Segmented PZT Bender Bar for Low-Frequency Acoustic Logging
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Solution Overview
Problem
Current bender bars face difficulties in producing high-quality logs for large hole and soft formation applications due to low frequency responses, which is a challenge in acoustic logging tools used in wireline logging and logging while drilling processes.
Innovation Solution
A bender bar design featuring multiple pairs of piezoelectric elements arranged symmetrically around an inert element, with controlled pulse driving to enhance low frequency response and suppress unwanted vibrations, allowing for improved acoustic radiation and signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bender bar design is used, then the device is simple and easy to manufacture, but the frequency response is poor especially at low frequencies
Solution Approach 1:
The piezoelectric element is divided into multiple independent segments along the longitudinal axis. Each segment can be independently driven with controlled pulse signals, allowing selective excitation of different vibration modes. This segmentation enables improved frequency response by activating specific segments to generate desired acoustic frequencies while suppressing unwanted modes.
Solution Approach 2:
The patent implements dynamic control of the bender bar by applying time-varying pulse signals to different piezoelectric segments. The pulse duration, amplitude, and timing are dynamically adjusted to optimize low-frequency response and suppress high-frequency vibrations. This dynamic actuation strategy transforms the static structure into a dynamically controllable system.
2Reliability
If multiple pairs of piezoelectric elements are used to enhance low frequency response, then the acoustic radiation is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The piezoelectric element is segmented into multiple independent sections that can be manufactured separately and then assembled. Each segment corresponds to a specific vibration mode, allowing modular manufacturing and assembly. This approach maintains ease of manufacture by using standard piezoelectric segments while achieving improved acoustic radiation through their coordinated operation.
Solution Approach 2:
Multiple piezoelectric segments are combined in a systematic arrangement along the bender bar. The segments work together synergistically, with each contributing to specific frequency ranges. This merging of multiple simple components achieves complex acoustic radiation characteristics without requiring a completely new complex structure.
3Measurement precision
If controlled pulse driving is applied to suppress unwanted vibrations, then the signal quality is improved, but the control system complexity increases
Solution Approach 1:
The patent employs periodic pulse signals with specific durations and intervals to excite the piezoelectric segments. By carefully selecting pulse frequencies and timing, unwanted vibrations are suppressed while desired acoustic signals are enhanced. This periodic actuation strategy improves signal quality through simple temporal modulation rather than complex continuous control.
Solution Approach 2:
The controlled pulse driving selectively activates specific piezoelectric segments for specific time intervals, skipping segments that would generate unwanted vibrations. This selective and transient activation strategy suppresses harmful vibrations while maintaining signal quality, avoiding the need for continuous complex control of all segments.
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 enhanced bender bar design achieves better frequency response and signal quality, enabling more accurate formation property measurements and reducing the need for multiple logging trips, thereby minimizing costs and increasing efficiency in drilling operations.
Implementation Method 1
at least two pairs of piezoelectric elements coupled to the inert element
Data Source
AI summary
A bender bar is presented. The bender bar includes at least two pairs of piezoelectric elements arranged on an inert element to adjust the response frequency of the bender bar. In some embodiments, the piezoelectric elements can be stacked on the inert element. In some embodiments, the piezoelectric elements are symmetrically arranged with respect to the bender bar such that a gap is formed between piezoelectric elements arranged on the inert element.