Seismicity and development of Romashkino hydrocarbon field’s Almetyevskaya area

The relationship between the various human activities and seismic activity has become more evident in the last several decades. One of the important domains where such a relationship manifests itself is hydrocarbon fields’ development. South East Tatarstan (Russia) is a region where the link between seismicity and the development of the giant Romashkino hydrocarbon field has been established. The goal of the current study is to conduct the causative analysis between the seismic activity and the development of the Romashkino hydrocarbon field’s Almetyevskaya area which is located in the most seismically active zone of the south-eastern Tatarstan.

Study of the component composition of organic matter of the East Pre-Caucasian basin rocks based on the results of lithological, petrophysical and geochemical studies

This study introduces results of lithological, petrophysical and geochemical investigation of Lower Cretaceous (K1) and Middle Jurassic (J2a-b) rocks of East Pre-Caucasian basin. According to pyrolytic and bituminological studies method of separate determination of kerogen and bitumen concentration been developed. In accordance with this method differentiation of organic matter components in different lithotypes of rocks been described. Also relationship between bitumen and kerogen concentrations been revealed. The majority of samples have poor to fair organic richness and poor source potential. Kerogen type is commonly presented by type III and stages of maturity characterized by stages PC3 to MC3. Bitumen compounds have low concentrations of asphaltenes and aromatic hydrocarbons and mainly contains light and heavy resins. Based on petrophysical and geochemical studies a close relationship between the concentration of organic carbon and the weight concentration of potassium nuclides was obtained. This relationship indicates that kerogen in the sediments under consideration is associated with clay minerals, which is also confirmed by the mineral composition of the rocks.

Resources of quartz raw materials, Gargan block, East Sayan quartzite-bearing area

The evaluation (according to structural and geochemical rock properties ) of the quartzites from the East Sayan quartzite-bearing area as a potential source of quartz raw material for crystalline silicon and optical glass manufacturing can significantly expand the forecast resources of this type of raw materials. The geological structure of the Irkut Formation, productive of high-purity quartzites is specified within the Oka-Urik, Urengenur and Urdagargan quartz-bearing areas; geological, mineralogical-petrographic and geochemical characteristics of the main quartzite types are given, the main morphological features of productive high-purity quartzite bodies are specified to predict their occurrence at depth. The major factors in the formation of high-purity quartzite bodies include: 1) quartzites are accumulated in the siliceous-carbonate sequence of the Middle Riphean Irkut Formation within a broad but isolated basin; 2) high-purity quartzite bodies are produced as a result of dynamic recrystallization due to the deformation of primary microquartzites resulting from the collision of the Dunzhugar island arc with the Gargan microcontinent margin. Within the western part of the East-Sayan quartz-bearing area, quartzite reserves as a potential source for silicon metallurgy and production of optical glass were estimated as 134 mln tons.

Application of core X-ray microtomography in oilfield geology

The article presents studies devoted to the practical application of computer X-ray microtomography (micro-CT) in oilfield geology. In particular, the authors give results of using the method for sample defectoscopy before petrophysical studies in order to improve the quality of analyzes. The paper includes an example of assessing the depth of core plugging with drilling fluid; assessing the mineral composition by micro-CT; experimental core studies when modeling the thermal effect on the oil source rocks of the Bazhenov formation. The authors also examine the current state of research in the field of digital petrophysics or digital core. The study is aimed at introducing the micro-CT method into the oilfield process.

