Purpose is the development of mathematical models to evaluate deformation of parameters of the rock mass-well geological and engineering system within the anisotropic media. Methods. Both mathematical and neural modeling of a stress state of the rock mass-well system under conditions of geological uncertainty has been applied for the studies. From the viewpoint of mathematical modeling, analysis of probability of factors, complicating drilling, should involve a number of assumptions for strength and deformation characteristics of rock mass layers corresponding to particular hole-making conditions. Findings. A mathematical model of horizontal wellbore and geological layers, occurring along the structure under the conditions of permanent comprehensive stresses, has been developed. An analytical and graphical form has been applied to implement one of the basic aspects of aggregation principles of strength changes in each particular lithological layer for identification of an ideal value of horizontal/inclined wellbore length relative to the rock mass depths scheduled by mining. Regularities of changes in deformation and spatial well stability within the complex reservoirs depending upon various process duties have been determined. A neural simulation-based model has been proposed to analyze deformation of rock mass layers having different strength characteristics. Originality. Interaction between geomechanical characteristics of rock mass as well as deformation and spatial stability of well design has been evaluated both qualitatively and quantitatively. Practical implications. An opportunity has been presented to forecast deformation of well walls taking into consideration different strength as well as structural and geological rock mass characteristics on the basis of neural simulation. The represented approach has been included on the register of the best scientific-based practices according to “Methods to recover low-pressure gas of Cenomanian producing complex” Project.

Purpose is to substantiate design factors and technological parameters of next-generation facilities of hydromechanical drilling basing upon the determined features of interaction between breaking pellets and rock mass. Methods. The studies of directionality features and bottomhole processes for rock mass breaking have been carried out using the current analytical methods and laboratory experiments. Among other things, certain mathematical and physical simulation techniques, methods of theoretical processing and interpretation of the research results under SolidWorks, Statgraphics, and Маthсаd environments, and a number of relevant instruments and materials have been applied. Following their technological sequence, the well bottomhole rock-breaking processes were simulated using a special laboratory stand equipped with a control- and-measuring unit (inclusive of a flowmeter, manometer, tachometer, and coordinate spacer among other things). Findings. Application perspectiveness of the combined techniques for rock breaking has been proved. Structural designs of the next-generation facilities for well drilling have been proposed. The pellet-impact drilling features have been analyzed from the viewpoint of its significant dynamic component during the rock mass breaking. Nature of the effect of breaking load rate on the results of bottomhole deformation processes has been identified. Efficiency of the proposed scheme to improve pellet-impact drilling based upon maximum use of a well bottomhole deformed by pellets has been proved. Measures to increase technical and technological indicators of pellet drilling have been considered. Requirements for the conditions stabilizing operation of a collar of the pellet-impact device have been outlined. Further research tendencies have been specified. Originality. It has been determined that compliance with specific geometrical and hydromechanical ratios, corresponding to the stable mode of a well sinking, is the factor required for reliable operation of hydromechanical drilling facilities. Practical implications. The results of stand-based tests as well as analytical studies may become the foundations to develop efficient engineering decision for hydromechanical well drilling with high technical and economic indicators. The data, concerning bottomhole rock breaking processes, are the basic ones to work out rational standard parameters of well sinking processes.

