Abstract: Sonic logging has been seldom applied in average velocity field, owing to some limits of data collection and defection of sonic logging. Sonic logging can be adjusted to VSP through drift calculation of sonic logging, drift correction of sonic logging and calculation of compensation time of shallow layer.Therefore acoustic logging is used to correct velocity spectrum in average velocity field. The average velocity field with maximum absolute error of 54 m/s and maximum relative error of less than 2% in XJ area is tested by using VSP of two new wells.

Key words: sonic logging, drift of sonic logging, compensation time of the shallow layer, average velocity field, XJ area