Gas-Bearing Capacity of Rock

the amount of free or retained gas (primarily methane) contained in a unit of mass or of volume of rock under natural conditions, measured in cu m per ton or cu m per cu m.

Coal deposits have the highest gas-bearing capacity. For example, at atmospheric pressure, 1 cu cm of coal has the capacity to retain 7-8 cu cm of methane or up to 18 cu cm of carbon dioxide. With a rise in pressure in the gas-bearing layers, the amount of gas that can be absorbed by them is increased. Gas-bearing capacity is influenced by many factors, the most important of which are the geological conditions of the region’s development, the extent of gas formation during rock metamorphism, the gas permeability of the deposits surrounding the coal seams, and the gas content of the minerals and surrounding rock. Besides methane, coal seams may also contain carbon dioxide; hydrogen sulfide, sulfur dioxide, or other gases are given off from some coal seams.