Practical Depth Conversion with Petrel

Depth conversion (domain conversion) of seismic time interpretations and related data within Petrel is a critical skill set for interpreters. However, there is no single methodology that is optimal for all cases, since the available seismic and geologic control varies in quantity and quality within each project. To impart an effective approach to depth conversion, the first part of this course prioritizes understanding the nature of velocity fields and practical approaches to velocity representation. Next, present appropriate (vertical) time-to-depth conversion methods suitable for time migration in case history and exercise form. Review single-layer and more sophisticated multi-layer approaches along with structural-uncertainty analysis.

Depth conversion must also embrace the process of database validation. The database QC issues reviewed will include incorrect well locations and deviations, improper assessment of seismic polarity and phase, mis-correlated seismic horizons, and inconsistent formation tops. The issues above compromise the interpretation, introduce distortions in the implied velocity field, and can result in false structures. Next, address database validation via the formation of synthetic seismograms to confirm horizon correlations and the use of intuitive QCs such as seismic horizon versus well-top cross plots to detect inconsistencies.

Prestack depth migration is now commonplace, and there is always the need to calibrate the depth volumes with well tops. We will leverage the same basic QCs and methods used for vertical time-to-depth conversion to validate the fidelity of the formation tops and the seismic depth surfaces used for calibration. This is particularly important during anisotropic depth migration where inconsistencies between well control and the seismic interpretation impact the estimation of anisotropic parameters, resulting in a compromised depth-imaging project.

This course emphasizes the formation of velocity models appropriate for the available data. This is in context to creating Petrel Velocity Models suitable for initializing reservoir characterization employing depth-calibrated seismic inversions and other attribute cubes precisely integrated with the well information. Finally, cover structural uncertainty analysis using various approaches to provide a critical metric for depth estimation accuracy.

The course agenda can be shortened if required.