Drill String Resonance Avoidance via Modal Analysis
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Solution Overview
Problem
Severe vibrations in drill strings and bottomhole assemblies during borehole drilling lead to reduced rate of penetration, measurement quality, and equipment failures, necessitating improvements in drill string operations to mitigate these issues.
Innovation Solution
A method and apparatus that vary the frequency of excitation forces applied to the drill string using an excitation device controlled by a drill string controller, measure vibration amplitudes with sensors, determine eigenfrequencies, and select drilling parameters to avoid resonance frequencies, thereby reducing severe vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If drilling parameters are selected without considering eigenfrequencies, then drilling operations can proceed without frequency analysis complexity, but severe vibrations occur due to resonance causing reduced rate of penetration and equipment failures
Solution Approach 1:
The system performs preliminary modal analysis to identify eigenfrequencies of the drill string before drilling operations begin. By determining the modal properties (eigenfrequencies and mode shapes) in advance, the system can pre-select drilling parameters that avoid resonance conditions, thereby preventing severe vibrations before they occur during actual drilling operations
Solution Approach 2:
The system uses vibration sensors to measure actual vibrations during drilling operations and feeds this information back to the parameter selection process. This feedback mechanism allows the system to adjust drilling parameters in real-time based on observed vibrational responses, ensuring operation away from resonant frequencies and maintaining optimal drilling performance
2Reliability
If drilling operations continue without vibration mitigation, then operational continuity is maintained, but equipment failures occur due to severe vibrations
Solution Approach 1:
The system determines modal properties and selects safe drilling parameters before operations begin, establishing a foundation for reliable drilling without encountering resonance-induced equipment failures. This preliminary configuration ensures that the drill string operates in safe frequency ranges throughout the drilling process
Solution Approach 2:
Vibration sensors continuously monitor drilling operations and provide feedback to the parameter selection system. When vibrations approach dangerous levels, the system automatically adjusts parameters to move away from resonant frequencies, preventing equipment failures and maintaining operational reliability without requiring manual intervention
3Object-affected harmful factors
If modal analysis is performed to identify eigenfrequencies, then resonance-induced vibrations can be avoided, but measurement and analysis complexity increases
Solution Approach 1:
The system intentionally applies mechanical vibrations to the drill string using excitation forces generated during normal drilling operations. By analyzing the vibrational response at different frequencies, the system identifies eigenfrequencies and mode shapes through modal analysis, converting the harmful vibration phenomenon into a useful diagnostic tool for determining safe operating parameters
Solution Approach 2:
Vibration sensors measure the drill string's response to excitation forces, and this measurement data is fed back to the analysis system. The system processes these measurements to identify modal properties, using the feedback loop to iteratively refine the understanding of the drill string's vibrational characteristics and determine safe operating frequencies
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 effectively reduces vibrations, improving the rate of penetration and reducing the risk of equipment damage, allowing for more efficient and cost-effective borehole drilling by avoiding resonance-induced vibrations.
Implementation Method 1
severe vibrations in drill strings and associated bottomhole assemblies can be caused by cutting forces at the bit or mass imbalances in downhole tools such as mud motors. Vibrations can be differentiated into axial, torsional and lateral direction. Negative effects due to the severe vibrations are among others reduced rate of penetration, reduced quality of measurements and downhole failures
Data Source
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AI summary
A method for selecting drilling parameters for drilling a borehole penetrating the earth with a drill string includes: varying a frequency of an excitation force applied to the drill string using an excitation device controlled by a drill string controller and measuring vibration-related amplitudes of the drill string due to the applied excitation force using a vibration sensor to provide amplitude measurements. The method further includes determining one or more modal properties comprising one or more eigenfrequencies of the drill string using the amplitude measurements and selecting drilling parameters that apply an excitation force at a frequency that avoids a selected range of frequencies that bound the one or more eigenfrequencies.