Distributed Acoustic Sensing Gauge Length Artifact Mitigation
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Solution Overview
Problem
Distributed Acoustic Sensing (DAS) systems face challenges in accurately measuring strain changes along optical fibers due to gauge length effects, which can introduce artifacts such as reverberations and signal attenuation, particularly in seismic data collection.
Innovation Solution
Applying de-convolution operations in the Z-transform or Fourier transform domain to DAS data, and combining data from different gauge lengths to average out artifacts, using weighted averaging to minimize truncation effects and enhance signal fidelity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DAS systems measure disturbances at different distances along the fiber length, then spatial detection of acoustic disturbances is achieved, but artifacts such as reverberations and signal attenuation are introduced
Solution Approach 1:
The patent extracts and removes the harmful artifacts (reverberations and signal attenuation) from the DAS measurement data through deconvolution operations. By identifying the artifact components in the frequency domain and selectively eliminating them, the system retains the useful acoustic information while removing the detrimental effects introduced by gauge length measurements.
Solution Approach 2:
The patent introduces deconvolution operations as an intermediary processing step between data acquisition and final analysis. This intermediary process acts as a filter that separates useful signal from harmful artifacts, using mathematical transformations (Fourier or Z-transform) to identify and remove artifact components while preserving genuine acoustic disturbances.
2Object-generated harmful factors
If de-convolution operations are applied to DAS data, then artifacts are reduced, but signal-to-noise ratio may deteriorate
Solution Approach 1:
The patent applies partial deconvolution by selectively removing only the artifact components (reverberations and signal attenuation) identified through transform operations, rather than attempting complete inversion. This partial action approach removes harmful artifacts while avoiding excessive processing that would amplify noise and degrade the signal-to-noise ratio.
Solution Approach 2:
The patent transforms the DAS data into different domains (Fourier or Z-transform) where artifact parameters can be identified and separated from signal parameters. By changing the representation domain, the system can selectively modify artifact characteristics while preserving signal integrity, then transform back to obtain cleaned data with maintained signal-to-noise ratio.
3Length of stationary object
If gauge length is increased to improve signal detection, then measurement range is extended, but spectral fidelity is reduced
Solution Approach 1:
The patent replaces the mechanical constraint of fixed gauge length with a computational solution. Instead of being limited by the physical gauge length setting, the system uses deconvolution operations in the frequency domain to correct the spectral fidelity degradation. This substitution allows the system to maintain longer gauge lengths for extended measurement range while computationally restoring the spectral information that would otherwise be lost.
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
The proposed solution effectively reduces artifacts and improves the fidelity of seismic data collected by DAS systems, restoring amplitude and wavelet shapes closer to the original seismic information, while maintaining suitable signal-to-noise ratios.
Implementation Method 1
Acoustic sensing based on DAS may use the Rayleigh backscatter property of a fiber's optical core and may spatially detect disturbances that are distributed along the fiber length
Implementation Method 2
To measure the phase changes, measurements of light signals from two different points along the fiber are taken to determine an average amount of strain over that distance
Data Source
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AI summary
A system includes a light source, optical fiber coupled to the light source, one or more interferometers coupled to the optical fiber, wherein each interferometer of the one or more interferometers comprising a gauge length, a photodetector assembly coupled to the optical fiber, and an information handling system. The photodetector assembly is configured to detect backscattered light from the optical fiber and generate signals based on the detected backscattered light. The an information handling system is configured to receive the signals from the photodetector assembly, apply a de-convolution operation to the signals based on the gauge lengths of the one or more interferometers, and store the de-convolved signals.