Not only a significant part of the world’s coal resources, but also their satellite, methane, whose scale is commensurate with the gas resources of traditional world deposits, is concentrated in the depths of the developed and prospective coal basins. The concentration of methane in a mixture of natural gas from coal seams is 80–98%.
The scientifically based assessment of the role of coal seams as the largest places of methane accumulation in the earth’s crust opens up new promising prospects for increasing hydrocarbon gas resources. Methane, which is the most dangerous companion of coal, becomes a valuable mineral, subject to independent commercial production or associated extraction in mines with complex step-by-step exploitation of gas-bearing coal deposits.
There are two fundamentally different ways to extract coal methane: mine (in the fields of existing mines) and borehole.
The mine method is an integral part of the underground coal mining technology – degassing. At the same time, the volume of methane produced is small, and gas is used mainly for the own needs of coal mining companies directly in the coal mining area.
Well production method is industrial. At the same time, methane is no longer viewed as a by-product in coal mining, but as an independent mineral. The development of methane-coal deposits with the extraction of methane on an industrial scale is carried out using special technologies for the intensification of gas recovery (the most common options are hydraulic fracturing, injection of air or air-air mixture through the well, and impact on the formation with current).
It should be noted that not all coals are suitable for the extraction of methane. So, deposits of long-flame brown coal are poor in methane. The high concentration of gas is characterized by anthracite coal, but it cannot be extracted due to its high density and extremely low reservoir permeability. The most promising for the extraction of methane are coal, which occupies an intermediate position between brown coal and anthracite.