Hybrid DTS and phi-OTDR Temperature Profiling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current fiber-optic temperature sensing systems in downhole environments face challenges in achieving high-resolution, real-time temperature measurements with precise temperature changes, particularly in harsh geological conditions.
Innovation Solution
A method and system combining Distributed Temperature Sensing (DTS) and Phase Sensitive Optical Time Domain Reflectometry (ϕ-OTDR) technologies, where an optical fiber is interrogated with pulsed and coherent signals to estimate absolute temperature and temperature changes, respectively, and these are combined to generate a high-resolution temperature profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DTS is used to measure absolute temperature, then temperature measurement capability is provided, but measurement precision and update rate are limited
Solution Approach 1:
The patent combines two different temperature sensing technologies - DTS (for absolute temperature measurement) and φ-OTDR (for temperature change detection) - into a hybrid system. This merging allows the system to leverage the strengths of both methods: DTS provides accurate absolute temperature references while φ-OTDR provides high-update-rate temperature change measurements, achieving both precision and high productivity simultaneously
2Productivity
If φ-OTDR is used to measure temperature changes, then update rate is improved, but absolute temperature accuracy deteriorates
Solution Approach 1:
The patent uses DTS-measured absolute temperature as an intermediary reference to calibrate and anchor the φ-OTDR temperature change measurements. The DTS system periodically provides absolute temperature references that correct drift in the φ-OTDR system, enabling the φ-OTDR to maintain high update rates while achieving accurate absolute temperature measurements through the intermediary calibration data
3Measurement precision
If integration time is increased to improve temperature measurement accuracy, then measurement precision is improved, but response time deteriorates
Solution Approach 1:
The patent implements periodic absolute temperature measurements using DTS interspersed with continuous temperature change monitoring using φ-OTDR. The DTS measurements are performed at periodic intervals to provide absolute temperature calibration points, while the φ-OTDR continuously monitors temperature changes between these periodic measurements. This periodic action allows the system to maintain high measurement precision through adequate integration time for DTS while achieving fast response times through the continuous nature of φ-OTDR monitoring
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 accurate, high-resolution temperature measurements with kHz update rates and precision of 0.01 degrees C, providing a calibrated temperature profile that accounts for temperature changes in real-time, enhancing operational control in energy industry applications.
Implementation Method 1
interrogating the optical fiber with a pulsed optical signal generated by a distributed temperature sensing (DTS) assembly, the pulsed optical signal having a first frequency, receiving first reflected signals from the optical fiber, and estimating an absolute temperature from the reflected signals
Implementation Method 2
interrogating the optical fiber with an at least partially coherent optical signal from a phase sensitive optical time domain reflectometry (φ-OTDR) assembly, the at least partially coherent optical signal having a second frequency, and receiving second reflected signals from multiple scattering locations in the optical fiber
Implementation Method 3
estimating a phase difference between the reflected signals, estimating a temperature change based on the phase difference
Data Source
AI summary
A method of measuring temperatures, includes disposing a carrier in a borehole in an earth formation, the carrier having an optical fiber connected thereto, interrogating the optical fiber with a pulsed optical signal generated by a distributed temperature sensing (DTS) assembly, the pulsed optical signal having a first frequency, and receiving first reflected signals from the optical fiber, estimating an absolute temperature from the reflected signals, interrogating the optical fiber with an at least partially coherent optical signal from a phase sensitive optical time domain reflectometry (ϕ-OTDR) assembly, the at least partially coherent optical signal having a second frequency, and receiving second reflected signals from multiple scattering locations in the optical fiber; estimating a phase difference between the reflected signals, and estimating a temperature change based on the phase difference, and combining the absolute temperature and the temperature change to generate a temperature profile at a location in the borehole.