Recording seismic data while drilling (SWD) can help to determine whether the drilling proceeds along the desired trajectory. This information can help to take action in advance to adjust the drilling process to the desired trajectory. 

For this purpose, Uppsala University has suggested a method and performed numerical modelling (Figure 1). The results showed that the applied method has a potential to determine the drill-bit trajectory. Moreover, in the used model it is possible to observe deviation after 2 m (Figure 2). Near real-time processing of the data may then allow a near real-time correction of the drilling trajectory (Ridderbusch et al., 2020).

Figure 1 (a) Acquisition geometry used for creating synthetic drill-bit signals. The stars mark the
positions of the drill-bit sources. (b) Detail showing the positions of the drill-bit source for a deviating
(red) and non-deviating (yellow) drilling trajectory (dashed line). The solid lines display schematic ray paths to the receivers at 280 m and 320 m.

The group has submitted the results as an extended abstract to the upcoming EAGE (European Association of Geoscientists & Engineers) Near Surface Geoscience Conference & Exhibition (Belgrade, Serbia, 30 August-3 September). Currently the group is working on more realistic and complex near-surface models to see the success of the method.

The SWD modelling has also been performed to test if the signals from hammer drilling can be used for seismic imaging of the surrounding rock and shows promising results.

The SWD method will be soon tested on the field seismic data. The drilling at the Örebro test site, which was supposed to provide the real data set, was initially planned for March – May, but was later moved to August due to the Covid-19 situation. The drilling was finally conducted in Week 33. Seismic data processing and analysis will be carried out in the next months.

Figure 2 Travel time differences between retrieved signals from different depths. Shown are the crosscorrelation panels for the non-deviating (a), (c) and (e) as well as for the deviating drilling trajectory (b), (d) and (f). From top to bottom the panels show the cross-correlations of 10 m depth with 20 m depth, 10 m depth with 30 m depth and 10 m depth with 40 m depth. The yellow dashed lines in (e) mark the most prominent correlation phases (Ridderbusch et al., 2020).

Jan Ridderbusch, Maryam Abbasian and Ayse Kaslilar. Monitoring Drilling Trajectory by Using Drill-bit Signal as a Source, NSG, Sept 2020, Belgrade, Serbia.



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