking of the rock formation, the extracts from the rocks contain more resins and asphaltenes and less saturated fractions predominantly comprised of high-molecular-weight n-alkanes. In model experiments, the influence of the temperatures 20, 250, 300, and 350°C on the conversion of organic matter of the Domanikovian carbonate rock in a carbonic acid hydrothermal system are studied, and the yield and quality of the extracted hydrocarbons are evaluated. It is demonstrated that the thermal effect at 200 and 250°C on the rock facilitates more intense and complete extraction of oil hydrocarbons. Processes of degradation of high-molecular-weight components and insoluble kerogen occur at temperatures above 300°C, leading to an increase in then yield of extracts from the rocks and an increase in them of the content of saturated hydrocarbons whose composition approaches the composition of the shale oil extracted from low permeability carbonate reservoir rock. Results of the investigation provide grounds for suggesting that carbonate rock of the Dankov-Lebedyan horizon contains productive formations that could become an additional source of petroleum hydrocarbons when developed by hydrothermal technologies.

The model experiments regarding the conversion of organic matters from carbonate rock samples of Dankov-Lebedyan deposits of Zelenogorskaya area and siliceous-carbonate rocks of Semiluki-Mendym deposits of Berezovskaya area of Domanic formations of Romashkino oil field were carried out. Two types of experiments were carried out: (1) the hydrothermal treatment of rocks at a temperature of 350°C in the presence of carbonic acid and a water content of 30%; (2) pyrolysis at temperatures of 350 and 600°C in the presence of hydrogen. The yield and quality of extracted hydrocarbons from the rocks depending on the mineral composition of rocks, content and composition of organic matter, and thermal stability of kerogen under hydrothermal influences were evaluated. Application of electron paramagnetic resonance in pyrolysis processes revealed the difference in mineral content of rocks (Mn2+, SO3−, and SO2− ions) and free radicals R∗, as well as in vanadyl ion (VO2+) concentration. It is established that an increasing temperature of pyrolysis promotes the formation of new free organic radicals in rock samples: in Domanic rocks of Semiluki-Mendym deposits at 350°С and in carbonate rocks of Dankov-Lebedyan horizon at 600°С. This indicates different ability of oil-generating potential of rocks with hydrothermal and pyrolysis technologies.

Depositions of the Domanic type in the territory of Tatarstan are stratigraphically associated with carbonate-siliceous deposits of the Upper Devonian part of the section. These deposits, enriched with organic matter, are characterized by the ability to generate liquid and gaseous hydrocarbons and accumulate them in the form of deposits of unconventional type. In this paper, the results of geochemical studies of rock samples from the depth interval 1705-1728 m of the Semi-Bug-Buregian deposits of the Berezovskaya area of the Romashkino oil field are presented. It is shown that the rocks, in spite of the narrow core sampling interval, differ in the content of quartz and calcite, as well as in the admixture of minerals such as muscovite, pyrite and albite. The content of organic matter according to thermal analysis data varies from 1.97 to 35.48 %, a significant part of which falls on an insoluble organic matter - kerogen. The influence of hydrothermal processes on the production capacity of the organic matter of these rocks is shown to generate hydrocarbons at temperatures of 200, 250, 300 and 350°C in a carbon dioxide medium. The yield and quality of the products obtained is estimated. The results of the research give grounds to believe that: firstly, the rocks of the Berezovskaya area of the Romashkino oil field have not fully realized their oil potential and the hydrothermal effect on them contributes to the thermal maturation of organic matter in the rock; second, at these temperatures, more intensive recovery of free hydrocarbons from the rock occurs. Thus, the hydrocarbon potential of the house rock is determined by the composition and content of liquid bituminous components that are in a free state in the rock, as well as the products of destruction of tar-asphaltene substances and macromolecules of insoluble kerogen and, consequently, it can be successfully realized with further optimization of hydrothermal processes directed to increase the quantity and improve the quality of the extracted fluids.

The structural regularities of the organization of interneuronal syncytial cytoplasmic connections between neuronal bodies in gyrus dentatus and CA1 and CA2 (CA is cornu ammonis) of hippocampus, as well as between cell neurites of the caudal mesenteric ganglion were studied by transmission electron microscopy. The syncytial perforations are located only on the base of tight junctions. The perforations have rounded edges corresponding to the fusion edges of perforated membranes of adjacent neurons - or where their edges have a form of thinned plate - a remnant of the tight junction. In the lumen of the perforations, remnants of contact membranes - residual bodies - are revealed. On living neurons in tissue culture, the syncytial connection of two contacting processes of different neurons is found during the death of the body of one of them, but with preservation of viability of its processes that contact with other neurons.