Purpose. Improving the producing capacity and ensuring the stable operation of gas wells that develop unstable, lowcemented reservoirs by preventing the sand entry from the reservoir by means of creating the cement stone with the corresponding values of strength and permeability in the bottomhole formation zone. Methods. The technological characteristics of the cementing slurry and the formed cement stone are measured using standard recording equipment. The cementing slurry consistency is measured with a pycnometer, the cement mixture spread ability – using AzNII cone, water separation is measured according to standard methods (DSTU BV.2.7 – 86-99), and the time of the cementing slurry hardening is determined on a consistometer KTS-3. The ultimate parameters of the stone strength during bending are determined on a special device for testing linear objects in tension, and compression – on a PSU-10 hydraulic press. Findings. The cementing slurry composition for creating the cement stone with the corresponding values of compression strength and gas permeability in the bottomhole formation zone has been developed, which includes oilwell cement, expanded perlite, non-ionic surfactant, plasticizer and water. Dependences of the cement stone compression strength and the stone permeability coefficient on the proportion of expanded perlite in the cementing slurry solution have been revealed. It is recommended to use the proposed cementing slurry for creating a cement stone with specified values of compression strength and permeability in the expanded well shaft in the interval of the producing reservoir. Originality. The optimal proportion of the expanded perlite in the solution has been found, at which the corresponding values of the compression strength (up to 4 MPa) and gas permeability (up to 3.47 μm2) of the cement stone is provided. Practical implications. When using the developed composition, it is possible to increase the yield of wells with unstable reservoirs and improve their working conditions by preventing the sand entry from the reservoir into the well.

Purpose. Research and substantiating the expediency of cement mix formulations of grout slurries with different Defecate additive content and their effective use when cementing the reservoirs prone to absorption of the cement slurry, as well as to prevent behind-the-casing flows and for cementing operations in the zone of abnormal pressures (hydraulic seam fracturing). Methods. Analytical and experimental studies of the physical-chemical grout slurry properties are used: determining the influence of the Defecate additive content on the cement mixture technological properties; study of a change in the grout slurry rheological characteristics at various temperature conditions; testing the formulation of grout slurry with different rates of strength development; substantiating the economic efficiency of using the grout mixtures with the Defecate additive. Findings. It has been revealed that the cement mixture fluidity increases by 10-20% with the addition of a Defecate in the proportion of 5-20%. With a further increase in the Defecate content, the stone strength deteriorates, and with a decrease, the grout slurry concentration increases. It has been found that when Defecate is added to the cement mixture in a proportion of 20%, the pumpability of the cement slurry doubles, that is, from 1.5 to 3 hours. The economic efficiency has been proved of using these mixtures during insulating activities in the well No. 122 of the Kulychykhynske NHKR (oil and gas condensate field). The improved formulations of grout slurry with the addition of a Defecate are recommended to be used during repairinsulation works for delimitation of producing reservoirs prone to absorption, behind-the-casing flows and hydraulic fracturing. Originality. New dependences have been determined of the technological and rheological characteristics of grout slurries on the content of the Defecate additive, which makes it possible to set its optimal proportion. Practical implications. The use of grout mixture based on the Defecate will expand the raw material base for obtaining lightweight grout slurries. The properties of such a solution make it possible to use a grout mixture for cementing wells in the zone of abnormal pressures, while reducing the costs for the process of reservoir delimitation.

Purpose. The purpose of the research is to develop a mathematical model of the jet pump (JP) working process and a calculation methodology for modeling, as well as to determine the optimal operating modes of a combined pumping installation in downhole conditions. Methods. When conducting research, the coordinated operation of an electric-centrifugal pump (ECP), a jet pump and a reservoir is determined as the initial compulsory condition for the effective exploitation of extraction wells using a tandem pumping installation (TPI). Theoretical studies describing the joint operation of a jet pump and an electric-centrifugal pump were conducted, in the course of which mathematical modeling of the “productive reservoir – electric-centrifugal pump – jet pump” system operation in a coordinated mode was used. Specific data from the Khorasan-2 deposit (Republic of Kazakhstan) mines are accepted as the initial data during the modelling. When modelling the jet pump operating modes, special attention is paid to determining the boundary parameters of the pumped-out productive solution, at which cavitation can occur. The modelling is performed using the Maple software package from Waterloo Maple Inc. Findings. To assess the efficiency of pumping-out the productive uranium solutions from wells using tandem pumping installations, a mathematical model of the jet pump working process has been developed. On its basis, a calculation methodology for modeling the operating modes of a combined pumping installation with imitation of actual downhole conditions has been compiled. Originality. As a result of computational modeling, the high sensitivity of the cavitation modes of the jet pump operation to the design parameters of the jet pump main elements has been revealed, while the tandem installation itself as a whole has a lower sensitivity to changes in dynamic conditions. It has been substantiated that the use of a tandem pumping scheme for pumping-out a productive uranium solution can increase the productivity and energy efficiency of the process. Practical implications. The calculation methodology and algorithm make possible, with sufficient accuracy for practical use, to quickly calculate the required geometric parameters of the jet pump to ensure rational and cavitation-free modes of the tandem pumping installation depending on the specific downhole conditions in the “reservoir – electrical centrifugal pump – jet pump” system. In addition, it is possible to develop some practical recommendations for the design of jet pumps, working in tandem with submersible electric-centrifugal pumps.

