Drill-bit position monitoring using seismic-while-drilling data; numerical and field examples from Sweden

The undesired drill-bit deviation is a source of drilling risks and requires monitoring. Seismic-while-drilling is one potential method to achieve this and has been tested in a number of previous studies. In August 2020 in orebro, Sweden, we conducted an experiment to test the feasibility of seismic-while-drilling drill-bit positioning and other applications of the method. We used the hammer drill-bit signal generated while drilling a 200 m deep well in hardrock conditions and implemented vertical stacking of the subsequent impulsive signals from the hammer source, generating enhanced direct arrivals from the drill-bit. Then, we used the relative arrival times to estimate the drill-bit position for selected bit depths, confirming our methodology with two numerical studies. We successfully estimated the position of the drill-bit for the numerical examples and for several of the real data examples, with the accuracy dependent on the receiver array geometry and the quality of the data. We conclude that this drill-bit positioning method shows potential for near-real-time monitoring in drilling operations that could be applicable for both impulsive and noise-retrieved drill-bit signals.