BHA Tool Placement via Modal Analysis
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Solution Overview
Problem
High frequency torsional oscillations in bottomhole assemblies (BHAs) during drilling lead to premature failures of components, as existing methods fail to effectively mitigate these vibrations.
Innovation Solution
Performing modal analysis to determine natural eigenfrequencies and eigenmodes of torsional oscillations, selecting a predominant eigenfrequency, and conducting forced modal analysis to correlate torsional deflection amplitude with position, allowing for the optimal placement of tools within the drill tubular to reduce vibration qualification below the torsional deflection amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tools are disposed in conventional positions in the BHA, then the drilling operation can proceed, but high frequency torsional oscillations cause premature failures of BHA components
Solution Approach 1:
The patent performs modal analysis and forced modal analysis before finalizing the BHA configuration to predict torsional vibration characteristics. This preliminary action allows optimization of tool positions and drill tubular properties before actual drilling, preventing premature failures by ensuring tools are placed in positions with acceptable vibration levels.
Solution Approach 2:
The patent changes physical parameters of the drill tubular (such as wall thickness, material properties, or geometric characteristics) to modify the torsional stiffness and natural frequencies of the system. By adjusting these parameters, the system avoids resonant conditions that would amplify torsional oscillations, thereby reducing harmful vibrations and improving component reliability.
2Object-affected harmful factors
If modal analysis and forced modal analysis are performed to optimize tool positioning, then torsional vibrations are reduced, but the design process becomes more complex
Solution Approach 1:
The patent replaces physical trial-and-error testing with computational modal analysis. By using finite element models and numerical simulations to predict torsional vibration behavior, the system eliminates the need for repeated physical prototyping and testing, reducing overall design complexity despite the sophisticated analysis methods employed.
Solution Approach 2:
The patent creates a digital model (copy) of the drill tubular and BHA components to perform virtual modal analysis. This digital replica allows for multiple design iterations and optimization scenarios to be evaluated without physical constraints, enabling complex vibration analysis while streamlining the design process through computational rather than physical means.
Data Source
AI summary
A method for estimating a location for disposing a tool in a drill tubular having a drill bit includes performing a modal analysis of the drill tubular to determine natural eigenfrequencies and corresponding eigenmodes of torsional oscillations of the model and selecting a predominant natural eigenfrequency and corresponding eigenmode from the determined natural eigenfrequencies and corresponding eigenmodes. The method further includes performing a forced modal analysis of the drill tubular at the predominant eigenfrequency with a force or moment acting on the drill bit to provide a correlation between forced torsional deflection amplitude and position and estimating the position to be within a range of positions wherein a vibration qualification of the tool is greater or equal to the torsional deflection amplitude throughout the range.