Seeing Coal Top Ahead of the Drill-bit Through Seismic-while-drilling – Results from Numerical Modeling

Blast damage to coal seams due to incorrect blast stand-off distances costs the equivalent of one unnecessary open cut mine for every 10 existing Australian mines. The current approach for mapping coal seam tops is through drilling and pierce-point logging. To provide appropriate depth control with ±0.2 m precision for blast hole drilling, a 50m x 50m grid is required in advance of overburden removal. Pierce-point mapping can be inaccurate and expensive as the seam is not flat. To date, there are no effective and economic techniques to map coal seam structures in the open cut environment where coal seams are shallow. In this paper, we propose two Seismic-While-Drilling (SWD)-based approaches to see the top of the coal seam ahead of the drill-bit: 1) reverse VSP recording, in which the geophones are planted on the surface near the drill rig; 2) in-seam seismic recording, in which the geophones are locked in the coal seam in a borehole. Numerical modeling demonstrates the feasibility of these two approaches for predicting the approach of coal seams during blasthole drilling. If these methods can be reliably realized in practice, significant coal resources can be saved and the mines can become more productive and profitable.