Reverse-Time Migration Using Directional Receiver Wavefields
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Solution Overview
Problem
Conventional reverse-time migration techniques for marine vertical cable seismic (VCS) survey data face challenges in producing high-quality migration images due to reflection boundary screening caused by long-wavelength artifacts, which are exacerbated by the deep placement of receivers, leading to image noise and complexity in the migration process.
Innovation Solution
The method employs directional propagation of receiver wavefields using equation-of-motion-based transform and inverse-transform processing on observed pressure wavefields as virtual sources during back-propagation, eliminating the need for up/down wavefield separation to enhance image quality and simplify the migration process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional reverse-time migration techniques are applied to VCS survey data, then the migration process can be performed, but long-wavelength artifacts appear that screen reflection boundaries and reduce image quality
Solution Approach 1:
The wavefield is segmented into upgoing and downgoing components using up/down wavefield separation. This separates the primary reflections (upgoing) from receiver ghosts (downgoing), allowing selective use of wavefield components that minimize long-wavelength artifacts while preserving reflection boundary information.
Solution Approach 2:
Different wavefield components are assigned different roles in the migration process. Primary reflections are used for imaging reflection boundaries while receiver ghosts are used for other purposes, optimizing the contribution of each component to overall image quality and artifact reduction.
2Object-generated harmful factors
If up/down wavefield separation is applied to extract receiver ghosts, then long-wavelength artifacts are reduced, but primary reflection signals with narrow reflection angles are removed causing weak image values
Solution Approach 1:
The wavefield separation process is optimized by adjusting separation parameters and frequency thresholds to preserve primary reflection signals with narrow reflection angles while still effectively removing receiver ghosts. This balances artifact reduction with preservation of useful imaging information.
3Object-generated harmful factors
If up/down wavefield separation is performed to solve artifact problems, then long-wavelength artifacts are reduced, but the migration process becomes more complex
Solution Approach 1:
Up/down wavefield separation is performed as a preliminary step before migration to pre-process the data and remove harmful artifacts. This separates the artifact reduction task from the main migration process, making each step more focused and potentially simplifying the overall workflow despite the additional separation step.
Data Source
AI summary
The present disclosure relates to a reverse-time migration method for marine vertical cable seismic (VCS) survey data and provides a reverse-time migration apparatus and method for vertical cable seismic (VCS) survey data using directional propagation of receiver wavefields, configured to perform equation-of-motion-based transform and inverse-transform processing on observed pressure wavefields during back-propagation of receiver wavefields to solve the problem of reflection boundary screening due to long-wavelength artifacts and avoid up/down wavefield separation to thereby simplify a migration process and improve overall quality of migration images.