Pin-Box Coupling Assembly With Axial Locking for High-Torque Drill Strings

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Solution Overview

Problem

Existing couplings for elongated elements, particularly in deep well drilling, face challenges in handling high torque, tension, and compression while maintaining reliability and efficiency, especially in demanding environments like extended-reach drilling where friction loss and torque requirements are high, and traditional threaded connections are cumbersome and prone to deformation.

Innovation Solution

A coupling assembly featuring a pin and box configuration with key-and-lock ring-and-recess pairs and frusto-conical surfaces that align before mating, allowing for axial motion and hydraulic pressure to form a tight connection without rotation, enhancing axial strength, torque performance, and preventing progressive failure mechanisms like micro-slip.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional threaded pin-box connections are used to achieve firm fixing and sealing, then connection reliability is improved, but device complexity and operational difficulty increase due to requiring rotational torque and precise make-up conditions

Engineering Contradiction:

Improveconnection reliabilityVSAvoidconnection complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The connection interface is segmented into discrete key elements (protruding portions and recessed portions) that must align and engage separately, replacing the continuous threaded engagement with discrete locking features that simplify the connection process while maintaining reliability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The rotational torque-based threading mechanism is replaced with a direct axial insertion mechanism using key-and-lock geometry, eliminating the need for complex rotational make-up procedures and torque control while achieving firm fixing and sealing

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Strength

If premium connections with tapered threads and seal portions are used to meet higher torque and pressure demands, then strength and sealing are improved, but the wall thickness must be increased to withstand higher radial clamp forces

Engineering Contradiction:

Improvetorque and pressure resistanceVSAvoidcoupling weight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The key-and-lock features are pre-configured on the pin and box surfaces, allowing the connection to achieve its full strength and locking capability immediately upon axial insertion, eliminating the need for progressive torque application and multiple engagement stages required by threaded connections

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The frusto-conical surfaces provide curved, self-aligning contact surfaces that distribute loads more evenly across the connection interface, reducing peak stresses and allowing for thinner wall thicknesses while maintaining strength under torque and pressure

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Loss of energy

If thinner wall thicknesses are used in premium couplings to reduce hydrodynamic drag, then drag reduction is improved, but the coupling becomes more susceptible to deformation under high radial clamp forces

Engineering Contradiction:

Improvehydrodynamic dragVSAvoidcoupling deformation resistance

Core Design Contradiction:

Loss of energyVSStability of the object's composition

Solution Approach 1:

The threading and torque application features are extracted from the outer surface of the coupling, eliminating the need for thick walls to withstand radial clamp forces during make-up, allowing thinner walls that reduce hydrodynamic drag while maintaining structural integrity through the key-and-lock axial engagement mechanism

Inventive Principle:

Principle #2Taking out (Extraction)

4Length of stationary object

If multiple pin and box connections are made in extended-reach drilling to achieve well depth, then well depth capability is improved, but cumulative friction loss and operational time increase

Engineering Contradiction:

Improvewell depth capabilityVSAvoidoperational time

Core Design Contradiction:

Length of stationary objectVSLoss of time

Solution Approach 1:

The connection process skips the time-consuming rotational threading operation and proceeds directly to axial insertion and immediate locking, dramatically reducing the time required for each make-up operation and reducing cumulative operational time for multi-connection well assemblies

Inventive Principle:

Principle #21Skipping (Rushing through)

Data Source

PatentUS11624245B2Coupling assembly for elongate elements

Publication Date: 2023.04.11 TORSION TOOL COMPANY

AI summary

A coupling assembly for elongate elements includes a pin having an outward-facing pin surface, and a box having an inward-facing box surface. The pin surface and box surface are configured for mating engagement. At least one bore has a port configured for connection to an injection fluid reservoir as a first opening and a second opening penetrating the pin surface or the box surface. A region of the box surface can include a wall thickness less than the thicknesses of the adjacent box walls. A region of the box surface can also include a material of a lower mod ulus of elasticity than the material of a corresponding region of the pin surface, or vice versa. A region of the pin surface can include a wall thickness which is less than the thicknesses of the adjacent pin walls.