Seismic Noise Image Calculation for Sub-Salt Migration
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Solution Overview
Problem
Seismic data migration methods, particularly Kirchhoff migration, struggle to effectively suppress spurious events and noise in complex subsurface environments like sub-salt geological settings where multiple ray paths and diffraction occur, leading to image distortion and reduced accuracy in identifying true reflectors.
Innovation Solution
A method involving multicomponent seismic data processing to calculate a noise image by determining wavefield components, using a velocity model, and generating products from these components to differentiate between noise and true reflector images, effectively suppressing spurious events through difference calculations and summations over multiple receivers and frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Kirchhoff migration is used to process seismic data, then computational efficiency is improved, but image accuracy deteriorates due to spurious events and migration smiles
Solution Approach 1:
The patent segments the seismic data processing into multiple components: separating P-wave and S-wave components, handling different ray paths independently, and processing multiple frequencies separately. This segmentation allows each component to be processed optimally while maintaining computational efficiency, resolving the contradiction between speed and accuracy.
Solution Approach 2:
The patent changes key parameters in the migration process: using variable density stacking instead of uniform stacking, adjusting the stacking operator to account for multiple ray paths, and modifying the migration operator to handle both P and S waves. These parameter changes enable Kirchhoff migration to achieve both efficiency and accuracy.
2Device complexity
If a single ray path is considered in Kirchhoff migration, then computational complexity is reduced, but reliability deteriorates in sub-salt environments with multi-pathing
Solution Approach 1:
The patent introduces dynamic elements to the migration process: the stacking operator adapts to different ray paths dynamically, the migration operator adjusts to handle multiple P and S wave components, and the process automatically selects the correct wave propagation path based on the data. This dynamic approach maintains reliability without excessive complexity.
Solution Approach 2:
The patent creates a universal migration operator that can handle multiple types of waves (P and S waves), multiple ray paths, and different geological conditions (including sub-salt environments) within a single framework. This multi-functionality improves reliability across diverse scenarios without proportionally increasing complexity.
3Measurement precision
If multicomponent seismic data is processed to suppress noise, then image quality is improved, but processing time increases
Solution Approach 1:
The patent performs preliminary actions by pre-calculating the stacking operator and migration operator based on the velocity model and ray path information. These operators are prepared in advance and then applied efficiently to the actual data processing, reducing the overall processing time while maintaining high image quality through the multicomponent analysis.
Data Source
AI summary
A method of calculating a seismic noise image for a formation comprises the steps of: a) obtaining data representing a multicomponent seismic signal from at least one receiver, in response to transmitting seismic waves into the formation; b) obtaining a velocity model of the earth formation; c) determining a plurality of wave field components; d) obtaining a set of second components; e) obtaining, for each subsurface point, at least two products, each product comprising the product of a selected wave field component and a different second component; and f) and generating a noise image by calculating at least one difference between different products for at least one image point.