Threaded Connection Retaining Device for Expansion Sealing

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Solution Overview

Problem

Threaded connections in subterranean tubular strings often experience leakage due to separation of pin and box ends during expansion, particularly at high temperatures and due to radial expansion leading to wall thinning and reduced contact pressure, which existing solutions like pre-stressing and resilient seals fail to adequately address.

Innovation Solution

A retaining device with interlocking fingers between thread steps that allows for relative axial movement while maintaining a metal-to-metal seal, utilizing a groove and taper design to enhance sealing and resist expansion-induced separation, applicable to both single and multi-step threads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the threaded connection is expanded to fit into the preexisting string, then the connection achieves proper positioning and common inside diameter, but the pin and box ends separate and lose gas tight sealing

Engineering Contradiction:

Improvegas tight sealingVSAvoidthread connection integrity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The thread forms are pre-stressed during makeup by bending the pin end away from the longitudinal axis and creating a groove at the box base. This preliminary action stores elastic energy that counteracts the separation forces during expansion, maintaining gas tight sealing throughout the expansion process

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The threaded connection is divided into multiple thread steps with retention devices positioned between the steps. This segmentation allows different portions of the thread to perform different functions - some steps provide sealing while others provide structural retention, preventing separation during expansion

Inventive Principle:

Principle #1Segmentation

2Reliability

If pre-stressing the pin end by bending it on makeup is used to prevent curling, then the pin nose retention is improved, but the box end cantilevering creates separation during expansion

Engineering Contradiction:

Improvepin nose retentionVSAvoidconnection stability

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

Different portions of the thread connection have different structural properties - the pin end is pre-bent and grooved for retention while the box end is cantilevered on a fulcrum. This local differentiation allows each end to respond optimally to expansion forces, with the pin end resisting curling and the box end curling in against the pin

Inventive Principle:

Principle #3Local quality

3Reliability

If resilient seals are used between thread steps, then sealing is improved at lower temperatures, but the seals fail at high temperatures exceeding 150° C.

Engineering Contradiction:

Improvesealing effectivenessVSAvoidservice temperature limit

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent replaces resilient seal materials with a mechanical retention system using interlocking thread forms, grooves, and retention devices. This mechanical system maintains sealing effectiveness at high temperatures where elastomeric seals would fail, as it relies on geometric interlocking rather than material elasticity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The solution combines metal-to-metal contact surfaces with geometric retention features (grooves, fingers, protrusions) to create a composite sealing mechanism that operates effectively across a wide temperature range, eliminating dependence on temperature-sensitive elastomeric materials

Inventive Principle:

Principle #40Composite materials

4Volume of moving object

If radial expansion is performed to conserve volume, then the inside diameter is maintained, but wall thinning reduces the force holding mating metal surfaces together

Engineering Contradiction:

Improveinternal volume conservationVSAvoidcontact pressure

Core Design Contradiction:

Volume of moving objectVSStrength

Solution Approach 1:

The thread forms are pre-stressed during makeup to store elastic energy before expansion. This preliminary action creates residual contact pressure that compensates for the wall thinning effect during radial expansion, maintaining the force necessary to hold mating metal surfaces together

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent addresses the two-dimensional wall thinning problem by introducing axial dimension changes through pre-stressing. The axial pre-bending and groove formation create a three-dimensional retention mechanism that maintains sealing pressure despite radial expansion and wall thinning

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS9222607B2Threaded connection with metal to metal seal capable of expansion

Publication Date: 2015.12.29 BAKER HUGHES CO

AI summary

A retaining device for a threaded connection that is expanded holds the connection together to prevent leakage. In a two step thread the retention device is located between the steps and comprises a nose in a groove that holds aligned surfaces together for a metal to metal connection and allows for relative axial movement at the same time.