Fiber Optic Thread Assembly Gap Layout to Prevent Micro-Bend Damage
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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, which leads to stress-induced damage 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 loosely placed 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:
A gel or grease intermediary material is introduced between the fiber optic thread and the metal tube. This intermediary fills the gaps and voids while maintaining mechanical isolation, allowing the fiber to remain protected from direct stress contact while improving thermal and mechanical coupling for more accurate data acquisition. The gel acts as a mediator that transmits environmental conditions to the fiber without transmitting damaging mechanical stresses.
2Measurement precision
If the fiber optic thread is placed directly against the metal tube, then the precision of data acquisition improves, but the fiber optic thread suffers from micro-bend fractures
Solution Approach 1:
The gel or grease intermediary material is positioned between the fiber optic thread and the metal tube to prevent direct contact. This intermediary layer allows thermal and mechanical coupling for accurate measurements while physically isolating the fiber from stress-induced micro-bend fractures. The gel fills the interface gaps and provides a compliant barrier that protects the fiber during cable deployment and operation.
3Reliability
If the fiber optic thread is loosely placed in the metal tube, then stress-induced damage is prevented, but temperature and pressure measurements become inaccurate
Solution Approach 1:
The gel or grease intermediary material improves thermal coupling between the metal tube and the fiber optic thread while maintaining mechanical protection. The gel fills the air gaps and voids that previously existed in loose placements, creating a continuous thermal path that allows accurate temperature and pressure measurements without requiring direct rigid contact between the fiber and tube.
4Measurement precision
If the fiber optic thread is structurally located right against the metal tube, then data accuracy improves, but the surrounding structure induces micro-bend fractures
Solution Approach 1:
The gel or grease intermediary material is introduced between the fiber optic thread and the metal tube to eliminate direct structural contact. This intermediary provides a compliant interface that allows the fiber to accurately sense temperature and pressure conditions while preventing the surrounding metal tube structure from inducing micro-bend fractures during cable deployment and operation.
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.