Optical Fibre Vibration Sensor for Rotary Equipment Monitoring
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Solution Overview
Problem
Monitoring the operation of rotary equipment within a borehole, such as coiled tubing, is challenging due to the need for precise detection of vibrations and strain, which existing technologies do not adequately address, especially in the context of downhole operations where communication and sensing are critical.
Innovation Solution
Utilizing an optical fibre as a distributed vibration sensor, operated with an OTDR system, to detect and analyze vibrations in the rotary equipment by transmitting coherent light pulses and processing backscattered light for strain detection, allowing for real-time observation of vibration magnitude and location along the fibre.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional vibration monitoring methods are used in downhole operations, then the equipment can detect vibrations, but the measurement precision and reliability are insufficient for accurate rotary equipment monitoring
Solution Approach 1:
The patent replaces traditional mechanical vibration sensors with an optical fibre-based distributed vibration sensing system. The optical fibre acts as a distributed sensor that detects vibrations through optical domain reflectometry, eliminating the need for mechanical transducers and electronic signal processing in harsh downhole environments. This substitution improves both measurement precision and reliability by using optical fields instead of mechanical fields for vibration detection.
Solution Approach 2:
The optical fibre serves multiple functions simultaneously: it acts as both a vibration sensor and a communication medium for transmitting data from the downhole rotary equipment to the surface. This multi-functionality improves reliability by reducing the number of separate systems needed and simplifies the overall monitoring architecture while maintaining high measurement precision through distributed sensing capabilities.
2Measurement precision
If distributed vibration sensing is implemented using optical fibre, then measurement precision improves, but device complexity increases due to the OTDR system requirements
Solution Approach 1:
The optical fibre acts as an intermediary that bridges the gap between the rotary equipment and the surface control system. It simultaneously carries vibration information through distributed sensing and communication signals, eliminating the need for complex mechanical sensors and electronic interfaces at the downhole equipment. This intermediary approach reduces overall system complexity while maintaining high measurement precision.
Solution Approach 2:
By making the optical fibre multi-functional (both sensing and communication), the system eliminates the need for separate vibration sensors, transducers, and communication cables. This consolidation reduces device complexity significantly while maintaining or improving measurement precision through distributed optical domain reflectometry.
3Reliability
If real-time vibration monitoring is implemented, then operational safety improves, but energy consumption increases due to continuous light pulse transmission and signal processing
Solution Approach 1:
The OTDR system transmits light pulses periodically rather than continuously, enabling real-time vibration monitoring through sequential pulse transmission and backscatter detection. This periodic action allows the system to maintain operational safety through continuous monitoring capability while reducing energy consumption compared to continuous transmission systems, as the average power required is lower with pulsed operation.
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 effective monitoring of vibrations in rotary equipment, providing real-time data on strain and vibration patterns, which can inform operational adjustments and improve the efficiency and safety of borehole operations by detecting changes in equipment performance and material interactions.
Implementation Method 1
providing an optical fibre extending down the elongate element from the surface to the rotary equipment
Implementation Method 2
transmitting coherent light pulses and processing backscattered light for strain detection
Implementation Method 3
operating the optical fibre as a distributed vibration sensor... observing and/or analysing vibration from the rotary equipment detected by the sensor
Implementation Method 4
there is strain and the resultant change in the fibre length (even though it is very small) can be seen as a change in this pattern of back scattering
Implementation Method 5
Light is then scattered back from points distributed along the fibre where there are slight variations in refractive index or other variations or imperfections in the material of the fibre
Implementation Method 6
variations in refractive index... slight variations in refractive index or other variations or imperfections in the material of the fibre
Data Source
AI summary
The operation of rotary equipment carried on elongate structure such as coiled tubing extending into a borehole from the Earth's surface is carried out by providing at least one optical fibre extending downhole to the rotary equipment from the surface, using optical time domain reflectometry to operating the optical fibre as a distributed vibration sensor while the rotary equipment is in operation, and thereby observing vibration created by the rotary equipment.