The method of the present invention relates to providing controlled directional bores in subterranean earth formations, especially coal beds for facilitating in situ gasification operations. Boreholes penetrating the coal beds are interconnected by laser-drilled bores disposed in various arrays at selected...http://www.google.de/patents/US4026356?utm_source=gb-gplus-sharePatent US4026356 - Method for in situ gasification of a subterranean coal bed
