Tilt Drive Shaft Eccentric Assemblies for Directional Drilling
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Solution Overview
Problem
Existing directional drilling systems face challenges in efficiently altering the azimuthal tool face orientation of drill bits due to mechanical stresses and complexity, which limits their ability to achieve high dogleg capabilities and increases costs.
Innovation Solution
The use of a tilt drive shaft with axially offset upper and lower eccentric assemblies, allowing for tilting rather than bending, reduces mechanical stresses and enables a higher bit-to-bend angle, thereby enhancing dogleg capability and reducing the need for robust components and maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a bent motor housing is used for directional drilling, then the drill bit can be oriented at a deviated angle, but the mechanical stresses on the bent housing increase and the system complexity increases
Solution Approach 1:
Instead of bending the motor housing to achieve the deviated angle, the patent inverts the approach by keeping the motor housing straight and using a tilted drive shaft that can be rotated relative to the housing. This allows the drill bit to be oriented at deviated angles while the motor housing itself experiences no bending stresses, thereby resolving the contradiction between adaptability and strength.
Solution Approach 2:
The patent introduces a dynamically tiltable drive shaft that can change its angle relative to the motor housing during operation. This dynamic adjustment capability allows the system to achieve various deviated angles without permanently deforming the motor housing, maintaining structural integrity while providing directional control.
2Adaptability or versatility
If a bent motor housing is used to achieve deviated drilling, then directional control is possible, but the device complexity and number of parts increase
Solution Approach 1:
The patent simplifies the system by inverting the conventional approach: instead of a complex bent housing structure, it uses a straight housing with a tiltable drive shaft. This reduces the structural complexity of the housing while maintaining directional control capability through the simpler, modular tilt mechanism.
Solution Approach 2:
The patent segments the directional control function into a separate tiltable drive shaft mechanism independent of the motor housing. This segmentation allows the housing to remain simple and straightforward while the tilt mechanism provides the necessary directional control, reducing overall system complexity.
3Reliability
If robust components are used to handle mechanical stresses in directional drilling, then reliability improves, but costs increase due to more parts and inventory
Solution Approach 1:
By inverting the design approach to use a straight motor housing with a tiltable drive shaft, the patent eliminates the need for robust bent housing components. The tilt mechanism uses simpler, less stressed components that are easier to manufacture and maintain, reducing part count and inventory requirements while maintaining reliability through reduced stress on critical components.
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 approach allows for increased dogleg capability, reduced mechanical stress, lower costs due to fewer parts and reduced inventory, and simplified maintenance, while maintaining precise control over the drill bit's azimuthal orientation.
Implementation Method 1
an upper eccentric assembly arranged within the housing and configured to support the tilt drive shaft at or near the first end, the upper eccentric assembly including an upper inner eccentric ring nested within an upper outer eccentric ring and rotatable with respect to each other, and a lower eccentric assembly arranged within the housing and configured to support the tilt drive shaft at or near the second end
Data Source
AI summary
A directional drilling sub comprises a housing, a coupling mechanism arranged within the housing, and a tilt drive shaft extending within the housing and has a first end coupled to the coupling mechanism and a second end coupled to a drill bit. The sub further comprises an upper eccentric assembly arranged within the housing to support the tilt drive shaft at the first end which includes an upper inner eccentric ring nested within an upper outer eccentric ring and a lower eccentric assembly arranged within the housing to support the tilt drive shaft at the second end which includes a lower inner eccentric ring nested within a lower outer eccentric ring, wherein rotational movement of at least one of the upper and lower inner or outer eccentric rings tilts the tilt drive shaft within the housing and thereby alters an azimuthal tool face orientation of the drill bit.