Vol 276 Iss. 1

Specific features of deep structure and tectonics of the Magadan and West Kamchatka shelves in the Sea of Okhotsk and adjacent area of the Kamchatka Peninsula were verified by geological and geophysical modelling. The investigations aimed at studying the localization pattern of hydrocarbon fields on the northern flank of the Okhotsk oil and gas province are based on results of regional and medium-scale geological surveys and prognostic and prospecting studies, geophysical survey data (gravity anomaly field Δg in the Bouguer reduction with an intermediate layer density 2.67 g/cm3, anomalous magnetic field ΔTа, regional seismic lines and the results of their generalizations), and petrophysical well survey materials. Different algorithms for solving the direct and inverse problems as well as pattern recognition with and without training were used in processing and interpretation of potential geophysical fields. The studies showed that the specific features of deep structure and tectonics of the region are determined by the sequence and nature of manifestation of Mesozoic and Cenozoic orogenic processes at the boundaries of the Eurasian and Okhotsk Sea lithospheric paleoplates. The study of regional shear zones developing along the Okhotsk-Chukotka suture zone and the Okhotsk-West Kamchatka Block demonstrated their vital influence on the morphology of sedimentary basins. Thus, the tectonic activity in the Okhotsk-Chukotka shear zone extending subparallel to the Eurasian coast, led to formation of an extensive network of feather dislocations and basins of two types: large longitudinal shear depressions (sedimentary basins that form due to extersion along strike-slip faults) and shear-pull-apart basins oriented at an angle to the axis of the main shear. Mapping of horst uplifts makes it possible to confirm the position of oil and gas formations prioritized for exploration according to the structural criterion.

In the current mine surveying practice, when assessing the harmful impact of underground construction on the earth's surface and undermined objects, the geotechnical system underground structure – rock mass is traditionally considered, which does not include the surface infrastructure. Such an approach can lead to distorted estimates of load levels, impacts and potential deformations for both buildings and the earth's surface. In order to determine the influence of the building and assess the interaction of elements of the geotechnical system tunnel – rock mass – building, the study analyses the undermining of the historical stage building of the Mariinskii Theatre by a complex of workings in Saint Petersburg metro station Teatralnaya. Numerical simulation by the finite element method in the PLAXIS 3D software package is used, the geotechnical model is calibrated in accordance with data of the field mine surveying and geodetic measurements. The models show that during undermining of buildings, their heterogeneous structure, weight and spatial rigidity significantly affect the distribution of deformations in the base of the construction, which is confirmed by localization of cracks in load-carrying structures that appeared after the start of mining operations. When assessing and predicting deformations by numerical methods, it is not always sufficient to simulate the rock mass – tunnel system, since this can lead to overestimated predicted values of the earth’s surface deformations, underestimated values of subsidence, and an incorrect assessment of the harmful effect on the undermined object. It was concluded that only an integrated approach using simulation, field measurements and survey data can ensure a correct analysis of the interaction of the rock mass, underground structures and above-ground infrastructure facilities with complex spatial geometry and allow a reliable assessment of the harmful effect on the undermined object with reference to structural damage. This contributes to adoption of adequate and timely protection measures for buildings and structures.

The results of experiments aimed at studying the influence of various nanomaterials on the key properties of drilling emulsions based on diesel fuel are presented. The nanomaterials used included spherical SiO2 nanoparticles with sizes of 5 and 80 nm, single-walled and multi-walled carbon nanotubes, as well as Al2O3 nanofibers. The nanomaterials were incorporated into standard formulations of drilling fluids containing a hydrocarbon phase of 65 %, with a mass concentration of nanomaterials in the emulsions reaching up to 2 %. The study examined the rheological, filtration, and antifriction properties, as well as the colloidal stability and inhibiting capacity of the modified drilling emulsions. It was demonstrated that even at low concentrations, the nanomaterials significantly affect the properties of drilling emulsions, indicating their potential for practical applications. Furthermore, the use of nanotubes exhibits effectiveness at lower concentrations (0.1 wt.%) compared to spherical nanoparticles.

