Progressing Cavity Power Section Non-Uniform Interference Fit

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Solution Overview

Problem

Progressing cavity motors and pumps face issues with heat distribution and thermal expansion, leading to material degradation and premature failure due to uneven pressure loading across stages, especially in the bottom stages where most work is performed during drilling or circulation.

Innovation Solution

A progressing cavity device with a non-uniform interference fit between the stator and rotor, where the fit is tighter at the uphole end and looser at the downhole end, evenly distributes torque and heat across all stages, maintaining better material properties and extending the life of the power section.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a uniform interference fit is used throughout the power section, then the stator provides consistent engagement along the length, but the pressure load is not carried evenly across stages causing heat buildup in bottom stages

Engineering Contradiction:

Improveuniform interference fitVSAvoidheat distribution

Core Design Contradiction:

Stability of the object's compositionVSTemperature

Solution Approach 1:

The stator is designed with varying interference fit characteristics at different axial positions. The bottom portion has a first interference fit value that is higher than the top portion's second interference fit value, creating non-uniform engagement to balance pressure load distribution across stages and reduce heat concentration in the bottom stages.

Inventive Principle:

Principle #3Local quality

2Power

If the bottom stages perform most of the work during drilling, then torque generation is maximized, but heat is generated causing thermal expansion and increased interference leading to material degradation

Engineering Contradiction:

Improvetorque generationVSAvoidmaterial durability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The interference fit is deliberately made higher at the bottom portion of the stator where torque generation occurs, which balances the pressure load across stages and distributes heat more evenly, preventing excessive thermal expansion and material degradation while maintaining effective torque generation.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The interference fit parameter is varied along the axial length of the stator, with the bottom portion having a higher interference fit value than the top portion. This parameter change optimizes both torque generation and heat distribution to prevent material degradation.

Inventive Principle:

Principle #35Parameter changes

3Temperature

If a contoured steel stator with thin elastomer coating is used, then heat transfer distribution is improved, but the elastomer thickness is reduced limiting the ability to manage solids in the fluid

Engineering Contradiction:

Improveheat transfer distributionVSAvoidsolid handling capability

Core Design Contradiction:

TemperatureVSAdaptability or versatility

Solution Approach 1:

Instead of using a contoured steel stator with thin elastomer coating, the invention uses a uniform steel stator with varying interference fit values along the axial length. This approach achieves heat distribution improvement while maintaining sufficient elastomer thickness to effectively manage solids in the fluid.

Inventive Principle:

Principle #3Local quality

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 solution effectively reduces heat-related damage and extends the operational life of the power section by evenly loading pressure and torque across all stages, enhancing the efficiency and reliability of the device.

Implementation Method 1

The stator lining has a non-uniform interference fit with the rotor, where the fit is tighter at the uphole end and looser at the downhole end

Methodology Applied

Scientific EffectInterference fit:

Implementation Method 2

The generated heat causes the elastomer of the stator to thermally expand and increases the interference with the rotor

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 3

The rotor defines a plurality of sealed stage cavities with the stator lining. In response to the pumped drilling fluid progressing in the sealed stage cavities from the uphole end to the downhole end, the rotor is torqued

Methodology Applied

Scientific EffectPositive displacement:

Implementation Method 4

The stator is an elastomer that flexibly engages the metal rotor with a tight interference so a seal is formed, leakage between stages can be minimized

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS11519381B2Load balanced power section of progressing cavity device

Publication Date: 2022.12.06 WEATHERFORD TECHNOLOGY HOLDINGS LLC

AI summary

A progressing cavity device operates as a motor to impart torque to a bit. A stator of the device defines an internal profile having uphole stages with a first dimension being less than a second dimension of downhole stage. A rotor has an external profile with a constant outer dimension along its length. Disposed in the stator, the rotor defines cavities with the stator and is rotatable with pumped fluid progressing in the cavities from the uphole to downhole to transfer torque to the drive toward the downhole end. Although the rotor is subjected at the downhole end to a reactive torque from the bit, the interference fit of the rotor's constant dimension with the stator's downhole stages is less than with the uphole stages, which can mitigate issues with heat buildup in the downhole stages. The device can also operates as a progressing cavity pump.