Variable Stiffness Rotor for Progressive Cavity Motor Durability
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Solution Overview
Problem
Moineau pumps and motors used in directional drilling experience motor failure due to excessive lateral and shear forces on the rubber or elastomer components, leading to inefficiencies and reduced durability.
Innovation Solution
The design incorporates a rotor with a variable diameter and stiffness along its axial length, and a stator with a corresponding variable inner diameter, which reduces shear stress on the elastomer and enhances sealing efficiency, allowing for optimal bending and power transmission while minimizing side loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rotor with variable diameter and stiffness is used, then durability and efficiency are improved, but device complexity increases
Solution Approach 1:
The rotor is designed with variable diameter along its axial length, creating different local stiffness characteristics. The uphole portion has a smaller diameter while the downhole portion has a larger diameter, allowing each section to have optimized mechanical properties for its specific operational requirements, thereby improving overall durability without requiring a complete redesign of the entire rotor structure.
Solution Approach 2:
The rotor incorporates variable stiffness along its axial length, making it a dynamically optimized component rather than a uniform structure. This dynamic design allows the rotor to flex and bend differently at various sections, accommodating the varying mechanical loads and stresses experienced during motor operation, which improves reliability while maintaining a manageable structural complexity.
2Force
If rotor diameter is reduced at the uphole end, then side loads are minimized, but manufacturing precision requirements increase
Solution Approach 1:
The rotor features a locally optimized diameter profile where the uphole end has a reduced diameter compared to the downhole end. This local variation in geometry is designed to specifically address side load reduction at the uphole section while maintaining adequate stiffness where needed, balancing force optimization with manufacturing feasibility.
Solution Approach 2:
The rotor diameter parameter is deliberately varied along the axial length rather than maintaining a constant diameter. This parameter change creates a gradient in stiffness and load distribution, minimizing side loads at the uphole end while the gradual transition in diameter helps manage manufacturing precision requirements through controlled geometric variation.
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 design increases the durability and efficiency of Moineau motors by reducing motor failure rates and maintaining torsional force, thereby prolonging the motor's lifespan and improving directional drilling performance.
Implementation Method 1
The rotor has a variable diameter and stiffness along an axial length of the rotor, which reduces shear stress on the elastomer
Implementation Method 2
A mud motor converts some of the energy from the flow of drilling fluid or mud downward through the bore of the drill string into a rotational motion that drives the drill bit
Data Source
AI summary
Rotor and/or stator designs and methods thereof to improve progressive cavity motor or pump durability. In one or more implementations, the rotor may have a variable outer diameter or variable stiffness along an axial length thereof. The stator may similarly have a variable inner diameter or variable stiffness, which may compliment or diverge from the variable outer diameter or variable stiffness of the rotor.