Flexible Downhole Coupling With Controlled Bending Stops
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Solution Overview
Problem
Existing flexible couplings for downhole drive strings face challenges in accommodating varying drilling angles and bending requirements, as they often apply point loads and shear forces, leading to potential failure and reduced flexibility.
Innovation Solution
A flexible coupling design featuring a central section with contact surfaces and pivoting connectors, allowing for pivotal movement of coupling sections within a range of at least 10 degrees, with threaded shafts and balls for secure connection, and a fluid passage for communication between sections, which limits pivotal movement and applies compressive force to reduce strain on the central block.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing flexible couplings are used to accommodate bending, then the drive string can bend at different angles, but point loads and shear forces are applied leading to potential failure
Solution Approach 1:
The flexible coupling is divided into multiple coupling sections (first coupling section, second coupling section, and central section) that can pivot independently relative to each other. This segmentation allows the coupling to accommodate bending at different angles while distributing mechanical loads across multiple pivot points, preventing concentration of point loads and shear forces that would lead to failure.
Solution Approach 2:
The contact surfaces of the coupling sections are angled at specific angles (e.g., 45 degrees) relative to the longitudinal axis. By changing the angular parameter of the contact surfaces, the coupling transforms the application of point loads and shear forces into distributed compressive forces along the angled contact surfaces, thereby reducing failure risk while maintaining bending adaptability.
2Adaptability or versatility
If flexible coupling allows pivotal movement for angle adjustment, then drilling at different angles is enabled, but structural integrity may be compromised
Solution Approach 1:
The coupling sections are designed to pivot dynamically within a controlled range (e.g., at least 10 degrees) relative to the central section through ball joint connections. This dynamic capability enables angle adjustment for drilling at different directions while the pivotal movement is constrained by angled contact surfaces that maintain structural integrity by converting uncontrolled shear forces into controlled compressive forces.
Solution Approach 2:
The angled contact surfaces (e.g., at 45 degrees to the longitudinal axis) change the mechanical parameter of force distribution. When coupling sections pivot, the angled surfaces engage to apply compressive forces rather than allowing direct shear loading, thereby maintaining structural integrity during angle adjustments.
3Manufacturing precision
If contact surfaces are angled to determine bending degree, then precise angle control is achieved, but manufacturing complexity increases
Solution Approach 1:
The contact surfaces are designed with specific angles (e.g., 45 degrees) relative to the longitudinal axis of the coupling sections. By defining a specific angular parameter, the coupling achieves precise control over the degree of bending and pivotal movement. The angled surfaces act as mechanical stops that limit rotation to predetermined angles, providing precise angle control through geometric constraints rather than complex active control systems.
Solution Approach 2:
The coupling is segmented into multiple sections with angled contact surfaces at their interfaces. Each interface independently controls the pivotal movement between adjacent sections, allowing precise angle control to be achieved through simple geometric features at each joint rather than requiring complex manufacturing of the entire assembly as a single precision component.
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
The flexible coupling effectively allows for controlled bending of downhole tubing strings, reducing strain and risk of failure by distributing forces as tension and compression, enabling precise angle adjustments and maintaining structural integrity during drilling.
Implementation Method 1
The first and second connectors may comprise threaded shafts at the first end and balls at the second end, and the retaining portion of the first and second coupling sections may be shaped to receive the balls of the connectors. The pivoting connections may be ball joints.
Implementation Method 2
The flexible coupling effectively allows for controlled bending of downhole tubing strings, reducing strain and risk of failure by distributing forces as tension and compression.
Implementation Method 3
The first and second coupling sections may apply a compressive force to the central block in a fully pivoted position.
Implementation Method 4
The first and second connectors may comprise threaded shafts at the first end and balls at the second end
Data Source
AI summary
A flexible coupling for coupling sections of a downhole tubing string is provided. The flexible coupling has a central section with first and second ends, each end having a contact surface and a first part of a pivoting connector, the contact surface extending radially outward relative to the first part of the pivoting connector. The flexible coupling also has first and second coupling sections pivotally coupled to the first and second ends of the central section. Each of the first and second coupling sections have a tubing string attachment at a first end, a second part of the pivoting connector at a second end, and a contact surface at the second end, the contact surface extending radially outward relative to the second part of the pivoting connector. Pivotal movement of the first and second coupling sections relative to the central section is limited by engagement between the contact surfaces.