NSW out of gas, page-10

Templeton,

Not sure what you mean by, "I'm not sure you are right about the carbon footprint especially when it comes to SNG". The CO2 is produced during the water gas shift reaction and shift conversion. These reactions take place underground, and the CO2 is removed at surface before the methanation process, CO +3H2 ->CH4 + H2O where the methane/SNG is produced.

Assuming all the CO2 is captured at surface, the only carbon released to the atmosphere is the carbon contained in the CH4. So unless you are thinking of working in a pure hydrogen economy, you ain'r going to get much better than that?

A few of references, one light and easy, the others are a bit bedtime reading for insomniacs. Enjoy.
http://www.ucgassociation.org/index.php/ucg-technology/a-cleaner-coal-option-ucg-ccs

This is above coal to SNG but you can get the picture
http://nicholasinstitute.duke.edu/sites/default/files/publications/natgas-paper.pdf

The long one, but this is on UCG to electricity
http://www.indiana.edu/~cree/pdf/Viability of Underground Coal Gasification Report.pdf