Linear Motor Pump Stator Segmentation for Downhole Leakage Control
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Solution Overview
Problem
Existing linear motors for downhole pumps face challenges in achieving commercially viable fluid production levels due to insufficient pressure, requiring artificial lift devices and complex motor-pump assemblies that are costly and inefficient in fluid lifting.
Innovation Solution
A linear actuator system comprising a stator with modular pole sections and coils, a shaft with permanent magnets, and a pressure compensator, which generates a magnetic field to reciprocate the piston linearly, enhancing fluid lifting efficiency and scalability while maintaining a sealed environment for motor oil to act as a hydrodynamic bearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a linear magnetic motor is used to reciprocate the pump piston, then fluid lifting capability is improved, but pressure differentials cause leakage and contamination risks
Solution Approach 1:
The motor is divided into two separate chambers: a first chamber containing the stator and a second chamber containing the shaft with permanent magnets. These chambers are isolated from each other by a common seal that also seals the motor oil within the second chamber. This segmentation prevents contamination between the electromagnetic components and the fluid handling components while maintaining the pressure differential needed for fluid lifting.
Solution Approach 2:
Motor oil is introduced as an intermediary substance within the second chamber, surrounding the shaft and permanent magnets. The motor oil acts as both a lubricant for the moving parts and a barrier that prevents direct contact between the sealed electromagnetic environment and the external fluid environment, thereby reducing leakage and contamination risks while enabling the pressure differential required for pumping.
2Loss of energy
If motor oil is used as hydrodynamic bearing, then friction is reduced, but sealing the motor oil becomes challenging under pressure differentials
Solution Approach 1:
The seal serves multiple functions simultaneously: it seals the motor oil within the second chamber, separates the first and second chambers, and provides structural support for the permanent magnets. This merging of functions reduces the number of separate sealing components needed while maintaining effective sealing under pressure differentials, thus reducing friction without proportionally increasing device complexity.
Solution Approach 2:
The common seal is designed as a multi-functional component that performs sealing, structural support, and chamber separation functions. This universal component approach simplifies the overall sealing system compared to using multiple dedicated sealing elements, making the hydrodynamic bearing system more practical while maintaining low friction operation.
3Force
If permanent magnets are placed on the shaft, then magnetic field strength is improved, but susceptibility to demagnetization from heat and stress increases
Solution Approach 1:
The permanent magnets are extracted from the external environment and placed within the sealed second chamber, surrounded by motor oil. This isolation removes them from exposure to external heat sources, contaminants, and mechanical stresses that could cause demagnetization. The motor oil provides thermal management and protective cushioning, allowing the magnets to generate strong magnetic fields while maintaining reliability.
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 system improves fluid lifting efficiency by scalable force output and reduced pressure differentials, minimizing leakage and contamination risks, thus enhancing the overall performance and reliability of downhole pumps.
Implementation Method 1
The stator generates a magnetic field through a series of annular magnetic coils. By timing the flow of current in the coils with respect to the position and/or momentum of the shaft, the interaction of magnetic forces from the shaft and from the stator will actuate the shaft to move linearly either up or down.
Implementation Method 2
The shaft generates a magnetic field by virtue of having a series of built in permanent magnets. The interaction of magnetic forces from the shaft and from the stator will actuate the shaft to move linearly either up or down.
Implementation Method 3
maintaining a sealed environment for motor oil to act as a hydrodynamic bearing
Data Source
AI summary
A linear actuator for pumping comprising a stator having an inner opening, a shaft having a plurality of permanent magnets spaced linearly in the axial direction, the shaft disposed in the stator opening and configured to reciprocate linearly in the axial direction relative to the stator, the stator comprising a first stator assembly having a plurality of pole sections spaced linearly in the axial direction and a plurality of coils disposed therebetween, a second stator assembly having a plurality of pole sections spaced linearly in the axial direction and a plurality of coils disposed therebetween, a bearing assembly positioned axially between the first stator assembly and the second stator assembly, and the bearing assembly having a width that is a function of the spacing of the plurality of pole sections of the first stator assembly and the second assembly and the spacing of the plurality of permanent magnets of the shaft.