Ann: Gas flows to surface in CSG Project PL 171 , page-10

re: Ann: Gas flows to surface in CSG Project ... Also have a read of this great article: http://anz.theoildrum.com/node/4618

Particularly,

Coal seam gas (also called coal seam methane or coal bed methane) is trapped in coal seams (usually 300-600 metres underground) by water, which must be removed to initiate gas flow. In the past it has been viewed as more of a hazard to miners than a benefit.

CSG is extracted via wells which are drilled down into coal seams - the water is pumped out and the CSG is then released (desorbed) from the coal. If the pressure within the seam is high enough the gas may flow to the surface unaided, otherwise the gas must be pumped.

Various techniques have been developed to enhance the rate of desorbtion, including the pumping of carbon dioxide underground to increase field pressure (which leads some CSG promoters to describe it as a form of "clean coal").