Process of underground coal gasification

A method for extracting coal values in-situ by in-situ gasification which comprises providing a cavity in the floor rock underlying the coal seam, providing an offset injection well extending from the earth's surface and communicating with said cavity, providing at least one upwardly radially extending injection channel that communicates the cavity with the coal formation at the interface of the coal seam and the floor rock underlying the coal seam, providing at least one production well for each injection channel, said production well extending from the earth's surface and communicating with said coal seam near the base of the seam and laterally spaced apart from said injection channel and lying approximately on the same radii as the injection channel, providing a channel through said coal seam to communicate the production well and the injector channel lying on the same radii, injecting an oxidant in said injection well, igniting said coal seam in the injection channel to form a gasification zone and generate hot product gases at the interface of said coal seam and the floor rock underlying the coal seam, continuing to inject said oxidant gas or oxidant gas mixture to propagate said gasification zone through said seam in a direction toward the production well and producing said hot product gases into said production well.

A method for gasifying underground coal seams by in-situ gasification which comprises providing a cavity in the floor rock underlying the coal seam, providing a plurality of upwardly radially extending spaced injection channels that communicate the cavity with the coal seam at the interface of the coal seam and the floor rock underlying the coal seam, providing an injection well extending from the earth's surface and communicating with said cavity, providing a plurality of production wells equal to the number of said injection channels, said production wells extending from the earth's surface and communicating with said coal seam near the base of the seam, said production wells surrounding said cavity and substantially concentric therewith and laterally spaced apart from said injection channels and lying approximately on the same radii as said injector channels, injecting an oxidant in said injection well, igniting said coal seam in the injection channels to form a gasification zone and to generate hot product gases at the interface of said coal seam and the floor rock underlying the coal seam, continuing to inject said oxidant gas or oxidant gas mixture to propagate said gasification zone through said seam in a direction toward the production well and producing said hot product gases into said production well.