Drill-bit seismic and pilot seismograms contain drill-string periodicities from signal and environmental noise sources. These coherent components are similar in seismic-while-drilling correlations, and their joint contribution may cause distortions in signal processing. Numeric modeling of the drillstring transmission line is used to correctly interpret the axial and torsional events with similar propagating modes of signal and noise. The reflection coefficients are computed for drillstrings of arbitrary materials, and their average mechanical features are related to the axial and torsional group velocities obtained by the dispersion equations. Fitting of the periodical components in the real seismograms is used to automatically correct the drill-bit pilot delays and to estimate the surface and downhole boundary conditions.
CITATION STYLE
Poletto, F., Malusa, M., & Miranda, F. (2001). Numerical modeling and interpretation of drillstring waves. Geophysics, 66(5), 1569–1581. https://doi.org/10.1190/1.1487102
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