GEOFILTRATION MODELING OF WATER FLOWS TO PRODUCED PRIMARY DIAMOND DEPOSITS AND INJECTION IN ASSOCIATED AREAS

Abstract

Safe development of primary diamond deposits in Western Yakutia requires constant monitoring of the hydrogeological regime of the exposed aquifer complexes within the quarry and mine fields of the deposits, as well as in the adjacent areas of drainage water injection. Over the entire period of development of the Alakit-Markhinsky, Daldynsky, Mirninsky and Nakynsky kimberlitic fields, about 400 million m3 of highly mineralized drainage water from quarries and mines were involved in the pumping-injection process. Complex cryohydrogeological conditions of the territory, i.e., lithological-facial specifics, continuous distribution of permafrost, structural confinement of kimberlite fields, fault-block structure of individual pipes, influence the dynamics of occurring changes and make the cryohydrogeological conditions of each individual pipe unique and having no complete analogues. In order to predict successfully and implement subsequently technical solutions aimed at controlling inflows of all types formed within mine and quarry fields, the Yakutniproalmaz Institute elaborated a program for the development, constant maintenance and updating of hydrogeological “digital twins” of all key mining deposits. The developed models take into account the influence of both natural factors and the applied schemes for opening and draining deposits, which impose their own limitations. The filtration problem was solved out using the licensed program FEFLOW, which performs modeling of hydrogeological conditions by the finite element method in a multilayer strata for areas of arbitrary configuration with boundary conditions of type I, II, III changing according to the known law in the presence of filtration heterogeneities in plan and section, as well as vertical filtration. The creation and constant updating of permanent digital models made it possible not only to acquire a modern tool for forecasting water inflows, but also helped to improve the planning process in terms of drilling drainage and injection wells, purchasing pumping equipment, etc. Deviation of predicted values from those actually observed within the short-term forecast for the period of use 2021–2023 ranged from 5 to 10%.