All types of unconventional gas will be much less efficient to recover than conventional gas and will have to be produced at slower recovery rates. Tight gas is natural gas in either blanket or lenticular sandstones that have in-situ effective permeability of less than 1 millidarcy. The black and dark brown Devonian shale is rich in organic matter and has a much higher gas content than the poorer-organic gray Devonian shale. The potential for technical improvements in geopressured gas recovery would parallel the experience of deep-gas-well drilling. Some of the gas entrapped in and around coal seams can be liberated either by premining degasification or by the act of mining itself. The gas that can be obtained from premining draining of coal seams is considered to have greater energy potential. The initial domestic target for recovering natural gas from coal seams is the 0.08 trillion cubic feet of methane emitted annually from working coal mines.