Shared Fiber-Optic Cable for Simultaneous Temperature and Strain Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Measuring strain and temperature in a wellbore using a fiber-optic cable is challenging due to the interference between temperature and strain responses, requiring disambiguation and often necessitating separate instruments optimized for different wavelengths, which complicates fiber characterization and alignment.
Innovation Solution
Employing multiple frequency or phase shift measurement techniques over a shared fiber-optic cable using interrogator instruments that differentiate between temperature and strain changes through linearly independent sensitivity ratios, allowing for unambiguous outputs by combining Brillouin-shift and Rayleigh-based relative frequency shifts on a single optical fiber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate DTS and Brillouin instruments are used for temperature and strain measurement, then measurement precision is improved, but device complexity increases due to requiring multiple optical fibers and wavelength alignment
Solution Approach 1:
The patent combines temperature sensing (DTS) and strain sensing (Brillouin) measurements into a single optical fiber cable. The fiber cable contains both multi-mode and single-mode fibers that carry signals for both measurement techniques, eliminating the need for separate fiber cables and reducing overall system complexity while maintaining measurement precision
Solution Approach 2:
The optical fiber cable is designed to serve multiple functions simultaneously: it acts as both the transmission medium for DTS temperature measurements and for Brillouin strain measurements. The cable structure supports both multi-mode and single-mode fibers, making it a universal solution for dual-parameter sensing in wellbore applications
2Measurement precision
If DTS and Brillouin instruments operate at different wavelengths (1064 nm and 1550 nm), then measurement accuracy is improved, but ease of operation deteriorates due to fiber characterization and depth alignment difficulties
Solution Approach 1:
The patent merges multiple wavelength operations into a single fiber cable infrastructure. The cable simultaneously supports 1064 nm wavelength for DTS temperature measurements and 1550 nm wavelength for Brillouin strain measurements, along with 1550 nm for distributed acoustic sensing. This unified approach simplifies deployment and depth alignment compared to using separate cables for each wavelength
3Device complexity
If a single fiber-optic cable is used for both temperature and strain measurement, then device complexity is reduced, but measurement precision deteriorates due to temperature-strain response interference
Solution Approach 1:
The patent segments the optical fiber cable into different fiber types with distinct characteristics. It includes both multi-mode fiber (for DTS temperature sensing) and single-mode fiber (for Brillouin strain sensing) within the same cable construction. This segmentation allows each fiber type to be optimized for its specific measurement function while being deployed together, reducing cross-interference and maintaining measurement precision
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
Enables accurate and simultaneous measurement of strain and temperature changes along the wellbore using a single fiber, improving the precision and efficiency of wellbore operations by controlling parameters such as hydraulic fracturing fluid pressure and proppant concentration.
Implementation Method 1
A 'Brillouin shift' instrument can measure shift in Brillouin frequency. The Brillouin shift instrument can be used for measuring changes in strain in the wellbore
Implementation Method 2
Temperature may be measured using Raman-based distributed temperature sensing (DTS)
Implementation Method 3
Detecting multiple different types of information using the same fiber-optic cable
Data Source
AI summary
A well system includes a fiber-optic cable that can be positioned downhole along a wellbore. The well system further includes a plurality of opto-electrical interfaces to communicatively couple to the fiber-optic cable to monitor temperature and strain along the fiber-optic cable. Additionally, the well system includes a processing device and a memory device that includes instructions executable by the processing device to cause the processing device to perform operations. The operations include receiving data representing frequency or phase shift measurements from the opto-electrical interfaces using at least two frequency or phase shift measurement techniques. Further, the operations include generating a temperature shift output and a strain change output using an inversion comprising sensitivity ratios and the data representing the frequency or phase shift measurements from the plurality of opto-electrical interfaces.