On the melt differentiation in the intermediate chamber (by the example of differentiated intrusives of the western slope of the Southern Urals)

The article provides materials on the analysis of the chemical composition of silicates and aluminosilicates that make up the differentiated body of the Misaelga complex, which made it possible by calculation methods to restore the thermobaric parameters of crystallization of the melt in the intermediate chamber. The presence of high-temperature (1472 ºC) intratelluric olivine crystals characterizing the process of magma generation in the mantle and olivine crystallizing under the conditions of the intermediate chamber (1050–1183 ºC) has been established. The calculated crystallization temperature of pyroxenes indicates that they crystallized together with olivine from the bulk of the rocks, and the established variations in the P–T parameters (T = 950–1045 ºC, P = 4.0–7.4 kbar) for plagioclase and amphibole complete the quantitative characteristics of high-temperature melt crystallization processes. It is shown that the calculated Р–Т parameters of the crystallization of the melt that formed the intrusive massif make it possible to classify its ultrabasic horizon as picrite complexes of the second type that we identified earlier. Modeling of the crystallization process carried out using two models – according to the algorithm of H.D. Nathan and K.K. Van Kirk and the software product KOMAGMAT – made it possible to establish that the most probable mechanism for the formation of a differentiated body of the Misaelga complex was directional crystallization with gravitational deposition of olivine at the initial stages of the formation of the massif.

Particle removal by two-phase filtration flow from a porous medium under wave action

The paper discusses the influence of wave action on the process of detachment and removal of particles from a porous body by a two-phase filtration flow. When modeling this process, the problem of the influence of the wave field on the force under the action of which the particles are detached from the pore walls is solved. For the first time, a pore-size distribution function is used for its solution. An expression for the critical flow velocity under wave action has been obtained. Critical frequency value of wave action depends on the capillary radius and the smaller the capillary radius is, the higher frequency is needed to enhance the effect of the action. At higher frequency of oscillation the peak of maximum change in the thickness of the sedimentary layer is shifted towards the pores of small radius. To maintain the influence of the wave field on the filtration parameters of the porous medium, the wave action should be carried out at a dynamically changing frequency range to increase the coverage of the effect of as many pores as possible. It is shown that particle removal during wave action increases due to the action of inertial forces, which reduce the influence of forces holding the particles on the pore surface.

Assessment of the ecological state of Kazan surface waters

The study of the influence of technogenesis on the state of surface waters in urbanized areas is one of the most urgent ecological and social problems. For processing and analysis of hydrochemical indicators of surface water bodies of Kazan for the period 2014–2020 the generally accepted stasticial indicators, as well as the methods of multivariate statistics were used. Hydrochemical models were built using the ArcGisMap software package. The data were grouped using the cluster analysis method separately for each hydrological season with the allocation of 6 groups of hydrochemical components in relation to the maximum permissible values. It has been revealed that the minimum technogenic load on the surface waters of the city falls on the spring period. Based on the analysis of the results obtained, an ecological and hydrological assessment of the state of surface waters was carried out. It was showed that the water bodies of Kazan are classified as unfavorable water bodies.

Geochemistry of water-soluble gases in the oil and gas bearing sediments of the zone of junction between the Yenisei-Khatanga and the West Siberian basins (the Arctic regions of Siberia)

The results of the studies of geochemical and zoning features of water-dissolved gases in the Mesozoic sediments of the junction between the Yenisei-Khatanga and the West Siberian basins are reported. The stage of industrial oil and gas content is more than 3 km thick and involves the depth range from 750 to 4000 m. Waters occurring in the region contain methane, their total gas saturation is 0.3 to 4.6 dm3/dm3, and CH4 content in 88.9 to 95.4 vol. % on average. An increase in the concentrations of carbon dioxide and methane homologues is observed with an increase in the depth, which is accompanied by a regular decrease in the concentrations of methane and nitrogen. In general, water-dissolved gases from the Neocomian and Jurassic reservoirs have similar compositions (С1 > N2 > C2 > C3 > n-C4 > i-C4 > CO2 > i-C5 > n-C5). The water-dissolved gases of the Aptian-Albian-Cenomanian sediments are distinguished by lower concentrations of methane homologues (С1 > N2 > C2 > CO2 > C3 > i-C4 > n-C4 > i-C5 > n-C5), with the total content of heavy hydrocarbons (HHC) equal to 1.44 vol. %. Vertical zoning of the composition of water-dissolved gases is determined by the distribution of hydrocarbon pools in the Jurassic-Cretaceous section. A regular increase in the average values of the factor of enrichment with hydrocarbons (HC) (from 37 to 154) was established, along with a decrease in the ratio of CH4/ƩHHC (from 130 to 7), C2H6/C3H8 (from 41 to 2) and i-C4H10/n-C4H10 (from 2.6 to 0.6) from the Aptian-Albian-Cenomanian reservoirs to the Jurassic ones. The zone with anomalous He concentrations within the range of 0.4–0.9 vol. % was detected in the Neocomian and Middle Jurassic sediments. This zone is localized at the north-western slope of the Messoyakh inclined ridge (the Anomalnaya, Turkovskaya, Pelyatkinskaya and Sredne-Yarovskaya areas). The nature of this anomaly needs further studies.

