Varying Sensor Reflectivity in Fiber Optic Wellbore Arrays
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Solution Overview
Problem
In oil exploration and production, fiber optic cables with multiple sensors experience significant multi-path ringing noise, which complicates signal interpretation and reduces the signal-to-noise ratio, making it difficult to accurately measure parameters like strain and temperature in wellbores.
Innovation Solution
Configuring the reflectivity values of sensors within the fiber optic cable such that they vary along the cable, with lower reflectivity closer to the light source and higher reflectivity farther away, or in a specific pattern related to distance, to minimize multi-path interference and enhance the signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensors are evenly spaced in the fiber optic cable, then the sensing coverage is uniform, but multi-path ringing noise becomes significant and reduces signal-to-noise ratio
Solution Approach 1:
The patent applies local quality by assigning different reflectivity values to different sensors based on their positions in the fiber optic cable. Sensors closer to the light source have lower reflectivity values, while sensors farther away have higher reflectivity values. This localized differentiation in reflectivity properties eliminates the uniformity that causes multi-path ringing, thereby reducing noise and improving signal-to-noise ratio without compromising sensing coverage.
2Ease of manufacture
If all sensors have the same reflectivity value, then the system is simpler to manufacture, but signal interpretation becomes complicated due to indistinguishable ringing signals
Solution Approach 1:
The patent changes the reflectivity parameter of sensors from a uniform value to a position-dependent value. By making reflectivity a variable parameter that changes with sensor position, the system achieves distinguishable signal characteristics that facilitate signal interpretation while maintaining relatively simple manufacturing processes through programmed reflectivity assignment during sensor fabrication or deployment.
3Illumination intensity
If reflectivity values are increased to enhance signal strength, then signal detection improves, but multi-path interference increases and degrades measurement accuracy
Solution Approach 1:
The patent applies local quality by implementing position-dependent reflectivity values that balance signal strength and interference reduction. Sensors at different positions have optimized reflectivity values tailored to their specific locations, ensuring adequate signal strength for detection while minimizing the generation of multi-path interference that would otherwise degrade measurement accuracy.
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 configuration effectively reduces noise interference, improving the signal-to-noise ratio and allowing for more accurate measurement of parameters like strain and temperature by minimizing multi-path interference and enhancing the clarity of signals received from the sensors.
Implementation Method 1
a light source at a surface location supplies light to the optical sensors via a fiber optic cable
Implementation Method 2
Light interacts with the plurality of optical sensors to produce a reflected light having a signal that is returned to the surface location to be measured
Data Source
AI summary
A method, system and apparatus for obtaining a parameter of interest relating to a wellbore is disclosed. A fiber optic cable having a plurality of sensors is disposed in the wellbore, wherein the plurality of sensors have reflectivity values configured to provide improved signal-to-noise ratio compared to signal-to-noise ratio of a plurality of sensors having substantially same reflectivity values. Light is propagated into the fiber optic cable from a light source and signals are received at a detector from the plurality of sensors in response to interaction of the propagated light with the plurality of sensors. A processor may be used to obtain the parameter of interest from the received signals. The fiber optic cable may be coupled to a member in the wellbore, wherein the parameter of interest is related to the member.