The features occurring during borehole uranium mining in deposits with low filtration characteristics, as well as the conditions and reasons for the reduction of geotechnological parameters of uranium mining by the well are considered in this study. Core material samples were taken from the productive horizon of the Chu-Sarysui province deposit and granulometric compositions were established. The contents of uranium, aluminum, calcium, magnesium, iron and carbonate minerals in the samples were determined by atomic emission spectroscopy. The X-ray phase analysis method established the features and quantitative and qualitative characteristics of ore-containing minerals. A special technique has been developed for conducting experiments in laboratory conditions using core samples, where the intensity of uranium leaching in tubes is determined. The results of laboratory studies are analyzed and discussed and graphs are constructed, to show the dependencies of change in: the filtration coefficients of K_f; the uranium content in solution; the extraction coefficient; and the specific consumption of sulfuric acid on the values of L:S (the ratio of liquid to solid) in the experiments. The effectiveness of using a mild acidity regime, with the addition of oxygen as an oxidizer, is determined and shown. The values of the uranium content in the productive solution, with the addition of oxygen as an oxidizer, reached 220 mg/L, which exceeds the design parameters. The results of uranium extraction from ore show a positive trend, reaching 68%, with L:S from 1.7 to 3.0, low acidity values and the addition of oxygen as an oxidizer. The specific consumption of sulfuric acid reaches the minimum values when using leaching solutions with reduced acidity of 26 kg/kg. The obtained results, on the flow rate of the solution in the tube, the extraction of uranium from ore and the specific consumption of sulfuric acid, indicate a decrease in sedimentation in a porous medium and increased filtration characteristics, with reduced acidity values in the leaching solution.

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The features of uranium mining on Kazakhstan’s enterprises have been examined, and uranium deposits located in the Syrdarya and Shu-Sarysu depressions have been described. Actual and projected data on the development of technological blocks in areas with complex geological structures have been analyzed and compared. Core samples were collected and, using X-ray diffraction analysis, quantitative and qualitative characteristics as well as mineral compositions of ores from various productive horizons of uranium deposits in the Syrdarya and Shu-Sarysu depressions were comparatively analyzed. It was determined that the ores in the Syrdarya depression are relatively homogeneous compared to those in the Shu-Sarysu depression, although in some places, clay minerals and gypsum are present, which hinder the uranium leaching processes. In the ores of the Shu-Sarysu depression, clay minerals that impede the uranium leaching processes are present in certain areas. Microscopic analysis of core material samples using a LEICA DM 2500 P microscope revealed particle sizes and shapes, as well as their distribution within the structure of host rocks in the productive horizon. Using X-ray diffraction analysis, mineral compositions of sediment-forming components during uranium well mining in the considered productive horizons were determined and comparatively analyzed. It was established that in the geotechnological wells of the Syrdarya depression, sediments of predominantly chemical origin, such as gypsum, are formed. However, in the geotechnological wells of the Shu-Sarysu depression, sediments of mechanical origin, consisting predominantly of quartz particles and clay minerals, are formed. Based on the obtained data, a method for intensifying underground uranium leaching in complex geological conditions has been developed, which involves dissolving sediment formations and increasing the oxidative–reductive potential of the leaching solution. The proposed and experimentally substantiated universal methodology for enhancing uranium well production involves the dissolution and prevention of precipitation using hydrofluoric acid solutions, as well as the oxidation of uranium dioxide with hydrogen peroxide.

Purpose. Improving the efficiency of borehole uranium mining and the selection of special decolmating solutions to improve the filtration characteristics of the seam due to effective destruction, as well as by preventing the sedimentation in the productive horizon, depending on the mineralogical composition and structure of sediment-forming materials. Methods. The advantages and disadvantages of the main methods used for improving the filtration characteristics of the productive horizon, when mining the uranium deposits by the borehole method, have been studied. Samples of sedimentation from the productive horizon are taken at the uranium deposit of the Shu-Syrasu depression. The quantitative and qualitative parameters, as well as the peculiarities of the mineral compositions have been determined by the X-ray phase method. A methodology has been developed and laboratory experiments have been conducted on the treatment of sedimentation samples by the drop method using various compositions of selected decolmating solutions. The microscopic method is used to determine the structure and peculiarities of sedimentation before and after treatment with various decolmating solutions. Findings. The effectiveness of the main methods used to improve the filtration characteristics of seams in the uranium deposits, mined by the borehole method, has been determined. The structure and composition of sedimentation, which causes a decrease in the filtration characteristics of the productive horizon, have been determined. To destroy and prevent the sedimentation in the productive horizon, an effective composition of a special decolmating solution using ammonium hydrogen fluoride with the addition of sulphuric acid and surfactants has been selected. An effective method for increasing the filtration characteristics of the productive horizon with the use of special decolmating solutions has been developed and scientifically substantiated. Originality. The use of special decolmating solutions based on ammonium hydrogen fluoride with the addition of sulphuric acid and surfactants according to the developed methodology allows to effectively destroy and prevent sedimentation in the productive horizon of borehole uranium ore mining. Practical implications. The use of the developed decolmating solution and a special methodology for the intensification of borehole uranium mining can reduce the operating costs of its production. This increases the ecological and industrial safety of the work to intensify the leaching of uranium ores.

Purpose. The research purpose is to increase the efficiency of borehole uranium mining by selecting special decolmating solutions and rational parameters of the technology for influencing the seam near-filter zone of geotechnological boreholes, as well as improving the filtration characteristics of the seam, depending on the mineralogical composition of ores and the structure of sediment-forming materials. Methods. The method of X-ray phase analysis was used to study the powders. The core material samples were studied on transparent sections using a LEICA DM 2500 P microscope. The content of the elemental composition of the ores and host rocks in the samples of the productive horizon was controlled using an atomic emission spectrometer. Findings. Based on the research results, quantitative-qualitative characteristics of the host rocks in the productive horizon, sedimentary formations from technological boreholes have been determined, revealing various levels in the productive horizon. It has been found that in the Campanian horizon boreholes, ores have a complex structure and multicomponent sedimentary formations, representing a mixture of sediments of mechanical-chemical origin. Originality. The results of quantitative-qualitative, microscopic, thermal research methods of the characteristics of ore-bearing rocks from various horizons at the Syr Darya depression uranium deposit have been studied and comparatively analyzed. The sedimentary formations of technological boreholes in the productive Santonian, Maastrichtian, Campanian horizons of the Northern Kharasan field, Syr Darya depression, have also been sampled and studied. The choice of the most appropriate composition of chemical reagents for dissolution and prevention of sedimentary formation in porous media has been substan-tiated by the microscopic research method. Practical implications. A detailed study and comparative analysis of the characteristics of ores and host rocks in various productive horizons makes it possible to more accurately plan the mining of blocks, minimizing emerging risks. Using the developed combined technology for intensifying borehole uranium mining, it is possible to increase the efficiency of borehole uranium mining and reduce its operating costs. At the same time, the ecological and industrial safety of the work of intensi-fying the leaching uranium ores increases.