Introduction: The problems arising from backflow of proppant, rock particles and non-decom-posed liquid from hydraulic fractures are considered in the paper. The urgency of the research is caused by the necessity of improvement of well stimulation technology after hydrofracturing. The objective of the paper consists in the development of a set of devices for flushing perforation channels and wellbore walls in the perforation interval after hydrofracturing of a formation. Investigation tools and methods: When writing the paper, the methods of comparison and analysis of national and foreign references in petroleum engineering, patents related to application of formation hydrofracturing were used. Results and discussion: The urgency of developing a device for lushing out of perforated intervals is revealed and substantiated. It is shown that solidified viscoelastic particles of gel enter perforation tunnels and stick to their walls and to the wall of a well. Later these zones of gel particles deposits decrease permeability in perforation tunnels. On the basis of the investigations, the author developed a device for well bottomhole clea-nout that reduces stimulation period for the wells with the above described problems arising after hydrofracturing. To increase productivity of such wells it is necessary to lush out them applying the developed device in the mode of the closest approach to the deposition zones. For better particles lifting to the surface, it is proposed to use foam systems produced by a jet pump which is described in the paper. Conclusion. The set of devices for flushing perforation channels and wellbore walls in the perforation interval which allow for multiple decrease of well stimulation period after hydrofracturing is developed. The described devices are protected by the patents of the Russian Federation: patent for invention No 2651869 "A device for clea-nout", application for patent No 2017109500; patent for invention No 2643882 "Jet pump", application for patent No 2017114222.

Introduction: urgency of this work lies in the need to solve problems of gas-lift optimization in regime of minimum specific gas consumption for oil and gas industry. Optimization of gaslift wells operation and redistribution of injected gas allow more rational use of gas resources and significantly increase production at fields of JV «Vietsovpetro». parameters of operation for artificial gas-lift wells, a list of complications in operation of low-yield wells were used. Materials and Methods: Results: the design features of well that influence operation of artificial gas-lift are determined. A number of faults in gas-lift operation are revealed. The methods for increasing efficiency of gas-lift are substantiated. Discussion and Conclusion: the author analyzed causes of the malfunction in gas-lift operation, proposed measures to eliminate them. The analysis of measures to increase the efficiency of gas-lift wells was carried out.

Introduction: the relevance of the study is due to the need to identify the role of the lithogenous basis of the landscapes of the Greater Caucasus in the formation of their geo-chemical features and patterns of migration and concentration of chemical elements in various landscape and geochemical conditions. The purpose of the article is to study the specific geochemical differentiation of near-surface (soil-forming) sediments of the landscapes of the Greater Caucasus. Materials and methods: a method was used to compare the chemical composition of the main soil-forming complexes of the physico-geographical subregions of the northern slopes of the Greater Caucasus with a regional lithogeochemical background. Results: Geochemical differentiation of soil-forming rock complexes was revealed for the physico-geographical subregions of the northern slopes of the Greater Caucasus, which are allocated in the physico-geographical zoning of the territory. Areas of distribution of individual complexes of soil-forming rocks are considered as litho-geochemical fields of regional geosystems. Based on the calculation of regional concentration coefficients for lithogeochemical fields, the above and below-back-ground associations of chemical elements were distinguished relative to the regional lithogeochemical background, for which the average content of chemical elements in the soil-forming complexes of the North Caucasus was adopted. Discussion and conclusion: the authors concluded that the formation of geochemical features of surface soil-forming complexes of sediments in the landscapes of the northern slopes of the Greater Caucasus was greatly influenced by long-term weathering processes during the orogenic stage of the region's development in the Late Cenozoic. The practical signiicance of the results obtained is to determine the basic information on the lithogenic basis of the landscapes of the Greater Caucasus, which is necessary for sound geoecological monitoring.

