Strain Detection in Fiber Optic Cables via Narrowband Signals
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Solution Overview
Problem
In the oil and gas industry, measuring the characteristics of substances in remote subterranean locations and transmitting these measurements to the surface is challenging due to the need for high-frequency data capture over long distances, which existing technologies have not effectively addressed without requiring new tools or adaptations.
Innovation Solution
The system employs high-frequency instruments to measure wellbore properties and uses low-frequency instruments for data transmission, decoupling measurement and transmission frequencies, allowing for advanced examinations without the need for new tools or hardware adaptations, utilizing transmitters, optical waveguides, and interferometry techniques to detect and process signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-frequency instruments are used to measure wellbore properties, then measurement precision and data accuracy are improved, but device complexity and cost increase due to the need for specialized equipment
Solution Approach 1:
The patent transforms the high-frequency measurement problem into a low-frequency transmission problem by changing the frequency parameter. The narrowband signal at high frequency is modulated onto a low-frequency carrier wave, allowing the measurement information to be transmitted at low frequency where existing optical fiber infrastructure can handle it, thus avoiding the need for complex high-frequency transmission equipment while maintaining measurement precision
Solution Approach 2:
The patent introduces an intermediary modulation process where the high-frequency measurement signal is transferred to a low-frequency carrier wave. This intermediary step allows the separation of measurement function (high frequency) from transmission function (low frequency), enabling the use of simple existing transmission infrastructure while maintaining high measurement capabilities
2Productivity
If high-frequency signals are transmitted over long distances, then data capture frequency is improved, but signal attenuation and transmission loss increase
Solution Approach 1:
The patent changes the transmission frequency parameter from high to low, exploiting the physical principle that lower frequency signals experience less attenuation in optical fibers. The high-frequency measurement information is encoded onto a low-frequency carrier, enabling long-distance transmission with minimal signal loss while preserving the original high-frequency measurement capability at the source
3Device complexity
If existing low-frequency tools are used for high-frequency measurements, then device complexity is reduced, but measurement precision deteriorates due to insufficient sampling rate
Solution Approach 1:
The patent employs periodic modulation where the high-frequency narrowband signal is modulated onto a low-frequency carrier wave at regular intervals. This periodic action allows the high-frequency information to be embedded in a low-frequency signal that can be sampled at lower rates using existing tools, while the original high-frequency characteristics are preserved through the modulation envelope
Solution Approach 2:
The patent creates a low-frequency copy or representation of the high-frequency measurement signal through modulation. This copied signal contains all the essential measurement information but at a frequency suitable for existing low-frequency instrumentation, effectively allowing existing tools to perform high-frequency measurements through intelligent signal processing
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 enables efficient high-frequency examination of wellbore characteristics using existing low-frequency tools, facilitating applications like flow detection and cement cure monitoring without the need for new equipment, thereby reducing costs and improving data accuracy.
Implementation Method 1
interferometry techniques to detect and process signals
Implementation Method 2
interferometric phase modulation techniques
Data Source
AI summary
A method may include transmitting a narrowband signal into a formation using a transmitter located in a wellbore. The narrowband signal is modified by passage of through the formation and the formation reflects at least a portion of the narrowband signal back to the wellbore resulting in a modified narrowband signal having a first frequency. The method also includes sensing the modified narrowband signal with an optical waveguide positioned in the wellbore, transmitting a source signal along a length of the optical waveguide, and obtaining a backscattered return signal from the optical waveguide. The backscattered return signal is sampled at a second frequency that is less than the Nyquist rate of the modified narrowband signal. The method further includes processing the backscattered return signal to obtain an amplitude of the modified narrowband signal.