Example 1
Sonic calibration with check-shot. Drift curve shows the diference transit time of check-shot and cumulative sonic two way time.
Generated synthetic trace from calibrated TDR spliced with correspondig seismic data.
Example 2
Sonic calibration with check-shot. Drift curve shows the diference transit time of check-shot and cumulative sonic two way time.
Generated synthetic trace from calibrated TDR spliced with correspondig seismic data.
Example 3
3D stacking velocoty model with check-shot projected in well position.
Sonic calibration with check-shot. 3D stacking velocoty model with check-shot projected in well position.
Stacking to Interval velocity conversion (CVI method)
Overview:
In seismic processing, stacking (RMS) velocities are commonly derived from velocity analysis. While useful for basic NMO correction, RMS velocities cannot be directly used for depth imaging or geophysical interpretation. To build accurate subsurface models, we need interval velocities the true velocities of each layer in the subsurface. The Constrained Velocity Inversion (CVI) method provides a robust and reliable way to convert RMS velocities into interval velocities, even when the data is noisy or contains outliers.
The CVI method is a robust and production-ready approach for converting RMS velocities into interval velocities. It is especially useful for modern seismic workflows where velocity picks are noisy or discontinuous, providing a stable and physically meaningful velocity model for depth imaging and interpretation.
Why CVI is Better than Traditional Methods:
The classical approach, known as Dix differentiation, is highly sensitive to:
- Noisy velocity picks
- Irregular time sampling
- Lateral inconsistencies
CVI overcomes these issues by using a regularized inversion approach. It balances fitting the data with producing smooth, realistic interval velocity profiles.
Key benefits:
- Smooth and laterally consistent interval velocity fields
- Less sensitive to picking errors
- Physically realistic velocities, avoiding impossible negative or zero values
- Ideal for depth imaging workflows (PSTM/PSDM)
How It Works:
Without using formulas, the CVI process can be explained in simple steps:
- Input RMS velocities: The method starts with the RMS velocities obtained from velocity analysis.
- Weighted inversion: It calculates the interval velocity for each layer, considering the RMS trend over time.
- Smoothness control: Vertical smoothness is applied to avoid unrealistic jumps between layers.
- Lateral consistency: Neighboring traces are considered to ensure lateral continuity and reduce isolated outliers.
- Physical limits: The method enforces minimum and maximum plausible velocities to maintain realistic results.
- Fallback mechanism: For locations with unreliable picks, a fallback method (similar to Dix) ensures the interval velocity remains valid.
The result is a stable, realistic interval velocity model ready for seismic imaging or depth conversion.
Practical Advantages
- Handles noisy or discontinuous velocity picking data
- Suppresses spikes and extreme outliers
- Produces smooth vertical and lateral velocity trends
- Suitable for automated seismic processing workflows
- Provides reliable input for depth imaging and geophysical interpretation
Recommended Use
- Use CVI for all velocity picking data before depth conversion
- Apply soft constraints for minimum and maximum velocities
- Use a moderate lateral smoothing radius to maintain lateral consistency
- Validate results by reconstructing RMS velocities and checking for anomalies
RMS calibrated 3D velocity model