Central Ciscaucasia is experiencing significant anthropogenic loads from the XIX century. About 90% of the territory of the Stavropol Territory is used for agricultural needs, which has a significant impact on the inhabitants of the soil. An important component of the soil fauna are representatives by the Diplopoda and Chilopoda. In the given work the analysis of habitat preference of these arthropods to native and anthropogenic biotopes is analyzed to assess the impact of human activity on members of these groups. The material for the present work was collected from 2004-2017 in the native and anthropogenic biocenoses of the Central Ciscaucasia. Specimens were taken either by hand or using soil sampling. In total, more than 3 thousand Diplopoda and Chilopoda were collected and processed. A total of 55 species were identified in the study area. The largest species diversity in the natural gully and floodplain forests (45 species). The fauna of the steppes is less rich (25). In this case, a decrease in species diversity is observed in various steppe biotopes with a decrease in humidity (up to 5 species in sagebrush steppes). The study area has undergone a significant anthropogenic transformation. Only 6 species of millipedes were found on the ield. Field-protecting forest belts are the richest species between anthropogenic biocenosis. They served as a refugium for the natural steppe fauna and "corridors" for spreading of some forest species. In the gardens there are 9 species of Chilopoda and 4 - Diplopoda. The gardens and urbocenosis characterized by the presence of anthropochoric species. The greatest variety of Diplopoda and Chilopoda (82% of species) is observed in forest biotopes, which occupy about 1.5% of the area under study. Reduction of species composition of the Myriapoda in the steppes is connected with a decreasion in soil moisture. This trend is also observed among the steppes of various types: 25 species in mixed-grass, 12 species in fescue feather grass and 5 in sagebrush steppes. In sagebrush steppes millipedes are completely absent. Scolopendra cingulata is the only species conined to steppe biotopes only. Anthropogenic transformation of natural biotopes adversely affects the diversity of millipedes. The greatest damage is caused by plowing of the land: in the fields there are only two types of diplopods and 4 - chilopods, 13 species of millipedes are found in gardens, 20 in urban areas. The creation of ield-protecting forest belts has played a certain positive role. They contribute to the preservation of elements of the native fauna of the Central Ciscaucasia.

Introduction: Caucasian Mineral Waters (KMV) - one of the oldest resort regions of Russia, on the territory of which are concentrated a variety of recreational resources and operate various types of recreational activities. A variety of recreational resources of Caucasian Mineral Waters are of interest not only from an economic point of view, it is important to explore them in the historical aspect. The historical approach allows us to study the history and features of the development of scientific ideas about the nature of the development of climate as a recreational resource of Caucasian Mineral Waters. The analysis of historical sources contributed to the identiication of factors in the study of climate as a recreational resource, and to determine the contribution of individual scientists to the study of climate in the region. Summarized scientific works of scientists and doctors, working in the region Caucasian Mineral Waters in the late XIX - early XX centuries. Along with the study of hydromineral resources in the study period in the Caucasian Mineral Waters begins an active study of climatic conditions in terms of their use for medicinal purposes. A number of scientific works devoted to the characteristics of the therapeutic value of climate are analyzed. The work of researchers involved in the analysis of the influence of climate in the region of Caucasian Mineral Waters or individual resort cities on the human body. The importance of the works of members of the Russian Balneological Society in the study of climate as a therapeutic factor, as well as their contribution to the development of climate treatment in the Caucasian Mineral Waters. In the XIX century, as a result of meteorological studies, the first scientific works on the climatic conditions of the Caucasian Mineral Waters appeared and the climate of the region acquired great importance for medicinal purposes. Due to researches of climatic factors of the resort region since 1910 Kislovodsk as the resort began to function and in the winter period. Materials and methods: Research result: Discussion and conclusions:

