Stranded Fiber-Optic Cable With Zero-Degree Lay for Downhole Sensing
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Solution Overview
Problem
Existing fiber optic cables for downhole applications in wells suffer from imprecision in data acquisition due to loose placement of fibers, which leads to stress-induced damage and inaccurate temperature and strain measurements, and conventional encasement methods cause micro-bend fractures.
Innovation Solution
A fiber optic cable design featuring stranded fiber optic threads coupled together at a zero degree lay angle, filled with a polymeric material, and jacketed for structural reinforcement, eliminating hollow tubing and reducing stress on the fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fiber optic threads are loosely placed in metal tubes, then stress-induced damage to fibers is reduced, but measurement precision and data accuracy deteriorate
Solution Approach 1:
A gel-filled polymer coating is applied as an intermediary layer between the fiber optic threads and the metal tube. This coating provides mechanical coupling to improve measurement accuracy while the gel filling accommodates thermal expansion and prevents stress concentration, thus maintaining fiber durability.
2Measurement precision
If fiber optic threads are directly encased by metal tube without spacing, then measurement accuracy improves, but micro-bend fractures increase
Solution Approach 1:
The gel-filled polymer coating serves as a protective intermediary that distributes mechanical stresses uniformly across the fiber surface, preventing localized stress concentrations that cause micro-bend fractures while maintaining adequate mechanical coupling for accurate measurements.
Solution Approach 2:
The gel filling within the polymer coating provides beforehand cushioning by accommodating thermal expansion and contraction, as well as absorbing mechanical shocks before they can transmit to the fiber optic threads, thereby preventing micro-bend fractures.
3Reliability
If airspace is left between fiber thread and tube, then stress damage is reduced, but temperature and stress detection accuracy deteriorate
Solution Approach 1:
The gel-filled polymer coating acts as a thermal intermediary that conducts temperature changes from the metal tube to the fiber optic threads while simultaneously providing mechanical protection. The gel's thermal conductivity ensures accurate temperature detection without requiring direct contact, while its cushioning properties maintain fiber protection.
Data Source
AI summary
A fiber optic bundle for incorporation into a cable for use in a well. The bundle includes multiple fiber optic threads that are helically wound about one another at a zero degree lay angle for structural reinforcement. Further, the cable that employs the bundle may be coupled in nature and gas proof thereby rendering the fiber optics mechanically responsive for improved accuracy in detections during use in a well application.