Flow-Actuated Cutter for Drill String Severing

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Solution Overview

Problem

Drill strings often become stuck in boreholes, especially at the lower end, due to mechanical and environmental challenges, making it difficult and costly to retrieve them, with existing methods being unreliable or requiring expensive equipment and specialized crews.

Innovation Solution

A method and apparatus that reduce the load-bearing cross-sectional area of the neck of a pin connection in a drill string section by using a flow-actuated cutter to erode or remove material, allowing for targeted severing of the string without the need for additional equipment or specialized operators, utilizing a cutter that can be quickly deployed and controlled to cut the string at the thinnest part of the connection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional pipe parting methods (blind back-off, explosive charges, jet cutters) are used to sever a stuck drill string, then the drill string can be separated, but the process requires expensive specialized equipment, trained crews, and takes significant time

Engineering Contradiction:

Improvesuccess rate of string separationVSAvoidcomplexity of severing equipment and process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by pre-weakening the drill pipe wall through controlled corrosion or notching before the actual parting operation. This preliminary damage to the pipe integrity allows the pipe to be severed more easily with reduced force, eliminating the need for complex explosive charges or specialized cutting equipment while maintaining high reliability of separation

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces complex mechanical severing systems (explosive charges, jet cutters, mechanical back-off tools) with a simplified chemical or controlled degradation approach. By using corrosion or notching to pre-weakenthe pipe, the system substitutes sophisticated mechanical parting equipment with a simpler process that achieves the same separation result

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Loss of time

If the drill string is left stuck for extended periods to attempt retrieval, then more time is available for fishing operations, but the probability of successfully freeing the string diminishes quickly with time

Engineering Contradiction:

Improvetime to retrieve drill stringVSAvoidprobability of freeing stuck string

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The patent performs preliminary weakening of the pipe structure before retrieval operations begin. This allows the drill string to be quickly severed and retrieved without requiring extended fishing operations, thereby reducing the time loss while maintaining high success probability by avoiding the diminishing returns of prolonged stuck conditions

Inventive Principle:

Principle #10Preliminary action

3Reliability

If the drill string is severed at connections rather than at the thinnest part of the pin, then the separation can be achieved, but significant damage is inflicted on the remaining connections making fishing more difficult

Engineering Contradiction:

Improvesuccess of string separationVSAvoiddamage to remaining connections

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by concentrating the weakening action specifically at the thinnest part of the pin (the most vulnerable location) rather than at the connection areas. This localized approach ensures that the pipe fails at the intended point while leaving the stronger connection regions intact and undamaged, facilitating easier subsequent fishing operations

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent converts the potential harm of uncontrolled pipe failure into a benefit by deliberately creating controlled weak points through corrosion or notching. This ensures the pipe fails in a predictable location (at the thinnest part of the pin) rather than damaging the connections, turning what could be a harmful uncontrolled fracture into a beneficial controlled separation

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 approach increases the likelihood of successful string separation by targeting the weakest point, reduces the need for expensive equipment and trained operators, and allows for immediate retrieval of the drill string or further operations like forming a kick-off plug, while minimizing damage to the remaining connections for easier fishing.

Implementation Method 1

A method and apparatus that reduce the load-bearing cross-sectional area of the neck of a pin connection in a drill string section by using a flow-actuated cutter to erode or remove material

Methodology Applied

Scientific EffectErosion: Erosion

Data Source

PatentUS10544655B2Method and apparatus for severing a drill string

Publication Date: 2020.01.28 CORETRAX GLOBAL LTD

AI summary

A method of severing a drill-string comprises reducing the load bearing cross-sectional area of the neck of a connection. The reduction in the area of the neck may be achieved using a precisely located flow-actuated cutter. The cutter may be pumped into the string to land on a seat above the connection. A bypass valve may be provided below the connection to facilitate fluid circulation.