Abstract
Purpose. To determine the mineralogical composition of colmatants formed during uranium in situ leaching at the North Kharasan, North Karamurun, and Irkol deposits of the Syrdarya uranium province and to evaluate their structural response to chemical decolmation treatments to substantiate deposit-specific approaches to well treatment. Methods. Colmatant samples collected from the inner surfaces of submersible pump assemblies in production wells were examined using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Quantitative phase composition was determined using a PANalytical X’Pert MPD PRO diffractometer. The samples were treated with two decolmation solutions: Solution 1 containing 10% HF and Solution 2 containing 5% HF, 10% H2SO4, and 1% surfactant. SEM observations were used to compare changes in surface morphology, crystal fragmentation, and formation of cavities and voids before and after treatment. Findings. Carbonate minerals constitute a major fraction of the studied colmatants, accounting for approximately 57% at North Kharasan, 29% at North Karamurun, and 45% at Irkol. North Kharasan is characterized by an ankerite-dominated assemblage, North Karamurun by a mixed carbonate-phosphate composition with a 51% phosphate fraction, and Irkol by a carbonate-rich assemblage containing 18% gypsum. Both decolmation solutions substantially disrupted the colmatant structure. The 10% HF solution generally caused more intensive local destruction, whereas the composite solution produced a comparable overall structural effect while reducing the HF concentration by half. For gypsum-rich colmatants, HF treatment may promote CaF2 precipitation, requiring sufficient pumping and subsequent flushing. Originality. The study integrates quantitative XRD characterization of operational colmatants with SEM-based assessment of their responses to two chemical treatments. It establishes a direct relationship between deposit-specific mineralogical composition and the selection of decolmatation approaches. Practical implications. The results provide a mineralogy-based framework for selecting effective decolmatation treatments at uranium ISL deposits. The composite 5% HF + 10% H2SO4 + 1% surfactant formulation can be considered for further field validation, while gypsum-rich systems require additional measures to prevent secondary colmatation caused by CaF2 precipitation.