Recycling of drainage brines by means of re-injection in Udachny Mine

Abstract

The permafrost zone in Levoberezhny 2 Site, represented by the Upper Cambrian carbonate–terrigenous rock strata up to 270 m thick, is studied. It is found that during injection, brines first flow along fractures and pores, and dissolve ice fill in them. The permafrost rocks degenerate as a result, and extra porosity is generated together with formation of a manmade aquifer. The analytical flow model of brine disposal in permafrost rocks in Udachny Mine represents the analytical flow model in dry soil, with rock permeability varied from zero to maximum values to describe frozen and thawed zones. The hydrogeological research of permeation by the numerical modeling method used GMS MODFLOW environment. The key complexity of the permeation problem consists in the fact that permeability coefficient and storage capacity of permafrost rocks greatly increase with time of injection. The highest degradation of ice takes place in the injection site; brines are displaced deeper in rock mass at the front velocity governed by density of joints, ice content, injection flow rate, mineralization of brines, temperature of rock mass and brines, etc. The permeation problem was solved using the method of alternation of quasi-stationary states in conformity with the modern hydrogeology and frost in the permafrost rock mass, and in accord with experience of drainage brine re-injection in Udachny Mine, subject to the key requirement of free flow of drainage brine into the permafrost rock zone at the eliminated discharge of water into local stream flows.