Fundamental Experiments for Developing Underground Coal Gasification (UCG) System

Abstract

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.

石炭の地下ガス化（UCG）においては，炭層内の燃焼領域を正確に把握する必要がある。この燃焼領域の評価のためにAE/MS（破壊音）計測を計画している。AE/MS 波形を解析することにより，燃焼領域周辺の破壊進展を把握することが可能になる。このために，モルタルで円柱形に固めた石炭塊の燃焼実験を行い，燃焼中の内部温度，AE 活動を計測した。その結果，燃焼中に多くのAE が発生し，そのAE 活動は内部温度の変化と関連していた。これらのAE の発生は，燃焼領域の周辺で熱応力によりき裂が発生，拡張したためと考えられる。このため，AE/MS 計測はUCG の燃焼領域の評価に有効な手段になりえることが確認された。