Downhole Anti-Rotation Coupling With Faceted Torque Engagement
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Solution Overview
Problem
Existing downhole assembly connections, such as those with box and pin type connections, face issues with rotational sliding due to excessive torque loads exceeding frictional forces, leading to metal fatigue and localized fractures, especially under cyclic or high-frequency torsional oscillations.
Innovation Solution
The downhole assembly incorporates a shaft with engagement areas that include torsional locking elements, such as raised members or particles, which engage through a threaded connection with a compression element, enhancing torque transmission and preventing rotational sliding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If torque loads are transmitted across abutting surfaces of joined members, then the connection area is reduced, but the frictional forces may be insufficient to prevent relative rotation
Solution Approach 1:
The patent employs asymmetric profiles on the abutting surfaces of the joined members. These profiles include complementary geometric features (such as protrusions and recesses) that are not symmetric about the axis of the members. This asymmetry creates mechanical interlocking that prevents relative rotation between the members, thereby maintaining rotational engagement stability even with reduced contact surface area.
Solution Approach 2:
The patent creates a state where the contact surfaces are pre-loaded to a specific compression level, establishing an equipotential condition for force distribution. By applying a predetermined compressive force across the abutting surfaces with asymmetric profiles, the system ensures uniform pressure distribution that maximizes frictional engagement while preventing sliding, thus maintaining reliable rotational connection.
2Device complexity
If the contact surface area is smaller than threaded connections, then the unit forces on the surfaces are greater, but the threaded connection structure is more complex
Solution Approach 1:
The patent applies local quality by concentrating the asymmetric profile features at specific locations on the abutting surfaces rather than distributing complexity throughout the entire connection structure. The asymmetric profiles are localized geometric modifications on otherwise simple cylindrical members, providing enhanced mechanical interlocking only where needed at the contact interface, while keeping the overall connection structure simple and threaded.
3Reliability
If frictional forces are used to maintain rotational engagement, then the connection is simpler, but sliding contact can occur under excessive torque loads
Solution Approach 1:
The asymmetric profiles create mechanical interlocking that converts the friction-based connection into a mechanical interlock-based connection. The complementary geometric features (protrusions and recesses) physically prevent relative rotation between members, eliminating sliding contact and the associated harmful effects such as metal fatigue and localized fractures, while maintaining connection simplicity.
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
This configuration significantly increases the rotational force and torque transferred between components, reduces the likelihood of sliding and connection loosening, and minimizes metal fatigue, thereby enhancing the reliability and performance of drilling operations.
Implementation Method 1
The first and second engagement areas are under compression when engaged
Implementation Method 2
Frictional forces between the abutting surfaces keeps adjacent tubulars rotationally engaged
Data Source
AI summary
A downhole assembly that includes tubulars rotationally coupled to one another. An interface is between adjacent tubulars that makes up at least a portion of the rotational coupling. Certain surfaces of adjacent tubulars come into contact with one another when adjacent tubulars are rotationally coupled; and which are defined as contact surfaces. Each contact surface is profiled with facets that are complementary to facets on a corresponding contact surface of an adjacent tubular. The profiling of the contact surfaces is such that when a contact surface is brought together with a corresponding contact surface; facets on the contact surface abut facets on the corresponding contact surface along planes that are oblique or parallel with an axis of the tubular. At least some of a rotational torque transmitted between adjacent tubulars occurs across the abutting facets.