Changes

[[file:full-waveform-acoustic-logging_fig1.png|thumb|300px|{{figure number|1}}FWAL microseismograms recorded (a) at two source-receiver separations and (b) In a “soft” formation at two source-receiver separations.]]

[[file:full-waveform-acoustic-logging_fig1.png|thumb|300px|{{figure number|1}}FWAL microseismograms recorded (a) at two source-receiver separations and (b) In a “soft” formation at two source-receiver separations.]]

There are three wave arrivals that can easily be identified in a full waveform acoustic log.<ref name=pt07r6>Cheng, C. H., Toksöz, M. N., 1981, Elastic wave propagation in a fluid-filled borehole and synthetic acoustic logs: Geophysics, v. 46, p. 1042–1053, DOI: 10.1190/1.1441242.</ref> In order of arrival time, they are the P wave packet, the S wave packet, and the Stoneley wave ([[:file:full-waveform-acoustic-logging_fig1.png|Figure 1a]]). The first two are analogs of the compressional and shear head waves refracted along the borehole wall. In a “soft” formation where the shear wave velocity is lower than the acoustic velocity of the borehole fluid (such as in semiconsolidated sediments), there is no refracted S wave arrival ([[:file:full-waveform-acoustic-logging_fig1.png|Figure 1b]]). The ''Stoneley wave'' is a pressure pulse created by the wave guide effect of the borehole and is called the ''tube wave'' in checkshot surveys or vertical seismic profiling surveys. Because the wavelength of the pressure pulse is approximately the size of the borehole diameter, there is a significant borehole wave guide effect. Thus, the refracted P and S wave arrivals along the borehole or formation boundary are not pure P and S waves. However, the first arrivals from these packets still travel with the formation P and S wave velocities, respectively.<ref name=pt07r6 /><ref name=pt07r45>Paillet, F. L., White, J. E., 1982, Acoustic modes of propogation in the borehole and their relationship to rock properties: Geophysics, v. 47, p. 1215–1228, DOI: 10.1190/1.1441384.</ref> The amplitudes of these waves are affected by a combination of the formation P and S wave attenuation and that of the borehole fluid. The Stoneley wave travels with a velocity that is slower than both the formation shear wave velocity and the acoustic velocity of the borehole fluid.

There are three wave arrivals that can easily be identified in a full waveform acoustic log.<ref name=pt07r6>Cheng, C. H., and M. N. Toksöz, 1981, Elastic wave propagation in a fluid-filled borehole and synthetic acoustic logs: Geophysics, v. 46, p. 1042–1053, DOI: 10.1190/1.1441242.</ref> In order of arrival time, they are the P wave packet, the S wave packet, and the Stoneley wave ([[:file:full-waveform-acoustic-logging_fig1.png|Figure 1a]]). The first two are analogs of the compressional and shear head waves refracted along the borehole wall. In a “soft” formation where the shear wave velocity is lower than the acoustic velocity of the borehole fluid (such as in semiconsolidated sediments), there is no refracted S wave arrival ([[:file:full-waveform-acoustic-logging_fig1.png|Figure 1b]]). The ''Stoneley wave'' is a pressure pulse created by the wave guide effect of the borehole and is called the ''tube wave'' in checkshot surveys or vertical seismic profiling surveys. Because the wavelength of the pressure pulse is approximately the size of the borehole diameter, there is a significant borehole wave guide effect. Thus, the refracted P and S wave arrivals along the borehole or formation boundary are not pure P and S waves. However, the first arrivals from these packets still travel with the formation P and S wave velocities, respectively.<ref name=pt07r6 /><ref name=pt07r45>Paillet, F. L., and J. E. White, 1982, Acoustic modes of propogation in the borehole and their relationship to rock properties: Geophysics, v. 47, p. 1215–1228, DOI: 10.1190/1.1441384.</ref> The amplitudes of these waves are affected by a combination of the formation P and S wave attenuation and that of the borehole fluid. The Stoneley wave travels with a velocity that is slower than both the formation shear wave velocity and the acoustic velocity of the borehole fluid.

==Dataprocessing==

==Dataprocessing==