Seismic Sweep Signal Generation via Time-Shifted Perturbation
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Solution Overview
Problem
Current seismic data acquisition methods using seismic vibrators face challenges in simultaneous shooting due to crosstalk, which complicates source separation and introduces intermodulation distortion noise, making it difficult to distinguish individual reflections and control the energy distribution effectively.
Innovation Solution
Generating sweep signals with instantaneous frequency modulation, where a nominal sweep signal is perturbed to create pseudo-orthogonal signals for each seismic source, allowing for better source separation and reduced noise artifacts, while being easier to control and process than pseudo-random signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pseudo-random signals are used for simultaneous shooting, then source separation is improved, but intermodulation distortion noise increases and control difficulty increases
Solution Approach 1:
The patent changes the temporal parameters of the sweep signals by applying different time shifts to each source's sweep signal. Instead of using complex pseudo-random sequences, the invention modifies the timing parameters of simple linear sweeps, creating pseudo-orthogonal signals that separate cleanly in the time domain while maintaining smooth frequency modulation that avoids intermodulation distortion.
2Measurement precision
If pseudo-random signals are used for simultaneous shooting, then source separation is improved, but device complexity and control difficulty increase
Solution Approach 1:
The invention simplifies the control system by changing from complex pseudo-random signal generation to simple time-shifted linear sweeps. The controller only needs to manage timing parameters rather than generating and coordinating complex pseudo-random sequences, significantly reducing computational requirements and control complexity while maintaining effective source separation.
3Ease of operation
If traditional sweep signals are used, then ease of control is maintained, but orthogonality between sources deteriorates during simultaneous shooting
Solution Approach 1:
The patent segments the time domain by assigning different time shifts to each source's sweep signal. This temporal segmentation creates distinct time windows for each source, ensuring orthogonality while maintaining the simplicity of linear sweep generation. Each source operates in its designated time segment, preventing signal interference.
Solution Approach 2:
The invention employs periodic time-shifted sweep sequences where each source repeats its sweep pattern at different time offsets. This periodic structure with time shifts ensures that sources remain orthogonal across multiple shots while keeping the control mechanism simple and regular, avoiding the need for complex aperiodic pseudo-random sequences.
Data Source
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AI summary
Computing device, computer software and methods for generating sweep signals corresponding to plural sources that generate seismic waves. The method includes selecting (502) a nominal sweep signal (S0); applying (512) a perturbation (P) to the nominal sweep signal (S0); and calculating (518) the sweep signals (Sn) by varying the perturbation (P), each sweep signal corresponding to a seismic source.