DAS VSP Gauge Length Deconvolution for Seismic Wavefield Recovery
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Solution Overview
Problem
Distributed Acoustic Sensing (DAS) technology for vertical seismic profiling (VSP) is sensitive to environmental and survey parameters, leading to degraded signal quality due to noise, which affects the signal-to-noise ratio (SNR) and resolution of data, necessitating downsampling techniques to improve SNR and maintain high resolution and broad spectrum.
Innovation Solution
The method involves processing and controlling VSP surveys to invert wavefields free of gauge length effects, predicting wavefields of arbitrary lengths, and optimizing gauge length during acquisition to enhance signal quality and bandwidth, using techniques such as Fourier transforms and low-pass filtering in the wavenumber domain to compensate for gauge length-induced attenuation factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DAS technology is used for VSP with fine channel spacing and high data acquisition rates, then measurement precision and data density are improved, but signal quality degrades due to sensitivity to environmental parameters and noise
Solution Approach 1:
The patent extracts and removes the gauge length effect from the DAS VSP data through deconvolution processing. By separating the gauge length attenuation factor from the recorded wavefield, the method recovers the underlying signal that would have been obtained with infinitesimal gauge length, thereby eliminating the degradation caused by finite gauge length while preserving the high measurement precision of DAS technology.
Solution Approach 2:
The patent changes the gauge length parameter dynamically through computational processing. Instead of being constrained by the physical gauge length used during acquisition, the method computationally transforms data to represent multiple gauge length values, including effectively zero gauge length, thereby adapting the measurement parameter post-acquisition to optimize signal quality.
2Object-affected harmful factors
If downsampling technique is applied to improve SNR, then signal quality is improved, but resolution and spectrum breadth are compromised
Solution Approach 1:
The patent changes the gauge length parameter dynamically through computational processing. Instead of being constrained by the physical gauge length used during acquisition, the method computationally transforms data to represent multiple gauge length values, including effectively zero gauge length, thereby adapting the measurement parameter post-acquisition to optimize signal quality.
Solution Approach 2:
The patent combines data from multiple gauge length measurements into a composite representation through deconvolution. By integrating information from measurements taken with different gauge lengths and processing them through a unified mathematical model, the method creates a composite wavefield that simultaneously achieves high signal-to-noise ratio and high resolution, avoiding the trade-off inherent in simple downsampling.
3Object-affected harmful factors
If gauge length is increased to improve signal quality, then SNR is improved, but bandwidth is reduced due to gauge length effect
Solution Approach 1:
The patent extracts and removes the gauge length effect from the DAS VSP data through deconvolution processing. By separating the gauge length attenuation factor from the recorded wavefield, the method recovers the underlying signal that would have been obtained with infinitesimal gauge length, thereby eliminating the degradation caused by finite gauge length while preserving the high measurement precision of DAS technology.
Solution Approach 2:
The patent applies preliminary anti-action by pre-compensating for the gauge length attenuation effect through deconvolution. The method calculates the inverse of the gauge length transfer function and applies it to the recorded data, thereby counteracting the bandwidth-limiting effect before further processing, ensuring that the full bandwidth information is preserved and recoverable.
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 improves signal quality, extends bandwidth, and provides a guideline for survey design, enabling advanced quality of DAS VSP data by removing gauge length effects and predicting wavefields of arbitrary lengths, thus enhancing noise resistance and data accuracy.
Implementation Method 1
Rayleigh scattering from random heterogeneities in the optical fiber of the cable is the primary mechanism of back propagation of laser beams for interrogation, where the optical fiber is an optical waveguide. Phase difference of the demodulated back-scattered light is introduced when the optical fiber is deformed by impinging seismic waves.
Data Source
AI summary
Various embodiments include apparatus and methods implemented to take into consideration gauge length in optical measurements. In an embodiment, systems and methods are implemented to interrogate an optical fiber disposed in a wellbore, where the optical fiber is subjected to seismic waves, and to generate a seismic wavefield free of gauge length effect and/or to generate a prediction of a seismic wavefield of arbitrary gauge length, based on attenuation factors of a plurality of wavefields acquired from interrogating the optical fiber. In an embodiment, systems and methods are implemented to interrogate an optical fiber disposed in a wellbore, where the optical fiber is subjected to seismic waves, and to convert a seismic wavefield associated with a first gauge length to a seismic wavefield associated with a different gauge length that is a multiple of the first gauge length. Additional apparatus, systems, and methods are disclosed.