Impact-Driven Downhole Motor Torque Management
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Solution Overview
Problem
Conventional downhole motors face premature failures and unfavorable drilling conditions due to high torque requirements for drilling through hard subsurface materials, leading to increased reactive torque loads and fatigue failures in drill string components.
Innovation Solution
The implementation of downhole motors that apply intermittent rotational and axial impacts to the bearing mandrel and drill bit, utilizing an impact adapter and drive mandrel with kinetic energy storage means, such as a helical spring, to reduce reactive torque loads and enhance drilling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional downhole motors use high torque power sections to drill through hard subsurface materials, then drilling effectiveness is improved, but reactive torque loads increase causing fatigue failures in drill string components
Solution Approach 1:
The patent applies periodic impact forces to the bearing mandrel through a cam mechanism that converts continuous rotational motion into intermittent axial impacts. This periodic action allows the drill bit to deliver high impact forces to break hard subsurface materials while the average torque on the drill string remains lower, reducing fatigue loads on drill string components.
Solution Approach 2:
The patent introduces dynamic elements including a movable drive mandrel that can shift axially within the housing, and a cam mechanism that transforms steady rotational motion into dynamic impact forces. This dynamic approach enables the system to deliver high peak forces for effective drilling while maintaining lower average torque, thereby improving both drilling effectiveness and reducing reactive torque loads on the drill string.
2Productivity
If conventional downhole motors apply continuous rotational force to the drill bit, then steady drilling progress is achieved, but excessive reactive torque causes premature failures in motor components
Solution Approach 1:
The cam mechanism converts continuous rotation into periodic impact forces applied to the bearing mandrel. This allows the drill bit to advance through hard formations with high impact forces while the motor operates at lower average torque, reducing stress on motor components and preventing premature failures.
Solution Approach 2:
The drive mandrel acts as an intermediary between the power section and the bearing mandrel. It receives continuous rotational force from the power section and transforms it into intermittent impact forces through axial movement controlled by the cam mechanism, thereby protecting the motor components from excessive reactive torque while maintaining drilling effectiveness.
3Reliability
If downhole motors use impact-driven mechanisms with kinetic energy storage, then reactive torque loads are reduced, but device complexity increases
Solution Approach 1:
The patent uses a cam mechanism and movable drive mandrel to create dynamic impact forces. These components, while adding some complexity, are mechanically simple and rely on well-understood principles of mechanics. The cam profile can be customized for different impact characteristics without changing the fundamental mechanism, providing flexibility without proportional increases in complexity.
Solution Approach 2:
The cam mechanism allows easy adjustment of impact parameters such as impact frequency, duration, and force magnitude by simply changing the cam profile geometry. This enables optimization of the impact-driven mechanism for different drilling conditions without requiring complex control systems or multiple components, thereby achieving reactive torque load reduction with manageable device complexity.
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 solution allows for effective drilling through hard subsurface materials using lower-torque power sections while minimizing reactive torque loads on the drill string, reducing the likelihood of premature failures and improving drilling efficiency and effectiveness.
Implementation Method 1
kinetic energy storage means associated with the drive mandrel and the cam assembly... rotation of the drive mandrel will cause axially-upward movement of the drive mandrel relative to the impact adapter and the housing, resulting in kinetic energy being stored in the kinetic energy storage means
Implementation Method 2
a cam apparatus associated with the drive mandrel... further rotation of the drive mandrel will cause axially-downward movement of the drive mandrel so as to release the kinetic energy stored in the kinetic energy storage means
Implementation Method 3
regular axial and rotational impacts to the bearing mandrel, so as to rotate the bearing mandrel and the drill bit relative to the drill string
Data Source
AI summary
A downhole motor has a bearing mandrel rotatably disposed within a housing, plus an impact adapter disposed above and connected to the bearing mandrel and rotatable therewith. The impact adapter has upwardly-projecting teeth engageable with downwardly-projecting teeth on a drive mandrel disposed above and coaxially aligned with the impact adapter. The drive mandrel is both rotatable and axially movable within the housing, and relative to the impact adapter. By means of a cam assembly and a helical spring (or other energy storage means) associated with the drive mandrel, rotation of the drive mandrel causes upward movement of the drive mandrel within the housing, thus compressing the spring. Further rotation causes instantaneous dropping of the drive mandrel, releasing energy stored in the spring, and causing the application of rotational and/or axial impacts to the bearing mandrel, and thus to a drill bit connected to the bearing mandrel.