Changes

==Dataprocessing==

==Dataprocessing==

[[file:full-waveform-acoustic-logging_fig2.png|thumb|{{figure number|2}}FWAL microseismograms across a fracture zone.]]

[[file:full-waveform-acoustic-logging_fig2.png|thumb|300px|{{figure number|2}}FWAL microseismograms across a fracture zone.]]

With some FWAL tools, the slowness (inverse velocity or time needed to travel a fixed distance) is obtained the same way as in conventional sonic tools by picking the P wave arrival using a threshold detection algorithm and measuring the moveout between two receivers.<ref name=pt07r63>Willis, M. E., Toksöz, M. N., 1983, Automatic P and S velocity determination from full waveform acoustic logs: Geophysics, v. 48. p. 1631–1644, DOI: 10.1190/1.1441444.</ref> Because of the lower frequency content, this method is not as accurate as that used with conventional sonic tools. The newer generation of FWAL tools take advantage of the larger number of receivers. Several different array processing techniques are used, the most common being semblance stacking along different slownesses.<ref name=pt07r29>Kimball, C. V., Marzetta, T. L., 1984, Semblance processing of borehole acoustic array data: Geophysics, v. 49, p. 274–281, DOI: 10.1190/1.1441659.</ref> <ref name=pt07r22>Hsu, K., Baggeroer, A. B., 1986, Application of the maximum likelihood method (MLM) for sonic velocity logging: Geophysics, v. 51, p. 780–787, DOI: 10.1190/1.1442130.</ref> <ref name=pt07r33>Lang, W. W., Kurkjian, A. L., McClellan, J. H., Morris, C. F., Parks, T. W., 1987, Estimating slowness dispersion from arrays of sonic logging waveforms: Geophysics, v. 52, p. 530–544, DOI: 10.1190/1.1442322.</ref> This method can also be used to obtain the slownesses of the later arrivals, namely, the S wave and the Stoneley wave.

With some FWAL tools, the slowness (inverse velocity or time needed to travel a fixed distance) is obtained the same way as in conventional sonic tools by picking the P wave arrival using a threshold detection algorithm and measuring the moveout between two receivers.<ref name=pt07r63>Willis, M. E., Toksöz, M. N., 1983, Automatic P and S velocity determination from full waveform acoustic logs: Geophysics, v. 48. p. 1631–1644, DOI: 10.1190/1.1441444.</ref> Because of the lower frequency content, this method is not as accurate as that used with conventional sonic tools. The newer generation of FWAL tools take advantage of the larger number of receivers. Several different array processing techniques are used, the most common being semblance stacking along different slownesses.<ref name=pt07r29>Kimball, C. V., Marzetta, T. L., 1984, Semblance processing of borehole acoustic array data: Geophysics, v. 49, p. 274–281, DOI: 10.1190/1.1441659.</ref> <ref name=pt07r22>Hsu, K., Baggeroer, A. B., 1986, Application of the maximum likelihood method (MLM) for sonic velocity logging: Geophysics, v. 51, p. 780–787, DOI: 10.1190/1.1442130.</ref> <ref name=pt07r33>Lang, W. W., Kurkjian, A. L., McClellan, J. H., Morris, C. F., Parks, T. W., 1987, Estimating slowness dispersion from arrays of sonic logging waveforms: Geophysics, v. 52, p. 530–544, DOI: 10.1190/1.1442322.</ref> This method can also be used to obtain the slownesses of the later arrivals, namely, the S wave and the Stoneley wave.