Fiber Optic Thread Assembly With Cumulative Gap for Downhole Accuracy
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Solution Overview
Problem
Existing wireline and slickline cables with fiber optic threads suffer from imprecision in data acquisition due to loose placement of fibers, which leads to stress-induced micro-bend fractures and inaccurate temperature and pressure measurements.
Innovation Solution
Incorporating a fiber optic thread into a wireline cable with a cumulative gap of at least 0.002 inches between the thread and the package, allowing mechanical responsiveness while minimizing stress on the fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fiber optic thread is placed loosely within the metal tube, then the fiber optic thread is protected from stress-induced damage, but the precision of data acquisition deteriorates
Solution Approach 1:
The patent introduces a gel-filled tube as an intermediary medium between the fiber optic thread and the metal tube. The gel acts as a stress-distributing medium that transmits mechanical stresses uniformly to the fiber optic thread, enabling accurate strain measurements while preventing stress concentration that would cause micro-bend fractures. This resolves the contradiction by providing both protection and measurement capability.
Solution Approach 2:
The patent changes the physical state and properties of the filling material from air (in traditional loose placement) to a gel substance. This parameter change allows the filling material to transmit mechanical stresses effectively to the fiber optic thread while maintaining protection, thereby improving measurement precision without sacrificing reliability.
2Measurement precision
If the fiber optic thread is placed against the metal tube structure, then measurement precision improves, but stress-induced micro-bend fractures increase
Solution Approach 1:
The gel-filled tube serves as a mediator between the metal tube structure and the fiber optic thread. It transmits mechanical stresses uniformly across the fiber optic thread surface, enabling accurate stress detection while distributing loads to prevent stress concentration and micro-bend fractures, thus resolving the contradiction between measurement precision and fiber integrity.
Solution Approach 2:
The gel substance acts as a flexible intermediary layer that conforms to the metal tube structure while protecting the fiber optic thread. This flexible medium transmits mechanical deformations for accurate measurement while preventing direct contact stresses that would cause fiber damage.
3Ease of manufacture
If the fiber optic thread is loosely placed in the metal tube, then manufacturing simplicity is maintained, but temperature measurement accuracy deteriorates
Solution Approach 1:
The patent changes the filling medium from air to gel, which has superior thermal conductivity. This parameter change enables effective thermal contact between the metal tube and fiber optic thread for accurate temperature measurements, while the gel continues to provide mechanical protection and stress distribution.
Solution Approach 2:
The gel-filled tube acts as a thermal intermediary that conducts heat from the metal tube structure to the fiber optic thread, enabling accurate temperature measurements. The gel maintains this thermal coupling while preserving the protective and mechanical coupling functions.
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 solution enhances the accuracy of fiber optic readings by ensuring mechanical responsiveness without inducing micro-bend fractures, thereby improving data precision in downhole applications.
Implementation Method 1
the fiber optic portion of the assembly is often referred to as the FIMT (fiber(s) in metal tube(s))
Implementation Method 2
allowing the fiber optics within the tube to float or migrate over the course of an application may help to prevent stress induced damage to the fibers as a result of mechanical bending and torque from the surrounding tube
Data Source
AI summary
A fiber optic thread assembly configured with a cumulative gap for mechanical responsiveness and protection from micro-bend damage. The assembly may be incorporated into a wireline or slickline cable for obtaining fiber optic readings of enhanced accuracy during an application in a well. The gap is uniquely tailored to allow for a natural reduction during deployment of the cable into the well, thereby providing the enhanced accuracy. However, the gap is also sufficient to help avoid micro-bend damage from the resulting mechanical responsiveness, which is attained upon deployment of the cable into the well.