Introduction: Karachay-Cherkessia is a type of regions in which there is an active change in the ethnic structure of the population. Over the past 50 years, there have been changes in proportions in the ethnic structure of the region's population, as well as changes in the geography of the resettlement of the titular ethnic groups of the republic. The purpose of the study is to conduct a comparative analysis of the resettlement of titular ethnic groups in Karachaevo-Cherkessia in the second half of the XX century and at the beginning of the 21st century. Materials and methods of research: author's GIS: "Mountainous settlement of the North Caucasus" and "Atlas Information System" Settlement of Peoples in Russia "were used. Cartographic methods and methods are applied as well as the method of statistical analysis, the Comparative method. The multiscale approach is the key, allowed to study the ethnic structure in general in the republic and at the level of individual municipalities. The results of the research and their discussion: the work details the resettlement of 5 titular ethnic groups of the Republic of Karachaevo-Cherkessia: Abazin, Karachais, Nogais, Russians, Circassians. The analysis is presented for the periods: Soviet from 1959 to 1989 and post-Soviet from 1989 to 2010. A significant place is given to the peculiarities of changing ethnic proportions at the level of municipal districts, as well as events and processes that to varying degrees contributed to a change in the ethnic structure of the population of the republic. The authors consider the features of the involvement of the titular ethnic groups of Karachay-Cherkessia in urbanization processes. The main conclusions and discussion: the authors made a number of conclusions, including that the ethnic structure of the population, and with it the geography of the settlement of ethnic groups in Karachaevo-Cherkessia during the second half of the XXth century beginning of the 21st century, changed under the influence of the growth (reduction) in the number of individual ethnic groups. The growth in numbers was due to active demographic processes, primarily among the Karachais, and to a lesser extent the Abazin, Circassians, and Nogais, against this background active migration processes - the departure of Russians outside the republic in the post-Soviet period inluenced their decline in numbers. Karachaevtsy quite actively expanded their settlement area, primarily due to the municipal districts, the compact residence of Russians. Circassians, Abazins and Nogais practically do not expand their settlement area; in the post-Soviet period, the Abazin and Nogai people have an increased concentration of populations in the settlements that make up the traditional area of their resettlement. At the present stage there is an active involvement of the titular ethnoses of the republic in urbanization processes.

Introduction: A risk-based approach can significantly reduce the total number of inspections, their planning, ranking by the degree of risk. Materials and methods of research: when developing methodological methods for assessing land plots, the criteria for classifying the activities of economic entities were taken into account. To identify land plots, the publicly available remote sensing data of the Earth was used. The generated database contains the coordinates of the cetroids of the land parcels and the risk category. Based on the created cartographic materials, an analysis of the effectiveness of the application of the risk-based approach for the assessment of agricultural land is made. Results and discussion: Based on the proposed methodology for applying the risk-based approach, the land plots located in the Ipatovsky, Arzgirsky, Blagodnenskoye, Trunovsky, Aleksandrovsky, Izobilnensky, Georgievsky, Kursk districts, as well as most of the Grachevsky and Andropov districts, will be checked only on applications from citizens and in the event of a threat to the life and health of people. Mapping of land subject to checks with the data of administrative violations of the land legislation in the period from 2015 to 2017 has identified municipal areas, where the rates of offences had values above medium-range, but the planned inspection of land will not be carried out, namely in the following areas: Ipatovskiy, Blagodarnenskiy and Novoseletskiy. Spatial analysis of the location of land areas subject to inspections in municipal areas with the maximum share of offenses identified only four land plots in the Turkmen district, the lack of audited sites in the western part of the Kochubeevskiy district, the northwestern part of the Novoaleksandrovskiy district, the southern part of the Predgorniy district, and the western and southern parts of the Krasnogvardeyskiy district. spatial analysis showed weak effectiveness of the risk-based approach without taking into account regional characteristics, possible threats to sustainable development of land use and protection of agricultural land in the Stavropol region.

Introduction: the article raises the current complex problem of environmental pollution with technogene waste and its component - the search for effective methods of wastewater treatment from oil and its products. The authors propose to use the perspective of sorption technology. The range of sorption materials from year to year is steadily expanding, however the deterrent factors of their widespread introduction are the high cost, not always optimal performance, environmental safety of disposal of saturated absorbers. The article assesses the prospects of using sorbents based on plant waste for wastewater purification from oil pollution. A clear understanding of the physico-chemical and mechanical properties of the raw materials is a necessary condition for determining the rational ways of their processing. Thermal modification of raw materials allows giving the sorbents the performance characteristics required for a particular type of pollution. The aim of the work was to study the influence of sorbent production conditions on their ability to purify water from oil pollution. Materials and methods of research: the raw material for the research was sunflower husk subjected to carbonization in oxygen-free conditions. The methods of thermal analysis, scanning electron microscopy, low-temperature nitrogen adsorption were used. For the assessment of operational properties of sorbents thermomodification applied weighting methods. Research results and discussion: the thermogram of decomposition of sunflower husk, giving an idea of the features of the thermal decomposition of plant waste in the range of 150-700 °С. The values of yield, buoyancy, oil and water adsorption of sorbents, worked out in the temperature range from 200 to 600 °С, determined the value of their surface , the features of the porous structure, allowing to consider the optimal carbonation at 300400 °С. Conclusions: the porous structure of sorbents has a direct impact on their performance properties. Large-scale absorbers are necessary for effective treatment of waste water from oil pollution. Carbonation of plant raw materials leads to an increase in the sorption surface, its hydrophobization. The practical significance of the perspective of the use of sorbents on the basis of wastes for purification of wastewater from different types of pollutants.

