Downhole Motor Axial Load Decoupling
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Solution Overview
Problem
Conventional downhole motor designs with bearings located distally result in a long distance between the drive connection and the drill bit, leading to premature failure, reduced stiffness for directional drilling, and inefficiencies in non-directional drilling due to increased side loads and bending moments.
Innovation Solution
The downhole motor assembly features bearings located proximal to the power section, with axial loads decoupled to separate and apportion them among multiple bearings, reducing the overall length and size of the bearing components, and incorporating an axial load decoupling device to facilitate torque transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bearings are located distally in conventional downhole motor designs, then the bearing section can transfer forces between the housing and drive train, but the distance between the drive connection and drill bit becomes excessively long
Solution Approach 1:
The patent inverts the conventional bearing location from distal to proximal of the power section. This inversion allows the bearing section to be positioned closer to the drive connection, significantly reducing the distance between the drive connection and drill bit while still maintaining force transfer capability between the housing and drive train.
Solution Approach 2:
The patent segments the axial loads into two separate bearing assemblies: a first thrust bearing assembly for off-bottom axial loads and a second thrust bearing assembly for on-bottom axial loads. This segmentation allows each bearing assembly to be optimized for specific load conditions and positioned to minimize the overall distance from drive connection to drill bit.
2Device complexity
If the distance between drive connection and drill bit is long, then the bearing section can accommodate all necessary bearings, but the drive train experiences increased torque and torsion effects leading to earlier failure
Solution Approach 1:
By inverting the bearing location from distal to proximal, the patent reduces the length of the drive train between the power section and drill bit. This reduction minimizes the exposure of the drive train to torque and torsion effects, thereby preventing earlier failure while maintaining the necessary bearing configuration complexity.
3Adaptability or versatility
If the distance from drive connection to drill bit is long in bent downhole motors, then the motor can be used for directional drilling, but the bend to bit distance becomes too long reducing stiffness and build angle capability
Solution Approach 1:
The patent inverts the bearing location to reduce the overall length from drive connection to drill bit. In bent downhole motors, this reduction directly decreases the bend to bit distance, thereby increasing bend stiffness and improving build angle capability while preserving directional drilling adaptability.
4Device complexity
If all axial loads are transferred to a single distal thrust bearing, then the bearing section can be simplified, but the bearing must accommodate both on-bottom and off-bottom loads increasing its size and position requirements
Solution Approach 1:
The patent segments the axial load capacity into two separate thrust bearing assemblies: the first thrust bearing assembly handles off-bottom axial loads and the second thrust bearing assembly handles on-bottom axial loads. This segmentation allows each bearing assembly to be smaller and more specialized, reducing the overall complexity of the bearing section structure while maintaining comprehensive axial load capacity.
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 configuration reduces the distance between the drive connection and the drill bit, enhancing motor durability, stiffness for directional drilling, and efficiency in non-directional drilling by distributing loads effectively and reducing side loads and bending moments.
Implementation Method 1
an axial load decoupling device in the distal drive assembly located longitudinally between the distal rotor end and the distal thrust bearing, for separating axial loads imposed on the proximal thrust bearing from axial loads imposed on the distal thrust bearing
Implementation Method 2
a proximal thrust bearing arranged between the housing and the proximal drive assembly, for transferring axial loads between the housing and the proximal drive assembly; a distal thrust bearing arranged between the housing and the distal drive assembly, for transferring axial loads between the housing and the distal drive assembly
Implementation Method 3
Drilling fluid is passed through the power section of the downhole motor in order to convert fluid energy into rotational energy of the rotor within the stator
Data Source
AI summary
A downhole motor assembly which has a housing, a power section with a stator and a rotor contained within the housing. A proximal drive assembly is connected with a proximal rotor end, a distal drive assembly is connected with a distal rotor end, and a proximal thrust bearing is arranged between the housing of the proximal drive assembly. A distal thrust bearing is arranged between the housing and the distal drive assembly. An axial load decoupling device is in the distal drive assembly located longitudinally between the distal rotor end and the distal thrust bearing, and is used for separating axial loads imposed on the proximal thrust bearing from axial loads imposed on the distal thrust bearing.