Walk‐away VSP using drill noise as a source

Abstract

We describe a method for extracting and deconvolving a signal generated by a drill bit and collected by an array of surface geophones. The drill-noise signature is reduced to an effective impulse by means of a multichannel Wiener deconvolution technique, producing a walk-away reverse vertical seismic profile (VSP) sampled almost continuously in depth. We show how the multichannel technique accounts for noise and for internal drill-string reflections, automatically limiting the deconvolved data to frequencies containing significant energy.We have acquired and processed a data set from a well in Germany while drilling at a depth of almost 4000m. The subsurface image derived from these data compares well with corresponding images from a 3-D surface seismic survey, a zero-offset VSP survey, and a walk-away VSP survey acquired using conventional wireline techniques. The effective bandwidth of the deconvolved drill-noise data is comparable to the bandwidth of surface seismic data but significantly smaller than what can be achieved with wireline VSP techniques.Although the processing algorithm does not require the use of sensors mounted on the drill string, these sensors provide a very economic way to compress the data. The sensors on the drill string were also used for accurate timing of the deconvolved drill-noise data.

Imaging mining hazards within coalbeds using prestack wave equation migration of in-seam seismic survey data: A feasibility study with synthetic data

“…The goal of this paper is to use reverse-time migration of synthetic two-component data to image discontinuities in 2-D coal seam models and development of a methodology for void characterization. As described here, this solution does not solve the problem of surveying while mining, but this may also be possible by borrowing from the technology of using drill bit noise as a seismic source (e.g., Rector and Hardage, 1992;Haldorsen et al, 1995;Kneib et al, 2000;Petronio and Poletto, 2002;Ashida et al, 2002).…”

Basis Pursuit Receiver Function

“…This technique gives better results in multichannel processing than simultaneous deconvolution, which is biased toward single channel, multievent data (Chen et al, 2010). The filter derived in this method minimizes the noise energy and energy related to instability and thus maximizes the signal energy (Haldorsen et al, 1994(Haldorsen et al, , 1995.…”

Interferometry by deconvolution: Part 2 — Theory for elastic waves and application to drill-bit seismic imaging

“…Most SWD methods rely on so-called pilot sensors to estimate independently the drill-bit excitation ͑Rector and Marion, 1991;Haldorsen et al, 1994;. Without relying on pilot records, Miller et al ͑1990͒ design multichannel weighting deconvolution filters based on statistical assumptions about the source function.…”

“…Poletto and Miranda ͑2004͒ provide a comprehensive description of pilot deconvolution technologies. Some pilot-based SWD methods deconvolve bit excitation directly from recorded data ͑e.g., Haldorsen et al, 1994͒, although most methodologies rely on crosscorrelations ͑e.g., Rector and Marion, 1991;. A close connection exists between correlation-based SWD methods and crosscorrelation interferometry, which we highlight in this paper.…”