Self-Aligning Bearing Assembly for Downhole Shaft Misalignment
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Solution Overview
Problem
Current drilling technologies for directional drilling, such as tilted drive subs and adjustable kickoff tools, face limitations in adjusting tilt angles without disassembly and suffer from high side loads and bearing wear due to misalignment, leading to reduced durability and increased maintenance costs.
Innovation Solution
A self-aligning bearing assembly with curved surfaces, including spheroid and cylindrical geometries, that adjusts its direction in response to applied forces during drilling, maintaining contact over a large surface area to reduce specific surface loading and accommodate misalignments, thereby reducing wear and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If traditional radial bearings are used in tilted drive subs, then the bearing assembly can support radial loads, but the misalignment between bearing axis and housing axis causes high side loads and bearing wear
Solution Approach 1:
The patent replaces traditional radial bearings with spherical bearings that have curved bearing surfaces. This curvature allows the bearing to self-align and accommodate misalignment between the drive shaft axis and housing axis, distributing loads more evenly across the bearing surface and reducing localized wear while maintaining radial load support capability.
2Adaptability or versatility
If bent subs or adjustable kickoff tools are used for directional drilling, then the tilt angle can be adjusted, but high side loads and bending moments are exerted on the drill bit and stabilizer due to large bit to bend distance
Solution Approach 1:
The spherical bearing assembly enables tilt angle adjustment through self-alignment while minimizing the bit to bend distance. The curved bearing surfaces allow the drive shaft to tilt relative to the housing without creating large bending moments, as the spherical geometry naturally accommodates angular deviations and reduces the lever arm for side loads.
3Length of moving object
If tilted drive sub with offset bearing components is used, then the bit to bend distance can be minimized, but the tilt angle cannot be changed without parts exchange and complete disassembly
Solution Approach 1:
The patent employs spherical bearings that provide dynamic adjustability of the tilt angle. The spherical geometry allows the bearing to adapt to different angular positions continuously, enabling the tilt angle to be changed without disassembly. The bearing can dynamically accommodate any tilt angle within its capacity, making the system versatile while maintaining minimal bit to bend distance.
4Ease of manufacture
If conventional bearings with flat surfaces are used, then the manufacturing is simpler, but the contact area is small leading to high specific surface loading and increased wear
Solution Approach 1:
The patent transitions from flat bearing surfaces to spherical bearing surfaces. This curvature increases the contact area between bearing elements, distributing loads over a larger surface area and reducing specific surface loading. While spherical bearings are slightly more complex to manufacture than flat bearings, the increased durability and reduced wear compensate for the additional manufacturing complexity.
Data Source
AI summary
An apparatus for use in a drill string configured for use in a subterranean formation includes a drive shaft coupled to a drill bit, the drill bit configured to continuously rotate and penetrate within the subterranean formation, a drill string housing that houses the drive shaft, the drive shaft continuously rotating within the drill string housing relative to the drill string housing, and a bearing assembly configured bear the drive shaft within the drill string housing, the bearing assembly comprising a first bearing surface having a first curvature.