Application of 222Rn technique to locate subsurface coal heatings in Australian coal mines

Subsurface coal heating poses a significant problem in many coal mines. The identification of the exact location of the heatings that occur in often inaccessible locations several hundred meters deep in goaf areas is a key to allowing effective control measures to be taken. Detailed investigations were carried out to apply the surface-based 222Rn technique to locate subsurface coal heatings in Australia. The results of two field trials indicated that subsurface coal heatings, at depths up to 450 m, lead to isolated 222Rn anomalies on the surface vertically above the heating zones. The geogas microbubble model for 222Rn transport through strata appears to be most in accord with the results of the field trials.