Quarry wastewater from open-pit iron ore mining enterprises is a source of contamination of surface water bodies and groundwater with chemical compounds used during development, including the products of decomposition and incomplete consumption of ammonium nitrate during blasting operations in mines – nitrate, nitrite, and ammonium nitrogen. Such characteristics of mining wastewater as high tonnage, organic matter deficiency, and sparse microbiome must be considered when selecting neutralization methods. Biological and physicochemical methods are used to treat wastewater contaminated with nitrogen compounds. Some methods are economically infeasible due to the significant volumes of wastewater generated. An important task is to find an economically viable and highly effective method for treating quarry water from nitrogen compounds. The article presents the results of theoretical and experimental studies of the possibility of using a permeable geochemical barrier based on a redox system consisting of iron scrap and carbon-containing material (screenings from the production of birch activated charcoal) for treating quarry waters from nitrate ions. Thermodynamic analysis allowed us to determine the chemistry of nitrate ion reduction by the Fe0-C redox system in a neutral and slightly alkaline medium typical of quarry waters. The study of the kinetic patterns of nitrate ion reduction showed that the process rate is described by a first-order equation. It was found that the rate constant for nitrate ion reduction increases with reaction mixture temperature rise: at 278 K – 0.0365 min–1, 283 K – 0.0416 min–1, 288 K – 0.0809 min–1, 293 K – 0.0901 min–1. The data obtained will allow substantiating the choice of the reactive barrier or reactor design for the treatment. Experimental studies on the treatment of real and model quarry waters in a laboratory setup simulating a geochemical barrier proved the high efficiency of nitrate ion reduction (more than 97 %). The treated water meets the requirements for water discharge into fishery water bodies.

For years attempts have been made in the drilling industry to increase the drilling efficiency and decrease the associated costs. The drilling efficiency can be evaluated by comparing applied energy, i.e., mechanical specific energy, with rock strength. The mechanical specific energy is defined as the energy required to destroy a unit volume of the rock. Over the years, this concept has been refined, and researchers proposed various models. Mechanical specific energy directly affects drilling efficiency, as excessive energy can lead to drill string vibrations and bit wear. In this study, a database was established by collecting drilling and log data from the Asmari formation in one of the oil fields of Iran. Various forms of specific energy were examined to develop the appropriate model based on operational conditions and the formation being drilled. Additionally, the confined compressive strength of the rock in the studied well was calculated. The results showed that the developed specific energy model provides a realistic energy value, as it includes all relevant parameters with an output close to the rock strength. Based on the comparison of mechanical specific energy with confined compressive strength, the optimal drilling parameters were determined: weight on bit ranges from 22.24 to 44.48 kN, flow rate ranges from 0.027 to 0.029 m³/s, torque ranges from 2522 to 3091 N·m, and rotational speed ranges from 160 to 180 rpm. Also, an inefficient drilling zone was identified in the studied well, where excessive applied energy compared to rock strength led to the drill bit damage and a significant reduction in penetration rate. The results highlighted the importance of drilling efficiency estimation in the drilling process, where an economic and technically feasible decision can be made by comparing the surface input energy with the rock strength.

This article outlines the key principles and assumptions that form the basis of the filtration consolidation model for water-saturated clay soils described by K.Terzaghi in 1925 for calculating the settlement of structures. One of the main assumptions that requires revision is the notion that the pore water in clay soils has properties identical to those of bulk water. In the modern context, pore water should be considered in terms of its structuredness under the influence of the active centers of solid particles, ions, and other factors. The results of experimental studies on the effect of active centers of the solid surface, primarily clay particles, on the change in water structure via nuclear magnetic resonance relaxometers of various generations are presented. The patterns of changes in the structure of pore water in water-saturated clay soils of different granulometric and mineral compositions in the range of changes in their conditional physical state by moisture are shown. The structuredness of pore water in soils contributes to its inertness to the perception of external pressure and to the need to revise the concepts of filtration consolidation in favour of the rheological model for predicting the development of settlements as the main criterion for their stability.

An experimental study has been conducted on natural materials such as sandstone and andesite, which are commonly used in the mining, oil and gas industries, as well as in road construction. Cylindrical samples were tested under quasi-static and dynamic loads in fragment preservation conditions. X-ray tomography was used to determine the stages and mechanisms of destruction and the spread of cracks in the material before and after testing. The quasi-static uniaxial compression tests were performed, in which the deformation fields were measured, in situ, by using the digital image correlation method and acoustic emission signals. Analysis of the results revealed the specific features of fracture of andesite and sandstone samples. The destruction of andesite, which consists of hard and soft phases, follows a quasi-brittle scenario in the soft phase, with the size of the resulting fragments corresponding to the solid phase. When main vertical cracks spread throughout the entire volume of sandstone, which is a homogeneous material and consists of strong, loosely interconnected grains of sand, there was no sharp drop in its bearing capacity because friction forces between sand grains contribute significantly to holding them together, especially under compression conditions. Once the load was taken off, the sample broke up into pieces. The destruction of the tested samples subjected to quasi-static loading proceeds in two steps. The first step involves the accumulation of damages in the form of multiple main cracks coinciding with the direction of the maximum stress. During the second step, multiple daughter cracks are formed, which promotes the failure of the sample. In the case of dynamic compression, complete fragmentation of the sample occurred when the energy of the loading pulse was sufficient, and this was accompanied by the separation of the formed fragments. The results of this study are promising for the development of numerical fracture models intended to investigate the kinetics of defect nucleation and growth in rocks. These models can also be used to optimize the drilling processes.