Rotor Catch Assembly for Downhole Motor Retrieval

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Solution Overview

Problem

Downhole motor assemblies often experience separation of the bearing assembly from the power section due to mechanical failure or threaded connection issues during drilling, leading to costly and time-consuming retrieval operations, especially when the rotor is helically fluted and hard-chrome coated, making conventional fishing tools ineffective.

Innovation Solution

A rotor catch assembly that includes a tubular housing and a rotor shaft capable of axial movement, which can block fluid flow to the downhole motor assembly in case of a failure, preventing further disengagement and facilitating retrieval by generating pressure pulses to reduce friction and aid in the advancement of the workstring.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If conventional fishing tools are used to retrieve the rotor, then retrieval can be attempted, but the rotor is difficult to latch onto because it is helically fluted and hard-chrome coated

Engineering Contradiction:

ImproveEase of retrievalVSAvoidDifficulty of latching onto rotor

Core Design Contradiction:

Ease of operationVSDifficulty of detecting and measuring

Solution Approach 1:

The rotor catch assembly performs preliminary action by automatically engaging the rotor shaft before any retrieval operation is needed. The catch members are pre-positioned to engage with the rotor shaft, and the assembly automatically activates upon detecting rotor separation, eliminating the need for operators to manually latch onto the difficult-to-grasp helically fluted and hard-chrome coated rotor surface.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The rotor catch assembly serves as an intermediary device between the rotor and the workstring. Instead of directly interacting with the difficult-to-grasp rotor surface, the catch members provide an intermediate engagement mechanism that simplifies the retrieval process by latching onto the rotor shaft through the catch assembly structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the downhole motor assembly separates into bearing assembly and power section, then mechanical failure or threaded connection issues occur, but this leads to costly and time-consuming fishing operations

Engineering Contradiction:

ImproveThreaded connection reliabilityVSAvoidRetrieval time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The rotor catch assembly implements preliminary anti-action by providing a preventive mechanism that activates automatically upon detecting rotor separation. The catch members are pre-positioned to engage the rotor shaft, and the assembly automatically deploys to prevent complete loss of the rotor, counteracting the harmful effect of separation before it leads to expensive fishing operations.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The rotor catch assembly provides beforehand cushioning by having catch members ready in advance to engage the rotor shaft upon separation. This pre-positioned safety mechanism cushions against the harmful effect of rotor loss, ensuring that even if separation occurs, the rotor remains secured and can be retrieved without costly fishing operations.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Strength

If the rotor shaft is made helically fluted and hard-chrome coated, then durability and wear resistance are improved, but conventional fishing tools become ineffective at latching onto it

Engineering Contradiction:

ImproveWear resistanceVSAvoidEase of latching

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

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

The rotor catch assembly effectively prevents the downhole motor assembly from being left in the wellbore, reducing the need for expensive fishing operations and enabling easier retrieval by generating pressure pulses to reduce friction and facilitate advancement of the workstring during operations.

Implementation Method 1

Rotation of the rotor shaft varies the size of the variable size flow port, thereby generating pressure pulses in the flow of the fluid upstream of the downhole motor assembly

Methodology Applied

Scientific EffectPressure pulses:

Implementation Method 2

The rotor shaft is axially moveable in the throughbore from an operating position, in which the fluid drives the downhole motor assembly, to a catch-activated position, in which the rotor shaft substantially blocks flow of the fluid to the downhole motor assembly

Methodology Applied

Scientific EffectFluid flow blocking:

Data Source

PatentUS10465510B2Rotor catch apparatus for downhole motor and method of use

Publication Date: 2019.11.05 KLX ENERGY SERVICES LLC

AI summary

A rotor catch assembly for connection in a workstring in a wellbore is provided. The rotor catch assembly is connected to a downhole motor assembly that includes a rotor that is driven by a fluid. In the normal operating state of the rotor catch assembly, fluid flows through the catch assembly and causes the rotor to rotate. In this state, the catch assembly generates pressure pulses in the fluid in the workstring to facilitate advancement of the workstring in the wellbore. In the event of a failure of a mechanical connection in the motor assembly, the rotor catch assembly shifts to a catch-activated state in which the motor assembly is disabled.