Velocity Tomography Residual Depth Error Reconstruction
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Solution Overview
Problem
Existing methods for building subsurface velocity models from seismic reflection data face challenges in complex imaging areas, such as sub-salt regions, due to inaccurate formulations and instability in kinematic demigration/remigration processes, which hinder reliable measurement of residual depth errors.
Innovation Solution
A method is developed to directly reconstruct residual depth errors from velocity scans using a derived formula, allowing for improved velocity model updates through tomographic inversion, where the formula reconstructs residual depth errors as Dzm = DA(vm−vf), with DA being a matrix built from ray tracing and used in the tomographic inversion workflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If kinematic demigration/remigration is used to convert velocity scans into RDE, then velocity model updating can be performed, but the process becomes complicated and stability and accuracy are difficult to achieve
Solution Approach 1:
The patent extracts only the essential information needed for velocity model updating by directly measuring residual depth errors (RDE) from velocity scan panels, eliminating the need for complex kinematic demigration and remigration processes. This extraction approach obtains RDE values directly from the scan data without requiring full conversion through complicated intermediate steps, thereby simplifying the workflow while maintaining updating reliability.
Solution Approach 2:
Instead of converting velocity scans into RDE through complex forward processes (demigration/remigration), the patent inverts the approach by directly measuring RDE from the velocity scan panels. This inversion simplifies the measurement process by working backwards from the final desired output (RDE values) rather than forwards through complicated transformations.
2Ease of manufacture
If 1D vertical updating method is used to update velocity model from scans, then the process is simplified, but the formulation becomes inaccurate for complex structures where 1D assumption is invalid
Solution Approach 1:
The patent applies local quality by measuring residual depth errors at each individual image point independently from velocity scan panels. Instead of applying a uniform 1D assumption across the entire subsurface volume, the method allows each location to have its own locally-optimized RDE measurement based on the velocity scan data at that specific point, thereby achieving both simplicity and local accuracy.
Solution Approach 2:
The patent changes the measurement parameter from assuming a uniform 1D velocity structure to directly measuring RDE values at each image point from velocity scan panels. This parameter change allows the method to adapt to local velocity variations in complex structures while maintaining the simplicity of direct measurement, effectively transitioning from a global 1D assumption to local parameter optimization.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides a more reliable estimation of residual depth errors in complex imaging areas, enhancing the accuracy and stability of velocity model updates, thereby improving the effectiveness of velocity tomography.
Implementation Method 1
A is a matrix built from ray tracing
Data Source
AI summary
Method for building a subsurface model of velocity or other elastic property from seismic reflection data using tomography. The method uses velocity scans to pick a focusing velocity model at each image point (40). The focusing velocities are used to pick depth errors from tables (60) generated using a tomographic inversion matrix (30) and a suite of different velocity models (10). The depth errors are then reconstructed at each image point from the velocity scans based on the difference between the base velocity model and the most coherent velocity from the scan (70). The reconstructed depth errors are used to compute the velocity model update (80).