Seismic Velocity Model Conditioning via Overshoot Layers
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Solution Overview
Problem
Conventional seismic imaging techniques, such as reverse time migration, face issues with backscattering noise, wavelet distortion, mis-positioning of boundaries, and discretization grid stair-casing diffraction noise due to high-contrast velocity boundaries, which are inadequately mitigated by traditional smoothing methods.
Innovation Solution
The method involves obtaining an initial velocity model with sharp transitions and conditioning it to create a gradual velocity transition using a velocity overshoot layer, which compensates for kinematic differences, thereby reducing artifacts in seismic images by employing a computer system to process seismic data and generate improved subsurface images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional smoothing techniques are applied to velocity boundaries, then some artifact mitigation is achieved, but manufacturing precision of velocity model deteriorates due to inadequate resolution preservation
Solution Approach 1:
The patent applies parameter changes by modifying the velocity model through a ramp function that gradually transitions velocity values across the boundary. This controlled parameter transformation reduces the sharp contrast that causes backscattering noise while preserving the essential structural features of the velocity model.
Solution Approach 2:
The patent performs preliminary action by applying the velocity ramping transformation before the seismic imaging process. This pre-processing step prepares the velocity model to minimize artifacts during subsequent imaging operations, rather than attempting to correct artifacts after they are generated.
2Measurement precision
If velocity ramping is applied at geologic layer boundaries, then wavelet distortion and boundary mis-positioning are reduced, but device complexity increases due to additional processing steps
Solution Approach 1:
The patent applies local quality by implementing velocity ramping only in specific localized regions where geologic layer boundaries are detected, rather than uniformly across the entire velocity model. This targeted approach improves boundary positioning accuracy where needed while minimizing additional processing complexity in other regions.
Solution Approach 2:
The patent introduces an intermediary ramp function as a mathematical mediator between the sharp velocity discontinuity and the seismic imaging process. This intermediate transformation layer gradually transitions velocity values, reducing boundary artifacts without requiring complex iterative corrections during imaging.
3Stability of the object's composition
If sharp velocity transitions are maintained in the velocity model, then structural features around salt bodies are preserved, but discretization grid stair-casing diffraction noise increases
Solution Approach 1:
The patent applies segmentation by dividing the sharp velocity transition into multiple gradual segments using a ramp function. This segmentation of the velocity transition reduces the abrupt changes that cause diffraction noise while maintaining the overall structural integrity and composition of the geologic features.
Solution Approach 2:
The patent applies curvature by replacing the sharp angular velocity discontinuity with a smooth curved transition through the ramp function. This curvature in the velocity profile eliminates the stair-casing effect that generates diffraction noise while preserving the essential geometric features of the subsurface structures.
Data Source
AI summary
A method for seismic imaging of a subsurface volume of interest may include an imaging technique such as reverse time migration which uses a conditioned velocity model that replaces at least one sharp velocity transition with a gradual velocity transition including a velocity overshoot layer. The method may be performed by a computer system.