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US 10,209,384 B2Granted
Peak tracking and rejection in acoustic logs
AssigneeHalliburton Energy Services, Inc.
InventorsGrant Philip Goodyear, Kristoffer Thomas Walker, Batakrishna Mandal
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Abstract
Disclosed herein is an approach to improving the accuracy of signal-peak tracking in acoustic logs by supplementing a semblance method used to detect signal peaks in individual coherence-, correlation- or amplitude-based semblance maps with consistency checks based on rock-physics constraints and/or based on history and/or future data for the signal of interest.
Claims20
A method comprising:
- cyclically operating a sonic logging tool deployed within a borehole, each cycle of operation comprising, at a determined depth, sequentially emitting acoustic waves with at least one monopole acoustic source and at least one dipole acoustic source, and measuring resulting acoustic waveforms with a plurality of receivers;
- computing semblance maps from the measured acoustic waveforms measured with the plurality of receivers, each semblance map being associated with one of the cycles of operation and an emission from one of the acoustic sources;
- for each of a plurality of the cycles of operation,
- determining that a dipole-based shear peak, determined from dipole measured acoustic waveforms resulting from emissions from at least one of the dipole acoustic sources, is unavailable for predicting a compressional peak for the cycle;
- identifying, in response to the determining that the dipole-based shear peak is unavailable, a plurality of candidate compressional-wave slowness peaks in a semblance map computed for the cycle from monopole measured acoustic waveforms resulting from a monopole acoustic-wave emission from at least one of the monopole acoustic sources;
- predicting a compressional-wave slowness peak for the cycle, the prediction being based, for at least one of the plurality of cycles, on compressional-wave slowness peaks detected in neighboring cycles and, for at least one of the plurality of cycles, on a shear-wave slowness peak detected for the cycle in a semblance map computed from measured acoustic waveforms resulting from a dipole acoustic-wave emission;
- comparing the plurality of candidate compressional-wave slowness peaks with the predicted compressional-wave slowness peak;
- and
- based on the comparison, selecting, among the plurality of candidate compressional-wave slowness peaks, the peak closest to the predicted compressional-wave slowness peak as the compressional peak for the cycle if it is consistent with the predicted compressional-wave slowness peak;
- aggregating at least the compressional peaks for the plurality of cycles into an acoustic log as a function of depth;
- and
- generating the acoustic log.
9 more elements
A sonic logging system comprising:
- a sonic logging tool comprising at least one monopole acoustic source, at least one dipole acoustic source, and a plurality of acoustic receivers, operable in cycles comprising sequential emission of acoustic waves with the at least one monopole acoustic source and the at least one dipole acoustic source and measurements of resulting acoustic waveforms with the plurality of acoustic receivers;
- and
- a processing facility configured to:
- operate the sonic logging tool at a plurality of depths;
- compute, at each of the depths, semblance maps from the measured acoustic waveforms measured with the plurality of receivers, each semblance map being associated with one of the cycles of operation and an emission from one of the acoustic sources;
- for each of a plurality of cycles of operation,
- determining that a dipole-based shear peak, determined from dipole measured acoustic waveforms resulting from emissions from at least one of the dipole acoustic sources, is unavailable for predicting a compressional peak for the cycle;
- identify, in response to the determining that the dipole-based shear peak is unavailable, a plurality of candidate compressional-wave slowness peaks in a semblance map computed for the cycle from monopole measured acoustic waveforms resulting from a monopole acoustic-wave emission from at least one of the monopole acoustic sources;
- predict a compressional-wave slowness peak for the cycle, the prediction being based, for at least one of the plurality of cycles, on compressional-wave slowness peaks detected in neighboring cycles and, for at least one of the plurality of cycles, on a shear-wave slowness peak detected for the cycle in a semblance map computed from measured acoustic waveforms resulting from a dipole acoustic-wave emission;
- compare the plurality of candidate compressional-wave slowness peaks with the predicted compressional-wave slowness peak;
- and
- based on the comparison, select, among the plurality of candidate compressional-wave slowness peaks, the peak closest to the predicted compressional-wave slowness peak as the compressional peak for the cycle if it is consistent with the predicted compressional-wave slowness peak;
- aggregating at least the compressional peaks for the plurality of cycles into an acoustic log as a function of depth;
- and
- generating the acoustic log.
12 more elements
Dependencies are inferred from the claim text.