Purpose. A methodology development for calculating the bottom hole assemblies (BHA) with two rock cutting tools for drilling the wells of large-diameter with an ability to manage the trajectory. Methods. A mathematical model has been developed for calculating the assemblies for drilling wells of large-diameter using two rock cutting tools – a bit and a reamer. The main technical and geological factors have been modelled, which influence the assembly elements (stress-strain state of the BHA, deflecting forces arising due to the rock influence). An algorithm for determining the distribution of axial load between the bit and the reamer has been developed. It has been modelled the formation of the reamer eсcentrical displacement relative to the pilot wellbore and the change in the intensity of the wellbore curvature in the process of deepening. Further on, a practical calculation according to the developed methodology is given. Findings. It has determined that an increase in the resource coefficient of cutting structure (that is, an increase in the total number of teeth on a bit, or a decrease in teeth on a reamer) leads to a decrease in the load on the bit. With an increase in the coefficient of destruction areas, the load on the bit decreases. It has been revealed that when drilling with assemblies, a significant influence on the stress-strain state of the BHA and on the change in deflecting forces, has an eccentricity on the reamer, while the intensity of the well curvature changes. It has been proven that the same assembly allows the well to be drilled with different curvature intensities, which can be adjusted by placing a restrictor under the reamer. Originality. A new comprehensive approach is proposed to the calculation of assemblies with two rock cutting tools, which is different in that it allows to perform an iterative cyclic calculation with constant refinement of the main parameters and the creation of a data set for constructing a well trajectory. Practical implications. The developed methodology for calculating the bottom hole assemblies with two rock cutting tools makes it possible to determine a rational design of the BHA for drilling a well in a specified direction by changing the design parameters of the drill collar (DC), supporting-centering elements (SCE), a bit, a reamer and an eccentricity restrictor.

Purpose. Substantiation of technological solutions for uranium mining by the method of In-Situ Leach Mining (ISL) under the conditions of the high groundwater pressure. Methods. Analysis of mining-and-geological conditions of the deposit, conducting experimental-industrial works at the experimental unit, and processing data from research results. To increase the efficiency and reduce the expenditures for in-situ leach mining of uranium, taking into account the hydrogeological peculiarities of the deposit, experimental works have been conducted using the “pumping wells” technology. Findings. The proposed technology helps to reduce the expenditures for acquiring cable products, submersible pumps (the cost of a more powerful pump is much less than the cost of several ones, which are equal to it in power), for the construction of well heads. The dependences have been obtained of the change in the uranium content in the pregnant solution and the recovery coefficient on the L:S ratio (liquid to solid) using the “pumping wells” technology. With a change in L:S from 0.1 to 0.33, the uranium content in the pregnant solution increases from 5 to 225 mg/l, then its gradual decrease is observed. A change in L:S from 0.9 to 2.2 leads to an insignificant change in the uranium content to 100-120 mg/l. Originality. Based on the research results, the dependences have been obtained of the change in the uranium content in the pregnant solution and the recovery coefficient on the ratio of L:S using the “pumping wells” technology. The recovery coefficient has changed in direct proportion to the L:S ratio, hence, for L:S from 0.1 to 2, the recovery coefficient increases from 1 to 87%. Practical implications. A new technology for uranium mining by the method of underground leaching has been developed, which is characterized by low capital expenditures and producing costs of in-situ leach mining of uranium.

