Method for in situ gasification of a subterranean coal bed

Claim 1

An improvement in the method of in situ gasification of a subterranean coal bed wherein combustion-supporting gas is introduced into the coal bed through at least one bore penetrating the coal bed to support and maintain combustion of the coal and wherein gaseous products resulting from the combustion are withdrawn from the coal bed through at least one other bore penetrating the coal bed at a location spaced from the first-mentioned bore, said improvement comprising the steps prior to the combustion of the coal of interconnecting the first and second bore by directing a beam of collimated monochromatic light beam into the coal bed with said light beam having sufficient energy to effect penetration of the coal bed and the formation of an elongated bore projecting between the first and second bore along a tortuous path defined by a plurality of straight serially-connected bore segments, and thereafter enlarging the elongated bore by fracturing the coal bed defining the walls of the elongated bore.