Underground gasification of superimposed coal seams in sequence - by restricting gas supply to individual seams

摘要

In situe gasification of multiple, relatively thin coal seams sepd. by several metres of rock comprises blowing in an oxidising or hydrating gasifying agent through a borehole into one or a few seams at time, while the other seams are sealed off. The remaining seams are gasified in turn, after gasification of the first seams is substantially complete. Each seam or group of seams is gasified as quickly as possible, so that escape of heat from the seam into the adjacent rock layers is minimised, and its contribution to the endothermic gasification reation is increased.