Introduction: the article gives a brief review of methods of affecting hailing used in production processes on agricultural crops protection from hail damage. Materials and Methods: combined method, the methods of competition and acceleration of sludging in the range of hail growth area and future hail formation of hail-hazardous and hail clouds, the method of hail breaking on the approach lane of the protected area from the direction of hail clouds invasion and the method of hail breaking on the protected areas of the Central Caucasus region. They differ from each other in scientific conceptions and criteria of seeding, technical means and seeding techniques, reagent consumption, the quality of seeding conception realization and evaluation methods of the impact eficiency. Results: the analysis of long-standing observations on affecting hail processes has revealed that the protection of agricultural crops from hail damage is successful. Nevertheless, there are some cases of considerable hail damage to agricultural crops on the protected areas of the region under research. The main causes of hailing are organizing and technical, insufficient research of hail processes, low ice formation efficiency of the utilized crystal reagent particles of argentum iodide, the lack of new criteria for recognizing and schemes of hail-hazardous and hail clouds. Discussion and conclusions: many of the above problems are practically solved in the author's works, which are protected by the patent [6] and are successfully applied in the anti-hail protection of the military services of the Stavropol Territory.

Introduction: Many important aspects of microphysical processes in hail clouds are still poorly understood due to the complexity of theoretical analysis and experimental research. The interaction of thermodynamic and microphysical processes in powerful convective clouds, electrical processes, interaction of the reagent with the cloud environment is not sufficiently studied. The relevance of the study is due to the need to develop scientifically valid methods of active impact to hail clouds. Materials and methods of research: The paper used a three-dimensional model of powerful convective clouds with a detailed description of thermodynamic, microphysical and electrical processes. The solution of the model equations was performed by a finite-difference method according to an implicit scheme of second-order accuracy with respect to spatial coordinates and time. When specifying the fields of the thermodynamic parameters of the atmosphere at the initial time, aer-ological sounding data or three-dimensional data from the global prediction model GFS were used. Results of the research and their discussion: The results of numerical experiments on the interaction of physical processes in high-power convective clouds show that an important consequence of the deformation of the fields of the thermodynamic characteristics of a cloud under the influence of ascending flows is an increase in the time of finding hailstones (or their path) in an area in which thermodynamic and micro-physical conditions are favorable for their growth. A study was made of the change in the microstructural characteristics of the cloud from the concentration of artiicial crystals and from the place of their application when the hail cloud was seeded with a crystallizing reagent. It is received that in the ield of inluence the radar relectivity decreases due to the appearance of many crystals, because of the induced supercooled droplets caused by the artiicial crystallization. Conclusions: Numerical experiments have shown the important role of interaction of processes of various types in the formation of the microstructure of clouds, in particular, in the formation and growth of hail particles. The most effective from the point of view of using the crystallizing reagent to reduce the danger of the cloud is to introduce it into a limited area, found as a result of numerical experiments. The effect of the crystallizing reagent on the microstructural parameters of the cloud as a result of seeding is determined.

