Adjustable Bend Assembly for Downhole Motor Deflection Control
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Solution Overview
Problem
Downhole motors in directional drilling experience bending moments and associated stresses due to the bit-to-bend distance, which can lead to damage and limit the maximum deflection angle, reducing the durability and efficiency of drilling operations.
Innovation Solution
An adjustable bend assembly in the downhole motor reduces the bit-to-bend distance by allowing the deflection angle to be adjusted between 0° and 180°, using a universal joint and an adjustment mandrel to minimize bending moments and stresses, and eliminating the threaded connection susceptible to failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bit-to-bend distance is reduced to decrease bending moments and stresses, then the durability and reliability of the downhole motor is improved, but the device complexity increases due to the adjustable bend assembly with universal joint and adjustment mandrel
Solution Approach 1:
The adjustable bend assembly is segmented into distinct functional components: a universal joint mechanism for angular adjustment, an adjustment mandrel for setting the deflection angle, and a threaded connection system for securing the configuration. This segmentation allows each component to perform its specific function independently, making the complex system more manageable and maintainable while achieving the goal of reducing bit-to-bend distance to improve reliability
Solution Approach 2:
The bend assembly transitions from a fixed configuration to a dynamic, adjustable configuration. The universal joint and adjustment mandrel enable the deflection angle to be modified during operations, allowing the system to adapt to different drilling conditions and optimize the bit-to-bend distance for improved reliability without being locked into a single complex design
2Stress or pressure
If the deflection angle is adjusted to a smaller value to reduce bending moments, then the stress on the motor is reduced, but the ability to achieve desired borehole curvatures is limited
Solution Approach 1:
The adjustable bend assembly enables dynamic modification of the deflection angle, allowing operators to optimize between stress reduction and curvature achievement. By adjusting the universal joint and mandrel position, the system can adapt the deflection angle to match specific borehole requirements while maintaining stress within acceptable limits, thus resolving the contradiction between stress reduction and adaptability
Solution Approach 2:
The system changes the deflection angle parameter to optimize performance. The adjustment mandrel allows continuous or discrete modification of the bend angle, enabling the system to find the optimal parameter value that balances stress reduction with the ability to achieve desired borehole curvatures for different drilling scenarios
3Reliability
If threaded connections are eliminated to prevent connection failure, then the reliability is improved, but the ease of assembly and disassembly is reduced
Solution Approach 1:
The universal joint acts as an intermediary mechanism that eliminates the need for traditional threaded connections between the bend assembly components. Instead of relying on threaded fasteners that are susceptible to failure, the universal joint provides a robust mechanical connection that accommodates angular movements while maintaining structural integrity, thus improving reliability without significantly complicating assembly through its standardized design
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 reduced bit-to-bend distance decreases bending moments and stresses, enhancing the durability and build rates of the downhole motor, allowing for a smaller deflection angle to achieve desired borehole curvatures and reducing the risk of motor failure.
Implementation Method 1
using a universal joint and an adjustment mandrel to minimize bending moments and stresses
Data Source
Figure 1
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AI summary
A downhole motor for directional drilling includes a driveshaft assembly including a driveshaft housing and a driveshaft rotatably disposed within the driveshaft housing. In addition, the downhole motor includes a bearing assembly including a bearing housing and a bearing mandrel rotatably disposed within the bearing housing. The bearing mandrel has a first end directly connected to the driveshaft with a universal joint and a second end coupled to a drill bit. Further, the downhole motor includes an adjustment mandrel configured to adjust an acute deflection angle θ between the central axis of the bearing housing and the central axis of the driveshaft housing. The adjustment mandrel has a central axis coaxially aligned with the bearing housing, a first end coupled to the driveshaft housing, and a second end coupled to the bearing housing.