Subsea Optical Distribution System for Multi-Fiber Sensing
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Solution Overview
Problem
Current subsea well sensing operations face challenges in maximizing the number of downhole sensing fibers while minimizing the number of subsea transmission fibers, due to physical and optical limitations in the subsea infrastructure.
Innovation Solution
The proposed system and method optimize the subsea optical distribution system by using a dual transmission fiber configuration with a distal WDM and circulators, allowing for increased pulse repetition rates and improved signal quality, thereby enabling multiple downhole sensing fibers to be used efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple downhole sensing fibers are deployed in subsea wells, then sensing coverage and data quality improve, but the number of subsea transmission fibers and optical connectors increases, leading to higher complexity and cost
Solution Approach 1:
The patent combines multiple downhole sensing fibers into a single transmission fiber using wavelength division multiplexing (WDM). Each sensing fiber operates at a distinct wavelength, allowing simultaneous transmission through one fiber, thereby reducing the number of transmission fibers and optical connectors while maintaining multiple sensing capabilities
Solution Approach 2:
The optical feedthrough system is designed to handle multiple wavelengths simultaneously, enabling a single transmission fiber to serve multiple sensing functions. The system can accommodate different sensing applications (temperature, pressure, acoustic) on different wavelengths within the same fiber infrastructure
2Loss of energy
If the number of optical connectors and splices is reduced, then insertion losses decrease and signal quality improves, but the flexibility and configurability of the optical distribution system are limited
Solution Approach 1:
The system employs dynamic wavelength assignment where different wavelengths can be allocated to different sensing fibers based on operational requirements. The WDM configuration allows flexible reconfiguration of wavelength-to-fiber mapping without physical reconnection, maintaining adaptability while minimizing connectors
Solution Approach 2:
The patent adds the wavelength dimension to the optical transmission system. Instead of adding more spatial paths (more fibers and connectors), the system utilizes the spectral dimension by operating multiple sensing channels at different wavelengths within a single fiber, thereby reducing physical complexity while maintaining configurability
3Use of energy by moving object
If subsea transmission fiber length is minimized, then optical signal strength is maintained, but the distance between topside facility and subsea tree is constrained
Solution Approach 1:
The system changes the optical parameter by using multiple wavelengths with WDM technology. This allows the optical signal to maintain sufficient strength over long distances by distributing power across multiple wavelength channels, each experiencing less attenuation, thereby enabling longer transmission distances without compromising signal quality
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 maximizes the number of downhole sensing fibers that can be configured for various sensing applications, reduces the complexity and cost of subsea optical infrastructure, and enhances the signal-to-noise ratio and data quality in subsea well sensing operations.
Implementation Method 1
a first wavelength division multiplexer (WDM) disposed within the subsea tree and operable to receive the first optical pulse from the first transmission fiber and direct the first optical pulse to the first downhole sensing fiber
Implementation Method 2
a distal passive optical circulator arrangement
Implementation Method 3
at least one downhole sensing fiber in the wellbore optically connected to a subsea optical distribution system, which provides optical continuity between a plurality of downhole sensing fibers and a single transmission fiber
Implementation Method 4
by using fiber Bragg gratings (FBGs), is an alternative cost-effective method of obtaining real-time, high resolution, highly accurate temperature and/or strain data at discrete locations along the wellbore
Data Source
AI summary
A fiber optic sensing (FOS) system and method. The system may include one or more interrogator units and a proximal wavelength division multiplexer (WDM) and a distal WDM optically connectable to the one or more interrogator units, an upgoing transmission fiber, a down-going transmission fiber, and one or more downhole sensing fibers. The method may include transmitting one or more light pulses from an interrogator unit, multiplexing the one or more light pulses from the interrogator unit with a proximal WDM into an upgoing transmission fiber and a down-going transmission fiber, and receiving the one or more light pulses with a distal WDM. The method may further include multiplexing the one or more light pulses from the upgoing transmission fiber and the down-going transmission fiber into one or more downhole sensing fibers and receiving backscatter light from at least one of the one or more downhole sensing fibers.