Introduction: the relevance of the study is due to the lack of justification of system-wide laws and principles from a unified position within the framework of the traditional set theory of systems, on the basis of which existing methodologies of analysis and synthesis of systems are constructed. Research methods: the results obtained within the framework of this article are a continuation of the research work on the creation of a formalized theory of simulation modeling of processes and systems. Earlier, the authors developed formal bases for the calculation of functional objects using the Abad-Kardeli calculus. There were introduced such terms as: stream and node objects. The formal foundations of the states of flow and core objects, as well as their interrelations, are determined. In addition to implementing the procedures for synthesis and analysis of systems, the results obtained opened the prospects for formalized accounting in system-object models of system-wide principles and regularities. In work with the above-mentioned calculation of Abadi-Kardeli objects, the deinition of the system within the system-object approach "Node-Function-Object" is clarified, and a formalization of the concepts "system-forming factor" and "system adaptation" is proposed. Results of the study and their discussion: the presented formalisms were used to take into account system-wide regularities in the construction of graphoanalytical models of organizational-business and industrial-technological processes in terms of "Node-Function-Object". The described approach makes it possible to distribute known system-wide regularities into three groups: related to the structural properties of systems related to their functional properties and to substantial properties, which justi-ies the hierarchical dependence between them. Formally, it is shown that the principle of organizational continuity is fulilled only if the principle of mono-centrism is observed, understood broadly. The possibilities of system-object, system-structural, object-oriented approaches and BPMN notation to consider system-wide regularities in graphoanalytical models are investigated. Conclusions: the authors concluded that the system-object approach "Node-Function-Object" allows to take into account from one position the existing system-wide laws and principles to a greater extent than other approaches. That, in turn, opens up new prospects for simulation of processes and systems, namely: the processes of adaptation and evolution of systems.

Introduction: the problem of integrability of nonlinear partial differential equations, even for the second order, is not always an obvious fact, since inding a general solution is possible only in rare cases. The proof of integrability can be justiied in many ways: by obtaining a large number of particular solutions, reducing to some exactly solvable reduction, and also constructing an infinite number of first integrals. Materials and methods of research: methods of the theory of solitons for equations possessing a Lax pair were used. To construct the conservation laws, we use the equation of isospectral deformation with a self-adjoint differential Dirac operator of the first and second kind. Under the condition that the functions occurring in the coeficients have a rapidly decreasing nature, the solution is represented in the form of a series expounded in negative powers of the spectral parameter. Results of the study: Eigenvalue equations with Dirac operators of the irst and second kind are investigated. A countable number of first integrals is found. Examples of nonlinear partial differential equations obtained with the help of an operator equation of zero curvature are given for which the scattering operator coincides with the Dirac operator. It is proved that such equations have a countable number of irst integrals. Discussion and conclusion: the author concluded that among the conservation laws obtained there is a Hamiltonian, all integrals of the motion are in involution with respect to the Poisson brackets. This suggests that nonlinear partial differential equations are Hamiltonian, which leads to their complete integrability.

Introduction: most of the differential equations associated with soliton mathematics are obtained using the Lax operator equation or the zero-curvature equation, which are the compatibility condition for a pair of linear differential systems. The case in which second-order systems were used to obtain such equations was studied in depth and comprehensively. Increasing the order of systems leads to highly overdetermined conditions. The possibility of using third-order linear systems is being studied. Materials and methods of research: methods for constructing partial differential equations using the Lax operator equation with differential operators of the first order and matrix coefficients of 3 x 3 were used. Research results: necessary and suficient conditions imposed on the parameters and func- Discussion and conclusions: tions included in the matrix coefficients, under which the commutator of two differential operators represents the multiplication operator. It is shown that the Lax equation reduces to a system of nine equations, the order of which can be reduced and reduced to one nonlinear partial differential equation. the authors demonstrated two examples of the derivation of nonlinear equations and the determination of their Lax pair. In the irst example, the main differential coeficient is considered as a lower triangular matrix, and in the second case the constant matrix has a diagonal form. As a result, second-order equations with a logarithmic nonlinearity are obtained.

