Introduction
This document outlines the general steps in calibrating a velocity data (downhole sonic or laboratory velocity profile) using a time-depth data (such as checkshots) in order to generate a time-depth relationship (TDR) curve and be able to accurately hang/tie the well/borehole data in time domain (i.e., Core-Log-Seismic Correlation). At every depth level, the calibration process calculates the drift, which is equivalent to the checkshot time minus the integrated sonic time, and applies this value to the sonic data. The result is a sonic data that is adjusted to match the times derived from the checkshot survey, thereby combining the high data resolution of the sonic log, and the accuracy of the checkshot data.
The workflow requires that a well or borehole is created in a properly defined project, with a reflection seismic profile, a downhole sonic or core velocity and a checkshot data already imported.
Procedure
1. In the Seismic interpretation toolbar tab > Seismic-well calibration group > click on the Seismic well tie button.
Figure 1: Petrel Seismic well tie button.
2. In the Seismic well tie dialog box that appears, select Sonic calibration from the Study type dropdown list. Select the well or borehole to use.
3. For the template, select the default sonic calibration template.
Select the parameters in the various tabs at the lower half of the dialogue box.
4. Input
5. Output
6. Datuming
7. Time-depth
8. Options
9. When you are satisfied with the parameters, click OK. A well section window will appear showing the results of the calibration process.
10. Well tie editing tool palette
11. Save TDR and apply to well.