Downhole Tool Cable Head Fluid Seal and Tension Release
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Solution Overview
Problem
Current cable heads in wellbore operations allow wellbore fluid to contaminate the conveyance line, leading to unpredictable tension calculations due to metal fatigue and stress concentrations in armor wires, resulting in imprecise separation and potential equipment failure.
Innovation Solution
A downhole tool with a cable head design featuring interconnected bodies that include a line end termination device, fluid seals, and breakable pins to manage tension and prevent fluid ingress, ensuring precise release and minimizing contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the armor wires are exposed at the end of the line to allow connection with the cable head, then mechanical connection is facilitated, but wellbore fluid can enter the line beneath the sheath and migrate upward, contaminating long portions of the line
Solution Approach 1:
The cable head is divided into multiple bodies (first body, second body, third body) that can move relative to each other. This segmentation allows the system to isolate the connection area from the fluid environment while maintaining operational capability for line connection and tension control.
Solution Approach 2:
Fluid seals are introduced as intermediary elements between the line and the wellbore fluid environment. These seals prevent fluid ingress into the cable head while allowing the line to pass through, thus protecting against contamination during operations.
2Productivity
If tension is applied to the line to break armor wires at the cable head for separation, then the line can be removed to retrieve stuck tool string, but the actual strength of armor wires is difficult to determine due to unknown metal fatigue and unpredictable stress concentrations
Solution Approach 1:
The invention introduces breakable pins with known and controllable strength characteristics as an alternative to relying on armor wire strength. By changing the failure mechanism from unpredictable armor wire breakage to controlled pin failure, the system achieves precise tension control and predictable separation behavior.
Solution Approach 2:
The first body is designed to move with respect to the second body when predetermined tension is applied, creating an asymmetric failure mode that provides controlled separation. This asymmetric design ensures that the breakable pins fail at a predetermined tension point, enabling precise control over when and how the line separates from the tool string.
3Adaptability or versatility
If the cable head allows wellbore fluid entry for operational flexibility, then connection and tensioning operations can be performed, but the contaminated portions of the line have to be cut off and discarded each time the line is reheaded
Solution Approach 1:
The invention converts the potential harm of fluid exposure into a benefit by using fluid seals to prevent contamination while maintaining operational flexibility. The seals allow the system to benefit from operational versatility without suffering the harmful effect of line contamination, thus eliminating the need to discard contaminated line portions.
Data Source
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AI summary
A downhole tool for connecting with a conveyance line. The downhole tool may include a body configured to receive the line and a fluid seal operable to seal against the line when the downhole tool is connected with the line to inhibit wellbore fluid from entering the body when the downhole tool is conveyed within a wellbore via the line. The downhole tool may include a fluid seal slidably disposed within the body and operable to seal against an inner surface of the body to inhibit wellbore fluid from entering the body when the downhole tool is conveyed within the wellbore. The body may include a first body and a second body connected together, wherein the first body is operable to move with respect to the second body when a predetermined tension is applied to the line from the wellsite surface to cause the downhole tool to release the line.