Generating T-D Pairs from Sonic Log

The Generate Checkshots tool can be used to generate time-depth pairs from a sonic log.

Checkshots are generated spaced at regular MD intervals based on sonic log data from the well.

Interval velocities are calculated from the sonic log and integrated to calculate travel time. Travel times are converted to time-depth pairs by referencing them to a single, manually entered, time-depth pair from within the log interval. Some pairs can be excluded if they are not required to achieve a specified level of accuracy in TWT.

  1. Ensure your sonic log is assigned the P Slowness class in the Details Panel of the Well tab.
  1. From the Tool menu, open Synthetics.
  2. Select the Current Well.
  3. Right click on the TVDSS-TWT track and select Create/Resample Time-Depth Survey.
  1. Tick the Create New Time-Depth Survey option to create a new survey. Otherwise the active time-depth survey in the well will be overwritten with the newly created one.  
    Note: When creating a new survey, a unique name must be provided.
  2. At Mode, select From Log.
    • Initial T-D Pair: An initial time-depth pair must fall within the MD range of the P Slowness curve      
    • Interval (MD): Minimum MD interval between consecutive generated checkshots      
    • Accuracy (ms): Pairs that affect time-depth conversion below this amount are excluded.      
    • Velocity Scale: The velocities derived from the P Slowness curve are scaled by this factor      
    • P Slowness: Select sonic log. Ensure units are correct.
  3. Click OK.