Sensitivity Kernel Migration Velocity Analysis in 3D Anisotropic Media
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Solution Overview
Problem
Existing migration velocity analysis techniques in seismology rely on ray-based tomography, which causes excessive smoothing in velocity updates, limiting the resolution of subsurface images and often failing to match accepted geophysical principles.
Innovation Solution
The use of sensitivity kernel-based migration velocity analysis in 3D anisotropic media, which migrates seismic survey data with an anisotropic velocity model to obtain common angle image gathers, processes depth residuals, and converts them into velocity errors to refine the velocity model, providing increased stability and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ray-based tomography is used for migration velocity analysis, then the velocity model can be updated, but excessive smoothing occurs in the velocity updates which limits resolution
Solution Approach 1:
The patent changes the fundamental parameter from ray-based tomography to sensitivity kernel-based migration velocity analysis. This parameter change allows the system to maintain velocity model updates while avoiding excessive smoothing, thereby resolving the contradiction between resolution and update accuracy.
Solution Approach 2:
The patent replaces the ray-based mechanical tomography system with a sensitivity kernel-based system that uses common angle image gathers. This substitution eliminates the excessive smoothing problem inherent in ray-based methods while preserving the ability to update velocity models accurately.
2Reliability
If ray-based tomography is used for migration velocity analysis, then velocity updates can be obtained, but the results fail to match accepted geophysical principles
Solution Approach 1:
The patent substitutes ray-based tomography with sensitivity kernel-based MVA that operates in the common angle image gather domain. This substitution ensures that velocity updates comply with accepted geophysical principles while maintaining accuracy in the velocity model.
Solution Approach 2:
The patent introduces common angle image gathers as an intermediary between the seismic data and the velocity model updates. This intermediary allows the system to obtain velocity updates that are both accurate and compliant with geophysical principles, resolving the contradiction between reliability and precision.
3Measurement precision
If traditional migration velocity analysis is used, then subsurface imaging can be performed, but the resolution is limited due to excessive smoothing
Solution Approach 1:
The patent replaces traditional ray-based MVA with sensitivity kernel-based MVA using common angle image gathers. This substitution improves subsurface image resolution by avoiding excessive smoothing while managing processing complexity through an efficient computational framework.
Data Source
AI summary
Seismic imaging systems and methods that employ sensitivity kernel-based migration velocity analysis in 3D anisotropic media may demonstrate increased stability and accuracy. Survey data analysts employing the disclosed systems and methods are expected to provide better images of the subsurface and be better able to identify reservoirs and deposits for commercial exploitation. Certain embodiments migrate seismic survey data with an anisotropic velocity model to obtain common angle image gathers. These gathers are processed to obtain depth residuals along one or more horizons. Angle-domain sensitivity kernels are used to convert the depth residuals into velocity errors, which are then used to refine the velocity model. A user is then able to view a representation of the subsurface structure determined in part from the refined velocity model. Multiple iterations may be needed for the velocity model to converge. The velocity model may be a layered to have constant velocity values between formation boundaries.