Development of the gold mining industry is in the first place associated with an increase in the mineral resource base, development of promising deposits and improvement in the quality of raw materials. At the same time, experts have been noting a deterioration in the quality of alluvial gold reserves over the last years both in Russia as a whole and in Eastern Siberia in particular. Therefore, the purpose of this research is to analyze the dynamics of the mineral resource base of gold mining in the Lena gold-bearing area as well as to substantiate the development trends of the placer development technology. The assessment was given to the state of the mineral resource base of the gold mining industry of the Irkutsk region in the period from 2000 to 2021. A quantitative and qualitative characteristic of alluvial gold reserves was provided with identified key changes caused by placer mining over the past 20 years. Having indicated the deterioration dynamics in the quality of alluvial gold reserves, the authors specified its reasons for the period under analysis. In addition, a brief description of the main mining and engineering indicators of the large and medium-sized alluvial gold deposits worked out in recent years is given. The distribution structure of reserves in technogenic deposits is presented. The conclusions are formulated on the results of the research performed, relevant problems of modern placer gold mining are formulated and the prospects of placer mining in the Irkutsk region are assessed. The replenishing possibilities of the mineral resource base by involving technogenic reserves in the development are described.

The Mnogovershinnoye gold deposit (Khabarovsk Territory, Russia) today is a significant industrial facility, which features extension additions as a results of additional in-mine exploration of deep horizons and identification of new objects within the ore field. The purpose of this work is to study the formation stages of ore minerals of one of the deposit sites as well as to identify the mineralogical and structural-textural features of ores. The methods of mineralogical and petrographic study of the material composition of ores are widely used in geological practice and allow to determine the material features of the studied objects as well as describe the ore formation process. The study of ore types was carried out using an Olympus BX51 microscope. Field observations performed by the authors served the base for the mineralogical and petrographic study of ore samples and host rocks of the Sredniy site of the Mnogovershinnoye deposit, which led to a slightly different understanding of formation stages of ore mineralization of this section of the deposit. The study revealed at least three formation stages of the material complex of this site of the deposit. The first stage is a magmatic one. It characterizes with the formation of pyrite of the first generation. The second stage is an ore hydrothermal one, as a result of which the gold-sulfide mineralization was formed including pyrite of the second generation, chalcopyrite, magnetite, kustelite. Gangue quartz was formed at the end of the second stage together with such ore minerals as pyrite, chalcopyrite, magnetite, and an insignificant amount of kustelite and native copper. The third stage is an exogenous one, during which substitution and oxidation structures were formed with iron hydroxide evolution. The studies of the ores of the Mnogovershinnoye deposit have shown once again the presence of polysulfide multistage mineralization, which had been developing in close connection with the magmatic process. Knowledge about the deposit formation stages is an integral part of the creation of geological and structural models of the deposit, which are necessary to increase the efficiency of geological exploration within the studied objects.

Modern forecast, exploration and development of hydrocarbon deposits within natural carbonate reservoirs of buried bioherm (reef) structures in the north of the Irkutsk region and the Sakha Republic (Yakutia) areas within the NepaBotuoba Anticline apply the most advanced technologies of 3D seismic exploration and geoelectric prospecting supplemented with a set of new interpretation approaches and analysis attributes contrasted against wide range of well logging data. The recent discoveries of hydrocarbon deposits in the northern reefs shoved the bioherms of the Irkutsk amphitheater in the shadow. The purpose of this research is geological study of biohermal carbonate formations of the Lower Cambrian age in the outcrops of the Bozhekhansky megaswell in the Baikal region. The choice of this object of study is due to the fact that the first oil and gas inflows were obtained from the wells of the Atovskaya, Osinskaya, Birkinskaya, Khristoforovskaya, Balykhtinskaya and Tuturskaya areas. Field geological routes and office processing of data on cuts and polished thin sections of sample surfaces were carried out including microscopic studies in the thin sections of samples and archival collections of cores from deep oil and gas prospecting wells. In 2021–2022, while prospecting in the south of the Irkutsk amphitheater, the authors explored stratified, nodular and columnar stromatolites found within the compound Bozhekhan megaswell of Cambrian carbonate outcroppings. Carbonate intraformational sedimentary breccias identified in the area under investigation feature a great variety in their fragment sizes and inclusions. The stromatolites’ structural features were studied by the cuts and polished thin sections of sample surfaces. Microphytolites were found in the thin sections and described. The authors also took advantage of the opportunity to study an archive collection of the thin sections of VendCambrian and Lower Cambrian carbonate strata from the Akhinskaya area’s wells at the Bozhekhan megaswell and from the Upper-Lena uplift to the north-west. The conducted study implies that Cambrian bioherm outcroppings of the Bozhekhan megaswell-type uplift within the Cis-Baikal trough are, in a sense, model geologic objects. The study of biologic and genetic varieties of Lower Cambrian phytolites, diagnostic features of the organogenic structures, their inner structure and formation processes of the reef ecosystem may provide a region-level prognostic key to the research of Cambrian sediment system in the south of the Siberian platform.