Interpretation of electrical logging data from the Hettangian-Aalenian terrigenous reservoirs in the Southeast of Western Siberia

In the southeast of Western Siberia, the most studied are the Upper Jurassic deposits, most of the oil and gas fields being confined to them. However, the probability of discovering new hydrocarbon deposits in the Upper Jurassic horizons is extremely small. Therefore, of great importance is finding new hydrocarbon deposits in less studied deep-lying complexes. The article considers the development of a criterion for determining the saturation type of the terrigenous reservoirs in the Hettangian-Aalenian deposits in the southeast of the West Siberian sedimentary basin. We use the example of the Ust-Tym megadepression, a large depression located in the central part of the Tomsk region. The Lower and Middle Jurassic sections are represented by the Urman and Togur formations, Salat formation (Peshkov formation is its isochronous analogue) and Tyumen formation, and characterized by the alternation of predominantly sandy (potential reservoirs) and argillaceous-carbonaceous (seals) sequences. In the studied interval, tests were carried out in just a few wells, for which reason the identification of deposits and promising objects is complicated. Determining the type of reservoir saturation will significantly improve the assessment of oil and gas potential. As a result of interpreting lateral logging sounding data, the geoelectric parameters of the invasion zone and undisturbed formation were reconstructed for the Lower Jurassic and Aalenian deposits. Based on the well logging data interpretation by means of numerical inversion, we obtained the criterion for the saturation type of the reservoirs (Ju11-17) in the Hettangian-Aalenian complex. The boundary resistivity values for the oil-saturated reservoirs vary from 8 to 20 ohm∙m, while for the water-saturated ones they do not exceed 5 ohm∙m.

On the possibility of introducing X-ray computed microtomography into the practice of biostratigraphic research

Currently, the techniques applied for extraction and study of conodonts from siliceous rocks are associated with a number of problems. This makes it difficult to solve many problems in the areas of development of the volcanic and volcanic-sedimentary rocks, where cherts, jaspers, and phtanites are the only sedimentary formations for dating these deposits. On X-ray computed microtomography it is possible to avoid some problems to obtain not only excellent 3-D images of conodonts, but sections in any direction too, as well as in video formats. It is shown that similar results are successful under the hollows after the dissolution of the conodonts. There is no problem in application of X-ray microcomputed tomography when conodonts have been already found on the surface or inside of the sample, or if the content of conodonts in the rock is obviously high. In such a case the scanning without preliminary search is ensured. In cases when conodonts are rare and not obvious, it is proposed the following technique of their discovery. The rock sample is cut into plates. The conodonts are search for on the surface of the plates, moistened with a mixture of glycerin and water under a binocular microscope. If it is necessary (when the rock is opaque), the result is checked by a chemical reaction: 5–10 % hydrochloric acid plus 1–2 crystals of ammonium molybdate are put on the surface of the sample. The appearance of a yellow sediment means the presence of phosphorus, to indicate the probability the detected object to be a conodont. Next, the sample should be washed from acid, its size should be decreased. Then the microtomographic study should be performed.