Fiber Optic Protection Assembly for Wellbore Fluid Sealing
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Solution Overview
Problem
Fiber optic cables face damage from wellbore fluids due to hydrostatic pressure equalization when the Fiber In Metal Tube (FIMT) is cut to expose individual fiber strands, leading to 'U tubing' and potential electrical shorts.
Innovation Solution
A fiber optic protection assembly with disc receiving areas and tension bolts, including O-rings, that compresses to seal the fiber tube, preventing hydrostatic pressure from reaching the fiber termination sub and protecting the fibers from wellbore fluids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the FIMT is cut to expose individual fiber strands for termination, then the fiber optic cable can be deployed and retrieved for redeployment, but wellbore fluids under hydrostatic pressure can enter the fiber termination sub through the open-ended FIMT
Solution Approach 1:
A protection assembly acts as an intermediary barrier between the wellbore environment and the fiber termination sub. This assembly includes a seal mechanism that prevents direct fluid access to the termination area while allowing the FIMT to remain open-ended for fiber deployment and retrieval operations.
Solution Approach 2:
The sealing function is extracted from the FIMT itself and implemented as a separate protection assembly. This allows the FIMT to maintain its open-ended structure for cable deployment while the separate assembly provides the necessary fluid barrier at the termination sub interface.
2Reliability
If di-electric grease is injected into the cable head void to insulate copper conductors, then electrical insulation is achieved, but the grease cannot prevent fluid from reaching the fiber termination area
Solution Approach 1:
The protection assembly serves as an intermediary barrier between the wellbore fluids and the fiber termination sub. It includes sealing elements that prevent fluid intrusion into the termination area, complementing the di-electric grease insulation function without interfering with it.
Solution Approach 2:
The cable head is segmented into distinct functional zones: the copper conductor insulation zone (protected by di-electric grease) and the fiber termination zone (protected by the separate protection assembly). This segmentation allows each zone to be protected by the most appropriate method for its specific requirements.
3Reliability
If multiple O-rings are placed between tension bolts and discs, then sealing effectiveness is improved, but the assembly complexity increases
Solution Approach 1:
Multiple O-rings (flexible sealing elements) are strategically placed at critical interfaces within the protection assembly - specifically between the tension bolts and discs, and between adjacent discs. These thin film seals provide reliable fluid barriers while maintaining a relatively simple overall assembly structure.
Solution Approach 2:
The O-rings are pre-positioned between the tension bolts and discs during assembly, creating sealed chambers before the assembly is subjected to wellbore conditions. This preliminary sealing action ensures fluid exclusion is established before any potential intrusion can occur.
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
Effectively prevents the flow of wellbore fluids under hydrostatic pressure from entering the fiber termination sub, ensuring the integrity and functionality of the fiber optic strands during deployment and operation.
Implementation Method 1
Hydrostatic pressure is the force pressure of a column of fluid measured in pounds per square inch. Hydrostatic pressure increases as an object is lowered deeper into a column of fluid.
Implementation Method 2
A fiber optic protection assembly with disc receiving areas and tension bolts, including O-rings, that compresses to seal the fiber tube
Data Source
AI summary
Fiber optic protection assembly for preventing fluid from entering into a fiber termination sub, including a sub having disc-receiving areas and inner channel connecting the disc-receiving areas. Disc-receiving areas receive plurality of discs, each disc having a disc channel. The sub includes tension bolts, each having a bolt channel. The sub receives a fiber tube or a Fiber in Metal Tube (FIMT) comprising fiber optic cables through bolt channels, disc channels of the discs and inner channel. Discs properly seal the void in the sub to ensure protection to the insulation, center conductor and fiber tube/FIMT. When the fiber optic protection assembly is lowered into the well, hydrostatic pressure compresses the discs and O-rings of the top tension bolt ensure protection to the insulation that houses the fiber tube. Compression of the discs ensures no pressure gets to the bottom tension bolt, thus protecting fiber optic strands from hydrostatic pressure.