Today the imitations of gold nuggets are highly promising materials in conceptual jewelry design. The manufacturing technology of these materials is based on melted brass casting in a cooling liquid. The purpose of this research is to identify the most favorable technological processes to obtaining high-quality simulants of gold nuggets. The article presents the results of the experimental studies of CW508L brass. The most favorable technological parameters have been identified. They include the melt temperature up to 970±5 °C and use of water with the temperature not higher than 20–25 °C as a cooling liquid. Adherence to the specifications allows to obtain the casts, which superficially resemble natural gold nuggets found in alluvial gold deposits. The casts’ intricate shape and uneven relief providing this resemblance are due to the specific crystallization conditions of brass that differ from the crystallization conditions under conventional casting. The research involved the analysis of the chemical composition of the alloy samples before tests and the samples obtained after casting. After processing the alloy has featured an insignificant decrease in the zinc percentage, and an increase in the impurity content (silica, sulfur, iron, and chrome). The metallographic analysis of the initial sample of CW508L brass has shown a single-phase microstructure that is a solid solution of zinc substitution by copper. The similar study of the casts obtained in the experiment has shown the presence of a β-phase in their structure (along with an α solid solution) that is a CuZn-based solid solution having a positive effect on brass mechanical properties. This microstructure is typical of the alloys undergone accelerated cooling that qualitatively changes the process of melt converting into a solid substance.

This research is aimed at the geoecological assessment of the territory of the Khabarovsk agglomeration in terms of location possibility of construction and demolition waste or recycling of the latter, as well as the environmental impact of the waste. The annual volume of construction waste generation in Khabarovsk is 407.5 thousand tons (326.9 thousand m3). All waste from the construction sector of the Khabarovsk agglomeration is sent to landfills. The study territory distinguishes two areas: the one of the flood plain and above-floodplain terraces of the Amur river in the western part, which is flooded in the periods of high and catastrophic floods and features unfavorable geoecological conditions, and the area on the right bank of the Amur river in the eastern part of the territory with urban development where the groundwater levels exceed 2 m. In the course of the study, the authors identified the potential locations of the construction waste recycling complex and considered the possibility of arranging a site for temporary storage of raw materials having given the rationale for this choice. The methods applicable in the field of waste recycling under the formation of the construction and demolition waste processing industry are described. The potential of using waste as material resources as well as the environmental aspects of waste recycling in the form of building materials are evaluated. It is noted that by 2030, the carbon footprint will be 116.8 thousand tons of carbon dioxide as a result of waste disposal at municipal solid waste landfills. To reduce the carbon footprint (carbon dioxide emissions) during the construction works involving concrete and bituminous concrete it is justified the use of processed aggregates based on recycled crushed stone. The sites favorable for the placement of construction waste recycling enterprises have been identified during the survey of the city. They are located outside the existing and prospective urban and industrial development, as well as outside the zones of specially protected natural areas.

