Checkshots

For these seven wells, the difference between checkshot time and integrated traveltime is plotted. Note that there is a difference (Tdiff) that grows with depth. The most likely explanation for this is dispersion: the sonic log is measured in kilohertz, while the seismic is in hertz. The pattern within each well is one of consistent growth.

Most importantly, the pattern between wells is consistent. This means that in a well without a checkshot survey, you can build a synthetic seismogram, stretch it by 7%, and expect a very close tie. The same relationship does not hold with raw logs.