Split Interrogator Layout for Long-Reach Subsea Acoustic Sensing
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Solution Overview
Problem
Subsea well sensing operations face challenges due to significant complexity and cost associated with marinizing interrogator systems, and the limited distance at which interrogation signals can travel, restricting the ability to monitor downhole sensing fibers effectively.
Innovation Solution
The system employs enhanced backscatter fibers (EBF) with coatings to increase signal strength and noise ratio, and integrates these fibers with transmission fibers in subsea infrastructure to maintain high pulse power and signal fidelity, while using interrogators on the topside facility to eliminate downhole electronic complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If marinization of interrogator systems is implemented for subsea well sensing operations, then the system can operate in subsea environments, but significant complexity and cost are introduced to the Subsea Production System and related electrical and optical distribution systems
Solution Approach 1:
The patent extracts the interrogator system from the subsea environment and places it on the topside facility, eliminating the need for marinization. The downhole sensing fiber is connected to the topside interrogator through optical distribution in the subsea infrastructure, thereby removing the complexity of subsea-qualified electronic equipment while maintaining subsea sensing capability.
Solution Approach 2:
The patent introduces optical distribution infrastructure (optical cables, connectors, and interfaces) as an intermediary between the topside interrogator and the downhole sensing fiber. This optical intermediary enables signal transmission through the subsea environment without requiring the interrogator itself to be subsea-qualified, thus reducing system complexity.
2Length of moving object
If long lengths of subsea transmission fiber (5 to 100+km) are used to connect topside facility to subsea tree, then subsea well sensing operations can be performed at distance, but optical engineering solutions are required to compensate for insertion losses accumulated through multiple components
Solution Approach 1:
The patent merges multiple optical components (transmission fiber, downhole sensing fiber, connectors, and splices) into a simplified optical distribution architecture. By integrating these elements into a unified optical path from the topside interrogator to the downhole sensing fiber, the system reduces the number of separate optical interfaces and minimizes cumulative insertion losses, thereby extending sensing reach without requiring complex compensation solutions.
3Adaptability or versatility
If multiple wet- and dry-mate optical connectors, splices, and optical feedthrough systems are used in the subsea Christmas tree, then optical connectivity is achieved, but insertion losses accumulate and cap the distance of subsea well sensing operations
Solution Approach 1:
The patent extracts the electronic interrogation function from the subsea environment and relocates it to the topside facility. This eliminates the need for multiple optical feedthrough systems and complex connector assemblies in the subsea Christmas tree, reducing the number of optical interfaces and minimizing cumulative insertion losses that would otherwise limit sensing distance.
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 enhances signal quality and fidelity, allowing for extended monitoring reach of up to several tens of kilometers, simplifying subsea optical distribution systems, and reducing operational costs by eliminating the need for complex downhole electronics.
Implementation Method 1
Distributed Acoustic Sensing (DAS), DSS, DTS, and FBG sensing has been practiced for monitoring downhole sensing fibers... by using fiber Bragg gratings (FBGs)... Distributed fiber optic sensing can be enabled by continuously sensing along the length of the optical fiber, and effectively assigning discrete measurements to a position or set of positions along the length of the fiber via optical time-domain reflectometry (OTDR)
Implementation Method 2
Fiber optic cables may be permanently deployed downhole in a wellbore via single- or dual-trip completion strings, behind casing, on tubing, or in pumped down installations
Data Source
AI summary
A fiber optic sensing (FOS) system and method of operation. The system may include a flying lead in which an integrated compartment is disposed with the flying lead, a transmitter disposed within the integrated compartment and configurable to transmit an interrogator signal and a remote circulator disposed in the integrated compartment and optically connected to the transmitter through an optical fiber, wherein the remote circulator is configurable to direct the interrogator signal to a downhole sensor fiber that is disposed in a wellbore. The system may further include a remote optical power amplification disposed within the integrated compartment and optically connected to the remote circulator by a second optical fiber.