Composite Vibration Index for Drilling Assembly Dynamics
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Solution Overview
Problem
Current drilling vibration modeling techniques fail to effectively combine different excitation frequencies, leading to increased complexity in design processes and a lack of quantitative understanding of harmonic content, which hinders efficient drilling operations and tool durability.
Innovation Solution
A method to develop a composite vibration index (CVI) by applying weights to vibration indices based on spectral content from recorded drilling data, allowing for a more representative and quantitative interpretation of drilling dynamics, thereby improving design criteria and operational guidance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If frequency-domain models are used to model drilling vibrations, then computational efficiency is improved, but the ability to combine different excitation frequencies and represent harmonic content is insufficient
Solution Approach 1:
The patent segments the vibration analysis by separating different excitation frequencies and their corresponding harmonics. Frequency-domain models are used for each frequency component individually, allowing efficient computation while maintaining the ability to analyze each harmonic separately. This segmentation enables the model to handle multiple frequencies without computational overload while preserving detailed harmonic information.
Solution Approach 2:
The patent introduces spectral analysis as an intermediary tool that bridges frequency-domain modeling and time-domain characteristics. By using spectral analysis, the model can process frequency-domain data while capturing time-varying harmonic content. This intermediary approach allows the system to maintain computational efficiency of frequency-domain methods while gaining the ability to represent complex harmonic structures.
2Measurement precision
If multiple vibration indices for different excitation frequencies are calculated separately, then frequency-specific analysis precision is improved, but design process complexity increases
Solution Approach 1:
The patent merges multiple frequency-specific vibration indices into a unified composite vibration index. By combining the results from different excitation frequencies and their harmonics into a single composite metric, the model maintains precise frequency-specific analysis while simplifying the design process. This merging allows engineers to work with one comprehensive index rather than managing multiple separate indices, reducing design complexity without sacrificing analytical precision.
3Loss of information
If time-domain modeling is used to combine vibration components, then comprehensive vibration representation is improved, but computational intensity increases
Solution Approach 1:
The patent employs periodic action by utilizing the periodic nature of drilling vibrations at different frequencies. Instead of performing continuous time-domain simulations which are computationally intensive, the model exploits the periodic characteristics of vibration components at various frequencies. This allows the system to represent comprehensive vibration behavior by analyzing discrete periodic cycles at each frequency, significantly reducing computational intensity while maintaining accurate vibration component combination.
Data Source
AI summary
A method to drill a borehole or wellbore through an earthen formation using a drill bit on a drillstring, comprising the steps of: selecting a frequency-domain dynamic model of a drilling assembly that describes the dynamic response of the drilling assembly to excitation at an excitation frequency for operating at a set of selected drilling parameters that include at least rotary speed and weight on bit; calculating a composite vibration index by combining calculated vibration indices for each excitation frequency with the spectral weighting factors for each of the drilling parameter partitions; displaying said composite vibration index for each of the drilling parameter partitions; selecting preferred drilling parameters based on the displayed results, and using the preferred drilling parameters to drill a borehole with the modeled drilling assembly.