Purpose is to substantiate and develop an efficient scheme of coalmine methane capture while preparing and developing gassy coal seams. Methods. Critical analysis of literature sources has been carried out; practice of applying the known schemes of coalmine methane capture for its further use has been systematized. Analysis and selection of theoretical substantiation of a new coalmine methane capture scheme have been performed taking into consideration the parameters of preparation and development of gassy coal seams. Methods of mathematical analysis have been applied to describe the dependence of gamma distribution of the continuous random variable of gas emission intensity on the distance to a stope. Findings. A scheme of coal mass degassing has been improved; that scheme helps increase degassing degree and eliminate colliery gas, including methane, in terms of specific arrangement of wells and introduction of new technological operations and parameters. The developed scheme takes into consideration physical and mathematical properties of rocks to increase the volume of produced gas along with the reduced total mining costs. Mathematical modeling has made it possible to define that the density function coincides maximally with the experimental and practical graph of dependence of gas emission intensity on the distance to a stope. Originality. Analytical dependences have been specified making it possible to evaluate rational range of the depth of degassing gas outlet wells and the distance between them according to the proposed scheme of their arrangement within the extraction pillar. Practical implications. The proposed scheme of coal mass degassing allows controlling coalmine methane extraction including special preparatory operations. It helps widen a range of effective application of the system for colliery gas extraction and reduce the time for preparatory degassing operations; that favours both rising stope output and the associated coalmine methane recovery with the corresponding increase in energy saving and safety during mining operations.

Purpose. Justification of magnetic field application in order to prevent formation of asphalt-resin-paraffin deposits (ARPD) in oil and gas equipment, and consider some current views on the state of ARPD problem in oilfield equipment and possible methods for its solution using magnetic treatment. Methods. Analysis and generalization of the research results of production fluid magnetic treatment using COMSOL Multiphysics software. Findings. The technology of magnetic fields application in prevention of asphalt-resin-paraffin deposits is introduced in the article. The obtained results of production fluid magnetic treatment make it possible to use it in oil wells equipped with pumping units, as well as in free flow production method or in wells operated by electric-centrifugal pump, and in oil pipelines. Originality. The use of high energy magnets based on rare earth materials can reduce asphalt-resin-paraffin deposits in oil equipment. Practical implications. The proposed magnetic treatment creates opportunities for field exploitation at the later stages of development which are characterized by a high content of asphaltenes, resins and paraffins. The results of production fluid magnetic treatment have proved the efficiency of this technology, which has doubled a turnaround time.

Purpose. The aim is to analyze the problem of preventing the asphalt-resin-paraffin deposits (ARPD) in the oil industry equipment and to justify application of paraffin control methods; to review modern approaches to ARPD problem and possible methods of its solution; to analyze existing methods of hydrocarbons ‘treatment by magnetic field. Methods. Investigations showed that application of magnetic anti-paraffin device (MAPD) makes it possible (during 24-hour operation of the oil well) to double the time between overhauls of oil wells equipped with sucker rod pump installations. Findings. The results obtained due to MAPD application in oil wells equipped with sucker rod pumps give an opportunity to use it in oilfield practice employing free-flow production method or in wells serviced by centrifugal pumps and in oil pipe lines. Originality. Application of up-to-date magnets with poles from 60 to160 kA/m enables to decrease ARPD in oil equipment. Practical implications. The results of MAPD implementation at Boryslav field, in particular in wells No 1343, 797, 948 proved the efficiency of the device application and doubled the overhaul period. Magnetic field effect on hydrocarbons is analyzed in the article.