Subsurface seismic imaging with a hammer drilling source at an exploration drilling test center in Örebro, Sweden

Abstract

Abstract. Seismic imaging while drilling (SWD) technology offers possibilities of imaging ahead of the drill-bit, which could be useful for determining when to go from hammer drilling to core drilling. Also, seismic images of the surrounding rock can improve geological models which could be then used to guide drilling programs. An SWD field test was carried out in August 2020 at an exploration drilling test site in Örebro, Sweden, with the aim to determine if the signals from hammer drilling can be used for seismic imaging around the drill-bit in a hard-rock environment where the strong drill-rig noise interference is one of the main challenges. The test site had previously been investigated with various geophysical methods, geological mapping and diamond core drilling, and it therefore represented an ideal location to perform this feasibility study. After data pre-processing and cross-correlation with the trace from the geophone closest to the rig, the shot-gathers were vertically stacked over the length of a drill pipe to achieve further signal improvement. A comparison with the active seismic data shows reasonable agreement, in spite of the fact that the noise level is significant even after careful processing. However, the lack of clear reflections in the active seismic data, indicating no detectable changes in the bedrock lithology in the near surface, hinders the full assessment of the seismic signal generated with hammer drilling at this site.

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

“…Therefore, the obtained error values form elliptical shapes, favouring the X-coordinate estimation. As argued by Ivandic et al (2022), increasing the offsets would have benefited the research potential of this experiment. An optimal geometry would have equal coverage in W-E and S-N directions, with offsets reaching further.…”

“…This was followed by many developments, including a numerical study on locating scatterers during tunnelling without a pilot trace (Harmankaya et al., 2018). Borehole ahead‐of‐the‐bit imaging has successfully been conducted for several drilling operations (Aldawood et al., 2021; Bakulin et al., 2020; Goertz et al., 2021; Ivandic et al., 2022; Poletto et al., 2022; Wang et al., 2019). SWD has also proven useful for imaging the shallow subsurface (Aldawood et al., 2021; Asgharzadeh et al., 2019; Bakulin et al., 2020).…”

“…Cross‐correlation is a standard procedure performed for signal retrieval regardless of the type of drilling. It has been used for roller‐cone and polycrystalline diamond bits (PDC) (Aldawood et al., 2021; Bakulin et al., 2020; Goertz et al., 2021; Poletto et al., 2022), rotational diamond bits (Sun et al., 2016) and hammer drilling (Asgharzadeh et al., 2019; Chamarczuk et al., 2021; Ivandic et al., 2022).…”

“…At the site in Örebro, Sweden, Ivandic et al. (2022) used frequency filtering, deconvolution and then cross‐correlated the data with the channel closest to the rig as the pilot trace. The obtained shot‐gathers had the central part muted due to the rig noise removal procedure.…”