Abstract
The issues are considered related to gas manifestations during the development of primary diamond deposits in Yakutia — «Internatsionalnaya» and «Udachnaya» pipes, which are the most difficult in terms of gas-dynamic conditions. Gas manifestations at the field are associated to a greater extent with gases dissolved in the natural brines, and to a lesser extent — with free and sorbed gases. Due to the fact that when developing the underground mines, the sources of explosive gases were recorded, to ensure the safe conduct of mining operations it is required to unload the rock mass. Analysis of data obtained at the different stages of construction and operation of the fields identified the source of the recorded gas manifestations: reservoirs and local gas reservoirs filled with gas-saturated brines. It was revealed that the sources of gas release are zones consisting of cavernous and fractured carbonate rocks complicated by fracturess and low-amplitude tectonics. The analysis of the dynamics of changes in the gas-dynamic, hydrogeological and mining-geological conditions of mines allowed to propose a two-stage advanced degassing of the host rocks as a rather effective method of combating gas manifestations. At the first stage, vertical advance wells are drilled for the entire capacity of the production block. At the second stage, 3–7 horizontal and slightly inclined (up to 10°) wells are drilled in front of the borehole of the underground working under construction. Thus, there is an interval unloading of the massif and the involvement of undeveloped natural gas reserves at the first stage. Actual observations of gas inflows in the underground mine workings showed a significant drop in gas production rates. In such a way, at the «Internatsionalnaya» mine the average gas flow rate per well (per year) decreased from 12.67 to 1.06 m3/h, which confirms the success of the selected two-stage degassing.
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