While shale gas has hurt the economics for UCG in the US, it has also led to improvements in seismic technology and horizontal drilling that may vastly improve the economics in the long term.
At that time underground coal gasification (UCG, also known as in-situ coal gasification or ISCG) was increasingly seen as a relatively low-impact way of tapping the huge US coal resource, while potentially managing emissions.
The concept of heating underground coal to a combustion point may lead one to recall Centralia, PA, an abandoned town in Pennsylvania sitting on a coal seam which has been burning for 50 years, but the UCG controlled process makes that outcome highly unlikely.