Virtual Source Redatuming With Radiation Pattern Correction
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Solution Overview
Problem
Virtual source redatuming methods face repeatability issues in near-field land applications with complex near-surface structures, leading to interference and mismatched frequency content between downgoing and upgoing seismic wavefields, which deteriorate the quality of seismic images.
Innovation Solution
The method involves iterative estimation and application of a matched filter for an ideal amplitude spectrum of downgoing direct seismic wave energy arrivals in 3D space, combined with time-dependent smoothing and source array tapering, to enhance the approximation of an ideal P-wave downgoing wavefield and improve image quality by suppressing artifacts and crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If virtual source redatuming is applied in near-field land applications with complex near-surface structures, then surface source records can be redatumed to buried receiver locations, but repeatability issues arise due to near-surface complexity
Solution Approach 1:
The patent applies radiation pattern correction by modifying the amplitude spectrum parameters of the downgoing wavefield to match a target radiation pattern. This parameter transformation corrects the directional amplitude distribution, enabling consistent results across repeated surveys despite complex near-surface conditions. The correction involves calculating a correction factor based on the ratio of target to actual radiation patterns and applying it to the wavefield amplitudes.
2Measurement precision
If cross-correlation of downgoing and upgoing wavefields is performed, then time-lapse changes can be resolved, but interference and mismatched frequency content deteriorate image quality
Solution Approach 1:
The patent transforms the frequency content and amplitude distribution of the downgoing wavefield by applying radiation pattern correction in the frequency domain. This parameter modification ensures that the corrected downgoing wavefield has matched frequency content and appropriate amplitude distribution, reducing interference when cross-correlated with upgoing wavefields and improving seismic image quality.
3Manufacturing precision
If downgoing wavefield approximation is performed using traditional methods, then processing can be simplified, but artifacts and crosstalk reduce the accuracy of P-wave field representation
Solution Approach 1:
The patent applies radiation pattern correction to transform the amplitude spectrum of the downgoing wavefield, changing its parameter distribution to match the ideal P-wave radiation pattern. This parameter transformation suppresses artifacts and crosstalk by correcting the amplitude distribution, resulting in a more accurate representation of the P-wave field while maintaining computational feasibility.
Data Source
AI summary
Received shot gathers are sorted to a common receiver gather. A target three-dimensional (3D) amplitude spectrum of seismic wavefield direct arrivals is computed from synthetic data. A 3D amplitude spectrum of seismic wavefield direct arrivals in field data is computed for each receiver. A matched filter is calculated from the 3D amplitude spectrum of field data to target response and applied to downgoing seismic wavefields separated from the common receiver gather to generate filtered downgoing seismic wavefields. Time-dependent smoothing of the filtered downgoing seismic wavefields is performed to generate smoothed downgoing seismic wavefields. A cross-correlation is calculated between upgoing seismic wavefields separated from the common receiver gather and the smoothed downgoing seismic wavefields.