http://www.cougarenergy.com.au/UCG.html
UCG EXPLAINED
Underground coal gasification (UCG) is the process by which coal is converted in situ into a combustible gas that can be used as a fuel or a chemical feedstock. UCG has the potential to exploit coal resources that are either uneconomic to work by conventional open cut or underground coal mining methods, or are inaccessible due to depth, geology or other mining and safety considerations.