Borehole cleaning is still a major challenge for most directional wells despite a significant progress achieved in drilling fluids, tools and field practice, as well as in the development of academic and industry research. Insufficient cleaning of the borehole causes undesirable phenomena in the form of various complications. Therefore, the purpose of the conducted research was to present the main correlations that determine the nature and cleaning degree of the annular eccentric space of the well and to analyze these correlations presented in the form of indicators in order to improve them. The object of the research is the mechanics of cuttings removal from an inclined or horizontal well. In the frameworks of this research mechanics is mathematically displayed in the form of indicators reflecting one or another physical aspect of the cuttings removal process. The research methodology consists in the analysis of the composition of indicators, evaluation of the significance of the indicator constituents, identification of the quantitative contribution of the indicator to the cleaning degree of the annular space of the directional well from destruction products while sinking the borehole. The study resulted in the introduction of the following indicators: equivalent circulation density, slip velocity and cuttings removal index. The physical essence of indicators in their mathematical form is shown with the focus on the slip velocity. The definition of the latter, which is widely accepted among the specialists indicates the rate of washing of cutting particles by the drilling fluid during its transportation to the day-light surface. This indicator is one of the main ones that determine the hydrodynamics of the cuttings transport process. To simplify the calculation of the indicator, it is proposed to use the dimensionless Lyashchenko criterion.

The purpose of the presented study is to give a theoretical substantiation of the formation process of a high-clay sand dispersoid from placers with a high content of fine and finely dispersed gold under changing hydrodynamic parameters of the hydro mixture flow by means of enclosing and reflecting surfaces of the proposed installation. The object of the research is the process of hydrodynamic disintegration. The subject of the study includes the main parameters of the hydrodynamic effect on the mineral environment and the destruction nature of high-clay sands under hydrodynamic conditions. While doing the research, the author used the methods for constructing a mathematical model of dispersoid transformation under hydrodynamic effect on the hydro mixture, analytical and numerical calculations. The analysis of the aspects of hydrodynamic phenomena and interactions made it possible to substantiate the dispersoid formation process based on the intensification of microdisintegration and to identify the characteristic impact factors as well. Based on the theory of changes in the thermodynamic potential of the system of particle surfaces under dynamic exposure, a method has been proposed for determining the hydrodynamic variation parameters of the hydromixture structural component in the closed cavity of the generator when interacting with the elements of the enclosing and reflecting surfaces. The performed numerical calculations allowed to reveal a significant increase in the specific interphase surface of the dispersoid of the mineral component. The interaction of the elements of enclosing and reflecting surfaces according to the proposed innovative layout of elements location in the generator under the directed supply of the hydromixture from the nozzle into a closed cavity resulted in the increase from 3 to 4 times. A new design of a hydrodynamic generator and a flow diagram have been introduced on order to activate the extraction process of microparticles of valuable components.

The purpose of the study is the laboratory determination of proppant indentation coefficients depending on the geological composition of the oil source rocks and their application in the design of hydraulic fracturing treatment. The laboratory researches used the core material of oil-producing deposits of the Domanic formation. The indentation of prop pant was carried out on the CTM-100 compression testing machine, in order to eliminate the measurement error, the size of the cells was additionally specified using ADF U300P microscope with the operation capacity either in reflected light or reflected and transmitted light only. As a result, the geological features of the Domanic complex were confirmed: a large content of organic matter was traced on the core material, the bulk of the rock was composed of carbonates with frequent lithological layering. The indentation coefficient of 20/40 proppan were as following: 0.2–0.4 mm in limestones, 0.23–0.45 mm in clay limestones, 0.47 mm for organic matter. The indentation coefficients for 30/50 proppant were as follows: 0.1– 0.5 mm in limestones, 0.13–0.55 mm in clay limestones, 0.47 mm in organic matter. The use of the obtained coefficients in the design of hydraulic fracturing treatment allowed to specify the fixed width of the crack opening that will have a positive effect on the predicted starting well yield under subsequent modeling. The proppant indentation is in direct relationship to the composition of the oil-producing rocks. When using the proppant coefficients it is advisable to pay additional attention to the proppant tracking map. The use of laboratory studies with subsequent modeling in the hydraulic fracturing simulator allows more accurate understanding of the fixed geometry of the crack of the formation fracturing. Estimation of the crack opening width at the stage of hydraulic fracturing design makes it possible to adapt the parameters of formation treatment, which has a positive effect on the lifetime of the crack width as well as on the well yield.