Changes in the hydrodynamic regime of the Tolbachany aquifer during mining of the Mir kimberlite pipe

Abstract

Introduction: The development of many types of solid minerals during the opening of pressure aquifers is carried out under the protection of the formation of a depression curve resulting from advanced water drawdown. The study of changes in the hydrodynamic regime of aquifers as a result of technogenic impact is important for areas with already developed or developing extractive and mining industries. The Lower Cambrian Tolbachany aquifer, after the resumption of mining operations at the Mir primary deposit, in the range from 925 to 1600 m from the day surface will form about 60% of the inflow of natural saturated (up to 520 g/l) calcium chloride brines. The initial reservoir pressure in the reservoirs of the Tolbachany suite reaches 150 kgf/cm2 , which is 1000 m of top pressure. Therefore, to ensure safe conditions for mining the production blocks of the deposit, advanced water drawdown will be required. Technogenic impact will certainly lead to the formation of a funnel of desiccation and will affect the hydrodynamic regime of the complex. Methods: For the investigation of the hydrodynamic regime of the Tolbachany aquifer within the mine field, the generally accepted methods used in studying the dynamics of groundwater were used. The construction of a hydrogeological model was based on the determination of reservoir filtration parameters over the past 5 years. The forecast of changes in the hydrodynamic regime was carried out after the calibration of the constructed model using the hydrogeological modelling program (Modflow software). Results and discussion: The result of the study was the characteristic of the hydrodynamic regime of the Tolbachany aquifer. Schematic maps of pressure distribution in case of resumption of mining operations and associated advanced drainage were presented. Changes in the hydrogeological conditions of the complex may have an impact on adjacent subsoil areas. By the end of the period of modelling the operation of the advanced water drawdown system, the radius of the funnel of desiccation will be about 2000 m. Conclusions: The conducted work allowed studying changes in the level regime of the Tolbachany aquifer. The features of the formation of funnel of desiccation that occur during the development of the Mir deposit in the reservoir interval of the Tolbachany suite were determined. The predicted hydrodynamic parameters will lead to the formation of a limited funnel of desiccation, which will be a moderate technogenic impact on the subsoil.