Pseudo-random seismic sweep noise attenuation
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Solution Overview
Problem
Current seismic data acquisition methods require repetitive measurements for noise attenuation using the diversity stack technique, which is costly and inefficient.
Innovation Solution
The use of pseudo-random frequency sweep signals for seismic data acquisition allows for noise attenuation on a pre-phase subtraction basis without the need for repetitive measurements, leveraging the characteristic that pseudo-random sweeps do not exhibit spectral notching when muted, thus enabling effective noise reduction without damaging the spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the diversity stack technique is used for noise attenuation, then noise is reduced, but repetitive measurements are required which increases cost and reduces efficiency
Solution Approach 1:
The patent changes the fundamental parameter of the sweep signal from a conventional sine-wave or linear frequency sweep to a pseudo-random frequency sweep. This parameter change enables the signal to maintain spectral integrity when muted, allowing noise attenuation through pre-phase subtraction without requiring repetitive measurements. The pseudo-random nature of the sweep creates unique spectral characteristics that prevent notching effects, thereby resolving the contradiction between noise reduction and operational efficiency.
2Object-affected harmful factors
If conventional sweep signals are muted for noise attenuation, then noise is reduced, but spectral notching damages the data spectrum
Solution Approach 1:
The patent applies parameter changes by transforming the sweep signal from a conventional linear frequency modulation to a pseudo-random frequency modulation. This change in the frequency modulation parameter ensures that when the signal is muted or windowed for noise attenuation, the spectral content remains intact without producing notching artifacts. The pseudo-random phase progression maintains spectral uniformity across the frequency band, thereby preserving spectral integrity while enabling effective noise reduction.
Solution Approach 2:
The patent introduces an intermediary processing step of pre-phase subtraction using the pseudo-random sweep signature before the correlation process. This intermediary action allows noise to be attenuated in the pre-processing stage without directly affecting the final spectral content after correlation. The pseudo-random sweep acts as a unique identifier that enables this intermediary noise attenuation step to proceed without damaging the spectral information, as the correlation process subsequently restores the full spectral content.
3Object-affected harmful factors
If repetitive measurements are performed for diversity stacking, then noise attenuation is achieved, but operational costs increase
Solution Approach 1:
The patent fundamentally changes the sweep signal parameter to pseudo-random frequency modulation, which enables noise attenuation through a single measurement rather than requiring multiple repetitive measurements for diversity stacking. The pseudo-random characteristics of the sweep create sufficient signal differentiation that allows noise to be attenuated through pre-phase subtraction from a single data set. This parameter change eliminates the need for repetitive measurements, thereby reducing operational costs while maintaining effective noise attenuation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively attenuates noise in seismic data without the need for repetitive measurements, maintaining the integrity of the seismic data spectrum and reducing operational costs.
Implementation Method 1
seismic waves generated for the imaging of geological layers have been used for more than 50 years. The most widely used waves are reflected waves and more precisely reflected compressional waves
Implementation Method 2
leveraging the characteristic that pseudo-random sweeps do not exhibit spectral notching when muted
Data Source
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AI summary
A method for attenuating noise in seismic data signals is described wherein seismic signals are transmitted using a pseudo-random frequency sweep signal. Noise is then attenuated from the resulting, acquired seismic data on pre-phase subtraction basis, e.g., before correlating or de-convolving the acquired seismic data. In this way, repetitions associated with, for example, diversity stacking techniques can be avoided.