Review on the existing and developing underground coal gasification techniques in abandoned coal seam gas blocks : Australia and global context

Coal is the major energy source which provides about 40% of the total electricity generation of the world. For Australia it is nearly 80%. For meeting global demand with less greenhouse gas emission (GHG), Australia is pursuing for alternative eco-friendly renewable energy sources. In Australia, there are huge ranges of coal resources, especially deep seated coal deposits, which are difficult to extract with conventional mining and the policy makers are practicing "clean coal" policy for further usages of the resources. Coal seam gas (CSG) and underground coal gasification (UCG) is identified technology for exploiting those coal deposits. The UCG is much more effective process for energy exploitation (theoretically greater than 15-20 times) compared to CSG process. Demonstration of UCG projects and development of these technology received momentum as one of the successful pilot project at Chinchilla, Queensland, Australia, which operated successfully from 1997 to 2003 for demonstration power generation and till dated for GTL( gas to liquid) commercial production from the gasification products . Last few years there was a debate for choosing priority policy for CSG / UCG. Australian local entrepreneur and global international oil companies (IOC) sought for massive scale CSG extraction and presently this industry is in booming stage. Apparently it is seen from the industry trend that UCG operation is behind the race compared to CSG activity, however the long term prospect of UCG is brighter as there are not much CSG left in the coal body for exploiting. The ideal conditions of the coal body have been deviated while CSG operation is being done. Only minor amount of hydro-carbon (with in-situ natural gases) are extracted but major share of the coal deposit are left over at deep geological formation. Review on the existing and developing sophisticated technology for next phase of abandoned CSG fields is a potential area for further research and development (R&D). This paper reviews history and methods of UCG both in Australia & global context. The issues related to UCG in abandoned CSG blocks are identified and discussed. Finally the study recommended the scopes of future study. The success of this effort can enlighten the black coal towards "Cleanest and Greenest" source of energy for next generation Hydrogen fuel.