Downhole Rotating Machine Lubrication With Magnetic Coupling
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Solution Overview
Problem
Downhole-type rotating machines, such as compressors and pumps, face challenges in maintaining lubrication efficiency at high speeds due to flooded bearing systems, leading to windage losses and reduced performance in well production systems.
Innovation Solution
A lubrication system that includes a pressure-sealed housing with a lubrication reservoir and magnetic coupling, where a topside pressure source provides lubrication to both the electric machine and fluid rotor, allowing for adjustable pressure and reduced leakage, and a speed reducer to optimize lubricant flow and bearing support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flooded bearing system is used in downhole rotating machines, then the bearings are lubricated and supported, but windage losses increase and operating speed is limited
Solution Approach 1:
The patent divides the bearing system into two separate lubrication circuits: a first lubrication circuit for the electric machine bearings (isolated from wellbore fluids) and a second lubrication circuit for the fluid rotor bearings (exposed to wellbore fluids). This segmentation allows each circuit to be optimized independently, enabling the electric machine side to operate at higher speeds with reduced windage losses while the fluid rotor side maintains reliable lubrication in the harsh downhole environment.
2Reliability
If the electric machine is isolated from wellbore fluids by a pressure-sealed housing, then the electric machine is protected from corrosion and damage, but lubrication delivery becomes more complex
Solution Approach 1:
The patent introduces a magnetic coupling as an intermediary mechanism that transfers rotational motion from the electric rotor to the fluid rotor without direct mechanical contact. This eliminates the need for shaft seals or other penetrating connections through the pressure-sealed housing, maintaining fluid isolation while enabling power transmission. The magnetic coupling acts as a non-contact mediator that resolves the contradiction between sealing integrity and rotational drive.
3Reliability
If a magnetic coupling is used to connect the fluid rotor and electric rotor, then the electric machine remains isolated from wellbore fluids, but the coupling complexity increases
Solution Approach 1:
The patent replaces traditional mechanical coupling mechanisms (such as shafts, gears, or belts that would require seals or direct contact with wellbore fluids) with a magnetic coupling system. This substitution uses magnetic fields to transmit torque without physical contact, eliminating the need for mechanical seals and maintaining complete fluid isolation. The magnetic coupling complexity is offset by the elimination of more complex sealing and mechanical transmission systems.
4Productivity
If high operating speeds are achieved in downhole rotating machines, then productivity increases, but lubrication efficiency decreases due to windage losses
Solution Approach 1:
The patent applies different lubrication strategies to different parts of the system based on their specific requirements. The first lubrication circuit uses a lubricant selected for high-speed operation with low viscosity to minimize windage losses in the electric machine bearings. The second lubrication circuit uses a lubricant selected for resistance to downhole conditions (temperature, pressure, contamination) in the fluid rotor bearings. This local optimization of lubricant properties allows high-speed operation while maintaining lubrication efficiency in each specific zone.
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 system enhances the reliability and performance of downhole-type rotating machines by enabling higher operating speeds, minimizing windage losses, and allowing for customization across various well conditions, including those producing liquid, gas, or both.
Implementation Method 1
A magnetic coupling couples the fluid rotor and a rotor of the electric machine to rotate in unison
Implementation Method 2
The electric machine enclosed within a housing isolates the electric machine from fluids within the wellbore
Implementation Method 3
The first lubrication circuit is configured to provide lubrication to a bearing within the electric machine
Data Source
AI summary
An electric machine is configured to be positioned within a wellbore. The electric machine enclosed within a housing isolates the electric machine from fluids within the wellbore. A first lubrication circuit includes a lubrication reservoir within the housing. The lubrication reservoir is fluidically connected to the electric machine. The first lubrication circuit is configured to provide lubrication to a bearing within the electric machine. A fluid rotor is configured to move or be moved by a fluid within the wellbore. A magnetic coupling couples the fluid rotor and a rotor of the electric machine to rotate in unison. A second lubrication circuit is configured to provide lubrication to a bearing supporting the fluid rotor.