Marine Seismic Wavefield Separation Using Ray-Aligned Velocity Data
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Solution Overview
Problem
Conventional methods for separating up-going and down-going wavefield components in marine seismic surveys require dense spatial sampling and knowledge of incidence angles, leading to decreased signal-to-noise ratio and aliasing issues, especially at higher angles.
Innovation Solution
The method involves rotating three-axis velocity data to conform to a ray direction associated with plane wave representation, applying plane wave decomposition, and combining pressure and decomposed velocity data to generate up-going and down-going wavefields without relying on incidence angles, thereby maximizing signal-to-noise ratio and reducing aliasing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods use dense spatial sampling and incidence angle corrections to separate up-going and down-going wavefield components, then measurement precision is improved, but device complexity and processing difficulty increase
Solution Approach 1:
The patent extracts and removes the incidence angle parameter from the wavefield separation process. By using three-component velocity data that directly provides particle motion direction, the method eliminates the need for incidence angle calculations and dense spatial sampling, thereby reducing system complexity while maintaining separation accuracy
Solution Approach 2:
The patent replaces the conventional mechanical/spatial sampling approach with a vector-based mathematical approach. Instead of relying on dense spatial sampling and incidence angle corrections, the method uses three-component velocity vectors to directly determine wavefield direction, substituting a simpler computational system for a complex spatial sampling system
2Measurement precision
If conventional methods rely on incidence angles for wavefield separation, then measurement precision is maintained, but signal-to-noise ratio decreases
Solution Approach 1:
The patent substitutes the incidence angle-based separation method with a direct three-component velocity vector method. By using the velocity vector direction to identify wavefield components, the method avoids the signal degradation associated with incidence angle calculations, particularly at higher angles, thereby preserving signal-to-noise ratio while maintaining separation precision
Solution Approach 2:
The patent changes the fundamental parameter used for wavefield separation from incidence angles to three-component velocity vectors. This parameter change eliminates the need for angle corrections that degrade signal quality, allowing accurate separation to be achieved without the signal-to-noise penalty inherent in conventional angle-based methods
Data Source
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AI summary
Three-axis velocity data, obtained along with pressure data in a marine seismic survey, are rotated to a ray direction. Plane wave decomposition is applied in the ray direction to the rotated velocity data. The pressure data and the velocity data are combined to generate at least one of up-going and down-going wave fields. The at least one of up-going and down-going wave fields are used in a time-space domain to image the earth's subsurface.