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Abstract. Acoustic energy emitted by drill bits can be recorded bygeophones on the surface and processed for an image of the subsurface usingseismic interferometry methods. Pilot sensors record bit signals on the drillrig and play an important role in processing geophone traces for the image.When pilot traces are not available, traces of the nearest geophone to therig may be used in deconvolution and cross-correlation of data, but extrasignal processing efforts are required to reduce the effect of sourcesignature on cross-correlation results. In this study, we use the seismicinterferometry method to image the shallow subsurface beneath a 2-D geophonearray by converting geophones to virtual sources. As there is no pilotsignal available for this survey, we use the nearest geophone trace for pilotcross-correlation and pilot deconvolution. We modify the spectrum of pilotcross-correlation and deconvolution results so that the effect of sourcefunction on virtual data is minimized. We then migrate the virtual shots andcompare the results of interferometric imaging with the available image from3-D (active source) survey and assess the efficiency of our approach. We showthat drill bit noise data can be used to generate a reasonably accurateimage of the subsurface even in the absence of pilot recordings, but theresults should be checked for the appearance of virtual multiples and depthinconsistencies that are caused by errors in the migration velocity.

Drill bit noise imaging without pilot trace, a near-surface interferometry example