Slotted Drill String Coupler for High-Frequency Torsional Isolation
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Solution Overview
Problem
Severe high frequency torsional oscillations (HFTO) in drill strings and bottom hole assemblies during drilling operations lead to reduced rate of penetration, reduced measurement quality, and increased fatigue and wear on downhole components, due to cutting forces and mass imbalances in drilling tools.
Innovation Solution
A vibration isolating coupler is introduced, comprising a first and second coupler portion connected by a vibration isolating portion with slots forming vibration isolating elements, allowing torsional rotation and reducing HFTO by modifying torsional dynamics and acting as a mechanical low-pass filter to isolate frequencies above a specific isolating frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid coupler is used to connect drill string components, then structural strength and rigidity are improved, but high frequency torsional oscillations are transmitted throughout the drill string causing wear and reduced measurement quality
Solution Approach 1:
The coupler incorporates a vibration isolating portion with slots that change the torsional stiffness parameter of the connection. The slots allow the coupler to have different mechanical properties: sufficient rigidity for structural strength but reduced torsional stiffness to isolate high frequency vibrations above 50 Hz, effectively filtering HFTO while maintaining connection integrity
Solution Approach 2:
The vibration isolating portion acts as an intermediary element between the first and second coupler portions. This intermediate component with its slot geometry serves as a mechanical filter that blocks the transmission of harmful HFTO while allowing the transfer of necessary drilling forces and torques
2Force
If the drill string is made more rigid to withstand drilling forces, then load bearing capacity is improved, but vibrations are amplified and transmitted to downhole tools
Solution Approach 1:
The coupler design changes the torsional stiffness parameter locally at the connection point while maintaining overall drill string rigidity. The slots create a frequency-dependent response that allows rigid force transmission for drilling loads while providing vibration isolation for frequencies above 50 Hz, effectively decoupling load bearing from vibration transmission
3Reliability
If vibration isolation elements are added to reduce HFTO, then measurement quality and component durability are improved, but device complexity increases
Solution Approach 1:
The coupler is segmented into distinct functional portions: a first coupler portion, a vibration isolating portion with slots, and a second coupler portion. This segmentation allows each portion to be optimized for its specific function while maintaining overall simplicity. The slot geometry itself acts as the vibration isolation mechanism without requiring additional separate components
Solution Approach 2:
The vibration isolation function is merged into the coupler structure itself rather than being a separate component. The slots are integrated directly into the coupler body, combining the connection function and vibration isolation function into a single unified element, thereby improving reliability without proportionally increasing 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
The vibration isolating coupler effectively reduces HFTO modes and associated torque loads, enhancing the reliability and quality of downhole measurements while minimizing wear on drilling components by isolating high-frequency vibrations, thus improving drilling efficiency and tool durability.
Implementation Method 1
isolating the torsional vibration from the second coupler portion by torsional oscillation of the vibration isolating portion
Implementation Method 2
The plurality of vibration isolating elements enabling torsional rotation of the first coupler portion relative to the second coupler portion
Data Source
AI summary
A vibration isolating coupler including a first coupler portion, a second coupler portion including an external surface and an internal surface portion, and a vibration isolating portion extending between the first coupler portion and the second coupler portion. The vibration isolating portion including a first solid annular portion and a second solid annular portion. The vibration isolating portion including a plurality of slots extending from the first solid annular portion toward the second solid annular portion forming a plurality of vibration isolating elements. Each of the plurality of vibration isolating elements is disconnected from adjacent ones of the plurality of vibration isolating elements by a corresponding one of the plurality of slots. The plurality of vibration isolating elements enabling torsional rotation of the first coupler portion relative to the second coupler portion.