Fiber Optic DVS Directional Sensing via Wavenumber Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Fiber optic Distributed Vibration Sensing (DVS) systems lack directional sensitivity, making it difficult to distinguish between up and down waves in borehole or marine acquisition environments, and their measurements are not directly comparable to those from legacy systems like geophones, limiting their use in seismic surveys and reservoir monitoring.
Innovation Solution
The implementation of spatially distributed optical fiber sensors with specific patterns, such as serpentine or helically wound configurations, combined with spatial gradients and polarity masks, allows for directional interpretation of acoustic wavefields, enabling separation of orthogonal components and enhancing sensitivity to seismic data, thereby providing measurements comparable to traditional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard fiber optic DVS systems are used, then the system is simple and cost-effective, but the system lacks directional sensitivity and cannot distinguish between up and down waves
Solution Approach 1:
The fiber optic sensor is divided into multiple segments or sections, each capable of detecting vibrations independently. This segmentation allows the system to analyze vibration patterns from different spatial locations along the fiber, enabling directional discrimination by comparing phase and amplitude differences between adjacent segments.
Solution Approach 2:
The patent introduces asymmetric processing methods where the fiber optic sensor system treats upward and downward traveling waves differently through specialized signal processing algorithms. By applying asymmetric filtering and analysis techniques, the system can distinguish between waves traveling in opposite directions despite the inherent symmetry of the physical fiber optic medium.
2Adaptability or versatility
If fiber optic DVS systems are deployed in seismic surveys, then the system provides distributed sensing capability, but the measurements are not directly comparable to legacy geophone systems
Solution Approach 1:
The patent applies parameter transformation techniques to convert fiber optic DVS measurements into equivalent geophone responses. By adjusting key parameters such as frequency response characteristics, sensitivity calibration, and signal processing filters, the system transforms the raw fiber optic data into a format that matches the response characteristics of traditional geophone systems, enabling direct comparison and integration with legacy seismic data.
3Measurement precision
If spatially distributed optical fiber sensors with specific patterns are implemented, then directional interpretation of acoustic wavefields is enabled, but the device complexity increases
Solution Approach 1:
The patent employs serpentine or helical winding patterns of the fiber optic sensor, transforming the linear fiber into curved spatial configurations. These curved patterns allow the fiber to interact with acoustic wavefields from multiple directions, enabling directional interpretation by analyzing vibration patterns along the curved path. The serpentine and helical geometries effectively convert a simple linear sensor into a multi-directional sensing array without requiring multiple separate sensors.
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
These configurations enable the DVS systems to distinguish between directional components of acoustic wavefields, improving the accuracy of seismic data collection and reservoir monitoring by providing measurements that are more comparable to legacy systems, thus enhancing the understanding of subsurface properties.
Implementation Method 1
Fiber optic sensors employ the fact that environmental effects, such as pressure, strain, vibration, and temperature, can alter the amplitude, phase, frequency, spectral content, or polarization of light propagated through an optical fiber
Data Source
AI summary
An apparatus and method for correcting the wavenumber sensitivity of a distributed fiber optic sensor are disclosed. The distributed fiber optic sensor is deployed in a region of interest to measure a characteristic of an incident acoustic wavefield. A composite response of the distributed sensor is determined based on backscatter optical signals generated by the sensor, where the composite response is indicative of a characteristic of an incident acoustic wavefield. The composite response includes at least a first response having a first wavenumber sensitivity and a second response having a second wavenumber sensitivity. The second wavenumber sensitivity is selected so that wavenumber notches of the first and second responses do not overlap.