Downhole Under-reamer with Multi-Diameter Extendable Cutters

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Solution Overview

Problem

In downhole operations, underreaming is challenging due to the need to enlarge bore diameters below existing casing sections, which requires reamers to pass through restricted diameters and switch between different reaming diameters efficiently, often limiting the maximum casing size that can be achieved.

Innovation Solution

A downhole under-reamer with extendable cutters that can be configured to ream at multiple diameters, allowing for selective extension and retraction to accommodate various bore diameters, facilitated by a fluid-actuated activation mechanism and limiter system to manage cutter positions and fluid flow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a fixed diameter drill bit is used to drill through existing casing, then the drill bit can pass through the casing, but the borehole diameter is limited to a narrower gauge than the lined section

Engineering Contradiction:

Improveability to pass through existing casingVSAvoidborehole diameter

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The under-reamer employs dynamically extendable cutters that can change their radial position from retracted to extended states. This dynamic adjustment allows the tool to first pass through the casing with cutters retracted, then extend to enlarge the borehole diameter below the casing, resolving the contradiction between passing through restrictions and creating a larger borehole.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The under-reamer design nests the extendable cutters within the tool body when in the retracted position, allowing the entire assembly to pass through the existing casing. Once positioned below the casing, the cutters are deployed outward to create the enlarged borehole, effectively implementing a nested structure that transitions from a compact pass-through configuration to an expanded reaming configuration.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Adaptability or versatility

If multiple under-reamers are used to ream at different diameters, then various bore diameters can be achieved, but the time between reaming operations increases

Engineering Contradiction:

Improveability to ream at different diametersVSAvoidtime between reaming operations

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The under-reamer is designed as a multi-functional tool with cutters that can be extended to multiple predetermined positions corresponding to different reaming diameters. This allows a single tool to perform multiple reaming operations at different diameters without requiring trip-outs and trip-ins of multiple different tools, thereby reducing time loss while maintaining adaptability to various bore diameter requirements.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The under-reamer implements periodic extension and retraction of cutters to different positions during a single continuous operation. The cutters are extended to the first position for initial reaming, then retracted and extended to the second position for further enlargement, allowing sequential reaming at different diameters in one continuous run without interrupting the drilling operation.

Inventive Principle:

Principle #19Periodic action

3Volume of moving object

If cutters are extended to maximum diameter for reaming, then the borehole can be enlarged, but the under-reamer cannot pass through restricted diameters above

Engineering Contradiction:

Improveborehole diameterVSAvoidability to pass through restrictions

Core Design Contradiction:

Volume of moving objectVSEase of operation

Solution Approach 1:

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The cutters are held in the retracted position during the tripping-in operation to allow passage through the casing and restricted sections. Only after the under-reamer is positioned below the restriction is the preliminary action completed by extending the cutters to the extended position for reaming, ensuring successful navigation through restrictions before borehole enlargement.

Inventive Principle:

Principle #10Preliminary action

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

Enables efficient reaming at multiple diameters, maximizing casing sizes and allowing for flexible downhole operations, reducing the need for multiple under-reamers and minimizing time between reaming operations while ensuring effective passage through restricted sections.

Implementation Method 1

a fluid-actuated activation mechanism and limiter system to manage cutter positions and fluid flow

Methodology Applied

Scientific EffectHydraulic pressure: Pressure Gradient

Data Source

PatentUS10294728B2Downhole under-reamer and associated methods

Publication Date: 2019.05.21 GRANT PRIDECO LP

AI summary

A downhole under-reamer for use in reaming a downhole bore. The under-reamer comprises a body and a plurality of cutters mounted on the body. The cutters are mounted on the body so as to be extendable from a retracted position to at least two extended positions. The at least two extended positions comprise reaming positions at respective first and second reaming diameters.