Fundamental Experiments for Developing Underground Coal Gasification (UCG) System

For Underground Coal Gasification (UCG), it is necessary to evaluate the combustion area in the coal seam precisely. We are planning to use acoustic emission/microseismicity (AE/MS) monitoring for estimation of the underground combustion area. Analyzing the AE/MS waveforms from underground rocks, fracture extension around the combustion reactor can be grasped. For this objective, laboratory experiments are conducted for the UCG model. During burning coal block molded cylindrically by mortar, temperatures inside coal and AE activity were monitored. From the experimental results, it was found that many AE events were generated during combustion of coal, and the AE activity was close related to the change of temperature inside coal block. These AE generations seems to be caused by the crack initiation and extension around coal combustion area in the influence of thermal stress. Therefore, AE/MS monitoring is expected to be a useful tool to evaluate the UCG combustion reactor.