Introduction: the methods of representation of functions given approximately by their singular integrals in relation to approximation problems and numerical methods for solving boundary value problems for differential equations are Investigated. In such a statement, the problem belongs to the class of ill-posed problems and requires the construction of appropriate regularizing methods and algorithms for its solution. Materials and methods of research: the questions of approximation of the function under study by generalized polynomials are Considered and some important properties of this computational process are investigated. The question of the extent to which the members of the approximating sequences represented by generalized polynomials "inherit" the analytical properties of the approximated functions is investigated. The nature and conditions of convergence of approximating sequences to the original function are investigated. Examples of application of the function approximation apparatus by generalized polynomials are given, calculation formulas of the computational algorithm are derived. Research results and their discussion: the results of theoretical studies obtained in the framework of this work are of independent importance in the field of computational mathematics. The practical significance of the results is that the proposed methods and approaches can be used in applied problems of the theory of approximation of functions, problems of applied analysis and boundary value problems of mathematical physics, using approximately given initial data obtained in the course of physical experiments or empirical functions.

Introduction: the relevance of the study is due to the fact that the effects of localization of excitations near the interfaces of nonlinear media play an important role in various technical applications of solid-state and opto-electronics. The aim of the paper is to find the solutions of the nonlinear Schrodinger equation and the energy levels of stationary localized near the defect states in the framework of the model, which is a generalization of models of two-level systems. Materials and methods: methods of theoretical physics of solids and nonlinear dynamics based on traditional methods of mathematical physics are used to investigate the localization energy of excitations in nonlinear media with defects. Results and discussion: The model generalized of the model excitation interacting on a defect with two branches of the dispersion law to the case of a nonlinear medium is presented in the article. The model is based on the nonlinear Schrodinger equations. Nonlinear Schrodinger equations describe the dynamics of excitations in nonlinear media of the Kerr type. The problems of the existence of different types of soliton states in a two-level system with different parameters of the dispersion law are considered. Solutions of the nonlinear Schrodinger equations with positive and negative anharmonicity in the focusing and defocusing media separated by a planar defect with Kerr nonlin-earity are obtained and analyzed. Conclusions: It is shown that in the system under consideration there exist nonlinear localized states of several types, which are related soliton solutions of asymmetric proiles. The energies of bound on defect soliton states are determined for cases of positive and negative nonlinearity of the medium. Conditions for the existence of such coupled soliton states are derived. In limiting cases, characterized by the degree of proximity to the edge of the lower boundary of the branch of the continuous spectrum, the energy levels are obtained in an explicit analytical form. The states considered in this paper describe the damping of the ield, both symmetric and asymmetric with respect to the interface of the media when moving away from it. The existence of bound soli-ton states is important to develop of quantum systems based on the properties of nonlinear surface waves in layered structures. Systems of such a type possess a wide range of important physical applications in nonlinear dynamics of a solid body and in nonlinear optics in the development of devices using nonlinear photonic crystals and periodic waveguide structures.

Introduction: a method for measuring the frequency of the formation of vapor bubbles in the boiling of opaque fluids using a two-layer system is proposed and implemented: an opaque - transparent medium. An experimental setup has been developed and experiments have been carried out to determine the frequency of the formation of vapor bubbles during the boiling of opaque liquids. Materials and methods: A method for measuring the frequency of formation of vapor bubbles in the boiling of opaque liquids by means of a two-layer system is proposed and implemented: an opaque - transparent medium. An experimental setup has been developed and experiments have been carried out to determine the frequency of the formation of vapor bubbles during the boiling of opaque liquids. The results of the study: The frequency of formation of vapor bubbles was measured in the boiling of a two-layer medium by a non-magnetic liquid on an unrestricted horizontal surface with pointwise heat input in a uniform external magnetic field. It is found that with the increase in the strength of a uniform constant magnetic field, the frequency of the formation of vapor bubbles upon boiling of a two-layer medium of a magnetic-nonmagnetic liquid on an unbounded horizontal plate decreases, and the temperature of the heat-releasing surface at which the vaporization process begins increases for samples of magnetic liquids with a high magnetic phase content. Discussion and conclusions: The dependence of the frequency of the formation of vapor bubbles on the temperature of the heat-releasing surface is found experimentally at the boiling of a magnetic fluid in various magnetic fields with different intensities and directions. It is found that with the increase in the strength of a uniform constant magnetic field, the frequency of the formation of vapor bubbles upon boiling of a two-layer medium of a magnetic-non-magnetic liquid on an unbounded horizontal plate decreases, and the temperature of the heat-releasing surface at which the vaporization process begins increases for samples of magnetic liquids with a high magnetic phase content.