Double-Taper Threaded Connection With Multiple Seals for Oilfield Tubing

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Solution Overview

Problem

Threaded connections in oilfield tubing often fail due to stress concentrations during deployment and production, exceeding compression limits and leading to structural and sealing issues.

Innovation Solution

A threaded connection design featuring a double-taper thread profile with an intermediate shoulder, including a first section with a greater taper angle and a second section with a lesser taper angle, along with multiple seals to enhance torsional strength and gas-tight sealing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional single-taper thread profile is used, then the connection structure is simple, but stress concentrations occur during deployment and production leading to connection failure

Engineering Contradiction:

Improveconnection reliabilityVSAvoidthread profile complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The thread profile is segmented into multiple sections with different taper angles. The external thread profile includes a first section with a first taper angle and a second section with a second taper angle, creating distinct zones that distribute stress more evenly throughout the connection, thereby improving reliability while managing complexity through functional segmentation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different sections of the thread profile are assigned different local geometric properties (taper angles) optimized for specific functions. The first section has a taper angle optimized for one aspect of stress distribution, while the second section has a different taper angle optimized for another aspect, allowing each local region to address specific stress concentration issues.

Inventive Principle:

Principle #3Local quality

2Strength

If a double-taper thread profile with intermediate shoulder is used, then stress distribution is improved, but manufacturing complexity increases

Engineering Contradiction:

Improvetorsional strengthVSAvoidthread manufacturing ease

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The thread profile is divided into multiple sections with different taper angles. The external thread profile includes a first section with a first taper angle and a second section with a second taper angle, creating distinct zones that distribute stress more evenly throughout the connection, thereby improving reliability while managing complexity through functional segmentation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Inventive Principle:

Principle #3Local quality

3Reliability

If multiple seals are added to the threaded connection, then sealing capability is enhanced, but device complexity increases

Engineering Contradiction:

Improvesealing reliabilityVSAvoidconnection structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The sealing system is segmented into multiple seals positioned at different locations within the threaded connection. This distribution of sealing functions across multiple components improves overall sealing reliability by providing redundant sealing paths and addressing different potential failure points in the sealing system.

Inventive Principle:

Principle #1Segmentation

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 design improves torsional strength and sealing capabilities, reducing the risk of cross-threading and failure, while maintaining a gas-tight seal under challenging well conditions.

Implementation Method 1

A cross-sectional area of the pin end increases at the intermediate shoulder

Methodology Applied

Scientific EffectStress distribution:

Implementation Method 2

In an interference fit, tapered pin and box ends are tightly wedged together as the pin threadably advances into the box

Methodology Applied

Scientific EffectInterference fit:

Implementation Method 3

The resulting interference fit provides both structural and sealing connections between the pin and box ends

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 4

a shouldering connection engages an annular shoulder on the pin end with an annular shoulder provided on the box end

Methodology Applied

Scientific EffectShouldering connection:

Implementation Method 5

The threads of the shouldering connection provide the structure holding the pin and box ends together, and the engaged shoulders help facilitate a sealed engagement

Methodology Applied

Scientific EffectPressure: Pressure Increase

Data Source

PatentUS12385326B2High torque threaded connections with external upset and multiple seals

Publication Date: 2025.08.12 SAUDI ARABIAN OIL CO

AI summary

A threaded connection includes a first tubular member having a box end defining an internal thread profile, and a second tubular member having a pin end defining an external thread profile threadably engageable with the internal thread profile of the box end. The external thread profile includes a first section that extends at a first taper angle relative to a longitudinal axis of the threaded connection, a second section extending from the first section at a second taper angle relative to the longitudinal axis, and an intermediate shoulder provided at a transition between the first and second sections and engageable with a corresponding intermediate shoulder provided on the internal thread profile. A cross-sectional area of the pin end increases at the intermediate shoulder.