Seeing coal‐seam top ahead of the drill bit through seismic‐while‐drilling

Abstract

Blast damage to the tops of coal seams due to incorrect blast standoff distances is a serious issue, costing the industry in Australia about one open‐cut mine for every ten operating mines. The current approach for mapping coal‐seam tops is through drilling and pierce‐point logging. To provide appropriate depth control with accuracy of ±0.2 m for blast hole drilling, it is typically necessary to drill deep reconnaissance boreholes on a 50 m x 50 m grid well in advance of overburden removal. Pierce‐point mapping is expensive and can be inaccurate, particularly when the seam is disturbed by rolls, faults, and other obstacles.Numerical modelling and prototype‐field testing are used in this paper to demonstrate the feasibility of two seismic‐while‐drilling‐based approaches for predicting the approach to the top of coal during blast hole drilling: (i) reverse “walk‐away” vertical seismic profiling recording, in which the drill bit vibration provides the source signal and the geophones are planted on the surface near the drill rig, and (ii) in‐seam seismic recording, in which channel waves, driven by the coupling to the coal of the seismic signal emitted by the approaching drill bit, are guided by the seam to geophones located within the seam in nearby or remote boreholes.

Cousins, Siblings and Twins: A Review of the Geological Model’s Place in the Digital Mine

“…Improving the resolution of geological information will provide more realistic model scenarios, particularly important for geotechnical challenges and improving stability of underground roofs and walls. Techniques are currently being developed for example to detect faults with less than 1m throw [20,21]. Presence of minerals using remotely sensed data hyperspectral data is used widely for geological characterisation [22].…”

Coal top detection by conductively guided borehole radar wave imaging for open cut blast‐hole drilling

“…Drilling beyond this protective layer margin causes exposure and dilution of the uncapped, damaged coal seam, leading to significant losses of the coal (Zhou et al . ). Conversely, drilling short of this protective layer margin results in additional work to remove the intact overburden.…”

“…The seismic‐while‐drilling (SWD) work reported by Zhou et al . () was partially funded by ACARP. Seedsman () initiated the Top of Coal Program, which was followed by Sendt (, ).…”

Conductively Guided Borehole Radar Wave for Imaging Ahead of a Drill Bit

“…It enables drillers to make informed near-realtime decisions to overcome drilling-related problems. These include efficient drill bit steering to a target position, e.g., leaving the correct stand-off distance for open-cut blast-hole drilling [35], avoiding hazardous situations, e.g., sticking and loss of drill strings. This will improve drilling safety and overall efficiency [36].…”