Vibratory Seismic Source Pilot Signal Low-Frequency Boost
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Solution Overview
Problem
Current seismic vibratory sources face constraints that limit their frequency output, particularly with pseudo-random pilot sweeps, leading to reduced energy content and potential system overdrive, which complicates subsurface imaging and requires methods to boost low- and high-frequency content without exceeding system limits.
Innovation Solution
A method involving a computing device to generate a pilot signal by scaling, level compressing, and transforming the signal in both force and displacement domains to account for stroke limits, thereby boosting the low-frequency end and redistributing high-frequency demand to maintain system compliance and maximize energy content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional linear sweeps are used to image the subsurface, then adequate frequency coverage can be achieved given enough sweep time, but the productivity is reduced due to very long sweep times or many shots required at each location
Solution Approach 1:
The patent applies non-linear sweep designs that dynamically adjust the frequency progression rate across different frequency bands. By varying the sweep rate non-uniformly across the frequency spectrum, the system achieves optimized energy distribution and improved subsurface imaging without requiring excessively long sweep times, thus resolving the contradiction between imaging quality and productivity
Solution Approach 2:
The patent modifies sweep parameters including frequency progression rate, sweep duration, and amplitude modulation characteristics to create optimized sweep designs. By changing these parameters non-uniformly across different frequency bands, the system achieves both adequate frequency coverage for imaging and reduced sweep times for improved productivity
2Quantity of substance
If pseudo-random pilot sweeps are used with vibratory sources, then frequency content can be generated, but system constraints impose frequency-variant limits on output amplitude spectrum that reduce energy content
Solution Approach 1:
The patent applies level compression techniques that selectively reduce amplitude in frequency bands where system constraints are most restrictive, while maintaining or enhancing amplitude in bands where the system can handle higher energy. This partial action approach ensures system compliance is maintained while maximizing energy content in permissible frequency ranges
Solution Approach 2:
The patent dynamically adjusts pilot signal parameters including amplitude, frequency progression, and temporal characteristics to match system constraints across different frequency bands. By changing these parameters adaptively, the system maximizes energy output while ensuring compliance with operational limits
3Quantity of substance
If sweep amplitude is increased to boost low-frequency content, then low-frequency energy is enhanced, but the vibratory source may reach stroke limitations and be overdriven
Solution Approach 1:
The patent applies different amplitude modulation characteristics and level compression factors to different frequency bands within the pilot signal. By applying local quality variations across the frequency spectrum, the system enhances low-frequency energy content while applying appropriate amplitude control in frequency bands where stroke limitations are more critical, thus maintaining reliability
Solution Approach 2:
The patent performs preliminary analysis of system constraints and pre-computes level compression factors and amplitude adjustments before generating the pilot signal. This preliminary action ensures that the pilot signal is designed to enhance low-frequency content while pre-emptively avoiding stroke limitations and overdrive conditions
Data Source
AI summary
Computer software, computer and method for generating with a computing device a desired pilot signal for driving a vibratory source to generate seismic waves. The method includes steps for compressing a pilot signal in a force domain and also compressing a mass displacement in a displacement domain. The resulting desired pilot signal boosts the low-frequency end of the vibratory source.